Utility Co. Wiring Metal Light Poles In Ma.

[tom baker]

Re: Utility Co. Wiring Metal Light Poles In Ma.

"To compare their grounding system to ours is inaccurate." Mostly yes but not for lighting.


What is the ground rod for?
Good question.
I am a member of the Illumination Engineering Societies Roadway Lighting committee (we write the standards for street lighting), and write articles for a traffic signal magazine.
I belive that the reason there are ground rods at metal lighting poles are:
1. The civil engineer drives the bus on traffic signal installations.
2. Lighting started with the utilities, they use ground rods (NESC), hence we should use ground rods (NEC).

Also utilities are installing street lighting to the NESC rules, for systems under 600V, following the NESC rules can result in a ground rod and no equipment grounding conductor.
But they should follow the rules of the NEC. Go here for an article on the NEC vs the NESC:

http://www.imsasafety.org/journal/mayjun/mayjun8.htm

[ November 04, 2005, 05:16 PM: Message edited by: tom baker ]

 

[iwire]

Re: Utility Co. Wiring Metal Light Poles In Ma.

Originally posted by romeo:
I did some research of the MGL and found MGL 166-32 that reads in part "Such inspector shall supervise every wire over or under streets or buildings in such a city,town or district and every wire within or supplied from buildings and structures subject to the provisions of chapter one hundred and forty-three and the state building code"I interpret that to mean that I as the AHJ has jurisdiction over that installation at least in the state of Massachusetts.

I have a couple of comments.

1)You are not the AHJ, as far as I understand MA rules, the AHJ is the State and you are an "Inspector of wires".

2)"subject to the provisions of chapter one hundred and forty-three and the state building code"

I think you will find that you are limited to the scope spelled out in 90.2 which leaves the utility work out.

Think about what you are suggesting, you would then have to have the utility also follow all the other NEC rules, wire sizing etc.

I am sure this separation between the NEC and the utility has long been agreed upon.

That said you may remind the power company about all the bad press they have been getting about energized covers in and around Boston and the fact that bonding the pole to their neutral would do a better job than a ground rod alone.

 

[romeo]

Re: Utility Co. Wiring Metal Light Poles In Ma.

IWIRE would bonding the neutral cause an improper neutral to case bond resulting in objectionable neutral current on the pole? Also please explain what path the current would take should the neutral of the circuit become open.

Romeo

 

[iwire]

Re: Utility Co. Wiring Metal Light Poles In Ma.

Originally posted by romeo:
IWIRE would bonding the neutral cause an improper neutral to case bond resulting in objectionable neutral current on the pole?

If the pole is covered by the NESC it would not be improper.

Yes it could raise the potential of the pole in relation to the earth due to voltage drop on the grounded conductor.

Originally posted by romeo:
Also please explain what path the current would take should the neutral of the circuit become open.

If the grounded conductor opens the pole will be 'hot'.

That said given the choice between bonding the pole to the grounded conductor or bonding it only to a grounding electrode IMO the grounded conductor is a safer method.

Like it or not the NESC does not require a separate EGC.

Also all of this could apply to the meter socket on the side of every house in America.

The meter socket is grounded via the utility's MGN (multi ground neutral).

If there is voltage drop on the MGN the meter socket will be at elevated potential in relation to the earth and if the MGN opens on the supply side of the meter socket the socket will be hot.