Dear friends,
We have a 502 MVA Auto Tr. tertiary( 13.8 kV delta) grounded through a zig-zag tr. The CTs for phase O/C protection of the grounding Tr. have their secondaries connected in delta. The relay used for above protection is Siemens 7SJ611. I would like to know as to what should be the connection of the relay current coils connected to this delta connected CTs? Delta or star? The CT ratio is 400:1 . What ratio should be configured in the relay ? 400:1 or 400/1.732 :1 ? Also it would be helpful if anybody can suggest suitable documents for analysing the current flow through the zig zag tr under different fault conditions.
Thanks in advance
We have a 502 MVA Auto Tr. tertiary( 13.8 kV delta) grounded through a zig-zag tr. The CTs for phase O/C protection of the grounding Tr. have their secondaries connected in delta. The relay used for above protection is Siemens 7SJ611. I would like to know as to what should be the connection of the relay current coils connected to this delta connected CTs? Delta or star? The CT ratio is 400:1 . What ratio should be configured in the relay ? 400:1 or 400/1.732 :1 ? Also it would be helpful if anybody can suggest suitable documents for analysing the current flow through the zig zag tr under different fault conditions.
Thanks in advance
