CT with connected burden greater than rated one 2

[RRaghunath]

In case 'P' class CT connected burden is greater than rated burden, how will it affect the CT as well as the protection performance in service? Thanks in advance.

 

[scottf]

The accuracy, burden, and accuracy limiting burden are all essentially proportional to one another.

As a for instance, if the CT is rated 5P20 - 30 VA and you connect 60VA, then you can assume roughly 5P10 performance. 2 times the rated burden = 1/2 the accuracy limiting factor.

 

[che12345]

Dear Mr. RRaghunath (Electrical)(OP)19 May 22 11:34
"...In case 'P' class CT connected burden is greater than rated burden, how will it #1. affect the CT as well as #2. the protection performance in service?"
I have nothing new to add, but to put it in detail.
#1. As advised by learned Mr. scottf , if the connected burden is 2 times the rated; the accuracy limit factor is reduced by approx 0.5. viz " a CT is rated 5P20 - 30 VA and you connect 60VA, then you can assume roughly 5P10 performance" The CT would not be damaged but the accuracy current is within 5% when the primary current is at 10 times , instead of 20 . At 20 times, the secondary current output would be lowered to where the ALF > 5%.
#2. If the protection relay is set to perform within 5% accuracy at 20 times primary current, a 5P20 CT is capable to drive it.
FYI: The same CT but with the load burden increased by factor of 2, a 5P20 is down graded to 5P10. At 10 times primary current, the CT accuracy is within 5%. At 20 times, the accuracy > 5%, which may not be sufficient to drive the relay.
Che Kuan Yau (Singapore)