Utility Co. Wiring Metal Light Poles In Ma.

[romeo]

For those who received Mike Holts October code questions and answers. Question #8 regarding a utility co. employee wiring metal light poles with out a equipment grounding conductor,and depending on a ground rod to provide a fault return path. Mikes agreed that the utility co. was not required to do the work by NEC standard.
But also explained how dangerous the installation was.

I am a wiring inspector in the State of Massachusetts. I came across the same situation at a subdivision of 35 homes with 12 light poles in the town where I work. To make matters worse these poles do not have any overload or short circuit protection. The circuits are tied directly to the secondary of the transformers by way of the utility hand holes. Also the neutral conductor is not insulated at the pole connection
I complained to a utility official who told me that they are exempt from local inspection.

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 am now in the process of getting an interpretation from town council.

This may be a way to finally get the utility co to stop killing people by there ungrounded light poles. I will post the results as they happen it may be useful for Massachusetts electricians.


Any comments or suggestions will be greatly appreciated.

I believe that a egc. should be run all the way back to xo of the transformer and not only back to the hand hole in the event that the neutral should become open from the hand hole to the transformer creating a parallel neutral from the pole to the hand hole, should the egc be run only back to the hand hole.

 

[jtester]

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

romeo

Electric utility systems usually don't have an egc. Their neutral is considered the ground in most cases because they operate a multiple grounded system.
Secondly, with grounded systems utilities almost exclusively rely on the earth to be part of the ground fault return path.
Finally, it is common practice for utilities to not provide overcurrent protection for individual lights, changes in secondary conductor size, etc. Where I work, the utility regularly does exactly what you describe, we call them flat rate street lights, which means they are not metered.

If you undertake the task of redesigning this utility practice, I commend you, but encourage you to consult with utility engineers as well.

Jim T

 

[charlie tuna]

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

these installations are killing 349 americans each year. a simple test would be to ground the hot conductor to the pole and determine how or if the ground trips the overcurrent device. if not i would red tag it and bring it to the attention to your supervisor. many times the return conductor is damaged and "open" but the fixtures operate on a high resistance ground path via the ground rods -- but will not clear a ground due to it's high resistance. and when a hot wire comes in contact with with a metal surface like a pole or metal bus bench enclosure -- they become energized and a public death trap!!! the use of system ground conductors should be required and the use of ground rods should be deleated!!! my $.02!!!!!!!!!!!!!!!

 

[Jhr]

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

I am a wiring inspector in the State of Massachusetts.

I'm not trying to be a smart a--, but is wiring all you inspect or are you an electrical inspector, I have never heard it put that way, in those words "wiring inspector".

 

[romeo]

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

jtester thank you for your reply. If the utility co. is using the neutral as a ground to bond the metal pole, all I want is for them to show me that there will be no touch voltage from the pole if the neutral back to the source should become open. Also how do they open the circuit if there should be a ground fault to the pole with or without overload protection? Will 110 volts provide a path back to the source through the high resistance of earth?

Thank you for your interest i know there is a long row to hoe should this small time inspector try to challenge the utility co. but I think there is a serious danger here and trying my best to correct it.

I maybe wrong. I am just looking for someone to show me that no one will be hurt should I not do my job.

Thanks again romeo

 

[romeo]

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

Jhr Sorry I guess I should have used the term Inspector of wires. That is the official term as I know it.

 

[Jhr]

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

Are you sure these poles don't have inline fuses installed, seen and done this, ie stadium lighting. And another thing if a ground rod won't trip a breaker, and has any one done a test with one, and G-rods are not good as lightning protection as I know for a fact , then what the HECK are these piecies of metel crap good for and why do we even use them,is it just so John Doe can have a job making them and our suppliers selling them and then we sell them to our customers, thus making money on some worthless piece of metal crap, also if a cold waterline can clear a fault then is it that a g-rod can't, if this is really fact, when both are listed as permitted grounding electrodes !

[ November 03, 2005, 07:23 PM: Message edited by: Jhr ]

 

[romeo]

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

Jhr do not get confused. A ground rod or rods are used as a grounding electrode system for lighting and other protection for a service entrance.

