Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: characterisation by contact angle and surface physical morphology

Abstract

High-temperature vulcanised (HTV) silicone rubber composite insulator has been widely used in extra-high and ultrahigh transmission lines due to its excellent electrical and mechanical performance. In practice use, liquids may encounter the composite insulator intermittently and can lead to the degradation and deterioration of silicone rubber. In the present research, the effects of liquids immersion and subsequent drying on the surface properties of HTV silicone rubber were investigated by means of the contact angle measurement and surface physical morphology measurement which was further analysed in terms of the discrete wavelet transform method, multiresolution signal decomposition algorithm, and three-dimensional fractal dimension calculation. Based on the experimental results, the mechanism of the loss and recovery of the hydrophobicity of HTV silicone rubber surface during the liquids immersion and subsequent drying processes were further explained by taking into consideration the embedded water molecules (and/or hydrated ions) on the HTV silicone rubber surface and the synergy of the increase in roughness/fractal dimension and low molecular weight siloxanes diffusion. This study is helpful for better understanding of the change of surface properties of HTV silicone rubber caused by environmental and electrical stresses.

Study on liquids diffusion into and relevant corrosion behaviour of glass fibre reinforced polymer used in high voltage composite insulator

“…Based on the actual operating experience of high voltage composite insulator [8], water (from relative humidity, spray, and rain), salt solution (from dissolving of soluble matter in contamination) and nitric acid solution (generated from the discharge around the high voltage composite insulator in the presence of water, oxygen and nitrogen) are the three kinds of liquid that high voltage composite insulator most commonly encounter during operation. Therefore, these three kinds of liquids were employed in this research.…”

“…To be more specific, the parameter h can be used to give a more quantitative analysis of the corrosion of the epoxy resin matrix of the GFRP plate surface. We further define the h max the maximum of profile height deviation by (8)…”

“…More specifically, as for the GFRP used in high voltage composite insulator, the diffusion of liquid into GFRP can increase the leakage current passing through the GFRP [27]. Furthermore, it should be stressed that the fracture of composite insulator is considered the most serious accident, the diffusion of liquids into GFRP rod and relevant corrosion behaviour can lead to the failure and fracture of high voltage composite insulator, the brittle fracture and the Decay-like fracture of high voltage composite insulator have a direct relationship with liquids diffusion and relevant corrosion behaviour [8,[28][29][30], in detail, the brittle fracture is responsible for the stress corrosion cracking under low-mechanical stress in the presence of a wet environment and the Decay-like fracture is responsible for the electrical erosion in the presence of a wet environment [31].…”

“…Specifically, in the field of electrical power transmission, GFRP is used as inner insulation of high voltage composite insulator [5, 6] applied in extra‐high voltage and ultra‐high voltage transmission lines with rated voltage ranging from 110 to 1100 kV [7]. In more concrete terms, the GFRP rod in high voltage composite insulator is the principal load‐bearing component, which is attached to metal end fittings and protected by silicone rubber housing from outside electrical and environmental stresses [8]. In actual use, high voltage composite insulator may suffer from many kinds of electrical and environmental stresses [9, 10], such as corona discharge, arc, moisture, rain, acid rain, ultraviolet exposure and pollution contamination, among these stresses, the liquids ingress is considered to play an important role in the aging phenomenon of high voltage composite insulator.…”

Performance of Silicone Rubber Composites Filled with Aluminum Nitride and Alumina Tri-Hydrate

“…High-temperature-vulcanized silicone rubber (SR) is widely used to manufacture high voltage insulators due to its relatively light weight and excellent anti-contamination ability [1][2][3][4]. It is often filled with suitable additives so that the performance of the SR composites can be improved [5][6][7][8][9][10][11].…”