Discussion on discharge mechanism based on leakage current measurements of outdoor polymeric insulating materials in salt-fog test

We have developed a measuring system to separate leakage current of polymer material for outdoor insulator into three frequency components. We discuss the relation between discharge types and degradation on the surface of polymer materials for outdoor insulators. The special attention is paid to the discharge form in a salt fog test by considering each frequency component. Discharge image is analyzed by gaining the light emission intensity distribution using image-processing technology, allowing us to investigate the relationship between the three frequency components of the leakage current and discharge light emission.