Insight Into the Distribution of Pyrolysis Gaseous Products From the PE Outer Sheath of 110-kV High-Voltage Cable

Polyethylene (PE) is widely used in the preparation of high-voltage power cable sheathing due to its excellent electrical properties. Electrical fires occur frequently in recent years. This study evaluates the status of PE sheathing on high-voltage cables by analyzing the distribution of PE pyrolysis gas products and provides a theoretical and experimental basis for fire warning techniques. Using large-scale ReaxFF molecular dynamics (MDs) simulations, we study the gas production characteristics of PE pyrolysis. The simulation results indicate that the main pyrolysis products are H2, CO, CH4, C2H4, and C2H2, with an analysis of the pyrolysis kinetics and gas formation mechanism through MDs calculations. Through the aging experiment, it is found that with the increase of aging time, the contents of C2H4, C2H2, H2, and CO in the pyrolysis gas of the PE outer sheath show a significant downward trend. Furthermore, through pyrolysis experiments at different times, the impact of pyrolysis time on gas product distribution is analyzed using Fourier transform infrared spectroscopy and gas chromatography. Overall, with longer pyrolysis times, there is a greater variety and quantity of gas products. Only C2H4, C2H2, and CO2 are generated after 15 and 30 min of pyrolysis, with H2 produced after 180 min of heating. The simulated and experimental gas generation components are in good agreement. Last, the evaluation of the overheating state of high-voltage cable PE sheathing is based on the characteristic gas differences produced.