Exchange of current transformers of defferent class

[npower0073]

I want to ask if I can exchange a current transformer of the same burden and ratio but with different class, meaning to use a 0,2s class to replace a 5P20 class. Is that feasible? I understand that 5P20 or 5P30 are used for protection purposes and have higher strength against short circuits in contradiction with 0.2s that are used fro measurement, metering, excitation and synchronization control, due to better accuracy. Can you advise on that one?

 

[lz5pl]

It depends for which purposes you are going to use new CT's. If protection circuit will be connected measuring class core should not be used. These cores typically saturate at about 5 times nominal current, so relay protection connected to measuring core probably will not operate correctly.

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It may be like this in theory and practice, but in real life it is completely different.
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[nirajagrawal]

Always use recommended class CT(Current Transformer) for recommended purpose only. If you use metering class Ct i.e. 0.2 , 0.5 etc Class CT for protection. Then protection system will loss its sensitivity , because metering core gets saturated early on fault & never gives replica of fault current upto 20 or 30 times of rated current , due to this current base relay (Backup Realy) will not operate within required time , relay will take more time to clear fault.
Similarly if you use protecton class 5P20 or 5P30 Class CT for metering , meter may burnt for fault , which is not get cleared within time. This may happen only with present static energy meters having lower factor of safety.
Recording of meter also affected because meter is having higher accuracy class & CT is having lower accuracy class for metering & this will add error to meter energy recording.