ground sizes

[BULLogna]

Lookin for info on what size grounds most people use for personel protection. My illinois company mandates 4/0 as the only acceptable size. Thats comforting on a 138 or 69kv line but it is alittle big for most distribution especiaslly #6cu. They want us to ground to a #2cu or 1/0 al neutral or go to a supplimental. I trying to get the powers tobe to allow 2/0 grounds for distribution depending on wire size. my theory is if a ground is easier to use, it will be used more. thanks

[loodvig]

All we had was 4/0 grounds. They took all the smaller ones off the trucks years ago.

[LeadHead]

We use 2/0 copper grounds on 12 kv and under anything larger gets 4/0

[HIVOLTS]

Our grounds are sized for the amount of available fault current. Up to 25ka we use 2/0, up to 45ka we use 4/0 and up to 75ka we double up 4/0.

[PA BEN]

Length is important too. Saw a video of long grounds becoming energized and the whip of the ground broke the ground bars in a substation.

[lewy]

All of our grounds are 2/0, but we only work upto 44kv

[mainline]

Everybody out there seems to be using larger grounds than we do. We only use #2 copper grounds on distribution. I would be willing to bet they are too small for some of our fault currents, but our engineers probably couldn't figure out the proper sizes.

[wudwlkr]

Does not matter what the voltage is. The only question is how much fault current is available and how fast will the breaker operate. Grounds have to be sized to handle the fault current for however long it takes to clear the fault. May very well need to have 4/0 on distribution.

Pa Ben is also correct, shorter is better. Long ground will whip possibly injuring you. Also longer grounds means more impedance which means the grounds will get hotter and more likely to fail.

[JAKE]

#2 here

our largest sub is a 50mva 14.4x25.6 grounded wye they say thats more than enough they just went through makin sure that was large enough.

[lewy]

I agree the fault current is the main criteria & for substations 4/0 may be required but for general utility purposes we use 2/0.
length is also important it is a matter of balance too short & you mite have to join them, too long & you could get into the wipping problem.
If you use equipotential grounding you could keep them far enough away to minimize the wipping problem

[BULLogna]

I realize fault current is the main factor but when your going to a 1/0 neutral whats the purpose? A relay is lookin for excessive current so am i being protected by a 4/0 phase to phase short ? otherwise my ground fault neutral should be at least the same size as my ground. I also wonder if the ground is assuring me that the line is dead and my lock out tag is protecting me from energizing but I have had lines heated up on my grounds. Either way I am not arguing the ground fault capability is important. I am just wanting to know if most hands are trusted to pick the proper ground size for what your groundin. right now I am breakin my company rules if I choose to find a smaller ground for grounding #6cu or even #8cu 12kv which we still have in the air. Thanks for the input guys


"its better to be lookin down than lookin up"

[BULLogna]

I know short ground theory is important but I can only carry so many sizes. And using single point grounding I like to have the grounds long enough to transfer with out having to re ground usually about 12'. You have to pay attention when you got hot under build and cover things up.


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"better to be lookin down than lookin up"

[old lineman]

Coiling ground leads is a big no, no. It causes high impedence to the flow of current. Perhaps your only coiling a couple of loops which you can get away with but if the grounding cables are stored on a drum everything should be stripped off.
By the way high impedence will cause high heat which in turn will melt the cable cover.
As for size of cable most utilities standardize on 2/O because there will be fault currents on their system that requires this size.
Generally 4/O is reserved for the substation setting. Sometimes the substation crews will be required to parallel 2/O cables due to the fault current available.
I found that IEC (europe) standards are slightly more stringent than ASTM standards. Their information must be readily available on the web.
Any supplier will provide the fault current vs. cable size info without question. Your engineering department can provide the available fault current information.
The Old Lineman

[old lineman]

As you all know current cuses heat. The only method of preparing a high flex cable to be treminated is by compressing on a ferrule before tightening it into the grounding clamp.
Never sweat any fittings using lead.
Lead will melt out and the connection will fail before the protection clears it in some cases.
The Old Lineman

[Special ED]

Back in Louisville we only had 2/0 grounds. I would usually keep 12 ground chains on my truck mostly 6 foot and a few longer ones. I believe OSHA has a standard on minimum sizes and 2/0 is it if I'm not mistaken. Atleast thats what the office told us..

As for coiling the grounds... Yeah thats a huge no no... It builds up too much heat and in some cases will act like the coils in a transformer and blow up. We had a saftey video the apes had to watch and on our trucks the ground was coiled up and hung in the rear bin on the truck with the lead made up to the frame on the other side of the bin. Well the video showed the ground only taken out enough to make it to the neutral and they put a fault on it. WOW you talking bout one hell of an explosion!! They also showed the same sceanareo on one of them automatic ground reels on the back of a truck.. Same thing only it didn't put a bin door in orbit.

[JAKE]

i remember seein that video, remember the ground rod shooting out of the ground like a rocket!!

we use ep grounds here quite a bit when ya only gotta put one up it can be quicker depending on circumstances. i still think its safer also. when i first saw it i was a sceptic also, we just happened to put a new sub in with nothing on it so we set it up in real life on a 14.4 line put a pot on the line to act like a person put my fluke 189 hooked up to the pot, had the ep ground setup and closed the sub in she hit and there wasnt the slightest bump on that meter after that test i definately belive in it. i wanted to try it with bracket grounding but after the boss saw the line buckin like it did he didnt let us

[Special ED]

Speakin of the ground rods shootin out of the ground.. We used to have the old screw grounds and the forman instructed the guys to use it on the tensioner ground and rolling grounds while we reconductored a hot 12Kv route. They just barely put the screw in the ground and made everything up. Well needless to say with the windy day and the boss being in a rush the new wire would occassionally bump the energized circuit and everytime the screw ground would jump and through dirt in the air. Boss insisted on pulling anyways and never did knock out the line. Since then they banned the use of the screw grounds and everything is made up to the system neutral.. They used to ground to pole grounds as well but thats a no no now as well.

