Transformer Differential Protection (87)
Transformer Differential Protection (87)
(OP)
Should the transformer differential protection (87) be responsible on detecting single phase to ground faults inside the transformer? If there is a SLG on transformer secondary, should 87 detect it?
RE: Transformer Differential Protection (87)
Only thing is that the zero sequence filtering that is adopted in the protection settings desensitises the protection to some extent (makes it less sensitive in other words) against SLG faults.
RE: Transformer Differential Protection (87)
Assuming that the "secondary" is a solidly grounded wye, most SLG faults will be detected by a phase 87 element. More can be detected by a negative sequence 87 element (called 87Q sometimes). But the closer you get to the neutral the harder it is for a phase 87 to detect. If the transformer is high impedance grounded, or capacitively grounded (aka ungrounded) then a SLG may not be picked up by the 87.
I’ll see your silver lining and raise you two black clouds. - Protection Operations
RE: Transformer Differential Protection (87)
RE: Transformer Differential Protection (87)
I’ll see your silver lining and raise you two black clouds. - Protection Operations
RE: Transformer Differential Protection (87)
That's interesting. It would be a good subject for a technical paper. I haven't seen any on the subject.
RE: Transformer Differential Protection (87)
Maybe a dumb question, but isn’t that what the stabilizing resistor is supposed to stop misoperations due to CT saturation??
RE: Transformer Differential Protection (87)
I’ll see your silver lining and raise you two black clouds. - Protection Operations