Pollution Maintenance Techniques in Coastal High Voltage Installations

Abstract

Pollution of outdoor high voltage insulators is a common problem for utilities, with a considerable impact to power system reliability. In an effort to prevent possible flashovers due to pollution, many methods have been applied, aiming to improve the insulation performance, either by suppressing the formation of surface conductivity or by increasing the possible insulation level. In the case of substations, the selection of the appropriate technique is complex due to certain issues correlated to the nature of the installation. In this paper, several techniques usually implemented by utilities, are investigated based on the experienced gained in the case of Crete, a Greek island in southern Europe, where due to the coastal development of the power system, the majority of high voltage installations are exposed to intense marine pollution. The technique of coating insulators with Room Temperature Vulcanized Silicone Rubber (RTV SIR) has proved rather efficient and therefore is presented extendedly. Correlation of the material behaviour with environmental conditions is discussed and results from long term monitoring, including environmental parameters and leakage current measurements, in a 150 kV Substation are presented. It is shown that RTV SIR coatings have remarkably suppressed surface activity and that porcelain insulators exhibit different activity period when coated.

Comparative Investigation of Pollution Accumulation and Natural Cleaning for Different HV Insulators

“…However, the duration and intensity of rain are important factors that should be taken in mind, as light rain and mist tend to lightly wet a surface with no real cleaning effect, leading to accumulation of surface contaminants. Unlike light rain, longer and heavier rainfall events wash the surface and this stops the localized concentration effect from occurring [1][2][3][4]17].…”

“…Therefore, the most complex issue is probably the pollution phenomenon [1][2][3]. Pollutants are deposited on the insulators' surface and, usually under the presence of a wetting agent, form a conductive film on the surface allowing the flow of leakage current [1][2][3][4][5]. This may result to dry bands formation and discharges, which under favorable conditions eventually lead to a flashover [1][2][3][4][5][6].…”

“…Pollutants are deposited on the insulators' surface and, usually under the presence of a wetting agent, form a conductive film on the surface allowing the flow of leakage current [1][2][3][4][5]. This may result to dry bands formation and discharges, which under favorable conditions eventually lead to a flashover [1][2][3][4][5][6]. Besides the obvious factor of the pollution quantity and quality present in the area, the interest is focused on the actual amount of pollutants that remains on the surface during long-term service condition.…”

“…Strong winds and a prolonged dry season add significantly to the problem [9]. The Greek utility (initially the Public Power Corporation (PPC) and now the Hellenic Electricity Distribution Network Operator (HEDNO)) have employed several remedies to cope with the problem over the years [4,[8][9]. RTV SIR coatings have been extensively used in substations [9] whereas, as of 2014, HTV SIR have replaced the traditional glass and porcelain insulators in most transmission lines [10].…”

Investigation of Leakage Current Waveforms Recorded in a Coastal High Voltage Substation

“…Contamination combined with wetting, in the case of ceramic insulators, results to the formation of a conductive film on the insulator's surface, which permits the flow of leakage current which in turn can result to the formation of dry bands, arcing and eventually flashover [1]. Polymer insulators and coatings are used as an improvement to ceramic insulators because of their hydrophobic surface which results to the formation of water droplets on the surface, instead of a film [2][3][4][5]. However, hydrophobicity is suppressed and recovered due to aging and the environmental and electrical stress applied [2,3].…”