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Hi Discop, Thanks for your comments, I never thought about the risk of fault current passing through the closed breaker ground loops, but that is very interesting, another reason to isolate the CT's! Cheers

Hey Palletjack, the paper describes a slightly different scenario than the one I am describing. In our case the breaker is not bypassed, it would be switched out of service, ie, the breaker disconnect switches would be opened and the breaker terminals would be grounded at both sides. So there...

Thank you for the replies retriever & Palletjack, pretty much confirms what I was thinking. Unfortunately there was no event to go off of, one where I can analyze relay records. It's interesting how Protection folks (engineers and the like) kind of have a blind spot to what the maintenance crews...

We use HADs (Heat Activated Devices), depending on how big the xmfr, we could use up to 6 or 8 of them place strategically around the tank.

I just realized in my eq circuit diagram, my Zoc should equal to R // jXm not R + jXm. my bad

Just wondering if anyone on here has thought about this scenario playing out. When our maintenance crews perform routine maintenance on HV circuit breakers, they typically throw up safety grounds on the HV drops to guarantee the equipment de-energized. The CT circuits remain in service. If the...

I work for a large electrical utility and I have never seen the start point of the CT's not formed in the equipment mech box.