Surge arrester having coaxial shunt gap

Abstract

A surge arrester of compact construction includes a housing formed preferably of elastomeric material through which a pair of spaced terminals protrude and between which a stack of metal oxide varistor discs is disposed and connected in series therewith. Disposed below the lower one of the discs and in contact therewith is a conductive base plate and an electrode is spaced somewhat from the lower surface of the base plate to form a gap and is provided with shunt means connecting the electrode with the upper surface of the lower disc so that an overvoltage surge condition and the resulting arc across the gap establishes a shunt circuit around the lower disc. Thus the lowermost disc is effectively shunted during surge conditions thereby enhancing the protective response of the device while the lowermost disc is in the circuit during stabilized conditions and effectively increases the overall resistance of the arrester and by this means limits the magnitude of current and prevents undesirable overheating and the attendant run away tendency of the arrester. Since the elastomeric housing is in direct heat transferring contact with the stack of varistors, heat transfer to atmosphere is greatly facilitated.

Dependencies are inferred from the claim text.