Our site 11kV system has high resistance grounding system and used CBCT (Core balance current transformers) to detect the earth fault current. And 132kV system has solid ground system and here residually connected VT are used to find the earth fault (DEF).
I know residual connected CTs will be used for detecting solid ground system earth faults and CBCT will be used for detecting high resistance ground system earth faults. I would like to know the advantage of using residual connected VTs for detecting earth fault.If any specific advantage, pl. explain me
Thanking you.
If the 'D' in 'DEF' is directional, the residually connected VTs are the polarizing source for the directional element with the the actual tripping being done based on current. The use of voltage tells nothing (or at least very little) about where the ground fault is located; it does an excellent job of indicating that the fault does exist, somewhere.
Zero sequence voltage says there is a ground fault somewhere, zero sequence current says that the fault current is flowing through the measuring point.
