Protection Engineering Basics and Schemes Protection Engineering | Page 8

Chapter 1
Instrument Transformers:
These Transformers are used for the purpose of Metering
and Protection, We cannot have High voltage or High
current Value meters which can operate on 11KV or 33KV
directly or bear 300A or 400A current, so we used
instrument Transformers for using the exact low value
replica of operational voltage and current For Metering
and Protection Purpose.
Instrument Transformer by replica of quantities can be
divided on two types.
 Current Transformer
 Voltage or Potential Transformer
1.1 Current Transformer:
Current transformer is producing low intensity replica of
high value of current, it is same as any Transformer with
primary and secondary windings, secondary winding is
always present in Current transformer but primary
winding would be the conductor/cable on which CT is
mounted for purpose of metering and protection.
pg. 8