138KV HLR ABB Breaker Fault Clearing Time

Commonly, overcurrent relays have an inverse time characteristic. Relay takes longer to operate if fault current is smaller according to a designed curve.

Was the fault an actual fault? In that case you may not know the fault current. Maybe fault location allows an estimate.

Also breakers may take several cycles after contact separation to stop all current on a heavy fault.

Or was it a simulated fault. In that case the current must be drawn on the relay curve to find expected operate time.

If your breaker is at power source, relay will necessarily have longer delay, to allow a succession of downstream relays & breakers to operate first - so relay operate time is longer than breaker operation time.

Remanent flux depends on previous breaks - if last break was on positive current, you have no influence, for example, on the next break being positive or negative half cycle or on remanent flux reappearing.

As pointed out by others , tripping of breaker under fault conditions depends on relay characteristics and master trip relay time and breaker trip time.

While maintenance check , probably you would have direct trip command with out any relay in the circuit.

Hence the difference.

Remove the guano from it?

What did ABB have to say in response to the telephone calls that have already been made for help?

Clearing a fault includes the time to interrupt the flow of current across the breaker contacts. This is a function of the breaker, an air breaker will take longer than a vacuum breaker, for instance, because you have to cool and extinguish the arc.

You need to know this to coordinate upstream and downstream devices. You have the response of your protective relay, the time it takes to release the trip mechanism of your breaker, the time it takes for the contacts to physically separate to the design interrupting distance, and the time it takes to extinguish the arc, stopping the current flow.

Total clearing time would be at the design rating of the circuit breaker, a smaller fault should clear sooner, but you need to design your coordination for worst case.