Partial Discharge and Its Influence in Oil-Paper Insulated Needle Plate Systems under Combined AC-DC Voltage

As an important part of the ultra-high voltage direct current (UHVDC) transmission system, the safety of the oil-paper insulation at the rectifying valve side of the converter transformer is extremely important. This kind of insulation is mainly dealing with combined AC-DC voltages, therefore, further studies about the partial discharge (PD) and its influence on the rectifying valve side need to be carried out. In this study, experimental platform including a high-speed camera was used to obtain photos of the experimental phenomenon, herein the PD process and its influence can be observed and analyzed. Experimental results show that the aging of oil-paper insulation system is closely relevant to the PD phenomenon. This study reveals the relationship between the PD process and the electrical aging, which can help to protect the oil-paper insulation system at the rectifying valve side of the converter transformer.