another electricution - metal street pole-baltimore!

[petersonra]

Re: another electricution - metal street pole-baltimore!

Originally posted by charlie tuna:
i think the national electrical code should consider evaluating the practice (and the practibility) of installing ground rods at poles.
one life is too many to loose when it can be prevented, and prevented by reducing job installation and maintainance costs. it may also help to educate people about grounding and bonding!

I don't see how this would solve the problem. Driving a ground rod would not cause those who are responsible to maintain these structures to actually do so. Nor would it likely cause an OCPD to trip in the event of a ground fault.

The ground rod will help the pole deal with a lightning strike, but bonding the pole to the source is the only thing that will prevent electrocution from a ground fault.

As for installing a ground rod, don't most poles already have a concrete encased electrode as their base? If you want to require grounding of light poles it would probably be better to just require a connection to the rebar or mesh thats already there rather than trying to add a new rod. It might not meet the 20' foot rule, or use mesh rather than rebar but I wonder if it might make a better GE than a driven rod. Besides, where would you put the rod? Someplace where it might be subject to damage?

[ December 27, 2004, 11:32 AM: Message edited by: petersonra ]

 

[tom baker]

Re: another electricution - metal street pole-baltimore!

"i think the national electrical code should consider evaluating the practice (and the practibility) of installing ground rods at poles.
one life is too many to loose when it can be prevented, and prevented by reducing job installation and maintainance costs. it may also help to educate people about grounding and bonding!"
Read the link to the article I wrote. the ground rod will do nothing to prevent electrocution if the pole is energized. If you feel otherwise, can you post the math that shows how a ground rod will solve the problem?

 

[physis]

Re: another electricution - metal street pole-baltimore!

It's completely possible that I'm underinformed. I have to admit that I only know about it if I hear about. Is this being swept under the rug. Are there substantially more occurances than most people are being clued in on.

I'll restate my comment.

Given all the municipal metal everywhere and my level of informedness I am lead to (and I think reasonabely) conclude that the metal to incident ratio is pretty good.

 

[charlie]

Re: another electricution - metal street pole-baltimore!

Sam, if a 747 crashes, everyone knows about it. If someone gets hurt on a street light column . . . Of course the same applies to traffic signal columns.

It is my belief that there are indeed some dangerous columns out there and will be repaired if they are reported. I don't think there are many (any?) manhole rings and covers that are dangerous (I think this was a freak accident). If this were a really bad situation, there would be a lot of people getting hurt or killed and that is not the case.

 

[charlie tuna]

Re: another electricution - metal street pole-baltimore!

don--member #4,
the reasoning i use to suggest that the ground rod installation should be evaluated and possibly discontinued is:
1)it has never been proven to me, nor have i ever seen where lighning damage is prevented or lessened by the use of a ground rod at a pole.

2)that the additional green wire connected to the ground rod and routed into the wiring compartment adds to the confusion of the person wiring and maintaining/repairing the pole.

3)too many people who are wiring and/or maintaining these installations consider the ground rod a low impedence path back to the power source. if this practice is stopped, they may ask "why" and then learn how important it is to confirm a return path for fault current.


i have heard of at least five people being killed by energized manhole or handhole covers in the last five years. and the touch hazard for this is very small compared to a pole or bus bench. the practice of bonding metal hand hole covers will help. this webb page contacts many people in our industry and thats why i bring it up---"food for thought"! it hurts me to read about two sixteen year old boys being killed by an energized street light pole because the person repairing the pole thought the ground rod provided a proper return path to the poles power source.

 

[don_resqcapt19]

Re: another electricution - metal street pole-baltimore!

Charlie T,
I guess I'm not reading your original post correctly. I read it as asking for the use of ground rod. Sorry.
Don

 

[physis]

Re: another electricution - metal street pole-baltimore!

I have to appoligise in advance because I haven't read all or even most of the posts.

I may be demonstrating my ignorance but I'm just gonna say it the way I see it.

Forget about NEC terminology.

If you have a metal pole.

You have a transformer.

If you connect the neutral from the secondary of the transformer to both the metal pole and the earth. Does this not make a safe grounded installation?

Even if you don't have a neutral you can do the same with one side of the secondary.

Is that wrong?

What is so complicated that nobody can understand it?

Is it me. Do I also not understand it?

 

[charlie]

Re: another electricution - metal street pole-baltimore!

I have heard of at least five people being killed by energized manhole or handhole covers in the last five years.

