Condition Assessment of Silicon Rubber Insulator used in Overhead Systems

Abstract

Polymeric insulators (silicon rubber) are widely preferred in overhead transmission networks due to their inherent properties. The inclined plane test as per IEC 60587 is useful studying the tracking and erosion performance of the silicon rubber insulators. The virgin and artificially-aged silicon rubber samples were tested as per the standard by supplying 3.5 kV AC and DC (both the polarities). Fourier Transform Infrared Spectroscopy (FTIR) on tested samples reveal the effects of artificial thermal aging on the material. The observations show that the aged samples exhibit poor performance with DC voltage, especially with positive polarity. More intensive arcing is found with DC as compared with AC voltage. Also, surface degradation is more severe with positive DC. The FTIR spectra provide the details of stretching of various bonds like O-H, C-H, Si-O-Si which may be resulted in hydroxylation and de-polymerization of the material. The stretching of other bonds is also affected more in aged samples than virgin.