What is the difference between CT for protection and Ct for
metering?

Answer Posted / avdhesh

Metering CT : It will function up to full load current only
then it will be saturated. It will not follow the CTR Above
the full load curent. Take the example of a train, if
boggies are connected to engine it will follow the speed of
engine but if coupling is broken boggies will not follow
the engine.

Protection CT : These CTs have to protect against fault
hence these CTs are not supposed to saturate during fault
current and they should transform secondary current exectly
replica of fault current. For example class 5P20 means 5 =
% error, P = protection class, 20 means = 20 times of rated
current means when 20 times of rated current is flowing
through CT the error in sec. current may be +/- 5%.

Never connect metering CT for protection purpose as it will
saturate during fault and will not provide any protection
at all.

Is This Answer Correct ?    184 Yes 16 No



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