The defects of cable accessories will seriously affect the safety of the grid

and the characteristics of par-tial discharge in voltage withstand test and operation process have important research value. This paper focused onknife incision defects divided into 2

3

4 mm annular knife incision defects and 3 mm vertical knife incision defect. Longtime monitoring partial discharge of defects is used. Statistics on the partial discharge characteristics of defects at dif-ferent time are counted. Trend diagrams and spectrum diagrams are drawn

and the differences are interpreted physi-cally. Test results show that partial discharge of knife incision defects starts with the surface discharge and turns intoelectrical tree discharge and breaks down. Knife incision defects with different depth and location will show similarelectrical tree discharge before breakdown. The deeper incision is the more surface discharge effects on defects. Ver-tical knife incision defect is more likely to evolve into electrical tree discharge and breaks down in a short time.