Power line safety procedures

[k0ua]

This video might help a bit if out brush hogging you hit a guy wire and knock a power line down on your tractor.

 

[rekees4300]

That was interesting thanks. :thumbsup:

 

[k0ua]

Keep in mind that although telephone and cable TV lines do not normally carry lethal voltages, you do not know what damage was caused by your hitting of a power pole, or during storms. An energized power line may now be making contact with one of these normally non lethal cables and it may now be energized to lethal potentials.

Also for those of you that don't believe you can be shocked by the "ground", I will assure you that differences in ground potential can easily exist. You can see this in even fairly low voltage situations where for instance a direct burial 240 volt cable is buried in the ground and its insulation has failed. You can take readings with a voltmeter a couple of foot apart and often see a voltage difference in where the probes are stuck in the ground due to the flow of current flowing into the ground an all the way back to the equalization point. Now think in terms of if this voltage was at least 100 or more times greater, some lethal voltage gradients could be produced.

My point is, better not take a chance with downed power lines, and I think the video brought these issues to light.

 

[davesl708]

Good video k0ua.

The same goes for a tree branch that is shorting out on a wire. The branch and sap will make it energize the ground around the tree.
The typical distribution line running to the transformer that supplies your house carries around 7,200 volts. Nothing to mess with.

 

[joefromga]

That guy looked like a crack head.

 

[GaryM]

I'd seen that video recently and thought it was interesting and informative.

We had a tree take down the 7K line feeding our little subdivision last week. It hit the hot line and pushed it down onto the neutral where they both burned through. Then it caught the phone line which held the weight.

I was speaking to the crew making repairs and mentioned the advice given in the video. The lineman said he wouldn't depend on hopping of shuffling working, but then added "I guess you've got to try something".

Staying in the car is best if possible of course.

 

[4570Man]

The guy the hooked up the electric service to my house said he accidentally cut a 7,200 volt line with a chain trencher. He said it welded the chain to the bar.

 

[TCJatko]

Reminds of the time I was in Abbeville, LA at my parent's place, and during a thunderstorm we saw an oak tree touch against an overhead line. The tree would touch the line, the line would glow red hot and then the breaker would trip. The tree would pull away as the wind changed direction, then the touch the line again. Red hot glow, breaker trips, tree retreats. The happened about a dozen times. This was also a 7.2 KV line, I learned from the crew out fixing the problem. Dangerous stuff.

 

[GaryM]

You may have already seen this YouTube video of a tree on a high voltage line. Toward the end the power is cut, then reconnects several times.

ORIGINAL! Bellingham Carolina & Grant St Tree Fire Explosion 10.03.09 - YouTube

 

[k0ua]

The guy the hooked up the electric service to my house said he accidentally cut a 7,200 volt line with a chain trencher. He said it welded the chain to the bar.

I bet that was a pretty light show for just a little bit.

 

[Farmer2750]

We had a tree fall on our power lines feeding our yard, it was blocking the driveway and the tree was just leaning against the line. We called the power company and they said "there is storm damage in the south and we can't get a truck to you for 2 weeks at least." Well it's a good think the loader tractor has 6 rubber tires cause we couldn't stay blocked in at the yard for two weeks. Just picked it up with the loader and pushed it off.

 

[kco]

Even if you know a power line is de-energized and down, don't assume it will stay that way even if the power company has not repaired a downed line. Many people have generators now and some may not know how to disconnect their wiring from the power system. Feeding 240v through a transformer produces primary voltage through that transform and back through the system. So, if a primary line is cut and down, don't assume the "load" side is de-energized even though the source side is.

 

[kco]

We had a tree fall on our power lines feeding our yard, it was blocking the driveway and the tree was just leaning against the line. We called the power company and they said "there is storm damage in the south and we can't get a truck to you for 2 weeks at least." Well it's a good think the loader tractor has 6 rubber tires cause we couldn't stay blocked in at the yard for two weeks. Just picked it up with the loader and pushed it off.

Was the powerline energized? If so, you got away lucky, or their was a good path through the tree to ground. There are MANY incidents with cranes and trucks contacting overhead lines and blowing out all the tires.

 

[coobie]

We had a tree fall on our power lines feeding our yard, it was blocking the driveway and the tree was just leaning against the line. We called the power company and they said "there is storm damage in the south and we can't get a truck to you for 2 weeks at least." Well it's a good think the loader tractor has 6 rubber tires cause we couldn't stay blocked in at the yard for two weeks. Just picked it up with the loader and pushed it off.

I need you to buy me a lottery ticket,you got lucky.

 

[k0ua]

Even if you know a power line is de-energized and down, don't assume it will stay that way even if the power company has not repaired a downed line. Many people have generators now and some may not know how to disconnect their wiring from the power system. Feeding 240v through a transformer produces primary voltage through that transform and back through the system. So, if a primary line is cut and down, don't assume the "load" side is de-energized even though the source side is.

