· non-operation and plcc mal- operation. the trippings due to gds, gis, auto-reclosure failure/...

Minutes of the 49th

PCSC Meeting held on 30-11-2015 Page 1

SOUTHERN REGIONAL POWER COMMITTEE BENGALURU

Minutes of the 49th Meeting of Protection Coordination Sub-Committee

(PCSC – 49) of SRPC held on 30.11.2015

1. Introduction The 49th meeting of Protection Coordination Sub-Committee (PCSC-49) was held on 30th November, 2015 in Mangalore, Karnataka. The list of participants is enclosed at Annexure-I.

Sh. R.C. Bhat, Station Head, UPCL extended warm welcome to Sh. S.R. Bhat, Member Secretary (MS), SRPC, Sh. P. Raghuram, Executive Director (ED), SRLDC, and other Officials from State & Private Power Utilities, SRLDC & SRPC. He thanked MS, SRPC for giving them the opportunity to host PCSC meeting, and added that ‘Team UPCL’ had put in all efforts to ensure a comfortable and enjoyable stay for all participating members. Then, a presentation was given by UPCL team highlighting the achievements and road-map of Adani Group with specific focus on Power Sector. Sh. S.R.Bhat, Member Secretary (MS), SRPC thanked Adani UPCL management for the excellent hospitality, and all the due care they have taken in making arrangements for the smooth conduct of the meeting. He then welcomed the Members and Participants to the meeting and briefed them on the following points:

Briefed the members on the proceedings of the third Grid Study Committee meeting held

on 18th November, 2015, wherein the Draft Report on Task-1 activities (Review of

implementation of Enquiry Committee recommendations given consequent to Grid

Disturbance in July, 2012) prepared by the Consultant (M/s Tractebel Engg.) was

discussed. As the performance of the Southern Region according to the report was not

very satisfactory, it was high-time Constituents make concerted efforts to resolve/

complete long-pending issues from their respective sides. The draft report was also

circulated all SR-Constituents for comments, however PGCIL (SR-II), KPTCL and KSEB only

responded.

Informed the members that the Task-2 data (relating to 15 Stations identified from SR for

audit-check by the Consultant) furnished by the respective Constituents had been

forwarded to the Consultant through NLDC for scrutiny and analysis, and the actual audit

of the Stations would commence shortly. In this regard, a meeting was also held (via VC)

with NLDC and the Consultant on 24th December, 2015 to discuss the modalities of

protection audit, wherein it was decided that the concerned Constituent-owner of the

Station would provide extracted relay settings (in pdf. format), if not already given to the

Consultant, and the Consultant would in turn provide their recommended relay settings

(based on the data already made available to them for each of the 15 stations) to the

concerned Constituent-owner of the Station well before the actual protection audit is

Minutes of the 49th


undertaken for that particular Station. It was reasoned that by doing so, not only do the

concerned Constituent/ Station personnel get an opportunity to peruse the to-be-revised

settings, and prepare themselves for the protection audit, but it would also facilitate in

finalizing the settings during actual protection audit. To start with, NLC TPS-II of NLC

(Audit schedule: 4th , 5th & 7th December, 2015) and Alamathy S/S of TANTRANSCO (Audit

schedule: 9th , 10th & 11th December, 2015) would be audited in the first round and the

schedule for the other Stations would be intimated soon. He requested Constituents’

active cooperation in completing Task-2 activities to the satisfaction of all parties involved.

Informed the members that the issue of implementation of Power-Swing protection

philosophy as recommended by the Rama Krishna Committee would be discussed in the

forthcoming meeting of National Power Committee (NPC), and requested to present their

views when the issue is taken up for discussion later in the meeting.

Reminded members of nearing dead-lines of time-extensions given to SR-Constituents by

Hon’ble CERC for completion of their respective Protection Audit Remarks (PAR). KPCL,

KPTCL, TSTRANSCO were requested to approach CERC for extension of time-lines with

proper facts.

In this regard, KPTCL representative informed that their R&U proposal was approved

during Appraisal Committee meeting held on 17.11.2015 and sent to CERC for further

processing of the scheme as per PSDF disbursement procedure. Early sanctioning of PSDF

grants from Monitoring Committee was awaited and thereafter LOI would be issued to the

successful bidder M/s Alstom. The execution time finalized for completion of

works related to 93 substations is 15 months from the date of award, since sub stations

are scattered throughout the state and many works require planned outages. 26 numbers

of audited substations are planned to take up in the first phase.

However, as CERC, after hearing the petition filed by KSEB, TamilNadu in its Order dated

18.08.2015, has reiterated the deadline for completion of the R&U project by KPTCL

as 15.01.2016 which was requested by KPTCL in the affidavit filed during September 2014

and has also confirmed that no request for further extension of time would be considered,

a decision has been taken at KPTCL management level to file a petition before CERC with

all facts requesting for extension of time for execution of the project.

Brought to members’ attention the obligation of fulfilling their requirements under

Regulation 5.2 (r) of IEGC, as per which all Users, STU/ SLDC, and CTU are required to

furnish for analysis purpose the relevant information relating to tripping events in their

system along with Disturbance Recorder (DR) and Event Logger (EL) to SRLDC/ SRPC within

24-hrs of occurrence of the same. Though this issue was regularly brought to Constituents’

attention vide various SRLDC & SRPC (fort-nightly) letters, still data w.r.t. all events was

either not being furnished or being made available with unacceptable delay of few weeks.

Constituents were urged to strictly comply with Regulation 5.2 (r) of IEGC, and furnish the

data in time.

Minutes of the 49th


Stressed upon the need to furnish remedial measures taken by the Constituents for the

forced outage of the transmission elements incident to their respective systems in time as

the same was also being monitored by the Office of Member (GO&D), CEA.

Finally requested members’ active participation in the ensuing discussions so as to raise

the quality standards to a new bar commensurate with the amazing ambience of

Mangalore city as orchestrated by Adani UPCL Team.

22. Confirmation of the Minutes of the 48th PCSC meeting held on 29.10.2015

SE (Protection), SRPC stated that the Minutes of the 48th meeting of the PCSC had been circulated vide SRPC letter No. SRPC/SE-III/ PCSC-48/ 2015/ 8412 - 44 dated 19.11.2015. As no comments had been received from any of the Constituents, the Minutes of the 48th meeting of PCSC were confirmed.

3. Details of Grid Disturbances (GD’s), Grid Incidents (GI’s), Line Trippings due to Auto-Reclose

non-operation and PLCC mal- operation. The trippings due to GD’s, GI’s, Auto-Reclosure failure/ non-operation, and PLCC mal-operation

that had occurred during the period October-November, 2015 were discussed in the Meeting. The deliberations and recommendations of the PCSC-forum are enclosed at Annexure–II. In the meeting ED,SRLDC informed that SRLDC would be approaching Hon’ble CERC for all the Grid Occurrences (GD’s and GI’s) which occurred due to abnormal delayed clearance.

4. Status of pending PCSC recommendations The status of implementation of pending PCSC recommendations was discussed in the meeting.

The Constituents had been requested to kindly submit the status of their compliance latest by 25-12-2015. The updated status of the same as on 14-12-2015 is enclosed at Annexure–III.

5. Remedial measures/ Action taken for the tripping incidents of the transmission elements

under forced outage The tripping incidents of the transmission elements under forced outage for which the remedial

measures/ actions taken still awaited were discussed in the meeting. The Constituents had regularly been kept apprised of the tripping events incident to their respective systems vide various SRPC mails. However, no replies have been received from APGENCO, TSTRANSCO during the period 29.10.2015 to 29.11.2015:

The Constituents have been requested to kindly furnish the remedial measures/ action taken in

time so as to forward the same to Central Electricity Authority. The updated list of the same as on 14.12.2015 is enclosed at Annexure-IV.

Minutes of the 49th


6. Certificate for Healthiness of Batteries

As per the MoP/ CEA direction given in pursuant to recommendations of the Enquiry Committee (NEW grid disturbance on 30th & 31st July, 2012), RPC’s are required to obtain from their respective Constituents the monthly certificate for healthiness of batteries, installed at 220 KV and above voltage level Substations (for power supply to Relays, RTUs and PLCC equipment) and furnish the same to CEA/ MoP.

With reference to above, the Constituents have been requested to submit the certificate on healthiness of batteries on monthly basis (i.e. status for a month may be sent by the 7th day of the following month) to SRPC.

The sought status for the month of October, 2015 has not been received from the following SR-Constituents:

APTRANSCO, TSGENCO (Hydro), PED, MAPS, SEL, CEPL, TPCIL

7. NPCIL Agenda Items (i) Frequent tripping of 230 kV KKNPP-Tuticorin S/c line: 230 kV switchyard of KKNPP is connected to TN STU network through 2 circuits of 230 kV

(one S/C each to Tuticorin and Nagercoil). These circuits are meant to provide "Off Site Power" to KKNPP. It has been observed that 230 kV KKNPP-TTPS line has been tripping very frequently on Zone-2 protection. As frequent tripping of the line degrades the reliability of "Grid supply" and loss of the same at 230 kV may affect the stability of nuclear units, TANTRANSCO has been requested to present action taken to ensure requisite stability.

In this regard, Action Taken Report furnished by TANTRANSCO vide their letter dated

28.11.2015 (copy enclosed at Annexure-V) was discussed and noted that requisite action has been initiated/ taken by TANTRNSCO to address the concerns raised by KKNPP.

(ii) Outage of Units -1&2 at MAPS due to the loss of evacuation lines on 9th November, 2015 On 9-11-2015, MAPS Unit -1&2 were generating 215 MW and 172 MW respectively with

three 230 kV lines in service (D/C to SP Koil Station and S/C to Acharapakkam Station). 230 kV MAPS- Arni line had tripped on previous day at 18:35 hrs. On next day (09-11-2015) starting from 08:22 hrs to 09:33 hrs, the cascade tripping of these 3 lines resulted in the outage of both the units.

The issue was discussed in the meeting. The deliberations and recommendations of PCSC

forum are given at Grid Disturbance I.5 in Annexure-II.

8. Power Swing Protection Philosophy

The Power swing protection philosophy as recommended by the Ramakrishna Committee (Task Force on Power System Analysis under Contingencies) [copy given at Annexure-VI] was discussed in the meeting. It is observed that while PGCIL, NTPC, NPCIL, NLC, and State Utilities of Karnataka, Kerala are in line with Task force recommendations in so far as unblocking it Zone-1 and blocking it in other zones, the State Utilities of Andhra Pradesh (AP), Telangana (TS), and TamilNadu (TN) are found to be blocking it in all Zones.

Minutes of the 49th


In this regard, it was agreed in the meeting that the matter would be favorably looked into by the above Constituents (of AP, TS & TN) and they would revert with their views after discussing with their respective managements.

9. Network configuration changes

As per the information furnished by SR-Constituents to the OCC forum in their 113th meeting

held on 06.11.2015 (Minutes circulated on 30.11.2015), the following network configuration changes (additions/ deletions/ modifications of transmission elements) took place in the southern grid during the month of October, 2015.

COD 220 kV Appayyadorapalem (ADR Palem) in Vizianagaram district was commissioned

on 15.10.2015 by APTRANSCO 220/132 kV Miyapur S/s of 1x160 MVA Transformer Capacity was augmented to 2x160

MVA Transformer Capacity on 07.09.2015 by TSTRANSCO. 220 KV D/C XLPE UG Cable from 220 kV Moulali SS to 220 KV GIS at Osmania University in

Hyderabad of ckm 17.926 was commissioned on 14.10.2015 by TSTRANSCO. 220 KV line on Narrow Based Multi Circuit Towers with 4 Circuits for LILO of both Circuits

of Dindi - Chandrayangutta 220 KV D/C Line to the proposed 220 kV SS, Bonguloor of ckm 2 was Commissioned on 31.10.2015 by TSTRANSCO.

LILO of 220kV Ramagundam- Mandamarry circuit-I to 220/6.6kV LI SS Murmur in Karimnagar district of 3.9 ckm was commissioned on 21.10.2015 by TSTRANSCO.

220 KV 2nd ckt stringing from 220 KV RSS 220 KV Mandamarry (34 KM) in Karimnagar of 34 ckm was commissioned by 20.10.2015 by TSTRANSCO.

LILO of 220kV Ogulapur- Durshed to 220/6.6kV LI SS Bommakal in Karimnagar district of 0.108 ckm was commissioned on 27.10.2015 by TSTRANSCO.

220/132 KV GIS Osmania University in Chilakalaguda, Hyderabad was commissioned on 14.10.2015 by TSTRANSCO.

220/6.6KV Murmur LI substation in Karimnagar district was commissioned on 21.10.2015 by TSTRANSCO.

220/6.6KV Bommakal LI substation in Karimnagar district was commissioned on 27.10.2015 by TSTRANSCO.

220/6.6KV Mallaram LI substation in Medak district was commissioned on 31.10.2015 by TSTRANSCO.

220/132 KVSS Bonguluru in Ranga Reddy Dist. (originally charged with 1x100MVA) was commissioned on 31.10.2015 by TSTRANSCO.

PGCIL vide their letter dated 16.10.2015 informed that consequent to the successful completion of Trial Operation, Transmission system associated with Kaiga 3 & 4 (2x235 MW) Project (Mysore-Kozhikode 400 D/C line along with new 400/220 kV S/S with 2x315 MVA ICTs and 2x50 MVAR switchable line reactors at Kozhikode and associated bay equipment at Mysore Substation) had been put under COD w.e.f 00:00 hours of 16th October 2015 in terms of Clause 4 of CERC(Terms and Conditions of Tariff) Regulations 2014.

Minutes of the 49th


10. Instances of SPS Operations Based on the information furnished by SRLDC, it is informed that there were no instances of SPS operations in SR during the period 29.10.2015 - 29.11.2015.

11. Compliance of Hon’ble CERC Orders 11.1 Petition No. 146/MP/2013 with I.A. 36/2013: Order dated 20.02.2014

Compliance of Regulations 5.2 (r) of the Grid Code: Issue regarding non-furnishing of FIR / Trip Analysis Report, EL, DR, etc. was also highlighted. It is pointed out that the above reports are to be submitted / uploaded on SRLDC web application within 24 hours as mandated under IEGC / CEA Regulations.

Implementation of Phase-I and Phase-II of Protection Audit Recommendations: All the constituents are requested to submit the updated status of the compliance (those who have not completed recommendations mentioned in the Phase I and Phase II) to SRPC Secretariat at the earliest.

Compliance of Regulations 5.2 (e) & 5.2 (l) of the Grid Code and Regulation 3(1)(e) of CEA Grid Standards: The constituents are requested to strictly comply with these provisions by ensuring standard protections systems having the reliability, selectivity, speed and sensitivity to isolate the faulty equipment and protect all components from any type of faults, within the specified fault clearance time and providing protection coordination

Ensuring proper maintenance of transmission lines and adopting best O&M practices: The constituents are requested to conduct line patrolling regularly as per the SRPC transmission line patrolling guidelines (available under the menu item "All Uploads Operation Miscellaneous Transmission Line Patrolling Protocol / Guidelines for Southern Region" on SRPC website). (http://www.srpc.kar.nic.in/website/2014/operation/patrolling.pdf).

11.2 Petition No. 167/Suo- Motu/2012: Order dated 22.02.2014

The Constituents are requested to follow approved protection philosophy ISTS licensees are requested to submit details of updated distance protection relay

setting of all inter-regional lines to POSOCO & RPCs.

All SLDCs are requested to install/activate sound recording system in their control rooms within three months from the date of issue of this order.

The Constituents are requested to submit the progress of implementation to SRPC and SRLDC as specified in the Hon'ble CERC Order.

11.3 Petition No. 263/MP/2012: Order dated 19.12.2013

Constituents are requested to implement the quantum of relief by AUFR and df/dt relays by identifying additional feeders and keep them functional within one month of issuing this order.

SLDCs are also requested to map these relays on their respective SCADA system within three months of issuance of this order.

The Constituents are requested to submit the progress of implementation to SRPC and SRLDC as specified in the Hon'ble CERC Order.

11.4 APTRANSCO’s Petition No.95/MP/2015: Date of hearing 09-04-2015

http://www.srpc.kar.nic.in/website/2014/operation/patrolling.pdf

Minutes of the 49th


It was noted in the Analysis and Decision part of the Order that:

“8. Noting the submissions of the petitioner, SRPC and SRLDC and activities initiated by the petitioner for procurement of materials required for implementation of the remarks of protecting audit, we allow time to the petitioner till 31.12.2015 for completion of our directions in Order dated 19.12.2013 in Petition No. 146/MP/2013.”

“9. SRPC is directed to monitor the status of completion of works relating to protection audit remarks in respect of 7 nos 400 kV sub-stations and 11 nos 220 kV sub-stations of APTRANSCO, protection audit remarks in Protection Coordination Sub-Committee (PCSC) meetings and coordinate the periodic protection audit to be carried out in Southern Region after deliberation in SRPC and submit bi-monthly report to the Commission.”

11.5 TSTRANSCO’s Petition No.83/MP/2015: Order dated 14-05-2015

It was noted in the Order that:

“12. Noting the submission of the petitioner, SRLDC and SRPC and considering the actions already initiated by the petitioner for implementation of works relating to protection audit, we allow time till 31.10.2015 and 31.8.2016 for implementation of Phase-I and Phase -II works respectively. The petitioner is directed to submit affidavit confirming the completion of Phase I of protection audit remarks by 31.10.2015 and Phase-II of protection audit remarks by 31.8.2016.

13. SRPC is directed to monitor the status of completion of remarks in these substations vis-à-vis protection audit remarks in Protection Coordination Sub Committee (PCSC) meetings. SRPC is further directed to coordinate the periodic protection audit to be carried out in Southern Region after deliberation in SRPC.”

11.6 Order in Petition No. 86/MP/2014 and 374/MP/2014: Order dated 18-08-2015

The time-lines given to the various SR-Constituents for completion of Phase-I and Phase-II activities of Protection Audit Recommendations vide above Order are given below: (A) KSEBL: 18. Noting the submission of KSEBL, SRLDC and SRPC and considering the actions already initiated by KSEBL for implementation of remarks of protection audit, we allow time till 31.12.2015 and 31.3.2016 for implementation of Phase-II works and R&M works at Idduki HEP respectively. (B) TANTRANSCO: 21. After considering the submissions of TANTRANSCO, SRLDC and SRPC, it is noted that

TANTRANSCO`s request for time till 31.5.2015 for implementation of Phase–I activities of providing numerical relays for feeder protection and Auto transformer protection is already over. We allow time till 30.6.2016 for other Phase-I activities such as provision of line VT, 5 core CT, Time synchronizing with GPS, Disturbance recorder & event logger and Phase-II activities. According to SRLDC, total implementation period is 15 to 16 months for items which involve major procurement, design changes with major site modification/civil activities. Accordingly, we allow 16 months time i.e up to 30.11.2016,

Minutes of the 49th


for Renovation and Modernization of Singarpet, Singaperumalkoil, Salem and Tondiarpet 230 kV sub-stations from the issue of the order.

(C) NLC: 22. NLC has sought time upto 31.12.2014 and 31.3.2015 for completion of Phase-I work of

Numerical Relay Retrofitting and for Phase-II works of providing second battery bank of PLCC respectively. It is noted that the completion dates for Phase-I and Phase-II of protection audit remarks as requested by NLC are already over. Therefore, no direction is required in this regard. However, we direct NLC to file a confirmation report regarding completion of protection audit works for Phase-I and Phase-II.

(D) KPTCL: 23. … … Considering the submission of KPTCL and SRLDC, we allow time to KPTCL time till

15.01.2016 for completion of Phase-I and Phase-II of protection audit remarks. No further extension shall be granted in this regard.

(E) KPCL: 24. … … Considering the submission of KPCL and SRLDC, we allow time to KPCL till 31.10.2015

and 31.12.2015 for completion of Phase-I for Phase-II of protection audit remarks respectively. No further extension shall be granted in this regard.

26. We direct SRPC to (a) submit status of protection audit remarks in respect of

APGENCO, NTPC (SR), Talcher, Puducherry, PGCIL (SRTS I & II), MAPS and TANGEDCO, (b) monitor the status of completion of remarks of protection audit in respect of all constituents of Southern Region in Protection Coordination Sub-Committee (PCSC) meetings, and (c) to coordinate periodic protection audit to be carried out in Southern Region after deliberation in SRPC. All the constituents of Southern Region are directed to file their status with SRPC on regular basis to facilitate proper monitoring in PCSC meetings. SRPC is directed to submit bi-annually status report to the Commission confirming the completion of Phase-I, Phase-II and R&M works of protection audit remarks of the constituents of Southern Region.

12. Nomenclature for naming various files uploaded in Web based Tripping Monitoring System of

SRLDC Portal

The nomenclature to be followed by the Constituents in naming various files (FIR, DR, EL, TR) corresponding to a tripping incident was brought out in the SRPC letter No. SRPC/ SE-III/ PCSC-45/ 4609 – 649 dated 26.06.2015 and in the minutes of PCSC-45 issued vide SRPC letter No. SRPC/SE-III/ PCSC-45/ 2015/ 5422-455 dated 21.07.2015. As illustrated therein, the format to be followed for the user entered part-name is given below:

Transmission Element File name to be given by the user

Transmission line SSN_DSN_line#_FT

Minutes of the 49th


Inter-connecting Transformer SSN_ICT#_FT

Generating Transformer SSN_GT#_FT

Generating Unit SSN_Unit#_FT

Where, SSN = Source Station Name/ From end Station Name/ Sending end Station Name

DSN = Destination Station Name/ To end Station Name/ Receiving end Station Name

FT = File Type (FIR/ DR/ EL/ TR)

All SR-Constituents are requested to kindly intimate the above file naming nomenclature to all the concerned and ensure that it is followed at all stations in their control area so that tripping analysis can be done systematically.

13. Date & Venue of the next Meeting

It is informed that the 50th PCSC meeting will be held on 29.12.2015 (Tuesday) at 10:30 hrs in the Conference Hall of SRPC, Bengaluru.

14. Vote of Thanks

Member Secretary, SRPC thanked the members and other participants for their active contribution in the deliberations.

Sh. Uday Trivedi, AVP, UPCL thanked all the Members for their cooperation.

*****

Annexure-I

Grid Occurrences discussed during 49th

PCSC Meeting on 30-11-2015 1/29

Grid Occurrences 1. Details of Grid Disturbances (GD’s):

1 Complete outage of 220kV Chikodi substation of KPTCL (GD-1)

(i) Date and Time of Event 13.10.2015 at 00:30 hrs

(ii) Location 230kV Chikkodi Substation

(iii) Reported Disturbance /

Fault

Tripped due of failure of 220kV Bus-2 PT at Chikkodi substation.

Lines tripped on zone-2 from Talandage and Mudshingi on

operation of Zone-2 protection. Bus bar protection is not

available at 220kV Chikodi substation

(iv) Load Loss

(v) Category GD-1

SLD:

As per FIR of KPTCL:

Annexure-II



KPTCL:

Pre fault: Entire Chikkodi and Belgaum sub station loads were fed from Maharashtra system. At Chikkodi, both the buses were tied through bus coupler.220kV Gataprabha 1 &2 lines were kept open at Chikkodi as Gataprabha SS was on Karnataka system.

At Chikkodi, normally Talandage and Mudshingi lines are generally kept on different buses, however due to some metering arrangement constraint (PT input) both lines were brought on to same bus, viz., Bus-B.

At 00:30hrs, R phase PT of 220kV Bus A failed and the incoming lines tripped at Talandage and Mudashinge Zone-2. This resulted in bus shut down at Chikkodi.

At Chikkodi, there was no bus-bar protection. Further as Bus Coupler’s O/C operating time is more than that of Zone-2, the lines got opened from remote ends in Zone-2.

During the incident, Load Loss: 143 MW for about 1 Hr 15 minutes. Energy unserved is 0.179 MU

Remedial Action: When enquired about provision of A/R on these inter-state lines, KPTCL representative informed that

control panels had already been replaced, but due to problem with output cards of REL-511, the matter was taken up with M/s ABB (OEM), and the relays would be soon replaced by REL-760, and the work is likely to be completed by December, 2015.

