Three phase power meter reading no power with current and voltage

[danwebb88]

I am struggling recreating an issue that was reported on a site where there are several breaker synchronization devices (has three phase PT and CT inputs) that is reading voltage at the breaker and current across the breaker but is reading 0 kW for real power and 183 kVar for reactive power. Each phase voltage is 450 V and each phase current is 590 A. I am not able to determine the phase angles with this device.

The CTs are 1500:5 A and the PTs are 400:100 V. The PT wiring is a 3PH3W for a delta system.

With the real power reading 0 kW with each phase having current, it appears as though the wiring from the CTs could have been swapped between any two phases. In a balanced system, which this is, this would be the case. However, the same would also be true for reactive power. If the issue was in fact swapped CT phases, then we would read 0 kW and 0 kVAR. This is where I am struggling to theorize the reason for this reading. Assuming there is something wrong with the wiring, what possible error could cause the meter to read a fully reactive load with no real load?

 

[GoldDigger]

Fairly simple to analyze, I think, but not to get the results you see. :?

If you swap the leads on one current transformer on a balanced three phase feeder, the calculation of real power for that line, not phase, would give a negative power equal in magnitude to the actual forward power. That reversal of a single CT would have no effect on the calculated power for the other PT-CT pairs.
If, on the other hand, you rotate the association of CT output with corresponding PT output all three of your phases will calculate power as if the phase angle between current and voltage was 120 degrees. Or with a polarity reversal too, -60 degrees.

At first glance if the load is balanced neither of these will produce the zero real power, large reactive power result that you report.
There is probably some combination of unbalanced and reactive loads that, combined with one or the other of the original scenarios, could produce your result.

In particular, if only one (line-to-line) phase is loaded, one CT lead reversal would sum to zero real power. But no reactive power. :happysad:
And your description states equal current on all lines.

I would be tempted to say that the power meter is defective.