question

msandrew avatar image
msandrew asked

Autotransformer (100A) w/ground leak

Am experiencing .5A on my unit’s ground conductor. Ground relay is not being used. I would think this is not supposed to happen.

I bring in 240v and output 120/240.

Otherwise, the unit seems to operate as expected.

Autotransformer
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wkirby avatar image wkirby ♦♦ commented ·
What is your ground referenced to?

Where does the conductor measuring 0.5A come from and go to?

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1 Answer
Bruce Fergusson avatar image
Bruce Fergusson answered ·

WKIRBY's questions are spot-on. When conditions and connections are proper, there will be no current flow through ground conductors to the ground reference, hence no voltage drop. This is occurring b/c of a ground loop of some sort that is causing current flow through the ground conductor or there is a low-grade fault current. But I would guess a low-grade fault is unlikely inside the AT. With that being said, neutral is probably connected to ground at more than one point, causing a current flow between the multiple points with the ground lead, which is acting as a parallel conductor for neutral return current. Neutral shall be connected to the reference ground at one point only, period, no exceptions. (no ambivalence there <grin>). No current = no voltage. Good luck!

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