scope:

The introduction of cables with extruded dielectric insulation and of modern splicing technology has imposed new conditions and restrictions on cable fault locating. The use of excessive high voltages and energies during ac, dc, and surge testing of service-aged power cable systems with extruded dielectric insulation may overstress insulation, creating defects that become faults after the cables are returned to service.

This guide is intended to be applied to medium-voltage distribution cables. Medium-voltage distribution systems generally operate at system voltages above 1 kV and up to 34.5 kV nominal.

The end user of the cable circuit should evaluate the necessity for verifying the integrity of extruded dielectric insulated cables, and, if they are in critical service, proceed to perform the high-voltage/energies testing. If not detected during dielectric tests, defects in dielectric materials may result in cable failures during the transient voltage surge episodes while in service.

Purpose

This guide is intended to provide trouble-shooting and testing personnel with information to quickly identify a faulted cable section and/or locate a cable fault with minimum risk of further damaging serviceable cables, terminations, and equipment.