drs_setting calculation reference 1

7/28/2019 DRS_setting Calculation Reference 1

1/29

SETTING CALCULATIONNUMERICAL PROTECTION SYSTEM

2 X 50 MW MALANA-II HYDROELECTRIC PROJECT

CLIENT :

ABIR INFRASTRUCTURE PVT. LTD.

MALANA-II HYDRO ELECTRIC PROJECT

Drawn: DD.MM.YYYY SS

Checked: DD.MM.YYYY SS

Approved: DD.MM.YYYY SKV

Rev. Modification Date Check Date Appd

PROJECT NO: C. 290PLANT: 2 X 50 MW MALANA-II HYDRO ELECTRIC PROJECT

= FU PLN

= LO

CUSTOMER No:

SETTINGCALCULATION NUMERICALPROTECTION SYSTEM

Internal Drawing Number:

2 783001Page 1 of 29

Rev.

0

THIS DOCUMENT IS THE PROPERTY OF VA TECH HYDRO AND MUST NEITHER BE COPEID NOR USED IN ANY OTHER WAY WIHTOUT THE WRITTENCONSENT OF VA TECH HYDRO NEITHER IT IS TO BE HANDED OVER, NOR IN OTHER WAY COMMUNICATED TO A THIRD PARTY. INFRINGMENT WILLLEAD TO PROSECUTION


2/29



MALANA-II HEP Page 2 of 29

SETTING CALCULATIONFOR DIGITAL PROTECTION SYSTEM

Table of Contents

1. GENERAL ............................................................................................................................3

2. TECHNICAL DATA ..............................................................................................................4

3. GENERATOR, TRANSFORMER AND UNIT AUXILIARY TRANSFORMER PROTECTION...6

A) GENERATOR DIFFERENTIAL PROTECTION 87G.............................................................. 6B) GENERATOR UNDEREXCITATION PROTECTION 40G....................................................... 7C) GENERATOR NEGATIVE PHASE SEQUENCE PROTECTION 46G ........................................ 8D) GENERATOR OVERVOLTAGE PROTECTION 59................................................................ 9E) GENERATOR UNDERVOLTAGE PROTECTION 27G ......................................................... 10F) GENERATOR OVER/UNDERFREQUENCY PROTECTION 81O/U ........................................ 10G) GENERATOR STATOR EARTH FAULT PROTECTION 64G1 .............................................. 11H) GENERATOR STATOR EARTH FAULT PROTECTION 64G2 .............................................. 11I) ROTOR EARTH FAULT PROTECTION 64R ..................................................................... 12J) GENERATOR REVERSE POWER PROTECTION 32G........................................................ 13K) VOLTAGE SUPERVISION FUNCTION 60G, 60M AND 60A ............................................... 13L) GENERATOR UNDERIMPEDANCE PROTECTION 21G ..................................................... 14M) DEAD MACHINE 27/51V .............................................................................................. 15N) UNIT DIFFERENTIAL PROTECTION 87GT ..................................................................... 16O) RESTRICTED EARTH FAULT PROTECTION 64REF ......................................................... 17P) RESTRICTED EARTH FAULT PROTECTION 64REF- DISCRETE RELAY ............................. 19

Q) OVERFLUXING PROTECTION 99G ................................................................................ 21R) UAT DIFFERENTIAL PROTECTION 87UAT..................................................................... 21S) UAT OVERCURRENT PROTECTION 50U/51U................................................................. 22

4. DISTANCE PROTECTION .................................................................................................23


3/29




1.GENERAL

This document provides information about the various protective schemes for the unit transformerprotection, generator protection and UAT. The document lists the particular protective functions as howthey overlap and complement each other for back-up and outlines the philosophy about the selection of the protection setting values.Please note that the generator and transformer characteristics and capability curves and data arecontained in separate documents.

Also the documentation with detailed descriptions of the various protection systems are provided inseparate relay documents.

Note:The calculated relay settings are based on different data sheets available during the workout (e.g.generator data sheet, CB data, and single line diagram) of the document. In case of any equipmentmodification or change of various electrical characteristics this document has to be revised. Thereforeall the settings have to be checked and revised during the commissioning on site.

Generally the calculation of the settings is done according to our best knowledge and conscience. Sowe cant accept any responsibility for errors included in the document. Further we are not liable for anyincident or damage resulting from the content of this setting calculation.

Some protection settings (e.g. frequency, voltage) have to be checked and approved also from thepower distribution owner.


