Fundamental investigation results of diagnostic techniques for deteriorated polymer insulators

Polymer insulators have superior performance, such as light weight, high mechanical strength, high contamination flashover voltage, etc. compared with conventional ceramic insulators. Polymer insulators, however, are made of organic materials and so ageing deterioration cannot be avoided. Serious ageing deterioration, such as puncture, brittle fracture, tracking, erosion has been observed in fields. Diagnostic techniques to detect deteriorated polymer insulators before serious accidents are essential for wide application of these insulators in future. We have investigated to find out possible techniques to detect such insulators by using polymer insulators removed from actual lines used for about 10 years in Shanghai area. Possibility to detect punctured insulators by image intensifier under normal operating voltage was confirmed.