Induced Voltage

[safetman1]

I have a question, Is there a proximity between lines and induced voltage? and is there an amount of voltage before another line can be induced? We had an instance where there was a 13.8 line that had fallen and a 69 line (hot) right above it. Was there a potential for induced voltage on the fallen line or does it depend on the distance between the different voltage lines? Any help in understanding this would be appericiated

[thrasher]

There are lots of factors that affect induced voltage. The higher the voltage the easier to induce voltage. A parrallel line will induce more than a crossing line. The longer the parrallel the more the power that will be induced. It all boils down to if you share a r/w with another line then you must ground your line to discharge any induced voltage and leave a ground attached while working. The lowest voltage I have seen make a problem was a 34.5kv induce onto a 12.5kv line where they shared the same poles for three miles. I have been told of it happening with 12.5kv lines top and bottom but have not seen that myself, however since we routinely ground it's probably just a case of the line didn't have enough time to build a charge.
By the way I have also seen induced voltage between a 500kv line and the gutter and downspouts of a house at the edge of the r/w. I personnally measured 87 volts on the gutter before we grounded it to the consumers ground rod.
Stay safe.

[lineman-up]

yes there is absolutely a good possibility of induction working under 69line. i have been knocke to my knees by induction on a 7200 volt line before. the moisture in the air and the distance between lines would factor into the induced voltage . there is a lot of factors in this equation and i dont know the math to figure it out. just ground it and work it as if it is hot

[safetman1]

Thank You for the replies, I am sure you can tell by the way I was beatin around the bush that yes I witnessed my guys working on a downed line and they did not ground the line, which is ok as long as you work it as it was hot. I am the safety guy for our company but I am not an OSHA cowboy, I just want my guys to be safe and go home to their families. I did stop the job and make them install grounds, the biggest factor was I was afaid that some small business might fire up the ole' generator and not kill their main. I am not a lineman but I have been associated in the industry for 20 years. I dont sneak around and take pics and I dont shove safety down my guys throats but...... There is a line between being safe and just plain dumb.

[Orgnizdlbr]

Thank You for the replies, I am sure you can tell by the way I was beatin around the bush that yes I witnessed my guys working on a downed line and they did not ground the line, which is ok as long as you work it as it was hot. I am the safety guy for our company but I am not an OSHA cowboy, I just want my guys to be safe and go home to their families. I did stop the job and make them install grounds, the biggest factor was I was afaid that some small business might fire up the ole' generator and not kill their main. I am not a lineman but I have been associated in the industry for 20 years. I dont sneak around and take pics and I dont shove safety down my guys throats but...... There is a line between being safe and just plain dumb.

No disrespect, but I would think a safety man would kow about the possibility of induction on parallel lines.

[500 KVA]

You say that it is okay to work those downed lines ungrounded as long as they treat it as hot.

What voltages do you expect your rubber gloves to be able to handle?

Inductance on lines can reach far above what a class 4 glove is rated to handle.

What is stupid is the fact that you don't know what you are talking about, but think you do. A lot of men are killed because of that same reason.

I'll bet you think bracket grounding is correct in that application as well. Bracket grounding will actually cause circulating current to be placed on a line with induction from another parallel line. Just like a trasnsformer works.

Single point grounding also known as Equipotential is the correct grounding application. I'm not saying not to ground every so many structures, but personal grounds need to be placed at the structure being worked as well.

Rubber gloves are not your cure all. If your in a transmission corridor with induction comming from a 500 KV line, do you think class 4 gloves rated for 36,000 volts are going to protect you? NO! They will not!

Maybe safety is not your calling. You've spent 20 years around the industry and apparently haven't learned too much.

[Stick-it]

ever hear of step potential safetman?

[billfoster67]

They sent up a kid with an inspector to inspect towers. I don't know if you remember this one. The inspector told the kid push in the cotter key in a little farther, but didn't realize there was an insulator on the static, to run cross river lighting or cross airport lighting to run the FAA lights, there was a PT on the other side running off the induction. 1st step apprentice killed.

