Answer / 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.

Answer / k.prakashchandra

's' stands for special.0.2s class cts guarantee the the
specified accuracy even at 1% and 120% of rating where 0.2
class cts may not be accurate upto 5% and beyond 100% 0f
rating

Answer / rao

For 0.2 Class specified accuracy is 'defined' between 5% to 120% of rated current, whereas for 0.2 S the accuracy is provided between 1% to 120% of rated current. At these secondary current ranges, accuracy is applicable when the burden is between 25% to 100%.

Hi My dear all Friends, There is a question regarding HVAC Engineering and widely used in Power Projects. Question- What is the diffrence Between REF, SEF and Differential Protection....???? Where REF - Restricted Earth Fault SEF - Senstive Earth Fault.

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