Evaluation of naturally aged non-ceramic insulators

Field aged non-ceramic insulators using weathersheds of silicone and ethylene propylene (EP) rubber, were evaluated for aging produced changes in material and electrical performance. The insulators had been in service for 13 years (EP) and 7 years (silicone rubber), respectively. The insulators were removed from a transmission line located in a relatively clean, subtropical environment. Electrical measurements performed included determination of the flashover voltage, evaluation of the contamination withstand capability and surface resistance, using the clean fog method. Material diagnostic tests were performed using a scanning electron microscope (SEM). Energy Dispersive X-ray analysis (EDX) and Cross Over Voltage (COV) measurements were carried out. The results demonstrate that both types of weathersheds experienced loss of material and electrical properties (contamination performance) when compared with new samples. Nevertheless, the functionality of both types of insulators was not impaired as their contamination withstand capability was considerably higher than the existing contamination level in the field, for the particular location from which the insulators were removed.