600 V transformer protection
600 V transformer protection
(OP)
HI Guys,
I am an electrical engineer in Canada working on a 600V distribution system. CSA standards are applicable.
I have to size/set breakers that protect a 600V/208V transformer Dyn1 50kVA (In=48A at 600V)
For now, my predecesor choose a primary side molded case breaker of 125% In so 60A breaker with no ajustement. At secondary side, i have a 225A Low voltage panel loaded at 27.772kW (77A at 208V) protected by a 300A LSI breaker ajust to 125%In=173A.
As both breakers are adjust at 125%In, i have a bad protection coordination (TCC curve).
Do you any suggestions ?
I am an electrical engineer in Canada working on a 600V distribution system. CSA standards are applicable.
I have to size/set breakers that protect a 600V/208V transformer Dyn1 50kVA (In=48A at 600V)
For now, my predecesor choose a primary side molded case breaker of 125% In so 60A breaker with no ajustement. At secondary side, i have a 225A Low voltage panel loaded at 27.772kW (77A at 208V) protected by a 300A LSI breaker ajust to 125%In=173A.
As both breakers are adjust at 125%In, i have a bad protection coordination (TCC curve).
Do you any suggestions ?






RE: 600 V transformer protection
Molded case circuit breakers in series are generally not going to fully coordinate because of the instantaneous trip elements.
RE: 600 V transformer protection
Bill
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"Why not the best?"
Jimmy Carter
RE: 600 V transformer protection
RE: 600 V transformer protection
To fit all the curves in, there sometimes needs to be a compromise, and it is normally at the transformer.
It is difficult to say if this is the case with your situation - but it is possible.
Plotting the tcc curves for the protection above the 600V breaker may indicate why the protection is set the way it is.