i have some doubts about the current transformer selection.
if some one knows how to select the current transformer for 11 kv protection purpose, i just need how to select it,which parameters should be kept in mind.

 

Current transformers do not protect against voltage. They are a single winding which is excited by current. The result is a current output which must be dissipated in a resistor. The voltage across the resistor is proportional to the current in the wire that passes through the center of the current transformer. The voltage on the wire that is having its current measured is irrelevant. The current transformer does not measure the voltage or protect against it.

 

The wire carrying the high voltage current needs to have high voltage insulation where it passes through the current transformer, of course. So the current transformer main parameter of interest is the maximum current you want to detect.

 

This might mean the current transformer needs a big hole in the center to allow that much insulation. Think about what kind of insulation you have available that will stop 11,000 volts.