Regarding provision of bus-bar protection, it was informed that the same would be provided as part of their R& U proposal covering 96 SS in Karnataka, for which funding was sought from PSDF. It was also informed their proposal was approved during Appraisal Committee meeting held on 17.11.2015 and sent to CERC for further processing of the scheme as per PSDF disbursement procedure. Early sanctioning of PSDF grants from Monitoring Committee was awaited and thereafter LOA would be issued to the successful bidder M/s Alstom.

SRLDC/SRPC:

PMU plot shows the occurrence of two successive faults; while the first fault got cleared within 320ms, the second fault got cleared in 360ms.

After the breaker got opened upon first fault, reasons for the second fault need to be investigated. Whether this could be correlated with the burning of R-ph Wave-Trap at Talandage end on 220 kV Chikkodi – Talandage line as mentioned in the FIR may be seen by KPTCL.

2 Complete outage of IL&FS power station (GD-1)


(ii) Location 400kV IL&FS Station


Fault

Complete outage occurred at IL&FS due to tripping of evacuating

lines i.e. 400kV IL&FS-Nagapatinam line-1&2. Both lines tripped

due to mal-operation of Bus-1 and Bus-2 bus bar protection

(iv) Generation Loss 400 MW

(v) Category GD-1

SLD: 404, 405, 406 are in one dia with ILFS-1 line connected between 405 & 406;

407, 408, 409 are in one dia with ILFS-2 line connected between 408 & 409;

Annexure-II



Pre-Fault:

Post-Fault:

400 kV Nagapattinam – ILFS line-1: Nagapattinam (PGCIL-SR2) end:

As per FIR/ TR, line tripped at 19:44 hrs due to BBP operation caused due to mal-operation of CB-406 & CB-407’s Gas Density Monitor on 3rd Stage. (But from DR, only CB-406 got opened. Tie-CB 405 observed to be in OPEN condition prior to occurrence of this fault).

As per DR/ EL, the lines tripped at 19:44:46.362 hrs due to BBP (96A) operation. IL&FS end:

As per FIR/DR/EL/TR, the line tripped at 19:35:02.383 hrs due to DT receipt from Nagapattinam PS. From EL, it is observed that DT has been received several times starting from 19:35:02 hrs. to 19:44:46 hrs. The resolution in EL was limited to seconds only. 400 kV Nagapattinam – ILFS line-2: Nagapattinam (PGCIL-SR2) end:

As per FIR/ TR line tripped at 19:44 hrs due to BBP operation caused by mal-operation of CB-406 & CB-407’s Gas Density Monitor on 3rd Stage.(But from DR, only CB-409 got opened. Tie-CB 408 observed to be in OPEN condition prior to occurrence of this fault)

As per DR/ EL, the lines tripped at 19:44:46.362 hrs due to BBP (96A) operation. IL&FS end:

As per FIR/DR/EL/TR, the line tripped at 19:44:46.405 hrs due to DT receipt from Nagapattinam PS. The resolution in EL was limited to seconds only.

Annexure-II



PGCIL-SR2:

Gas Density Monitor (GDM) operation consist of three stages as given below: Normal stage SF6 Pressure:0.67Mpa

Stage1: <=0.64Mpa, Stage2:<=0.62Mpa , Stage3:<=0.60Mpa. It’s third stage operation causes BBP operation of the bus to which the concerned CB is connected.

In the instant case, first CB-407’s GDM operation in third stage caused BBP operation for Bus Bar -1 (top bus in the diagram). Then after 9 sec, CB-406’s GDM operation in third stage also caused BBP operation for Bus Bar – 2 (Bottom bus in the diagram). However as all Tie-CBs remained in service, the lines NLCTPS-Exp1 & NLC TPS 2 and , Trichy-1 & Trichy-2 got connected through Tie-CB 411 and Tie-CB 414 respectively.

On Examination at site, the pressure in 406-CB and 407-CB is found normal and tripping occurred due to mal-operation of gas density monitoring associated circuit.

The moisture entry in the associated circuit of gas density 3rd stage, caused mal-operation due to some contact problem with the miniature relays, and resulted in bus bar protection operation.

It was also found that the space heaters which keep LCC panels dry got accidentally got switched off

On this point, KKNPP representative informed that in their GIS, space heaters associated with GDM were not provided separately, but came as a built-in feature of GDM. Then, it was opined that could be due to design difference as PGCIL’s GDM is of China-make, and that of KKNPP is of Russian-make.

Remedial action: The Gas leakage detector healthiness checked. Precautions to avoid moisture entry in the panels have been taken to ensure no repetition of such

occurrences takes place. SRLDC/SRPC: As the Tie-CB’s 405 and 408 were found to be OPEN condition prior to occurrence of BBP operation from the

DR’s furnished, PGCIL (SR-II) needs to substantiate their statement by providing all the relevant EL’s.

At IL&FS end, the time-scale resolution in EL’s should be configured for msec. Time-sync for DR and EL needs to be ensured at IL&FS.

3 Complete outage of 220kV Ambewadi Substation of KPTCL (GD-1)


(ii) Location 220 kV Ambewadi Substation


Fault

220kV Nagjheri-Ambewadi line-1 tripped at 13:33 hrs due to B

phase to earth fault. Ambewadi was radially fed from Nagjheri

power station through 220kV Nagjheri-Ambewadi line-2. Tripping

of this line caused 220kV Bus shut down at Ambewadi and

remaining lines and transformers were hand tripped

(iv) Load Loss Karnataka: 14 MW and Goa: 97 MW

(v) Category GD-1

Annexure-II



SLD:

As per TR of KPTCL:

Ambewadi (KPTCL) end:

Prefault conditions: 220kV Ambewadi-Narendra 1 & 2 lines are under LC due to failure of insulator strings. Supa generation - Nil; Goa load on Ambewadi @ 14.00Hrs- 97MW; Karnataka load (11kV load of Ambewadi & 110kV loads) - 14MW

At 13:33hrs, Ambewadi-Nagjheri line-1 tripped on distance protection due to line fault and declared faulty. Line Clear was availed by TLI staff.

At 14:36 hrs, 220kV Ambewadi-Nagjheri line-2 tripped at Nagzari end on DPR in Zone-2(BN, 25km). This resulted in loss of supply to Ambewadi station as only source to Ambewadi was 220kV Nagjheri line-2.

220kV Ambewadi-Ponda line-1& 2 were hand tripped.

Load loss - Karnataka load : 14MW; Goa load:97MW and energy unserved was 0.0685 MU Restoration: 220kV Bus was restored by charging 220kV Nagjheri Ambewadi line- 2 at 14:50 hrs and 220kV

Ambewadi-Ponda line-1 was charged at 15:13hrs.

Line-1

Line-2

Line-1

Z2

NK

20 MVA

No Generation

XELDOM

55 MVA 100 MVA

Out of service

(Maintenance)

Hand trip

Z1 Z2

Line-2

AMBEWADI-

220kVAMBEWADI- 220kV

Annexure-II



KPTCL also informed that Ambewadi – Narendra D/C line which were taken on outage replace insulator strings would be put into service by mid-December, 2015.

KPCL

Presently A/R & Carrier protection is not present on Nagjheri – Ambewadi lines due to absence of CVT’s at Nagjheri. However, as the material was already received (in third week of November, 2015), carrier protection and A/R will be provided in 3-month period.

To this, SRLDC insisted KPCL for providing the same in one month time, to which KPTCL also conveyed their preparedness.

Recommendations:

KPCL to provide A/R on all 220 kV lines emanating from Nagjheri PH. KPTCL to provide A/R on all 220 kV lines emanating from Ambewadi SS.

4 Complete outage of 220kV Ambewadi Substation of KPTCL (GD-1)


(ii) Location 220 kV Ambewadi Substation


Fault

220kV Nagjheri-Ambewadi line-1 & 2 tripped at ambewadi end

only on operation of DEFR. This resulted in loss of supply to

Ambewadi station. Fault had occurred in 220kV Nagjheri-Hubli

line-2

(iv) Load Loss 4 MW

(v) Category GD-1

SLD:

220kV Ambewadi SS end: Prefault Conditions: 220kV Ambewadi-Narendra 1 & 2 lines were under LC due to failure of insulator strings. Supa generation : Nil Goa load on Ambewadi @ 16.00Hrs- 103MW Karnataka load (11kV load of Ambewadi & 110kV loads) - 12MW

Line-2

Line-1

Line-2

Line-1

PONDAP

ONDA

NARENDRA

SUPA HPS

(2X50 MW)

SUPA HPS

(2X50 MW)

NAGJHERI

NAGJHERI

AMBEWADI-

220kVAMBEWADI- 220kV

NK

20 MVA

110 kV

No Generation

XELDOM

55 MVA 100 MVA

Out of service

(Maintenance)

Hand trip

F (B-N)

DEFR

HUBLI

DEFR

DEFR Z2

Annexure-II



As per TR of KPTCL:

At 16.54 hrs, 220kV Ambwadi – Nagheri lines - 1 &2 tripped at Ambewadi end on DEFR. Due to this 220kV Bus got de-energized and the remaining lines and transformers were hand tripped.

Restoration: 110kV bus restored at 17.17 hrs by charging 110kV NK-2 line (220kV Sirsi source). 11kV Load of Ambewadi for about 4 MW was restored immediately. 220kV bus restored at 17.45 Hrs and 220kV Ponda -1 line restored at 17.50 Hrs.

Load loss : 11kv load of 4 MW for 20 minutes ( Karnataka) Goa load of 103MW for 53 minutes.

Energy Unserved in MU: 0.0923 MU. KPTCL:

Details of trippings occurred at Nagjheri were collected and it was observed that 220kV Ambewadi- 1 & 2 lines were not tripped at Nagzari end during the instance. However 220kV NPH-Hubli-2 line was tripped during the instance with following relay indications: At Nagjheri : 220kV Hubli-2 line tripped on DPR, Zone-2,CN, 88.5km, 3.1kA; At Hubli: NPH-2 tripped on DEFR. Suspected transient fault in the line. This line was restored at 18.24Hrs on

31.10.2015.

During this time, there was reversal of power flow on the Nagjheri - Ambewadi lines 1 & 2, i.e. from Ambewadi to Nagjheri on account of acting of tertiary winding of the transformers at Ambewadi in shunt to the fault (thus contributing to the fault point) even though there was no source at Ambewadi.

Remedial Action: As NPH- Hubli, NPH-Ambewadi lines are passing through dense forest, these lines are prone to high

resistance faults. Hence resistive reaches of distance relays of NPH connected lines at remote end sub stations i. e. at Hubli, Bidnal and Ambewadi have been revised to 75 ohms (primary).

DEFR time-lever has also been increased to 0.225.

Upon enquiry by SRLDC regarding non-furnishing of DR for the tripping event, KPTCL informed that presently DEFR operation was not configured for triggering DR. So it was recommended that KPTCL configure DEFR output also for triggering DR at Ambewadi SS.

5 Complete outage of S.P.Koil station of TANTRANSCO and generation loss at Madras Atomic Power station(MAPS) (GD-1)

(i) Date and Time of Event 09-11-2015at 9:33hrs

(ii) Location 230 kV MAPS Station and 230kV S.P.Koil Substation


Fault

Fault had occurred in 230kV MAPS-S.P.Koil feeder-1. LBB

protection got operated as breaker of this feeder was under

lockout and resulted in tripping of 230kV bus at S.P.Koil. Unit-

1&2 at MAPS due to loss of evacuating feeders i.e. 230kV MAPS-

S.P.Koil feeder-1&2

(iv) Generation Loss 250 MW

(v) Load Loss 150 MW

(vi) Category GD-1

Annexure-II



SLD:

Annexure-II



Annexure-II



MAPS is connected to four 230 kV lines, viz., SPKoil lines – 1 & 2 (L1 & L2); Acharapakkam line (L4); and Arni line (L3).

As per the Report dated 11.11.2015 furnished by MAPS:

230 kV Kalapakkam – Arani line (L3) was tripped on 08.11.15 first at 18:35 hrs, and then again at 19:06 hrs due to snapping of conductor between B-ph Wall Bushing & First Tower from MAPS. Strain insulator in the B-ph of first tower (towards switchyard) was also observed to have been damaged.

230 kV Kalapakkam – Acharapakkam line (L-4) was tripped on 09.11.2015 at 08:21 hrs due to snapping of Y-ph & B-ph conductors from First Tower to Second Tower from MAPS.

230 kV Kalapakkam – SP Koil line-2 (L-2) tripped on 09.11.15 at 09:02 hrs due to B-ph fault; and the line could not be normalised due to breaker problem at SP Koil end.

230 kV Kalapakkam – SP Koil line-1 (L-1) tripped on 09.11.15 at 09:33 hrs due to line fault.

As a result of losing of all four evacuating lines, both Units of MAPS tripped on Turbine Over Frequency protection.

No FIR/ DR/ EL furnished relating to tripping of Kalpakkam – SP Koil D/C lines and both Units of MAPS by NPCIL (MAPS).

As per the Report dated 27.11.2015 furnished by TANTRANSCO:

Annexure-II



230 kV Kalapakkam – SP Koil line-2 (L-2): SP Koil (TANTRANSCO) end:

As per FIR/ TR, the line tripped at 9:06 hrs on B-E fault due to DPR, Z2 operation. It was stated that A/R was in locked-out condition.

From DR, the line got tripped on B-E fault at 08:39:30.102 hrs. (Digital inputs were not shown) EL furnished was not proper (It does not show SOE). Time sync of DR & EL needs to be checked. From synchro-phasor data, the fault seemed to have got cleared in 160 msec. This means that the fault got

cleared due to DPR, Z1 operation from MAPS end. 230 kV Kalapakkam – SP Koil line-1 (L-1): SP Koil (TANTRANSCO) end:

As per FIR/ TR, On 09.11.2015 at 06:00 hrs., the CB at SP Koil end on SP Koil – MAPS line-1 was under lock-out due to Compressor’s low SF6 pressure.

Subsequently at 09:32hrs., line fault occurred in the above feeder, but due to lockout condition the breaker had not tripped; as a result, LBB relay acted and tripped all the 230kV feeders & all the 4 Auto transformers.

EL furnished does not show events after time 9:03:36:416 hrs. (After this, only following two events were shown:

Monday 09 November 2015 09:24:03.677 : Any Pole Dead OFF Monday 09 November 2015 09:24:03.672 : All Pole Dead OFF)

From DR, the line trip happened at 08:32:55.174 hrs on Y-E fault due to DPR, Z1 operation. But due to A/R’s lock-out condition, 3-ph trip was given. However, only R-ph and B-ph currents only became zero. It is observed that Y-ph current became zero only after 560 msec. (It was also observed that similar operation, viz., R-ph and B-ph currents becoming zero, and the y-ph current becoming zero only after 560 msec. was also observed in the DR furnished for SP Koil end on SP Koil – Kalavindapattuu 230 kV S/C line). Hence, whether this happened because of sluggish operation of LBB relay or PD relay needs to be found out).

From Synchrophasor data, fault clearing time was observed to be 560ms. Hence, the operation of LBB protection needs to be validated.

Time sync of DR & EL also needs to be checked. TANTRANSCO:

On the tripping day, there was heavy rain and thunderstorms around SP Koil area due to which operators could not attend to the low air pressure of compressor in time which resulted in locked-out condition of A/R relay. This resulted in tripping of the SP Koil – MAPS lines on line faults subsequently.

MAPS:

MAPS being a Nuclear Power Station, the evacuating lines from MAPS need proper line maintenance by TANTRANSCO. Further, when it was already known that MAPS was operating under depleted network conditions due to tripping of MAPS – Arani line the previous day, more vigilance should have been exercised by SLDC so that MAPS remained in grid mode of operation.

As such incidents happened in the past also, SRPC is requested to form a sub-committee to look into all protection & operational issues concerning MAPS, and suggest suitable corrective measures.

SRLDC:

The breaker of 230kV SP.Koil-MAPS feeder-1 was under lockout due to SF6 gas pressure low from 6:00 AM of 09-11-2015 and no actions were taken by TANTRANSCO to rectify the same till teh occurrence of the fault at 9:33 AM.

Apart from the line maintenance related issues, the proposed sub-Committee may look into the following issues concerning MAPS: Connectivity of MAPS from Bhavini for increasing the reliability of secure grid-operation of MAPS. Carrier –Communication & PLCC related issues; Modalities to bring down generation at MAPS in case of tripping of few evacuating lines from MAPS may

also deliberated by the proposed sub-Committee.

Annexure-II



SRPC:

A sub-Committee consisting of Officals from SRPC, SRLDC, PGCIL (SR-II), TANTRANSCO & MAPS would conduct a Protection System Analysis Group (PSAG-14) meeting at MAPS, Kalapakkam and deliberate on all protection & operational issues concerning MAPS.

Recommendations: TANTRANSCO to ensure correctness of operation of LBB relays at SP Koil. TANTRANSCO & MAPS to furnish their respective compliance report of the recommendations of to-be-

conducted PSAG-14 meeting at MAPS, Kalapakkam.

2. Details of Grid incidents (GI’s):

Sl. No.

क्र.स.ं घटनाकावििरण /

Details of Event

तारीख/ Date &

समय /Time कारण / Reason

शे्रणी/

Category

1 Multiple tripping at Nagjheri Hydro power station of KPCL

09-10-2015 at 11:43 hrs

220kV Nagjheri- Bidnal line tripped on operation of Directional earth fault protection due to suspected high resistance fault in line. Running Units -1&2 at Nagjheri power station tripped on operation of high set of back-up earth fault protection of Generator transformer protection. Remaining feeders at Nagjheri, i.e., Ambewadi-1, 2 and Hubli- 1 & 2 were not affected. Hubli-3 feeder was under shutdown

GI-1

SLD:

Nagjheri Capacity: 885 (5x150 + 1x 135) MW. Pre-fault conditions:

o Nagjheri – Kodasalli lines 1 & 2 were kept open. o Nagjheri – Hubli line -3 was under LC. (Check this because Nagjheri – Kubli is a D/C line only) o Units in service at Nagjheri: Unit-1 & Unit-4

220 kV Nagjheri – Bidnal line: Bidnal (KPTCL) end:

As per FIR, line tripped at 11:44 hrs on B-E fault due to OCR operation. No DR/EL furnished. Nagjheri (KPCL) end: As per DR/EL/ TR, the line tripped at 11:43:21.509 hrs on B-E fault due to operation of DEF (67N) protection.

In DR, no digital inputs (signals) were shown. In DR & EL the events/ signals or which protection operated to open the line were not shown.

It was stated that other 220 kV lines had not tripped.

Annexure-II



Nagjheri Units -1 &4 tripping:

As per TR, the Units tripped due to operation of (High Set of) GT OC & E/F protection. (Time not mentioned, Instantaneously?).

DR & EL were not furnished for any of the Units. SRLDC:

Delayed clearance of the fault on Nagjheri –Bidnal line-1 was observed from PMU plot. The fault was observed to have sustained from 11:42:54.480 hrs to 11:42:55.600 hrs to 11:42:55.760 hrs 1.120 sec & 160 msec.

All trippings with delayed fault clearance (more than 1 sec) would be informed to CERC. When asked about operation of SPS, KPCL replied that SPS at NPH was provided for Units- 3 & 6 only which

were not in service during the tripping event. KPCL:

Remedial action: Settings of Instantaneous elements of Generator Transformer back up protection would be reviewed. The IDMT relay responsible for delayed fault clearance would soon be replaced. KPTCL also informed that resistive reaches of distance relays of NPH connected lines at remote end sub

stations i. e. at Hubli, Bidnal and Ambewadi had been taken up for review and revised to 75 ohms (Primary).

2 Tripping of 765kV Kurnool-Tiruvalam line-2

12-10-2015 at 11:18 hrs

Buchholz-2 of B-ph line reactor at Kurnool mal-operated and caused tripping of Line. Direct Trip was received at Thiruvelam end.

GI-2

Tiruvalam (PGCIL-SR2) end:

As per FIR/ DR/ El/ TR, the line tripped at 11:18:19.714 hrs due to DT receipt from Kurnool end. Kurnool (PGCIL-SR1) end:

As per FIR/ DR/ EL/ TR, the line tripped at 11:17:12.399 hrs due to mal-operation of Buchholtz-2 of B-ph Line Reactor.

PGCIL (SR-I):

It is a typical case of mal-operarion as the Buchholtz relay contacts were latched without any pressure variation.

Remedial Action: In fact, in all the newly commissioned 765 kV lines, they have been experiencing problems with

WTI and Buchholtz relays, and the issue has been taken up with OEM. All the Buchholz / PRD WTI / OTI Relays supplied under package are being replaced by OEM.

Already WTI relay was replaced at Kurnool; Buchholtz would also be replaced shortly.

When enquired by SRLDC regarding time-frame of completion of above work, he informed that the work would be completed in 3 months time.

When asked about spare transformers’ WTI and Buchholtz relays, it was informed that they were also being replaced.

3 Tripping of 220kV Edamon-Tirunelveli line-1&2

12-10-2015 at 21:30 hrs

220kV Edamon-Tirunelveli lines -1&2 got tripped due to operation of Bus Bar protection which was due to human error

GI-1

220 kV Edamon – Tirunelveli line-1: Edamon (KSEB) end: As per DR, the line tripped at21:47:38.549 hrs due to BBP operation.

EL not furnished (Uploaded EL was same as FIR) Tirunelveli (PGCIL-SR2) end:

Annexure-II



As per FIR, the line was holding from their end. 220 kV Edamon – Tirunelveli line-2: Edamon (KSEB) end:

As per DR, the line tripped at 21:35:57.274 hrs due to BBP operation. EL not furnished (Uploaded EL was same as FIR) Tirunelveli (PGCIL-SR2) end:

As per FIR, the line was holding from their end.

Time sync between DR’s of both lines at Edamon end needs to be ensured. As per KSEB letter dated 27.11.2015:

SRLDC:

Had the tripping been due to accidental pressing of TEST LBB button of LBB, DT should have been sent to the remote end. But as this did not happen, KSEB should investigate the same.

Recommendations: KSEB to furnish reasons for DT not being sent to the remote end during the tripping event along with

remedial measures taken to PCSC forum.

4 Tripping of 400kV Gooty-NPS line-1

13-10-2015at 10:15 hrs

Direct Trip was sent to NPS end of line-1 during opening of Main CB of Gooty-NPS line-2 at Gooty end. This resulted in tripping of line-1 at NPS and line was holding from Gooty. Over voltage protection got operated at NPS end and resulted in tripping of line

GI-2

SLD:

Annexure-II



400 kV Gooty – NPS line-1: Gooty (PGCIL-SR1) end:

As per FIR, the line tripped at 10:15 hrs due to DT receipt from NPS end. From EL, DT receipt was observed at 10:09:31.750 hrs from NPS end. [Prior to this, it was observed that both

Tie-CB 2952 and NPS-II Main-CB 2852 were in OPEN position]

DR (trigger time = 10:12:23.417 hrs) furnished was not readable. Also the cause of trip was not clear (as no relevant digital signals were shown)

As per TR, while manually tripping Tie-CB (2952) and Main-CB (2852) of NPS-II, DT was sent to NPS end. Subsequently on receipt of DT from NPS end, the line tripped at Gooty end. It was stated that at the time of hand tripping of Main-CB of NPS-II, DT was sent to NPS-I end wrongly. Due to this, 400 kV Gooty-NPS line-1 tripped at NPS end. Subsequently, OVR, Stage-I protection operated at NPS end, and sent DT to Gooty end, due to which Gooty-NPS line-1 tripped at Gooty end.

However, there was no evidence for OVR, Stage-I operation at NPS end.

Time sync of DR, EL needs to be ensured. NPS (PGCIL-SR1) end:

As per FIR/ TR, the line tripped at 10:15 hrs due to DT receipt from Gooty end. As per EL, DT receipt ALARM (NOT TRIP) only was observed at 10:15:33 hrs. Further, Time-Stamp was not

configured to show events at msec level. The events corresponding to OVR, Stage-I operation were not recorded.

As per DR, the line tripped at 10:15:33.053 hrs due to DT receipt from Gooty end. Time-sync of NPS and Gooty with GPS needs to be ensured. PGCIL (SR-I):

Prior to tripping event, 400kV Gooty-NPS Line-2 was out of service. Line Reactor (LR) at Gooty end for line-2 was being used as bus reactor.

Line-2 was to be taken into service. For opening LR, Main & Tie breakers of line-2 were opened at Gooty end.

