Overvoltage surge arrester with means for protecting its porcelain

Abstract

This overvoltage surge arrester has a tubular porcelain housing having a bore, metal terminals at opposite ends of the porcelain housing, stacks of metal-oxide varistor disks located within the housing in angularly-spaced relationship about the bore, and venting means within the terminals for venting gases from the housing should an electric arc develop within the housing as a result of failure of a varistor disk. First liners of electrical insulating material having relatively high thermal conductivity are sandwiched between the stacks and the bore for providing effective heat transfer between the stacks and the porcelain housing. Additional liners are disposed on the bore in locations angularly between the first liners. These additional liners are of a thermal and electrical insulating material, a major portion of which is a ceramic selected from the group of alumina, thoria, zirconia, zircon, and spinel. This thermal and electrical insulating material has a relatively low thermal conductivity and low ablation compared to the material of the first liners and is collapsible in response to arc-produced pressures developing within said porcelain housing, thereby protecting the housing from pressure and temperature shock waves developed by the arc.