4/29




2. TECHNICAL DATA

Generator:

GENERATOR OUTPUT= Sn 55560.00 kVA RATED VOLTAGE= Un 11 kVPOWER FACTOR p.f. 0.9RATED CURRENT In 2915.9 A RATED FREQUENCY fn 50 HzSYNCRONOUS REACTANCE Xd 93.30%TRANSIENT REACTANCE (STAURATED) Xd' 26%NEGETIVE PHASE SEQUENCE WITHSTAND I2 8%UNBALANCED LOAD (I2/IN)xt 20 secFIELD CURRENT If 875 AdcSTATOR LEAKAGE REACTANCE xs 0.0952 PUSYNCRONOUS REACTANCE QUARD AXIS Xq 0.602 PU

Step up transformer

RATED VOLTAGE Un 11/132 kVRATED OUTPUTS Sn 63.9 MVA SHORT CIRCUIT VOLTAGE Uk 12.5 %

VECTOR GROUP YNd11

Auxiliary Transformer :

RATED VOLTAGE Un 11000/415 VRATED OUTPUTS Sn 500 KVA

VECTOR GROUP Dyn11

Excitation Transformer :

RATED VOLTAGE Un 11000/364 VRATED OUTPUTS Sn 630 KVA

VECTOR GROUP Dy5

Line Parameters:

POSITIVE SEQUENCE RESISTANCE R1 0.14 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.387 OHMS/KMZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L 70 KMLENGTH OF NEXT SHORTEST LINE L1 30 KMLENGTH OF NEXT LONGEST LINE L2 30 KM


5/29




Current TransformerPrimary Secondary

GENERATOR TRANSFORMER HV SIDE 400A 1AGENERATOR TRANSFORMER NEUTRAL 400A 1AGENERATOR NEUTRAL 4000A 5AGENERATOR TERMINAL 4000A 5A

AUX TRANSFORMER HV SIDE (OVERALL DIFF) 4000A 5AGENERATOR TRANSFORMER HV SIDE (DIFF) 600A 1A

AUX TRANSFORMER HV SIDE (OVERCURRENTPROT) 100A 1A

Voltage transformerPrimary Secondary

PROTECTION CORE 11000V 110V AVR CORE 11000V 110VNEUTRAL TRANSFORMER 11000V 110VMETERING CORE 11000V 110VLINE PT 110000V 110V


6/29




3.GENERATOR, TRANSFORMER AND UNIT AUXILIARY TRANSFORMER PROTECTION

A) GENERATOR DIFFERENTIAL PROTECTION 87G

This function protects the generator system from the neutral CTs to the generator terminal CTs. Whenfunction operates, the unit will be shut down immediately.

The differential setting value is calculated as follows:

555602916.14

3 11 3 gp

Sn kVA I A

Un kV

Generator primary current

Now with a CT ratio = 4000/5 A the generator secondary current is calculated

2916.14A5 3.65

4000

gp gs

I I A A

CTratio A Generator secondary current

The differential current setting is chosen to be 20% of the relay current rating, i.e.

A A I s 1520.087

This is in turn the equivalent to the generator rated current.

87 1% 100 100 27.4%

3.65 s

gs

I A I

I A

The bias slope is set to %40bias

Setting

Name of parameter

Range

Operate Value 1A Bias 40%


7/29




B) GENERATOR UNDEREXCITATION PROTECTION 40G

The under excitation MHO protection is used to detect failures in the excitation system of synchronousgenerators and to prevent damage to the equipment and power swings in the system.

The given direct reactances areSynchronous reactance x d 93.3%Transient reactance (saturated) x d 26%

A compensation factor F must be determined according to the equation below, in order to adjust thereactances to the CT and VT ratios:

11000 4000 110 51.5

2916.14 5 11000 100G r

G r

V CTratio I V A V A F

I VTratio V A A V V

whereIr rated current of the relayVr rated voltage of the relay (100V internally)

So the adapted reactances are

1.5 0.933 1.399

' ' 1.5 0.255 0.382d d

d d

x F x pU pU

x F x pU pU

The relay function setting is calculated as follows.

1.40

' 0.382 1.4 0.8912 2 2 2

d

d d

Diameter x pU

x x pU pU Center pU

The relay will be set to the next possible set point:

Diameter: 1.4 pUCenter: 0.89 pU

The Time Delay Stage 1 is set to 5 sec.

The parameters Operate Value St. 2, Rotor Cur. Comp., Rotor Cur. Offset has no relevance.Stage 2 is using the following logical function:

The Time Delay Stage 2 is set to 1 sec.The Operate Value of the Function "27/50" is set to 50V.

