Transmission Perspective on Maintenance - Asea … 2009...Eskom Transmission’s Current Perspective...

Eskom Transmission’s Current

Perspective On Power

Transformer and Shunt Reactor

Maintenance

Eskom Transmission’s Current Eskom Transmission’s Current

Perspective On Power Perspective On Power

Transformer and Shunt Reactor Transformer and Shunt Reactor

MaintenanceMaintenance

Compiled and presented by

Sidwell Mtetwa (Pr. Eng)

ContentsContentsContents

• Definitions

• Transmission Network Overview

• Challenges

• Strategies

• Summary

• Definitions

• Transmission Network Overview

• Challenges

• Strategies

• Summary

“The days of our lives are seventy years; and if by

reason of strength they are eighty years, Yet their

boast is only labour and sorrow; For it is soon cut off

and we fly away.”

““The days of our lives are seventy years; and if by The days of our lives are seventy years; and if by

reason of strength they are eighty years, Yet their reason of strength they are eighty years, Yet their

boast is only labour and sorrow; For it is soon cut off boast is only labour and sorrow; For it is soon cut off

and we fly away.”and we fly away.”

Psalms 91:10Psalms 91:10

Life is finite, no matter what.

“The days of our lives are forty years; and if by reason

of good maintenance they are fifty years, Yet their

significance is only availability and outage; For it is

soon cut off and we are scrapped.”

““The days of our lives are forty years; and if by reason The days of our lives are forty years; and if by reason

of good maintenance they are fifty years, Yet their of good maintenance they are fifty years, Yet their

significance is only availability and outage; For it is significance is only availability and outage; For it is

soon cut off and we are scrapped.”soon cut off and we are scrapped.”

Life Cycle Management PlanLife Cycle Management Plan

DefinitionsDefinitionsDefinitions

Maintenance

• The act of keeping an asset in good condition to perform efficiently and safely the service for which it is used.

Maintenance Philosophy

• What action to do and when to do it

TMP – Transmission’s Maintenance Philosophy

Maintenance

• The act of keeping an asset in good condition to perform efficiently and safely the service for which it is used.

Maintenance Philosophy

• What action to do and when to do it

TMP – Transmission’s Maintenance Philosophy

Transmission Network’s OverviewTransmission Network’s OverviewTransmission Network’s Overview

• Transmission has 155 substations with an incoming

voltage of either 132, 220, 275, 400 or 765 kV

• Substations are grouped in 8 grids / regions

• There are 510 Power Transformers ( >125GVA)

• 135 additional transformers planned ( installed by

2017)

• The present average age of this transformer fleet is

28 years

• Transmission has 155 substations with an incoming

voltage of either 132, 220, 275, 400 or 765 kV

• Substations are grouped in 8 grids / regions

• There are 510 Power Transformers ( >125GVA)

• 135 additional transformers planned ( installed by

2017)

• The present average age of this transformer fleet is

28 years


• About 80 Shunt Reactors (> 7 GVAr)

• 45 additional shunt reactors required by 2017

• The average age of Transmission’s reactor fleet is

24 years

• 33 different OEMs for transformers and reactors

• 21 different tap changer OEMs

• About 80 Shunt Reactors (> 7 GVAr)

• 45 additional shunt reactors required by 2017

• The average age of Transmission’s reactor fleet is

24 years

• 33 different OEMs for transformers and reactors

• 21 different tap changer OEMs


Transmission Tapchangers By Make

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Fu ller

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Series1

TMP - ChallengesTMP TMP -- ChallengesChallenges

1. Unavailability of plant for long outages.

• Maintenance engineers – ensure LTPH and

safety.

• Plant operators – security of supply and safety.

2. In carrying out maintenance

– Not enough time.

– Lack of skilled people – risk of further outage

– Lack of OEM support on certain old makes

1. Unavailability of plant for long outages.

• Maintenance engineers – ensure LTPH and

safety.

• Plant operators – security of supply and safety.

2. In carrying out maintenance

– Not enough time.

