As it is not possible to use line current directly for measurement and protective relays due to its high value & insulation problem. Our bar primary CTs, Cast Resin CTs current transformers and control transformers are used to :

• Reduce the line current to a value (e.g 1 amp.) which is suitable for standards measuring instruments, relays etc.
• To isolate the measuring instruments, meters, relays etc. from direct line.
• To protect measuring instruments against short circuit current.
• Principal of operation:-Current transformer works on the principal of variable flux. In the ideal current transformer, the secondary current would be exactly equal to(multiplied by turns ratio) the primary current. But in practice, some of the primary amp-turns are used for magnetizing the core.This causes an error, which is termed as current (ratio)error and phase error.