SchoolofPower
Electrical
Hello,
Long time reader, first time poster. We were testing some bushing CT's today. 20 of them tested fine, 1 had some weird results. I have attached the results of a good test and the test in question. The CT would not saturate, we drove 5 Amps into the secondary and could not get a knee point. Has anybody ever seen this before? Comments? Failed CT? Ratio was decent no great but close. Smallest tap was 50:5 and error was 20%.
Also I know that IEEE C57.13.3 recommends grounding the secondary circuits of CT/PT’s at the first “point of application”. I have generally used the first TB the instrument transformer touches. Is this not acceptable? Should I be using the first TB inside the control room? If so do you run the risk of losing your ground if you have multiple shorting blocks or FT switches ahead of this point.
Thanks in advance.
Nathan
Long time reader, first time poster. We were testing some bushing CT's today. 20 of them tested fine, 1 had some weird results. I have attached the results of a good test and the test in question. The CT would not saturate, we drove 5 Amps into the secondary and could not get a knee point. Has anybody ever seen this before? Comments? Failed CT? Ratio was decent no great but close. Smallest tap was 50:5 and error was 20%.
Also I know that IEEE C57.13.3 recommends grounding the secondary circuits of CT/PT’s at the first “point of application”. I have generally used the first TB the instrument transformer touches. Is this not acceptable? Should I be using the first TB inside the control room? If so do you run the risk of losing your ground if you have multiple shorting blocks or FT switches ahead of this point.
Thanks in advance.
Nathan