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CONSOLIDATED REPORT ON THE AUDIT FINDINGS OF ESKOM TRANSMISSION COMPLIANCE AUDITS
Year of Assessment: 2014/15 Financial Year
All enquiries and correspondence to be directed to the Head of Department unless indicated otherwise by means of a formal letter signed by the Head of Department: Electricity Licensing, Compliance and Dispute Resolution
Tel : +27 (0)12 401 4794
National Energy Regulator
Kulawula House
526 Madiba Street
Arcadia, Pretoria
0083
PO Box 40343
Arcadia
0007
Tel : +27 (0)12 401 4600
Fax : +27 (0)12 401 4700
Website : www.nersa.org.za
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CONTENTS ABBREVIATIONS ............................................................................................................. iii
EXECUTIVE SUMMARY ................................................................................................... iv
1. INTRODUCTION ........................................................................................................ 1
2. METHODOLOGY/APPROACH .................................................................................. 2
3. CRITERIA FOR PLANT/EQUIPMENT RATINGS ....................................................... 4
4. SUBSTATION PLANT/EQUIPMENT ASSESSED ...................................................... 5
5. EQUIPMENT ASSESSMENT RESULTS AND SUMMARY OF FINDINGS ................ 5
6. ASSESSMENT OF DISSOLVED GAS ANALYSIS RESULTS .................................. 26
7. SUBSTATION DOCUMENTATION AND MAINTENANCE ....................................... 33
8. CONCLUSIONS ....................................................................................................... 36
ii
ABBREVIATIONS
AIS Air Insulated Substation
CAPs Corrective Action Plans
CT Current Transformer
DC Direct Current
DGA Dissolved Gas Analysis
GIS Gas Insulated Substation
HV High Voltage
IEEE Institute of Electrical and Electronic Engineers
kV Kilo Volt
MTS Main Transmission Substation
MYPD Multi- Year Price Determination
NERSA National Energy Regulator of South Africa
OEM Original Equipment Manufacturer
PCB Polychlorinated Biphenyl
PPM Parts per Million
PTW Permit to Work
SAP Systems Applications Programming
SO System Operator
SQI Service Quality Incentives
SVC Static Var Compensator
TNSP Transmission Network Service Provider
TSP Transmission System Planner
VT Voltage Transformer
WTI Winding Temperature Indicator
YTD Year to Date
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EXECUTIVE SUMMARY
The Electricity Regulation Act, 2006 (Act No 4 of 2006) (‘the Act’), stipulates that the Regulator must enforce performance, compliance and take appropriate steps in the case of non-performance.
Pursuant to Section 4(a) (vii) of the Act, all licensed entities are subject to an audit for compliance with licence conditions imposed by the Energy Regulator. The audit objectives are to assess compliance with applicable regulatory requirements, validate evidence of self-reported non-compliances, document the Licensee’s compliance level and plans, and monitor the implementation of corrective action plans.
Eskom Transmission is the holder of an Electricity Transmission Licence issued by the Energy Regulator with the following licensed activities:
• Transmission Network Service Provider (TNSP); • System Operator (SO); • Transmission System Planner (TSP); and • Grid Code Secretariat.
The audit focussed on Eskom Transmission’s function as a TNSP as per its licence which stipulates that “The Transmission Division shall operate and maintain the Licensee’s assets constituting the transmission network in accordance with the Grid Code in order to transmit electricity across the Transmission System within the areas designated in Schedule 1.”
The Energy Regulator conducted compliance audits for the Main Transmission Substations (MTS) listed in Table 1 below:
Table 1: List of Eskom Transmission substations audited
No. Substation Name Grid Location Audit Date 1 Craighall (delta) Central 10 Nov 2014
2 Bighorn North 12 Nov 2014 3 Sol North East 14 Nov 2014 4 Illovo East 20 Nov 2014 5 Muldersvlei West 24 Nov 2014 6 Aurora West 25 Nov 2014 7 Poseidon South 02 Dec 2014 8 Luckoff South 05 Dec 2014
The audit included a plant and equipment inspection, assessment of documentation and records and analysis of Dissolved Gas in oil Analysis results. Most of the substations were found to be in good condition, documentation was available, and procedures stipulated by the standards and the South African Grid Code were being adhered to.
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The plant and equipment assessments were based on a range of ratings from 1 (very poor condition), 2 (poor condition), 3 (fair condition), 4 (good condition) and 5 (very good condition). These parameters for each rating level are explained in detail further in the report. No weighting was applied to the ratings and every plant and equipment was treated equally.
Based on the condition assessments and documentation/records received from Eskom Transmission for each substation, the summary of findings (detailed findings are available in the individual reports prepared for each substation) for all the substations that were audited are as shown in Table 2 below: Table 2: Summary of Overall Substation Condition Findings
No. Findings
1.
A number of transformers across the various grids either have oil weeps or are leaking oil. Oil serves as a cooling and insulation medium and whilst no transformer had oil below the optimum level, the leaks and/or weeps require attention.
2. Infra-red scanning results are not kept on site for “at least one year” as required by the Eskom Standard for Infra-Red Scanning on Transmission Plant (Unique Identifier TST41-717)
3.
Operation of split bus bar where there are double bus bar arrangements reduces the flexibility of the substation during maintenance or under fault situations. This was in one substation. Eskom indicated they are planning to replace underrated equipment.
4. In several substations, the yard stones that has been washed away or where the soil is exposed poses a risk of shock to personnel or visitors due to step and touch potentials.
5. Significant mould growth on the silicon skirtings of some bushings was identified in one of the coastal substations, which increases the risk of flashovers due to the moisture content of the moulds.
6. Rusted steel structures, platforms and security fencing which makes them weaker and susceptible to failure.
7.
There are some inconsistencies in signing off workers’ register and Permit to Work (PTW) forms. In some cases different operates use different approaches in the same grid while in some there arfe differences across grids. Eskom already indicatefd they would explore the possibility of revising the procedures or the forms.
8. Original battery test sheets were not consistently send to the central office as required.
9. Bird nests and droppings are present on some equipment such as line traps, transformers, and capacitor banks.
v
10. Work orders in one location are not closed in the maintenance scheduling system when the work has been completed on site.