However due to wiring problem (during commissioning stage), DT was sent to line-1 at NPS end which resulted in tripping of line-1 CB’s at NPS end. Line-1 was holding from Gooty end. The DT-sent was also a spurious operation due to latching of CB auxiliary contacts.

Then, Over voltage, Stage-I protection got operated at NPS end and resulted in tripping of line-2.

Remedial action: Problem with wiring connections got rectified. Latched CB auxiliary contacts were also replaced.

Recommendations:

PGCIL (SR-I) to configure time scale resolution in Event Logger to msec. at Nelllore PS (NPS) and furnish DR

corresponding to OVR, Stag-I operation at NPS end during the tripping event. PGCIL (SR-I) to ensure time-sync of DR’s and EL’s with GPS at Gooty and NPS.

5 Tripping of Gazuwaka Pole-2

13.10.2015 at 12:28 hrs

HVDC Pole-2 win-2 breaker tripped on operation of differential protection of Bus-2 of east side. Loss of East Bus-2 voltage led to tripping of Pole-2

SLD:

Annexure-II



Pre-Conditions:

System Normal with Jeypore-Gazuwaka Line – I & II along with Line Reactors are in service Total Power Flow: 600MW E→S Pole - 1: 250 MW E→S Pole - 2: 350 MW E→S

Pole-2 East side WA2.W1.Q1 CB, connected to East Bus-1 was under shutdown condition for identification of SF6 Leakage points vide CPCC Code-CP/10/389 from 09:35 onwards.

Pole-2 East Bus voltage extended through WA2.W1.Q3 CB, connected to East Bus-2. Description of Fault:

At 12:28:06 Hrs on 13/10/2015, Voltage dip in the East Side was observed and HVDC POLE-2, East Bus-2 connected Breakers i.e WA2.W1.Q3 & WIN2.Q1 breaker tripped due to operation of “WIN2 Differential Current Phase L3 Trip” of East Bus-2.

Since East Bus Voltage was extended only through WA2.W1.Q3 Breaker i.e East Bus-2 as WA2.W1.Q1 CB (connected to East Bus-1) was under shutdown condition and tripping of WA2.W1.Q3 CB & WIN2.Q1 CB on above protection caused Loss to East Bus Voltage thereby tripping HVDC Pole-2 on “LOW DC VOLTAGE TRIP”.

Analysis:

DR Prints revealed current ZERO in Phase L3 (B-Phase) of WA2.W1.T3 CT connected to WA2.W1.Q3 Bay at the time of tripping, whereas the other two phases are showing healthy conditions i.e 182-Amps causing operation of “WIN2 Differential Protection” of East Bus-2 and loss of East Bus Voltage for HVDC Pole-2, thereby tripping the Pole on “Low DC Voltage Trip”

On detailed investigation it was found that the Core-4 B-Phase cable coming from WA2.W1.T3 CT Junction Box to Pole-1 Control room RTI-A System for East Bus Differential Protection had failed/earthed. The failure of particular core was confirmed through Continuity Check and Insulation Resistance measurement.

Remedial action: The trip was initiated by differential protection of RTI-A System. The protection in RTI-A system was

disabled and the same protection was made ACTIVE in redundant RTI-B system. The faulty CT cable from WA2.W1.T3 CT Junction box to Pole-1 Control room of length 1.5 km was

pleaced by spare, and PO for new cable ad already been placed. Normalization: At 14:06 Hrs, Pole-2 was Deblocked vide codes CPCC-414, NLDC- 433, SR-445, ER-351.

Annexure-II



UPCL:

Since, the said cable is of 1.5 km length, line differential protection may be provided for protecting the same.

Provision of CT supervision may also be explored.

6

Tripping at 220kV Nunna Substation of APTRANSCO. 400/220kV ICT-2 at Vijayawada substation also got tripped.

15.10.2015 at 16:14 hrs

220kV bus bar protection operated at 220 kV Nunna APTRANSCO substation due to fault. All elements connected to 220kV bus-2 got tripped

GI-I

As per FIR/TR of Nunna (PGCIL-SR1), ICT-2 tripped at 16:14 hrs due to BBP operation of 220 kV Bus of APTRANSCO.

As per DR of Nunna (PGCIL-SR1), ICT-2 tripped at 16:14:51.802 hrs (the causing digital signal was not shown)

As per DR of Nunna (APTRANSCO), BBP of 220 kV Bus-2 operated at 15:12:12.264 hrs due to Y-ph bus fault. Time sync of Nunna (APTRANSCO) SS. Remedial Action: APTRANSCO informed that Aluminium wire had fallen on the 220KV BUS-2 and created the bus fault. Bus

bar protection operated and cleared the fault by tripping the Bus -2 connected Feeders, ICTs/PTRs. Protection was in order.

When enquired about time sync of Nunna-AP SS, APTRANSCO representative informed that GPS is not available at Nunna. However, they have planned to provide the same in a phased manner.

7 Tripping of 765/400kV ICT-2 at Kurnool Substation

15-10-2015 at 17:10 hrs

ICT tripped due to mal-operation of B-phase HV WTI trip

GI-2

As per FIR/ TR, ICT-2 tripped at 17:10:12 hrs due to mal-operation of HV B-ph WTI Trip. As per DR/ EL, ICT-2 tripped at 17:10:13 hrs due to mal-operation of HV B-ph WTI Trip. EL resolution was not configured to show events at msec level. Remedial action: This problem which was being experienced in all the newly commissioned 765 kV lines was

taken up with OEM and all the Buchholz / PRD WTI / OTI Relays supplied under package would be replaced by OEM.

At Kurnool, WTI relays were replaced by availing shut down on 17th and 18th Nov, 2015.

8

Tripping of 400kV Vemagiri-Sattenapalli line and 400kV Vemagiri-Kalpakka line

25-10-2015at 10:56hrs

B-phase to earth fault had occurred in line. From Vemagiri end D.R, three phase trip and Tie-CB LBB operated was observed. Sattenapalli end had auto-reclosed, however breaker at Satenapalli tripped 8 sec after A/R on receipt of DT from Vemagiri as observed from EL of Satenapalli station. For 400k Vemagiri-Kalpakka line at Vemagiri end, Tie LBB operation and Grp-A/B trip was observed and direct trip was sent to Kalpakka end

GI-2

400 kV Vemagiri – Sattenapalli line: Vemagiri (APTRANSCO) end:

As per DR/EL, line tripped at 10:55:39.487 hrs on B-E fault due to A/R operation. During A/R dead time, T-LBB operated at 10:55:39.559 hrs to result in 3-ph trip.

Annexure-II



Sattenapalli (APTRANSCO) end:

As per EL, the line tripped at 10:56:19.203 hrs on B-E fault due to A/R operation, and successfully auto-reclosed after one second. But it again tripped at tripped at 10:56:29.457 hrs due to DT receipt from Vemagiri.

DR furnished was for second event (DT receipt) only. DR for the first event (for A/R operation) was not furnished.

If this DT receipt was due to T-LBB operation at Vemagiri end, then this time delay of 10 sec is inadmissible.

400 kV Vemagiri – Kalpakka line-1: Vemagiri (APTRANSCO) end:

As per DR/EL, the line tripped at 10:55:39.572 hrs due to operation of Tie-CB LBB protection. Kalpakka (APTRANSCO) end:

As per EL , the line tripped at 10:53:01.704 hrs due to DT receipt from Vemagiri

As per DR , the line tripped at 10:57:19.324 hrs due to DT receipt from Vemagiri Time sync of DR & EL needs to be ensured. APTRANSCO:

Vemagiri – Sattenapalli line and Vemagiri – Kalpakka line-1 are in the same dia. In the above dia at Vemagiri , Tie-CB has two auxiliary relays;

o One is for tripping its corresponding Main-CB and sending DT to Kalpakka and o The other is for tripping corresponding Main-CB sending DT to Satenapalli and.

On Tie LBB operation at Vemagiri end, Kalapkka line got tripped at Kalpakka end on DT receipt. On B-phase to earth fault, Satenapalli line auto-reclosed successfully. But after 8 seconds, Satenapalli line

tripped on OVR, Stage-I operation at Vemagiri.

Remedial Action: APTRANSCO representative informed that Tie-CB LBB auxiliary trip relay mal-operated. It was replaced

with spare relay, and feeders taken into service. SRPC:

The tripping of Vemagiri – Sattenapalli line due to T-LBB / OVR, Stage I operation could not be conclusively established from the DR & EL furnished in this regard.

Recommendations:

APTRANSCO to furnish a report on the tripping of 400 kV Vemagiri – Sattenapalli line along with relevant DR & EL showing clearly the successful operation of A/R followed by T-LBB/ OVR, Stage-I operation.

9

Tripping of 400/220 kV ICT-3 at Thrissur substation

25-10-2015at 11:04 hrs

Tie LBB protection of CB 405 resulted in tripping of breakers connected to 400kV Bus-1 along with main breaker of ICT-3. This in turn resulted in tripping of ICT-3 at Thrissur.

GI-2

KSEB:

Annexure-II



Remedial action: Grading capacitor across CB-401 was replaced. The CBF relay was sent for repair works.

Annexure-II



10 Tripping of 400kV Gooty - NPS line-1

26-10-2015 at 14:30 hrs

Line tripped on operation of REF protection at Gooty end and Direct Trip was sent to NPS end.

GI-2

Gooty (PGCIL-SR1) end:

As per FIR/TR, the line tripped due to operation of Reactor’s REF protection (64R). DT was also sent to NPS-1 end.

As per EL, the line tripped at 14:28:06.211 hrs due to Grp A & B trip relay operation. As per DR, the line tripped at 14:29:30.842 hrs. NPS (PGCIL-SR1) end:

As per FIR/DR/EL/TR, the line tripped at 14:30:46.290 hrs due to DT receipt from Gooty end. PGCIL (SR-I):

There was a problem with NGR-CT polarity, due to which its REF protection operated accidentally. Subsequently, it was rectified.

11

Tripping of 400/220 kV ICT-2 at Kurnool Substation and 400kV Kurnool-Srisailam line

26-10-2015 at 14:31 hrs

400kV Kurnool-Srisailam line - distance protection zone-2 had operated at Srisailam end. However from DR, R-phase to earth fault and zone-2 start were observed. Breakers at Kurnool end tripped on direct trip receive from Srisailam end. ICT-2 Main-CB tripped due to operation of bus bar protection, and Tie-CB tripped due to DT receipt from Srisailam

GI-2

SLD:

The SLD of 400/220 kV Kurnool SS as provided by APTRANSCO is attached at the end for reference. At 400 kV Kurnool SS, ICT-2 and Srisailam line are in the same dia. 400 kV Kurnool – Srisailam line: Kurnool (APTRANSCO) end:

As per FIR/ TR, the line tripped at 14:31 hrs due to DT receipt from Srisailam end DR, EL were not furnished to verify above operation. Srisailam end:

As per FIR, the line tripped at 14:31 hrs on R-E fault due to DPR, Z2 operation. As per DR/ EL, the line tripped at 14:29:44.489 hrs. But only Z2 Start (at 14:29:44.442 hrs) and DEF Start (at

14:29:44.449 hrs) were seen. Tripping of ICT-2 at Kurnool SS of APTRANSCO: As per FIR, ICT-2 Main-CB tripped at 14:31 hrs due to operation of BBP; Tie-CB tripped on receipt of DT signal

from Srisailam end. DR, EL not furnished. APTRANSCO:

ICT-1 Main-CB was availed Shutdown due to isolator problem. During maintenance, isolator of its earth switch got closed accidently which created a bus fault. Due to this , ICT-2 Main-CB got tripped.

The Tie-CB tripped along with Main-CB of Srisailam line due to DT receipt from Srisailam end. In the past also, APTRANSCO lines’s connected to Srisailam LB received DT in case of any kind of fault

occurring at Srisailam LB or on lines emanating from Srisailam LB.

Annexure-II



TSGENCO:

At Srisailam end, newly commissioned relays (numerical) appeared to have configuration problems due to which DT is being sent to remote ends wrongly.

Remedial action: The matter had already been taken up with their OEM, and hope to resolve it at the earliest.

Recommendations: TSGENCO in coordination with APTRANSCO to carry out end-to-end testing of PLCC channels by 15.12.2015

on 400 kV Srisailam – Kurnool S/C line and 400 kV Srisailam – Sattenapalli D/C line. TSGENCO and APTRANSCO to make A/R functional on 400 kV Srisailam – Kurnool line. TSGENCO to resolve configuration problems with the newly commissioned relays at Srisailam LB so that

unwarranted DT sending to remote ends is addressed.

12 Tripping of 400/220kV ICT-2 at Chittoor substation

26-10-2015at 17:00hrs

ICT-2 at Chittoor tripped due to suspected mal-operation of Buchholtz relay.

GI-2

As per FIR, ICT-2 tripped at 16:59 hrs due to operation of Buchholtz relay.

From DR, ICT-2 tripped at 16:59:40.433 hrs due to operation of Buchholtz relay. The causing event was not recorded in the EL furnished. Remedial action: APTRANSCO representative informed that the line tripped due to mal-operation of ABB-make Buchholtz

relay. As a remedial measure, it was replaced with another relay of Areva make.

13

Tripping of running Units 1 & 3 at Rayalaseema TPS of APGENCO

31-10-2015 at 03:30 hrs

While synchronizing Unit-5 with grid, Bus bar protection of 220kV Bus-1 operated which resulted in de-energization of 220kV Bus-1. This resulted in tripping of running Unit-1&Unit-3, 220kV lines Pulivedula-1, Yeralaguntla-1, Chinakampalli-1, Timmapura

GI-1

SLD:

** Above is a part-SLD showing Unit-IV and Unit-V. Complete SLD is enclosed at the end.

Annexure-II



Tripping of Units – 1 & 3 of Rayalaseema TPS of APGENCO:

As per FIR/ TR of APGENCO, Unit-5 of Rayalaseema TPP got tripped at 01:24 hrs on Flame Failure. In the process of taking Unit-5 back, TG set was kept 3000 RPM. During building-up of Generator Voltage, GT-5 LBB operated resulting in actuation of BBP of 220KV Bus-1. As a result, all out going feeders, GT-1, GT3, ST-1 &ST-5 on Bus-1 got tripped at 03:30 hrs.

From DR of Unit-5, it was observed that at 03:30:26.903 hrs that voltage was absent in R-phase. Also Dead-Machine condition and Class-A trip were observed 80 msec. subsequent to that.

From PMU data, dip in R-phase voltage was observed for 320ms. APGENCO:

While synchronizing Unit-5 manually, as the voltage build-up of generator reached around 10.5 kV, GCB got closed accidentally, and resulted in shorting/ burning of control cables. Due to this, closing pulse from the CB was not received by the main-relay, and dead-machine condition prevailed. This led to Class-A trip of Unit-5 generator protection. However, as the breaker failed to open, it resulted in BBP operation of 220 kV Bus-1.

Remedial action: The GCB Closing circuit was thoroughly checked in the presence of M/S. BHEL engineer from EDN

Bengaluru. 25CX (sync check relay) and k3-02 (GCB closing command) NO contacts have been incorporated in the

negative path of the GCB closing circuit along with the existing positive side. In the closing circuit of GCB, the Auto synchronising path and DEAD BUS closing path were completely

removed. Only manual closing path is kept after verifying thoroughly. New cables were laid for 220 Volts DC supply to GCB marshalling box for closing and tripping circuits. Close & open feedbacks of GCB poles are hooked up in protection relay disturbance record. The closing command output at GCB local panel was monitored by introducing an auxiliary relay. A NO

contact of this relay was connected to disturbance record of RET-670 relay. In the DVR auto channel soft start time was increased to 45seconds from 12 seconds in order to build up

the generator voltage in slow ramp to avoid inrush current. In manual channel Ifo (NO LOAD FIELD CURRENT), setting S885 was changed to position ‘0’ from position

‘A’. It will help in building up of generator voltage in slow ramp so that inrush current due to generator transformer charging shall be avoided.

After all the above checks the closing and protection tripping of GCB was checked and found OK

As regards keeping synchronization facility in auto-mode, it was informed that in the past with sync-facility in auto-mode, a fire accident took place in the cable gallery in which several control cables got burnt. Also they generally experienced abrupt changes in voltages and currents with auto-mode. As such, they have kept it in manual mode. The matter was referred to their OEM, M/s BHEL who had suggested to keep it under observation in mode for some time.

NLC:

Auto synchronization should be enabled where 25Ax relay is available, for it not only monitors the pre-conditions for synchronising, but also activates on-line correction signals, if necessary, to satisfy the conditions for synchronising, and ensures proper closing at right time. This is in place at NLC stations.

UPCL:

For CB closing circuit, negative breaking system, in which the sync-pulse will be transmitted from (-)ve, may be employed to secure operation of primary switching. (In this regard, a paper presented by Sh. Sanjay Bhatt,

UPCL is enclosed at Reference-I for kind perusal). Recommendations:

In view of the availability of 25AX, APGENCO shall keep synchronizing facility in auto-mode after getting it’s operation verified by its OEM, M/s BHEL.

Annexure-II



14 Tripping of 220kV Ambewadi-Ponda line-1

31-10-2015at 11:51hrs

Line tripped on operation of directional earth fault protection, and distance protection had not sensed the fault.

GI-1

As per FIR, the line tripped on operation of DEF (67N) protection, and distance protection had not sensed the fault. The Currents recorded were Ia-284.2A, Ib-309.5A, Ic-566.9A.

The DR (with trigger time = 10:51:47.715 hrs) furnished may not be related to this tripping event, as while Ia, Ib became zero, Ic did not. Also no digital signals were shown.

In the EL furnished, no events relating to present tripping were observed between 10:00 hrs to 12:00 hrs. KPTCL:

The fault was well beyond the resistive reach of the distance relay. Remedial measures: The resistive reaches of distance relays of NPH connected lines at remote end sub stations i. e. at Hubli,

Bidnal and Ambewadi were taken up for review and revised to 75 ohms (Primary). DEFR time lever was also modified to 225ms.

15 Trippings at Raichur TPS

12-11-2015 at 00:30 hrs

Running Unit-4, 5 and Unit-8 and 400kV RTPS-Yeramaras TPS feeder got tripped due to de-energization of both 400kV Bus-1&2 at Raichur TPS

GI-2

RTPS Configuration: 400 kV – 1090 (4x210 MW + 1x250 ) MW 220 kV – 630 MW (3x210) MW SLD:

As per TR of RTPS of KPCL:

Running Units - 4, 5 & 8 and 400kV RTPS-Yeramaras TPS feeder got tripped due to de-energization of both 400kV Buses - 1&2 at Raichur TPS. Remaining 400kV lines, Units at 220kV level (Unit1,2 &3) and 400/220kV ICT-1&2 were not affected during the incident.

Unit-6 is under planned shutdown for annual overhaul from 28-10-2015. Unit-7 was tripped on auxiliary supply failure on 07-11-2015. Generation loss was 460 MW due to tripping of Units - 4, 5 & 8. Triggering incident: While building up voltage in Unit-7, (around 10kV) Unit-7 got tripped on operation of GT

neutral over-current protection. Simultaneously Main and Tie CB’s LBB of Unit-7 got operated. As a result, Main breakers connected to 400kV Buses - 1&2 got tripped (there was no other element in dia of Unit-7). 400kV Raichur line-1 got connected to ICT-2 through Tie-CB Mahboobnagar line got connected to Munirabad line through Tie-CB. Units - 4, 5 & 8 got tripped as the Main and Tie breaker are connected to Bus-1 & Bus-2 respectively

(there was no second element in the respective dia’s). As Unit-6 was already under planned shutdown, Yeramarus feeder got tripped on tripping of Main

breaker connected to 400kV Bus-2.

Annexure-II



It was stated that as bus bar protection was electromechanical, DR & EL were not available for the incident. What about Stand-alone EL?

Reasons for operation of GT neutral over-current protection, and subsequent LBB-operation of Main-CB and Tie-CB of Unit-7.

SRLDC:

From PMU plots, three faults were observed, which got cleared with a delay of 320 ms, 400 ms, and 120 ms. Reasons for 3 successive faults and their delayed clearance.

SOE of RTPS was not recorded at SLDC SCADA and same needs to be checked. Reasons for why the fault went undetected by GT’s primary protection (Differential or REF) need to be seen. KPCL: On 12.11.2015 at 00:30hrs, during voltage build up of Unit-7 around 10KV, Unit-7 tripped on operation of GT

neutral over current protection (51NGT) due to surface conduction over the Main & Tie breakers. LBB relays of Main & Tie breakers got operated leading to Bus-1 & 2 bus bar relay operation.

Observation: As informed by the shift staff that, heavy sound & arcing observed near Unit-7 Main & Tie breakers. On

detailed inspection it is observed that, B-pole (RYB) of Unit-7 Tie breaker interrupter got ruptured. Due to this 51 NGT of Unit-7 operated and initiated class-A & LBB. Since, the surface current was persisting more than 200 milli seconds leading to tripping breakers connected to bus-2.

Due to surface conduction over the Unit-7 main breaker, (Bus-1) LBB relay of main breaker also operated simultaneously, leading to tripping breakers connected to bus-1.

Reason : The reason for surface current is due to deposition of ash, heavy mist & humidity. The Unit-7 bay is very

near to the cooling towers.

When enquired about hot-line washing, it was informed that an accident happened while carrying out hot-line washing of RTPS connected lines some time ago, subsequent to which it was temporarily put on hold.

To this, SRLDC stated that hot-line washing is essential to avoid fog-trippings and other unwarranted trippings due to deposition of dust on insulators.

UPCL:

Under the circumstances as above, a dedicated breaker-flashover protection comes in handy. Breaker failure schemes are specifically employed to provide backup protection in the event that a circuit breaker fails to operate properly during fault clearing. (In this regard, a write-up on Breaker flask-over protection, and a paper presented by Sh. Sanjay Bhat, UPCL on “Adaptive Logic for Breaker Flashover protection” are enclosed

at Reference-II and Reference-III for kind perusal). Recommendations:

KPCL to carry out hot-line washing of RTPS-connected lines regularly to avoid trippings due to fog and dust. KPCL may see the feasibility of providing breaker flashover protection at RTPS, and implement the same if

possible.

3. Failure/ Non-operation of Auto-reclose during transient fault

Sl. No. Element Date & Time Reason

1

Tripping of 220kV Sabarigiri-Theni line

09-10-2015 at 16:56 hrs

Line tripped on a R-phase to earth fault. At Sabarigiri, relay gave a 3 phase trip after 220ms. From Theni end D.R, auto reclose block was observed.

Theni (TANTRANSCO) end:

As per FIR/ TR, the line tripped at 16:56 hrs on R-E fault due to carrier-aided trip.

Annexure-II



From DR, the line tripped in R-ph at 16:49:44.002 hrs on R-E fault due to carrier-aided trip. However, within 100 msec, A/R block was observed;

EL not furnished (Furnished EL was the last part of DR) Sabarigiri (KSEB) end:

As per FIR/ TR, the line tripped at 16:56 hrs on R-E fault due to DPR, Z1 operation (Distance 52.8 km). From DR/ EL, R-E fault got detected at 17:02:21.749 hrs; however, as the A/R status was not ready, it gave a

3-ph trip and sent carrier to the other end at (17:02:21.749 hrs + 241 ms). It was also observed that EF trip was blocked.

The delay in fault clearance for DPR, Z1 operation needs to be explained. KSEB:

The fault was of high resistance type due to arcing to tree branches in the forest. It was suspected that the fault could have been first picked up by DERF (this explains A/R not ready status),

and it slowly developed into a Zone-1 fault, due to which line tripped sending carrier to the remote end. Recommendations:

KSEB to furnish a report on the tripping incident along with the remedial measures taken to PCSC forum.

2 Tripping of 220kV Gummidipoondi-Sullurupeta line

14-10-2015 at 23:22 hrs

As per FIR, line tripped on a Y-phase to earth fault. Line did not auto-reclose.

Gummidipoondi (TANTRANSCO) end:

As per FIR/DR/EL/TR, line tripped at 11:20:12.971 hrs on Y-E fault due to DPR, Z1 operation (Distance = 36.96 km). As A/R provision was not present, the line tripped in 3-ph.

