GB353924A - Improvements in protecting devices for electric circuits - Google Patents

Abstract

353,924. Protective arrangements. EDISON-SWAN ELECTRIC CO., Ltd., 123, Queen Victoria Street, SHOTTER, G. F., 14, The Ridgeway, Friern Barnet, both in London, and GREETHAM, E., 27, Louis Street, Hull. Jan. 29, 1930, No. 3084. [Class 38 (iv).] A protective device against excess voltage comprises an electric discharge tube having normally cold electrodes of a refractory material and filled with a permanent gas such as neon or a mixture of such gases the shape and arrangement of the electrodes and the pressure and nature of the gaseous filling being so correlated that at normal voltage no current passes through the tube. Excess voltage causes first a glow discharge and, when the current rises, an arc discharge. To offset the negative characteristic of the arc a trace ol gas having a high thermal conductivity, as hydrogen, may be introduced. Two of the electrodes 4, as shown in Fig. 1, may be connected to the conductors and the third to earth. The electrodes are shaped so that the discharge takes place at the points and shrouds 8 of metal of high heat conductivity or of insulating material also facilitates localizing of the arc. Auxiliary electrodes 9 as shown in Fig. 2 may be introduced and connected to the main electrodes 4 through resistances 10. Various applications are described and the discharge current may be used to energize the tripcoil 19, as shown in Fig. 5, to open a main circuit-breaker.