choose current transformer

[hasanhadi]

hi
1-how choose transformer suitable for metering or protection?
2- what happend if VA off load greather than VA for transformer current? for example metering CT 10VA 500/5 and load 1.2 ohm
now max.load=10/25=0.4 ohm but load=1.2 what happend for ct
3- how caculated knee voltage Vk

 

[JG2828]

Lots of good papers can be found here:

http://lmgtfy.com/?q=selecting+a+current+transformer

 

[DTR2011]

I read the ABB paper from the Google search and it is very understandable.