– Lack of skilled people – risk of further outage

– Lack of OEM support on certain old makes


3. On line processes are insufficient to keep the

plant in service for very long time. Offline

interventions are needed

3. On line processes are insufficient to keep the

plant in service for very long time. Offline

interventions are needed

TMP – Plant AvailabilityTMP TMP –– Plant AvailabilityPlant Availability

• Network was built with redundancy

• Economic growth exceeded the expectations

• Redundancy no longer existing in some

substations

• During outage – increased risk of failure

(loading / age)

• Some units have conditional avail ability

(fixed tap pos.)

• Network was built with redundancy

• Economic growth exceeded the expectations

• Redundancy no longer existing in some

substations

• During outage – increased risk of failure

(loading / age)

• Some units have conditional avail ability

(fixed tap pos.)

TMP - SkillsTMP TMP -- SkillsSkills

• Skills are becoming harder to mature and to

retain

• OEM training is expensive (overseas)

• Lack of extensive exposure after training

• OEM trained staff are quickly recruited in the

private sector

• Skills are becoming harder to mature and to

retain

• OEM training is expensive (overseas)

• Lack of extensive exposure after training

• OEM trained staff are quickly recruited in the

private sector

TMP – SkillsTMP TMP –– SkillsSkills

• Staff not trained by OEM’s, performing intrusive

work - risk of failure

• Wide spectrum of types installed in the network

• OEMs are no longer in business

• OEMs still in business - designs were

discontinued

• Staff not trained by OEM’s, performing intrusive

work - risk of failure

• Wide spectrum of types installed in the network

• OEMs are no longer in business

• OEMs still in business - designs were

discontinued

Incident No.1 – Near MissIncident No.1 Incident No.1 –– Near MissNear Miss

• A 15MVA 132/33kV transformer was taken out of service

for a scheduled tap changer maintenance during a

weekend. When the maintenance was completed, the

transformer was re-commissioned and put back on load.

Minutes after taking load, smoke was seen coming out of

the diverter chamber of the transformer.

• The investigation revealed that the transition resistors

were heating the oil, because the resistors were

continually in the circuit due to incorrect wiring.

• A 15MVA 132/33kV transformer was taken out of service

for a scheduled tap changer maintenance during a

weekend. When the maintenance was completed, the

transformer was re-commissioned and put back on load.

Minutes after taking load, smoke was seen coming out of

the diverter chamber of the transformer.

• The investigation revealed that the transition resistors

were heating the oil, because the resistors were

continually in the circuit due to incorrect wiring.

Incident No.2 – Reduced CapabilityIncident No.2 Incident No.2 –– Reduced CapabilityReduced Capability

• A 500MVA 275/132/22kV autotransformer was taken out of service for a scheduled tap changer maintenance over a

weekend. This transformer had a design where the diverter is

physically sitting on top of the 132kV bushing. During

inspection, problems were identified on the diverter switches.

• Instead of removing only the diverter switch, the contractor

removed the complete set of bushing and diverter. In attempting to re-install, the equipment was mishandled and the bushing got

damaged. No spares could be found for this old design.

• The transformer was then modified to run on a fixed tap

position.

• A 500MVA 275/132/22kV autotransformer was taken out of service for a scheduled tap changer maintenance over a

weekend. This transformer had a design where the diverter is

physically sitting on top of the 132kV bushing. During

inspection, problems were identified on the diverter switches.

• Instead of removing only the diverter switch, the contractor

removed the complete set of bushing and diverter. In attempting to re-install, the equipment was mishandled and the bushing got

damaged. No spares could be found for this old design.

• The transformer was then modified to run on a fixed tap

position.

Incident No.3 Incident No.3 Incident No.3

A 145MVAr 765kV Shunt reactor was taken out of

service for maintenance. A person supposed to

clean the pressure relief valve removed the PRV

and oil gushed out.

A 145MVAr 765kV Shunt reactor was taken out of

service for maintenance. A person supposed to

clean the pressure relief valve removed the PRV

and oil gushed out.


• All these bring about a complex situation and

Transmission has to manage it for continuity of supply.

• If maintenance is correctly/timeously done – benefits

• If maintenance is incorrectly/not done - consequences

• All these bring about a complex situation and

Transmission has to manage it for continuity of supply.

