22 kV Express Feeder Master Trip Relay Contacts got burnt: Corrective Action taken

On 08.12.2023 Friday, Outage was taken on 22 kV Express Feeder.

While taking Relay through trip trials, Master Trip Relay Areva Type VAJ coil 1 contacts got burnt.

Being an express feeder, there is not much tripping and hardly one outage a year.

Due to non-operation of the breaker, the Breaker mechanism is not smooth and so while taking the trip trial, Breaker may have taken longer time to trip and so current through the trip relay contacts was for a longer period, which may have damaged the contacts.

There are 2 Operating Coils in the Master Trip Relay, so if one gets damaged, we can use the other one.

So we shifted the wiring from Coil 1 to Coil 2 and bypassed the Coil 1.

For feeders like Express feeders or EHV Consumers, since there are not many shutdowns or trippings, there are not many operations of the Breaker and the Breaker mechanism gets sluggish.

So when we Trip the Breaker, the Master Trip Relay or the Tripping Coil may get damaged, as current flows through them for a longer period, as the Breaker takes longer time to trip.

Remedial Action:

When tripping the Breaker after a very long time, it is advisable to Trip the Breaker Mechanically instead of Electrically.
Once the Breaker Mechanism is made free after Mechanical Trials, then the Breaker can be Closed/Tripped Electrically.