Remedial Action: Temporary fault; Feeder charged from Sullurpeta end at 23:38 hrs and tied at Gummudipoondi end

23:40 hrs. Sullurupeta (APTRANSCO) end:

As per FIR, the line tripped at 23:17 hrs on Y-E fault due to DPR, Z1 operation. As per DR/EL, the line tripped at 11:17:52.516 hrs on Y-E fault due to DPR, Z1 operation. As A/R provision

was not present, the line tripped in 3-ph. Status of Provision of A/R:

TANTRANSCO and APTRANSCO informed that A/R would be made functional on Gummidipoondi – Sullurupeta line by the last week of December, 2015.

As regards providing A/R on 400 kV Chittoor – Tiruvalam D/C line, material procurement it was informed that material procurement is under progress, and A/R would be made functional in one to two months time.

3 Tripping of 220kV Ambewadi-Ponda line-1.

17-10-2015at 14:01 hrs

line tripped on a B-phase to earth fault. There is no provision for auto-reclose for line

Ambewadi (KPTCL) end:

As per FIR, the line tripped on B-E fault (fault current = 6.87 kA, fault distance = 3.498 km) due to DEFR and DPR, Z1 operation.

From DR/EL (trigger time = 13:58:09.455 hrs), the fault current seemed to have sustained for 750 msec, after which only “Any Trip” acted.

KPTCL:

As per the information available from the field people, it was definitely a Zone-1 fault. However, the reasons for delayed fault clearance would be analysed and furnished to PCSC forum.

The A/R for this line was covered under KPTCL’s U&R proposal for their 93 SS, and would be provided under those works.

Annexure-II



4

Tripping of 400kV Krishnapatnam-Chittoor line-1

19-10-2015 at 07:49 hrs

R-phase to earth fault had occurred in line. Chittoor end tried for auto-reclose. However, due to persistent fault, breaker at Chittoor end tripped. Krishnapatnam end relay did not try for auto-reclose and gave a 3 phase trip as observed from D.R

Krishnapatnam TPS (APGENCO) end:

As per FIR/ DR/ EL, the line tripped at 07:49:44.182 hrs on R-E fault due to DPR, Z1 operation (fault distance = 58.1 km).

The line did not try for A/R, and simply gave a 3-ph trip. Why? (In DR, addition signals - TEF1_STFW, ZCOM_CS – were observed)

Chittoor (APTRANSCO) end:

As per FIR/ DR/ EL, the line tripped at 07:49:44.182 hrs on R-E fault due to DPR, Z1 operation.

The line tried for A/R, but gave 3-ph trip due to persistent fault. APGENCO:

A/R was kept out of service at the time occurrence of tripping as there were only two evacuating lines [SDSTPS – Chittoor & SDSTPS – Nellore (AP)] then. Now with the commissioning of second circuit of both the lines in November, 2015, APGENCO agreed to put A/R into service. To this, SRLDC requested to keep A/R functional on all lines emanating from Krishnapatnam TPS by 10th December, 2015.

Recommendations: APGENCO to make A/R functional on all lines emanating from Krishnapatnam TPS by 10th December, 2015.

5 Tripping of 400kV Kaniyambeta-Kadakola line

28-10-2015at 12:08 hrs

Line tripped on a Y-phase to earth fault. There is no provision for auto-reclose

Kaniyampeta (KSEB) end:

As per FIR/ DR, the line tripped at 12:08:39.106 hrs on Y-E fault due to DPR, Z1 operation (FD = 30.47 km; FC = 1643 A)

No EL furnished. In DR, various Voltages & Currents should be shown separately (instead of superimposing); Time scale was

also very restrictive (configured to show only 300 msec).

Remedial Action: As per the information from field, after line patrolling, no fault or permanent tree touching found in the

Kerala area. A semi permanent fault is suspected to be in the maintenance area of Kadakola. (The fault location is around 35km).

Kadakola (KPTCL) end:

As per FIR/ DR. the line tripped at 12:02:00.776 hrs on Y-E fault due to DPR, Z1 operation (FD = 69.5 km; FC = 8 p.u.).

No EL furnished.

3-ph trip happened due to absence of A/R Remedial action: Transient fault; stood OK after test charging.

SRLDC:

KPTCL should provide 1-ph A/R from Kadakola end, as in case of transient faults supply can be restored within one second.

Recommendations:

KPTCL to provide A/R on Kadakola – Kaniyampeta line at Kadakola end.

Annexure-II



4. Lines tripping due to tripping at one end/PLCC mal-operation

Sl. No.

क्र.स.ं घटनाकावििरण /

Details of Event

तारीख/ Date &

समय /Time

कारण / Reason

1 Tripping of 400 kV Mysore-Kozhikode line-2

31-10-2015at 16:19 hrs

Line tripped at Mysore end only on Direct trip receipt.

Kozhikode (PGCIL-SR2) end:

As per FIR, the line was kept holding. Mysore (PGCIL-SR2) end:

As per FIR/ DR/ EL/ TR, the line tripped at 16:19:57.294 hrs due to DT receipt from Kozhikode end. Remedial Action: Tripped at Mysore end only on receipt of DT from Kozhikode end. Suspected DC earth fault at Kozhikode.

The DC earth fault was rectified. SRPC/ SRLDC:

PGCIL (SR-II) may carry out PLCC end-to-end testing for this line to ensure carrier communication is intact.

2 Tripping of 400 kV JSW-BTPS line

10-10-2015 at 12:14 hrs

Line tripped at BTPS end only and was holding from JSW. R-phase CVT fuse fail had caused tripping at BTPS end

JSWEL end:

As per FIR/ TR, the line was kept holding. BTPS (KPCL) end:

As per FIR/ DR/ TR, the line tripped at 12:12:21.351 hrs due to External Trip caused due to R-ph fuse failure of CVT

Remedial Action: KPCL: Trip occurred due to CVT "R" Phase fuse failure. CVT Fuse replaced. Tested and found OK.

SRLDC:

In case of VT/ CVT fuse failure, the relay should block tripping. However, during such block if a fault occurs (this can be detected from neutral current), the block should be released.

Annexure-II



SLD of Rayalaseema TPS (Courtesy: APGENCO)

Annexure-II

Meeting

No /

Index

Details of

Event

Date Reason PCSC Recommendations Utility

Responsible

for

implementat

ion

Status of Recommendations

as on 14-12-2015

Remarks

45/II/14 Tripping of

400/220 kV

ICT-1&2 at

Gooty

substation

31-05-2015at

06:37 hrs

As per FIR, ICT-1&2 tripped on

operation of directional overcurrent

and earth fault protection. It was

reported that there was fault in

220kV APTRANSCO system

1. APTRANSCO to check resistive reach of the

distance relays on 220 kV Gooty SS – Gooty

RS line

2. APTRANSCO to check time coordination of

distance relay on Gooty SS – Gooty RS line at

Gooty SS with Gooty ICT’s (1 & 2) back-up

protection.

APTRANSC

O

Yet to be informed Pending

APTRANSC

O

APTRANSCO to furnish a report on the

tripping of 400 kV Vemagiri – Sattenapalli line

along with relevant DR & EL showing clearly

the successful operation of A/R followed by T-

LBB/ OVR, Stage-I operation.

Pending Implementation of PCSC Recommendations (30th to 49th)

Andhra Pradesh42/II/3 Outage at

Regulapadu

station of

APTRANSC

O

21-02-2015

at

00:49 hrs

Y-Ph Metering PT failed at 220KV

Ragulapadu Substation. Fault got

cleared

by tripping of lines from remote

ends.

APTRANSCO to furnish the remedial

measures taken in consequent to the tripping

incident along with the status of bus bar

protection and bus coupler at Regulapadu S/s.

A/R feature to be enabled on Regulapadu –

Alipuira 220 kV inter-state line.

APTRANSC

O

Mail recieved on 22-08-2015:

APTRANSCOhas planned to commission ABB make ETL-41 type

PLCC terminal along with NSD-50 type protection coupler at

Ragulapadu end towards Alipura. vide our Ltr Dt 23-07-2015, it is

requested KPTCL to arrange ABB make ETL-41 cabinet with NSD-

50 type protection coupler for establishing PLC communication

between Alipura- Ragulapadu.

Pending

B-phase to earth fault had occurred

in line. From Vemagiri end D.R,

three phase trip and Tie-CB LBB

operated was observed.

Sattenapalli end had auto-reclosed,

however breaker at Satenapalli

tripped 8 sec after A/R on receipt

of DT from Vemagiri as observed

from EL of Satenapalli station.

For 400k Vemagiri-Kalpakka line

at Vemagiri end, Tie LBB

operation and Grp-A/B trip was

observed and direct trip was sent to

Kalpakka end

25-10-2015

at 10:56 hrs

Tripping of

400kV

Vemagiri-

Sattenapalli

line and

400kV

Vemagiri-

Kalpakka line

49/II/8 PendingYet to be informed

Annexure-III

Page 1 of 24


running Units

1 & 3 at

Rayalaseema

TPS of

APGENCO

31-10-2015

at 03:30 hrs

While synchronizing Unit-5 with

grid, BBP of 220kV Bus-1

operated which resulted in de-

energization of 220kV Bus-1. This

resulted in tripping of running Unit-

1&Unit-3, 220kV lines Pulivedula-

1, Yeralaguntla-1, Chinakampalli-

1, Timmapura

In view of the availability of 25AX,

APGENCO shall keep synchronizing facility in

auto-mode after getting it’s operation verified

by its OEM, M/s BHEL.

APGENCO Yet to be informed Pending

49/III/4 Tripping of

400kV

Krishnapatna

m-Chittoor

line-1

19-10-2015

at 07:49 hrs

R-phase to earth fault had occurred

in line. Chittoor end tried for auto-

reclose. However, due to persistent

fault, breaker at Chittoor end

tripped. Krishnapatnam end relay

did not try for auto-reclose and

gave a 3 phase trip as observed

from D.R

• APGENCO to make A/R functional on all

lines emanating from Krishnapatnam TPS by

10th December, 2015.

APGENCO Yet to be informed Pending


400kV

Ghanapur-

Mamidapalli

line

15-04-2015

at 2:03 hrs

Line tripped at Mamidapalli end

only and was holding at Ghanapur.

Overvoltage protection had

operated at Mamidapalli

TSTRANSCO to make DR

functional at Mamidipalli

TSTRANSC

O

TSTRANSCO informed vide their mail dated 24.06.15 that the

existing relays would be replaced with numerical relays in DPR

works.

Pending

Telangana

Annexure-III

Page 2 of 24

48/II/5 Tripping of

400kV

Nagarjunsaga

r-

Mahboobnaga

r line

07-09-2015

at 2:58 hrs

Line tripped on operation of OV

protection at Mahboobnagar and

DT received at N’sagar station. DT

receive was observed in DR and

EL of N’sagar station. D.R/EL of

Mahboobnagar was not furnished

to validate the overvoltage tripping

TSTRANSCO to furnish a detailed report on

the tripping event along with remedial

measures taken to PCSC forum.

TSTRANSC

O



220kV

Gajwel-

Shankarapally

line

20-09-2015

at 2:24 hrs

line tripped at Gajwel end on R-

Phase to ground fault. Reason for

non-auto reclose could be

established as DR and EL of both

ends were not furnished

• TSTRANSCO to furnish a detailed report on

the tripping event along with remedial


TSTRANSC

O


47/I/1

(GD)

Disturbance

in Srisailam

left bank

power station

18-08-2015

at 15:25 hrs

PendingYet to be informedTSGENCO1. TSGENCO to check the reclaim time of A/R

and set it at 25 sec at KTPS.

2. TSGENCO to carry out PLCC end-to-end

testing in coordination with PGCIL (SR-I) for

KTPS – Khammam

line-2; retrofitting of Protection Coupler may

be carried out based on the test results.

Y-phase to earth fault had occurred

in line. From Khammam end DR it

was observed that the relay after

dead time tried for auto-reclose.

The fault was persisting and relay

gave a single phase

trip instead of a 3 phase trip after

1.25sec. R& B pole voltage dip

after 2 sec possibly due to

operation of pole discrepancy.

Auto-reclose close command

observed after 2.5 seconds

and all poles got closed.

30-07-2015

at 6:08 hrs

PendingYet to be informedTSGENCO1. TSGENCO to disable sensitive earth fault

protection provided as supplementary to static

bus-bar

protection at Srisailam LB (GIS).

2. TSGENCO to set the current setting for

phase-to-ground faults for numerical bus-bar

protection at a suitable value so that the

prominent high-resistance earth faults

occurring within the bus-zone are

covered at Srisailam LB (GIS).

Tripping of

400kV

Khammam-

KTPS line-2

400kV Srisailam-Mamidapalli line-

2, 400kV Srisailam- Satenapalli

line-2 and 400 kV Srisailam-

Kurnool line tripped during

multiple tripping at Srisailam

power station. 400kV Srisailam-

Mamidapalli-1 and 400kv

Srisailam-Satenapalli-1

was kept out of service due

over-voltage conditions. There was

no generation at Srisailam left bank

power station. Triggering incident

was failure of CT in 400kV

Srisailam- Satenapalli line-2 at

Srisailam end.

47/II/6

Annexure-III

Page 3 of 24

34/III/1 400kV

Raichur-

BTPS line

26-06-2014 Transient fault in R-phase.

Line did not auto reclose

A/R at BTPS end to be made operational

within one month

KPCL 1. A/R for 220kV lines enabled already.

2. Shut down of lines availed to commission the auto reclosing schme

for 400 kV line at BTPS.


Timer relays have been received at site. A letter has been addressed to

M/s Alstom to complete the work on priority basis.


Commissioning of Autorecloser planned on 14, 15 & 16th of Dec-

2015 subject to availability of LC.

Pending

Karnataka30/I/A RTPS

Tripping

incidents and

the Spl

meeting held

at RTPS on

13th and 14th

March 2014

Mar-14 Spl meeting held at RTPS on 13th

and 14th

March 2014

The PCSC forum recommended for

replacement of existing electromechanical

relays with Numerical relays.

KPCL Mail recieved on 21-10-2015 and 23-11-2015:

1) Replacement of Old electromagnetic relays with Numerical relays

has been completed for RTPS-BTPS line & commissioned on

18.03.2014.

Raichur-PG1 & Raichur-PG2 lines have already retrofitted with

numerical relays.

2. Job order placed on 26.06.2015 on M/s Alstom T&D India Ltd.

Chennai for retrofitting of relays for all 220kV lines at RTPS.

3. Retrofit of existing bus bar(CAG-34) with numerical version–

Budgetary offers obtained and is under process.

38/GD/3.

5

GD-1 at

Kadra and

Kodasalli

hydro power

station

13-11-2014

at 19:31hrs

A fault had occurred in 220 kV

Kadra and

Kodasalli. As A result, de-

energization of

220kV bus occurred at Kadra and

Kodasalli.

1. The PCSC forum requested KPCL to speed

up the installation of Numerical Distance

Protection relay in Kadra –Kaiga and

Kodasalli –Kaiga.

2. The PCSC forum requested KPCL to submit

the implementation status of PSAG-10

recommendations within a week’s time.

KPCL Mail recieved on 21-10-2015:

NIT floated on 5.5.15 through e-portal. Bid evaluation completed.

LOA's issued to M/s Schneider Electric Infrastructure Ltd. on

08.10.2015.


LOA's issued to M/s Schneider Electric Infrastructure Ltd. on

08.10.2015. Engineering work is in progress.

Pending

Pending

Annexure-III

Page 4 of 24

38/GD/3.

2

GD-1 at

Guttur

Substation of

KPTCL

05-11-2014

at 11:42 hrs

Circuit breaker of 400kV Guttur-

Hiriyur

line-1 failed at Guttur end while

availing

shutdown for replacement of CVT.

The

failure of breaker caused bus fault

at Guttur.

KPTCL was requested to expedite the early

implementation of pending recommendations

of:

1. Protection Audit (Phase-I & Phase-II)

2. PSAG-4, PSAG-5, and PSAG-8

KPTCL Mail received on 27-05-2015 & 29-07-2015:

Latest satus of implementatin of Phase-1 &2 recommendations,

PSAG 4,5 and 8 is being obtained from field. The Status will be

updated witin a weeks time.

Pending

39/I/5 Tripping of

400/220kV

ICT-2 at

Hoody

substation of

KPTCL

01-12-2014 Suspected mal-operation of 220kV

side Rphase

over current relay

1. PCSC forum recommended KPTCL to

replace the relay with a different make.

2. KPTCL was also requested to train the

O&M personnel adequately before performing

any maintenance works to avoid such unwanted

trippings.

KPTCL Mail received on 27-05-2015 & 29-07-2015:

C&R panels of 500MVA ICT 1&2 will be replaced under

scheduled R&M works. O&M personnel are instructed to take

sufficient care in order to avoid unwarrented trippings.

Pending

34/I/6 400/220 kV

ICT-1 & 2 at

MUNIRABA

D

16-07-2014 As reported directional over

current relay of ICT’s operated

due to snapping of line jumper

in 220kV Lingapur line.

1. Bus bar protection shall be provided by

asset owner ( i.e KPTCL).

2. Settings for main distance protection &

Overcurrent protection shall be examined and

reviewed.

3. Time synchronization of the Substation

shall be ensured.

4. Correct DR shall be submitted to the SRLDC

for trip analysis.

KPTCL Mail recieved on 27-05-2015 (KPTCL):

1. KPTCL has taken action to provide bus bar protection to 220kV

buses.

2. Over current relay Settings of ICTs to be reviewed by PGCIL.

Mail received on 29-07-2015 (KPTCL):

Initial Tendering stage

Pending

38/GD/3.

1

GD-1 at

Mahalingapur

a Substation

of KPTCL

25-10-2014 Fault had occurred in 220kV

Mahalingapura-Narendra line-2.

Due to the

failure of relay operation at

Mahalingapura,

breakers at remote end tripped

which

resulted in bus dead condition.

1. PCSC forum recommended KPTCL to

replace the old static distance protection

relays with numerical relays.

2. PCSC forum also requested KPTCL to

provide a broken conductor alarm indication in

Control Room.

3. Standing instruction needed to be given to

the all substation personnel for not changing

the relay settings without approval of RT/MRT

wing.

KPTCL Mail received on 27-05-2015 (KPTCL) & 29-07-2015:

1.Existing Back up relays will be replaced by numerical type

distance relays.Procurement is in tendering stage. Remaining

observations were attended.

Pending

Annexure-III

Page 5 of 24

40/IV/1 220kV Sedam-

Tandur line

20-12-2014

at 22:20 hrs

Line tripped on Yphase to earth

fault from both the ends

KPTCL was requested to explore the

possibility of providing A/R feature to this

line and submit the remedial measures to the

PCSC forum.

KPTCL Mail recieved on 29-07-2015:

Carrier protection is being restored for 220kV Sedam-Tandoor line at

Sedam end. After restoring the carrier protection , AR will be

enabled.

Pending

40/I/1 GD-1 at

220kV

Ambewadi

Station of

KPTCL

22-12-2014

at 21:22 hrs

Triggering incident was B-phase to

earth fault in 220kV Ambewadi-

Nagzari line-1. B-pole of breaker

did not open at Ambewadi end.

LBB protection not available at

Ambewadi end. All elements

tripped on Zone-2 from remote

ends.

1. Till the completion of R&M works for bus

bar and LBB protection, KPTCL shall explore

the possibility of having split bus operation

at Ambewadi and submit the details of the

same to PCSC forum.

2. KPTCL shall provide the details of the

tripping of Supa hydro station connected

downstream from 110 kV bus.

KPTCL Mail recieved on 29-07-2015:

Action is being taken by KPTCL for operating Ambewadi in split bus

mode. Problem in bus coupler breaker is attended.Isolator

overhaulling work is completed.PTs are already provided to 220kV

Bus-II. After commissioning of Bus-II PTs, Ambewadi can be

operated in split bus mode. Pending works will be completed within a

months time.

Pending

Mail received on 28-05-2015:

1. Main-2 relays already installed and commissioned.

2. DC fuses are intact. Till date no such incidence occurred.

3. Possibility of DC-1 & DC-2 arrangement and splitting of DC will

be reviewed.

Mail received on 07-07-2015 , 21-10-2015 and 23-11-2015:

1. Completed.

2. Completed.

3. Possibility of DC-1 & DC-2 arrangement and splitting of DC will

be reviewed.

Pending41/I/1 GD-1 at

220kV Kadra

power Station

of KPCL

16-02-2015

at 12:56 hrs

Triggering incident was B-phase to

earth fault had occurred in 220kV

Kadra-Kodasalli line. Line tripped

from Kodasalli end only. 220kV

Kaiga-Kadra tripped in Zone-3

from Kaiga end. Tripping of

evacuating lines caused bus shut

down at Kadra hydro station.

1. KPCL to make functional the Main2

(EPAC) relay with the help of KPTCL at the

earliest.

2. KPCL to investigate the reason for DC

fuse fail during transient fault in 220kV Kadra-

Kodasalli line including the testing/ checking

of DC supply cables, breaker control cables,

and trip coils.

3. KPCL to ensure supply for Main-1& Main-

2 protections, Trip Coils (TC1, TC2) from

separate battery banks.

KPCL

PendingMail received on 29-07-2015:

1. Procurement of Bus bar and LBB protection is in the final

tendering stage.

2. Action is being taken to restore the carrier protection for 220kV

Sedam-Tandoor line. AR will be enabled after restoration of PLCC.

KPTCL 1. KPTCL to provide Bus bar and LBB

protections for 220 kV bus at Sedam S/s.

2. KPTCL to implement A/R feature on 220

kV Sedam-Tandur inter-state line.

R-Phase to ground fault occurred

on 220kV Sedam-Shahpur line.

Fault not cleared from Sedam end

due to stuck-breaker condition.

While the Sedam- Sahapur line

tripped from Shahapur end in Zone-

1, the other 220 kv lines from

Sedam tripped at remote ends in

Zone-2. This caused complete

outage of 220kV Sedam substation.

27-01-2015

at 8.00 hrs

Complete

outage at

220kV Sedam

Substation of

KPTCL (GD-

1)

41/I/4

Annexure-III

Page 6 of 24

42/I/1

(GD)

Complete

outage of

220kV Sedam

substation of

KPTCL

15-02-2015

at 14:24 hrs

Fault occurred in 220kV Sedam-

Shahpur line

1. KPTCL to provide Bus Bar protection and

LBB protection at Sedam S/s and furnish

the status of their implementation to PCSC

forum.

2. KPTCL to implement A/R feature on 220 kV

Sedam-Tandur inter-state line.

KPTCL Mail received on 29-07-2015:


tendering stage.



Pending

42/I/2

(GD)

Complete

outage of

220kV

Ambewadi

substation of

KPTCL

12-03-2015

at 7:51 hrs

Fault in 220kV Ambewadi-

Nagjheri line-2

1. KPTCL shall provide A/R feature on

Ambewadi – Ponda 220 kV D/C inter-state

line.

2. Till the completion of R&M works for bus

bar and LBB protection, KPTCL shall explore

the possibility of having split bus operation at

Ambewadi and submit the details of the same

to PCSC forum.



tendering stage.



Pending

42/II/2 Tripping of

220kV

Chikodi-

Talandage

and

Mudshingi

line

20-02-2015

at

06:40 hrs

Lines tripped during test charging

220kV

Chikodi-Belgaum line-2 from

Chikodi

end.

1. KPTCL to provide A/R feature on the 220

kV Chikkodi – Talandage, and 220 kV

Chikkodi –Mudashinge inter-state lines.

2. KPTCL to carry out E/F relay coordination

for Chikkodi - Talandage and Chikkodi –

Mudashinge lines in coordination with

Maharashtra.


Action is taken for enabling AR for Mudashinge and Talandage lines.

Work is scheduled during first week of August 2015.

Pending



tendering stage.



KPTCL 1. KPTCL to provide Bus bar and LBB

protections for 220 kV bus at Sedam S/s.

2. KPTCL to implement A/R feature on 220

kV Sedam-Tandur inter-state line.

R-Phase to ground fault occurred

on 220kV Sedam-Shahpur line.

Fault not cleared from Sedam end

due to stuck-breaker condition.

While the Sedam- Sahapur line

tripped from Shahapur end in Zone-

1, the other 220 kv lines from

Sedam tripped at remote ends in

Zone-2. This caused complete

outage of 220kV Sedam substation.

27-01-2015

at 8.00 hrs

Complete

outage at

220kV Sedam

Substation of

KPTCL (GD-

1)

41/I/4

Annexure-III

Page 7 of 24


400/220kV

ICT-1 at

BTPS

14-01-2015

at 1:09

hrs

ICT tripped due to operation of

Over current and Earth fault relay

KPCL to check the possibility of providing line

differential protection between RTPS and

Yermarus stations.

