This paper deals with the surface degradation characteristics of 20 kV silicone rubbers (SiR). A chamber containing nine ultra violet (UV) lamps with intensity of 50 W/m2 was considered as artificial ageing. There are many aging factors in the outdoor environment, but this paper study the factors UV that it cause Crazing, chalking, tracking and loosing hydrophobicity on the surface of insulator. Solid layer pollution method is applied according to IEC60507 standard and surface leakage current (LC) was measured to analyze its electrical characteristics. Fast Fourier Transformer (FFT) method is used to analyze the LC waveforms. Result show UV has direct impact on the hydrophobicity of insulator surface. Supporting the results from leakage currents analysis, scanning electron microscope (SEM) and thermo gravimetric analysis (TGA) were used to observe the surface changes of silicone rubber and the dielectric loss.
Key words: Degradation, silicone rubber, leakage current, hydrophobicity, ultraviolet.
Abbreviations: SiR, Silicone rubbers; UV, ultra violet; FFT, fast Fourier Transformer;NaCl, sodium chloride; CuSO4, copper(II) sulfate; THD, total harmonic distortion; TGA,thermo gravimetric analysis; SEM, scanning electron microscope; LC, leakage current.
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