HIGH-POTENTIAL TESTING OF MEDIUM-VOLTAGE CABLE.

After a number of medium-voltage cables had failed in the course of routine maintenance high-potential tests in some Owens-Corning Fiberglas Corp. plants, the corporate plant and electrical engineering departments undertook an evaluation of the advisability of such testing. This article discusses the study that was conducted and some conclusions drawn from it. The study was confined to the routine maintenance testing of cable that has been in service for some time; the fact that good practice demands an acceptance test of newly installed cable before it is placed in service was not in question. Among the subjects covered are the differences between acceptance testing and maintenance testing, essential criteria for obtaining valid test results, selecting test voltage, cable failure under test, testing radial and dual feeders, and others.