Connecting Building Grounding System to 12.47kV System neutral/Ground

[hidalgoe]

Hello:

A small pump house building was recently connected to our 4.16kV overhead distribuition system. Basicall the system consists of a 150kVa pad mounted transformer (4.16kV Delta Pri - 208Y/120V Sec.

At the pole cutouts the surge arresters are tied to a ground rod at the pole base. The pump house building ground conductor is also tied to this ground rod.

The P.E.s here are of the opinion that interconnected counterpoises around the transformer pad and pump house building should be connected to the 4016kV grounding conductor.

Please help.

hidalgoe

 

[davidbeach]

Ground is ground and all grounds must be bonded together.

 

[dpc]

Yes, the grounds need to be tied together.

David Castor

http://www.cvoes.com

 

[PHovnanian]

I'm lost. Where is the 12.47 kV system?

Connect the 4.16 kV system grounds together. Generally, I also see the 120/208V system neutral bonded to the primary side (4.16 kV) grounds at the transformer. There are cases where this may not be desirable and a separate low side grounding scheme is used*. But worker safety, transformer insulation and protection operation need to be carefully considered if this is done.

*One case where this is done is on diary farms. Typically utilities tie their primary neutrals and grounds together. This allows the returning unbalanced load currents to split between the neutral and earth. When the customer's neutral (bonded to their grounding electrodes and structures) is tied to the utility primary neutral, these currents also return through these paths. In milking parlors, cows get hooked to the structure's plumbing and, as a result, become a part of this return path as well. Cows don't like that. Hospitals and other facilities with sensitive equipment (or occupants) are other instances where breaking this loop path might be desirable.

 

[hidalgoe]

Hi:

Sorry to all the 12.47kV reference was a mistake.

Hidalgoe

 

[dpc]

But if there was one, it should be bonded as well.

David Castor

http://www.cvoes.com