Practical guide for ground grid design

[JLuc]

I'm working on the expansion of an outdoor substation, and I'm looking for a practical guide to design the new earth grid. I have limited information on the existing one. Earth resistivity tests are beeing done now.

Any suggestion on such a practical guide??

It's a 25 kV sub, with 2 txfos (25kV/4kV & 25kV/600V both resistance grounded), capacitor bank, breakers etc.., the actual fence will be moved about 20 feet out on each side.

Thank you

JL

 

[7anoter4]

Hi JLuc
I think you have no problem to calculate the GROUNDING GRID FAULT CURRENT.
In order to build a Grounding Grid and calculate GPR and Touch and Step Potential this link may be useful:

http://www.erico.com/public/library/fep/LT0359.pdf

regards

 

[cuky2000]

A classical guides are the IEEE Std 80 for the US and other ANSI market place and CENELEC / IEC Std 479-1 for European countries and other IEC market places.

 

[JLuc]

thanks for the suggestions.

the IEEE Std 80 helped a lot. Good "step by step" design procedure.

JL

 

[jghrist]

The problem will be with the unknown existing grid. For safety in the expansion area, you could assume a minimal grid in the existing substation. If the expansion increases fault levels at the existing substation, however, you need to check to ensure that the existing substation is safe. I see two choices. First, locate the existing grid and ground rods. Second, install new grid wires and/or ground rods in the existing substation area. Neither option is easy, particularly in an energized substation.

The CDEGS 2003 Users' Group Conference included a paper on the Assessment of Earthing Systems at Existing Substations by Mark Davies and Matthew Taylor, Strategy & Solutions Ltd, UK. You might get information on this at the SES website

http://www.sestech.com/.

If not, you could contact SES to get a copy.