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%.

How to find Cable size? Caterpillar generator produce (Two generators) 127*2=254 amp at 11 kv . What would be the cable size (XLPE) to supply 256 amp at 11 kv? Air or surrounding Temperature is 32 degree C. Cable will go under ground at 2.5 feet depth. Group Rating Factors is 3 cables. Clearance between cables is 7 cm. Soil Temperature (Ambient) 28o C Soil Thermal Resistivity is 1.2 K.m/W I would like to use 3 separate single core instead of using 3 core cable. Some says I should use three separate single core 120RM cables. Some says 70RM .some says 95. I m totally confused. Is there ant specific rule to determine cable size? What would be the LT cable size to flow 500 Amp current? Ifte My e mail address is ifte13@yahoo.com Anyone please send me the answer to my e mail address, i will be very glad.

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