I am talking about a equipment grounding conductor to provide a ground fault path as required in section 250.4 (A)(5) also note that the earth shall not be used as the sole equipment grounding conductor or ground fault current path

 

[Jhr]

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

for lighting and other protection for a service entrance.

Ground rods for the protection from lightning I very much disagree, and I know about the equipment ground, but to say that a ground rod will not clear a fault, I just don't know.

[ November 03, 2005, 08:14 PM: Message edited by: Jhr ]

 

[electricmanscott]

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

Originally posted by Jhr:

Ground rods for the protection from lightning I very much disagree, and I know about the equipment ground, but to say that a ground rod will not clear a fault, I just don't know.

I am by no means an expert but I do know from this board and Mike Holts teachings that a ground rod will not clear a fault nor is that its purpose.

Romeo I think you are doing the right thing but I have a feeling you are in for a tough battle. In Massachusetts and most states for that matter you have to have a dead body to prove your point. Then you might get something done if you find a hack politician looking for a headline to take the heat off their drunk driviing arrest.

[ November 03, 2005, 09:16 PM: Message edited by: electricmanscott ]

 

[shortcircuit2]

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

Romeo...
I too have seen how the utility company wire pole lights without a EGC and just install the supplementry ground rod. There is a development under construction where I have witnessed the same installation. I have also read Mike Holts latest about this potential hazard. But, trying to go up against a big utility company, like Nstar or Mass Electric, will be a long battle...but I do support your position on this hazardous issue.

shortcircuit

 

[Jhr]

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

I am by no means an expert but I do know from this board and Mike Holts teachings that a ground rod will not clear a fault nor is that its purpose.

Another job for THE MYTH BUSTERS. I wouldn't try it, I'll take Mike's word for it, but that been said what is the lowly, underdog, Rodney Dangerfield of electrical products ground rod that gets no respect suposed to acomplish, if not help clear a fault, after all it is part of the GEC system .

 

[tom baker]

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

" to say that a ground rod will not clear a fault, I just don't know"
Do the math.
25 ohms for the ground rod resistance.
120 V
Whats the current?
Will this clear a 15 amp overcurrent device?

 

[Jhr]

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

Ok Tom what is the ground rod for then ? A ground fault is an unintentional connection between an ungrounded conductor and any grounded raceway, box, enclosure, fitting, etc. Ground faults can result in a large magnitude current flow in the ground path. the amount of current that flows depends upon the resistance or impedance of the ground path. for example if a 120v. ungrounded conductor in a metal raceway is nicked during installation, a ground fault can occur. the amount of current that flows depends upon the impedance of the metal conduit back to the source of power, so the G-rod been part of the EGC system is part of this path so don't just take the resistance of the G-rod into your math problem the resistance measurement is a combination of all the metal parts that are bonded together, in the electrical installation, a G-rod just happens to be the electrical product that is driven into the earth which helps clear the fault.

[ November 04, 2005, 12:01 AM: Message edited by: Jhr ]

 

[pierre]

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

At light poles, ground rods if the voltage is less than 600 volts are useless, that is correct they are useless. There is so much misinformation pervading the grounding issues, that are frankly quite scarey. Just do the math, it is simple - as Tom has shown. Remember Tom showed 25 Ohms as part of the math. Usually the CONTACT resistance of a rod is many times higher than 25 Ohms.

Again Rods are USELESS. Don't just say they are doing something, show me the math to prove me wrong.

FOR ANYONE WHO THINKS THAT THE GROUNDING ELECTRODE SYSTEM IS IN PLACE TO HELP CLEAR A GROUND FAULT, IT IS NOT!!!! Do the math.

Okay why do we install them? I have not got a clue. Do they help for lightning protection? Any pole light that takes a hit from lightning will not survive the hit, I do not care how many rods you install.

 

[Jhr]

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

[/QUOTE] FOR ANYONE WHO THINKS THAT THE GROUNDING ELECTRODE SYSTEM IS IN PLACE TO HELP CLEAR A GROUND FAULT, IT IS NOT!!!! Do the math.

Now I'm really And don't we want the least path of resistance to ground, so if the G-rod is not 25 ohms are less then it should be agmented by one additional electrode, so the more metal making contact with earth the least resistance there will be, is that a correct statement?

