Knee point Voltage of Class X CTs

X CTs are special CTs used mainly in balanced protection systems (including restricted earth fault) where the system is sensitively dependent on CT accuracy. Further to the general CT specifications, we now need to know :

Vkp - Voltage knee point
Io - Maximum magnetising current at Vkp
Rs - Maximum resistance of the secondary winding.

in other words it is a custome made CT..so u have to specify the necessary info compared to general CT

Thanks lot,,,

but why we r not consider(knee point voltage) in other class CT,s?

knee point voltage is required for relay opretion. In differential protection,some relay have minimum req. (Ereq) voltage which must be greater than the CT' knee point voltage.If it is less than knee point then the relay will not operate after a particular S/C level.

i want to know,from where you passed out and where is your home?