Generator Farm question

[ruggedscot]

I wonder if anyone out there could advise on this one -

Scenario Generator farm consisting of several diesels - these feed a diesel marshalling board fitted with ACB's.
Each gen set feeds an ACB which connects to a bus. The Bus then connects to several ACB's that feed the connected loads through interlocked ACB's for utility / generator selection.

Now comes the tricky bit - I would have thought that the generator marshalling board should have seen and tripped out before the fault rippled through, what happened was that there was a failure on one of the changeover ACB's this resulted in the possible back feeding of the utility company supply and the shut down of all the generators. Should the ACB on the generator board not have seen the fault and opened before the generators tripped on overcurrent?

Maybe the generators went out on reverse power, as of yet Ive not gotten fully into the prognosis of the incident but it is one that worried me and has me thinking that our protection may not be set up as good as what it should be.

The more that I think about it the more that I think that if we had a cable fault then the system would have opened the ACB feeding it but as there was an alternative power source involved this is what caused the breakdown in descrimination.

Has anyone ever encountered such a scenario before ?

 

[davidbeach]

ruggedscot, you would need to provide a whole lot more information before anybody could begin to speculate on what happened. Could you draw a one-line diagram and post it? What controls the ACB (air circuit breaker?) and how is it set? Lots and lots of other things.

 

[rbulsara]

Post all relay flags that showed up and their location(which breaker) in addition to what david asked.