Induction has so many formulations, an Ugly's book and buch of meters wont do it all. You just have to know its there, and to take extra care. I would use a stick to mess with anything unground above and below underbuild. On a tower- the tower is basically a ground rod and working off that is a death wish, or even meyer structure. Insulated ladder-Insulated stick to do what you need to do!

[lineman-up]

well stated 500kva. safetman-- ya kind of have to take 500kva with a grain of sand. he pretty much says what ever he thinks , but he is smart as hell and i was hoping he would see this post. if anyone would know how to figure this out it is probably him. How do you get to be a safety guy? our safety guy comes out barking orders all the time not knowing what the hell he is talking about, i finally told him where to shove it. we now have an older retired lineman as our field safety guy. that is the problem with this stupid safety shit, any apprentice lineman has probably experienced induction at some point by touching something that was energized by induction. but now the safety industry is going to hire people to protect us the have never been a lineman, come on!!!!!! i just dont understand this.:confused:

[Bull Dog]

Whats that old saying its better to keep your mouth closed than to speak up and remove all doubt.

[Stick-it]

A bracket ground will not protect you any more than using no bracket if it is on the next pole down. Bracket grounding the earth mid span would be a tough task to do. Substations use buried ground grids to do this. Grounding both sides and jumpering across the break is the safest method I can think of for being on the ground.

[electric squirrel]

If your talking about induced voltages on ungrounded lines, don't forget about the wind factor! E.S.:cool:

[500 KVA]

You must remember that bracket grounds will never protect you if the line becomes accidentally energized. If the circuit becomes energized the grounds placed on the line act as a bolted fault. They are suppose to take the line out as fast as the curve settings on the breakers are set.

Until those breakers open up there is still energy travelling down that wire towards you. Grounds do not sweep that voltage down to the ground, not letting anything past them like some sort of gate guard. Its not the path of least resistance. It is all paths with any kind of potential will be travelled. You will get that electrical voltage until the breaker has run its programmed sequence. whether it is 3 shots or 1 shot.

Then there is induction. You never know what your dealing with when voltage is being induced onto a circuit. Like Bill 67 said, sticks are the only way to remain safe *[if you are not going to place yourself at the same potential]. Gloves may work a few times. We all seem to get away with something a time or two. But do you want to be the worker who tries working on a line when the induced voltage is twice the rated voltage of the gloves your using? Not me! Gloves give a false sense of security.

The key with grounding is not using grounds with the belief that they will trip the circuit fast enough to help you. They wont. Breakers working at peak performance will not trip faster than 3 to 6 cycles if your lucky. And that is faster than a great many breakers out there. At the voltages we deal with, that is enough to give you ventricular fibrillation, cause asphyxiation or at the very least nervous system damage.

Grounds must also be large enough to handle the maximum fault current. You need to know what the max. current could be on that line. 2/0 copper grounds and even 4/0 copper grounds might not be big enough to handle everything system out there. You may need to parrallel two sets of a particular size grounding set. Maybe even 3 sets.

You must become one with the wire, AND your surroundings. Grounding and jumpering a downed wire is fine, but if your standing on mother earth, you are at a different potential than the wire and those grounds. A difference in potential will cause a voltage rise and then add the resistance of your body and current will now begin to flow. Enough current and you have major problems. It doesn't take much.

If you're standing on the ground, use a matt and bond it to the wires you'll be working on along with the jumpers and grounds. That puts you at the same potential. A bird on the wire so to speak.

If you are working out of a bucket, you need to make sure that anything you could possibly make contact with while doing so is also at the same potential. You could accidentally bump into the pole. That would be enough to be lethal as well. It only takes a slight brush up against something like a pole, down guy etc...

I said that I still believed in grounding a transmission line every mile or so. I also believe you must use single point grounds (Personal grounds) at the location where you are working.

