hoW to select a CT?

Answer Posted / venkat iyer

Selection of CTs depends upon its usage, whether for
metering or protection. Class of accuracy, VA burden and
palatability to instrument safety factors need to be
considered incase of metering CTs. In case of protection
CTs, linearity factor w.r.t its primary current and
accuracy factors need to be considered. Metering CTs are
expressed in terms of Class 1 or Class 3 where as
protection cts are expressed as 5P10 or 5P15 or 5P20 or
10P10 etc. The first digit stands for the class of accuracy
and P stands for protection and the last two digits stands
for linearity.

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