High Temperature Insulation Materials for DC Cable Insulation-Part II: Partial Discharge Behavior at Elevated Altitudes

Utilizing hybrid electric propulsion systems in the next generation of aircrafts with elevated DC voltage level has raised the concern about the degradation of insulation subjected to partial discharge at high altitude and harsh environment. In this work, the surface discharge behavior of commonly used high-temperature insulation materials in aviation systems (FEP, ETFE, and PEEK) under positive and negative DC and ramp voltage was studied, including the pulse waveform, frequency spectrum, PD count and magnitude. Pressure changes as a significant factor influencing surface discharge phenomenon was thoroughly studied. Dust figure technique was employed after voltage ramping tests for both positive and negative polarities at low pressure to investigate the surface charge accumulation and surface discharge traces, and unveil the involved physical mechanisms at different stages of streamer propagation. The content of this paper provides a reference for surface discharge studies and evaluation of high temperature materials for medium voltage direct current power distribution in the future aviation systems.