Power Waveform Issue

[beanland]

Fault?

Fault?

What I see is a fault. Current is going along fine, current rises due to fault or sudden load, circuit breaker trips, current drops, slight arcing during contact opening, current gone once arc is cleared.

 

[drbond24]

110310-1034 EST

drbond24:

Your voltage waveforms are useful.

V1 had the greatest drop, and V2 a substantial drop. V3 the least.

Note there is negligible phase shift of the voltage waveforms thru the incident.

I believe there was a lot of current from from V1 to neutral. If all the current was from V1 to V2, then I would expect both voltages to drop equally. So maybe more current flows from V1 to neutral than from V1 to V2. But I think I would expect a larger neutral current than what is shown.

Since the voltages are not shifted in phase very much I think the following plots would be useful:
Time base from 2 cycles before to 3 cycles after the incident (blip).
V1 and I1 on the same plot. Same for 2 and 3 as separate plots.

Another would be a single plot of V1, I1, I2, and In over the same -2 to +3 time range.

.

Ask and you shall receive!

Note that the voltages I'm giving are phase-to-phase...

 

[hurk27]

Ask and you shall receive!

Note that the voltages I'm giving are phase-to-phase...

Well it's clear the event was between L1 and L2 at the 7585 mark, and migrated to a L1 to N (or L2 to N see below) event at about the 7625-7650 mark, the first triggering of neutral current could have been the result of the imbalance between L1and L2, but after the L1 to N event the neutral current jumps up a bit, the one problem I see is to me it seems that the L1 CT or PT is swapped with L2 as the V1 is almost 180 deg's out from I1 but starts out barely lagging L2 before the event, then slightly leads L2 after the event? the other thing that points to this is both V1-V2 voltage drop, and V2-V3 voltage drop, but V3-V1 doesn't show the voltage drop, which tells me the L to N fault could have been on L2 and the CT of L1 is really L2, or the PT of L1 and L2 are swapped

 

[Smart $]

110310-1034 EST

... But I think I would expect a larger neutral current than what is shown.

...

That is why I asked about the grounding paths. Could be that a good portion of ground-fault current is bypassing the neutral CT.

Yet if the neutral current is an indication of a ground fault, it cannot be entirely a L1 to ground fault... the neutral current is out of phase with I1 regardless of polarity.

 

[G._S._Ohm]

Something triggered a transient that was damped out after a few cycles. . .?

 

[gar]

110311-1025 EST

drbond24:

Thanks for the plots. I was expecting line to neutral voltages, but without those being available we have work with what is presented.

I printed these landscape and scaled 143 %. This produced close to 1.6" for the positive slope zero crossing spacing.

Even in the severely distorted voltage waveform, V12, the voltage zero crossing did not shift. For some reason V23 shows a minor shift.

I do not have any new ideas, but I agree with Smart-$ that all of the source neutral current is not being seen by the current transformer measuring neutral current. In other words it looks like the line neutral does not contain all of the transformer neutral current, that is, there was a ground path back to the transformer neutral that did not pass thru the neutral CT.

Can your software create an approximation of the line to neutral voltages?

.

 

[drbond24]

Can your software create an approximation of the line to neutral voltages?

I don't think so. I believe I've given you about all I have at this point.

I do not have any new ideas, but I agree with Smart-$ that all of the source neutral current is not being seen by the current transformer measuring neutral current. In other words it looks like the line neutral does not contain all of the transformer neutral current, that is, there was a ground path back to the transformer neutral that did not pass thru the neutral CT.

I understand.

Thank you to everyone, especially gar, for taking the time to look at this. I appreciate the help.