Generator Breaker

[shlim]

Hi there, this is my first posting since I subscribed to Eng-Tips.

I have attended a generator failure in a diesel driven power plant. According to the plant, there had been multiple tries to sync this particular Gen to the grid. After replacing a few electronics component, the Gen still failed to sync. Lastly, they decided to swap gen breaker from another unit. The operator claimed that during the process, he had mistakenly switch to close the breaker's contacts, closing to generator to the grid, instead of switching from 'local' to 'remote' (in order for the control room to take control).

My question is, it possible that the operator can closed the breaker 'locally' from the control switch at the front of the VCB cubicle? My understanding is there should be a sort of protection relay to prevent the breaker from closing if the Gen had not meet synchronization criteria.

Thank you.

 

[odlanor]

DTR2011,
This protection do not close or avoid close breaker; it opens breaker after wrong synchronization.

 

[veritas]

shlim

I have just recently completed a synch project design where an interlock was programmed into the relay preventing local closure of the cb. By local I mean operation at the specific panel on the switchboard. A relay output contact was in series with the cb closing coil. When in local mode, relay contact closure is prohibited. Relay implemented as a safety precaution for the unsuspecting (or suspecting) operator.

 

[shlim]

Thanks guys, I now understand that while cb can be closed locally, the system should have incorporated a synch-check protection relay which purpose is to prevent unauthorized cb closing (eg. operator error, sabotage, not in synch) as a safety measurement.

 

[racookpe1978]

That is what I was trying to get at: A "local operator" SHOULD BE prevented from making mistakes (either deliberately or accidentally); but the local control operation often voids many fail-safe preventions and protections that are in place when the breaker is operated "normally" from the control room.