Iberdrola 400-132-66-20kV substation at Rocamora - Application of rtv silicone HVIC Insulator Coating to provide reduced maintenance protection against Pollution-induced flashovers.
Rocamora substation is shared between Iberdrola (400-132-66-20 kV) and another company (400 kV transmission side). Located nearby a quarry, the substation receives contamination from agricultural activities, and some saline pollution from the sea. Additionally the area receives very little rain (<340mm/year), most of the time in the form of very heavy storms and the winds from North Africa (Saharan dust aerosols) can cause the rain to acquire the consistency of mud.
Iberdrola management observed an increased need for energy as well as a change in seasonal demand from winter to summer due to heavy air conditioning usage. Combined with the high ambient temperature of above 40ºC, this makes for very difficult service conditions. It became urgent for Iberdrola to ensure in Rocamora a consistent supply to their customers.
Until now, to protect the substation, Iberdrola had been spraying the insulators with a silicone fluid. Unfortunately, the fluid became saturated with dust and required frequent replacement. Based on their experience with rtv silicone coatings at other substations, Iberdrola decided to coat the insulators at Rocamora with rtv silicone to reduce pollution-induced flashovers and provide a long-term, low maintenance solution.
Most of the insulation at the substation is porcelain, except for some HTV silicone bushings on a transformer and a circuit breaker. During application tarpaulins, supported on the scaffolding, were used to protect the targeted elements and adjacent ones from overspray and/or losses due to the virtually ever-present wind. Shrink film was used to avoid spraying Sylgard HVIC+ onto fittings and other equipment.
The insulators were first cleaned with solvent (xylene and naphtha) and, immediately prior to spraying, isopropanol was applied. Sylgard HVIC+ was applied slightly diluted and, after the initial coat, subsequent coats were applied to build a thickness of 400 microns minimum. According to Iberdrola, the application time was around 10% less than for other RTV silicone coatings.
Coating thickness was checked by cutting out a small section, which was examined with an optical paint inspection gauge. This combined a 50X microscope and a micrometer gauge with a 2,000 micrometer scale. If the coating was under 400 microns then additional coats were applied until the coating reached this minimum thickness, however not exceeding 500 micrometer upper limit.
The Sylgard HVIC+ surface finish was smooth and its enduring hydrophobicity will ensure long-term, maintenance-free service.