Field Testing of Cables: Theory and Practice

Testing cables in the field requires a specialized knowledge of dielectric behavior, electrical stress phenomena, safe and proper use of test equipment, and interpretation of test results. Theoretical and practical aspects of high-potential field testing of medium- and high-voltage extruded cables are discussed. The fundamental theory of ac and dc voltage stresses is reviewed along with the behavior of the cable insulation under dc stress. It is concluded that a dc test is preferred over an ac test for field applications. However, for a dc test the cable should be cooled to ambient temperature so that the voltage stress distribution is the same as for an ac voltage. A program for field testing is suggested along with the voltage levels to use for the test. Finally, guidance on performing the test in the field is given along with examples on interpreting the test results.