Putting grounds on a line even a few spans apart will cause a voltage rise on the wire when Like E.S stated the wind blows. Wind can induce enough emf to cause voltage to flow. Putting two sets of grounds on the line will allow the formation of a simple transformer. An emf on the conductors between the two sets of grounds, and through the actual ground itself between those two sets of grounds will cause a current to flow in the wire.

I said that all in one breath. Whoooo!

Simple for me to say this: Bracket grounding alone = Bad practice.

It has been proven too many times since the mid 1950's when an engineer from Puget Power first realized the cause of linemen dying on de-energized and grounded transmission lines. He developed the equipotential grounding procedure we still argue about now, back in the mid 50's.

Look how long it is still taking us to understand it. Throw out those old wives tales guys. In this case they are dangerous!

[safetman1]

WOW!! Thanks for all your great comments, I might not not be much of a safety guy but... I can read. If you were to look at my original post you will see that I am not talking about 500kv lines I was talking about 34,000 volts and second your right I am not a lineman but the guys that were working on that downed line are, and they were doing it UNPROTECTED. Now with that said I guess I could have barked put grounds on use your rubber gloves! but once again they are lineman with 20+ years of service, I am not a lineman. I guess everyone wants to blame the safety guy which is ok as long as you go home safe. I guess every lineman needs a good safety guy to hold his hand. Once again thanks for the input I plan on printing all this out including the safety bashing part and hold a safety meeting with my guys because I feel it is important for the guys to hear from their peers about voltage induction and the first 2 posts answered my question. ;)

[Stinger]

500, why did I feel like I just went to a refresher course in grounding. Good post. Remeber the post by Mike_ close call- had to do with this very subject.Safte1man, no offense, but with your lack of hands on experience, do not be surprised if a line crew lets everything you say go in the left ear and out the right ear and the crew will do their own thing and it will be safe. I think one of things utilities and contractors should institute is the requirement for the field safety personell should be a JL with a minimum of 10 years experience as a JL from the particular area of expertise, ie distribution, transmission, underground. Let the chief of safety be some safety degreed guy, after all that posistion is management and really has nothing to do with field ops. Just my opinion.

[electric squirrel]

500, why did I feel like I just went to a refresher course in grounding. Good post. Remeber the post by Mike_ close call- had to do with this very subject.Safte1man, no offense, but with your lack of hands on experience, do not be surprised if a line crew lets everything you say go in the left ear and out the right ear and the crew will do their own thing and it will be safe. I think one of things utilities and contractors should institute is the requirement for the field safety personell should be a JL with a minimum of 10 years experience as a JL from the particular area of expertise, ie distribution, transmission, underground. Let the chief of safety be some safety degreed guy, after all that posistion is management and really has nothing to do with field ops. Just my opinion.

Amen,,,,,E.S.:cool:

[jimmymac33]

Equipotential grounds Both sides of you. Bring your self and line at or to the same potential as what your working on. They buy the stuff for you to use and they allow you the time to use it. So use it. Problem solved
Seen induction bury an ole boy from Ga.
And it don't make a damn safteeman1 whether it's 500 kv as the conversation detoured to or 400 volts know your stuff and bark the orders that you are paid for. You are paid to look out for the men and women that do the work that pays your salary..
Where you from by the way? You sound supect of the SAFETEE Man from the company that I just left ( in south Fl) that just had 3 folks burned (flash) on thursday 8/9/07 one of which was a apprentice and had to be airlifted out..

Leave each day the same way you came with 21 appendages.

[buzzit125]

I had a good friend killed from the same BS 25 years ago, induction is no joke. It is a very dangerous threat, for any lineman or cub. No way to measure the potential of voltage stored in the paralleled lines. Work on getting good information to your men. Safety is not just a thing we talk about, it is a way of life. A culture that is bread into a lineman, no books can put it there, it is always best to ask questions first then act. You came to the right place Safetyman, don't get scared now... Its not dead till it's grounded.

[safetman1]

Once again Thank You for all the great posts negative and positive. I will continue to use this site I do believe there is a wealth of information here that cant be learned from a book.