11. In a few cases routine oil sampling was not done within the six month sample as stipulated in the Oil Management Standard (Unique identifier 41-966).
12. Cracked equipment foundations were identified in few substations.
13.
Whilst age is not the sole determinant for replacement of CTs and VTs, in one location the VTs and CTs are over 48 years old and pose a higher risk of failure. Eskom indicated that are implementing a “CT Care Programme.”
14. Signage on gates and equipment in some substations require either replacement or rehabilitation to ensure that they serve their purpose of informing, warning/informing and safety.
vi
1. INTRODUCTION
The National Energy Regulator derives its mandate to conduct compliance audits for licensed electricity transmitters from the Electricity Regulation Act, 2006 (Act No. 4 of 2006) ('the Act'). The National Energy Regulator is entrusted with the Electricity Supply Industry as the custodian and enforcer of the regulatory requirements.
The transmission licence issued to Eskom Transmission mandates it in Section 4.1 to “operate and maintain the Licensee’s assets constituting its transmission network in accordance with the Grid Code”, as transmission Network Services Provider (TNSP).
The challenges being faced by Eskom in meeting demand recently made it necessary to urgently assess the efficiency and effectiveness of the planning, operating and maintenance of the electricity infrastructure that falls under Eskom transmission division.
The assets’ status and condition is critical in determining if they can provide the service that they were designed for. It is important to note that the transmission network is ageing and thus requires more frequent maintenance, or rehabilitation or asset replacement altogether in some worst cases.
Plant and equipment that is in poor condition often lead to unplanned and costly failures that can lead to the licensee failing to comply with its own standards and the Grid Code.
Unplanned outages have a huge negative economic impact on the South African economy, as well as Eskom Transmission due to the penalties that may be imposed should the Quality of Supply not meet the levels stipulated in the Service Quality Incentives (SQI) under the Multi-Year Price Determination (MYPD) as approved by the Energy Regulator.
This report is a consolidation of eight audit reports that were prepared and discussed with Eskom Transmission. It summarises the results of the plant/equipment status and condition as assessed by the team, the perceived risks (findings) as well as recommendations to address the observed risks.
The audit team comprised the following members:
Mr Lovemore Seveni Senior Transmission & Trading Engineer
Ms Lorato Dlamini Compliance Technician
Mr Tamai Hore Senior Generation Licensing Engineer
Mr Siphiwe Khumalo Compliance Engineer
Mr Diketso Ratema Senior Quality of Supply Engineer
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2. METHODOLOGY/APPROACH
In conducting the audit of the transmission assets to verify their status and condition, the following approach was adopted in consultation with Eskom Transmission:
a) decide on the number of Main Transmission Substations (MTS) to be visited
using agreed criteria and other additional information from Eskom;
b) engage Eskom transmission on what the audit will entails and share the audit
sheet which was used to collect the information while on site;
c) finalise the logistical arrangements and contacts at the different sites to be
visited (e.g. induction and safety requirements including Personal Protective
Clothing –PPE);
d) conduct the non-intrusive visual inspections (with Eskom representatives) of
high voltage yard and control room equipment at the selected MTS and
evaluate equipment according to the audit sheet;
e) inspect site maintenance plans, inspection records and other documentation on
site as well as other standards, procedures and policies applicable to the sites;
f) prepare draft reports on findings on each substation and obtain comments from
Eskom;
g) prepare final reports for submission to the Energy Regulator;
h) communicate final decision to Eskom and request management comments
[including Corrective Action Plans (CAPs)]; and
i) monitor implementation of the CAPs and prepare reports for submission to the
Energy Regulator.
Eskom Transmission was very supportive before, and during the audit and all the relevant staff were made available on the day of the audit, including for the primary and secondary plants. Queries to site staff and head office were responded to timeously and all the information requested was provided. Since the major assets constituting the transmission system are its Main Transmission Substations (MTSs), the effectiveness and extent of Eskom transmission’s operations and maintenance as provided for in the Grid Code can be evaluated from assessing the grid assets and the associated documentation. Due to the extended nature of the transmission grid and the available resources,
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the team selected eight substations out of about 170 MTSs to be audited during the 2014/15 financial year.
The following criteria was utilised to select the substations to be audited:
i. grid location of the substation; ii. location/ use of the substation iii. transformation voltages; iv. technology/type of insulation; and v. age of the substation
The selected substations are as shown in Table 3 below: Table 3: List of Eskom Transmission substations audited
Selection Criteria No. Substation
Name Grid
Location Location Voltage
Level (kV)
Technology Vintage (Years)
Audit Date
1 Craighall (delta)
Central City 275 GIS 39+ 10 Nov 2014
2 Bighorn North Industrial
400 AIS 34+ 12 Nov 2014
3 Sol NE Industrial
400 AIS 49+ 14 Nov 2014
4 Illovo East Coastal 275 AIS-SVC 44+ 20 Nov 2014
5 Muldersvlei
West Country 400 AIS 61+ 24 Nov 2014
6 Aurora West Coastal 400 AIS 41+ 25 Nov 2014
7 Poseidon South Coastal 220 AIS-SVC 44+ 02 Dec 2014
8 Luckoff South Country 400 AIS-Capacitor
12+ 05 Dec 2014
The assessments were non-intrusive (no testing, injection, switching or measuring) with the plant in service.
In addition, the following information and standards were requested from Eskom to assist with the assessment and evaluations:
• dissolved Gas Analysis (DGA) results for the past five years (2009 – 2014) for
all the oil-filled equipment at the selected substations;
• maintenance plans for the selected substations for 2012 to 2014;
• refurbishment plans for the selected substations;
• operating and single line diagrams;
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• Eskom transmission asset register;
• sample design information for one substation;
• Eskom standard - Oil Management within the transmission division;
• Eskom standard – Standardization of High Voltage (HV) Plant Maintenance
template for Time-based maintenance;
• Eskom standard – Infra-red Scanning of HV current carrying equipment; and
• Transmission Grid’s Maintenance Performance Report – September 2014/15.
