Metering CT vs. Protection CT
Metering CT vs. Protection CT
(OP)
Hi everyone
On a newly buildt substation, on the 380V side, faultlevel of almost 32kA, I've noticed something. The CT's been use there is 3200/1, but it is metering CT's. When I asked one of the guys if it is correct, (in my opinion it must be 10P10 protection CT's, otherwise the CT's would saturate under a big fault) he told me that the relay been used is an electronic relay with a very low burden. So in fact is there nothing wrong with metering CT's! Is this statement true?
regards
On a newly buildt substation, on the 380V side, faultlevel of almost 32kA, I've noticed something. The CT's been use there is 3200/1, but it is metering CT's. When I asked one of the guys if it is correct, (in my opinion it must be 10P10 protection CT's, otherwise the CT's would saturate under a big fault) he told me that the relay been used is an electronic relay with a very low burden. So in fact is there nothing wrong with metering CT's! Is this statement true?
regards





RE: Metering CT vs. Protection CT
I don't what know the contract language specifies, but I'd ask for calculations and CT manufacturer’s literature supporting that. Then see that the label information on the CT matches/supports the paper.
RE: Metering CT vs. Protection CT
RE: Metering CT vs. Protection CT
RE: Metering CT vs. Protection CT
Just to illustrate an example,
we are using GE Multilin relay SR489, which has multifunctions like,
Overcurent/earthfault
differential protection and all other generator protection in one relay.
metering
data logginh and communication with SCADA.
disturbance recorder etc.
Now we require to give single C.T input. which one of the following to choose?
- Class x (suitable for differential protection)
- protection C.T 5P10
- metering C.T (cl 0.5)
we have choosen C.T of class 5P10 in the line as well as neutral end C.T.
If any further technical details on the above is required, please let me know.
RE: Metering CT vs. Protection CT
I agree with busbar, you should check the claculations otherise you've got yourself a very expensive ammeter !
RE: Metering CT vs. Protection CT
RE: Metering CT vs. Protection CT
Bung
Life is non-linear...
RE: Metering CT vs. Protection CT