External Insulation Alternatives for EHV and UHV Bushings by Paolo Cardano
Different housings are available these days for the external insulation of EHV and UHV bushings. These include: porcelain, which may or may not also be coated with RTV silicone material to improve pollution performance; hybrid housings consisting of a porcelain core with a polymeric housing; and a composite housing based on an internal FRP tube over which a polymeric housing has been molded. Each of these alternatives offers different benefits in terms of factors such as safety, pollution performance, seismic performance, icing performance, etc. For example, in regard to electrical performance, different housing solutions can be broadly grouped into two categories: hydrophobicity transfer material insulators and non-HTM solutions. This presentation analyses the relative advantages of these different alternatives when considering the full range of design aspects and requirements. The analysis will focus on EHV and UHV applications and is based on tests performed at laboratories worldwide.