3. CRITERIA FOR PLANT/EQUIPMENT RATINGS
The criteria for inspection and assessing equipment are listed below. The inspection checklists were completed by means of walk-through inspections. The condition ratings for electrical plant and equipment are indicated at the end of each description. The rating was done based on the following guideline:
Table 4: Rating of electrical equipment guide
GRADE
CONDITION
DESCRIPTION
5 Very Good
Plant in sound physical condition designed to meet current standards. Operable and well-maintained. Asset likely to perform adequately with routine maintenance for 10 years or more. No work required.
4 Good
Acceptable physical condition but not designed to current standards, or showing minor wear. Deterioration has minimal impact on asset performance in medium term (5-10 years). Only minor work required (if any).
3 Fair
Functionally sound plant and components, but showing some wear with minor failures and some diminished efficiency. Minor components or isolated sections of the asset need replacement or repair but asset still functions safely at adequate level of service. For example, bearing and gland wear becoming evident and some corrosion present. Deterioration beginning to be reflected in performance and high attendance for maintenance. Failure unlikely within 2 years but further deterioration likely and major replacement required within next 5 years. Work required but asset is still serviceable.
2 Poor
Plant and components function but require a high level of maintenance to remain operational. Likely to cause a marked deterioration in performance in short-term. Likely need to replace most or all of assets within 2 years. Minimum level of risk to health or safety but work required within 2 years to ensure asset remains safe. Substantial work required in short-term, asset barely serviceable.
1 Very poor
Failed or failure imminent. Plant and component effective life exceeded and excessive maintenance costs incurred. A high risk of breakdown with a serious impact on performance. No life expectancy. Health and safety hazards exist which present a possible risk to public safety or asset cannot be serviced/operated without risk to personnel. Major work or replacement required urgently.
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In addition, the following generic condition rating for other assets was used: Table 5: Generic condition for other transmission assets
DESCRIPTION
DETAILED DESCRIPTION
VG - Very good Sound structure, well maintained. Only normal maintenance required. G - Good Serves needs but minor deterioration (< 5%). Minor maintenance required. F - Fair Marginal, clearly evident deterioration (10-20%). Significant maintenance
required. P - Poor Significant deterioration of structure and/or appearance.
Significant impairment of functionality (20-40%).Significant renewal/upgrade required. Safety/Environment Issues
VP - Very poor Unsound, unsafe, failed needs reconstruction/ replacement (> 50% needs replacement)
4. SUBSTATION PLANT/EQUIPMENT ASSESSED
Substation equipment were assessed by means of on-site evaluation and using records of equipment that is available at that particular substation. The following equipment and assets were assessed: Table 6: List of substation equipment and assets assessed
• Substation security fencing • Outdoor yard earthing • Substation buildings (Civils) • Substation foundations (Civils) • Substation yard including stone • Signage • Steel structures • Substation lightning protection
systems • Substation Yard Lighting • Safety (CO2 fire extinguishers,
earthing equipment, ladders) • Substation documentation • Power Transformers • Transformer bushings • Capacitor banks, including
capacitors • Static Var Compensators
• HV Circuit Breakers • Lightning and Surge Arresters • Current transformers • Voltage transformers • Isolators • Earth Switches • Coupling capacitors • Line traps • Bus bars, conductors and clamps • Power cables • Battery chargers • Batteries • Tele control Equipment • Control and Protection Panels • Protective relays • Control Cables • Indoor switchgear • GIS bushings
5. EQUIPMENT ASSESSMENT RESULTS AND SUMMARY OF FINDINGS
Based on the assessments and observations of the individual reports prepared for each of the eight substations visited, the rating for each equipment/asset is plotted.
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An overview condition of the piece of equipment/asset is then given and any non-compliances or outliers are discussed briefly.
5.1. Substation security fencing
Figure 1: Substation security fencing ratings
• Fencing at most of the substations fencing were intact and functional. • There are severe signs of rust at Bighorn and Muldersvlei substations at the
capacitor banks and around transformers 2 and 3 respectively.
5.2. Outdoor yard earthing
Figure 2: Outdoor yard earthing ratings
• The equipment earthing in the yards were in a general good condition at most of the substations assessed. No signs of theft of earthing conductors were evident.
0
1
2
3
4
5
6
Ratin
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Substations
Outdoor Yard Earthing
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• Sol substation has a broken earth bar at transformer No. 3. The Eskom team on site was alerted to the fact on site.
5.3. Substation buildings (civils)
Figure 3: Substation buildings (Civils) ratings
• The substation buildings at most of the substations were in good condition. • The control room at Illovo substation requires some rehabilitation including
repainting. • A few cracks were noticed on the substation buildings at Muldersvlei substation.
5.4. Substation foundations (civils)
Figure 4: Substation foundations ratings
• Most of the substation foundations are in a general good condition.
0
1
2
3
4
5
6
Ratin
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Substations
Substation Building (Civils)
0123456
Ratin
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Substations
Substation Foundations (Civils)
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• Although the foundation of Illovo transformer No. 2 circuit breaker is intact, a 10mm layer of screed applied to the surface of the foundation is cracking.
• The foundations of some equipment at Muldersvlei substation have a cracking problem especially those for equipment on the 400kV busbars as well as on equipment on the 400/132kV transformers.
• Foundations at Camden No. 1 feeder and at transformer No. 3 at Sol substation are disintegrating. However, some repair work has been done on some foundations.
5.5. Substation yard including stone
Figure 5: Substation yard including yard stone ratings
• The substation yards are generally in fair condition. However, some yards have weeds and the yard stone in most substations require replacement in order to meet the safety requirements.
• Some vegetation was present at Craighall substation and vegetation control is required.
• Restoning is required around Muldersvlei transformers 6 and 7 as the soil is exposed. Some vegetation control is also required.
• There were also patches of weeds evident at Poseidon substation. There was a contractor on site dealing with the weed issue at the time of the audit but the problem seemed persistent.
• At Sol substation, the yard stone around the Kriel and Camden feeder require restoring.
