Potential Distribution Measurement of Electrical Surface Discharge by Using Electro-Optic Device and the Discharge Phenomena

带电表面放电沿固体绝缘子表面发展。应用普克尔斯晶体光学传感器测量了放电传播表面的电势分布。该测量系统由BGO普克尔斯晶体、Ar离子激光器、高速条纹摄像机和CCD摄像机组成。表面放电是在BGO晶体表面或绝缘板PMMA的表面上传播的。在其表面设置点电极，在空气中对电极施加脉冲电压。研究结果表明：1)对于BGO晶体表面的放电，其空间分辨率为0.1 mm，时间分辨率为2。对于PMMA板表面的放电，分辨率低于BGO上的放电，但适用于高压放电。2)从测量的电势分布可以计算出电场强度、表面电荷密度和传播速度。3)表面流光的电场在电极附近为几个千伏/厘米，而流光尖端的电场超过30千伏。4)负表面放电分步传播时，电势分布与步进同时快速充电。

Electical surface dischages are developed along surface of solid insulator. Optical sensor with a Pockels crystal has been applied to measurement of the potential destribution on the surface where the electrical discharge is propagated. The measuring system consist of a BGO Pockels crystal, a argon ion laser, a high speed streak camera and CCD camera. The surface discharge is propagated on surface of BGO crystal, or surface of insulating plate PMMA which is put on BGO crystal. Point electrode set up on their surface, and impulse voltage is applied the electrode in air. The change into position time of potential while the discharge is propagate can be measured continuously by using this system.Main results obtained from these studies are summarized as follows.1) For the discharge on surface of BGO crystal, the spatial and temporal resolution are 0.1mm and 2nd, respectivly. For discharge on surface of PMMA plate, the resolutions become lower than one for the discharge on BGO,but the method is applied to the high voltage discharges.2) Electrical field intensity, charge density on the surface and propagating velocity can be caluculated from the measured potential distribution.3) The electrical fields of surface streamer are several kV/cm near electrode but over 30kV at streamer tip. The propagating velocity of the stramer initially reaches 10^9cm/s after its start and decreases down to 10^6cm/s.4) When negative surface discharge propagates in step wise, the potential distribution charges repidly at the same time as the step.