Identify this utility wire

Factual Questions
1

I posted in the MMP thread that the power went out this morning. Short version: A wire fell down from the power pole.

There is a pole in front of the house, and another one at a T-intersection three houses down. The wire was connected to the very top of that pole, and had become disconnected from ‘our’ pole. The wire is jade green in colour, and I didn’t take the time to see if the green was insulation or oxidisation of bare copper wire. The end that was disconnected had a tip that was maybe 3/4 inch of copper that appeared to have been singed a little. I presume this end attached to something at the top of the pole. The wire was about a quarter inch in diameter.

So:

  • Green, possibly uninsulated, wire about 0.25 inches in diameter;
  • Located at the very top of the power poles;
  • Did not electrocute me when I ran over it and the bare end scraped along the bottom of my car.

What is this wire? Some sort of ground? Since it’s at the top of the pole, is it some sort of lightning protection? If it’s not a ground, is it part of a circuit? If not, then why did the power go out in the neighbourhood?

2

The very top wire is usually a ground wire. IIRC, they put it at the top to help catch and divert lightening. I suppose someone working on the power lines is also less likely to accidentally ground themselves with it up that high.
ETA, just checking online, the few places I looked confirmed that it’s for dealing with lightening, but it’s called a ‘static wire’ not a ground. And I guess that makes sense. You really don’t need a dedicated ground wire since the ground is, well, everywhere.

ETA2: It was likely green from oxidation and if it the end of it was actually burned, it may have hit another wire on the way down or another live wire hit it and the resulting short/spark is what caused it to break.

3

[nitpick] lightning [/nitpick]

4

Thanks.

So is a static wire part of a circuit? What would cause the power to go out? Unless, as you suggest, it hit another wire on the way down and blew the fuse?

5

No, it wouldn’t be part of the circuit. But if it hit another live wire on the way down, that would have shorted it [the live wire] to ground and opened a breaker somewhere upstream.

6

Aha. Much like the squirrels used to do on the other pole, before they put a higher-capacity breaker up there.

7

Sounds more like a single-phase primary distribution wire, oxidized copper. Static wires for lightning are usually only found on sub-transmission and higher lines (69 kV and up). Static wires also generally aren’t attached to the pole with insulators. If there’s an insulator at the top of the pole then it was a live wire. If it was burnt then it likely arced after falling but the short circuit tripped a breaker.

Unlike inside buildings, in the transmission and distribution network, neutral and ground are almost interchangeable. The static wire (if present) and any neutrals in the primary or secondary distribution wiring will be connected to each other and grounded at (usually) every pole with a wire going down the side into an anchor rod in the dirt.

This is a good old-school explanation of a lot of what you see out in the world: UTILITY POLES

8

If that wire shorted against another one, you would probably know it - it would have made a tremendous bang. Did you hear anything when the lights went out?

9

I heard a thump, like something fell on the roof. [NB: Nothing fell on the roof.]

10

As mentioned above, the top wire in residential systems is most always the hot wire. In my area its energized to 7K . The next lower wire is the neutral and is usually tied to ground, the real ground, at each pole.

11

A static wire is a static ground. As different from an Electrical ground.

Static grounds and Electrical grounds are connected together, and are both grounds, but they serve different purposes, carry different currents, and are only connected together deliberately, at some ‘correct’ point, not willy-nilly where it feels good

… It’s a separate subject, but ground isn’t everywhere, and even if it was, you still would need ground wires . Both for good reason, and because (at least in Euro/Aus standards) the good reasons are expressed in electrical standards of mind-bending complexity.

12

If you heard a thump and the power went out immediately, it was most likely a distribution line.

Power lines have what are called automatic reclosers on them. For those that don’t know what a recloser is, it’s kinda like a circuit breaker in your house except that it will automatically turn itself back on after it trips.

If you short something out in your home, the circuit breaker trips, and you have to walk down to your electrical panel and reset it. Power lines have the same sort of thing, except that power lines will often have temporary faults caused by things like tree branches blowing into power lines or high winds causing power lines to blow into each other. And unlike in your home, the “circuit breaker” for the power line isn’t within quick walking distance. It is likely several miles away. So to handle quick faults like tree limbs and winds and such, the recloser waits a second or two and then flips the circuit back on. If that fails it will probably do it again a couple of times. If those fail, it will wait maybe a minute or so and will make one last attempt at flipping the circuit back on. If that also fails, it gives up, and a lineman is going to have to fix whatever the problem is.

If you have ever had your power blink off for a second or two, it was probably a recloser that automatically turned the power back on. If you have ever had your power go out, but the lights blink a couple of times and then stay dark, that’s also a recloser trying to do its thing, except in this case the fault wouldn’t clear.

Reclosers are programmable, so the power company can set them up any way they would like, but typically they make a few quick attempts within a few seconds, then one or two attempts after a longer period of time (a couple of minutes), and then they give up.

If a static line breaks and shorts out one of the power lines, that can cause the line to trip, but a recloser will usually turn it back on. As long as the static line falls down and doesn’t get stuck hanging on one of the power lines, all you end up with is a short blink of a power outage.

Distribution lines are usually not insulated.

IMPORTANT SAFETY NOTE:

Never touch downed wires. You never know if it’s a power wire, and while it might be dead at the moment, a recloser could turn it back on and kill you the moment that you happen to touch it.

13

Thanks for the information, engineer_comp_geek. There’s a fuze/breaker at the top of one of the poles in front of our house. That’s the one the squirrels would kill themselves on until PSE cut the top of the tree and put on a higher-capacity breaker. I didn’t know about the auto-reset. Nice feature.

Since the wire was matte jade-green, I didn’t see it against the light grey road. I’m guessing it wasn’t energised, as it didn’t affect the car other than sraping along the underside. (Of course the tires provide insulation.) When I got out of the car to investigate, I made sure I didn’t touch anything – just in case.

14

That is most likely just a fuse / disconnect.

If it looks something like this, it’s just a fuse:

Reclosers vary. Here are a couple of examples:

Yeah, squirrels definitely wreak all kinds of havoc on power systems. A suicidal squirrel managed to take out a major distribution transformer near here a few years ago, leaving about 10,000 people in the dark.

15

That’s it.