Measurement Accuracy of energy meter A44 ABB

[yogesh]

Please help resolve this techincal queistons: The customers industrial plant is supplied with electricity from the utility company via 2 transfer sta-tions. The sum of the 2 meters A44 from the transfer station deviates by more than 3% from the val-ues of the utility meter. The customeris looking for possible causes, since the 3% deviation amounts to a quantity of approx. 300kW per hour. The cable from the transformer to the two transfer stations is taken into account mathematically with transmission losses. Cable type and lengths can be provided. The current and voltage transformers are calibrated with accuracy class 0.5. The customer wants to know, what can cause the 3% deviation. The electronic meters have a relatively small burden, the CTs could be "underloaded", to what extent does this influence the measurement result? - do harmonics in the range of 6% on average influence the measuring accuracy (the standard allows 8%)? - what other causes could falsify the measurement result?

 

[newfutile]

Do these meters measure the voltage as well?if not they may be set at 220 v and you may be running at 240 or above that , also power factor may not be ideal which may lead to inaccurate results .

 

[James]

If you are being billed for a HV connection, it is metered before the transformer.
If you are comparing this to the customers own measurements after the transformer, then you will have a difference.
I would expect somewhere between 1 and 3% losses from the transformer, depending on its loading.

remember of course that a large transformer can have a loss of several Kw even when there is no load on the output side.