Protection Engineering Basics and Schemes Protection Engineering | Page 222

But primary is delta, so

I prsecond = I PS =

I PS = 0.787319A

2361. 957

3000 1

I PS = √3 ∗ 0.787319 I PS = 1.363637A

Now we have to use interposing CTs as vector group is different on both sides for error correction, I use it on primary side, my primary

CT interposing =

1.363637 0.787319 1

CT Interposing = 0.787319: 1

Modern numerical relays have built in function of interposing CTs

At 500 / 1, secondary side of 393.6595A will be

I secsecond = I SS =

I SS = 0.787319A

393. 6595

500 1 pg. 222