Current Transformer Question

[yaoyaodes]

I have a question regarding the current transformer.

For question 1.1m

I am unclear about how primary current changes affect the accuracy. Why accuracy is 2*0.3%?

 

[main197]

Looks like it comes from IEEE C57.13 permissible error. Here, the graph shows 0.6% accuracy region for currents less than 100% for 0.3Bxx CT with 4.0 rating factor. "The limit of permissible error in a current transformer accuracy class has one value at 100% rated current and allows twice that amount of error at 10% rated current". Accuracy class is stated at 100% rated current. Twice the error is allowed at 10% rated current.

For more information, go to this link.

 

[yaoyaodes]

Thanks