GB730709A - Improvements in electric surge arresters - Google Patents

Abstract

730,709. Lightning arresters. E.M.P. ELECTRIC, Ltd. Nov. 23, 1951 [Oct. 7, 1950], No. 6476/54. Divided out of 730,634. Class 38 (4). A lightning arrester includes a spark gap in series with one or more non-linear resistance elements, the spark gap being surrounded by a plurality of ring-shaped shunt resistor elements held under axial compression and so arranged that current traversing them on operation of the arrester travels in a peripheral direction around the elements. The spark gap may be a rod, or sphere, gap, or may be a quench gap for use with a separate switch gap. As shown in Fig. 1, an arrester for use in association with a separate switch gap comprises a quench gap unit G mounted, together with non-linear series resistor blocks 21, in an insulating casing 28 enclosed in an outer ceramic case 29 which may be provided with external sheds. Springs 30, acting on plates 18, 253, 252 maintain the gap unit and blocks 21 under compression. The gap unit comprises electrode discs 25, 251 spaced apart by non-linear shunt resistance rings 24, each embedded in an insulating casing 241 provided with conductive inserts 242 at diametrically opposite points on opposite faces to connect the ring to adjacent electrode discs in such a manner that leakage current is successively around both halves of each ring and then oppositely around the next ring. In a modified arrangement the rings 24 are of ceramic material and are formed with a series of spaced apertures which receive cylindrical non-linear resistors, segmental portions of the faces of the rings being metallized to connect the resistors in series to and cause the leakage current to traverse the rings in a peripheral direction. In another arrangement, the rings are of resistance composition and provided with metallized portions at opposite points on each side of the ring.