GB388465A - Improvements in and relating to metal vapour electric discharge valves - Google Patents

Abstract

388,465. Protective cut-out systems. AKT.-GES. BROWN, BOVERI, ET CIE, Baden, Switzerland. Oct. 1, 1931, No. 27378. Convention date, Feb. 2. [Class 38 (v).] To extinguish the arc in a metal vapour discharge valve used as a protection in transmission lines, a condenser is connected, through a spark gap, in parallel across the valve, and the spark gap has an ignition transformer with additional magnetization opposed to that of the primary winding. In a circuit for extinguishing a valve on a high voltage surge occurring in continuous current supply mains, the additional magnetization is such that with full normal load passing through the primary the transformer is working at the lower elbow B, Fig. 1, of the magnetization curve. Fig. 2 shows one circuit, wherein the transformer 4 ignites the spark gap 6a, 6b which thereupon connects the condenser 5 across the valve 3. The additional magnetization is supplied by a winding 46 whi h may be fed from the line, as shown, or from a separate source. The condenser 5 is charged through the resistance 16. The choke coil 11 prevents an excess current from flowing in the winding 4b and blows the arc 6 against an electrode 6c which short-circuits the ignition winding 4c so that its reactance does not reduce the peak value of the discharge current of the condenser. In a modification, Fig. 3, two spark gaps 6 and 12 are used, the ignition of the latter allowing the condenser to discharge over the former without the use of a third electrode.. The coil 11 is used to extinguish the arc in the horn spark gap 12 ; its action is assisted by an auxiliary electrode 14 connected to one horn through a condenser 15. The spark gap 6 may be caused to act first by connecting the winding 4c to the positive main. In a further modification the winding 4c acts also as the additional magnetizing winding and the winding 4b is dispensed with. The magnetizing winding 4b may be fed from a separate source which may also control a blocking grid in the valve 3.