HELLO, WE have CT's with not equal

sori · Jun 30, 2024

HELLO,
WE have CT's with not equal excitation curves in each of the phases for a differential protection of a generator in a relay G60. My questions are:
1. It is possible to adjust the mismatch compensation in G60 for each phase?
2. It is possible to adjust the mismatch compensation for 3 phase CT's in the line side or in the neutral side separately in G60?
3. Is there any some of the Standard reference about: What is the permitted deviation for excitation curves between the CT's in each phase for a generator differential protection?
Thanks a lot in advance for reference to questions

wcaseyharman · Jun 30, 2024

Just out of curiosity, have you done the calculations to see where the maximum fault puts you on the saturations curve with the burden on the CT? Sure it’s not ideal but If neither CT saturates for the maximum fault current case at your facility I’m not sure you have a problem - we have a plant with new CTs on the neutral and 60 year old CTs on the switchgear, it’s been working fine.

Casey

dpc · Jun 30, 2024

Not aware of any adjustments per phase in the G60 for CT accuracy. As suggested, the difference may not matter based on the available fault current. I would consult with GE/Multilin regarding application of the G60.

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HELLO, WE have CT's with not equal

sori

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dpc

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