KPCL Mail received on 07-09-2015 , 21-10-2015 and 23-11-2015:

Revised relay settings are awaited from KPTCL.

Revised relay settings furnished by KPTCL will be incorporated in co-

ordination with KPTCL shortly.

Pending


400kV

Raichur-

BTPS line

01-06-2015

at 01:02 hrs

line tripped on R-phase to earth

fault. Line did not auto-reclose

KPCL to make A/R operational on 400 kV

RTPS – BTPS S/C line at both ends.

KPCL Mail recieved on 23-11-2015:

Completed at RTPS end.

Pending

44/II/3 Tripping of

220kV

Kaiga-

Kodasalli

and 220kV

Kodasalli-

Nagjheri line-

1

22-04-2015

at

20:28 hrs

220kV Kodasalli-Nagjheri line-1

tripped from Kodasalli end on

operation of distance protection,

zone-2.

220kV Kodasalli-Nagjheri line-

1&2 is kept opened from Nagjheri

end, hence fault

could not be cleared with carrier

aided protection. Backup earth

fault relay at Kaiga end got

operated during the event and

resulted in tripping of 220kV

Kaiga- Kodasalli line from Kaiga

end.

1. KPCL to check the possibility of

implementing Permissive Over Reach (POR)

with Echo feature at Kodasally end.

2. If the above is not possible, KPCL shall

check the possibility of keeping the 220kV

Kodasalli-Nagjheri lines OPEN at Kodasalli

end and idle-charged at Nagjheri end, and

implement the same.

KPCL Mail received on 07.07.2015:

The matter had been discussed with KPTCL. KPTCL recommended

to keep Zone-2 time lever to zero. If this is acceptable, then the same

shall be incorporated immediately.

Mail received on 07-09-2015 , 21-10-2015 and 23-11-2015:

The matter has been discussed with KPTCL. KPTCL recommended to

keep Zone-2 time lever to zero.

If this is acceptable to SRLDC, then the same shall be incorporated

immediately.Reply from SRLDC is awaited.

Pending

PendingMail recieved on 23-11-2015:

1) Completed

3) Two bus operation for 220kV buses : In place of existing CT

switching relays, High speed manual heavy duty change over switch

of sufficient current capacity will be retrofitted to all feeders at 220kV

station and same will be operated manually during changeover of

feeder by one bus to the other and this arrangement may facilitate to

put both buses in service. Time required for this retrofit is around

90days . However, this work will be taken up only after retrofitting of

electromagnetic relays with numerical relays for Main-2 protection of

all 220kV lines, for which work is in progress.

KPCL1. KPCL to check the operation of anti-

pumping relay on 220 kV side and keep it in

healthy condition.

2. KPCL to provide manual reset to the 220 kV

side master trip relay.

3. KPCL to use both the 220 kV buses as main

buses under normal operation, and should go

for single bus operation only during

emergencies.

07-06-2015

at 01:35 hrs

Trippings at

220kV

Raichur TPS

46/II/21

Annexure-III

Page 8 of 24


220kV

Ambewadi-

Ponda line-2

02-08-2015

at 13:20 hrs

Line tripped on a transient fault in

B-phase. There is no

provision for auto reclose.


220kV

Ambewadi-

Ponda line-1

08-08-2015

at 10:51

hrs and 09-

08-2015 at

11:15 hrs

Line tripped on a B-phase to earth

fault. Line tripped as there is no

provision for auto-reclose


220kV

Ambewadi-

Ponda line-1

17-08-2015

at 13:20 hrs

Line tripped on a transient fault .

There is no provision for Auto

reclose.

Complete

outage of

220kV

Peenya

Substation in

Karnataka

48/I/2

(GD)

PendingYet to be informedKPTCL KPTCL to revise distance relay settings at

Nelamangala end for 220 kV Nelamangala –

Hebbal - Peenya line – 1 for the effective line

length of 17 km. These new settings can be

appropriately reviewed as and when the tie-

arrangement at Hebbal is done away with.

All connected 220kV lines and

transformers were taken on 220kV

North bus as South bus was under

shut down for conversion of strung

bus to rigid bus and isolator

replacement under R&M works.

Failure of HV side Y phase CT of

150MVA Transformer-3 occurred

at Peenya Substation which

resulted in operation of Differential

and HV REF protection. The

failure of CT also resulted in a

220kV bus fault in North Bus.

27-09-2015

at 4:23:17

hrs

PendingYet to be informedKPTCLKPTCL to activate non-directional Over

Current protection with a time delay of 600-

800 msec for Fuse

failure condition at Lingasugur.

Till A/R is put into service on Ambewadi-

Ponda line-1, KPTCL to reduce Zone-2 time

setting to zero sec. at Ambewadi end.

KPTCL Yet to be informed Pending

220kV RTPS-Lingasugur line-2

tripped at TPS end on operation of

distance protection zone-1.

400/220kV ICT-2 got tripped on

operation of earth fault protection.

220kV RTPS-Lingasugur line-

1&3 tripped on distance protection

zone-2 and zone-3 respectively.

Due to

tripping of ICT-2, the running units

got overloaded and it was

mentioned that under frequency

occurred as units are on load

control. The Units got tripped

on under frequency.

06-08-2015

at 4:51 hrs

Tripping of

Unit-1&2

along with

400/220kV

ICT-2 at

Raichur TPS

47/II/13

Annexure-III

Page 9 of 24

48/I/3

(GD)

Outage of

220kV

Ambewadi

station in

Karnataka

30-09-2015

at 10:41 hrs

220kV Ambewadi-Nagjheri line-2

tripped on B-phase to earth fault.

This resulted in loss of supply to

220kV Ambewadi bus. 220kV

Ambewadi-Ponda line-1&2 were

hand tripped after deenergization

of bus at Ambewadi.

KPTCL to fast-track providing A/R on all 220

kV lines emanating from Ambewadi SS to

prevent Station shut-down on temporary faults.


48/I/4

(GD)

Complete

outage of 220

kV HSR

substation of

Karnataka

06-10-2015

at 16:32 hrs

All connected 220kV lines at

220kV HSR substation i.e.

Somanahalli, EPIP, Hoody and

Nagnathapura tripped during the

incident. Triggering incident was

fault in 220kV HSR-EPIP line

KPTCL to review distance relay settings at

Naganathpura SS in view of LILO arrangement

at HSR Lay-out.


49/II/15 Trippings at

Raichur TPS

12-11-2015

at 00:30 hrs

Running Unit-4, 5 and Unit-8 and

400kV RTPS-Yeramaras TPS

feeder got tripped due to de-

energization of both 400kV Bus-

1&2 at Raichur TPS

1. KPCL to carry out hot-line washing of RTPS-

connected lines regularly to avoid trippings due

to fog and dust.

2. KPCL may see the feasibility of providing

breaker flashover protection at RTPS, and

implement the same if possible.

KPCL Yet to be informed Pending


400kV

Kaniyambeta-

Kadakola line

28-10-2015at

12:08 hrs

Line tripped on a Y-phase to earth

fault. There is no provision for auto-

reclose

• KPTCL to provide A/R on Kadakola –

Kaniyampeta line at Kadakola end.

KPCL Yet to be informed Pending

Pending1. KPCL to provide A/R on all 220 kV lines

emanating from Nagjheri PH.

2. KPTCL to provide A/R on all 220 kV lines

emanating from Ambewadi SS.

220kV Nagjheri-Ambewadi line-1

tripped at 13:33 hrs due to B phase

to earth fault. Ambewadi was

radially fed from Nagjheri power

station through 220kV Nagjheri-

Ambewadi line-2. Tripping of this

line caused 220kV Bus shut down

at Ambewadi and remaining lines

and transformers were hand tripped

29.10.2015

at 14:34 hrs

Complete

outage of

220kV

Ambewadi

Substation of

KPTCL

49/I/1.3

(GD)

Yet to be informedKPTCL

Annexure-III

Page 10 of 24

45/II/12 Multiple

tripping at

400/230kV

Alamathy

substation

25-05-2015at

09:08hrs

As per FIR, failure of R-phase CT

of 230kV Alamathy-Manali feeder

occurred at Alamathy end. Hence

230KV BBP Zone 1 & 2 Operated

at Alamathy substation. All the

230KV feeders, 230KV BC, ICT-3,

4 & 5 LV breakers got tripped.

TANTRANSCO to furnish a detailed tripping

report including reasons for delayed clearance

of fault at Almathy.

TANTRANS

CO

Mail received on 03-09-2015:

The faults were cleared with out time delay at Alamathy SS. Detailed

Tripping report sent vide Lr.No.CE/P&C/SE/D/

EPC4/AEE3/F.SRPC/ D.21/15, dated 14.07.2015.

The reasons for the delayed clearance of the third fault not

furnished.

Pending

48/I/1

(GD)

Disturbance

in 220kV

Tamilnadu

system

05-09-2015

at 14:04 hrs

Complete outage of 230kV

Palladam, 230 kV

Othakalmandapam S/s, 230 kV

Coimbatore S/s, 230 kV Thudialur

and 230 kV Sadayapalayam S/s

TANTRANSCO to take suitable measures like

installing more stub-towers along 230 kV OK

Mandapam – Myvady line to avoid excessive

sag due to over-loading.

TANTRANS

CO


48/II/6 Tripping of

400/220kV

Alamathy

ICT-3,4&5

07-09-2015

at 04:24hrs

Triggering incident was failure of

Y & B phase CT failure in 230kV

Korattur feeder

1. TANTRANSCO to furnish a detailed report

on the tripping event covering the sequence of

events, and the remedial measures taken to

PCSC forum.

2. TANTRANSCO to configure Bus-Bar

protection at Alamathy for instantaneous

operation.

TANTRANS

CO


PendingTANTRANSCO vide their mail dated 24.06.15 informed that

different relays in Main-I & Main-II would be ensured at the earliest.


Different relays in Main-I & Main-II will be ensured.

TANTRANS

CO

TANTRANSCO was requested to swap the

relays between two stations, so that

Main-1 and Main-2 will be of different make at

each station.

Line-2 tripped on R-phase to earth

fault.

Line autoreclosed at SVChatram

end and failed to reclose at

Alamathy end. Bphase to earth

fault in line-1. Line tried for A/r

but due to permanent fault line did

not reclose. ICT tripped on

operation of over flux protection.

29-03-2015

at

15:29 hrs

Tripping of

400kV

Alamathy-

SVChatram

line-1&2

and

400/230kV

ICT

at

S.V.Chatram

43/II/5

Tamil Nadu

Annexure-III

Page 11 of 24

49/II/3 Tripping of

220kV

Edamon-

Tirunelveli

line-1&2

12-10-2015

at 21:30 hrs

220kV Edamon-Tirunelveli lines -

1&2 got tripped due to operation of

Bus Bar protection which was due

to human error

KSEB to furnish reasons for DT not being

sent to the remote end during the tripping event

along with remedial measures taken to PCSC

forum.

KSEB Yet to be informed Pending


220kV

Sabarigiri-

Theni line

09-10-2015

at 16:56 hrs

Line tripped on a R-phase to earth

fault. At Sabarigiri, relay gave a 3

phase trip after 220ms. From Theni

end D.R, auto reclose block was

observed.

KSEB to furnish a report on the tripping

incident along with the remedial measures

taken to PCSC forum.

KSEB Yet to be informed Pending

PendingYet to be informedTANTRANS

CO

1. TANTRANSCO to ensure correctness of

operation of LBB relays at SP Koil.

2. TANTRANSCO & MAPS to furnish their

respective compliance report of the

recommendations of to-be-conducted PSAG-14

meeting at MAPS, Kalapakkam.

Fault had occurred in 230kV

MAPS-S.P.Koil feeder-1. LBB

protection got operated as breaker

of this feeder was under lockout

and resulted in tripping of 230kV

bus at S.P.Koil. Unit-1&2 at

MAPS due to loss of evacuating

feeders i.e. 230kV MAPS-S.P.Koil

feeder-1&2

09-11-2015at

09:33 hrs

Complete

outage of

S.P.Koil

station of

TANTRANS

CO and

generation

loss at

Madras

Atomic

Power

station(MAP

S)

49/I/1.5

(GD)

KeralaMail recieved on 30-10-2015:

1. Purchase procedures is still in progress.

2. Replaced.

3. PLCC equipment Tested and found OK.

Pending

(Recomm

endation

No.1)

44/I/1

(GD)

Complete

outage of

Idukki Hydro

Power Station

(GD-1)

28-04-2015

at 12:30 Hrs

220 kV breaker of unit-3 at Idukki

Power

house flashed and bus differential

protection

acted. All Generators (6Nos.) along

with all

220 kV feeders tripped during the

incident.

1. KSEB to reduce sensitivity of REF

protection appropriately at Idukki PH.

2. KSEB to replace/ repair the faulty breaker.

3. KSEB to check the PLCC equipment at New

Pallam and inform the remedial measures taken

to PCSC forum.

KSEB

Annexure-III

Page 12 of 24


400kV

Udumalpet-

Palakad line-

1& 400

Udumalpet-

Arasur line-2

09-02-2015

at 9:50hrs

PLCC of Udumalpet-Arasur-2 mal-

operated

• PGCIL to furnish remedial measures taken.

• PGCIL to properly tune PLCC panels.

PGCIL Mail received on 25-11-2015:

The issue was referred to BPL and OEM suggested to upgrade the

panels with design modifications. LOA has been placed on BPL for

the same. Work is expected to be completed by Nov'15 end.

Pending


HVDC pole-

1&2

at Gazuwaka

and 400kV

Jeypore

Gajuwaka

line -1

14-03-2015

at

17:12 hrs

HVDC Pole-1 at Gazuwaka tripped

due to

tripping of filter banks and Pole-2

tripped due to operation of

differential protection.

400kV Jeypore-Gazuwaka line-1

tripped on over-voltage from

Gazuwaka end.

PGCIL (SR-I) to furnish the reasons for

Converter Transformer differential protection

operation for Pole-2 along with the remedial

measures taken.

PGCIL Reply received during 46th PCSC meeting:

Operation is in-order as per OEM manual (ABB HVDC)

Pending

PGCIL34/I/7 HVDC

BHADRAV

ATHI POLE

2

18-07-2014 As reported pole-2 tripped due on

5th harmonic alarm.

1. Complete analysis of the faults and

rectification/remedial action taken to avert

similar occurrence in the HVDC Back to Back

station shall be submitted.

2. The PCSC forum recommended PGCIL,

SRTS-I take up the issue with WRTS to submit

the report as per IEGC guidelines.

3. SRLDC is also requested to send a letter to

WRLDC to submit the reports to SR also.

4. Based on the SRTS/SRLDC

correspondences, SRPC would take it up with

WR and PGCIL if the issue is not getting

resolved.


Being pursued with POWERGRID, WR-1

Pending

Pending42/II/7 Yet to be informedPGCILPGCIL (SR-II) to submit the report of M/s

ABB’s on preventing supply card failures.

HVDC pole-1 got tripped due to

failure

of 4 no. power supply card. HVDC

pole-2 tripped on DC low voltage

trip.

400kV Jeypore-Gazuwaka line-

1&2

tripped due to operation of Over

voltage

protection at Gazuwaka end.

23-02-2015

at

13:34 hrs

Tripping of

400kV

Jeypore-

Gazuwaka

line-

1&2 and

tripping of

HVDC back

to back pole-

1&2 at

Gazuwaka

Annexure-III

Page 13 of 24


HVDC

Bhadravathi

Pole-1

18-03-2015

at

13:55 hrs

Pole tripped due to failure of

auxiliary supply

PGCIL (SR-I) to submit the compliance report

on PSAG-11 recommendations to PCSC

forum.


Tertiary Transformer charged and auxiliary power for HVDC is being

availed from tertiary widings of ICT.

Pending

Annexure-III

Page 14 of 24

44/I/3

(GD)

765 kV

Raichur-

Sholapur line

1 &

2 tripped

24-05-2015

at 19:19 hrs

Tripped on Overload. 1. PGCIL to provide the status of healthiness of

SPS contact logic in SRLDC’s SCADA.

2. PGCIL to furnish the details of the

implemented SPS-7 scheme including logic

diagram to PCSC forum.

PGCIL Yet to be informed Pending

43/II/2 Multiple

tripping

at 400/230kV

Hosur

substation

of Powergrid

26-03-2015

at 15:40 hrs

230kV Bus-2 at Hosur (PG) got

tripped as spurious initiation got

extended to LBB relay of 230kV

Hosur-Hosur(PG) line at

Hosur(PG) end due to shorting of

contacts in lockout relay.

400/230kV ICT-2, ICT-3, 230kV

Hosur-Vinnamangalam,

230kV Hosur(PG)-Hosur which

were connected to Bus-2 got

tripped along with bus coupler

breaker

PGCIL (SR-II) to check the possibility of

providing re-trip feature in LBB relay.

PGCIL Mail received on 02-09-2015:

The scheme was tested thoroughly found normal.

Pending

PendingYet to be informedPGCILPGCIL (SR-I) to check healthiness of PLCC

panels at Hyderabad SS, and repair/ replace

them, if necessary.

400kV Ramagundam-Hyderabad

line-3 at

ramagundam end only due to DT

receive.

400kV Hyderabad-Malkaram line-

1

tripped at Hyderbad end only and

was

holding from Malkaram end.

400kV Bus-1 at Hyderabad due to

operation of bus

bar protection.

23-04-2015

at

15:11 hrs

Tripping of

400kV

Ramagundam-

Hyderabad

line-3,

400kV

Hyderabad-

Malkaram

line-1 and

400kV Bus-1

at Hyderabad

44/II/4

Multiple

tripping at

Vemagiri

substation of

APTRANSC

O

44/II/6 PendingYet to be informedPGCIL1. PGCIL (SR-I) to enable Auto reclosure

feature at Vijayawada end.

2. PGCIL (SR-I) to check distance relay

settings for Vijayawada – Vemagiri line 3, and

furnish a compliance report to PCSC forum.

400kV Vemagiri-Vijayawada line-

1&3, 400kV Vemagiri-Goutami

line-2, 400kV Vemagiri-

Konaseema line-2 and 400/220kV

ICT-2 at Vemagiri tripped

during the incident. Triggering

incident

was failure of B-phase L.A in

400kV

Vijayawada-Vemagiri line-1 at

Vemagiri end.

25-04-2015

at 10:04

hrs

Annexure-III

Page 15 of 24

44/II/7 Tripping of

765kV

Kurnool-

Tiruvalam

line-1

and 765kV

Kurnool-

NPS-1

25-04-2015

at

18:10 hrs

REF protection of Line reactor of

Nellore-1&2 and Tiruvalam line-1

maloperated

due to DC earth fault

1. PGCIL (SR-I) to submit the action taken

report on the measures suggested by their

OEM.

2. PGCIL (SR-I) to check for the availability of

Chatter Disable feature in P141 and

configure it appropriately to block operation of

REF protection on DC fluctuations.


44/II/8 Tripping of

400kV

Gooty-NPS

line-2

26-04-2015

at 13:16

hrs


in

line. Lines auto-reclosed at gooty

end

and later tripped due to DT receive

from

NPS end.

PGCIL (SR-I) to coordinate STUB protection

settings with the distance protection time

settings at NPS.



400/220kV

ICT-1 at

Gooty

Substation

03-06-2015

at 12:30 hrs

ICT tripped due to mal-operation

of differential relay

1. PGCIL to follow IS and CEA regulations

while carrying out maintenance work.

2. PGCIL to furnish a report on what caused

the ICT-1 tripping including remedial

measures.


PendingYet to be informedPGCILTo avoid tripping of transmission lines on

transient faults, PGCIL is recommended to

carry out periodic patrolling of lines, and

ensure their proper maintenance by carrying

out jungle/ bushing clearance and trimming of

tree branches within the RoW of transmission

lines as per the SRPC transmission line

patrolling guidelines (available under the menu

item "All Uploads Operation

Miscellaneous Transmission Line Patrolling

Protocol / Guidelines for Southern Region" on

SRPC website).

Lines tripped on transient fault.

Auto reclose was un-successful. SR

&NEW grid separated due to

tripping of 765kV lines

03-05-2015

at 4:13 hrs

Tripping of

765kV

Raichur-

Solapur line-

1&2

45/II/15

Annexure-III

Page 16 of 24

46/II/1 Tripping of

400/220kV

ICT-2 at

Nagarjunsaga

r Station

16-06-2015

at 18:12

hrs& 19:18

hrs

ICT-2 tripped due to mal-operation

of 86B relay due to suspected DC

earth fault.

PGCIL (SR-I) to furnish a detailed report on

ICT-2& Bus II outage at 19.18 hrs on

16.06.2015 along with the remedial measures

taken.


46/II/4 Tripping of

400/220kV

ICT-2 at

Gooty

substation

22-06-2015

at 13:06 hrs

At 220kV Gooty Switching

Station, 220KV Gooty Receiving

Station feeder line side Y-Phase

jumper connected between line

isolator to boom resulting in a

220kV Bus fault. This resulted in

tripping of ICT-2 and 220kV

feeders connected to 220KV BUS-

II

PGCIL (SR-I) to furnish a detailed report as to

what caused LBB operation at 400 kV Gooty

SS along with the remedial measures taken.


Tripping of

HVDC

Talcher-Kolar

Pole-2.

45/II/29

PendingYet to be informedPGCIL1. PGCIL (SR-I) to furnish a report detailing

the sequence of events including the remedial


2. PGCIL (SR-I) to verify and ensure time-

synchronizationof DR& EL with GPS at both

Gooty and NPS.

3. PGCIL (SR-I) to check and resolve,in co-

ordination with APTRANSCO, the professed

Phase-Discrepancy that is found to be

occurring between 400 kV Gooty (PG) SS and

the surrounding 220 kV network of

APTRANSCO in the event of a fault.

Breaker at NPS end tripped on

Direct Trip receipt from NPS end.

After 4 seconds, over voltage

protection operated at NPS end as

observed from EL, and direct trip

was sent to Gooty.

01-07-2015

at 09:59 hrs

Tripping of

400kV Gooty-

NPS line-1

46/II/13


Major Shut Down of HVDC Bi-pole line for replacement of insulators

in Polluted Streched is planned from 07th 11th January-16 scheduled.

PGCILTo avoid tripping due to transient faults,

PGCIL (SR-I) is recommended to carry out

periodic patrolling of lines, and ensure proper

maintenance of transmission lines by carrying

out jungle/ bushing clearance and trimming of

tree branches within the RoW of transmission

lines as per the ‘SRPC transmission line

patrolling guidelines’ (available under the

menu item "All Uploads Operation

Miscellaneous Transmission Line Patrolling

Protocol / Guidelines for Southern Region" on

SRPC website).

DC line fault26-05-2015

at 17.55 hrs

Annexure-III

Page 17 of 24


HVDC

Bhadrawati

Pole-1

05-08-2015

at 10:53 hrs

Main pump-2 of valve cooling got

tripped during dip in 33kV

auxiliary bus

voltage. Valve cooling flow got

reduced

due to tripping of pump and

resulting in

tripping of pole-1

PGCIL (SR-I) to furnish compliance report on

PSAG-11 recommendations without further

delay to PCSC

forum.


765 kV

RAICHUR -

SHOLAPUR

1 and 2

04-09-2015

at

19:25 hrs

Sholapur -1 and 2 Feeder got

tripped at Raichur end on operation

of over current

protection in Main-1 distance relay

and holding from Solapur end on

04.09.2015 at

19:24:42 Hrs

765 KV

RAICHUR –

KURNOOL 2

04-09-2015

at

19:25 hrs

Kurnool -II Feeder got tripped on B-

N fault and holding from Kurnool

end (successfully auto-reclosed at

Kurnool end) subsequently tripped

at other end on operation of OV stg-

1 protection at Raichur end on

04.09.2015 at 19:24 Hrs

49/II/4 Tripping of

400kV Gooty-

NPS line-1

13-10-2015at

10:15 hrs

DT was sent to NPS end of line-1

during opening of Main CB of

Gooty-NPS line-2 at Gooty end.

This resulted in tripping of line-1

at NPS and line was holding from

Gooty. OV protection got operated

at NPS end and resulted in tripping

of line

1. PGCIL (SR-I) to configure time scale

resolution in Event Logger to msec. at Nelllore

PS (NPS) and furnish DR corresponding to

OVR, Stag-I operation at NPS end during the

tripping event.