0
1
2
3
4
5
6
Ratin
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Substations
Substation Yard& Stone
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5.6. Signage
Figure 6: Substation signage ratings
• Most of the substations assessed had their equipment and structures well labelled.
• Signages at some battery charger panels at Bighorn substation were handwritten in ink translating Afrikaans to English.
• Not all phases are labelled at Muldersvlei substation and some gate signs are faded.
• The white phase label of the SVC was missing at Poseidon substation. • A small number of signs is rusted at Sol substation.
5.7. Steel structures
Figure 7: Steel structures ratings
• Most structures are in a general fair condition
0
1
2
3
4
5
6
Ratin
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Substations
Signage
0
1
2
3
4
5
6
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Substations
Steel Structures
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• The steel structures at Bighorn substation have significant signs of rust and require painting.
• Some steel structures are in a bad condition at Illovo substation as they are affected by the coastal weather. The structures at Rayon 1 132kV circuit breaker and bus coupler are rusted and are peeling off.
5.8. Substation lightning protection systems
Figure 8: Substation lightning shielding ratings
• The lightning protection systems were found to be adequate for all the substations. The catenary wire covers all the equipment and lightning masts are installed.
5.9. Substation yard lighting
Figure 9: Substation yard including yard stone ratings
0
1
2
3
4
5
6
Ratin
gs
Substations
Substation Lightning Shielding
0
1
2
3
4
5
6
Ratin
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Substations
Substation Yard Lighting
Page 10 of 36
• The majority of the substations have adequate lighting including emergency lighting from Direct Current (DC) supplies.
• Sol substation does not have adequate lighting. Staff rely on portable lighting when required. The portable torches are shared among nine substations spread geographically in the region, which poses an operational challenge.
5.10. Safety (CO2 fire extinguishers, earthing equipment and ladders)
Figure 10: Safety ratings
• Fire extinguishers in all substations were not overdue for inspection and/or service and were the carbon-dioxide type.
• There was adequate portable earthing for all the substations and there were no signs of rust or wear and tear.
• For all the stations, safety signs for use during switching operations or maintenance work were also available in the storeroom.
• Ladders were also available in the storerooms and were in good condition for all the substations.
0
1
2
3
4
5
6
Ratin
gs
Substations
Safety
Page 11 of 36
5.11. Substation documentation
Figure 11: Substation documentation ratings
• Most of the substation documentation was available and up to date. • At Bighorn substation, some Permit to Work forms were not signed off and
cleared by the Authorised person. • The document filing system needs to be enhanced at Craighall substation. • At Illovo substation, staff are not signing out (having signed in at the
commencement of work) once the work has been completed. There are interpretations that need to be clarified which may include revision of the workers’ register form. In addition, there is a need to align all grids in signing of instruction forms and other documents.
• Some battery test sheet originals were not pulled out for onward transmission to the central repository where records are kept. The inconsistences regarding the signing out of the workers register needs to be aligned at Luckhoff substation as well.
0
1
2
3
4
5
6
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Substations
Substation documentation
Page 12 of 36
5.12. Power transformers
Figure 12: Power transformer ratings
• Most of the transformers in the substations assessed are in a general fair
condition. • There is a bird droppings problem at Aurora substation especially transformer
No. 11. The problem also affects transformers No. 12, 13 and 14. • There are some oil leaks on transformer No.2 at Bighorn substation. All the
transformers at this substation also have some bird droppings that have accumulated over time. However, the transformers are still relatively new.
• There were significant oil leaks on transformer No. 2 at Craighall substation. The transformers are reaching 40 years of age but are fitted with online gas monitoring equipment.
• At Illovo substation, transformer No. 1 is rusting and there is oil weeping at the bushings and the Bucholz. Eskom staff advised that repair work on this transformer had been deferred to January 2015 due to demand from distribution. Illovo transformer No.2 has bird nests, a malfunctioning pressure release valve and a broken earth linkage. The Winding Temperature Indicator (WTI) on Illovo transformer No. 3 is also not working and there is oil weeping on this transformer. The blue phase transformer of SVC 1 also needs derusting, regasketing and painting.
• At Muldersvlei substation, half of the eight transformers are over 40 years of age but are fitted with online gas monitoring equipment. Some oil leaks were also evident under the cooling fins of transformer No. 2. The temperature winding gauge glass is misty on transformer No. 3 and it is impossible to get the reading. Muldersvlei transformer No. 7 also had vegetation growing on the civil works.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Aurora Bighorn Craighall Illovo Muldersvlei Poseidon Sol
Ratin
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Substations
Power transformers
Page 13 of 36
• There were oil leaks visible under the fins of Poseidon transformer No. 3 and also on Poseidon transformer No. 22. The temperature indicators on transformer No. 3 were covered in paint and were therefore not legible. Transformers No. 11 and 13 also had oil weeping at this substation.
• The drainage at Sol transformer No. 3 is blocked and there is stagnant water accumulated in the bund wall. The transformer also requires repainting . Sol transformer No. 4 has oil leaks that are evident and there is also a drainage problem in the bund wall. Transformer No. 2 has oil leaks although it is fairly new and its foundation is cracking.
5.13. Power transformer bushings
Figure 13: Power transformer bushings ratings • Most of the transformer bushings are in a general good condition. • The oil level indicators of some of the bushings at Illovo substation are faded
and/or dirty thus making them difficult to read. • Some oil level indicators of the bushings at Muldersvlei substation are also
faded and/or dirty making it impossible to read. • A condition assessment of the bushings on the Poseidon substation coupling
reactor No.3 needs to be done. Eskom confirmed that tests are scheduled for March 2015.
0
1
2
3
4
5
6
Aurora Bighorn Craighall Illovo Muldersvlei Poseidon Sol
Ratin
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Substations
Power transformer bushings
Page 14 of 36
5.14. Capacitor banks and capacitors
Figure 14: Capacitor banks and capacitors ratings
• The majority of the capacitors and capacitors banks were in very good
condition. • No Polychlorinated Biphenyl (PCB) insulated or cooled type capacitors were
in service at the assessed substations. PCB insulated capacitors are no longer used due to their toxicity.
• The high presence of birds in the live capacitor bank was a concern at Luckhoff substation.
