Mike Holt has pointed out in his Grounding and Bonding text thousands of metal light poles are not grounded.
Here is an example I ran across recently in eastern Washington State.
The metal light poles (OK Luminaire Standards) are installed across a river bridge, the orginal poles were on the concrete railing. These poles are fed overhead at 120V or 240V, unfused from a transfromer via triplex to the first pole, and then open insulated conductors on insulators to the rest. There is no ground wire in the overhead feed. Also at one point there is a high voltage line (12,500 V) above the open street lighting feed.
Some one went to a lot of effort to install the secondary insulator rack. It would have been much faster (and code compliant) to use triplex. These type metal lighting poles are not designed for overhead feed.
Paul: The majority of "street lighting" around here (NJ) is utility owned and maintained. Some is overhead, some is underground, and some is a mix of both. A recent "street scape" project (business area rehabilitation) job utilized utility installed decorative poles (metal) w/ lantern type HID luminaires. They ran PVC to the new poles from the OH grid, and ran triplex to each pole. The ground (earth) consisted of a driven ground rod at each pole.
The utilities also install & maintain parking lot lighting (site lighting). Some consist of metal poles, UG wiring from a pad mount transformer, triplex in the PVC, and a ground rod at each pole. Apparently, the utility is exempt from installing a grounding conductor "pole to pole", and also are not required to "bond" all the rods.
The poles are all individually controlled by a photo cell at each pole/fixture.
Hope this answers your questions.
PS: Almost forgot; I have not come across too many like the photos. John
[This message has been edited by HotLine1 (edited 06-30-2003).]
Re: Light Pole Violations#114808 06/30/0301:57 PM06/30/0301:57 PM
Maybe the angle of the photo is deceiving, but there doesn't appear to be much clearance for half a million volts!
John, Thanks for the info. It just looks odd to see overhead lines and insulators on metal poles. I don't ever recall seeing that combination before, even in America.
Over here metal lamp standards are always wired underground. Where lights are needed with overhead wiring, they're generally just individual bracket lamps fitted to each wooden pole (although overhead lines in areas built-up enough to have street lights have disappeared rapidly in the last 20 years or so).
They ran PVC to the new poles from the OH grid, and ran triplex to each pole. The ground (earth) consisted of a driven ground rod at each pole.
Do you mean that the metal poles were connected only to a ground rod, and not bonded to the neutral in any way whatsoever? (What would be called a "TT" system here.) If so, then is the feed via a GFCI ?
[This message has been edited by pauluk (edited 06-30-2003).]
Re: Light Pole Violations#114810 06/30/0310:05 PM06/30/0310:05 PM
Paul: quote: -------------------------------------------------------------------------------- They ran PVC to the new poles from the OH grid, and ran triplex to each pole. The ground (earth) consisted of a driven ground rod at each pole.
To respond to your questions...
To the best of my knowledge, there is no GFI protection on our utility lines, as the 120/240 volts is obtained from pole mounted transformers. This 120/240 supplies various loads, street lights, site lights, traffic signals, and customers.
Again, as far as I know, the grounds (earth) for the poles is via a driven rod, unless the neutral from the triplex is tied to it inside the poles. I have no jurisdiction as AHJ on the utility equipment, and I have not seen the inside of these poles. We removed a utility metal pole (site lite) that was hit by a truck, and it's ground (earth) was only a driven rod. (120/208 volt feed in triplex in PVC)
Hope this answers your questions. Perhaps BJarney has some input; or one of the "line guys". John
Re: Light Pole Violations#114812 07/03/0305:38 AM07/03/0305:38 AM
I'm just looking at the situation from a purely technical view: If the post is grounded only to a local rod, then the loop impedance may well be high enough that a short wouldn't open any OCPD and would leave the pole hot. Not good.
Re: Light Pole Violations#114813 07/07/0306:01 PM07/07/0306:01 PM
I've got the same situation out in front of my place. OH duplex wire. They're putting the utilities all underground right now. My street's ripped up, and a big pain in the tailfeathers. (No access covers to the poles, I'll get a pic when they pluck the poles, and send it in)...S
Re: Light Pole Violations#114814 07/08/0308:08 PM07/08/0308:08 PM
Paul: A side note; the only OCP that I know of is the primary fuses at the pots (transformers) Or some pots have a resetable CB device built in. I have no clue of the ratings; the pots range from 25 to 75 KVA usually. John