Current 180 degrees out of phase with Voltage

[Doghandler]

Gents,

Little help please. Currently investgiating some intermittant faults on a server room distribution board. At the moment the UPS systems kick in and out randomly as a result of suspected voltage fluctuations.

To check our supply we monitored the supply to the board with a power quality meter and found from looking at the phasor diagram the whilst blue and yellow pahse had current slightly leading voltage blue phase was 180 degrees out of pahse with the voltage.

We suspect it may be due to a neutral fault but would like some back up.

Has anyone come accross this or from theory suppose what is the problem other then a neutral fault?

 

[VEBill]

Was the current sensor installed on that wire backwards?

 

[Doghandler]

Already checked that. Rookie mistake. Nope.

 

[VEBill]

The only thing I can add is that one of my rules of thumb is the following:

When everything looks crazy, start checking the continuity of the return lines.

 

[waross]

As I understand your information, look for an inverter with the leads swapped. As I understand the information, it sounds like a transformer in a 3 phase bank with X1 and X2 swapped.
respectfully

 

[dwftx34]

What is the operating voltage 120/240 or 120/208 is this a single phase or three phase system or a European voltage system.

 

[Doghandler]

Guys found the problem. Apparently the electrician DID have the sensor backwards. Most embarrasing but it does happen....

Apologies to all.

 

[VEBill]

Ever so modestly...

 

[gepman]

Your hint should have been when you noticed that the other two legs had leading (not lagging) power factor and the third as you said was 180 degrees out of phase. You know that you are measuring it wrong.

Don't feel bad, I get about 10% of my measurements hooked up backwards the first time even though I try to be careful.