3-Phase 4-Wire Service Entrance

[skipg88]

I have a 3-phase pad mounted transformer rated 208Y/120 on the secondary. The Y is grounded. The transformer will be grounded locally by the use of rods and buried bare copper grounding ring. The service entrance conductors will include phase conductors sized as necessary and will include a full sized neutral(3-phase, 4-wire). The service entrance cable will be connected to a 3-phase, 4-wire 208/120 volt panel with full size neutral bus. The panel will have a ground bus that is connected to local ground via ground rod. The distance between the outdoor pad mount and the indoor panel is about 200 feet.

QUESTION: What is the position on carrying (with the service entrance conductors) a ground wire (sized per NEC Table 250.66) from the transformer ground to and connected to the panelboard ground bus. Is the grounded conductor required.

 

[charlie]

Re: 3-Phase 4-Wire Service Entrance

I am assuming you are talking about the service lateral and not the service entrance conductors from the PMT and this is an electric utility owned transformer. If this premiss is not correct, this falls under different sections and you are not dealing with either service entrance conductors or a service lateral.

We do not permit the customer's grounding system to connect to our grounding system. The reason for this rule is that any connection will place the bonding conductor in parallel with the grounded conductor. That would be a violation of 310.4.

Saying all that, I am sure other electric utilities and jurisdictions have different rules.