EPZ grounding

[LAMartin.CVEC]

Definately understand the concept of the EPZ, and do believe in it.

I honestly thought that a driven ground rod was an important part of creating the EPZ, but Lewy said he doesn't use the ground rod. Just bonds with the pole bracket installed to the system neutral. No ground rod. Thanks for the 10 ohms info. That I didn't know.

Mr. OLD the idea around Equal potential "grounding" has nothing to do with the GROUND or ground rod. but rather that every thing in the work zone that's "grounded" is at the same potential.

You do not need a driven ground to achieve this you simply need every thing bonded together. If every thing is bonded to the system neutral as well as bonded to an "earthed" ground all the better.

The problem with EPZ (again focus on Equal potential ZONE not EPZ grounding) is when you work on delta and single wire earth return systems. That problem is quickly resolved when if you realize that your not "grounding but rather providing an Equal Potential Zone. If everything is connected correctly it matters not what system your working the worker is at the same potential as the work.

To many of us get hung up on the jargon and to not realize the facts behind it.

How man of us "ground" our trucks or in fact just bond them to the system neutral?

Work Safely,

L.A. Martin
Journeyman Div III
CVEC

[LAMartin.CVEC]

I guess we will just have to agree to disagree

What is the Difference Between Grounding and Bonding?
A. "Grounding" is a method of connecting an isolated conductor to some type of ground in order to trip the circuit as quickly as possible and minimize voltage rise on the circuit. Grounding, by itself, does not protect a lineman from harmful shock currents.
B. "Bonding" is a method of physically interconnecting conductive parts to maintain a common potential. The objective of bonding is to avoid harmful shock currents by minimizing any potential difference across the lineman's body. An adequately-sized jumper is used to tie the conductor / circuit / equipment to a bonding point such as an equipotential band or ground mat / grid below the lineman's feet.

The ground rod just helps clear the fault, it has nothing to do with the EPZ you created with the pole band.

Agreed.


Work Safely,

L.A.Martin
Journeyman Div III
CVEC

[lewy]

Lewy was pretty right on with his explanation. According to the National Electric Code and OSHA any ground must be at 10 ohms or less to be effective. If a company does not test their driven grounds when installed to ensure the ground is 10 ohms or less then they are not following OSHA guidelines. The ground shown on the picture of an EPZ is mainly for step potential but does give some help for circuit tripping depending on your area soil type. The phase to phase jumpering is to trip the circuit as quickly as possible since the station breakers will see that fault the quickest. Once you have your phase to phase jumpers to neutral established, all you have to do on an adjacent pole is jumper from the neutral to your pole bracket to make your EPZ. Of course every situation can be different because of soil type and effectiveness of the neutral but that should have been pre-established by the company engineer. Another issue is Transmission, because of the fault current and inductance it is always the best to establish the EPZ at the work location.

As far as companies in Florida not using EPZ, then they are not following OSHA guidelines and are walking a tight rope. I believe I am correct though by saying that most companies in Florida require there lineman to always wear their rubber gloves when not using and EPZ. Most of the crews that I have been around in Florida just find it easier to wear their rubbers than take the time to set up a proper EPZ, which is just personal preference.

Just a note for you history buffs, Equal Potential Grounding was first tested and instituted by Bonneville Power Administration in 1958!! It was called the Straw Man Test.

I can't understand wearing rubber gloves compared to proper grounding, it is either laziness or ignorance . I think people have a false sense of security that nothing can go wrong wearing there rubber gloves. I know that the odds of something going wrong are small, but why play those odds. I doubt that they are worried about touching a phase with part of there body while wearing there rubbers. In my opinion when working on a line EPZ is the only way to go, then put your rubbers away as long as there are no energized conductors on the pole. I know what it's like to wear rubbers gloves in the high humidity here so I can't understand with the high humidity in Florida why you would want to wear rubber gloves when not necessary.

[linemanfrog]

As others have stated the EPZ practice is done to make everything in the work zone the same potential. Since there is no difference in potential, there is no current flow, and hence no eletrocution. In incident prevention magazine a few years back there was a good article about this practice as well as how a few companies, (I think AEP was one cannot remember the others) had performed testing and found that the pole band alone did not always work.

