Current on the ground of 600VAC disconnect.

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djtazjr

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I was wondering about grounding (EGC) of a transformer and the disconnect of the line side (primary) feeder to the transformer. I came across the job that has lots of problems with the service. A 800amp service rated transfer switch was installed recently with an electronic GFCI breaker for both generator and utility. The breaker trips when the transfer back to utility occurs. Now I know why this happens and have done plenty of digging for the service to find that the transformers and disconnects are not properly grounded (GEC) or bonder either with a jumper or metal cases.

As said the feeders for the transformers primary come from a Main Distribution Panel with a EGC with them. The ground is attached to XO on all transformers down stream. The EGC shouldn't have been run with the feeders or is need to be connected to the transformer cases?

Someone?
 
I'm pretty sure that 600vac services are of the ungrounded type, bonding of all metal

parts of the electricial system is still required. Why was there GFP installed on the 800a

service in the first place ?
 
djtazjr said:
I. A 800amp service rated transfer switch was installed recently with an electronic GFCI breaker for both generator and utility.
Click to expand...

GFCI on a main circuit breaker or GFP Ground Fault Protection?


The breaker trips when the transfer back to utility occurs. Now I know why this happens and have done plenty of digging for the service to find that the transformers and disconnects are not properly grounded (GEC) or bonder either with a jumper or metal cases.
Click to expand...

Transfers back to utility generally are an out of phase issue (if the transfer switch transfers fast with no in phase monitor).

WHAT TYPE OF ATS?

The other issue would be circulating ground current.

What type of ATS 3 or 4 pole?
Is the generator grounded as well as the main service (generator treated as SDS)?
Was a coordination study done?
Based upon 600 VAC I assume you have several transformers being fed from these two sources?
 
Let me qualify my statement:

It is a 400Amp deconnect that has current of the GEC and a 800 amp 480 volt Transfer switch with Ground Fault Protection.
 
Oh, 480v. Yes the EGC must be run with the feeders to the transformer(s) and yes, it will

find its' way to the XO terminal, and yes that is the way it is done in many, many installs.

Each transformer should also have a grounding electrode conductor run to an available

electrode close by.
 
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