Hit a 277 volt panel with my meter and saw 483 volts between phases for a split second

I was testing a three phase lighting panel in an old warehouse downtown last Tuesday and my Fluke showed 483 volts between A and B phases before it settled back to 277. Turns out a loose neutral on the utility transformer was causing voltage imbalance that could have fried all the ballasts if I hadn't caught it. Any of you guys run into floating neutrals that show weird numbers before everything goes haywire?

2 comments

2 Comments

piper_flores691mo ago

Neutral issues always show up as weird ghost voltages first.

fiona3301mo ago

@piper_flores69 close but it's not ghost voltage - that floating neutral let the center point drift, so A to B saw the line-to-line sum of two unbalanced phases for that split second. Real voltage, not phantom.