棒-板间隙在交直流预电压作用下的冲击特性

为了分析实际运行中稳态预电压对电力设备绝缘的影响 ,研究了在标准气象条件下 ,棒 -板间隙的操作冲击特性和交直流预电压的关系。研究结果表明 :正直流预电晕能提高气体间隙中正的操作放电电压 ,而负直流预电晕却能降低间隙的正操作冲击放电电压 ,且电极的棒直径越小这种效应越明显。正直流预电晕能减弱正操作冲击下的电晕特性 ,阻碍了正流注和先导的形成与发展 ,而负直流预电晕却能激励正流注放电 ,从而造成强烈的先导放电。在交流预电压作用下 ,间隙的正操作放电电压比无预电压作用下的纯操作放电电压低

Sparkover of rod-plane gap for composite alternating or direct/impulse voltages

Air breakdown for composite alternating and direct voltages in a rod plane gap at standard atmospheric conditions were studied to understand insulation breakdown in electrical appliances. The test results show that a positive pre stressed DC corona can increase the positive sparkover voltage of the switching impulse and a negative pre stressed DC corona can reduce the positive sparkover voltage of the switching impulse. Smaller rod diameters caused more significant effects since for the same DC voltage, the DC corona pulse current increase with decreasing rod diameter. Photographs show that the positive DC corona reduces the corona activity of the positive streamer and leader formation during a switching impulse, but the negative DC corona has the opposite effect for the pre stressed AC case. The sparkover voltage of the positive impulse without AC pre stressing voltage is always higher than that with AC pre stressing voltage, so the problem is more serious than with DC pre stressing voltage.