Power-factor testing for finding insulation values

THE DIELECTRIC-LOSS and power-factor method of testing insulation has been in use by many operating companies for almost 20 years for determining when new equipment meets minimum requirements for insulation and to keep equipment in use in good operating condition through adequate maintenance. The equipment for making dielectric-loss and power-factor tests consists of means for supplying a-c potential to insulation and meters, from the readings of which the power factor of the current through the insulation may be determined. This test will detect moisture, dirt, carbon deposits, carbonization of wood and other organic material, corrosion of bushing leads due to corona, and almost all insulation defects. The test is not a destructive test since voltages below operating voltage generally are used. The test sets are sufficiently rugged for field use and can be transported easily. Highly technical personnel are not required to make tests and analyze the results, but test engineers must have common sense, intelligence, and thorough knowledge of the apparatus being tested.