Dielectric tests have been used for decades to diagnose power transformers and bushings. In addition to the traditional tests at line frequency, modern types of dielectric tests using different frequencies and voltages have evolved.
This article explains the importance that dielectric properties have on insulation systems as well as factors that influence these properties. It also compares the most common test procedures and describes what kind of information you can gain from the measured values. By choosing the correct tests, you can detect issues in power transformers and bushings and decide on the proper type of maintenance before failures occur.