DEVELOPMENT OF NEW DEGRADATION DIAGNOSIS METHOD OF OUTDOOR INSULATION USING AC DISSIPATION CURRENT WAVEFORM MEASUREMENT

研究了基于交流耗散电流波形测量的室外绝缘退化诊断新方法。基于DSP的新型测量系统可以对片状样品的介电性能进行评估。电介质特性的电场依赖性可以与电场作用同时进行评估。系统的传递函数也由DSP系统自动求值。通过DSP系统控制外加电压波形，实现对外加电压波形的控制。当出现异常响应时，现场应用下一个周期内的电压。该系统可以检测时变特性，如硅橡胶片在润湿或干燥过程中的表面导电性。吸水降低了硅橡胶的疏水性。接触角的恢复有两个阶段。最初，它恢复得很快，这与吸收的水分蒸发有关。在这种快速恢复之后，它缓慢地增加，似乎与LMW或硅酮表面相对应。电场的U-M（本体方向，主电极高压方向）和G-M（表面方向，主电极保护方向）都可以检测硅橡胶片在老化和恢复过程中介电性能的变化。与RTV相比，HTV对衰老和恢复的研究条件更为敏感。HTV硅橡胶的介电常数在吸水老化过程中增大，在空气中吸收水分蒸发恢复过程中减小。在第一次时效过程中，tanddelta表现为简单的增加，但在时效过程中，tanddelta表现为界面极化，在HTV硅橡胶的体积中减少一定的LMW后，tanddelta表现为界面极化。

Development of new degradation diagnosis method of outdoor insulation using AC dissipation current waveform measurement has been studied. The new measurement system with DSP can evaluate dielectric property of a sheet type sample. The electric field dependence of dielectric property can be evaluated simultaneously with electric field application. The transfer function of the system is also evaluated automatically by the DSP system. By using DSP system, applied voltage waveform is controlled and the system can cu off the applied high. voltage within next one cycle of field application in case of abnorma response. This system can detect time varying property such as surface conductivity during wetting or drying of silicone rubber sheets.Water absorption reduces the hydrophobicity of silicone rubber. The recovery of the contact angle has two stages. Initially it recovers quickly that is related to the evaporation of absorbed water. After this quick recovery it increases slowly that seems to correspond to the LMW or the silicone surface.Both U-M (Bulk direction ; High voltage to Main electrodes) and G-M (Surface direction : Guard to Main electrodes) application of electric field can detect the changes in dielectric property during aging and recovery of the silicone rubber sheets. HTV is more sensitive compared to RTV for studied conditions of aging and recovery.Dielectric constant of HTV silicone rubber increases during aging by water absorption and decreases during recovery in air by the evaporation of absorbed water. Tandelta shows simple increase during 1st aging, however, it shows like an interfacial polarization during aging and recovery after certain amount of LMW has reduced from the bulk of HTV silicone rubber.