What are the specific requirements or guidelines for testing industrial grounding grid? What is the reference?

Question by ahe03: What are the specific requirements or guidelines for testing industrial grounding grid? What is the reference?
Where in NFPA or NEC do I find the need to do this ground testing? I hear it needs to be done usually yearly.

Best answer:

Answer by Fred P
There a re a number of references for ground grids….

IEEE 80 – Guide for Safety in AC Substation Grounding
IEEE 81 – Guide for Measuring Earth Resistivity/Ground Impedance….
IEEE 142 – Recommended Practice for Grounding of Industrial and Commervial Power Systems
IEEE 81-2 – Guide for Measurement of Impedance for Large Interconnected Grounding Systems

NFPA 70 (NEC) or the National Electric Safety Code do not identify any requirements for periodic testing of industrial grounding systems – nor do the above-referenced IEEE standards. This is more a matter for the owner to address, based on his experience (or the recommendations of the engineer based on the particular situation).

IF it’s located in a particularly corrosive environment in an urban area, an annual test is probably a good idea. If it’s located very remotely in a rural area (and clean air/water – up in the mountains), you could get away with checking it a few times during its life. If the fault duty has increased significantly since installation, it would probably be a good idea to reanalyze the grid to ensure you don’t have unsafe touch or step potentials.

Calif PE

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