how to calculate knee point voltage of current transformer?

Answer Posted / dinesh

Below equation is helpful in calculating the knee-point voltage of Protection CTs
Vkp = ALF(VA / In + Rct x In)
ALF = Accuracy Limit Factor
VA = Burden
Rct= Resistance of the secondary winding
In = 1A or 5A
For example if the CT Ration is 500/1A, Burden is 20VA and Class is 5P20, then Vkp is 20(20/1) = 400V.

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