Electric Pyrolysis of Silicon Rubber- an Explosion Failure Case of 220 kV Power Cable Joint

In this paper, an explosion failure case of 220 kV power cable joint is analyzed. The disassemble analysis reveals that prolonged overheating of the cable joint is responsible for the decline in the mechanical property of the silicon rubber (SiR) insulation, further resulting in SiR insulation electrical breakdown. Based on this case, SiR insulation discharge-breakdown experiment and gas chromatography measurement are conducted to explore the electric pyrolysis evolution of SiR insulation. The results show that the electrical breakdown process of SiR insulation is moderate due to its high elasticity and the insulting property of SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> formed by electric pyrolysis. Meanwhile, the breakdown cavity is gradually expanded by the pressure caused by the generated H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and hydrocarbon gases. Theoretical calculations indicate that the pressure generated at the instant of final arc-induced breakdown in the cable joint exceeds 800 GPa. Furthermore, these pyrolytic gases serve as combustible material for the subsequent explosion. This study provides both theoretical insights and experimental evidence to support fault diagnosis and prevention strategies for cable joints.