Special grounding for street lighting installed under high voltage overhead lines?

[Muzikp]

Doe's anybody have experience with street lighting under transmission lines? Specifically where does the NEC cover how to ground street lights placed under transmission lines?

Working on a street lighting project which is installing 30' street light poles under transmission lines. See photo below, the new roadway will travel under transmission tower the arrow is pointing to.

I'm told that street lighting under these transmission lines require special grounding?

Thank you for the help.

 

[Muzikp]

Anyone? Any ideas where I should look? IEEE? Somewhere there must be information regarding grounding street lights under high voltage transmission lines?

Any help or random thoughts/ideas appreciated.

Thanks.

 

[Microwatt]

I would say if you ground the poles per the NEC (Arts. 250 & 410) and follow any local requirements you should be ok. Maybe check with the mfg. of the poles or the power company that ownes the over head lines to see if they have any recommendations. Obviously the towers supporting the lines are much closer to the lines then your poles will be so you shouldn't have to get too crazy. In my state we have to drive a seperate 1/2"x10' copper ground rod for each pole over 12 feet (or use 25' of 1/2 "rebar) but that is regardless of location.

 

[PEDRO ESCOVILLA]

individual light poles do not require a separate ground rod. it's a waste of money, unless you're trying to make a lightning rod out of the light poles. light poles must have an eguipment grounding conductor termination in the handhole (410.30 (B) #3). pull an egc with your power to the poles. if they require additional grounding, that will be spec'd by a design engineer, dealing with transmitted eddy currents or the lines of flux from the high tension lines which may be "wide"

City of Kerrville, TX​

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, if you will. you may want to check with the poco who owns the lines under where you are installing the lights, as well. what you are asking makes perfect sense. i worked on a fence job years ago in valejo cal., abnd there were high voltage lineas above where we worked. if we leaned on the pick ups, we'd get shocked if they were too close or directly under neath the power lines. not sure how the "junk" got in there, but i can't get it out!!!:rant::lol:

 

[iMuse97]

Whether or not the ground rod is a waste of money, most local jurisdictions around here require it, apparently wanting to incur the cost of that wasted money.

 

[Cow]

Don't do it......

I've serviced some poles under transmission lines that'll give you a pretty good zap when you work on them. My glow stick would go off in my back pocket every time I'd touch the fixture. They had an EGC but I doubt there was a rod.

 

[kwired]

Will you be running parallel or perpendicular to the transmission line? That will likely make some difference in what kind of voltage is induced into your equipment.

If voltage is induced and you install grounding electrodes current will flow. You effectively have a transformer. Place a steel core with conductor wrapped around it and you have a better transformer. If voltage is induced and you don't install grounding electrodes no current flows and voltage levels will be higher. The more often you place grounding electrodes the less resistance there is in current paths the more current flows dropping the voltage even more on what is not that good of a transformer in the first place.

I know that in places where I have seen similar lines they bonded all the wires together of any fencing located near the lines every so often to minimize voltages between the fence lines. Can't recall for certain but I believe they also connected bond wires to a ground rod, which would make sense with my theory above.

This is just my theory, go ahead and disprove it if it is wrong.

 

[iwire]

Whether or not the ground rod is a waste of money, most local jurisdictions around here require it,

Based on what code section?

 

[iwire]

The company I worked for some time a ago did a large parking lot under transmission lines and the poles chosen where very short. Instead of 27'-31' poles like we would have normally used these where more like 14'-17' and of course a lot more of them. The lot looks funny.

I have no idea if the use of shorter poles was actually required or if it was just a design decision with perhaps some forward thinking regarding servicing them later.