How to locate faults in underground cables?

First you need to secify the faulted phase using DC Hipot or better using VLF tester.

Second , you use one of two techniques : Bridge technique or the best one TDR Time Domain Reflectrometry .

In the last technique a pulse with a predetermined duration and speed are sent through the cable , at the point of fault a change in impedance occurs and the pulse is reflected showing the distance on the screen.