Breaker trip after Sync following ACB retrofit
Breaker trip after Sync following ACB retrofit
(OP)
I am on an offshore oil production platform. We have a 440V Diesel gen set running in island mode, supplying an emergency sw board. We attempted to auto sync our normal 440v power board fed from GT alternators through an intertie breaker
Normally the intertie ACB breaker closes at sync and the Emergency generator incomer ACB breaker opens normally after 2 secs. However, the intertie ACB closed and after a short delay (~2 sec) the Emergency generator ACB tripped on G Protection with fault current Ig = 675A. The intertie breaker stayed close, so we did not lose power to the em board
This is since we replaced the incomer ACB with a new modern breaker supposed to be like for like and all protection settings the same
There is no genuine earth fault as gen was running fine for a couple of days on own
The emergency incomer breaker is an ABB 3P emax 2 with neutral sensor replacing an obsolete emax breaker with neutral sensors
we are all baffled why the trip occurred, we don't believe there was a sync issue
any thoughts?
Normally the intertie ACB breaker closes at sync and the Emergency generator incomer ACB breaker opens normally after 2 secs. However, the intertie ACB closed and after a short delay (~2 sec) the Emergency generator ACB tripped on G Protection with fault current Ig = 675A. The intertie breaker stayed close, so we did not lose power to the em board
This is since we replaced the incomer ACB with a new modern breaker supposed to be like for like and all protection settings the same

There is no genuine earth fault as gen was running fine for a couple of days on own
The emergency incomer breaker is an ABB 3P emax 2 with neutral sensor replacing an obsolete emax breaker with neutral sensors
we are all baffled why the trip occurred, we don't believe there was a sync issue
any thoughts?
RE: Breaker trip after Sync following ACB retrofit
RE: Breaker trip after Sync following ACB retrofit
Is the phase sequence verified with new ACB?
How are the new ACB opening & closing times compare with those of old ACB?
If the above are ruled out, then we may have to suspect the generator protection and test it.
What is the relay type & model? Guess the relay takes all three phase current inputs for summing up vectorially to get Ig or does it use neutral CT current signal?
RE: Breaker trip after Sync following ACB retrofit
Muthu
www.edison.co.in
RE: Breaker trip after Sync following ACB retrofit
The transformer incomers were fitted first last week, and the one supplying the RHS Bus tripped on ground fault during sync. This left the Em Gen running in island mode. Now that the Em gen incomer has been replaced this is tripping first as the settings are lower.
I agree that the fault must be with the new breakers, but our main board runs with the two new incomers with no issue, only tripped when syncing with the DG. That would mean two breakers each having reversed CTs. The breakers were also fitted by ABB engineers. So maybe it will be a case of revised protection settings
I will feedback these comments, it will be interesting to see what our onshore support team comes up with, if anything soon. In the meantime, I will not be carrying out any loaded test runs with the DG