Impedances and surface conditions of naturally coastal-polluted epoxy resin insulators

This paper presents the experimental results of one new-clean and six different coastal area naturally polluted outdoor epoxy resin insulators. The conducted experiments were leakage current and applied high voltage measurements, in the hermetically sealed chamber on various RH. Both quantities were measured by a storage digital oscilloscope. The data could be recorded and transferred to a computer, saved in softcopy form. In this paper, it is revealed two values of humidity, low and high. Furthermore, from each measurement, it was obtained impedance, phase angle and THD, and impedance ratio between low and high RH. The results indicated that on the new-clean, on low and high RH, the insulator was no change. Whereas on first withdrawal, the insulator impedance was significantly different on high and low RH, as ratio 65.45%. This case was caused by pollutant adhered on the insulator surface, due to dry season. Finally, on the sixth withdrawal, the ratio of impedance on high and low RH reached 67.97%, the phase angle and THD changed from 77o to 51.43o and from 18.7% to 8.8% respectively for low and high RH. It is supposed, besides pollutant, it was caused by the degradation on the surface, that indicated by SEM test results on the epoxy resin specimens. The degradations of epoxy resin surface were also shown in this paper gradually using SEM.