Much has to do with moisture content of the pole, type of wood treatment, etc. They found that a pole ground that was bonded to the neutral with staples driven in a certain distance, spaced a certain distance placed with the pole band served to more effectively create an effective EPZ. With that being said, you never really heard of EPZ very much until companies began insulating their neutrals on spools. Prior to that they were installed on metal attachments that were bolted through the pole. Also companies would usually run a pole bond to the top of every pole.. When a worker grounded one of these lines, the effectively created a EPZ grounding practice due to the nature of the pole construction. Perhaps we should start re-evaluating our construction standards as to why we insulate the neutral on spools, do not install pole bonds on every pole, etc.

I've worked in FL for 16 years or so in the trade and I have never seen workers wear rubbers on a dead and grounded line. Perhaps some do, but I cannot see why.

[US & CA Tramp]

As others have stated the EPZ practice is done to make everything in the work zone the same potential. Since there is no difference in potential, there is no current flow, and hence no eletrocution. In incident prevention magazine a few years back there was a good article about this practice as well as how a few companies, (I think AEP was one cannot remember the others) had performed testing and found that the pole band alone did not always work.

Much has to do with moisture content of the pole, type of wood treatment, etc. They found that a pole ground that was bonded to the neutral with staples driven in a certain distance, spaced a certain distance placed with the pole band served to more effectively create an effective EPZ. With that being said, you never really heard of EPZ very much until companies began insulating their neutrals on spools. Prior to that they were installed on metal attachments that were bolted through the pole. Also companies would usually run a pole bond to the top of every pole.. When a worker grounded one of these lines, the effectively created a EPZ grounding practice due to the nature of the pole construction. Perhaps we should start re-evaluating our construction standards as to why we insulate the neutral on spools, do not install pole bonds on every pole, etc.

I've worked in FL for 16 years or so in the trade and I have never seen workers wear rubbers on a dead and grounded line. Perhaps some do, but I cannot see why.

This scenario in your 1st paragraph was discussed in depth at the Distribution, Transmission Partnership meetings about 8 years ago. These meetings were attended by utilities, contractors, IBEW, & OSHA from all over USA, and two representatives from Canada. The ground on the pole with the bracket over it brought up by AEP is what we called a DUH. Any body with one eye and half an ass would agree that would help lower the potential on the pole. The chances of reaching a zero potential is few and far between. but it was agreed by all that the goal was to lower the potential on the pole to an acceptable level so the body would not be bothered by the difference of potential. I could go on about all the references discussed and used in these meetings, but not now.

As for your 2nd paragraph I respectfully disagree with all of it. I can make a list of several Utilities back in the seventies that used EPZ and could not work on the lines any other way because of the amount of fault current and inductance at the work sites. Even if they worked the lines as if they were energized the inductance would eat them up. The only reason that a lot of companies didn't use EPZ years ago was because there was not the fault current available like there is today so they got away with out using it.

Working a circuit hot instead of grounding with EPZ has always been an alternative. I have found that most small municipals, co-ops, and one county lineman don't grasp the facts of these issues and concepts.

[lewy]

As others have stated the EPZ practice is done to make everything in the work zone the same potential. Since there is no difference in potential, there is no current flow, and hence no eletrocution. In incident prevention magazine a few years back there was a good article about this practice as well as how a few companies, (I think AEP was one cannot remember the others) had performed testing and found that the pole band alone did not always work.

Much has to do with moisture content of the pole, type of wood treatment, etc. They found that a pole ground that was bonded to the neutral with staples driven in a certain distance, spaced a certain distance placed with the pole band served to more effectively create an effective EPZ. With that being said, you never really heard of EPZ very much until companies began insulating their neutrals on spools. Prior to that they were installed on metal attachments that were bolted through the pole. Also companies would usually run a pole bond to the top of every pole.. When a worker grounded one of these lines, the effectively created a EPZ grounding practice due to the nature of the pole construction. Perhaps we should start re-evaluating our construction standards as to why we insulate the neutral on spools, do not install pole bonds on every pole, etc.

I've worked in FL for 16 years or so in the trade and I have never seen workers wear rubbers on a dead and grounded line. Perhaps some do, but I cannot see why.

This is what we use. We still have to use the band although I personally feel the Hubbard gives us better contact with the pole.

