Let’s say a power line gets knocked down in a storm or something. How does the lineman know the exact place to reattach the line for repair?
I feel like part of the question is missing, or I’m missing it.
They splice the broken wires back together.
Are you asking how they find the break? In that case, the rely on sensors located around the system as well as people calling in to report power outages to narrow it down the area and then they go out there and physically look for it.
Check out this guy’s videos:
He’s a lineman in Canada and his videos are almost always on-the-job, as he is fixing the kind of problem you describe. As he works he answers exactly those kinds of questions.
Bobsdecline (Aaron, I think) is the lineman I watch on youtube. In fact, I was waiting for the OP to clarify the question so I could find the right Bobsdecline video to post. There’s one out there, filmed in the middle of the night, possibly raining or snowing, showing him, having isolated the problem as much as he can, literally driving/walking the line with a flashlight until he finds the broken wire.
I think that it’s actually possible to detect the location of breaks remotely, from signal “echoes” from the broken spot. Though I don’t know how precise this is; the walking-along-with-a-flashlight step is probably still needed at the end.
Surely they have cool tools for that. I have cool tools that can measure lengths of CAT-6 cable in the walls by doing exactly what you described.
I bet the lineman’s version costs 10 times as much though.
I was waiting for an answer from Wichita.
I think he’s away. He needed a small vacation.
mmm
In principle a time domain reflectometer (TDR) sounds the obvious tool. (There are equivalent mechanisms such as frequency domain reflectometers (ie use a Fourier transform and you get the dual) and even hybrids.)
Basically fire a signal down the wire and look for a reflection off the unterminated end. However a bit of an online search didn’t turn up much, except for research into the idea.
The main problem being that a general power distribution line isn’t a simple nice transmission line. There may be a break somewhere, but there are probably many spurs coming off the line, and even if there is a break in one direction, behind you is going to affect the signal as well. There isn’t a well defined impedance nor velocity factor either. A big very high voltage interconnector would be expected to behave nicely, but local distribution networks, much less so.
Using a TDR on an Ethernet or coax run is easy. You have a simple direct run and you can read the reflections off and see every little impedance wiggle and map time to distance. A power transmission line is likely a real trial to untangle. Doable maybe, within limits. It would likely help a great deal if you knew what it looked like to the test gear before any failure. Chances of that sort of data being current are going to be very slim sadly.
OTOH, there is a lot of data run atop the power distribution nowadays. There is probably a lot of information to be gleaned from this general chatter, and if monitored and analysed it might be possible to create a quite detailed understanding of the transmission characteristics of each bit of distribution network. The whole data transmission network might be made to do double duty monitoring the wires themselves.
One of the tools they have is called a “thumper”. It’s for finding breaks in underground power cables.
The thumper literally works by sending a high voltage pulse down the wire. The electricity will arc across the break or will arc into the ground, causing a “thump” that can be heard on the surface. It also makes all of the worms in the area come to the surface (they don’t like being shocked). So the linemen will simply listen for the thump and will look for worms.
Not as fancy and high tech as some folks imagine, but it works.
The fact that the thumper summons the worms saves the linemen from having to walk without rhythm.