5.15. Static VAR Compensators (SVCs)
Figure 15: Static VAR Compensator ratings
• The SVCs were in a general good condition at the substations assessed.
0
1
2
3
4
5
6
Bighorn Illovo Luckhoff Muldersvlei Poseidon
Ratin
gs
Substations
Capacitor banks&capacitors
0
1
2
3
4
5
6
Illovo Muldersvlei Poseidon
Ratin
gs
Substations
Static Var Compensators
Page 15 of 36
• While the SVC at Illovo was in good condition, the single-phase transformers had signs of oil weeping.
5.16. HV Circuit Breakers
Figure 16: HV Circuit breaker ratings • The circuit breakers are in a general good condition at some of the
substations and fair condition at others. • Some circuit breaker bushings at Aurora substation such as the 132kV
Blouwater and Kerkbosch feeders have developed moulds on the silicon skirting. The circuit breaker mechanism compartment of transformer No. 14 is similarly affected by these moulds. Eskom staff indicated that tests done showed the moulds do not affect the insulation levels. The results of the test is to be requested as part of the monitoring exercise.
• At Illovo substation, there is a significant number of circuit breakers that are over 40 years old. While they are still operational, their age is likely to lead to a higher failure risk.
• There are six circuit breakers that are over 40 years old at Muldersvlei substation. In addition, there is a 132kV yard, which the audit team was advised not to enter due to the risk of explosion. The risk of explosion was due to overloading and lack of maintenance.
• At Poseidon substation, two circuit breakers are over 40 years old and seven will reach 40 years of age in 2015. Older circuit breakers pose a higher risk of failure if not properly maintained and managed.
0
1
2
3
4
5
6
Ratin
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Substations
HV Circuit breakers
Page 16 of 36
5.17. Lightning and Surge Arresters
Figure 17: Lightning and surge arresters ratings
• The surge arresters in all stations are in a general good condition. No broken
porcelain or earthing conductors were evident. • As was the case with the circuit breakers, the lightning arresters at Aurora
substation were also affected by the moulds on the silicon skirting. This is due to the coastal climate where the substation is located.
• Bird nests were identified on the Dinaledi No.1 400kV feeder bay at Bighorn substation.
5.18. Current Transformers
Figure 18: Current transformer ratings
0
1
2
3
4
5
6
Ratin
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Substations
Lightning & Surge Arresters
0
1
2
3
4
5
6
Ratin
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Substations
Current transformers
Page 17 of 36
• Most current transformers are in good condition in the substations assessed (note: The current transformers at Craighall substation are in the GIS chamber and not visible).
• The current transformers at Aurora substation are increasingly ageing especially at 50kV. Eskom advised that a “CT Care” plan has been developed to ensure that ageing CTs do not malfunction, which includes extensive tests.
• The current transformers at Muldersvlei are in good condition but require cleaning.
5.19. Voltage Transformers
Figure 19: Voltage transformer ratings
• The voltage transformers were in a general good condition in all the substations (note: Craighall substation VTs are enclosed in the GIS chamber).
• The voltage transformers at Aurora substation require minor maintenance in the form of cleaning to reduce risk of flashovers.
• Some voltage transformers at Muldersvlei substation are well over 40 years e.g. the 66kV VTs are 48 years old. Eskom’s commented that tests are done on older VTs (and older equipment in general) to detect any anomalies.
0
1
2
3
4
5
6
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Substations
Voltage transformers
Page 18 of 36
5.20. Isolators
Figure 20: Isolator ratings
• The isolators are in a general good condition in most of the substations (Isolators at Craighall substation are enclosed in the GIS chambers).
• Isolators at Aurora substation are affected by moulds on the silicon skirtings. • The isolators at Illovo substation are in good condition but the steel platforms
on which they are mounted are rusting. • Isolators at Muldersvlei substation at the bus bar links are old and the bushings
are heavily polluted. • At Sol substation, the porcelain on the 132kV Sasol 3 feeder is broken. Clipton
was applied to minimise tracking. 5.21. Earth Switches
Figure 21: Earth switch ratings
• The earth switches are in general good condition and the earth linkages are not open.
• Mould growth also affected the earth switches at Aurora substation. • There was a bird nest on the earth switch of the 275kV transformer No. 3 at
Bighorn substation.
0
1
2
3
4
5
6Ra
tings
Substations
Isolators
0
1
2
3
4
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6
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Substations
Earth switches
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• The earth switch in capacitor bank No. 1 had a bird nest at Luckhoff substation but the isolator was in good condition.
5.22. Coupling capacitors
Figure 22: Coupling capacitor ratings
• The coupling capacitors in the majority of the substations were in a very good
condition. • Minor steel structure maintenance (painting) is required on the Droerivier No.
2 feeder.
5.23. Line traps
Figure 23: Line trap ratings
0
1
2
3
4
5
6
Ratin
gs
Substations
Coupling capacitors
0
1
2
3
4
5
6
Ratin
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Substations
Line traps
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• The line traps were in a general fair condition for most of the substations assessed but there is bird nest problem.
• The 400kV Juno No. 1 feeder is affected by mould formation due to the coastal conditions at Aurora substation. In addition, the line traps do not have the netting that prevents birds from nesting.
• Bird nests were also present at Bighorn substation on Pluto No. 1, Spitskop and Dinaledi feeders.
• Bird nests were also present in the line traps at Craighall substation. • There were also bird nests at Luckhoff substation due to the large number of
birds attracted by the warmth of the capacitor banks. • The netting on the line traps at Muldersvlei substation and a large number of
the line traps are over 40 year old. 5.24. Bus bars, conductors and clamps
Figure 24: Busbars, conductors and clamps ratings
• Bus bars, conductors and clamps in the yards of most of the substations were
in very good condition. • At Illovo and Muldersvlei substation, the insulation of the earthing conductors
on the isolators were burnt but not broken.
0
1
2
3
4
5
6
Ratin
gs
Substations
Busbar, conductors & clamps
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5.25. Power cables
Figure 25: Power cables ratings
• Samples of the exposed power cables assessed in all the substations were in
very good condition. No anomalies were evident.
