Degradation Dynamics of Polymeric Housing Materials Used for HV Line and Station Apparatus

A combination of laser irradiation and thermogravimetric analysis has been utilized to understand the degradation dynamics of polymeric materials used for housings of outdoor high voltage (HV) line and apparatus insulators, namely, silicone rubber, ethylene propylene diene monomer rubber and cycloaliphatic epoxy. The induced temperature rise was calculated using laser photo-thermal models and the results were found to be in good agreement with experimental findings. It has been shown that there are significant differences in the degradation dynamics of silicone rubber when compared with ethylene propylene diene monomer and epoxy. It has also been shown that the laser irradiation technique can be used as an efficient method to rank polymers materials for arc tracking and erosion resistance, especially for present day materials that will easily pass the screening tests prescribed in the ASTM and IEC standards.     

Quantification of degradation in nonceramic housing materials by laser ablation

A laser irradiation technique has been explored to quantify visible as well as invisible degradation of housing materials used for nonceramic insulators. Nonceramic insulators that were removed from service and new samples of the housing that were subjected to accelerated testing in the laboratory have been evaluated. The method uses a constant power laser source for delivering the same energy to the test specimen. The proposed method is fairly quick and could be looked upon as an additional method for characterizing aging of nonceramic insulators. It has been shown that this method provides a better characterization of aging than is obtained from Fourier Transform Infrared Spectroscopy. The housing materials evaluated include silicone rubber, ethylene propylene diene monomer rubber and cycloaliphatic epoxy resin.     

Quantification of corona discharges on nonceramic insulators

This paper attempts to establish a correlation of the visual images of corona obtained from a camera with discharge magnitude measured with conventional partial discharge equipment. A linear relationship is shown between the transformed image parameters and the discharge magnitude, thereby providing a means for quantifying corona observations made during routine maintenance inspections, of insulators from ground. Different insulator designs using silicone rubber (SIR) and ethylene propylene diene monomer (EPDM) housings were examined. The effect of fog has been examined by performing experiments inside a fog chamber. It is shown that this information can be used along with the corona degradation characteristics of housing materials to identify discharge patterns that can pose problems to the integrity of the insulator.