低气压下直流正极性冰电极电晕特性研究

覆冰将改变绝缘介质的放电过程，导致电力系统绝缘性能下降，为深入研究覆冰绝缘子串中空气间隙的电晕放电特性，基于冰棱-冰板电极系统，通过脉冲电流传感器和紫外线成像仪CoroCAM IV+揭示了气压对起晕电压、放电模式、放电波形及其幅值等的影响。通过数学分析提出表征不同大气压下不同间隙长度时起晕电压的修正公式，分析和讨论气压对放电脉冲及其幅值的影响。理论分析表明，随着气压的降低，覆冰空气间隙起晕电压呈幂函数或指数函数降低，特征指数同间隙长度相关。试验结果与理论分析一致，进一步揭示了覆冰环境下电晕放电的特性。

The Properties of Positive DC Corona Discharge in Iced Electrode System Under Low Atmospheric Pressure

Low air pressure and recurrent icing may affect the discharge characteristics of dielectrics and decrease the insulating performance of insulators. The aim of this paper is to investigate the corona discharge phenomena on ice-covered insulators at low air pressure based on an icicle/iced-plate electrode system with direct current (DC) positive voltage. Using a pulse current sensor and an ultraviolet camera, CoroCAM IV , it was possible to carry out investigations on the influence of atmospheric pressure on corona onset voltage, discharge mode, discharge waveform and mean discharge amplitude. An empirical function for predicting corona onset voltage was developed, shedding more light on the influence of pressure on mean pulse amplitude of partial discharge (PD). The theoretical analysis indicates that the corona onset voltage of the tested clearance decreases exponentially with the increase of altitude, and that the special exponents are affected by the length of clearance. The results of this study will advance our knowledge of corona discharges at icicle tips and help to calculate more precisely the electric field distribution along ice-covered insulators.