交流电压下变压器油中流注发展时空演化的光-电信号特征研究

Optical and Electrical Characteristics on Space-Time Evolution of Streamer Propagation in Transformer Oil under AC Voltage

流注放电多具有电离程度高、发展速度快及树状分叉等典型特征,是介质击穿前发生的各类放电起始、发展现象的统称。研究变压器油中流注现象对于加深液体介质放电机理的认识以及提升油纸绝缘性能具有重要意义。本文通过搭建流注光-电特性检测平台,获取了交流电压下针板电极结构中流注放电的光-电脉冲电流序列和光学图像。结果表明,负流注主要包括单个脉冲、幅值递增序列、幅值递减序列及幅值先增后减序列四种典型序列模式。负流注通道形状为球状,但较难向前发展,导致击穿电压较高;正流注电流脉冲序列为正脉冲簇形式,通道形状为细丝状且发展过程中伴随着随机分叉现象。结合流注发展电流序列和空间发展图像,对正、负流注起始与时空演化机理进行阐述,根据电容模型和流注通道压力平衡方程计算了正、负流注发展时的半径、速度特征参量,得到负流注通道半径约为80?m,正流注直径为60～80?m,平均速度约为3km/s,计算结果与实验现象相符。

The streamer discharge is the pre-breakdown phenomenon including inception and propagation process of discharge,which is featured by high degree of ionization,high propagation velocity and random branching characteristics.Studying streamer discharge in transformer oil is of great importance to deep understand the mechanism of liquid dielectrics discharge and improve the quality of oil-paper insulation.The steamer propagation process experimental platform is set up to obtain the current pulses and optical image of streamer.It is found that current pulses of negative streamers include four patterns,i.e.single pulse,increasing pulses,decreasing pulses,and first increasing then decreasing pulses.The negative streamer is in a nearly spherical shape and develops slowly with the rise of applied voltage.The positive streamer current pulses are in the form of pulses burst,where the streamers are in a filament-like shape with a random branching characteristic.The inception and propagation mechanism of streamer is also discussed,and several parameters of streamer including radius and velocity are calculated.The results show that the radius of negative is about 80μm,and the diameter of positive streamer is 60~80μm with 3km/s of the average velocity,which are in accordance with the experimental results.It is concluded that the inception and development mechanisms of positive and negative streamers are different.