PQ Scope Picture & Question

[iwire]

The change in power consumption at the supermarket could easily have resulted from the transformer change.

Yes, it could have, I don't think anyone has indicated otherwise.

Or it could be any of a hundred reasons, we have no idea when the trans was changed, why it was changed or if it resulted in any voltage change.

I started this thread to ask those in the know what I was seeing on the scope because I did now know what I was looking at.

 

[mivey]

This got me thinking that perhaps the distortion on the B phase may have been noise contributed by the failed revenue CT or was it a coincidence?

While reading these posts it got me thinking. Anyone think this is possible?

Could be an issue with the metering. Line disturbances damage them from time to time. It would not hurt to ask the last time the metering was tested. This usually happens once a year for the large loads, once every few years for smaller loads. If the site has been recently tested but you still want them to test it, some utilities will charge you a testing fee if they find no trouble. The metering should test within 2% accuracy and almost all are way better than that.

 

[mivey]

Imposable for me to say, both pictures may indicate a clean signal from the CTs but from a dirty source.

If it were my meter, I would like to see a clean signal from a large current load. Just for peace of mind and to eliminate one avenue of possibilities.

 

[iwire]

If it were my meter, I would like to see a clean signal from a large current load. Just for peace of mind and to eliminate one avenue of possibilities.

I have peace of mind right now, my only concern is finding out why the customers usage has increased.

 

[mivey]

I have peace of mind right now, my only concern is finding out why the customers usage has increased.

If you find out: inquiring minds want to know. :grin:

 

[gar]

100313-1534 EST

iwire:

If the KWH and billing charges are compared on a month by month basis for several years, maybe two back from now, there may be a step change of the roughly 4% that will show up. If the variations from month to month are totally random, then some other cause than transformers or other equipment is likely. Weather for example.

Even if weather randomness is superimposed on some other change it is possible one can see a specific change around some point.

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