2. PGCIL (SR-I) to ensure time-sync of DR’s

and EL’s with GPS at Gooty & NPS.


47/II/18 1. PGCIL (SR-I) to check the A/R scheme

implemented through BCU’s at all its GIS/

SAS substations for correct

operation.

2. PGCIL (SR-I) to ensure time-

synchronization of DR & EL of 765 kV

Kurnool SS with GPS.

3. PGCIL (SR-I) to sort out the LEGEND

ISSUE related to tripping of the lines in the

Event Logger of Raichur.

4. PGCIL (SR-I) to check & ensure the

functionality & healthiness of synchronization

facility at Raichur end at

the earliest opportune time.


46/II/22 PendingYet to be informedPGCIL1. PGCIL (SR-I) to obtain from PGCIL (WR-l)

the reasons for DT receipt from Sholapur end

and furnish thesame along with the remedial


2. PGClL (SR-I) to verify the logic

implemented of SPS-1 and SPS-7 for the 76S

kV Raichur - Sholapur link byavailing the line

shutdown at the earliest opportune time.

3. PGCIL (SR-I) to furnishthe details of the

implemented SPS-1 and SPS-7 schemes

including their logicdiagrams to PCSC forum.

28-07-2015

at 11.52.22

hrs.

Separation of

SR-grid and

NEW-grid

Annexure-III

Page 18 of 24


400KV

Coastal-

NTPL line

13-02-2015

at 22:54 hrs

Line tripped B-phase to earth fault

and later tripped on R-Y phase

fault. From Coastal end D.R, Y &

B poles of breaker opened first and

R-pole appears to be opened on

Pole discrepancy.

CEPL to check A/R scheme at their end. CEPL Yet to be informed Pending

41/IV/2 400kV

Tuticorin PS-

NTPL line

09-02-2015

at 03:17 hrs

Y-phase to earth fault had occurred

in line. Line auto reclosed at

Tuticorin PS end and failed to

reclose at NTPL end.

NTPL to check A/R scheme at their end. NTPL Yet to be informed Pending


400kV

Coastal

(CEPL)-

Tuticorin

pooling

station

20-04-2015

at 12:35 hrs

Line tripped at Coastal energen end

only and was holding from

TTRNPS

CEPL to furnish a detailed report on this trip

event to PCSC forum.

CEPL Yet to be informed Pending

46/II/3 Tripping of

400kV

Ramagundam-

Dichipalli

line

21-06-2015

at 03:27 hrs

Line tripped on operation of

overvoltage protection at

Ramagundam end and direct trip

was received at Dichipalli. Over-

voltage operation could not be

established with D.R & E.L

submitted by Ramagundam station.

1. NTPC, Ramagundam to investigate the

reasons for OV alongside checking the drop off-

to- pick-up ratio of the OV relay.

2. The tripping is not as per the grading

adopted for OV, Stage-I protection (Grading is

C2: 110% and 6 sec time delay) at

Ramagundam. NTPC, Ramagundam to check

up the same.

NTPC Yet to be informed Pending


400kV

Vemagiri –

GVK (JPD)

line-2

16-07-2015

at 17:02 hrs


in line. Line auto reclosed at

Vemagiri end and failed to reclose

at GVK end.

GVK to put A/R into service at GVK

Jegurupadu end on 400 kV GVK (Jegurupadu)

– Vemagiri line-2.

GVK Yet to be informed Pending


400 kV

Hassan -

Udupi line-1

05-10-2015

at 13:33

Line tripped due to B-E fault in Z2.

Main 1 relay tripped in Z2. 3 phase

trip operated at Hassan. AR

successful at other end and line

was charging from other end. Then

OV stage 1 picked up in Main2

relay and operated in OV after the

time delay

UPCL to furnish reasons for delayed operation

of distance relay in Zone-1 at their end, and the

remedial measures taken, if any.

UPCL Mail recieved on 19-11-2015 (UPCL):

The fault was of resistive nature, was sensed from Hassan end in Zone-

2 reach. The DR from UPCL indicates resistive high current prior to

operation of Zone-1 in C Phase. This is seen as development of Zero

sequence voltage and current prior to Zone -1 operation.

The operation of single phase Z1 from UPCL end was correct

followed by successful AR operation.

Pending

Others

Annexure-III

Page 19 of 24

36/II/8 400kV

Raichur-

Munirabad

line

07-09-2014 B-phase to earth fault had occurred

in line.

Line auto reclosed at Munirabad

end and failed to reclose at Raichur

end.

KPTCL:

PD (pole discrepancy) time delay would be

changed.

PGCIL /

KPTCL


38/II/5 400kV

Ramagundam-

Hyderabad

line-4

27-10-2014 Line tripped on Bphase

to earth fault.

Line did not auto

reclose at Hyderabad

end due to

PLCCmal-operation.

Planned to replace the PLCC system within a

week's time at both the ends during the

shutdown.

NTPC/

PGCIL

Yet to be informed. Pending

Miscellaneous

39/I/2 Tripping of

400Kv

Ghanapur-

Mamidipally

line

22-12-14

at 10:52 hrs,

24-12-14 at

11:32

hrs,

24-12-14 at

16:16 hrs

Due to PLCC Mal-operation at

HYD S/S end, DT received at

MMPLY end and line got tripped.

PGCIL is requested check up with the

manufacturer to resolve the issue and submit

remedial measures to PCSC forum.

PGCIL/

TSTRANSC

O

Mail received on 26-05-2015 from TSTRANSCO:

On 27-12-2014 PGCIL requested to arrange services of

OEM(Manufacturer)for identifying the problem. TSTRANSCO

arranged the same on 06-01-2015 and the manufacturer testing and

concluded that the problem in not in the newly erected digital

protection coupler at both ends and the issue is related to relay panel

at Ghanapur. [OEM minutes enclosed]

Pending

Annexure-III

Page 20 of 24

40/II/3 Tripping of

400

kV

TALAGUPP

A

– HASSAN

line

01-01-2015

at

13:38 hrs

On account of R-phase to earth

fault, line tripped at Hassan end

due to operation of distance Zone-2

and non-receipt of

carrier. From D.R of Talaguppa

end it is observed that fault had

occurred in Yphase.

1. PGCIL and KPTCL to ascertain the reason

for the phase discrepancy in the relay

operation and take suitable remedial measures.

2. KPTCL to check the PLCC operation at

Talaguppa end and submit the report to the

PCSC forum.

PGCIL/

KPTCL

Mail received on 27-05-2015 (KPTCL) & 29-07-2015:

End to end testing of PLCC has been done and problem in the PLCC

is atttended. Phase

discripancy in the relay operation is to be checked jointly.


Problem is in identification of phases at Talguppa end. To be rectified

by M/s KPTCL.

Pending

41/I/2 Complete

outage at

220kV

Bahoor

Substation of

Pondicherry

(GD-1)

15-02-2015

at 11:20 hrs

Bus fault occurred in 110kV bus at

230/110kV Bahoor substation due

to failure of Y-phase main bus

strain insulator. 220kV lines

connected to Bahoor (viz., Bahoor-

NLC TPS II and Bahoor – Pondy)

tripped from remote end on

operation of B/U protection.

1. PED to investigate the cause of non-

operation of ICT’s protection system

(differential protection, back-up protection)

and review the relay settings suitably.

2. PGCIL to check the settings of distance

relay and back-up relays for correctness of

operation.

PED/PGCIL Mail received on 02-09-2015 and 25-11-2015:

All the relay settings were checked and found ok

Pending

with

PED.

42/II/1 Tripping of

400kV

Coastal-

Tuticorin PS

line

19-02-2015

at

16:37 hrs

Line tripped at Coastal end only

due to suspected PLCC

maloperation

and was holding from

Tuticorin PS end. Running Unit at

Coastal energen also got tripped

during the event.

PLCC end-to-end testing shall be carried out by

CEPL and Tuticorin PS (PGCIL-SR II) by

06.04.2015.

CEPL/

PGCIL(SR-

II)

Mail received on 02-09-2015 and 25-11-2015:

On 11.06.2015 PLCC testing carried out by M/s ABB Engineer. ABB

suspects that the problem is with frequency interference related issue,

and suggested to change to new frequecies.

Pending

with

CEPL

Annexure-III

Page 21 of 24

43/II/12 Multiple

tripping at

400kV

Raichur(PG)

and RTPS of

KPCL

11-04-2015at

18:04 hrs

400kV Raichur(PG)-Gooty line-2,

400kV Raichur TPS-Raichur(PG)

line-1&2, 400kV Raichur-

Mahboobnagar, Unit#5 at RTPS

tripped during the incident

KPCL, KPTCL and PGCIL (SR-I) to furnish

the action taken report on the

recommendations given by PSAG members

held at Raichur on 22-04-2015 and

23-04-2015.

KPCL/KPTC

L/ PGCIL(SR-

I)


Tripping of

Unit 1 at

NCTPS

24-05-2015

at 19:13 hrs

ID Fan trip

Tripping of

Unit 1 at

MEPL

24-05-2015

at 19:13 hrs

Coal Mill tripped

Tripping of

Unit 1 at

Krishnapatna

m

24-05-2015

at 19:17 hrs

Generator Protection operated

Tripping of

Unit-8 at

RTPS

24-05-2015

at 19:19 hrs

Tripped on Overvoltage.

Mail received on 26-05-2015 from TSTRANSCO:

It is found that the main-2 ABB make REL316 type distance relay

was defective and same was replaced with MICOM P444 by

M/s.PGCIL on 23.04-2015. After replacement of main-II, DR can be

extracted from this relay. For EL in to service, some field winding is

pending which is being taken up in this month.

Pending

44/I/3

(GD)

1. All Tripped units, viz., Krishnapatinam,

MEPL, Raichur, NCTPS to submit a detailed

report

on this event including the remedial measures


2. KPCL to check the excitation system of Unit

8 of RTPS, and submit the remedial measures


KPCL/

MEPL/

APGENCO/

TNEB

TANGEDCO vide their mail dated 07.07.2015 informed that as per

the discussion and recommendation of 44th meeting of PCSC held on

28.05.2015, a time delay of 2 Sec had been introduced for the above

tripping for all the ID fans at NCTPS-II.

MEPL vide their mail dated 14.09.2015 informed that they have

implemented 2 seconds delay for under voltage tripping of all Drag

Chain Feeder Conveyors. And this has been done for both the Units.

Pending

with

KPCL,

APGEN

CO

42/II/18 Multiple

tripping at

Raichur

thermal

power station

of

KPCL

09-03-2015

at

06:36 hrs

400kV Raichur TPS-Raichur(PG)

line-

1&2, 400kV Raichur-

Mahboobnagar,

Unit#7 and ICT-2 at RTPS tripped

during the incident. B phase to

earth

fault had occurred in 400kV

Raichur

TPS-Raichur line-1

1. KPCL to review REF setting (DMT or

IDMTL) for unit-7 by first week of April, 2015

and

inform the same to PCSC forum.

2. TSTRANSCO to furnish Mehaboobnagar’s

DR and EL and the reasons for distance relay

operation at their end within a week’s time.

3. PGCIL (SR-I) to rectify the issues relating to

A/R operation, relay reach (Z2), reverse reach

(Z4) and SOTF auxiliary contacts within a

week’s time, and submit the actions taken to

PCSC forum.

KPCL/TSTR

ANSCO/PGC

IL (SR-I)

Annexure-III

Page 22 of 24

Complete

outage of

Krishnapatna

m TPS

47/I/2

(GD)

PendingMEPL vide their mail dated 14.09.2015: informed the following

1. Tan Delta Testing of winding and DGA of Insulating Oil for all

CTs was carried out and normal.

2. Could not find any problem during internal checks hence we are in

touch with ABB for rectification work. Will be done by the end of

15th Oct'15

3. End to end testing of Carrier signals was carried out and found

them healthy.

MEPL/

PGCIL(SR-

I)/ SEL

1. MEPL to ensure healthiness of all CT’s by

carrying out Tan Delta and DGA tests wherever

necessary.

2. MEPL to take suitable action to correct the

operation of tie-CB Bay Control Unit that

caused LBB/ BBP operation.

3. PGCIL (SR-1) to carry out end-to-end

PLCC testing in coordination with MEPL and

ensure that carrier-aided protection on MEPL –

NPS line is in healthy condition.

4. SEL to properly time-coordinate their Over

Current phase and Earth fault relays in

consultation with MEPL.

Y phase CT failure at MEPL led to

tripping of 400kV NPS-MEPL,

400kV SEPL-MEPL line and Unit-

2 at MEPL. Uni-1 was not in

service at the time of tripping

20-05-2015

at 20:38 hrs

Complete

outage of

MEPL power

station

45/I/2

(GD)

Tripping of

220kV Kadra-

Karwar line-

1&2 and

220kV

Kaiga-Kadra

line

47/II/7 PendingYet to be informedKPTCL/

KPCL/

NPCIL

1. KPTCL/ KPCL to see the possibility of

implementing Weak Infeed logic with Echo

feature enabled by Under

Voltage (27) element on Kadra-Karwar lines 1

&2, and implement the same if feasible.

2. NPCIL to time-coordinate Kaiga’s DEFR

settings with (i) Zone-2 settings at Kaiga, and

(ii) primary protections of the lines emanating

from Kadra and Kodasalli.

3. KPCL to ensure time-sync of EL’s, and

healthiness of the Fault Locators at Kadra.

220kV KAdra-Karwar lines-1&2

tripped on earth fault in B-phase in

zone-2.

Kaiga-Kadra line tripped at Kaiga

end only on operation of

directional eath

fault protection.

31-07-2015

at

11:44 hrs

PendingYet to be informedAPGENCO/

PGCIL (SR-

I)

1. APGENCO to furnish to PCSC forum (i) A3-

size SLD of SDSTPS, and (ii) the sequence of

events with time stamp showing the protection

that opened Tie-CB (405) at SDSTPS.

2. APGENCO to review STUB/TEED

protection in all dias at SDSTPS and ensure

that they are configured for instantaneous

operation.

3. APGENCO to properly configure the STATE

of the tripping events so that they get recorded

appropriately like TRIP/ OPERATED in their

corresponding EL.

4. APGENCO to ensure time sync of all DR’s

and EL’s at SDSTPS.

5. PGCIL (SR-I) to provide line differential

protection for 400 kV NPS –Nellore-PG lines 1

& 2.

As per FIR submitted, CT damage

observed in Chitoor-Main bay

(404). Main breakers connected to

bus-1 (401, 404, 407, 410) got

tripped on operation of bus bar

protection. Unit-1 tripped on

operation of MFT. Unit-2 was not

in service

08-09-2015

at 18:20 hrs

Annexure-III

Page 23 of 24


400 kV

Kurnool –

Srisailam line

03-10-2015

at 04:40 hrs

on

Tripped at both ends on Y-Phase to

ground zone-1fault. Attempt for

auto-reclose could not be

established.

TSGENCO/ APTRANSCO to carry-out PLCC

end-to-end testing in co-ordination with

APTRANSCO/ TSGENCO to sort out

reception of signals on 400 kV Kurnool –

Srisailam line.

TSGENCO/

APTRANSC

O



400/220 kV

ICT-2 at

Kurnool

Substation

and 400kV

Kurnool-

Srisailam line

26-10-2015

at 14:31 hrs

400kV Kurnool-Srisailam line -

distance protection zone-2 had

operated at Srisailam end.

However from DR, R-phase to

earth fault and zone-2 start were

observed. Breakers at Kurnool end

tripped on direct trip receive from

Srisailam end.

ICT-2 Main-CB tripped due to

operation of bus bar protection,

and Tie-CB tripped due to DT

receipt from Srisailam

1.TSGENCO in coordination with

APTRANSCO to carry out end-to-end testing

of PLCC channels by 15.12.2015 on 400 kV

Srisailam – Kurnool S/C line and 400 kV

Srisailam – Sattenapalli D/C line.

2. TSGENCO and APTRANSCO to make A/R

functional on 400 kV Srisailam – Kurnool line.

3. TSGENCO to resolve configuration

problems with the newly commissioned relays

at Srisailam LB so that unwarranted DT

sending to remote ends is addressed.

TSGENCO/

APTRANSC

O


Tripping of

220kV Kadra-

Karwar line-

1&2 and

220kV

Kaiga-Kadra

line

47/II/7

PendingYet to be informedNTPL/ CEPL1. NTPL to ensure (i) proper DATE settings,

and (ii) time-sync with GPS for DR and EL at

NTPL.

2. CEPL to furnish remedial measures taken

regarding PLCC channel failure.


in 400kV Coastal NTPL line. Line

autoreclosed

at NTPL end and failed to

reclose at Coatal end. Auto reclose

block was persisting due to PLCC

channel fail. Also running Units-

1&2 at NTPL tripped on operation

of GT

differential protection.

Tripping of

400kV

Coastal-

NTPL line

and running

units

at NTPL

47/II/9 03-08-2015

at

15:43 hrs

PendingYet to be informedKPTCL/

KPCL/

NPCIL

1. KPTCL/ KPCL to see the possibility of

implementing Weak Infeed logic with Echo

feature enabled by Under

Voltage (27) element on Kadra-Karwar lines 1

&2, and implement the same if feasible.

2. NPCIL to time-coordinate Kaiga’s DEFR

settings with (i) Zone-2 settings at Kaiga, and

(ii) primary protections of the lines emanating

from Kadra and Kodasalli.

3. KPCL to ensure time-sync of EL’s, and

healthiness of the Fault Locators at Kadra.

220kV KAdra-Karwar lines-1&2

tripped on earth fault in B-phase in

zone-2.

Kaiga-Kadra line tripped at Kaiga

end only on operation of

directional eath

fault protection.

31-07-2015

at

11:44 hrs

Annexure-III

Page 24 of 24

Sl.No. Element NameOutage

date/time

Revival

date/time

Reason for

OutageSender/ Receiver

Remedial Measures/ Actions

taken

1400 Kv KRISHNAPATNAM -

NELLORE

20-07-

2015/11:27:00

20-07-

2015/12:00:00

BUS -1

TRIPPED :

REASON

AWAITED

APGENCO/

APTRANSCO

APGENCO: BUS-1 was tripped

at Power Grid Sub-

Station(PGCIL), Nellore during

the operation of the Isolators,

which is not pertaining to

APGENCO.

APTRANSCO: Line tripped at

Krishnapatnam end only.Line is

in service from Nellore-AP.

PGCIL (SR-I):

2 220 kV AMBEWADI - PONDA 127-09-

2015/15:53:00

27-09-

2015/16:38:00

DUE TO BUS

DEAD AT

AMBAWADI

STATION

KPTCL/ GOA To-be-discussed

3 220 kV AMBEWADI - PONDA 227-09-

2015/15:53:00

27-09-

2015/18:43:00

DUE TO BUS

DEAD AT

AMBAWADI

STATION

KPTCL/ GOA To-be-discussed

Pending Remedial Measures/ Actions taken

for the Critical Tripping Incidents (as on 14-12-2015)

Annexure-IV

Page 1 of 8

4 400 Kv NCTPS - SVCTM-I05-10-

2015/14:31:00

05-10-

2015/15:44:00

TRIPPED ON R-

PH FAULT

TANGEDCO/

TANTRANSCO

TANTRANSCO: Temporary

fault. AR lockout at both ends.

Feeder normalised at 15:43 hrs. on

05.10.2015.

TANGEDCO:

5 400 Kv VTPS - MALKARAM 112-10-

2015/11:40:00

12-10-

2015/16:01:00

TRIPPED ON B-

PH FAULT

APGENCO/

TSTRANSCOTo-be-discussed

6 400 Kv VTPS - MALKARAM 113-10-

2015/12:55:00B-N FAULT

APGENCO/

TSTRANSCOTo-be-discussed

7 400/220 kV ICT-1 AT BTPS30-10-

2015/21:02:00

30-10-

2015/22:42:00TRIPPED KPCL To-be-discussed

8400 Kv GAJWEL - SHANKARPALLY

1

02-11-

2015/11:33:00

02-11-

2015/11:59:00R-N FAULT TSTRANSCO To-be-discussed

9400 Kv GAJWEL - SHANKARPALLY

1

02-11-

2015/12:22:00

02-11-

2015/14:40:00R - N FAULT TSTRANSCO To-be-discussed

10 400/220 kV ICT-2 AT KAIGA03-11-

2015/08:26:00

03-11-

2015/09:49:00

TRIPPED ON

DIFFERENTIA

L

PROTECTION

KAPS To-be-discussed

11 400/110 kV ICT-3 AT SALEM10-11-

2015/03:49:00

10-11-

2015/05:04:00

DUE TO OVER

FLUX RELAY

ACTED

TANTRANSCO

TANTRANSCO:

Due to raise in 400 KV grid

voltage, Over fluxing relay

operated. The Frequency variation

from 49.90 Hz to 50.09 Hz was

recorded during the tripping of all

ICTs.

Annexure-IV

Page 2 of 8

12 400/230 kV ICT-1 AT SALEM10-11-

2015/03:53:00

10-11-

2015/04:49:00

DUE TO OVER

FLUX RELAY

ACTED

TANTRANSCO

TANTRANSCO:






ICTs.

13 400/230 kV ICT-2 AT SALEM10-11-

2015/03:51:00

10-11-

2015/04:57:00

DUE TO OVER

FLUX RELAY

ACTED

PGCIL (SR-II)/

TANTRANSCO

TANTRANSCO:






ICTs.

PGCIL (SR-II):

14 400/110 kV ICT-4 AT SALEM10-11-

2015/02:29:00

10-11-

2015/07:17:00

TRIPPED DUE

TO OVER

FLUX

TANTRANSCO

TANTRANSCO:






ICTs.

15 400/230 kV ICT-4 AT SALEM11-11-

2015/04:42:00

11-11-

2015/17:58:00

TRIPPED DUE

TO OVER

FLUX

PGCIL (SR-II)/

TANTRANSCO

TANTRANSCO:



operated. Carried out the

maintenance work and the

overfluxing relay was tested and

healthiness was ensured.

PGCIL (SR-II):

Annexure-IV

Page 3 of 8

16 400 kV KAIGA - GUTTUR 213-11-

2015/18:21:00

TRIPPED ON R-

PH FAULTKAPS/ KPTCL

PGCIL-SR2:

Portion of the line in which fault

occured owned and maintained by

M/s KPTCL. May be clarified

from M/s KPTCL

KPTCL:

KAPS:


2015/22:04:00

DISTANCE

PROTECTIONKAPS/ KPTCL To-be-discussed


2015/17:24:00

16-11-

2015/18:28:00Y -N FAULT

TANGEDCO/

TANTRANSCO

TANTRANSCO: Temporary

fault. Feeder normalised at 18:28

hrs. on 16.11.2015.

TANGEDCO:

19 220 kV CHITTOR - THIRUVALEM18-11-

2015/11:20:00

18-11-

2015/16:18:00

BUSBAR

PROTECTION

OPERATED @

CTR END

APTRANSCO/ TNEB

TANTRANSCO:

There was no tripping of 230kV

Thiruvalam – Chitoor feeder on

18.11.2015 at Thiruvalam end.

APTRANSCO:

20400 Kv KRISHNAPATNAM -

CHITTOOR

21-11-

2015/07:18:00CB PROBLEM

APGENCO/

APTRANSCOTo-be-discussed


2015/13:15:00

23-11-

2015/19:39:00

DISTANCE

PROTECTIONKAPS/ KPTCL To-be-discussed

Annexure-IV

Page 4 of 8

22 400 Kv HASSAN - UPCL 223-11-

2015/12:53:00

23-11-

2015/13:14:00

B-PH ZONE-1

DISTANCE

PROTECTION

OPERATED

PGCIL-SR2/ KPTCL/

UPCLTo-be-discussed


2015/15:07:00

27-11-

2015/16:11:00R-G FAULT KAPS / KPTCL To-be-discussed

24 400/220 kV ICT-2 AT BANGALORE27-11-

2015/18:47:00

27-11-

2015/19:26:00

BUS BAR

PROTECTION

ACTED

PGCIL (SR-II) To-be-discussed

25 400/230 kV ICT-3 AT UDUMALPET27-11-

2015/11:25:00

27-11-

2015/11:34:00

TRIPPED ON

MAL

OPERATION


26 400/230 kV ICT-3 AT UDUMALPET27-11-

2015/17:25:00

27-11-

2015/18:38:00

RELAY

MALOPERATI

ON


27 400 Kv ALM - SVCTM-II27-11-

2015/15:40:00

27-11-

2015/16:37:00C -G FAULT TANTRANSCO

TANTRANSCO: 400kV

S.V.Chatram - Alamathy -1 feeder

'C' phase jumper got cut at

Loc.No.178 from Alamathy end

and created temporary fault with

400kV S.V.Chatram - Alamathy -

2 feeder 'A' phase jumper. Both

feeders runs on the same tower.

