Equipotential Grounding

[500 KVA]

Concrete is as good a conductor as anything else.

The entire equipotential theory for underground cable in duct and vaults, is designed for underground vaults made of concrete.

This is what you need to do with concrete.

If you get your concrete pole manufacturers to weld every joint where the rebar is joined together instead of just wire tying it. Put brass studs from that rebar to the outer part of the pole, at the proper locations. A place where you can place your grounds onto those studs.

Then you will have the desired level of protection for equipotential. That rebar has to be welded, not tied when joined. That's an added cost.

[MAD's]

Yes, that is what different pole manufacturers are going through now but it doesn't help with all the concrete poles in the system now. The idea of running a copper conductor, attached to the pole from the x-arm bolt down to the expected cluster bracket has been suggested but some engineers believe it is creating another hazard on the pole especially when gloving. I don't know how much of an extra hazard it would in fact create as the concrete pole itself would have covers applied if gloving anyway.

[500 KVA]

Are you gloving energized primary from a concrete pole? You should be using an insulated baker board.

If we are talking about de-energized, then how would copper being added around the pole be an added hazard? If you make it temporary. Only when de-energizing and grounding work will be done. Then remove it just like a cluster bar when the work is finished.

You guys need to figure it out somehow. Bracket grounds alone will cause a potentially lethal voltage rise at your work location if the lines became energized. You cannot argue the mathematical fact in that.

Maybe if you ran a piece of the stainless steel pole banding, that you would use to mount things onto a concrete pole, around the pole and bonded to it like a pole band.

Don't give up. Someone there has to be capable of figuring it out. I wouldn't listen to that AEP study though. Bad information.

[wudwlkr]

AEP apparently is refusing to release the actual test methods and data to any one else to study. Their lawyers have advised them not to do so. Got to wonder why. They did do a presentation before a committee from IEEE that writes the grounding standards used in the US to try and get their buy in. According to an individual who was at that presentation, the data AEP presented was not very informative. While the test results presented did show lower voltage levels across a worker on a pole using their methds, their own test data showed that installation of a cluster bar as in traditional equipotential grounding still provided the best level of protection.

Georgia Power did something similar while back in an effort to get out of an OSHA citation received during hurricane cleanup work in the gulf a couple of years ago. Turns out they only used a test voltage of 480 volts and claimed it was a safe method becasue a lineworker could stand on the neutral and be protected. If there is a ground cable connected between phase conductor and neutral and you are standing on the neutral you ARE IN an equipotential zone, probably the best one possible. FWIW

[old lineman]

Concrete is as good a conductor as anything else.

The entire equipotential theory for underground cable in duct and vaults, is designed for underground vaults made of concrete.

This is what you need to do with concrete.

If you get your concrete pole manufacturers to weld every joint where the rebar is joined together instead of just wire tying it. Put brass studs from that rebar to the outer part of the pole, at the proper locations. A place where you can place your grounds onto those studs.

Then you will have the desired level of protection for equipotential. That rebar has to be welded, not tied when joined. That's an added cost.

Hi 500KVA
I was reading your posts re; welding rebar as opposed to wire tying where the rebar intersects. Up north here they use too much salt on the roads I know, but. I have seen concrete poles with whole slabs of concrete missing.
This is because the rebar is rusting and expanding when it does. The force pops the concrete off.
This also happens on bridges and what they are doing for a solution is coating the rebar with epoxy (it's a pukey green color).
This would eliminate the possibility of welding once the rebar is delivered to the pole manufacturer.
I believe this will eventually be the standard to lengthen the life of these poles. I think it would be better to spec a cad welded braided copper lead to use for grounding instead.
Your engineers would be responsible for the specifications.
I am also puzzled by your statement about using a baker board on these concrete poles. First of all you can't climb these poles so the work must be done from a manlift, therefore, to use a bakerboard you would have to disembark.
Appears silly from my view point. Am I missing something?
This deal about a ground lead puzzles me also. Grounded circuits need a lead somewhere, what's MAD's talking about? Your right on that one.
By the way. I have been reluctant to say anything but in my former life I wrote the script for an Equipotential Zone video. The intent was to have a well laid out way of explaining the technical aspects of creating an EPZ.
I checked with E&USA here in Ontario last week and they have distributed about 200 copies around the world.
Apparently IBEW has purchased many for training purposes. Lots of good feedback.
For anyone who wants to have one for educational purposes contact www.eusa.on.ca
I would like to hear somefeed back from anyone who has seen it.
The Old Lineman

[old lineman]

I've always thought EPG was really, the most effective method of grounding for the safety of a Lineman. I actually used the AB Chance Video when I taught it. Haven't seen yours....Would really like to!!

