Protection Engineering Basics and Schemes Protection Engineering | Page 39

See below name plate

Look, I th = 63KA Now I dyn = 2.5 I th = 2.5 ∗ 63 = 157.5KA But here nameplate mention it 163.8KA, which is ok, dynamic current will never be less than 2.5 times of I th

Now if I want to check Knee point voltage of this CT.

As you knew V k = ALF ∗ I s( R ct + R b) or

V k = ALF( I s R ct + VA

I s

) pg. 39