Comparison of PD and DF test results before and after voltage endurance tests

The voltage endurance test on coils/bars is an accelerating aging test of the insulation system. The voltage endurance test can be used to assess the insulation quality of coil manufacturing. Partial discharge (PD) and dissipation factor (DF) tests are also diagnostic tools to discover insulation problems in coils/bars. Based on a large testing database, this paper presents the test data on a number of coils/bars to observe the general insulation performance of new coils/bars before and after voltage endurance tests. A comparison of PD and DF test results before and after voltage endurance tests can evaluate the effect of the aging tests on the insulation system. The paper would be helpful for both coil manufacturers and machine users to understand the insulation performance of machine coils/bars before and after voltage endurance tests.