气压和湿度对正直流电晕流注脉冲特性的影响

Influence of Air Pressure and Humidity on Positive DC Corona Streamer Pulse Characteristics

电晕是输电线路设计和运行中面临的重要问题之一。为此,测量了不同气压和湿度下的正直流电晕流注脉冲幅值和脉冲重复频率,实验结果与利用流体模型计算得到的波形随气压和湿度的变化规律一致。流注脉冲电流平均幅值Im随气压的降低和湿度的增大而减小。随着气压降低,流注头部电离减弱,使得注入流注通道的平均电子密度下降,流注通道内场强平均值E的降低是导致脉冲电流幅值下降的主要原因。随着湿度升高,流注头部电离减弱,使得注入流注通道的平均电子密度下降,流注通道内电导率λ的降低是导致脉冲电流幅值下降的主要原因。低湿度下,正直流流注电晕放电容易转化为辉光电晕,高湿度下,在较宽的电压范围内一直存在流注放电,流注脉冲平均频率随湿度升高显著增大。负离子解离产生自由电子的速率随湿度升高而减小,使得自由电子出现时,正离子已迁移到距离阳极较远的地方,是流注放电可以形成及流注脉冲重复频率随着湿度升高而增大的重要原因。

Corona is one of important problems in the design and operation of transmission lines. The positive DC corona streamer pulse amplitude and frequency under different pressure and humidity was measured, the results were in good agreement with the waveforms calculated by the fluid model. The streamer pulse average amplitude Im decreased with the fall of air pressure or the rise of humidity. The ionization intensity in the head of the channel weakened with the fall of air pressure, accordingly the number of electrons entering into the streamer channel decreased, and the weakening of average electric field E in the channel was the main reason of the fall of Im as air pressure was lower. The ionization intensity in the head of the channel also weakened with the rise of humidity, accordingly the number of electrons entering into the streamer channel decreased, and the decrease of conductivity λ in the channel was the main reason of the fall of Im as humidity was raised. The positive streamer discharge turned to be glow discharge at low humidity, while it existed in a wide range of voltage with a high repetitive frequency as humidity was raised. The free electrons production rate decreased with the rise of humidity; consequently, the positive ions had already migrated far from the anode as the free electrons emerged, and then the electric field near the anode returned to be sufficient to form a new streamer discharge with a high repetitive frequency.