Optical and Electrical Partial Discharge Measurement with A1N Dielectric Barrier in Mineral Oil

SiC based wide bandgap power modules are well known for their performance in high voltage, high frequency and high temperature conditions. The use of high voltage in small gaps increases significantly the risk of partial discharge (PD) activity, which can lead eventually to a breakdown and cause an irreparable failure of the module. Thus, new insulating materials and packaging structures are required in order to prevent PDs. This work aims to analyze the PD activity in different configurations with dielectric liquid encapsulation under AC 50 Hz voltage waveform. The use of liquid dielectrics can be an advantageous alternative to the conventional silicone gel thanks to his self-healing properties. In this study, both electrical and optical measurements of PD are carried out. Analysis and discussions of PD patterns, partial discharge inception voltage (PDIV) and the number of PDs (NPD) obtained using both techniques are presented. The results show that the photomultiplier tube (PMT) can provide PD patterns, PDIV and optical NPD values (in arbitrary unit) close to that obtained using standard electrical technique. The PD patterns show a discharge activity in both alternations even at low applied voltage values during the period. This behavior confirms that the electric field is highly affected by the space charge in the liquid.