5.26. Battery chargers
Figure 26: Battery charger ratings
• Most of the battery chargers were in good condition in all the substations. Back
up chargers were available for both the 50V and 220V chargers. • The handwritten signage on one of the chargers at Bighorn substation needs
to be rectified.
0
1
2
3
4
5
6
Ratin
gs
Substations
Power cables
0
1
2
3
4
5
6
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gs
Substations
Battery chargers
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5.27. Batteries
Figure 27: Battery ratings
• The batteries in most of the substations were in a general good condition. • There were no protective gloves in the battery room of Bighorn substation. • At Craighall substation, the switch for turning on the extraction fan in the
battery room was broken although the fan was working. • There was no eyewash in the battery room at Muldersvlei substation. The
batteries also require cleaning to remove the accumulating dust.
5.28. Tele control equipment
Figure 28: Tele control ratings
• The tele control equipment was in a general good condition in most of the
substations.
0
1
2
3
4
5
6
Ratin
gs
Substations
Batteries
0
1
2
3
4
5
6
Ratin
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Substations
Tele control equipment
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• Minor work is required on the cable trenches at Aurora substation. • The air condition in the tele control room was not working. Some lights were
also not working and some parts were not adequately illuminated. In addition, some cables were weeping compound.
• A number of panels were open in the tele control room at Muldersvlei. The air condition in the tele control room was also not working. Eskom staff advised that there was a programme to replace the air conditioning.
5.29. Control and Protection Panels
Figure 29: Control and protection panel ratings
• The control and protection panels in almost all the substations were in a good
condition. • The voltmeter on transformer No. 21 was not working at Bighorn substation.
5.30. Protection relays
Figure 30: Protection panel ratings
0
1
2
3
4
5
6
1 2 3 4 5 6 7 8
Ratin
gs
Substations
Control&Protection Panels
0
1
2
3
4
5
6
1 2 3 4 5 6 7 8
Ratin
gs
Substations
Protection relays
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• The protection relays at all the substations were in a general good condition. • Some substations have obsolete protection relays but they are still
operational.
5.31. Control Cables
Figure 31: Control cable ratings
• The control cables in all substations were in a general good condition.
5.32. Indoor Switchgear (No substations had indoor switchgear).
5.33. GIS Plant and bushings
Figure 33: GIS plant and bushings ratings
0
1
2
3
4
5
6
Ratin
gs
Substations
Control cables
0
1
2
3
4
5
6
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gs
Substations
GIS Plant & bushings
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• The GIS plant and bushings at Craighall substation were in very general good condition. There was no evidence of pollution or gas leaks in the GIS room.
6. ASSESSMENT OF DISSOLVED GAS ANALYSIS RESULTS
6.1. Introduction to DGA
The formation of gases in transformers (and other oil immersed equipment) can lead to catastrophic failure with major economic and safety risks. The formation of gases is attributable to two principal causes namely electrical disturbances and thermal decomposition. The cost of transformers is very high especially at transmission level, therefore the cost of monitoring of the transformer maintenance and the environment it operates in is justified when compared with the replacement cost and interruption in power supply. Transformer health can be monitored by assessing the gases generated in the transformer during the electrical breakdown of the insulating materials. It has been suggested that over 70% of transformer condition information is contained within the insulating fluid and that many transformer failures are attributable to manageable problems. The identity of the gases can be used to come up with preventive maintenance programmes. It is also important to note that the gas concentrations in the oil depend upon:
i. the volume of oil involved; ii. the age of the transformer; and iii. the type/use of the transformer e.g. generator or transmission, sealed or
free breathing.
The chemical composition assessment of these gases is known as Dissolved Gas Analysis (DGA) and Eskom provided a set of such results for five years (2009-2014) for the substations that were visited as part of the audit. The NERSA team also requested the oil management standard in transmission division (Unique identifier 41-966) which stipulated the procedure for the management of oil including tests such as the DGA.
6.2. Approach
The NERSA team assessed the DGA results based on the following parameters:
i. The 6-month interval routine sampling frequency for transformers and reactors as required by the oil management standard referred to above;
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ii. a comparison of the Eskom’s gas concentration alarm levels with the latest results for the seven gases (Hydrogen, Methane, Ethane, Ethylene, Acetylene, Carbon Monoxide and Carbon Dioxide) in at least 2 oil filled equipment for each substation namely transformers and/or reactors; and
iii. A comparison of the Eskom maximum gas concentration limits with
international benchmarks such as the Institute of Electrical and Electronic Engineers’ (IEEE) “Recommended Safe Fault Gas levels in Oil Immersed Equipment” and the Bureau of Reclamation in maximum parts per million – (ppm). The comparison of the gas concentration limits for the different fault gases are as shown in Table 7 below.
Table 7: Comparison of Eskom alarm levels with international standards for oil-immersed
equipment
It is evident from the above table that the Eskom gas limits are in line with the international benchmarks and will ensure that any fault gases trends are interpreted correctly. In some cases, the Eskom limits are more stringent than the international benchmarks.
6.3. Sample DGA analysis results for the substations
The DGA results were received for all the oil-immersed equipment such as transformers and reactors. However, the team selected two equipment per substation (except for Craighall and Poseidon where only one was chosen, and Luckhoff where there is no oil-immersed equipment) to analyse the frequency of sampling as well as the turn around times for sample sent to the laboratory for analysis. In addition, the levels of the seven gases referred to above were compared to the Eskom limits that would trigger an alarm to determine if there was an exceedance of the latter. The DGA results of the following power transformers/reactors in service were analysed: i. Aurora transformer No. 11;
ii. Aurora shunt reactor No. 1;
Gas Dornenburg IEEE Bureau Eskom Stritt of Reclam. Alarm
Hydrogen (H2) 200 100 500 150 Methane (CH4) 50 120 125 150 Ethane (C2H6) 35 65 75 100 Ethylene (C2H4) 80 50 175 100 Acetylene (C2H2) 5 35 7 15 Carbon Monoxide (CO) 500 350 750 750 Carbon Dioxide (CO2) 6 000 2 500 10 000 10000
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iii. Bighorn transformer No. 21;
iv. Bighorn transformer No. 1;
v. Craighall transformer No.2;
vi. Illovo transformer No.1;
vii. Muldersvlei transformer No. 3;
viii. Muldersvlei SVC transformer (Red phase);
ix. Poseidon transformer No.3;
x. Poseidon power reactor No.3;
xi. Sol transformer No. 11; and
xii. Sol transformer No. 4.
