Ground fault Current of Chiller feeder

[mohsan514]

Gotcha! Your cable layout is not the optimal arrangement for flat multi-cable runs. Here is the proper arrangement:
View attachment 2560020Or you could arrange your cables in A1B1C1 A2B2C2 A3B3C3 with intra-phase spacings of 2 cable diameters apart, cable groups (1 to 2 and 2 to 3) with 3 cable diameters apart. But definitely not the way you did as shown in your sketch.
Hope that helps!

Is this reason for Ground Fault Current???

 

[topgone]

Is this reason for Ground Fault Current???

You don't have a neutral and therefore any imbalance current produced by the vectorial sum of the fluxes around the cables will have to go somewhere. Please review how your breakers' GF protection element determines the "ground current" that will be compared to its GF settings.

 

[synchro]

We have checked the phase current with another Meter , It is same as shown in breaker display. But for Ig we could not verify from another instrument.

Perhaps the main circuit breaker itself is defective. Was the ground fault protection of the main breaker working OK with other equipment before installation of the chiller, or was the main breaker also newly installed?

This is a wild guess, but if it's a new breaker maybe the polarity of one of the CTs on each phase inside the breaker has its polarity reversed (assuming that this is physically possible in the breaker design). A reversed CT on one of the phases would produce an indicated residual GF current just like you are seeing. For example, if all of the phase currents were 350A then a reversed CT output would not cancel out the vector sum of the other two CT outputs, but instead it would add to it. And so the indicated GF current would be 350A + 350A = 700A.

 

[zbang]

One of the prime rules of troubleshooting is not to trust a single thing until proven. You've checked the breaker's readings of the phase currents but not that of the supposed ground current. Without actually measuring that, you're trusting an unproven device which could very well be wrong.

There are a couple of options- measure the actual current on the grounding conductor (difficult), measure the "zero-sequence" current on all the phase leads (mentioned earlier), or have the breaker properly tested. Only then will you know if it's a real problem or an imagined one inside the breaker. You could also swap the breakers between machines but that takes both out of service for a while.

One other thought- is the breaker actually measuring that ground current or calculating it? I'd be extremely surprised if there was only one grounding path (a wire) from a machine with lots of pipe connected, so the breaker is probably (wrongly) calculating that current.

What's model # of the breaker? Folks here like to look up the data sheets and manuals.