& TripUnderexcitation Stage 1 PickupUndervoltage 27/40 Pickup Time Delay Stage 2


8/29




C) GENERATOR NEGATIVE PHASE SEQUENCE PROTECTION 46G

The calculation of the setting values is done according to e.g. following generator data:

Rated power S G =55560 KVA Rated voltage V G = 11 kVNegative phase sequence current withstand 8%

Therefore the generator primary current is

555602916.14

3 11 3

g gp

gp

S kVA I A

V kV

and by using a current transformer with a CT ratio of 12000A/1A the corresponding secondarycurrent is

2916.14A5 3.64

4000 gp

gs I

I A ACTratio A

So the CT ratio compensation is

3.640.73

5 gs

N

I ACT ratio comp

I A

A further data for the generator (manufacturer data) is the inverse time characteristic i 2t, which isfor example

i2t=20s

Note: This characteristic is only valid for high current values i, as shown below (calculationtripping time).

So the time constant is selected to be

2

203125 52

0.08 s

s min

The tripping time can be calculated exactly

2

222

22ln

e

tripii

it

In case of a failure with n.p.s=45%, i 2 results to 5xi 2e , and the tripping time is


9/29




25ln 0.0408 127.5

24tript s

Compared with the manufacturer data

2 22

3.5 2098.7

0.45trip s s

t si

The values for the "neg.ph.sequ.alarm" and "neg.ph.sequ.trip" are selected as a percentage of the load limit. The load limit is reached after approximately 4 time constants when runningconstant admissible unbalance current. Typical values are (depends on the customer wishes):

neg.ph.sequ.alarm=80%neg.ph.sequ.trip=100%

D) GENERATOR OVERVOLTAGE PROTECTION 59

The overvoltage function protects the generator and the transformer against electrical field stresses.The function is provided with 2 stages whereby stage 1 has a lower voltage setting and a larger timedelay to cater for voltage regulator response time in case of full load rejections and stage 2 is providedwith a higher voltage setting above loss of load conditions and minimum time delay.

The calculation of the setting value for Stage 1 is as follows

The setting is chosen to be 110% of the generator rated voltage, therefore

V V

V V VTratio

V V

gp s 0.12110.1

1100011011000

%110

and the time delay is set to t = 2.0 s

Stage 2 is selected to be 125% of the generator rated voltage, therefore

V V

V V VTratio

V V

gp s 5.13725.1

1100011011000

%125

and the time delay is set to t = 0.0 s

Setting:

Name of parameter Range UnitOperate Value Stage 1 121.0 VOperate Value Stage 2 137.5 VTime Delay Stage 1 2 SecTime Delay Stage 2 0 SecType 1 Over Voltage


10/29




E) GENERATOR UNDERVOLTAGE PROTECTION 27G

The function is enabled during the generator set being connected to the power system and is disabled(blocked) by the 220kV CB open position. It is a 1-stage function.

The function settings are selected as follows.

V V V V ns 7711070.0%7027Time delay st 5.227 trip

Setting:

Name of parameter Range UnitOperate Value 77 [V]Time Delay 2,5 [Sec]Type 2 Under Voltage -

F) GENERATOR OVER/UNDERFREQUENCY PROTECTION 81O/U

The protective function has 4 Stages providing separate adjustable over- and under-frequency alarmand trip facilities. In addition to the mechanical overspeed and excitation system underspeed detectionit provides backup protection for such conditions. All stages will initiate an alarm and trip the unit.

The function settings are selected as follows.

Stage 1 overfrequency Hz f 0.521.81 time delay st 5.01.81 TripStage 2 overfrequency Hz f 5.522.81 time delay st 0.02.81 TripStage 3 underfrequency

Hz f 5.483.81 time delay

st 0.203.81 Trip

Stage 4 underfrequency Hz f 0.474.81 time delay st 0.04.81 Trip

The frequency settings need to be reviewed by the grid regulator.

Setting:

Name of parameter Range UnitMin. Volt. Setting 60 100 [V]Max. Volt. Setting 100 140 [V]Operate Value St. 1 52 [Hz]Time Delay St. 1 0.5 [s]

Type St. 1 OverdetectionOperate Value St. 2 52.5 [Hz]Time Delay St. 2 0.00 [s]Type St. 2 OverdetectionOperate Value St. 3 48.5 [Hz]Time Delay St. 3 20 [s]Type St. 3 UnderdetectionOperate Value St. 4 47 [Hz]Time Delay St. 4 0.00 [s]Type St. 4 Underdetection


11/29




G) GENERATOR STATOR EARTH FAULT PROTECTION 64G1

The function should serve as an earth fault function for the complete 11kV-system and for thegenerator up to 90% of its winding. With an earth fault in the 11kV-system (respectively on theterminals of the generator) we receive the following voltage in the generator neutral:

V V kV

kV ratiotransf

V V

Gen

N 5.63110/111

3

111

3sec

For a protection range of 90% we are able to calculate the setting value:

V V V range prot

V N set 18.35.63%100%95%100

%100.%100

sec

Selected value (according to setting range of the protection relay): 3.2V.