[ November 04, 2005, 06:48 PM: Message edited by: Jhr ]

 

[pierre]

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

Effective ground fault current path.

In our side, that is under 600 volts, the Equipment Ground Conductor - 250.118 lists the types permitted to be installed.

Remember that every electron (current flow) leaves a source (for services - a transformer, lets us say on a pole outside the building). All of the electrons want to, and will try to find any path back to that same transformer. If there is a fault, some of those electrons will flow on the Grounding electrode conductor, to the ground rod, through the earth, up the grounding electrode on the pole, then up the conductor on the pole to the transformer.

This is important to understand!!!

But.... most of the electrons will flow from the fault, onto the equipment grounding conductor (the effective ground fault current path) back to the service, over the main bonding jumper, to the grounded conductor (the neutral in this case) and back through the windings of the transformer, and finally back to the building on the phase conductor of the fault and then the overcurrent device will open (trip). Whew!! who says it is easy being an electron?

So, the short answer is the equipment ground - whether that be a conductor or the raceway, etc...

did that help?

[ November 04, 2005, 12:50 AM: Message edited by: pierre ]

 

[pierre]

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

In understanding what I just posted, the neutral(grounded conductor) that is installed from the transformer outside to the house is a very important conductor. It serves two functions.
1. as the incoming neutral conductor.
2. When a fault occurs in a house, the neutral conductor becomes the path back to the transformer from the house for "most of the fault current". If you were to lose the service neutral, you can see how this will also create a potential safety hazard, as there will not be enough current flow on the GEC system, and then the overcurrent device will not open during a fault condition.

I mentioned that the GEC system is quite useless for fault conditions. The EGC is extremely important for the proper functioning of an overcurrent device during a fault condition.

[ November 04, 2005, 12:59 AM: Message edited by: pierre ]

 

[jtester]

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

Most of the comments and statements made so far are based on how a NEC designed system operates, 25 ohms or less, etc. A utility system operates much differently. They have the equivalent of a ground rod at almost every pole, at almost every electric service, there are thousands per mile in some locations. To compare their grounding system to ours is inaccurate.

Secondly, there usually are no overcurrent devices to trip when a street light circuit shorts to ground. The first OCPD is on the high side of the transformer in many cases, and it won't even blink for a street light short. Contractors and designers often put fuses in poles to fuse individual lights, but I am not aware of that practice in utility work.

Finally, this is a serious problem, and I am not defending a utility's right to maintain a system that appears to be unsafe to many. However it is a fact that their system doesn't closely resemble ours, and to try and compare the two just draws ideas that are often inaccurate.

Jim T

 

[eprice]

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

Originally posted by Jhr:
Ok Tom what is the ground rod for then ?

In the words of NEC 250.4 it is to connect the system to the earth "in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation."

A ground fault is an unintentional connection between an ungrounded conductor and any grounded raceway, box, enclosure, fitting, etc. Ground faults can result in a large magnitude current flow in the ground path. the amount of current that flows depends upon the resistance or impedance of the ground path. for example if a 120v. ungrounded conductor in a metal raceway is nicked during installation, a ground fault can occur. the amount of current that flows depends upon the impedance of the metal conduit back to the source of power, so the G-rod been part of the EGC system is part of this path so don't just take the resistance of the G-rod into your math problem the resistance measurement is a combination of all the metal parts that are bonded together, in the electrical installation, a G-rod just happens to be the electrical product that is driven into the earth which helps clear the fault.

As you point out, the amount of current that flows in a path depends upon the impedance of the path. Tom is pointing out that the impedance of a ground rod alone, without considering all of the other impedance in the path, will be enough to limit the current in that path to a low enough level that it can not be relied upon to clear the fault. In a service covered by the NEC, the path with a low enough impedance to clear a fault does not go through the grounding electrode system. It follows the EGC to the main disconnect, then over the main bonding jumper to the service neutral, then via the service neutral to the source. The EGCs are not useless in this scenario, in fact they are essential, but it is not because they lead to the grounding system, but rather, because they lead to the service neutral.

For a light pole installation to be safe, there has to be a low impedance path provided for fault current to get back to the source. Because of their high resistance, this path cannot rely upon ground rods.