Partial discharge inception and breakdown characteristics of LN2/polypropylene laminated paper composite insulation system for HTS cables

A novel technique for partial discharge (PD) measurement and analysis (PD-CPWA : PD Current Pulse Waveform Analysis) is developed and introduced in this paper. The purpose of PD-CPWA is to elucidate PD mechanisms and physics in electrical insulating materials, focusing on the PD current pulse waveform and its time transition from PD inception to breakdown (BD). In this paper, PD-CPWA was applied to liquid nitrogen/polypropylene laminated paper composite insulation system for high temperature superconducting cables, and PD inception and propagation characteristics were obtained. Experimental results revealed that PD inception at the lower stress would mainly originated from micro gaps between PP laminated paper layers, and then PD activity could be developed also in butt gaps at the higher stress, and finally leading to BD.