250.32 - Grounding for Bridge w/ Main Span Truss

[NECuser]

For a long bridge with a Main Span Truss and Steel Members
Two separate electrical load centers on opposite sides of the bridge to feed roadway lighting, aviation lighting, navigation lighting, cameras, etc.

Is it required by NEC to provide a grounding bond jumper conductor from the electrical service electrode's grounding system to the bridge structure steel members, allowing the bridge structure steel members to establish an effective ground fault current path?

My understanding is that installation of the jumper will bring the bridge spans to the same potential voltage path, meaning that no voltage differential should be registered between the electrical system grid grounding system and the bridge steel structure.

 

[petersonra]

For a long bridge with a Main Span Truss and Steel Members
Two separate electrical load centers on opposite sides of the bridge to feed roadway lighting, aviation lighting, navigation lighting, cameras, etc.

Is it required by NEC to provide a grounding bond jumper conductor from the electrical service electrode's grounding system to the bridge structure steel members, allowing the bridge structure steel members to establish an effective ground fault current path?

My understanding is that installation of the jumper will bring the bridge spans to the same potential voltage path, meaning that no voltage differential should be registered between the electrical system grid grounding system and the bridge steel structure.

IIRC, the NEC specifically prohibits the use of the GEC as a fault current path. The EGC is the fault current path.

 

[Smart $]

IIRC, the NEC specifically prohibits the use of the GEC as a fault current path.

That doesn't sound right. I'm thinking more that it can't be the only path.

The EGC is the fault current path.

The EGC is the required path, but other paths are not prohibited... and in most cases, unavoidable.

 

[Smart $]

...

Is it required by NEC to provide a grounding bond jumper conductor from the electrical service electrode's grounding system to the bridge structure steel members, allowing the bridge structure steel members to establish an effective ground fault current path?

...

I'm more inclined to think the bridge would be designed so it is an electrical grounding electrode...

 

[petersonra]

That doesn't sound right. I'm thinking more that it can't be the only path.


The EGC is the required path, but other paths are not prohibited... and in most cases, unavoidable.

that is probably a better way of phrasing it, and more correct.

 

[petersonra]

I'm more inclined to think the bridge would be designed so it is an electrical grounding electrode...

It is only a GE if it meets the NEC requirements for being a GE. As a practical matter, I think it would be about as good of a GE as one could get, even if it was not specifically designed as one.