Diagnosis and Research on Partial Discharge Characteristics of EMU Capacitors with Typical Defects

The traction converter supporting capacitor of the EMU provides good support for the operation of the EMU, but due to factors such as the environment and manufacturing process, defects are formed inside the capacitor, which can easily cause partial discharge and threaten the safe operation of the EMU. This paper conducts partial discharge tests between the electrode and the shell on three types of defects including metal particles, insulating oil and water bubbles, which are common in capacitors. After data analysis, the results show that metal particles have the strongest discharge intensity, the largest discharge energy, and insulation oil inflow is next, and bubble defects are the weakest. The maximum similarity of the positive and negative skewness of the PRPD spectrum is calculated to provide a basis for distinguishing the three types of defects.