Substation Ground Grid Location

[scottf]

I am interested to know the location of substation ground grids in relation to control wiring. I.e. is control wiring (such as wiring from apparatus to the control house) generally run above or below the station ground grid.

Thanks for any input you may have.

 

[jbartos]

Suggestion: Could you be more specific about those control runs and ground grid. Normally, the ground grid or ground mesh is installed in the ground, e.g. 24 inches deep, under the substations, usually medium voltage and above, Reference IEEE Std 80-2000 Guide for Safety in AC Substation Grounding. Usually, there is no control wiring around in the ground. If need to be, it is run above the ground or very close to the ground surface. This could potentially answer the question, i.e. the control wiring run would be above the grounding grid.

 

[jlgordon]

ground cable to be 1' - 6" minimum below existing grade.
ground mat continuous under control cable trench.
gnd mat cable shall be placed the full length, on top, of the lateral duct bank and treminate at the end of the bank.

In other words, underground control cable are sandwiched between ground mat.

 

[cuky2000]

Control cables in most substations are designed to run in cable trench with 24 inches deep approximately.

Most ground grid designs are installed under the trench to maintain the continuity of the ground grid.

For Illustration, see one typical pre-cast trench information:

http://www.trenwa.com/graphics/catalog.pdf

Beware that in some instance could be noise induced from the ground grid particularly under fault or switching conditions. Therefore, shielding or other grounding mitigation techniques should be applied.