Experience with accelerated aging tests on stator bars and coils

Three accelerated aging tests for evaluating different aspects of the design and manufacturing of stator winding insulation systems are described: the groundwall voltage endurance test for evaluating the ability of the groundwall insulation to resist aging due to operation at high voltage and temperature; the thermal cycling test for evaluating the ability of the insulation system to resist delamination caused by differential thermal expansion; and the turn insulation voltage endurance test for assessing the ability of a coil´s turn insulation to resist aging due to high voltage and temperature. The voltage endurance test for groundwall insulation has recently been standardized and has been shown to be a good indicator of problems associated with insulation system design and manufacture. Experience with the thermal cycling test indicates that the insulation delamination process can be rapidly accelerated. Preliminary results for the turn insulation aging test are given