There are various methods employed in finding a
buried joint .................. it all depends on what you are presented with as an engineer as to which method you would use ??
If there are 'spare pairs' within the cable that are not used, the chances are they
may be 'stumped' (disconnected) in the buried joint. So, we would measure these 'spares' and whilst tracking the cable using a 'Cat & Genny' (Google it
), we also use a pedometer to wheel out the distance of the measured spare pairs.
The problem is, there could be a coil of cable left in the ground as sometimes happens that would throw ones measurement out quite a lot, so the key is to also listen to the CAT tools 'beep-beep' and start tweaking down the 'sweep' level. Where the spare pairs end, the 'beep-beep' will all but disappear. It needs a little bit of experience to get to grips with it.
Likewise, if there are no spare pair in the cable, ie: they are all used and jointed through, then we attach the Genny to the armoured wiring protecting the inner cable, this is a bit trickier to get to grips with as the induced signal from the Genny has a high chance of spreading to 'Earth' where the insulation has cracked over years of being underground. But, a good engineer will know a 'good signal' from a 'poor signal' and will follow the trace until the 'beep-beep' diminishes, which is where the armoured cable has been cut to fit the buried joint.
Many, many years ago, we were told to fit a metal plate to the joints so that we could use a metal detector to locate it again in the future, but that practice kinda dropped off over the following years.
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Believe me when I say that when you are presented with mile after mile of rural buried cable, you become quite proficient in measuring, locating and digging down on buried joints.