A very good point.

 

[Qapla]

The power company that services our area says "if a line is not grounded, it is not dead" - so, they attach a grounding line to each wire before they do any work even when they were the ones who pulled the switch. They even ground the common/ground wire. They also will no longer allow a technician to work on a "feed/hot line" if he is by himself. He can work on the ground/common/return line when alone - but there must be at least two techs for then to be able to service a "hot" wire - which usually means they bring two trucks since they seldom have two techs in one truck.

This has been a real benefit as they frequently find "dead" wires to be energized by a private generator while they are repairing downed/broken lines after/during a storm.

 

[My Hoe]

Good video--thanks for posting.

Though I think it could have benefited from some editorial input, saying:

STAY OFF THE ******* WHILE DRIVING, unless you have a proven ability to do two things at once...and I realize even that is very subjective and NOT as good as my first observation.

These comments, below, from the youtube video, made some sense to me:

"USNVA1 month ago
Step potential conducting through each leg is possibility, but to minimize the shock, running is every bit as effective as keeping feet together. When a person runs they only have one point of contact touching the ground in the line of step potential. Walking has two points touching at once.
Alex Mamer
Alex Mamer1 month ago

You're right, that way your body would not complete a circuit."

However, upon further reflection it occurred to me that perhaps "shuffling" is advisable over running, in case you ARE injured/shook up, don't know it, and fall down on the (potentially) energized ground (no pun intended)--or even trip on debris, as you're in unfamiliar territory, it could be dark, slippery, etc.... Just my .02.

But I'll be passing the OP's video on to others so, again, thank for posting.

My Hoe

 

[k0ua]

Yes, I thought it would be a good reminder for those of us that have had some safety training, and maybe an eye opener for those of us that have not.

About 20 years ago a friend of mine was driving in his pickup truck and encountered black ice and a dump truck. He managed to not collide with the dump truck, but in taking evasive maneuvers he hit a power pole. The dang power transformer (pole pig) fell on the cab of his pickup and dang near smashed him. he managed to jump out of the truck without getting shocked, but then rolled down a steep hill. That didn't do him any good. And it took some time for him to crawl back up this steep icy hill. He crested the hill about the time Law Enforcement arrived. I wondered what had happened to him. You just never know the things that might befall you. He was in his 20's, it was not like he was some old decrepit dude. Like me.

 

[kco]

The power company that services our area says "if a line is not grounded, it is not dead" - so, they attach a grounding line to each wire before they do any work even when they were the ones who pulled the switch. They even ground the common/ground wire. They also will no longer allow a technician to work on a "feed/hot line" if he is by himself. He can work on the ground/common/return line when alone - but there must be at least two techs for then to be able to service a "hot" wire - which usually means they bring two trucks since they seldom have two techs in one truck.

This has been a real benefit as they frequently find "dead" wires to be energized by a private generator while they are repairing downed/broken lines after/during a storm.

I think grounding de-energized lines before working is standard practice for all utilities. If there it is a fully grounded neutral it is usually acceptable to connect the three phase wires to the neutral because it is connected to many grounds along the circuit.

Another hazard is induction from parallel lines. In 1967 I saw an unintended demonstration. Our crew had de-energized a stretch of 3 phase 12 kv distribution line strung below a 72 kv transmission line. Two of our crew were up a 90 degree corner pole and had grounded the three phases by attaching the ground clamp to one of the guy wires which were in turn bonded to the system neutral. One of the linemen decided the ground chain was in his way. I even remember him saying so, and stating he would move it to the other guy-wire, 90 degrees from the one it presently was on. He disconnected the clamp from the existing guy wire (the other three clamps were still on the phases of the de-energized phases), and while holding that clamp in one hand, grabbed the guy wire to which he was going to transfer the ground clamp with the other hand. That's when he let out a heck of a noise, yelling "I can't let go". It went on for a few seconds. Luckily, the second person was an experienced and quick-thinking journeyman; plus I think he already had pliers in his hand for doing some work. He immediately reached over and cut the ground chain. No real harm was actually done and they both continued working, after we sent up a new ground chain.

The person who made the mistake was a fourth-year lineman who had been in to write his journeyman's exam that same week. Once it was clear things were OK, our foreman yelled up something like "that's a heck of a thing to do for someone who just wrote his journeyman's exam", but not in those words.

The lineman broke a couple of rules: the ground end should always be connected before the phases and rubber gloves and hot stick are to be used when installing the phase grounds.

This incident is also a good reminder that low voltage systems can be just as deadly as high voltage systems.

 

[Travelover]

This idiot needs to watch a video about not using a cell phone while you drive. He could have killed someone instead of hitting the pole.