Time delay 1.0s

Setting:

Name of parameter Range UnitOperate Value 3.2 VTime Delay 1.0 SecType Over detection -

H) GENERATOR STATOR EARTH FAULT PROTECTION 64G2

For simplification an evenly distribution of the 3rd harmonic over neutral and terminals for the generator inhealthy condition is assumed (see figure below).

This distribution of the 3rd harmonic over neutral and terminal side is taken for the evaluation of earthfaults close to the generator neutral. The 3rd harmonic is measured in the generator neutral with asingle-phase voltage transformer and on the generator leads with a voltage transformer in open delta


12/29




connection. In case of an earth fault, the 3rd harmonic in the neutral is shorted whereby the value onthe generator terminals is increased by the same value (see figure below).

The following requirement is assumed: the relay with the measurement of the 3rd harmonic shallprotect the 15% of the stator coil close to the neutral point. The other 85% are protected by a normalovervoltage relay with the measurement of the fundamental frequency. The correct settings will bedetermined on site during earth fault tests. For this purpose different measurements of the 3rdharmonic in the generator neutral and on the generator leads have to be done in dependence of different generator loads for the healthy condition and for an earth fault.

The 3rd harmonics are processed via the following formula:

valuesmeasured volt neutral gen Harmrd ratiovolt al minter gen Harmrd ....3....3There should be a difference between the measured values for the healthy condition and for the caseof an earth fault.

Setting:

Settings will be determined on site during earth fault tests.

I) ROTOR EARTH FAULT PROTECTION 64R

This protection function comprises an auxiliary supply, which is connected between the earth and oneside of the field circuit. A direct voltage appears at the output, which is indirectly proportional to therotor insulation value and corresponds to the resistance. If this measured resistance is smaller than thesetting value, the required trip sequences for a unit shutdown are carried out.

The setting of the rotor earth fault protection is selected to

Stage 1: k R 50 with a time delay st delay 10


13/29




Stage 1 will initiate an Alarm only.

Stage 2: 1500 R with a time delay st delay 1

Stage 2 will initiate a trip.

Setting:

Name of parameter Setting UnitOperate Value, Stage1 50 [k ]Time Delay, Stage1 10 [s]Operate Value, Stage2 1.5 [k ]Time Delay, Stage2 1 [s]

J) GENERATOR REVERSE POWER PROTECTION 32G

When operating on reverse power this protective function will perform a unit shut down. The setting isselected due to our experience, i.e. -5.0% of the generator rating power.

The relay function setting is calculated as follows.

The relay primary power is

kW AkV I V P CTp prelp 77.5715130000.113cos3

The required -5.0% primary reverse power setting of the machine rating is

kW AkV I V P g p p 2259.04.26200.11305.0cos3%0.532

The required relay setting is P p32 /P relp = -225/5715.77 = -3.94%

The time delay is set to st 0.532

Setting:

Name of parameter

Setting Unit

Operate Value -3.94 [% P N]Time Delay 5 [s]Power Direction Direction 1 -

Phase Rotation Right -

K) VOLTAGE SUPERVISION FUNCTION 60G, 60M AND 60A

The setting for the negative phase sequence voltage for unbalanced secondary phase to phasevoltages is selected to

Operate Value U=50.0 V with a time delay t=5s


14/29




The second condition of the function is the setting for the negative phase sequence current. A highnegative phase sequence current indicates e.g. a failure in the network and the protection function isblocked. Normally an unbalanced voltage causes only a small n.p.s. current. So the setting is chosen tobe

Operate Value I=0.2 A

The selection parameter declares the setting for the phase rotation.

Setting:

Name of parameter Range UnitOperate Value I 0.2 A Operate Value U 50 VTime Delay 5 [s]Phase Rotation 2 (Right) -

L) GENERATOR UNDERIMPEDANCE PROTECTION 21G

This protection function consists of two stages, whereby the first stage is a so called impedanceprotection relay with a current interlock and the second stage is a backup protection, which is designedas overcurrent protection relay.

