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