how do they find out where an underground electrical cable that are encased in concrete pipes has developed a fault or gotten cut and needs fixing?
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You realise there’s a fault when electricity doesn’t come out the other end like it should do.
You can find the fault through a few ways. Walking the line might reveal a very obvious point, like someone has dug up the ground or something.
You can put a signal down the cable, watch for its reflection (it bounces off where the cable fault is) and, since you know the speed of the signal and the properties of the cable, you can make a good guess for the location of the fault. You then go out to the approximate area and look.
You can dig near the approximate area and see if there’s anything obvious underground. Damaged cables have a specific type of burn smell that can be detected.
You can put a signal down the cable and use detection equipment to follow it. When the signal stops you’ve found the break.
Sometimes it’s just a known cable with a dodgy connection buried, and you happen to know that connection failed every few years so you go dig it up again on a hunch.
There are two common faults, open circuit (a break) and short circuit (the cable ends touch each other). Different techniques can be used for each.
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