Study on Partial Discharge Characteristics of Metallized Film Following Self-Healing in Power Capacitors

Metallized film capacitors (MFCs) is the essential components of the superconducting magnetic energy storage (SMES) system. In this paper, a polymer insulation film partial discharge(PD) experimental system is established to explore the PD characteristics of biaxially oriented polypropylene (BOPP) and metallized films based on the simulation of insulation defects formed after the self-healing in MFCs. As the size and quantity of defects increase, the distortion of the electric field intensifies, thereby facilitating the occurrence of PD. However, the PD amplitude of the metallized film decreased by about 10%. The PD of BOPP films is mainly internal discharge. The metallized film initially occurs surface discharge. With the applied voltage increasing, the intensity of internal discharge amplifies. Self-healing and PD will cause the loss of electrodes, leading to the degradation in capacitor performance. The difference in PD characteristics between BOPP and metallized films is attributed to the excellent conductivity of the metallized film surface. This property promotes diffusion and combination of the space charge, while reducing the accumulation of charges in the defects. Thus the electric field distortion is reduced, which makes PD more difficult to occur and less intensive.