Can anyone explain this voltage reading I had today?
I was repairing some perimeter lights at my work today, and found out that the circuit was all messed up. It’s a 480v circuit from Line to Line, 277v from Line to ground. When I metered most of these lights, I got the right voltage from line to ground which is 277v, but from Line to Line it showed only 120-130v??? What can cause that to happen? On some fixtures, I got 480v from Line to ground!! And on some, I get about 350 from Line to Line. Very weird stuff. I can’t figure out what it is. Does anyone out there have a clue? Thanks. ( The lights have 250w High pressure sodium ballasts. Before this problem there was a major voltage fluctuation problem which I found to be a bad igniter in one fixture that was screwing up the whole circuit. I disabled that fixture and now there’s no more fluctuation, but I have a big voltage problem. )
First thing that comes to my mind is grounded phase conductor. Your supply system must have some resistance between neutral & ground. Due to an undetected ground fault somewhere in your system (trip setting of your ground fault protection device is too high), your neutral is working on a potential higher than that of ground. This can also happen due to severe unbalance phase loading which can give rise to appreciable neutral currents. I suggest you to measure neutral voltage at your Distribution board/Lighting transformer.
Hope this will be helpful.
Wyeksploatowany LRF 250W Polamp z 1991 r
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