Therefore the generator current is

AV

S I

gp

g gp 4.262

3Generator primary current

The current and voltage transformer are designed according to the related voltage and rated current of the generator. For this purpose the VT ratio is selected to be 11000V/110V and the CT ratio of thecurrent transformer at the neutral is selected to be 10000/1A

The HV and LV transformer currents are:

AV

S I

hvp

t hvp 73.57

3HV transformer primary current

AV

S I

Lvp

t Lvp 35.577

3LV transformer primary current

The primary short circuit impedance of the transformer is obtained by

835.010011

50.711100

22

VAV k u

S V Z

k

t

TS p


15/29




Therefore the secondary transformer impedance is calculated

495.0825.0110005110300

p s Z VTratioCTratio

Z

In order not to overreach on external system faults an impedance of approximately 50% to 70% of thetransformer is selected with a corresponding setting of

247.073.15.0%5021 sG Z Z With time delay st G 2.021

The impedance current interlock setting, i.e. the overcurrent stage is a starting element for the underimpedance stage, is set to 120% of the generator rated current and calculated as follows

AratioCT

I Is LV 55.11300

535.5772.1

12.1

The time delay setting for stage 2 depends on the time grading of the remaining network.

Setting:

Name of parameter

Range Unit

Operate Value 0.25 [Ohm]Time Delay Imp. 0.2 [s]Time Delay Curr. Depends on time grading of remaining n/w [s]Current Interlock 11.55 A

M) DEAD MACHINE 27/51V

The overcurrent setting will be coordinated with all the other overcurrent functions (generator, transformer...).

A I V 10.151/27The typical operating range of a generator lies between 90% and 110% of the rated voltage. For generatorswith an isolated starpoint or with an earthed starpoint via a resistor the generator voltage drops to values of about 30% caused of a phase to phase fault. For this case the parameter "Voltage Limit" has to be chosen inthat way, that the generator voltage is below the setting of this parameter. The operating value of thecurrent setting will then be reduced to the "K-Factor". The setting is chosen to be 60% of the generatornominal voltage; this is for the secondary side:

V V V 0.66110%100%60

51/27


16/29




The k-factor is chosen to be 20% (to make sure that the current exceeds the setting value).

2.0 K

Setting:

Name of parameter Range UnitOperate Value 1.1 [A]

Voltage Limit 66 [V]K-Factor 0.2 -Time Delay 4 [s]

N) UNIT DIFFERENTIAL PROTECTION 87GT

The unit differential protection is protecting the system from the transformer 220kV CTs up to the 11kV

generator neutral and Auxiliary Transformer busbar CTs. When operating the unit is tripped and will beshut down immediately.

AkV

kVA

V

S I

hvp

t hvp 74.57

3110

11000

3HV transformer primary current

A A A

ACTratio

I I

hvphvs 96.00.1

6074.57

HV transformer secondary current

With a differential current setting of 0.20xIn the setting as a percentage of the transformer ratedcurrent can be calculated

%8.2010096.020.0%

A A

I I I hvs

shvs

By choosing a differential current setting of 0.20A secondary the primary setting is calculated asfollows.

A A A A

I ratioCT I hvshvp 7515.00.1

500

High set over current = 5.0 x I N =4.8

To cater for the different CT ratios on the transformer HV and LV side the CT ratio compensation factorsystem2/system1 and systm3/system1 is calculated according to following formulas whereby system 1refers to the 220kV HV winding, system 2 to the generator leg and system 3 to the aux transformer LVwinding.

5

5.0

11110

1/60

1/300

21

.1

212

kV kV

A

A

system system

ratiotr CTsystem

CTsystemcompCTratio


17/29




05.0

11

1101/60

1/300

3

1.1

313

kV

kV A

A

system

systemratiotr CTsystem

CTsystemcompCTratio

Setting:

Name of parameter Range UnitOperate Value 20% -High Set OC 4,8A -CT Ratio Comp. 2-1 0.5 -CT Ratio Comp. 3-1 0.05 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %

Bias 50 % Vector Group 1-2 1 - Vector Group 1-3 11 -Zero Sequ. Syst.1 On -Zero Sequ. Syst.2 Off -Zero Sequ. Syst.3 Off -

O) RESTRICTED EARTH FAULT PROTECTION 64REF

The grid transformer restricted earth fault protection 64REF is protecting the system from thetransformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (gridtransformer). High impedance scheme and high speed tripping is provided. When operating thefunction trips the generator unit.

CT data for the 220kV transformer feeder switchgear CTs.

