Effects of accelerated repetitive impulse voltage aging on performance of model stator insulation of wind turbine generator

A high reliability is essential for the insulation system of wind turbine generator because of its high repairing cost. In this paper, three experimental methods based on accelerated aging under repetitive impulse voltage and multi-environmental factors are established to (i) investigate the failure or degradation mechanism during the aging, and (ii) make recommendations on how to assess the functional life and reliability of insulation systems for wind turbine generator. Repetitive impulse voltage stress combined with thermal stress, change of temperature, steady damp heat and salt mist was, in turn, applied to model specimens with different length and section sizes. Some of non-destructive characteristic parameters such as dissipation factor, insulation resistance, and partial discharge inception voltage were measured periodically during the aging. In addition to the residual breakdown voltage, the appearance features and infrared spectrum analysis of specimens were carried out after aging. It has been found that the surface partial discharge generated under repetitive impulse voltage resulted in the degradation of surface insulating material near the slot end. The change of temperature also caused the delaminating of stator insulation from the core slot especially when massimpregnated insulation used in long slot of practical stator. The increase of dissipation factor of insulation system was largely contributed by salt mist and moisture factors especially when the surface or interface of insulation material was damaged. The electrically accelerated aging under about triple maximum repetitive impulse voltage for 1000 h was an effective and feasible method to assess the insulation system of wind turbine generator.