Downed power lines safety tips

hot_rod

https://www.youtube.com/embed/fLVzvMTgGDY

Zman

Puget Sound Energy does some great stuff.
And here I thought we were just trying to avoid licking the power line.

KC_Jones

Worked for the power company for 7 years. One of my job requirements was to drive around and investigate every customer all of downed wires, yes we are required by the PSC to personally investigate every single call that comes in.

I showed up on one that I thought was locked out (thinking can be dangerous). Wire hanging about 12" off the ground, maybe a little more. Well when the wind blew it would swing to a higher spot on the ground and arc.

This was a 34kv line, which in our world wasn't "high", but it's enough to get you re-evaluating your life choices in a hurry. I was standing about 10' from it when it arced, my partner and I moved to the other side of the road and I proceeded to smoke 3-4 fine tobacco products in a row. Thankfully it is standard procedure to close the road regardless of live or dead "just in case". When the lineman came back in his truck, we told him what happened and he got a good chuckle.

Those lineman have them screwed on really tight, I have seen them grab a live 13kv line that was arcing. Talk about trust in your PPE.

hot_rod

Zman said:

Puget Sound Energy does some great stuff.
And here I thought we were just trying to avoid licking the power line.

Never about the shuffle away part?

Solid_Fuel_Man

Ground potential is a crazy thing, cross too many ground rings at once and poof! Reality is that the line on the ground would most likely have faulted and a (hopefully) fuse blown.

KC_Jones

Solid_Fuel_Man said:

Ground potential is a crazy thing, cross too many ground rings at once and poof! Reality is that the line on the ground would most likely have faulted and a (hopefully) fuse blown.

You'd be shocked how long they will go, as long as it's under the fuse threshold it stays live. I watched one smolder on a tree for 3 hours one night, it was raining and I'm pretty sure that's the only reason the fire department wasn't there. Apparently the tree fell down about 6 hours before we got there.

Roughly 9 hours of live line on the ground under a tree and no trip.

Gordy

KC_Jones said:

Solid_Fuel_Man said:

Ground potential is a crazy thing, cross too many ground rings at once and poof! Reality is that the line on the ground would most likely have faulted and a (hopefully) fuse blown.

You'd be shocked how long they will go, as long as it's under the fuse threshold it stays live. I watched one smolder on a tree for 3 hours one night, it was raining and I'm pretty sure that's the only reason the fire department wasn't there. Apparently the tree fell down about 6 hours before we got there.

Roughly 9 hours of live line on the ground under a tree and no trip.

When I worked for Kewitt they had a laborer Forman scope a boom lift into the power lines. He cooked for over an hour and a half before power was disrupted by the utility company. So no don’t think there will be a fuse that will save you, or someone else.

JUGHNE

We had one of our common summer storms with 50-60 MPH winds and lighting. Over in less than an hour.
Went out with fire dept. as there was a branch burning between lines. Large branch was hung up in 69KV transmission lines and dangling down on lower under build of 13KV. Just hanging like a torch.
One of our "hotshot" guys was about to knock the branch away with a high pressure water hose. (Don't try this at home)
As I called dispatch to report the situation and mentioned the voltages, "hotshot" heard the numbers and backed off with the hose.....go figure.
Actually the 69KV was de-energized and the 13K (still hot) was backfeeding up to it. The 69 fuses/cutout was taken out by lighting.
Down the road 5 miles the 69 line had 2 broken 60' poles.
The wires were not on the ground yet, but close enough to touch, this 69 line would have been back fed by the 13K line 5 miles away.
We just let the branch burn and fall to the ground.....maintaining a safe distance as the hot 13K could have fallen also.

Even a cable TV wire on the ground during windstorms could be energized by high voltage contact any distance away.

BTW, those numbers of 69k and 13k are phase to phase readings. Phase to ground is only about 1/2 that amount....see safer isn't it.