6.3.1. Frequency of Sampling Assessment
The assessment of the frequency of routine sampling of the oil-immersed equipment that is in service as discussed above was analysed and the observations are summarised in Table 8 below. Table 8: Summary of frequency of routine oil sampling from selected oil-immersed equipment
Oil Immersed Equipment Observations and Conclusions
Aurora transformer No. 11
• Sampling was done consistently at 6-month intervals as required by the standard.
Aurora shunt reactor No. 1
• Sampling was done consistently at 6-month intervals as required by the standard.
Bighorn transformer No. 21
• Sampling was not done consistently at times with sampling being done at 7-month intervals in 2010 and 2011. In addition, sampling results between December 2011 and October 2012 are not available.
Bighorn transformer No. 1
• Sampling of this transformer was done once in 2009 and 2010 in November and December respectively. Only in 2011 was sampling was done as required by the standard. Subsequently sampling was done once in October 2012 and after that no sample results were available. Eskom advised unit failed in April 2013 hence the missing results.
Craighall transformer No.2
• The sampling of this transformer was done consistently and during the same months of January and July annually.
Illovo transformer No.1 • Sampling was done consistently at 6-month intervals as required by the standard.
Illovo SVC transformer (Blue phase)
• Sampling was done consistently at 6-month intervals as required by the standard with minimal variations between the dates of sampling.
Muldersvlei transformer No. 3
• Sampling was done consistently at 6-month intervals (April and October) as required by the standard.
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Muldersvlei SVC transformer (Red phase)
• Sampling was done in line with standard in the majority of cases. Missing set of results between the period March 2013 and January 2014 were later provided by Eskom.
Poseidon transformer No.3
• There are no sampling results for the period February 2013 to 15 July 2014 but sampling was done consistently during the rest of the period under review.
Poseidon power reactor No.3
• Sampling was done consistently but there are no sampling results for the period 22 January and 17 January 2014 showing inconsistent sampling.
Sol transformer No. 11 • Sampling was done consistently at 6-month intervals as required by the standard.
Sol transformer No. 4 • In the majority of cases sampling was done consistently at 6-month intervals as required by the standard. However, there was one case between 2011 and 2012 where samples were taken over nine-month interval instead of six months.
6.3.2. Conclusions on frequency of sampling
Whilst not all the oil-immersed equipment DGA results were analysed, the sample shows that in the majority of cases, the 6-month routine sampling interval for in-service units was done as per the standard. However, there are several cases where inconsistent sampling is evident. The worst case is for Bighorn substation where sampling results are only available up to 2012 for one of the cases. The absence of these results poses a risk to the equipment concerned, as trends cannot be established on the level of dissolved gases. These trends are vital as they can be used to institute preventive maintenance measures that may mitigate the loss of the equipment and the consequences associated with the loss of such equipment. 6.3.3. Comparison of the different gas levels with Eskom alarm level
A comparison of Eskom’s gas concentration alarm levels with the latest results for the seven fault gases Hydrogen, Methane, Ethane, Ethylene, Acetylene, Carbon Monoxide, and Carbon Dioxide for the selected substations in Section 6.3 above, is summarised in the following section. Each gas concentration is plotted against the Eskom alarm level for that particular gas. It is important to note that the alarm level will signal an investigation by Eskom. The summary for the comparison of the actual levels at the time of the audit and the Eskom alarm level, for each of the gases, are as detailed below:
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i. Hydrogen
Figure 34: Comparison of Hydrogen gas levels
The sampling results for the hydrogen gas levels for all the selected oil-immersed equipment indicates that the levels are well below the threshold of 150ppm. No risk associated with hydrogen gas production is identified. Hydrogen is normally produced where there is arcing corona. ii. Methane
Figure 35: Comparison of Methane gas levels
284 7
45
10 0
337
30 279 0 0
150
020406080
100120140160
(ppm
)
Substation and Eskom Alarm Level
H2
6 3
215
109
0 0 0 2 20 4 2 0 14
150
0
50
100
150
200
250
(ppm
)
Substations and Eskom Alarm Level
CH4
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The methane gas levels for the majority of the oil-immersed equipment are below the threshold except for Bighorn transformer 21, which exceeded the 150-ppm level. This requires further investigation as it may indicate sparking within the transformer.
iii. Ethane
Figure 36: Comparison of Ethane gas levels
The sampling results for ethane gas levels for all the selected oil-immersed equipment indicates that the levels are significantly below the threshold of 100ppm. No risk associated with local overheating is therefore identified at this moment.
iv. Ethylene
Figure 37: Comparison of Ethylene gas levels
7 225
85
8 1 0 3
38
4 1 0 0
100
020406080
100120
(ppm
)
Substation and Eskom Alarm Level
C2H6
20 15 10 142 0 0 3 11 8 1 0 3
100
020406080
100120
(ppm
)
Substations and Eskom Alarm Level
C2H4
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The sampling results for ethylene gas levels for all the selected oil-immersed equipment indicates that the levels are significantly below the threshold of 100ppm. No risk associated with severe overheating is therefore identified at the moment.
v. Acetylene
Figure 38: Comparison of Acetylene gas levels
The sampling results for the acetylene gas levels for all the selected oil-immersed equipment indicates that the levels are significantly below the threshold of 15ppm. In some cases, no traces of the gas were detected. No risk associated with acetylene gas (typically arcing) production is present.
vi. Carbon monoxide
Figure 39: Comparison of Carbon monoxide gas levels
5
0 0 0 0 0 03
0 0 0 0 0
15
02468
10121416
(ppm
)
Substations and Eskom Alarm Level
C2H2
611
387
808 750
519375
190 178
471330
97250
496
750
0100200300400500600700800900
(ppm
)
Substation and Eskom Alarm Level
CO
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The threshold of 750ppm for carbon monoxide was not exceeded in most of the cases except for Bighorn transformer No. 21, which exceeded the alarm level marginally. The same transformer also exceeded the methane threshold and this warrants further investigation as per the oil management standard. Carbon monoxide production typically indicates severe overloading of the transformer.
vii. Carbon dioxide
Figure 40: Comparison of Carbon Dioxide gas levels
The graph clearly indicates that the carbon dioxide gas concentration levels for all the substations are well below the alarm level of 10000ppm. No risk of failure emanating from the production of carbon dioxide is therefore imminent.