• If maintenance is correctly/timeously done – benefits

• If maintenance is incorrectly/not done - consequences


Eskom Transmission considers precise

maintenance philosophy combined with proper

strategies is the key in managing all these

challenges

Eskom Transmission considers precise

maintenance philosophy combined with proper

strategies is the key in managing all these

challenges

TMP - StrategiesTMP TMP -- StrategiesStrategies

Transmission maintenance philosophy is built with the following strategies

1. Specify and use low maintenance technologies

• Vacuum tap changers – 300 000 ops

• Welded main covers – no gasket leaks

• RIP bushings – no bushing oil leaks

• Online dryers – preserve paper insulation

• Conservator air bags – eliminate oil oxidation.

Transmission maintenance philosophy is built with the following strategies

1. Specify and use low maintenance technologies

• Vacuum tap changers – 300 000 ops

• Welded main covers – no gasket leaks

• RIP bushings – no bushing oil leaks

• Online dryers – preserve paper insulation

• Conservator air bags – eliminate oil oxidation.


Oil tap

Conservator with air bag


RIP bushings with SiR sheds OIP bushing with porcelain sheds


Oil leak on main lid gasket On line moisture remover


2. Maintenance - as per OEM instruction or 6 yearly

(synchronized with breaker maintenance)

3. Only accredited persons to do intrusive work.

4. Only people trained by OEMs and have post

training experience are accredited

2. Maintenance - as per OEM instruction or 6 yearly

(synchronized with breaker maintenance)

3. Only accredited persons to do intrusive work.

4. Only people trained by OEMs and have post

training experience are accredited


5. Standardizing on components e.g. tap changers (difficult to keep spares for all types)

6. Repair non OEM supported units using existing classical supplier for parts or use local suppliers

7. Detailed and frequent inspections

8. Inspection and maintenance records are kept in an electronic database

5. Standardizing on components e.g. tap changers (difficult to keep spares for all types)

6. Repair non OEM supported units using existing classical supplier for parts or use local suppliers

7. Detailed and frequent inspections

8. Inspection and maintenance records are kept in an electronic database


Experience has shown us that only OEM trained

technicians with suitable post training experience

can be accredited to perform intrusive

maintenance

Experience has shown us that only OEM trained

technicians with suitable post training experience

can be accredited to perform intrusive

maintenance

SummarySummarySummary

• Asset reliability is a function of maintenance

• Transmission’s challenges with maintenance are

– Non availability of plant for outage

– Scarcity of skilled people

– Many OEMs are no longer in business – no spares

– Some old designs have been discontinued –no support

– Wide spectrum of component types

• Asset reliability is a function of maintenance

• Transmission’s challenges with maintenance are

– Non availability of plant for outage

– Scarcity of skilled people

– Many OEMs are no longer in business – no spares

– Some old designs have been discontinued –no support

– Wide spectrum of component types

SummarySummarySummary• Strategies that have been developed are

– Use of no / low maintenance technologies

– Maintenance as per OEM instruction or 6 yearly

– Only accredited technicians to do intrusive work.

– Only people trained by OEMs and have post training

experience are accredited

– Standardizing on components like tap changers

– Get specs and manufacture components locally – quality

risk. Else do modifications

• Strategies that have been developed are

– Use of no / low maintenance technologies

– Maintenance as per OEM instruction or 6 yearly

– Only accredited technicians to do intrusive work.

– Only people trained by OEMs and have post training

experience are accredited

– Standardizing on components like tap changers

– Get specs and manufacture components locally – quality

risk. Else do modifications

Maintenance CategoriesMaintenance CategoriesMaintenance Categories

• Transmission maintenance is categorized in

three types

1. Short term maintenance

2. Medium term maintenance

3. Long term maintenance

• Transmission maintenance is categorized in

three types

1. Short term maintenance

2. Medium term maintenance

3. Long term maintenance

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Questions and Comments

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Questions and Comments

Transmission Perspective on Maintenance - Asea … 2009...Eskom Transmission’s Current Perspective...

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