[mainline]

Driven ground rods are not a really good ground. I can speak from experience. We sounded one out, about 4 feet when it hit ledge. We then hooked it up to a running ground on our wire trailer. What we didn't know was that the P-line was wrapped around a phase, when the wire got there it energized the trailer. It burned three out of the eight tires flat. It also burned a tire on the digger truck we had hauled the trailer with. I was on the trailer for the ten minutes it took to for a lineman to get through a work zone and kill the circuit at the sub. The recloser never even bumped. We now only use the system neutral for a ground. Strangely enough we have to use a 2/0 ground to ground our equipment for pulling though we only use #2 for personal protection during restoration. Go figure.

[wtdoor67]

Anybody ever seen that ......I think it was AB Chance training Video on Omni potential Grounding? I saw it in the early 90's, 93 I think it was.

The one with the little fake 3 ft. line and the lightbulbs connected with alligator clips?

Does anybody out there ACTUALLY DO...Omni Potential Grounding? Is it "Hocus Pocus", or what.

It sure looked good in Theory.

and then again in about 87 or 88. It was not made mandatory at either place I was working. It as just kind of presented as perhaps a good method. Seemed to me it worked but I don't recall anybody using it. I had actually forgotten what it was called but Omni Potential sounds like it.

[BULLogna]

Didn't that video compare a cluster ground assembly to single point grounds that were too long?






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"better to be lookin down than lookin up"

[Special ED]

It burned three out of the eight tires flat. It also burned a tire on the digger truck we had hauled the trailer with.


Did you not have the trailer tired off at the tie down points with bull ropes or slings?? Thats a big no no for me. We don't leave pullers and tensioners or wire trailers hooked up to trucks. They are tied off to them but not hooked up. Mainly for that reason.. Burning up a trailer is bad enough but burn up a truck and your kickin rocks and counting insulators back to the shop..

[Smitty57]

At my company we use 2/0 C.U. for distribution and 4/0 C.U. for x-mission.
Two 2/0 grounds can be used in place of one 4/0 provided they are the same length.

[JAKE]

we leave the trailer hooked up to the rig here but we have the sub in hotline tag when were reconductoring and one tiny bump and whoops the sub is open!! some times hlt is a bit too sensitive i was up changin an arm and all the sudden dispatch is callin for me see if im ok, dang tree touched the line somewhere and opened it but it was just fine in normal.

[JAKE]

THAT's Cool Jake!
Yup, that's the one....with the groundrod comin out of the ground! :D

I really don't think many Utilities actually use it though. The KEY I believe to EPG is....really settin that groundrod, the correct depth and distance. AND setting up EPG takes time....

One hell of a video training film though. Anybody find it posted anywhere? I looked all over Google, and couldn't find any reference to it.

So....Anybody else, ACTUALLY USE Equi Potential Grounding?

we have the tape at the shop i can see if i can get it loaded to the net

i like the ep groundin i only gotta put one set up, quicker than bracket grounding the only thing is ya cant get them off from the ground

[graybeard]

Where I'm at they have gone to EPG and it was a big fight in the begining. The guys are getting used to using that method of grounding. You kind of have to go job by job to set up your grounding. When they had the training when they wanted us to start using EPG they didn't cover every senario. We just got done helping another grew change out 69 wishbone on an uprate job and put up 1 set of grnds to a driven grnd and then EPG at the pole we were working on.
So here is COMPANY policy, 2/0 for dist.,4/0 for trans EPG when possible and on trans with system neut. and just a static then a driven grnd. And the grnds should not be any longer then needed.

[1st Class Husker]

I agree with jake and mainline , we also use #2 Copper grounds!

I use them very honestly, but in my opinon grounds are hung to verify the line is dead, not to save you , you will most likely get killed if holding on to a grounded line that gets accidently energized!

[Trbl639]

with us....4/0 inside the sta fence, and on Transmission......

on distribution 2/0 from outside the station until conductor size drops to 1/0, then we can use #2 grounds on 1/0 and smaller........

[230kv]

before 14 years our personal ground 2/0 from 69 kv to 230 kv until one day… my foreman sent me to assist U/G unit by bucket truck to install personal ground for them on some of 69 kv line tower,
By some big mistake dispatcher energized the line :mad: while we are working??? Suddenly Big explosion I heard???
We was very lucky, our grounding completely damaged and burn , no any injury, just some of our clothes burn…but after that our engineering decide to use ground 4/0 which is very heavy:cool:

[Stinger]

Fault current is what determines the size of grounds to use. I've grounded 345kv where the utility has told us to use 2 4/0 grounds on the masters to the bracket. From the bracket to the grid system use 2 4/0 grounds. length does matter. A job we are working now, reconductering a 115kv line our safety man in his safety plan obtained the ground fault current for the particular lines we are working. We are at 110. What he also said in the plan that if the ground fault current exceeded 125, we were to use two 2/0 grounds instead of a 4/0 ground as the two 2/0 will handle 136. It distributes the heat more easily and faster. As for personal ground we could use 2/0 as long as we were between masters. As the JL title stands for JUST LEARNING, this is the first time a safety man has explained in writing a plan the reason for doing things. This guy used to work for National Grid Transmission and has never given us bad info, one of the few that will come on a job site to correct and teach instead of writting things up.