Forecasting the Partial Discharge Inception Voltage (PDIV) of Insulated Busbars for Future Aircraft Power Distribution Systems

Electrification of aircraft propulsion requires the development of busbars and cables that can deliver higher power levels of up to 4 MV A for hybrid electric and 40 MV A for an all-electric aircraft while still operating in a safe and reliable way. Voltage levels on aircraft are presently relatively low compared to most ground-based applications (+1 −270 DC bus on the Boeing 787 Dreamliner) but with future levels expected to rise further, the risk of partial discharge is increased. Sharp corners on insulated busbars can enhance the electric field strength providing a potential location for partial discharge initiation. In this paper, we present the results of finite element analysis of electric fields in the air around a bus bar and use the streamer inception criteria to estimate the PDIV for a range of insulation thicknesses and radii of curvature on the busbar edge. The use of screens to retain the electric field within the insulation to prevent partial discharge in the air surrounding the interconnect has the potential to reduce the insulation thickness required and lead to weight savings. The use of screens does not eliminate the risk of partial discharge in air-filled voids within the insulation, so we also calculate the maximum void size that can be tolerated for screened bus bars. As aircraft operate at high altitude where the PDIV of air is lower, a pressure equivalent to 50000 ft (15240 m) is used in the calculations.