CT ratio 600/1,0 A CT secondary current In = 1,0 A Estimated CT knee point voltage Vk > 300 VEstimated CT secondary resistance Rct = 5Estimated single lead resistance to relay Rl = 0.3

CT data for the 220kV transformer neutral CT


The CT requirements for the High impedance transformer restricted earth fault protective function, isaccording to the following formula.

Vk > 2IF ( Rct + 2 Rl + Rext )


18/29




Whereby IF is the maximum secondary three phase through fault current considering a short circuitfailure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3standard).

A AkV

kVACTratioV

S I T

F 24.120.1/6002203

175000163

16

220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V

Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than theminimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V

Vs=69V and the resulting external stabilising resistor for a relay setting I S = 0.15A (33% ratedcurrent) is

45515.0

15.01.069

S

S S

ST I

I relayVAV

R

The minimum CT kneepoint voltage should be greater than twice the relay voltage setting

220kV: Vk = 300V > 2 x V S = 138V

Check, whether a voltage limiting device is required:

V V V V V K f K p 3000 22

VK =300V

V R R R R I V RST l CT F f 56374553.02524.122

Thus, V V p 3579

Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.

Continuous power rating of the setting resistor:

W R I P ST S con 2.1045515.0 22

with a short time rating:

onds for W

R

I RV

R

V P

ST

F ST K

ST

fs short sec5.0 159

3.12

41

32


19/29




Thermal rating of the non-linear resistor:

W V AV I P K F 94.467730024.1215.3

44

A R

V I

ST setting 15.0

45569

Settings:

Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s

P) RESTRICTED EARTH FAULT PROTECTION 64REF- DISCRETE RELAY

The grid transformer restricted earth fault protection 64REF is protecting the system from thetransformer 220kV CTs up to the grid transformer neutral to cater for faults near the neutral point (gridtransformer). High impedance scheme and high speed tripping is provided. When operating thefunction trips the generator unit.

CT data for the 220kV transformer feeder switchgear CTs.


CT data for the 220kV transformer neutral CT


The CT requirements for the High impedance transformer restricted earth fault protective function, isaccording to the following formula.

Vk > 2IF ( Rct + 2 Rl + Rext )

Whereby IF is the maximum secondary three phase through fault current considering a short circuitfailure. The secondary fault current IF at the 220kV level is calculated as follows (British EATS 48-3standard).

A AkV

kVA

CTratioV

S I

T F 24.12

0.1/6002203

17500016

316


20/29




220kV lead CTs Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V220kV neutral CT Vk = 300 V > 2 x 12.24A (5 + 2 x 0.3 ) = 137.16 V

Therefore the selected restricted earth fault protection voltage setting is chosen to be greater than theminimum stability voltage IFx( Rct + 2 Rl + Rext )=68.58V

Vs=69V and the resulting external stabilising resistor for a relay setting I S = 0.15A (33% ratedcurrent) is

22.16215.0

15.01.0

69

S

S S

ST I

I relayVA

V R

The minimum CT kneepoint voltage should be greater than twice the relay voltage setting

220kV: Vk = 300V > 2 x V S = 138V

Check, whether a voltage limiting device is required:

V V V V V K f K p 3000 22

VK =300V

28.205522.1623.02524.122 RST l CT F f R R R R I V

Thus, V V p 48.2052

Due to ensure a safety margin a voltage limiting resistor is connected into the circuit.

Continuous power rating of the setting resistor:

W R I P ST S con 65.322.16215.0 22

with a short time rating:

onds for W

R

I RV

R

V P

ST

F ST K

ST

fs short sec5.082.2412

3.12

41

32

Thermal rating of the non-linear resistor:

W V AV I P K F 94.467730024.1215.344


21/29




A R

V I

ST setting 42.0

22.16269

Settings:

Name of parameter Range UnitOperate Value 42.5 % -Drop Off Delay 0.5 s

Q) OVERFLUXING PROTECTION 99G

The degree of saturation (overfluxing) is calculated according to following formula.

f V f V

S N

N

Whereby V and V N are the actual voltage and rated voltage and f and f N the actual frequency andrated frequency respectively.

The operating value of stage 1 is set to the maximum continuous overfluxing withstand of thegenerator, which must be specified by the manufacturer of the generator, i.e. to 105% voltage at ratedfrequency and the other stage is set to increasing higher levels.