[bobbo]

I understand it with induction rather than accidental switch. When you put that bracket on and your climbing and you just bond the wire doesnt burn your hands. You can feel it. I know about that poor guy with end of arm bracket. And I feel his pain. Because he works probably multi circuit, multiple arms and there is no place to put that bracket. If he is from CA, there is no room. The only eight foot arms that guy sees is in a backyard single phase delta. Instead of a buck arm, they will install and end of arm bracket, tapped witb kee rite in conduit. The reason they use they use those brackets is they have three to four foot spacing between circuits and they cant fit an arm in there. I feel your pain. You have to go to California to see it. I have worked on poles with ten circuits on it. Twelve foot arms with a circuit on each side and sub t on top. I actually had a journeyman lineman GF tell me there was no such thing as a seventy foot distribution pole, (he was so one county boomerville). When I have been everywhere else, a 40 or forty five were stub poles or secondary lifts, or single phase backyard poles. When they see positecs here they think are like the most dangerous things, they will bypass because the are afraid to open them. I know what you are saying, but I havent seen an end of arm bracket except for Cali and no one will understand except for someone in Cali. To epz that circuit you would probably have to go to to the take off pole to do the circuit. And you couldnt do it with the.end.of arm bracket. Because there is too much crap.

[lewy]

I understand it with induction rather than accidental switch. When you put that bracket on and your climbing and you just bond the wire doesnt burn your hands. You can feel it. I know about that poor guy with end of arm bracket. And I feel his pain. Because he works probably multi circuit, multiple arms and there is no place to put that bracket. If he is from CA, there is no room. The only eight foot arms that guy sees is in a backyard single phase delta. Instead of a buck arm, they will install and end of arm bracket, tapped witb kee rite in conduit. The reason they use they use those brackets is they have three to four foot spacing between circuits and they cant fit an arm in there. I feel your pain. You have to go to California to see it. I have worked on poles with ten circuits on it. Twelve foot arms with a circuit on each side and sub t on top. I actually had a journeyman lineman GF tell me there was no such thing as a seventy foot distribution pole, (he was so one county boomerville). When I have been everywhere else, a 40 or forty five were stub poles or secondary lifts, or single phase backyard poles. When they see positecs here they think are like the most dangerous things, they will bypass because the are afraid to open them. I know what you are saying, but I havent seen an end of arm bracket except for Cali and no one will understand except for someone in Cali. To epz that circuit you would probably have to go to to the take off pole to do the circuit. And you couldnt do it with the.end.of arm bracket. Because there is too much crap.

10 circuits on 1 pole what voltage is that at? At the top of my head the most I think we run is 4 and most times when we have multiple circuits we will be anywhere from 60' to 70' poles, but we are armless with 6' between circuits and 5' between phases with a 10' neutral.

[Trouble1]

I still don't see how you get an EPZ without a bare stapled down ground going all the way up to the pole top pin. Using that picture as an example, let's pretend you are climbing to tighten that k-line and lets say that the pole band is half way between the neutral and phase and your feet are a foot above the band. With your bare hands on the phase and your feet above the pole band, are you really in an EPZ? There is resistance between parts of the pole without the bare ground. Am I overthinking this or not? And what about all the other utilities that may not be bonded that are within reaching distance?

I have nothing against using it on distribution, just curious...

[bobbo]

If gets even wierder when edison and a city share a pole. To get to the secondary, you have to climb through primary of the other. I have seen five to six arms on a pole, 12 footers, with circuits on each side of the arm. I have seen Southern Cal Edison runs the sub t (either 34.5 or 69), then 16 kv primary, then 12 kv, primary, then a lot of circuits 2400/4160. I remember I had to change out wood pins in long beach and I dont think the spacing was even bucket width, I went through a box and a half of glass on one structure. It would have been easier and safer to climb. If you get to a heavy industrial areas of some of that city, you will have all kinds of arms and circuits. Because some circuits are dedicated. Ladwp is 34.5 sub t, and 4800 delta, and I heard they have 7200. And if you want to sometging special lewy check out there smith corners. I remember changing out 16 foot arms with 4 arm stiffeners catching budle copper bigger than 4/0. That structure broke off the feed four ways, distribution, on a 120 foot pole. It was 40 feet of all arms on top. I didnt have to use my hooks for the top because it was a big jungle gym. California is a different animal of the trade. You will see something new everyday sometimes good and sometimes bad. Now they are taking down the open wire and putting it on arms, bussing it to both sides. Then you might have another arm have 3 phase secondary. It takes awhile to get cut in. And when someone from California makes a comment on here, I love it, because the things there are so hard to explain. When you have 16 million people in that 240 square miles, their system is complex as that city.