What is the Different between CT Class-0.2 & Class-0.2s ?

Answer Posted / sam

Accuracy class of 0.2 means +/- 0.2 % error. But, the
declared accuracy is guaranteed only between 100% & 120%
rating. And, with some increased error, the CT performance
can be guaranteed from 5% loading. Below this load, the
error is not guaranteed. It can be anything.

Normally these classes of accuracy are used for Tariff
Metering by the Utility Company.

In large industrial projects, the project would be
commissioned in steps only. In such a case, initially the
loading will be very low. If the tariff metering CT errors
are haphazard, it may not be acceptable either to the
supplier (in case of negative error) or to the consumer (in
the case of positive error). And the magnitude can be quite
large, say, with a sanctioned demand of 10MVA, even 1%
error means 100kVA.

To cater to such situations, Standards have introduced two
new accuracy classes, 0.2S & 0.5S for tariff metering
purposes. These special CTs guarantee the declared
accuracy, even with 20% loading. And some definite error
can be defined even with a load as low as 1%. Thus they are
suitable for industries where loads are commissioned in
steps or stages.

Is This Answer Correct ?    44 Yes 5 No



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