Isolating a Ground Fault

[Machiavelli999]

We have a lighting panel that has had several cases of tripping the breaker in the distribution panel upstream that feeds it. One time the fault propagated to the distribution main which has a trip unit that tells us the fault was a ground fault.

We are going to replace the panel and rerun the wiring to the lighting since the panel is old and there could be wiring issues such as crossed neutrals that we hope to fix. However, it was proposed, that since we are replacing the panel, the new panel have GFI breakers on every branch circuit. So that if the problem occurs again, we can isolate it.

I thought that this was excessive, but if we were to do it, is there any other way to locate the ground fault? Could a ground fault device be put on the main that could at least tell us what phase the ground fault occurred on. My research so far hasn't produced anything. I know Schneider offers a breaker equipped with an Earth Leakage Module but I think that's just a standard GF breaker that you could set at differential down to 30 mA. I don't think there is anything else besides putting ground fault relays on each branch circuit to isolate the problem.

 

[Jraef]

We have a lighting panel that has had several cases of tripping the breaker in the distribution panel upstream that feeds it. One time the fault propagated to the distribution main which has a trip unit that tells us the fault was a ground fault.

We are going to replace the panel and rerun the wiring to the lighting since the panel is old and there could be wiring issues such as crossed neutrals that we hope to fix. However, it was proposed, that since we are replacing the panel, the new panel have GFI breakers on every branch circuit. So that if the problem occurs again, we can isolate it.

I thought that this was excessive, but if we were to do it, is there any other way to locate the ground fault? Could a ground fault device be put on the main that could at least tell us what phase the ground fault occurred on. My research so far hasn't produced anything. I know Schneider offers a breaker equipped with an Earth Leakage Module but I think that's just a standard GF breaker that you could set at differential down to 30 mA. I don't think there is anything else besides putting ground fault relays on each branch circuit to isolate the problem.

There isn't any kind of GF main breaker or device that could discern which branch below it has the GF event. There are GF locators, but they are REALLY expensive.

Are all of the branch breakers in the lighting panel the same size? If so, buy ONE GF breaker and install it in one circuit at a time, until the GF event is detected by THAT breaker, not the one ahead of it. It's a little tiresome, but it would cost less than buying a bunch of GF breakers.
Similarly, or if the branches are all different sizes, you could add a portable GF protector on the load side of each breaker and do the same sort of thing, one at a time.

 

[don_resqcapt19]

Disconnect all of the grounded and ungrounded conductors at the lighting panel, cap off and isolate the grounded conductors (neutrals) and megger the ungrounded conductors. This will often tell you what branch circuit is causing the trip. This is assuming that it is a branch circuit that is causing the trip. You could also isolate the panel feeder conductors and megger them to see if they are the cause.

 

[augie47]

IMO, changing out the panel will not necessarily prevent a feeder breaker from opening due to a ground fault on a branch circuit.
A coordination study by an engineer who will look at specific breaker details might be in order if you really want to reduce this occurrence.