Influence of air pressure on positive DC corona inception voltage of stranded conductors in the corona cage

The transmission lines pass by the high altitude region with low air pressure, which brings many special problems to the design and operation of the transmission lines. The corona cage is widely used to study the corona performance of conductors for its good economy and maneuverability. A computation model is adopted for evaluating the corona inception voltages of conductors in the corona cage, which is established according to the gas discharge theory. The charge simulation method is introduced to the computation model to calculate the electric field intensity. Then the positive corona inception voltage are calculated according to the positive corona criterion. The influence of air pressure on the corona inception voltage of conductors is analysed systematically. Corona inception voltage decreases as air pressure is lowered. The corona inception voltage may decrease by 9% per 0.01MPa bases on the standard atmospheric pressure, which is mainly due to the enlargement of ionization zone as a result of the increase of effective ionization coefficient.