What do you think of these phase angle readings? 1

[westex]

Part of our relay maintenance procedure we have to prove that the current and voltage inputs to the relay are correct. When we triggered the event (screen shot provided) on the SEL-311C (substation A) we saw that the phase angles didn’t quite make sense (IB was almost in phase with VA). When talking to the boss he said something is wrong. We than compared the SEL phase angle readings to the bus diff relay and all the readings were the same. Doing that just proved that if the line relay readings (SEL-311C) are wrong so is the bus diff readings. We also went to the other end of the line (substation B) to check those readings expecting those to be 180° different than (substation A) and they were. So we can’t find anything wrong but boss still says asks how can our angles look that bad. I know power factor and vars could throw the readings off. If these reading are correct (and I believe they are) what good is “proving” the inputs to the relay in this case? Also how would you explain these readings? If anyone has AcSELerator Analytic Assistant and wants to look more at the event I can provide that.

 

[EmergencyPowered]

I fully understand VT's being wye or delta. Can CT's also be wye or delta. A wire is a wire, how is a CT a wye or delta?

 

[waross]

There is a metering scheme that uses three CTs with the secondaries in delta to a two element kiloWatt-hour meter. We used this arrangement to accurately measure power to large users. This method depends on the phase to neutral voltages being equal.
We lost one phase of a submarine cable and after a single conductor cable was laid to replace the faulty phase we could no longer depend on balanced voltages and we started using three element meters.
Yes, CT secondaries may be connected in delta.

Bill
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"Why not the best?"
Jimmy Carter

 

[davidbeach]

Back in the bad old days, the CTs on the wye side of a delta-wye transformer would be wired in delta for the differential relay. Now there is no excuse for delta CTs or delta VTs.

 

[jghrist]

An explanation other than capacitive load is consistently wrong CT or VT wiring. The capacitive load explanation is doubtful because two of the phases show the angle between I and V to be more than 90°.

 

[davidbeach]

Capacitive load on a real system at near zero real load. In real systems where lines aren't transposed, and all sorts of other text book assumptions don't hold, you can see near zero real power in one direction in less than all three phases and and the other direction in the remaining phases. If the other end gives approximately the same thing with the currents 180 out then it's probably too much to ask for the same wiring errors at both ends. Wouldn't see this on a fully balanced, text book, system. But then I've never seen all three currents have the same magnitude and be 120 degrees apart in real life.