PUTT Trip and AR successful at

S.V.Chatram end. AR lockout at

Alamathy end.

28 220 kV KANIAMPET - KADAKOLA27-11-

2015/09:55:00

TRIPPED ON

DISTANCE

PROTN

KSEB / KPTCL To-be-discussed

Annexure-IV

Page 5 of 8

29 400 Kv ALM - SVCTM-I27-11-

2015/15:40:00

SWITCH ON

TRANSIENT

FAULT

TANTRANSCO

TANTRANSCO: AR lockout at

both ends. C-Phase jumper cut at

LOC.NO.178 from Alamathy SS

end was attended. Feeder

normalised on 10.12.2015 at

12:45hrs.

30 400/220 kV ICT-1 AT BANGALORE27-11-

2015/18:47:00

27-11-

2015/19:15:00

BUS BAR

PROTECTION

ACTED



2015/14:09:00

28-11-

2015/16:20:00B-N FAULT KAPS / KPTCL To-be-discussed


2015/01:04:00

TRIPPED ON R-

N FAULTKAPS / KPTCL To-be-discussed


2015/01:04:00

TRIPPED ON R-

N FAULTKAPS / KPTCL To-be-discussed

34400 kV DICHIPALLY -

RAMAGUNDAM

02-12-

2015/02:46:00

02-12-

2015/04:13:00B-N FAULT TSTRANSCO / NTPC To-be-discussed

35400 kV DICHIPALLY -

RAMAGUNDAM

02-12-

2015/12:40:00

TRIPPED ON B-

Y FAULTTSTRANSCO / NTPC To-be-discussed

36400 kV TALAGUPPA -

NEELAMANGALA

03-12-

2015/16:20:00

TRIPPED ON

LINE FAULTKPTCL To-be-discussed


2015/03:54:00

04-12-

2015/04:58:00

TRIPPED ON B-

PH FAULT

TANGEDCO /

TANTRANSCO

TANTRANSCO/TANGEDCO:

Temporary fault. AR lockout at

both ends. No visible fault and

feeder normalised on 04.12.2015

at 04:58 hrs.

TANGEDCO:

Annexure-IV

Page 6 of 8

38 400 Kv HASSAN - UPCL 106-12-

2015/10:40:00

06-12-

2015/10:56:00

TRIPPED ON R-

N FAULTPGCIL (SR-II) / UPCL To-be-discussed

39400 kV NEYVELI TS 2 - NEYVELI

TS2 EXP

06-12-

2015/20:35:00

06-12-

2015/23:03:00DT RECEIVED NLC To-be-discussed

40400 kV NEYVELI TS2- NEYVELI TS-

I

06-12-

2015/23:12:00

07-12-

2015/00:46:00

MALOPERATI

ONNLC To-be-discussed

41 400/220 kV ICT-3 AT TRICHUR06-12-

2015/13:50:00

06-12-

2015/21:38:00

REF

OPERATEDKSEB To-be-discussed

42 400 Kv NPS - TPCIL 210-12-

2015/03:48:00

10-12-

2015/04:56:00

RELAY

MALOPERATI

ON AT TPCIL

END

To-be-discussed

43400 Kv VIJAYAWADA - NELLORE -

AP -

10-12-

2015/10:51:00

10-12-

2015/11:46:00

TRIPPED DUE

TOBACKIP

IMPEDANCE

RELAY ACTED

To-be-discussed

44 400 kV KALPAKKA - VEMAGIRI 210-12-

2015/15:20:00

10-12-

2015/16:20:00

BUS BAR

PROTECTION

OPERATED @

KLPAKA

To-be-discussed

45 400 kV SIMHADRI - KALPAKKA 410-12-

2015/15:20:00

10-12-

2015/16:30:00

BUS BAR

PROTECTION

OPERATED @

KLPAKA

To-be-discussed

46 400/220 kV ICT-2 AT CHITTOOR11-12-

2015/07:12:00

11-12-

2015/16:23:00

BUCHOLZ

RELAY

OPERATION

To-be-discussed

Annexure-IV

Page 7 of 8

47400 kV TRIVENDRUM -

TIRUNELVELI 1

11-12-

2015/04:56:00B-N FAULT To-be-discussed

48400 KV ALAMATHI -

THIRUVALLAM-1

13-12-

2015/22:42:00

Y-PH LA

BLAST @

THVLM END

To-be-discussed

49 400 kV ALAMATHI - VALLUR 213-12-

2015/22:42:00

Y-PH LA

BLAST @

THVLM END

To-be-discussed

Annexure-IV

Page 8 of 8

F. _SRPC /0. 3 (, 15 dated 2.& .11.2015.

TANTRANSCO

ToThe Member Secretary,

I SRPC,Bangalore.

From'I ErJ.Rexline Terese M.EChief Engineer,Protection and Commu nication5B Block, IfIoor,144 Anna salai, TNEB comple ,Chennai -2Lr.No.CE/ P&C/ SEt 01 Chi EPC4j AEE3

Sir,Sub: Elecy - Operation Circle / Tirunelveli - Tripping of 230KV TIPS

Koodankulam feeder - Action taken report - furnished -Reg

230KV TIPS-Koodankulam feeder tripping for the period from October 2013

to November 2015 is listed in the Agenda for 49 h PCSC meeting. In this regard the

following details are furn ished.

1. 7 Nos. tr ipping were due to flashed over disc insulators - (Breakdowns).

2. During rainy season, most of the trippings occurred (28 Nos.) which were dueto heavy rain, thunder and lightning for the period from October to December .

3. 6 Nos. tripping were due to earth wire cut.

4. I I Nos tripping were passing fault (Bird fault).

Earlier the 230kV TIPS- SR Pudur line made LILO at Koodankulam. The

frequent tr ipping of feeder may be due to the deposit ion of fly ash on the insulatorscoming out from TIPS and NTPL for a radial distance of 5 Km. Replacement of the old

insulators and corroded earth wire in and around TIPS area have already beensanctioned and work is in progress. 70% of disc insulators have already been replacedby Composite Polymer insulators . So deposit ion of fly ash problem will be eliminated in

due course.

In order to avoid frequent tr ippings and breakdowns, it is programmed to

replace the corrod ed earth wi re after the monsoon is over.

Chief Engineer/P&C

Annexure-V

SRPC

Highlight

SRPC

Highlight

Report of the Task Force on Power System Analysis Under Contingencies

Page 113

Appendix-9.1 (Page 5/7 of Appendix)

Various types of directional elements may be employed to control operation of ground over current (zero sequence over current) protection response. The most common approach is to employ Phase angle difference between Zero sequence voltage and current, since the relaying signals can easily be derived by summing phase current signals and by summing phase voltage signals from a suitable voltage transformer.

However, this method is not suitable for some applications where transmission lines terminated at different substations, run partially in parallel. In such cases following type of directional control is recommended to be used for the directional earth fault relay.

Relative phase of negative sequence voltage and current

To ensure proper coordination, operating time must be set according to following criteria:

The DEF protection should not operate when the circuit local backup protection of remote end clears a fault in an adjacent circuit i.e DEF should be coordinated with the remote end LBB.

12. POWER SWING BLOCKING FUNCTION While the power-swing protection philosophy is simple, it is often difficult to implement it in a large power system because of the complexity of the system and the different operating conditions that must be studied. There are a number of options one can select in implementing power-swing protection in their system. Designing the power system protection to avoid or preclude cascade tripping is a requirement of modern day power system. Below we list two possible options:

12.1. Block all Zones except Zone-I This application applies a blocking signal to the higher impedance zones of distance relay and allows Zone 1 to trip if the swing enters its operating characteristic. Breaker application is also a consideration when tripping during a power swing. A subset of this application is to block the Zone 2 and higher impedance zones for a preset time (Unblock time delay) and allow a trip if the detection relays do not reset. In this application, if the swing enters Zone 1, a trip is issued, assuming that the swing impedance entering the Zone-1 characteristic is indicative of loss of synchronism. However, a major disadvantage associated with this philosophy is that indiscriminate line tripping can take place, even for recoverable power swings and risk of damage to breaker.

Annexure-VI

Page 1 of 2

Report of the Task Force on Power System Analysis Under Contingencies

Page 114

Appendix-9.1 (Page 6/7 of Appendix)

12.2. Block All Zones and Trip with Out of Step (OOS) Function This application applies a blocking signal to all distance relay zones and order tripping if the power swing is unstable using the OOS function (function built in modern distance relays or as a standalone relay). This application is the recommended approach since a controlled separation of the power system can be achieved at preselected network locations. Tripping after the swing is well past the 180 degree position is the recommended option from CB operation point of view. Normally all relay are having Power swing Un-block timer which unblocks on very slow power swing condition (when impedance locus stays within a zone for a long duration). Typically the Power swing un-blocking time setting is 2sec. However, on detection of a line fault, the relay has to be de-blocked.

12.3. Placement of OOS trip Systems Out of step tripping protection (Standalone relay or built-in function of Main relay) shall be provided on all the selected lines. The locations where it is desired to split the system on out of step condition shall be decided based on system studies. The selection of network locations for placement of OOS systems can best be obtained through transient stability studies covering many possible operating conditions.

Till such studies are carried out and Out-of-Step protection is enabled on all identified lines, it is recommended to continue with the existing practice of Non-Blocking of Zone-I on Power Swing as mentioned under Option-12.1 above. However, it should be remembered that with this practice the line might trip for a recoverable swing and it is not good to breakers.

Committee strongly recommends that required studies must be carried out at the earliest possible time (within a timeframe of one year) to exercise the option-12.2 & 12.3 above.

13. LINE OVERVOLTAGE PROTECTION FOR 400kV LINES: Low set stage (Stage-I) may be set in the range of 110% - 112% (typically 110%) with a time delay of 5 seconds. High set stage (Stage-II) may be set in the range 140% - 150% with a time delay of 100milliseconds.

FOR 765kV LINES: Low set stage (Stage-I) may be set in the range of 106% - 109% (typically 108%) with a time delay of 5 seconds. High set stage (Stage-II) may be set in the range 140% - 150% with a time delay of 100milliseconds.

However, for over voltage Stage-I protection, a time grading of 1 to 3 seconds may be provided between overvoltage relays of double circuit lines. Grading on overvoltage tripping for various lines emanating from a station may be considered and same can be achieved using voltage as well as time grading. Longest timed delay should be checked with expected operating time of Over-fluxing relay of the transformer to ensure disconnection of line before tripping of transformer.

It is desirable to have Drop-off to pick-up ratio of overvoltage relay better than 97% (Considering limitation of various manufacturers relay on this aspect).

Annexure-VI

Page 2 of 2

SRPC

Highlight

SRPC

Highlight

SRPC

Highlight

SRPC

Highlight

PRACTICAL INTERLOCK LOGICS TO PREVENT UNDESIRED CIRCUIT BREAKER CLOSING, ISOLATOR OPENING & CHARGING OF BAY

IN SUB STATION USING IEDS

Sanjay U Bhatt, Protection, Automation and Metering Department

Adani Power Ltd, Ahmedabad E-mail: [email protected]

ABSTRACT Un desired charging of a bay / equipment when is ready to charge or immediately after getting isolated, due to accidental closing of circuit breaker or breaker flash over may result in severe undefined damage / loss to equipment / system stability / human loss, as well financial burden due to huge repairing cost and outage period till normalcy.

This paper describes practical interlock logics using IEDs for (1) controlling DC negative source to circuit breaker closing circuit and (2) Auto opening of Isolators after opening of circuit breaker.

KEYWORDS Circuit Breaker closing circuit logic, DC negative source breaking for CB closing, Isolator Auto opening logic, safety interlock for CB and isolator.

1. INTRODUCTION The essential element of a protection & control circuit design is to have inclusion of all engineering aspects for control, protection, monitoring & measurement having considerations for technical & operational limitations and capabilities of equipments, system and switchgear, operation possibilities & flexibilities with safety interlocking.

Fig. 1 is a typical such circuit conventionally used for a Circuit Breaker closing purpose.

Fig 1- Typical Closing circuit of a circuit

Accidental shorting of DC+ve to close CB

Reference- I

Page 1 of 11

The safety interlocking involves design of circuit in a controlled manner, by which ultimately actuates the operating mechanism of relevant circuit breaker / isolators / contactors / solenoids etc. for bridging primary connections to charge or operate the equipment. CASE-I In case of a circuit breaker for closing circuit interlock, the auxiliary supply (DC +ve or Phase) is extended from source to actuating point connection of closing coil of a circuit breaker through various permissive contacts ensuring healthy operating conditions, CB readiness, and absence of any abnormalities. The cables are routed through all relevant location of interlock contacts. DC –ve or Neutral is directly connected to other end of closing coil. A typical circuit is shown at Fig. 1.

The opening of isolator on load is also such kind of operation due to similar reasons indicated above.

CASE-II

In addition to the undue closing of circuit breaker, the undesired energizing of equipment (Transformer, Generator, Line etc.) may also happen in case of breaker flash over (internal or external) , particularly in case of Generator or two charged line from different sources, when going to synchronize or after isolated from grid. This is due to external insulation failure or arcing within breaker chamber, causing out of phase connection of two vector (peak to peak twice magnitude) causing severe oscillation and damage to equipment. The detection of breaker flash over reliably and isolation is still a serious concern especially in case of one and half breaker arrangement. Fig.2 shows a typical bay arrangement for a Generator with possible peak to peak voltage vector from Grid and Generator causing flash over. .

An automatic and comprehensive logic which can detect successful opening of breaker and initiate command to open the outgoing circuit isolator with flexibility of closing operation will be very useful to be secure against such wrong energisation of equipments

Fig 2- Typical One and Half CB arrangement possible breaker flash over due to peak to peak voltage across CB open contacts Breaker

Reference- I

Page 2 of 11

2 A CASE STUDY FOR GENERATOR BREAKER RECLOSING AFTER TRIPPING.

Recently at one of the large power plant the Generator Transformer Bushing of a phase failed which led to tripping of unit on operation of overall differential protection with tripping of both Main & Tie breaker. Due to heavy flash over and burning of insulation & oil, there was heavy fire and hot oil spread in nearby MK box & cable trench. This led to damage of all cables as shown in the pictures. After @10 Minutes the Main breaker got closed due to shorting of cable carrying DC+ve and return for closing. However the tripping command was persisting on operation of lockout relay hence tripping of breaker was taking place immediately on closing this sequence repeated multiple times and then stopped on blowing of main DC fuse.

Due to very short time closing, opening of B phase HV bushing of GT and residual rolling of turbine, nothing further damaged occurred.

Fig-3, indicates the control cables route for CB closing from switchyard kiosk to Generator Relay Panel and Synchronizer panel located at Main C/R. The cable trench route is passing near GT area where fire took place.

The detailed closing control circuit is shown at Fig-4.

It is therefore must to review the conventional closing circuit scheme for breaker & Isolator and cabling practices.

Fig 3- Showing location of Bay Kiosk, CB, GT and Main C/R with route of control cable.

Reference- I

Page 3 of 11

Due to fire cable damaged and shorted core to complete the closing circuit path for DC Positive return to Circuit Breaker Closing circuit.

Generator Relay Panel interlock for closing circuit

Synchronizing interlock for closing circuit and closing command from Main Control Room

CB cubicle at Switchyard

Control cables in cable trench from Switchyard to Main C/R

Interlocks

Figure-4- A Generator Breaker Closing circuit, event of closing control cable shorted resulting in undesired closing of circuit breaker Reference- I

Page 4 of 11

3. ISSUES WITH CONVENTIONAL CIRCUIT BREAKER CLOSING & ISOLATOR OPEN CIRCUIT.

Please refer case study mentioned earlier, where the breaker closing circuit philosophy used is conventional as described previously. The scheme is simple and being used everywhere.

Pl. refer Fig.1, and case study occurrence, it is seen that extension of DC +ve supply to closing coil terminal is the only deciding factor for closing operation of breaker and also opening sequence of isolator . Any undue extension of DC+ve to operating coil may lead to undesired operation of equipment. The undue extension of DC+ve to closing circuit/isolator opening circuit may happen due to (1) shorting of control cable carrying DC+ve and return path after permissive and command towards CB/Isolator, and (2) Simultaneous grounding of DC+ve system and terminal connected to CB closing / Isolator Open circuit. The sample case for CB are mentioned in following sections which will also apply to Isolator open circuit with due modifications.

4. SOLUTION TO BREAKER CLOSING DUE TO UNDESIRED SHORTING OF DC+VE.

The mishap due to above indicated DC+ve shorting can be avoided by breaking DC-ve immediately after closing CB and the same can be made through just before closing CB, command through SCADA/IED.

The simple solution is to switch OFF the closing supply immediately after closing CB and make ON when required to close. The same can be made by breaking DC +ve as well with the method described here. However this may involve addition of circuits and contacts for +ve at DC source also, with simultaneous operation of contacts on both sides, adding more complexity and online monitoring of closing circuit also is not possible. So for our purpose DC-ve breaking scheme is sufficient.

.

Existing Closing Circuit

Close Guard I/P

Fig. 5a- Closing circuit DC Negative breaking with CMR operated from Logical operation of IED / circuit. CMR placed at Breaker MK box.

Fig. 5b- Closing circuit DC Negative breaking with Output of IED / Logical circuit scheme placed at Control panel

Digital / Analogue Interlock I/O

Digital / Analogue Interlock I/O

Reference- I

Page 5 of 11

Fig. 5a and 5b above indicate the methods of breaking DC-ve using logical operation performed from numerical IEDs or such circuit from conventional relay, contactor, timers etc.

A simple way of breaking DC-ve is to route it from Master trip relay contacts where DC+ve for closing permissive is also routed.

However in case of manual opening or isolation Master Trip relay may not operate or can be reset after tripping for further interlocks and operations in a Generating Station. So it is also not covering complete risk.

In method 5a the CMR (Contact Multiplier Relay) placed in CB MK box is used to isolate the DC –ve. The CMR is operated by a separate DC/AC source from IED/ Logical device. As shown the CMR energizing supply is also wired from two separate contacts from IED at C&R panel. This will ensure complete secured operation of CMR even in case of the cable damage for CMR.

In method 5b the DC-ve is routed through contacts of IEDs/Device placed at Kiosk in Switchyard interfaced with SCADA.

Method 5a is the most appropriate one for all cases due to secured operation of CMR placed very near to CB closing circuit in MK box.

The CMR method should be used where there is no S/Y Kiosk near to CB and C&R panels are located at Main C/R directly connected with CB for control.

All above method should ensure secure operation with flexibility to operator and monitoring feedback. It should also supervise the shorting of cable or undue extension of DC+ve in closing circuit by guarding method.

5. LOGIC FOR BREAKING DC-VE USING IEDs & SCADA.

A practical logic using IEDs and SCADA interface implemented at the power station where the undesired closing of Generator Breaker happened as referred in case study is shown here at Fig. 6a and 6b.

Explanation of the logic:

Please refer Fig 6a, where a concept circuit is shown for placing of IED /CMR contact in the Negative terminal of closing coil (CC). The Guard input from DC+ve circuit is connected before CB auxiliary switch contact which is closed when breaker is OPEN or immediately after closing contact circuit. The guard input turns in high state when Close command is extended or any undue positive is extended in close circuit.

Please refer Fig 6b, the main logic part which can be built in IED (Relay/Bay Control Unit BCU / RTU having required logical blocks with IEC61850 accepting GOOSE signal and hard wired Binary I/O signal from scheme wiring and interfacing with local SCADA. This is generally available now with all IEDs installed in a switchyard.

The logic uses RS Flip Flop block having reset priority for latching output OPEN / CLOSE. The Flip Flop get reset and breaking DC-ve when

Circuit Breaker is closed successfully.

Lock out / Master trip relay operated.

Circuit Breaker Pole Discrepancy Relay (PDR) operated.

Circuit Breaker closeing permissive interlock NOT OK.

Negative Bypass command from Switchyard SCADA is given for Manual Bypass purpose.

All above condition will cause Flip Flop to reset and opening of contact to break DC-ve.

Reference- I

Page 6 of 11

52b

CC

Various external interlocks / commands

Breaker MK / Control Box

IED/ CMR Contact

DC ‐ve

DC +ve

CB CLOSE (Except Line Bay)

CB-PDR Operated

Lock out relay Operated

RESET

SET

OUT

+ve Guard input High

‘CLOSE circuit through command’ (Pulse) from OWS

RS Flip-flop

IED Contacts to

operate CMR or to

DC‐ve circuit of CB

as per scheme

adopted.

Guard BI of BCU / IED

200 ms

NOTE: The logic can be built in IED (Relay/Bay Control Unit BCU / RTU having required logical blocks with

IEC61850 accepting GOOSE signal and hard wired Binary I/O signal from scheme wiring and interfacing with local SCADA. This is generally available now with all IEDs installed in a switchyard.

Necessary wiring / GOOSE configuration should be worked out for I/O as per logic. ‘The Close circuit through command’ from OWS (Operator Work Station of SCADA) to extend DC-ve for

manual close should be initiated before closing of breaker so that –ve circuit to closing coil will be extended. In case of any unwanted DC +ve extension in closing circuit will be monitored by Guard circuit and will not

allow the flip flop to set to extend DC –ve to closing coil. Which is monitored in SCADA also. The Guard timing is considered as 200 mS allowing closing of breaker normally. The above circuit can also be used for isolator control circuit with modification in input logic and other

interlocks.

Manual Reset (Pulse) from OWS

CB closing permissive OK

Interlock status feedback to SCADA / OWS

Fig 6b - Logic for DC-ve breaking for Circuit Breaker Closing circuit

Fig-6a- Concept Circuit for Breaker Closing circuit

Breaker Aux. contact

Reference- I

Page 7 of 11

The Flip Flop will be set to drive BO to extend DC-ve under following condition.

Though manual command from OWS (SCADA) when it is really required to close breaker, if the DC Guard input is NOT High more than 200 mSec.

Immediately after closing of CB the Flip Flop will get reset breaking DC-ve till a manual intervention is made which should be done just before closing the breaker. In case of line after closing of breaker to allow Auto Reclosure operation DC-ve is not being broken, however except in case of three phase tripping.

Further it is also important to have wire cores for DC +ve source of closing circuit going to external wiring and return from CB MK should be in different cable and not in same cable.

Above logic has been implemented and proven well working taking care for all possible abnormalities. The same can also be used to take care for undue opening of Isolator with some modification of logic such as the phase and neutral (OR DC +ve and –ve) will be extended simultaneous when any open command generated from valid open sequence and other interlocks.

Snap of logic and control built in SCADA database is mentioned as under for a Generator Circuit Breaker.

Reference- I

Page 8 of 11

6. LOGIC FOR AUTOMATIC OPENING

OF ISOLATOR AFTER TRIPPING OF CIRCUIT BREAKER.

It is well known that an Isolator is OFF Load and Circuit Breaker is ON Load circuit breaking equipments. Opening of an Isolator on load will lead to a severe damage to equipment and human also. Due to this reason to avoid accidental opening of isolator a routine practice is being adopted for an isolator, to switch OFF isolator Driving Motor supply after closing electrically or manually. However in case of ABCB earlier, due to risk of getting closing of circuit Breaker on low air pressure automatic opening of isolators on immediate opening of CB was used using hard wired CB status based logic. Now days all isolators are remotely operated from SCADA and also with concept of unmanned S/S the Isolators are kept ready to operate with all auxiliary sources in service. With this arrangement it is must for isolator to have DC-ve and also automatic opening of isolator breaking logic schemes.

Please refer Section 2 Case-II and case study of occurrence, the reclosing of Circuit Breaker due to any reason or flash over subsequent to opening of breaker or before synchronizing will defiantly damage the equipment connected. In the referred case, the immediate opening of circuit (Line) isolator on opening of CB would have saved the impact on Transformer and Generator, if so designed in the scheme. The manual opening of isolator immediately after tripping of CB is also not expected due to human action.

