Isolating A Disconnecting Circuit Breaker Using Live Line Working On A 132kV HV Indoor Substation

By Chris Dodds on 21st June, 2013

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Isolating A Disconnecting Circuit Breaker Using Live Line Working On A 132kV HV Indoor Substation

This ABB video shows the live removal of a link to a disconnecting circuit breaker in a 132kV high voltage indoor substation - this is done to enable the maintenance of a disconnecting circuit breaker without taking the line out of service.

This is NOT an instructive video to show how this type of work is done.

As it becomes more and more common with live working, performed by special trained staff, the question has been raised if it is possible to use the manual links in the DCB-design for live working.

In a plant taken into service, a test was performed, where a DCB first was linked off from the live switchgear and then reconnected. The test was documented in this video film.

Important Notice

This is carried out by the national distribution company in Sweden, thus following all applicable laws and regulation. Regarding PPE (Personal Protective Equipment), the maintenance crew strictly follows the rules and regulations set for this kind of work, which includes the equipment used. All safety procedures are not shown in this video.
 

LinkedIn Discussion Comments July 2013

Tex Gamvrelis, P.Eng. • Very good video by ABB. At 3:50 and 5:25, I was thankful to have a desk job. I will never take the maintenance personnel for granted again. How often can this procedure be repeated before the connections have to be replaced?

Rob Maitland-Stuart • Answers one of the concerns I've always had re the isolation of DCB's, but a good question from Tex re the long term arc damage between the connecting terminal interfaces, bearing in mind that the need frequency to isolate the DCB should be fairly low.

Richard Thomas • As indicated by Rob Maitland-Stuart, the frequency that this sort of procedure should be necessary should be very low. For line and transformer bay DCBs that typically operate infrequently the interval between recommended maintenances is 15 years, which is still 3 to 4 times longer than the typical maintenance intervals of HV air disconnectors.

Disconnectors that would be connected to the busbar would require a full busbar outage, which is what can be avoided by using DCB with disconnecting links and live line working (But please note the safety notices on the video and further comments below!).

Nevertheless, when you look at the video closely one can see that the arcing typically occurs at the ends of the connection points which is away from the the final main contact areas on the busbar and the connection clamp and as such any arcing "wear" on these surfaces is minimal and should not impact on the proper function of the clamped connection.

If a customer had concerns on the integrity of the clamped connections, it is possible to use a thermal imaging camera to check that none of the connections exceeds the recommended / standard operating temperature limits under nominal / rated load current.

Using a thermal imaging camera in this way can be done from a safe distance while the equipment is energised.

It is important to note that this sort of live line work shall ONLY be carried out by specially trained personnel with the appropriate personal protective equipment and tools, according to the relevant safety regulations and laws.

(Of course all work on HV equipment, should only be performed by suitably trained / certified personnel with appropriate safety equipment and following relevant safety regulations).

Live line working is only one option and not compulsory. If a user is prepared to accept a short busbar outage for the rare times DCB maintenance can be needed, then the disconnect links could still be used to disconnect and reconnect the DCB in a shorter time than the total outage time needed on the busbar for accessing and maintaining an HV air disconnector in a similar location.

Richard Thomas, Global Product Manager, ABB

  • Further reading

Switchgear Temperature Monitoring - Hot-Spot Detection Enabling Condition-Based Maintenance

ABB CMF High Voltage Motor Fuses -7.2kV Rated Voltage 100A/200A 

ABB MWK High Voltage Surge Arresters AC 4-44kV

ABB Medium Voltage Power Products

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