Qualification test results on stator bars of large hydro generators

Thermal cycling and voltage endurance test (VET) are the most common tests used to qualify insulation systems of bars or coils of large rotating machines. This paper reports the results of these tests on 13.8 and 16 kV hydro generator bars. Partial discharge (PD), dissipation factor (DF) and tip-up tests are used as quantitative tests to assess the changes in condition of the insulation due to accelerated thermal and electrical aging. Breakdown tests were also performed to evaluate the effect of different stages of aging on dielectric strength of the bars.