Evaluation method of insulation system for wind turbine generator based on accelerated multi-factor ageing test

With the rapid increasing of the amount and capacity of wind power generation worldwide, the operation reliability of wind turbine generator (WTG) became more and more important due to its high repairing cost. In this paper, a procedure based on the accelerated multi-factor aging test was firstly established for evaluating the insulation system of offshore WTG. The specimens for modeling the stator insulation system of megawatt class WTG were prepared. The repetitive impulse voltage, temperature change, steady damp heat, salt mist and vibration, were applied, in turn, to the specimens for periodical ageing test, and at least 5 periods of ageing tests were conducted. At two intervals of each period, some non-destructive diagnoses have been carried out to monitor the change. The relationships of the dielectric properties of insulation system with the aged time have been obtained. The residual breakdown voltages of specimen were measured, and the micro-structures of insulating material were also analyzed. The testing results show that the environmental factors play an important role in the deterioration of insulation materials, and the cooperative effect would produce between the environmental factors. Finally two primordial evaluation methods of insulation system for WTG available for the offshore and onshore environments based on accelerated multi-factor ageing test are proposed.