Poletop Overhead Service Equipment Bonding Requirements

[erikcederstav]

I work on a lot of community solar projects that interconnect to overhead lines in the 15-35kV classes. The service usually comes with a grounded conductor as well. Typically the OH setup is as follows:

Existing Utility Pole -> Utility Meter Pole -> Customer Service Disconnect Pole -> Customer Meter Pole -> Customer Recloser Pole -> Riser Pole

My partners and I were debating whether the Neutral-Ground bond in a customer owned transformer downstream of these poles is a Main Bonding Jumper or System Bonding Jumper. There is no question to me that this would be a System Bonding Jumper, and I was able to convince them that much.

I went to Section 250 Part X to review bonding requirements for MV services, and I still have some questions on how it applies to OH equipment.

1. 250.186(A) says the grounded conductor must be bonded to the disconnect enclosure, but if it is an overhead GOAB switch, does that even count as the enclosure? Does this section apply?

2. I don't usually see an EGC being run with overhead conductors, but is it possible that this is technically required per 250.180

3. Does the NEC have any blind spots for OH mounted equipment?

Thanks!

 

[electrofelon]

The NEC doesn't do a very good job with MV. Many OH MV systems will be an MGN so the neutral is your EGC. If it's not an MGN, I believe you need an EGC.

 

[erikcederstav]

The NEC doesn't do a very good job with MV.

I figured as much. On the customer side for these solar sites, the MV neutral is typically only grounded at one location, the transformer. Even though the NEC doesn't explicitly say this, I would still say we follow the spirit of a MGN system as the customer poles are practically a short extension of the utility MGN distribution network.

Also, looking more closely at 250.186, reading...

"A main bonding jumper shall connect the grounded conductor(s) to each service disconnecting means enclosure."

it isn't saying that there necessarily is a disconnecting means "enclosure" (I don't think any NEC definition of an enclosure is present for an OH GOAB), but if there was one, you would bond it.