Maximum ground fault current for grounding grid design
Maximum ground fault current for grounding grid design
(OP)
Background:
There are two 230kV stations within a same yard with a fence in between. Station 1 is a three 230kV breaker ring bus. Station 2 is a three winding transformer 230/115/34.5kV Yg/Yg/Delta with one 115kV line and one 34.5kV feeder. At delta tertiary, there is a grounding transformer to make the tertiary system effectively grounded.
Question is:
Both station 1 and station 2 grounding grids are tie together, so shall we consider 115kV and 34.5kV side ground fault levels while finding the maximum ground fault current for performing station 1 grounding grid calculation and design? If yes or no, any reference document to support?
Thank you,
Best Regards,
Bing
There are two 230kV stations within a same yard with a fence in between. Station 1 is a three 230kV breaker ring bus. Station 2 is a three winding transformer 230/115/34.5kV Yg/Yg/Delta with one 115kV line and one 34.5kV feeder. At delta tertiary, there is a grounding transformer to make the tertiary system effectively grounded.
Question is:
Both station 1 and station 2 grounding grids are tie together, so shall we consider 115kV and 34.5kV side ground fault levels while finding the maximum ground fault current for performing station 1 grounding grid calculation and design? If yes or no, any reference document to support?
Thank you,
Best Regards,
Bing






RE: Maximum ground fault current for grounding grid design
Because the grids are tied together and adjacent, they would be analyzed as one single grid, using the maximum grid current.
See IEEE Std 80-2000, Section 15.8.
RE: Maximum ground fault current for grounding grid design
The maximum injected current to the ground is a fraction of largest phase-to-ground fault. A current division factor is recommended to be considered.