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Pad mounted transformer

Pad mounted transformer

Pad mounted transformer

(OP)
Hi Everybody,
Could anybody advise me any practical article or source of information available on web which contains some pictures or any one of you drop few words about grounding of a 167 KAV pad mounted distribution transformer. I am not sure how to start. It is an instruction to contractor. I think first he should be advised to measure the resistivity of soil and the resistance should be less than 5 ohm.He should bury 10 ft, 5/8 in copper claded steel rod and then calculate resistance. if it is still less than what to do. Add one more but how far from each other. Please advise.
Thanks

RE: Pad mounted transformer

I think you only need to install a 10' gnd rod in the secondary compartment and connect to the Xo (neutral) terminal. You then run the service conductors to the building. At that point the NEC 250 requires that you install a gnd rod with a resistance of 25 ohms or less. If the reading is less then you are required to install another rod spaced at least 6 ft away.

RE: Pad mounted transformer

Quote "If the reading is less then you are required to install another rod spaced at least 6 ft away. "
That should read if the reading is more that 25 ohms you need another ground rod.

RE: Pad mounted transformer

Are you just trying to comply with NEC?  If so, it is as wareagle says.  

RE: Pad mounted transformer

Most utilities require a ground loop 2-3' outside of the transformer pad, connected to at least 2 ground rods.  This is to create the equipotential plane to minimize step and touch potentials.

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