Upload it to Utube!! :-)

Thing about EPG is...

it's time consuming in setup, in most cases... to be truly effective. It has to be done correctly. Have you ever seen that AB Chance Vid on EPG Oldlineman? Hell...think it was back in 99-00...probably not used anymore.

So....Is EPG All Bullshit nowdays? Any of you guys out there....or your companys...actually practice it...daily?

Yes I've seen it but was less than impressed. Perhaps it's because I'm biased or perhaps computer animation can add so much clarity.
The producer said he could make the whole video using animation but I knew that we needed to show the real thing or linemen wouldn't buy it. We used animation overlayed on real scenes which worked really well.
The video cost about $65,000.00 so it was taken real serious. Anyway I was pleased with the results and the positive feedback.
The Old Lineman

[rat1369]

the method i have used is put the cluster about 2 ft below the neu/secondaries. if there is a pole bond, bond the bracket to it. if not run a temp bond. also cut breaks in every potential feed and jerk xfmrs open. there have been some reports of people having contacts with traditional bracket grounding. Any dead work i'm doing i insist that every way is covered that could energize a line. if i cant completely be sure of it i still glove it

[mainline]

We use EPZ on transmission at our utility, but we bracket ground on distribution. When we ask why the difference we get a lot of blank stares. Then we got a song and dance about the bolt for the primary neutral acting as a pole band. They couldn't give us an answer on how this was going to work when the neutral was by the crossarm braces. I have seen the chance demonstration video of what bracket grounds will do when energized. It doesn't give me a warm fuzzy feeling being next to them in hooks, but the company says it is the best way.

[lewy]

We use EPZ on transmission at our utility, but we bracket ground on distribution. When we ask why the difference we get a lot of blank stares. Then we got a song and dance about the bolt for the primary neutral acting as a pole band. They couldn't give us an answer on how this was going to work when the neutral was by the crossarm braces. I have seen the chance demonstration video of what bracket grounds will do when energized. It doesn't give me a warm fuzzy feeling being next to them in hooks, but the company says it is the best way.

On your bolt for you primary neutral are you using a hubbard clamp?
In my oppinion it is better than the pole band, in some places in Ontario they only use the hubbard clamp & some use both.
How far are you away from your grounds? we were told you could be no more than 300' from a set of grounds.

[old lineman]

We use EPZ on transmission at our utility, but we bracket ground on distribution. When we ask why the difference we get a lot of blank stares. Then we got a song and dance about the bolt for the primary neutral acting as a pole band. They couldn't give us an answer on how this was going to work when the neutral was by the crossarm braces. I have seen the chance demonstration video of what bracket grounds will do when energized. It doesn't give me a warm fuzzy feeling being next to them in hooks, but the company says it is the best way.

In our neck of the woods Hydro One settled for using a through bolt and they manufactered an extension to screw onto the through bolt to provide ample space for a duck bill clamp.
We looked at it and decided NO. For many reasons including;
1. It's at a fixed location and may or may not be were it should be.
2. Current flowing across the pole will be mostly on the surface and a through bolt only contacts the surface area under the washers, this is NOT adequate.
A mulitude of testing proved beyond doubt that the most effective method of capturing the current flow was the have a metallic band snuggly fitted over the surface of the pole. The A B Chance pole band was chosen (other companies also make them).
A pole band has to be made from a non-corroding light material such as aluminum cast that is curved to more or less fit the shape of a pole and there should be a copper bar of adequate length to allow a grounding clamp from the neutral, a grounding clamp from the primary and a grounding clamp to a ground rod if the the system is rural (some times you may even want another duck bill for the truck grounds).
We always want to ensure the protection system will see enough fault current to operate. In the rural setting even then it may not, however, the lineman won't be injured if he/she remains within the EPZ until something gives. All he'll have to do is change his shorts.
Obviously if there is no neutral a ground rod is the only choice.
The pole band has to be placed not more than 8 feet beneath the lineman's feet. Sometimes that may be beneath the system neutral.
My advice is don't mess around with the system. It's been researched up, down and sideways and this is the best protection that can be provided.
The Old Lineman