| The growing market for improved materials in high-voltage components is driven largely by a need to reduce overall operating costs and improve system reliability. The cost advantages of silicone insulators are especially evident in situations where long-term reliability and maintenance-free performance is a concern, such as coastal regions and high-contamination environments. For these reasons, Dow Corning, USA, has recently been developed a new generation of silicone rubber compounds that are suitable for moulding high-voltage insulators, surge arresters, weather sheds and other HV-components. All are high-consistency rubber (HCR) products in the Dow Corning� 1600 series, designed to deliver outstanding tracking resistance over a wide voltage range, superior wet electrical performance, hydrophobic transfer and recovery, as well as good mould release and other processing characteristics. Dow Corning� HV 1650-50 silicone rubber (type ASTM D 1418 VMQ) is a 50-durometer material designed with low-modulus, primarily for moulding surge arresters. Sister products, Dow Corning� HV 1660-65, Dow Corning� HV 1666-65 and Dow Corning� HV 1660-75 silicone rubbers, are 65- and 75-durometer formulations which were specifically developed for moulding high-voltage insulators and weather sheds. All silicone rubbers from the HV 1600 series feature good processing characteristics for easy moulding with injection, transfer or compression methods.
The Dow Corning HV 1600 series HCRs deliver excellent electrical properties, including a dielectric strength greater than 17kV/mm (440 volts/mil) per IEC 243 and a dielectric constant up to 3.67 at 100Hz (IEC 250). These products are supplied as one-part, fully compounded, ready-to-run materials to help molders achieve faster processing and eliminate the need for mixing. The Dow Corning 1660 series materials exhibit excellent arc tracking performance and erosion resistance over a wide voltage range (between 3.5kV and 6.0kV), and they are extremely stable in difficult environments. The Dow Corning HV 1600 series materials deliver excellent recovery and transfer of hydrophobic properties after periods of high-surface electrical activity. The result is better electrical performance and management of surface leakage currents, which helps avoid electrical flash-overs, reduce maintenance and extend service life.
Supplied as a high-consistency elastomer (either preformed or in bulk), these silicone formulations cure to a lightweight, shatter-resistant composite that helps suppress leakage current and arc tracking. The materials resist erosion and extend service life, especially in severe operating environments. Silicone insulators also resist the weathering effects of ultraviolet light, ozone and extreme temperatures, and have vastly superior mechanical shock properties when compared to ceramics, glass, epoxy or other rigid materials. The new silicone materials from Dow Corning also exhibit easier mould flow, faster cure and less fouling than earlier generation materials, and consequently reduce manufacturing costs. Dow Corning� HV 1650-50, 1660-65, 1666-65 and 1660-75 silicone rubbers are available in 500kg boxes, either preformed or in bulk. When stored at or below 5O�C in the original, unopened containers, the products have a usable life of 12 months from the date of manufacture.
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