Study on PD characteristics of insulation internal defects of large generator stator bar

Generally there are four types of defects inside the stator bar insulation of large generators, i.e. void, internal delamination, crack and delamination at conduct edge. It´s evident that these four types of internal defects appear at the different stages of aging and play significantly different roles in the aging and ultimate failure of stator bar insulation. Thus it makes sense to distinguish them. In this paper, partial discharge experiments were performed on four elaborate model defects to establish a firm basis for the recognition of defect type