Stage 1 alarm S 1A =1.05 time delay t=10.0sStage 2 trip S 2T=1.10 time delay t=1.0s

Setting:

Name of parameter Setting UnitOperate Value St. 1 1.05 [p.U.]Time Delay St. 1 10.00 [s]Operate Value St. 2 1.10 [p.U.]Time Delay St. 2 1.00 [s]Nominal Frequency 50.0 [Hz]Nominal Voltage 110 [V]

R) UAT DIFFERENTIAL PROTECTION 87UAT

This function protects the UAT system from the HV side CTs to the LV side CTs and operates for phaseto phase and three phase faults.

The differential setting value is calculated as follows:

AkV

kVA

V

S I

np

AT AT-HVp 24.26

311

500

3UAT (HV) primary current

Now with a CT ratio = 30/5 A the generator secondary current is calculated

A A A

ACTratio I

I AT-HVp

AT-HVs 37.4530

24.26UAT (HV) secondary current


22/29




AV

kVA

V

S I

np

AT AT-LVp 60.695

3415

500

3

UAT (LV) primary current

and with a CT ratio of 800/5A the corresponding secondary current is

A A A

ACTratio I

I AT-LVp

AT-LVs 87.01800

60.695UAT (LV) secondary current

The differential current setting is chosen to be 20% of the relay current rating, i.e.

A A I s 00.1520.087

This is in turn the equivalent to the generator rated current.

%16.3810062.20.1

100% A

A I

I I

AT-HVs

s

High set overcurrent = 5.0 x I N =13.1

The bias slope is set to %40bias

00.1

415.011

1/30

800

21

.1

2

kV kV

A system system

ratiotr CTsystem

CTsystemcompCTratio

Setting:

Name of parameter Range UnitOperate Value 38.16% -High Set OC 13.1 -CT Ratio Comp. 2-1 1.00 -2nd Harmonic 20 (to be verified during commissioning) %5th Harmonic 15 (to be verified during commissioning) %Bias 40 %

Vector Group 1-2 11 -Zero Sequ. Syst.1 Off -Zero Sequ. Syst.2 Off -

S) UAT OVERCURRENT PROTECTION 50U/51U

This function protects the auxiliary transformer against substantial overloading and heavy internal andexternal HV side short circuits and will trip the generator unit when operating. For the overcurrentprotection stage 1 an inverse time characteristic is chosen to cater for field forcing conditions and thecurrent setting is selected to be 1.0x the transformer rated current. The overcurrent protection stage 2setting is chosen to be about 5 x In with a small time delay


23/29




The protective function settings are obtained

AkV

kVA

V

S I

np

AT ATp 24.26

311

500

3

auxiliary transformer primary current

and with a CT ratio of 50/5A the corresponding secondary current is

A A A

CTratio I

I ATp

ATs 62.2550

24.26auxiliary transformer secondary current

Hence the current setting for Stage 1 is selected to be 120% of the rated current

A A I I ATs 15.32.162.22.151

With a Time Multiplier setting 5.0TMS normally inverse time characteristic

The Stage 2 current setting is selected to be approximately 5 x In and is obtained

A A I I 75.150.515.30.55150

The time delay of Stage 2 is chosen to be st 1.050

Setting:

Name of parameter Range UnitOperating Val. St.1 3.15 A

MS St.1 0.5 -

Curve normal inverse -Operating Val. St.2 15.75 A Time delay St.2 0.1 Sec

4. Distance Protection

Line Parameters:

POSITIVE SEQUENCE RESISTANCE R1 0.0659 OHMS/KMPOSITIVE SEQUENCE REACTANCE X1 0.3836 OHMS/KM

ZERO SEQUENCE RESISTANCE R0 0.272 OHMS/KMZERO SEQUENCE RESISTANCE X0 1.233 OHMS/KMLINE LENGTH L1 70 KMLENGTH OF NEXT SHORTEST LINE L2 30 KMLENGTH OF NEXT LONGEST LINE L3 30 KM

ARC RESISTANCE PH-PH Arc ph-ph 0 OHMS ARC RESISTANCE PH-EARTH Arc ph-e 20 OHMS

Primary Values per Km:


24/29




R1=0.0659X1=0.3836R0=0.272X0=1.233

3892.0111 22 X R Z

2517.8011

1),( 1 R X

Tan Ph Ph LineAngle

2626.1000 22 X R Z

5598.7700

0),( 1 R X

Tan E Ph LineAngle

Values Protected Line:

Primary Value:

R1pL1=0.0659*70=4.6130X1pL1=0.3836*70=26.8508R0pL1=0.2720*70=19.0400X0pL1=1.2330*70=86.3100

Secondary Value:

06.0 PTratioCTratio

R1sL1=4.6130*0.06=0.2767X1sL1=26.8508*0.06=1.6110R0sL1=19.0400*0.06=1.1424X0sL1=86.3100*0.06=5.1786

