A common cause of cable faults is damage to the plastic casing (referred to as the cable sheath). Such damage permits water ingress to the cable, creating “Water Trees” and other corrosion based damage within the cable. Water trees are one of the primary reasons for cable faults, and the ability to identify these faults is a vital step in the cable fault testing process.
Locating cable sheath faults is one of the last steps in cable testing, occurring after you have identified the existence of a cable fault via the identification procedure based on your specific site variables and the type of system you are working on.
Following cable fault identification, a pre-location procedure estimates the location of the fault. Cable sheath fault location is the final stage in this process, pinpointing the flaw on site. Faults can be identified by ground fault locators, which pass a test current along the cable and measuring the voltage gradient at the point it exits to ground.
There are inherent dangers to a cable sheath fault, which are elevated in a high voltage scenario. If the current leaks to ground it is possible to complete a circuit with a secondary cable nearby causing collateral damage.