The purpose of this paper is to review work undertaken on partial discharges and their influence on the insulation of wind turbines. No matter whether partial discharges can be considered as the main cause of deterioration of the insulation material

the initial cause of failure or not but an indication of the material degradation

there is no doubt that they are intimately linked to the aging of machine insulation. Material degradation can be detected by non-destructive techniques (e.g.

partial discharge measurements

change of tan

δ

) or by destructive techniques

such as by cutting small pieces of the insulating material and by putting them under the scrutiny of the scanning electron microscope (SEM). Wind generators are a modern subject of research

especially in view of the growing demands of electric energy worldwide and the problems facing the environment all over the globe. Wind turbines are a novel field of research regarding partial discharge diagnostics since they are subjected to a variety of aging factors

which are different from conventional turbines. In this respect

particular attention should be paid to the multi-factor stressing of insulation and their consequences on the partial discharges.