The logic implemented at Sub station referred earlier is mentioned at Fig 7 & 8 using Bay Control Unit, GOOSE signal for status / Analogue signal over IEC 61850.

The output of Auto OPEN Logic is configured with same output of the existing logic for OOPEN sequence of isolator taking status and feedback as per logic.

Explanation of the logic:

Please refer Fig. 8, the Auto Open sequence will be initiated after proposed time delay of 5 sec, when (i) Under current relay picks up AND (ii) Main Breaker is not CLOSED AND (iii) TIE Breaker is not CLOSED AND (iv) Isolator closed status is high. For secure operation the interlock of load current and breaker status has been incorporated. The Auto open sequence will be automatically latched for next operation when (1) Under current relay resets OR (ii) Main Breaker CLOSED OR (iii) Tie Breaker CLOSED, after a proposed time delay of 5 sec. The next closing sequence will be initiated by Manual command from SCADA OWS for SET command to the RS Flip-Flop, and when it is set will allow manual CLOSE sequence to operate making the operation more secure and enhancing the CLOSE logic also.

Again after opening of breaker and sensing of under-current will allow Auto opening of isolator as per logic.

The implemented logic screen snap is also indicated at Fig-9.

Existing CLOSE sequence

Existing OPEN sequence

AUTO OPEN Logic

BCU Output for Isolator OPEN & CLOSE

SCADA interface

Reference- I

Page 9 of 11

Fig 8 - Logic for Auto open of Isolator after opening of Circuit Breaker

&

I<1 Under Current

Main Breaker CLOSE

TIE Breaker CLOSE

Isolator CLOSE status

Manual SET

(Pulse) from OWS

Timer OPEN

Command

to Isolator

RESET

OUT

O

R

SET

To Isolator CLOSE logic interlock

to ensure SET condition of Auto

Open sequence

& Existing LOGIC for

Isolator CLOSE command

CLOSEE

Command to

Isolator

T

5 S

NOTE: Manual SET command from OWS SCADA should be SET before Closing of Isolator. The Logic is built in BCU and connected with existing OPEN command of isolator. Manual Set command latch O/P from flip flop is interlocked with Existing Logic for Isolator Closing Required modification & configuration of relevant relay for under current setting and Logic should be worked out. Timing for Auto Open Isolator may be set at 5 second after opening of CB.

Fig 9 – Implemented Logic for Auto open of Isolator after opening of Circuit Breaker

Reference- I

Page 10 of 11

7. CONCLUSION

The described engineering practice should be implemented as a standard scheme for operation of Circuit Breaker and Isolators looking to secure operation of primary switching.

Because numbers of incidences are being occurred on account of damaged cables or DC- grounding or mal-operation even during fault finding or testing of control wiring. The use of latest technology or equipment without reliable operating mechanism is waiting for a disaster always.

Availability of Numerical technological IEDs and GOOSE signals over IEC61850 protocol with SCADA has made the task very easy and secure.

(1) Circuit Breaker Closing circuit should be equipped with DC-ve breaking as near as possible to Closing Coil with Contact Multiplying relay / IED (Relay) contact with secured logic, control and monitoring facility in SCADA.

(2) Isolator OPEN circuit should also be equipped with similar above scheme logic indicated at (1).

(3) Circuit (Line) Isolator should be automatically opened immediately after tripping /Opening of CB/s. The logic should be secured enough to ensure complete OFF Loading of circuit and also with no confliction with CLOSE sequence operation.

(4) The control cables carrying DC-ve from CB / Isolator and to IED/Relay at C&R panel should be in different cable, preferably separate route to avoid any possibility of malfunction of the above discussed circuit itself.

(5) All the input / output and logical status should be configured in event of IED and SCADA for future analysis on event of occurrence.

(6) The new specification for C&R panel and scheme should be included with above said requirements.

REFERENCES:

(1) Various schemes drawing for different substations.

(2) AREVA make application manuals on BCU MICOM C264 /EN/AP/ C30, PACIS Operation Interface for Automation and other IEDs

(3) ABB make application manuals on 670 series IEDs.

AUTHOR:

.

.

.

Sanjay U. Bhatt, working as DGM (Protection) at Adani Power Ltd, Ahmedabad, (Protection Automation & Metering Department), from January 2012.

B.E. (Electrical) -1993 from L.E. College Morvi , Gujarat (India). Worked: In G.S.F.C.-Jamnagar, as Ele. Maintenance Engr. In Govt. Polytechnic, as a lecturer on clearing GPSC. In GSECL as Junior Engineer at Sikka Power station as Electrical Testing & Maintenance engineer and at SLDC during commissioning of SCADA and related system. As Deputy Engineer at GSECL corporate office as Testing engineer.

Reference- I

Page 11 of 11

Application Notes P34x/EN AP/G44

MiCOM P342, P343, P344

Page 129 of 176

For generator applications the undercurrent elements should be measuring current from CTs on the terminal side of the generator. This is because for an internal fault on the generator after the CB has tripped the generator will still be supplying some fault current which will be seen by undercurrent elements measuring current from CTs on the neutral side of the generator. This could thus give false indication of a breaker fail condition.

The voltage dependent overcurrent protection and underimpedance protection used for back-up protection of system faults are usually connected to the neutral side CTs so that the generator is in the zone of protection. These protection functions use the IA, IB, IC current inputs in the P343/4. Therefore, if the IA, IB, IC inputs are connected to neutral side CTs then the IA-2, IB-2, IC-2 inputs should be selected for the undercurrent elements using the setting ‘I< Current Input - IA-1, IB-1, IC-1/IA-2, IB-2, IC-2’.

P2181ENa

DDB #162 : Any Trip (RL3)

DDB #493 : Bfail1 Trip 3ph

DDB #294 : CB Fail Alarm

tbf2

0s

DDB #494 : Bfail2 Trip 3ph

DDB #380 : Ext. Trip 3ph

OR

AND

DDB #631 : IA< Start

DDB #632 : IB< Start

DDB #633 : IC< Start

DDB #635 : IN< Start

DDB #447 : ISEF>1 Trip OR

S

Q

R

G37-0 : Disabled

G37-1 : Enabled

SETTING [4504] :

CB Fail 2 Status

G37-0 : Disabled

G37-1 : Enabled

SETTING [4502] :

CB Fail 1 Status

AND

AND

tbf1

0s

OR

SETTING [4503] :

CB Fail 1 Timer

SETTING [4505] :

CB Fail 2 Timer

AND

S

R

OR

Q

DDB #453, 457 : V< Trip

DDB #469 - 472 : F< Trip

DDB #757 : All Poles Dead

OR

DDB #380 : Ext. Trip 3ph

AND

DDB #634 : ISEF< Start

G68-0 : I< Only

G68-1 : CB Open & I<

G68-2 : Prot Reset & I<

SETTING [4506] :

Volt Prot Reset

G68-0 : I< Only

G68-1 : CB Open & I<

G68-2 : Prot Reset & I<

SETTING [4507] :

Ext Prot Reset

AND

AND

OR

AND

AND

OR

S

R

Q

S

R

Q

DDB #162 : Any Trip (RL3)

DDB #461, 465 : V> Trip

DDB #451, 457 : VN> Trip

DDB #416 : 100% ST EF Trip

DDB #497, 498 : PSlipz Trip

DDB #475, 476 : Power Trip

DDB #495, 496 : SPower Trip

DDB #422, 423 : Field Fail Trip

DDB #429 : V/Hz Trip

DDB #430 - 439 : RTD Trip

DDB #473, 474 : F > Trip

x 2 Stages

x 2 Stages

x 2 Stages

x 4 Stages

x 2 Stages

x 2 Stages

x 2 Stages

x10 Stages

x 2 Stages

x 2 Stages

Figure 52: CB fail logic

2.29 Breaker flashover protection

Prior to generator synchronization, or just following generator tripping, where the protected generator could be slipping with respect to a power system, it is possible to establish at least twice rated phase-neutral voltage across the generator circuit breaker. An even higher voltage might briefly be established just after generator tripping for prime mover failure, where the pre-failure level of excitation might be maintained until AVR action takes place. Whilst generator circuit breakers must be designed to handle such situations, the probability of breaker interrupter breakdown or breakdown of open terminal switch gear insulators is increased and such failures have occurred.

Reference-II

Page 1 of 2

30010641

Highlight

P34x/EN AP/G44 Application Notes

Page 130 of 176

MiCOM P342, P343, P344

This mode of breaker failure is most likely to occur on one phase initially and can be detected by a neutral current measuring element. If the generator is directly connected to

the power system, the second stage of stator earth fault protection (“ΙN>2...”) could be

applied as an instantaneous element by setting the time delay “ΙN>2 TimeDelay” to 0s, to quickly detect the flashover. To prevent loss of co-ordination this stage must be blocked when the circuit breaker is closed. This can be programmed by correct configuration of the programmable scheme logic and can be integrated into the circuit breaker fail logic, as shown in Figure 53.

Where the machine is connected to the system via a step-up transformer a similar scheme can be arranged. The P34x relay standby earth fault protection element can be connected to measure the transformer HV earth fault current to provide the breaker flashover protection, via suitable scheme logic. The machine earth fault protection can be provided by the P34x sensitive earth fault protection element, as shown in Figure 54.

P2182ENa

MiCOMP343

IN

ISEF

DDB 39

L8 52-B

DDB 205

IN>2 Trip

& DDB 168

Extern Trip 3ph

DDB 310

Bfail1 Trip 3ph

R5 CD fail trip DW 100

Scheme logic in PSL

Figure 53: Breaker flashover protection for directly connected machine

P2183ENa

MiCOMP343

IN

ISEF

DDB 39

L8 52-B

DDB 205

IN>2 Trip

& DDB 168

Extern Trip 3ph

DDB 310

Bfail1 Trip 3ph

R5 CD fail trip DW 100

Scheme logic in PSL

Figure 54: Breaker flashover protection for indirectly connected machine

This CT shall

be provided

additionally. This CT is connected to P141realy (GRP-C). This CT signal shall be

extended to P344relay by connectingboth relay terminals in series.

Reference-II

Page 2 of 2

Adaptive Logic for Breaker Flashover Protection of Generator. Sanjay Bhatt

Protection Automation and Metering Group Adani Power Training and Research Institute

Adani Power Limited, Ahmedabad [email protected]

1. ABSTRACT:

Flashover can occur on any breaker in the network where an overvoltage condition is present, but the probability is higher for breakers being used to synchronize two isolated power systems; e.g. on generator breakers, line breaker connecting two separate sources or grids. For Generator/line breaker, the Period is considered as critical in view of withstanding rise in voltage vector appearing across poles of Circuit Breaker and the arc quenching process before generator/line synchronization, or just following generator/line tripping respectively. The circuit breaker for above said applications for must be designed capable of maintaining the sufficient insulation level to withstand the same. The detection of flashover reliably and operating protection to isolate the affected breaker and generator in possible minimum time calls for a logic based on immediate sensing of arc current supported by breaker status to reliably declare a flash. This paper describes the logic adapting the numerical relaying logic blocks with current status different from conventionally used and also described in IEEE guideline for Generator Protection C37.102.

2. KEYWORDS: Breaker Flashover, Generator Protection for GT Breaker flashover, unintended arc across Generator breaker

3. INTRODUCTION:

(I) It is because the vectors of the protected generator and grid vector across circuit breaker poles are slipping with respect to a power system. This will lead to a condition to establish at least twice rated phase-neutral voltage across the generator circuit breaker. Due to the system and machine operation condition it is quite often possible that even higher voltage may be established. This will lead to establishment of arc between two poles of circuit breaker, which may be internal or external, leading to failure of breaker damaging self and also nearby equipments and persons. Further the establishment of arc will also lead to the asynchronous energisation of Generator with grid and create oscillation damaging Generator Transformer / Generator. Detecting the flashover The abnormal rise in voltage just after generator tripping is most likely due to following reasons,

Prime mover failure: which is associated by the excitation level not matching instantly with the lowering of active power, where the pre-failure level of excitation might be maintained until AVR action takes place.

AVR malfunction: this is associated with failure of AVR to discharge energy through discharging resistor at the time of tripping boosted by residual flux.

Reference- III

Page 1 of 7

2 Adaptive Logic for Breaker Flash over protection of Generator.

The peak to peak voltage appearing across circuit breaker is indicated at Fig.1 below.

During the synchronization process, the out-of-phase angle between breaker contacts changes from 0 to 360 degrees continuously. Voltage between breaker contacts reaches its maximum instantaneous value when the angle difference between the voltages is 180 degrees, with a magnitude equal to double the nominal phase-to-ground peak voltage; posing severe stress to the insulation. May also result in out of step and swing.

The flash over thus occurred in most of the cases are of single phase in nature as because of probability of maximum peak to peak voltage at a time is for one phase and very rare may be of two phases depending up on deterioration of insulation and repeated peak across each phase.

(II) Detection of Flash over The detection of arc as a fault is very tricky due to lower magnitude and also resembling the breaker status with selectivity among various normal and abnormal grid behavior and remote fault. The arc current will always reflect as a Zero sequence or Negative sequence current which can be detected typically as under.

Fig 1- Typical One and Half CB arrangement possible breaker flash over due to peak to peak voltage across CB open contacts Breaker

Fig 2a- Typical CT connection to detect breaker arc current as residual current for Generator directly connected to Grid

Fig 2b- Typical CT connection to detect breaker arc current as residual current for Generator connected to Grid through Transformer.

Reference- III

Page 2 of 7


Typically the detection of Neutral over current from Generator or Generator transformer as referred in fig (2a & 2b) with Breaker OPEN status is interpreted as breaker flash over condition, and after certain small time delay tripping is declared out. Alternatively detection of Negative sequence current at Generator Neutral and phase side with Breaker status is also used for detection of breaker flash over condition.

(III) Action: Tripping of associated bus is essential here, because, merely tripping of Generator or excitation will also initiate tripping of Generator breaker and still the breaker is shunted by flash arc current, with the breaker is already in OPEN status, will subsequently cause initiation of LBB and after certain time delay of LBB timer will trip Bus breakers, which is delayed tripping as per LBB setting and initializing scheme.

(IV) Reliability & Selectivity.

(a) Limitation of above logic remains always within the reliability of the breaker status, because defective status of breaker obtained through breaker auxiliary switch many times falsify due to switch and related gearing alignment and contact issues. During the defective status of breaker associated with remote fault or short duration unbalance due to auto reclosing will cause to operate the

logic undesirably causing tripping of Generator and bus also. However use of GT neutral current with interlocking of GTCB may lead to mal-operation when the Breaker contact is defective, which enables the function during normal operation of unit. Further the setting of IN for Flash over detection is kept low enough for effective detection of flash current therefore any earth fault or unbalance in the grid / line may lead to operation of the function. Use of Generator Neutral CT will avoid the possibilities of above mal-operation during grid disturbances. However pure single phase flash may not be reflected at Generator Neutral side because of the zero sequence isolation at generator side for faults on GT side.

(b) In case of Generator connected with one and a half breaker bus arrangement detection of breaker flash over if actual, will not identify the breaker (Main or Tie) which has undergone flash over. Pl. refer fig 1, where it has been indicated that the Generator / Line can be connected either from Main or Tie breaker and therefore the flash over condition may be for either of two breaker. Thus the automatic and reliable detection of the breaker which has undergone the mishap must be identified and output action should be relevant to the identification. It is now obvious that action to isolate the Generator from Grid should be separate for each condition with unique identification. Merely detecting breaker flash over condition from the breaker status (composite may be of Main and Tie) and neutral current from Generator Transformer or Generator, with action for Tripping of Bus bar and Class A tripping for Generator is not sufficient as well not truly as per requirement defeating the aim for Breaker flash over protection intended so.

Above limitation for reliability and selectivity will place a threat to undesired tripping, delayed tripping or stability aspects too.

& Breaker OPEN Status

IN>

I2p>

I2n>

TRIP Excitation& BUS

& Breaker OPEN Status

TRIP Excitation& BUS

Fig 3- conventional logic to detect breaker flash over

Time

Time

Reference- III

Page 3 of 7


(V) Solution: Addressing above limitations with feasible solution is possible with following considerations. As earlier discussed Broadly two criteria are required to detect breaker flash over (i) Breaker OPEN status (ii) sensing of Neutral current at GT or Negative sequence current at Generator terminal and (iii) third one essential for One and Half breaker Bus arrangement is, identifying the affected breaker. The output actions are then decided and forwarded with suitable circuit schemes. (a) Detection of Breaker Status.

Indirect assessment of breaker pole status can only be done by detecting flow of current through all three phases simultaneously registering a status in logic block and removing also the register status as low, i.e. using flipflop block triggered by current threshold. Also as per IEEE GUIDE FOR AC GENERATOR PROTECTION: Std C37.102-1006, 4.7.1 Open generator breaker flashover protection: ‘Generator breaker flashover may also be detected by breaker pole disagreement relaying. This relay monitors the three-phase currents flowing through the breaker and senses whether any phase is below a certain low threshold level (indicating an open breaker pole) at the same time that any other phase is above a substantially higher threshold level (indicating a closed or flashed-over pole).’ Logic using FlipFlop :

Above logic criteria are indicated at Fig 4. The flow of current through circuit breaker at HV side of Generator Transformer is considered as Phase current (Iph) and IN as GT neutral current. The OPEN status is detected when all three phases detect current below 2% (or practically as low possible setting available in relay which can be detected reliably. The OPEN status implies isolated

condition of Generator from grid and SET the FlipFlop. The output of FlipFlop makes input of AND gate high arming for Breaker flashover protection active. On detection of neutral current in GT or Negative sequence current at Generator will operate breaker flash over protection trip output. The normal operation of Generator can be considered as (i) Before & During synchronizing (ii) After Synchronizing and (iii) Grid fault when Generator is normal in service (iv) After isolating from grid. (i) Before & during synchronizing there

is no current flow and hence FlipFlop O/P is High. There will not be Iph and IN hence keeping the logic O/P as low.

(ii) Immediate after synchronizing there will be Iph >5% (or to be set as possible initial loading normally) resetting the FlipFlop after 200 mS.

(iii) Machine running normally will also prevail condition (ii) above.

(iv) After tripping of machine there will be Iph<2% as set above will immediately put function in service.

Fig 4- Breaker open status Detection logic based on current threshold using SR FlipFlop

SR Flip Flop

S

R

O

IPh <2% 3 Phase

IPh > 5% 3 Phase

T = 200 mS

& IN> 10 to 20%

T = 100 mS

TRIP ALL / BUS TRIP

Iph= Phase current, IN = GT Neutral current

For 1-1/2 Breaker bus, separate logic for Main and Tie breaker path current.

Reference- III

Page 4 of 7


Logic using AND –OR blocks : Some of the basic versions of IEDs do not have the Flip Flop logical blocks, for which following logic using basic AND – OR and Timer blocks can be used as indicated at Fig-5 here under.

The lower current threshold for any one phase is monitored for OPEN status, this implies for resetting only when all three phases have current more than 2% i.e. all poles closed. The drop out timer is intended for keeping function armed for 200 mS. after synchronizing during which practically picking up of load by Generator more than 5%.

All four conditions mentioned in earlier paragraph for Generator are addressed here

also detecting reliably the breaker flash over condition.

The IN setting for 10 to 20% is intended for detecting lower arc current as low as 10% keeping in consideration normal maximum unbalance current.

The delay in output is chosen as 100 mS for stability and reliability purpose considering normal breaker closing time and inherent difference in closing of individual pole and also initial unbalance current owing to measurement and magnetizing effect for lower magnitude.

OUTPUT Action:-

The output action of the protection must isolate the Generator from grid and also removal of excitation to Generator. The conventionally action for a LBB protection is similar to the required one for Breaker Flashover condition.

The difference here is the detection at a lower magnitude of current without any trip initiation and also operating time is much less than typical LBB time of 200 to 250 mS.

Fig 5- Breaker open status Detection logic based on current threshold using AND-OR blocks.

Iph= Phase current, IN = GT Neutral current

For 1-1/2 Breaker bus, separate logic for Main and Tie breaker path current

&

IN> 10 to 20%

PU Timer = 100 mS

TRIP ALL (Class A & BUS TRIP

IPh-B <2%

IPh-c <2%

OR

IPh-A >5%

IPh-B >5%

IPh-C >5%

OR

DO Timer 200 mS

Annunciation & SOE in SCADA / DCS

IPh-A <2%

LBB Initiation

OR

TRIP ALL (Class A & BUS TRIP

Breaker Flash over O/P

I>20% Timer 250 mS

&

Fig 6: Output action for LBB and Breaker flash over protection

Reference- III

Page 5 of 7


(V) Solution

(b) Selectivity of Breaker Flash over for One and Half Breaker system arrangement of Bus.

The One and half breaker arrangement is mainly having advantage of redundant connectivity for feeders. As shown in fig-7, the Phase current used for Breaker flash over can be referred from Main or Tie breaker CTs. The breaker flash over may occur for Main or Tie breaker during synchronizing or after isolation from Grid. So both the paths must be

separately detected for flash arc current i.e. Main and Tie breaker. The action required after detection of flashover are different as detailed below.

(1) MAIN Breaker flash over Tripping of Generator in Class-A

to trip excitation immediately and stop prime mover for any rise in voltage due to residual magnetism.

Open all bus breaker to isolate the affected breaker from grid.

(2) TIE Breaker flash over. Tripping of Generator in Class-A

to trip excitation immediately and stop prime mover for any rise in voltage due to residual magnetism.

Trip Main breaker of Line side. Send Direct Trip Transfer signal to

isolate source from remote end.

The logic described for Current detection as Iph-A-B-C in earlier paragraphs equally used separately for Main and Tie breaker. The CT input for Main and Tie paths are indicated in fig-7.

Two separate logics should be built as conveniently in bay IEDs like, BCU or back up relay with separate set of actions as described above.

Please note that the neutral current here and elsewhere in document is indicated from GT neutral, whereas can also be used as Negative sequence current of Generator Phase connection also.

The setting values shown here are from experienced values for a 660 MW Generator, however can be considered on typical machine behavior and normal operation.

TIE

Fig 7: Current detection for selectivity for One and Half Breaker arrangement for breaker flash over protection.

Line Feeder

Y

D

Main-Line

Main-Gen

G

Iph-TIE

Iph-MAIN G

IN

Reference- III

Page 6 of 7


(VI) CONCLUSION;

The breaker flash over phenomena is a very typical one to detect reliably and opt for action like isolation of bus and feeder at minimum possible time. Typical logic are offered by various manufacturer as indicated earlier, however use of reliable detection and output action is a part of scheme designing and adaption of philosophy.

Reliable detection and comprehensive logic is now very easy to be built in IEDs having numerous logical blocks, I/O configuration and even use of GOOSE signals for interlocking.

Breaker flash over protection must be used as a critical protection function particularly the locations like sea shore based or saline atmosphere surrounded installations, where chances of external flash over is higher. The lower flash arc current may also cause severe oscillation and asynchronous energisation may lead to damage to TG set or transformer.

Careful design should be carried out to handle flash over detection and isolation for one and Half breaker arrangement.

(VII) REFERENCES a. IEEE Guide for AC Generator

Protection: Std C37.102-1006, 4.7.1

b. Guide for Ac Generator Protection, ANSI/IEEEC 37.102-1995.

c. Application manual AREVA Micom P34x relay.

(VIII) Acknowledgement:

Author takes opportunity to express gratitude and special thanks to HOD of P&M Group of Adani Power Ltd., his guideline & knowledge, Adani Power Training & Research Institute, APL management for granting permission and inspiration to think and present this paper.

(IX) Author:

Sanjay U. Bhatt, working as DGM (Protection) at Adani Power Ltd, Ahmedabad, (Protection Automation & Metering Department), from January 2012.

B.E. (Electrical) -1993 from L.E. College Morvi , Gujarat (India).

Worked: o In G.S.F.C.-Jamnagar, as Ele.

Maintenance Engr. o In Govt. Polytechnic, as a lecturer on

clearing GPSC. o In GSECL, Gujarat as Junior Engineer

at Sikka Power station as Electrical Testing & Maintenance engineer and at SLDC during commissioning of SCADA and related system.

o As Deputy Engineer at GSECL corporate office as Testing engineer.

Reference- III

Page 7 of 7

· non-operation and plcc mal- operation. the trippings due to gds, gis, auto-reclosure failure/...

Documents