Ground Grid Design
Ground Grid Design
(OP)
We are building a small substation ( including a transformer and a padmount switchgear) in adjacent to a wind farm substation and connecting the new substation ground grid to the existing grid. The existing grid has a measured grid resistance of .5 ohms. we are using Cymgrd to model our grounding grid and assumed a parallel resistance of .5 in the model which has dropped the GPR to below 5K.
However, step and touch potentials are still high. Do we need to model the existing ground grid as well as the new grid to accurately calculate step and touch potentials or are we missing a step?
Thanks for all responses.
However, step and touch potentials are still high. Do we need to model the existing ground grid as well as the new grid to accurately calculate step and touch potentials or are we missing a step?
Thanks for all responses.






RE: Ground Grid Design
Regards
Marmite
RE: Ground Grid Design
1) select different surface material, i.e. high resistivity material like clear crushed stone, asphalt, etc
2) use unequal spacing method to lay finer grid around fence and other metal structures
RE: Ground Grid Design
"DESIGN OF SWITCHYARD GROUNDING SYSTEMS USING MULTIPLE GRIDS-by Stephen W. Kercel" method.
RE: Ground Grid Design
Thanks
RE: Ground Grid Design
RE: Ground Grid Design
Does the existing substation have a HV/MV transformer, with a grounded MV winding that feeds the new transformer? If so, the source of MV ground fault current will be the existing substation transformer and it will not flow through the earth and contribute to GPR or touch voltages. A HV ground fault will produce GPR and touch voltages on both the existing substation and the new small substation.
RE: Ground Grid Design
RE: Ground Grid Design
RE: Ground Grid Design
RE: Ground Grid Design
With cymeground If I remember you can simulate the both cases connect or not and see the impact of your design.