I work for an Electric utility.
Have noticed that the actual amperage running through a phase does not match the amperage being sent to the meter with it's proper multiplier from the current transformer (CT)?

Example: phase A is using 83 amps. The X1 tap to the meter from the current transformer (400:5 ratio = multiplier of 80) shows 0.8 on my amp check.

If you take the 0.8 and multiply X 83amps you have a metered current of only 64 amps for that phase. Additionally I get a 1.0 amp reading when I check the amps nearer to the CT on the X1 line (real close to 83) and the 0.8 mentioned above happens at the switch gear just under the meter? A "amp loss" if you will.

The result is lost revenue to the utility company. I don't believe the problem lies in the windings of the CT's. I've noticed this on all of my checks. If this were the case and the problem is as prevelent as I think it might be lawsuits to the manufactures might ensue.
Well...

Does anyone out there know why this ? What could be the cause? And the remedy?

Thx. Chafor

PS - I know no one gives a rats tail if any utility gets "cheated" a bit by perhaps their own ineptitude but I would like to get to the answer on this. Could be a "feather in my cap"!

Can you restate this?

The X1 tap to the meter from the current transformer (400:5 ratio = multiplier of 80) shows 0.8 on my amp check.

If you take the 0.8 and multiply X 83amps you have a metered current of only 64 amps for that phase. Additionally I get a 1.0 amp reading when I check the amps nearer to the CT on the X1 line (real close to 83) and the 0.8 mentioned above happens at the switch gear just under the meter??



What is the ammeter you are using?

How long is the lead from the CT to the utility meter?

What is the burden on the CT?

What is the make and model of the CT and the utility meter?

Are you saying that measuring the amps of the X1 lead close to the CT is 83, and what is the amps close to meter?

Thx for response.

ammeter made by Fluke Corp in Thailand. Fluke Electronics

length of X1 wire is aprox 3 1/2 feet from CT to the meter.

The electric meter I believe is either made by Slumberge' (sorry if misspelled) or Itron Corp

Explain "burden" on the CT to Me! 400:5 multiplier 80?? It was a "Donut" type - NOT bus bar.

And yes I got consistent .8 in the switch gear box (indicating 64 amps going through meter) while picking up an amp read of 1.0 (one) close/near to the CT indicating 80 amps vs. 83.

I wouldn't have a problem with the 3 amp difference if it was consistent from the CT to the meter. I would have assumed, I believe correctly, that the meter was probably getting the correct measured load and that the problem was with the (calibration of the) ammeter. But the 0.8 was "way off" in my opinion... or is it one should expect theses discrepancies?

Thx.