Charlie, I have a real problem with this statement. I am wondering if we are talking apples and apples? What is the definition of manhole that you are using?

What I am talking about is a large rectangular concrete bathtub that is buried and is large enough for people to get into to work. It has concrete "windows" that may be knocked out and a duct bank installed and cables racked around the sides. The entrance(s) are concrete tubes that extend upwards from the roof to grade level and terminate in a manhole ring where a manhole cover that weighs around 300 pounds will be set.

Is this the same animal you are talking about?

 

[charlie]

Re: another electricution - metal street pole-baltimore!

Sam, you are correct and have just described the way that grounding is done in the NESC. If these metal columns are in a parking lot and served from a supermarket, the columns must be grounded to a grounding conductor. The grounding conductor than takes the fault current to the main bonding jumper, then to the service neutral, then back to the transformer.

You are right, this should not be a big deal.

 

[charlie tuna]

Re: another electricution - metal street pole-baltimore!

charlie #59,
yes--thats what i would consider a manhole and i also included handhole covers. the manhole cover was somehow energized by reinforcement steel that was in contact with the yoke of the cover. the person contacted the manhole cover and a grounded steel plate encased in the curb.

 

[physis]

Re: another electricution - metal street pole-baltimore!

Charlie, thank you for confirming my sanity.

Honestly, I think we're creating terminology barriers with this stuff because the concept is not difficult.

 

[physis]

Re: another electricution - metal street pole-baltimore!

I have to say this.

 

[charlie]

Re: another electricution - metal street pole-baltimore!

Sam, that is why Don's proposal will change grounding to bonding in most of the locations throughout the Code in the 2008 Cycle. When we use the term grounded, we are really meaning bonded and it is confusing if you are not really on top of the terminology.

 

[physis]

Re: another electricution - metal street pole-baltimore!

I agree that might help.

But I also think we're traversing further into the abiss that brought us here.

 

[physis]

Re: another electricution - metal street pole-baltimore!

I just read through almost all of this, like I should have at first.

What I'm seeing is that these incidents are a result of plain and simple sloppy work.

I think perhaps the problem is supervisory.

These things seem to have happened because nobody bothered to make sure it was OK.

 

[don_resqcapt19]

Re: another electricution - metal street pole-baltimore!

What I'm seeing is that these incidents are a result of plain and simple sloppy work.

Maybe not. Up until a few years ago there was never an EGC pulled to traffic signal equipment in Illinois. The just drove rods and bonded the metal poles and standards to the driven rods. There was no way to clear a fault, and this was per IDOT design standards.
Don

 

[charlie tuna]

Re: another electricution - metal street pole-baltimore!

most of the electricutions i have heard about is the result of unqualified people or qualified people who mis-understand the correct method to properly ground metal surfaces exposed to the general public. for this reason, most of the cases are just considered "accidental deaths"! who would be blamed--the county official who hired an un-licensed person to maintain light poles? or the county commisioner who allowed a sign contractor to install electrified bus benches on county property without inspections or permits?

consider what happens when a street light pole gets knocked down by a motor vehicle? what happens to the wiring in the raceways to and from the pole? maybe nothing? maybe something very serious! in most cases, do you think the person replacing the pole confirms the continuity of the bond conductors in each raceway back to the source and to the pole down stream? it could effect a pole down stream by the movement of wires. in most cases the power company is called to isolate the effected pole's wiring. then a contractor is hired to replace the damaged pole. this is where the problem usually starts!

 

[physis]

Re: another electricution - metal street pole-baltimore!

There was no way to clear a fault, and this was per IDOT design standards.

Well, I'm kind of stretching it a little but I'd say that standard is sloppy work.

And not checking to see that a pole is correctly repaired and not just stood back up is certainly sloppy.

 

[charlie]

Re: another electricution - metal street pole-baltimore!

Up until a few years ago there was never an EGC pulled to traffic signal equipment in Illinois.

Don, I don't have a problem with that if they would have grounded the columns to the system neutral the way we do. I would have thought the IDOT engineer would realize that the earth can't be used for the return.

 

[physis]

Re: another electricution - metal street pole-baltimore!

You know, it occurs to me that the parking meter coin boxes never get ignored!

I'm trying to think of a second comment.

Don't have to, it speaks volumes.

Edit: The utter diligence that that task is performed with just fills ones heart with pride!

[ December 29, 2004, 05:01 AM: Message edited by: physis ]