Sal Santamaura

As I sit here in California, fortunately a safe distance of any active fires, but always susceptible to the whim of winds that might cause sparks from power lines, it seems the ultimate infrastructure project would be undergrounding all lines. From home service lines to long-distance transmission lines.

flat_twin

Telephone techs watch similar safety films every month and are required to check their B voltage testers and hot gloves. I got in the habit of using that B voltage tester every time I was working on aerial cable. We also watched some grizzly films that got your attention when things go wrong.
I was surprised, shocked actually, (pun intended) to discover the metal body of my company truck was picking up induced current from high voltage lines directly overhead. I'd get a pretty good zap if I touched any bare metal on the truck. I was standing on the ground at the time with the bucket stowed.
Sometime later I was working there on a wet foggy morning and you could hear the power lines sizzling. Scary stuff

ratio

Probably 25 years ago, during a rainstorm, I kept catching whiffs of an arc somewhere. I kept looking out windows & doors until I caught it, the wind would occasionally blow a residential primary into the trees & it would arc. I was on the phone to 911 when all of a sudden I heard a 60 Hz hum for a second & the line went dead. The next day I found the phone line to the house was down, & a ¼" notch was melted into it where the primary had dropped onto it. That's when I started drinking.

I cut the melted section out of the drop, still have it around here somewhere.

Leonard

Utility guys were doing mainatance work on towers of some cross country power lines nearby. Had pickup truck with trailer under the lines. I went and talked with them. Guy said if you touch the truck you'ld get a small ZAP. Vehicles had enough surface area that capacitive coupling to power lines induced enough voltage onto vehicles to give you a minor zap.

There are designs where you can use that capacitive coupling along with a spark gap to draw power from the lines to charge low power stuff like cell phones and run radios. Don;t need a car sized "antenna" , maybe umbrella sized will do.

JUGHNE

I started doing line work in 1977. Older guy was giving me some training.
He told me of high voltage fuses (2400 Volts) for transformers that would open and need changing.
These were a bayonet type fuse holder.
Imagine something similar to an AC disconnect pullout.
He would have to pull that out and then it would arc internally.
The clearances were not enough to break the arc.
He would put 2 fingers of his rubber gloved hand into the holder to break the arc. Then reload the new fuse link and insert back into the holder with his hands.
All this was done on climbing spikes, often at night in the rain.
So you learn to check your gloves often.
He was a fighter pilot over Europe in WW2, so this was not living as close to the edge as his flying time might put him.
That generation did things like this without worry.

Those fuse holders are all long gone, I want to find one for our museum. Few would appreciate what it was and the danger it imposed.

Solid_Fuel_Man

Here is a couple of recent ones. The squirrel blew a 5amp fuse on a 7200 volt line and took out a street this summer.

The aerial was fed by a common single phase 200A 120/240 service which shorted and this happened before the CSP in the can tripped.

Leonard

Squirrels .......funny thing but this summer I've been having trouble with them gnawing on aluminum........ garden tools, sheet metal, clean pizza pans, sheetmetal cab of 60's Jeep. Almost made it thru on the Jeep cab's roof, had to put garden anti-bug hot pepper wax spray on it ( habinero hot)

Why do they like aluminum?

JUGHNE

Dumb squirrel, if he would have looked, there is a squirrel guard below on the lighting arrester for his safety.

Jamie Hall

And just to add to the fun -- the power company folks always treat every line as if it were live until they've tested it. Even if the fuse or circuit breaker is blown. Why? Because of the possibility of a cross with a live line (mentioned above) but also because of the possibility of someone in the neighbourhood backfeeding with an improperly connected generator.

Be safe.

KC_Jones

I'll give you a good one on backfeeding, and this one resulted in the power company essentially buying some houses.

Before I worked for them, they had an incident with a tree trimmer. This wasn't someone working for a resident, this was a contractor hired to trim around the power lines. Well he made a mistake, it happens, but someone else also made a mistake on the substation controls.

Guy drops a large branch on the lines, 34kv (or 13 hard to remember) drops into the 110 bus for the neighborhood. Normally this would trip the entire 34kv feeder, but due to a mistake in the substation wiring there was no trip. So that 34kv energized the houses. To add insult to injury several people were home and happened to have video cameras (this was in the day of VHS).

I saw the video, and honestly I was in awe of what I saw. You could see arcing across aluminum siding, meters literally blew like projectiles off the house. All electrical equipment fried, you really had to see it to believe it. During the entire video you kept hearing the arcing and the blood curdling screams. Oh yeah the screams, the tree trimmer was in his bucket, unable to move crouched down screaming for help. I can't remember how long it actually lasted, but I recall roughly 10-15 minutes of video.

Someone at the control center finally noticed what was going on and manually shut it down, thankfully that worked. It was truly an epic event.

Solid_Fuel_Man

The substation really takes that blame. Trees fall, cross contamination happens, cans blow up. We just had a tree take out a pole at my neighbors house, transformer atop the pole spilled 15 gallons of oil on the road and made one heck of a mess at 1:30 am.