Earth Impedance (residual) Compensation:

Resistance Ratio:

Reactance Ratio:

Earth Compensation Factor, Ko:

04248.113

1

1

0

R

R

R

R

L

G

7381.0131

1

0

X X

X X

L

G

1

31

1

00 Z

Z K


25/29




i K 0508.07469.00

7486.00508.07469.0)( 220 K ABS

89.37469.00508.0

tan)( 10 K ARG

Next Shortest Line:

Primary Value:

R1pL2=0.0659*30= 1.9770X1pL2=0.3836*30= 11.5075R0pL2=0.2720*30= 8.1600X0pL2=1.2330*30= 36.99

Secondary Values:

R1sL2=1.9770*0.06=0.1186X1sL2=11.5075*0.06=0.6904R0sL2=8.1600*0.06=0.4896X0sL2=36.9900*0.06=2.2194

Next Longest Line:

Primary Value:

R1pL3=0.0659*30= 1.9770X1pL3=0.3836*30= 11.5075R0pL3=0.2720*30= 8.1600X0pL3=1.2330*30= 36.99

Secondary Values:

R1sL3=1.9770*0.06=0.1186X1sL3=11.5075*0.06=0.6904R0sL3=8.1600*0.06=0.4896

X0sL3=36.9900*0.06=2.2194

KPCL Setting Philosophy:

Zone1 : 80% of Protected Line

Zone2 : 100% of protected line + 50% of next shortest line


26/29




Zone3 : 100% + 100% of next longest line

Zone4 : Normally 15% to 20% of Zone 1

Zone 1 Calculation :

Phase to Phase Faults :

Primary Values

69.3)8.0*11(11 pharcph pL R p Z R

481.21)8.0*11(11 pL X p Z X

Secondary Values

221.006.0*1111 p Z R s Z R289.106.0*1111 p Z X s Z X

Phase to Earth Faults :

Primary Values

232.35)8.0*10(10 earcph pL R p Z R

048.69)8.0*10(10 pL X p Z X

Secondary Values

114.206.0*1010 p Z R s Z R143.406.0*1010 p Z X s Z X



Primary Values

602.5)5.0*21()11(21 pharcph pL R pL R p Z R

605.32)5.0*21()11(21 pL X pL X p Z X

Secondary Values

336.006.0*2121 p Z R s Z R956.106.0*2121 p Z X s Z X


27/29





Primary Values

120.43)5.0*20()10(20 earcph pL R pL R p Z R

805.104)5.0*20()10(20 pL X pL X p Z X

Secondary Values

587.206.0*2020 p Z R s Z R288.606.0*2020 p Z X s Z X



Primary Values

590.6)31()11(31 pharcph pL R pL R p Z R

358.38)31()11(31 pL X pL X p Z X

Secondary Values

395.006.0*3131 p Z R s Z R

301.206.0*3131 p Z X s Z X


Primary Values

200.47)30()10(30 earcph pL R pL R p Z R

300.123)30()10(30 pL X pL X p Z X

Secondary Values

832.206.0*3030 p Z R s Z R398.706.0*3030 p Z X s Z X

Reverse Zone 4 Calculation :


Primary Values


28/29




923.0)2.0*11(41 pharcph pL R p Z R

370.5)2.0*11(41 pL X p Z X

Secondary Values

055.006.0*4141 p Z R s Z R322.006.0*4141 p Z X s Z X


Primary Values

808.23)2.0*10(40 earcph pL R p Z R

262.17)2.0*10(40 pL X p Z X

Secondary Values

428.106.0*4040 p Z R s Z R036.106.0*4040 p Z X s Z X

Settings:

Name of parameter Set Value Unit

Line Angleph-ph 80.2517

Degreesph-e 77.5598

Earth faultCompensation Factors

Re/Rl 1.042489Xe/Xl 0.738143

Zone 1(Forward)

ph-ph R 0.221

OhmsX 1.289

ph-e R 2.114X 4.143Zone 2(Forward) ph-ph

R 0.336 OhmsX 1.956


29/29



ph-e R 2.587X 6.288

Zone 3(Forward)

ph-ph R 0.395

OhmsX 2.301

ph-e R 2.832X 7.398

Zone 4(Reverse)

ph-ph R 0.055

OhmsX 0.322

ph-e R 1.428X 1.036

Operation time

Zone 1 0

secsZone 2 0.4Zone 3 0.8Zone 4 1.2

drs_setting calculation reference 1

Documents