AC current in the protective earth of power transformers
AC current in the protective earth of power transformers
(OP)
We measured an AC current - in the order of tenth Amps - flowing in the protective earth of large scale step up power transformers.What might be the source of this current?
Thanks everybody
Thanks everybody





RE: AC current in the protective earth of power transformers
Bill
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"Why not the best?"
Jimmy Carter
RE: AC current in the protective earth of power transformers
Some years back, I came across a pretty large rectifier transformer in an aluminum plant where the tank current to earth was the order of 800 A !One out of two earth links to ground was removed to bring down this current to the order of 300 A.
RE: AC current in the protective earth of power transformers
I have seen a lot of transformers where there did not seem to be excess current to ground. Is this an issue with three legged cores and unbalanced voltages?
I am under the impression that the open circuit voltage caused by capacitive coupling is quite high, but that the current is limited by the reletively high source impedance of the capacitive effect.
From your numbers I suspect that the open circuit voltage of flux induced currents is quite low but the source impedance is quite low.
From the OP, I took the current to be less than an Amp (tenths, not tens) which is consistent with capacitive leakage currents.
Comments?
Bill
--------------------
"Why not the best?"
Jimmy Carter