6.3.4. Conclusions on DGA Results
The levels of dissolved gases in the sample of transformers and reactors were mostly under the Eskom alarm threshold. This indicates that the transformers or reactors are generally in good condition and at low risk of failure due to internal faults. However, there are few cases where the thresholds are exceeded especially transformer No. 21 at Bighorn substation. This is compounded by the fact that sampling was not done consistently.
7. SUBSTATION DOCUMENTATION AND MAINTENANCE
7.1. Documentation
Substation documentation was requested at each site and inspected. In most of the substations, the documentation was available for inspection and up to date. Single line diagrams for both the HV circuits, tele control equipment and protection schemes were also made available.
50074047
29334906
3584 3218 2334 31271037 1661 1037
2596 2596
10000
02000400060008000
1000012000
(ppm
)
Substation and Eskom Alarm Levels
CO2
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Records of infra-red scan results of the substation were also made available and inspected. The tests were done at intervals stated in the Eskom Standard for scanning of hotspots and reports were kept on site for further monitoring or repair where necessary.
However, the team identified the following issues at some of the substations related to documentation:
• Aurora substation - infra-red results for 2013 were not available when the audit was conducted. Eskom provided evidence that the tests had been done but the results were not kept on site as per Eskom Standard TS41-717. The standard requires that all records of infra-red scanning be kept in the substation for at least one year.
• Bighorn substation – some Permit to Work (PTW) forms are not
signed off and cleared by the Authorised Person when the work is completed.
• Craighall substation – a proper document filing system is required. • Illovo substation – the workers are not individually signing out once
the work has been completed. In some instances, the Authorised Person signs out on behalf of the workers while in other cases the workers sign out and the Authorised Person countersigns. Eskom undertook to consider revising the workers register form.
• Luckhoff substation – in some instances, battery tests sheet
originals were not removed and conveyed to the central office.
7.2. Plant Maintenance Performance
The team received the plant maintenance performance report based on inputs retrieved from the new SAP system. Most of the work was carried out as scheduled according to the work orders created in the system. Original Equipment Manufacturers’ (OEM) manuals were available at all the sites to enable the staff to refer to the manuals when carrying out maintenance inspections, tests and/or repair work on the equipment. Records of work orders for maintenance work to be carried out and done were also available and matched the other records such as the PTW , workers register, risk assessments and instructions from the controller.
In terms of pant maintenance performance for the 2014/15 financial year, the measure used by Eskom transmission is a comparison of the “all jobs completed Year to Date (YTD) % versus jobs issued YTD.” This compares the planned work logged into the SAP system against what is
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actually done over a defined period. It is important to note that the jobs carry the same weighting regardless of whether it is outage or non-outage dependant. The assessment is done per grid as well as for the overall transmission grid. The current annual target as set by Eskom transmission is 97% for both the individual grids and summated for the whole grid. As at 08 October 2014, out of a total of 21 958 jobs issued in the SAP system, 21 496 (representing 97.9% of the total) were completed spread across the 9 individual grids and Apollo as shown in the Table 9 below:
Table 9: YTD Eskom Transmission Maintenance Performance
The above performance is also depicted graphically below:
Figure 41: Summary Transmission Grid’s Performance
As can be seen from the graph, only three grids did not manage to reach the target of 97%. The three that failed to reach the target all performed above 96%, which is very close to the target.
The maintenance performance based on the planned vs actual maintenance indicates that Eskom transmission is executing the work as planned except in a few instances. Backlogs are also traced and recorded. In addition, the SAP information audit is audited for correctness of data, which guards against any possible errors intentional or otherwise.
Sept 2014 YTD Maintenance Performance Northern Cape Apollo CS Central East North North East Free State South West North West Tx GridJobs issued Sept 2014 YTD 1872 615 3503 3615 1654 4024 1642 1582 1730 1721 21958Jobs completed Sept 2014 YTD 1869 607 3387 3593 1636 3892 1630 1537 1665 1680 21496% jobs Completed 99.8% 98.7% 96.7% 99.4% 98.9% 96.7% 99.3% 97.2% 96.2% 97.6% 97.9%Target 97%
99.8%
98.7%
96.7%
99.4%98.9%
96.7%
99.3%
97.2%
96.2%
97.6% 97.9%
94.0%
95.0%
96.0%
97.0%
98.0%
99.0%
100.0%
101.0%
All j
obs
com
plet
ed Y
TD v
s Al
l job
s is
sued
YTD
(%)
Tx Grids Maintenance Completion Performance September 2014_15 YTD
% Completed Target
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The team noted the good plant maintenance performance while recommending that the findings of the audit be included in the maintenance and/or refurbishment plans of Eskom transmission if they have not been included already.
8. CONCLUSIONS
Detailed findings and recommendations of the audit for each Licensee are presented in the individual audit reports of the Licensee.
From the audit findings, the following conclusions are made:
(a) The licensee is fully aware of the requirements of the licence conditions and that of the South African Grid Code.
(b) Most of the equipment and plant in the substations is in a general good
condition, well maintained and tidy. (c) The transmission grid is to a large extent being operated according to
the procedures derived from the requirements of the Grid Code. (d) The overall substation ratings (based on the average of the equipment
ratings for each substation) indicate that the substations are in a general good condition as shown below in Figure 42 below:
Figure 42: Overall Substation Condition Ratings
4.42 4.48 4.52 4.54.85
4.174.8 4.61
0
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4
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6
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Substation
Overall Substation Condition Ratings
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