GB534936A - Improvements in or relating to liquid immersed electric circuit interrupters - Google Patents

Abstract

534,936. Liquids-blast switches; switch cases. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 20, 1939, No. 26228. Convention date, Sept. 21, 1938. [Class 38 (v)] A circuit-breaking assembly, adapted to be housed in a tubular insulating assembly by means of arms 61 on a flanged casing member 59, comprises a pair of series-connected elements 53, 55 separated by a metal section 57. Each element comprises an insulating tube 63 having threaded metal collars 65 at each end and containing a stack of insulating washers 67, 69 of different diameters so as to provide a cylindrical arc-chamber 71 of corrugated section; the lower chamber being of larger diameter. Each element also includes a support 73 carrying four fixed contact-fingers 75, the upper set being connected by flexible shunts 77 to member 59 and the lower by shunts 79 to a conducting part 101 on the operating rod 81, Fig; 5. The main movable contacts 91 and arcing contact 93 for each element is carried on a ring 89 above which is a stack of insulating washers 97, 99, the thickness or spacing of which is such as to prevent their locking with 67, 69. The arcing fingers 93 project into a channel formed by cut-away parts on one sieie of the washers 67, the upper ring 89 and washers 99 being of smaller diameter than the lower ones. A metal sleeve 105 having a corrugated surface to prevent it from binding in the guide plate 165, is threaded on to an upper metal fitting 85 on member 81 and serves to hold all the parts of the member in place on the central insulating core 83. Further guide members 167, 171 for member 81 and actuating member 117 are provided with knife edges, as 169, to clean the surfaces which they guide of solid deposits. The upper end 143 of member 81 is secured to a plate 139 guided on rods 141 which are screwed into member 59 and support a plate 137. A battery of compression springs 135 between plates 137, 139 provide the opening force, the opening stroke being cushioned by a plate 161 and springs 163 guided on the rods 141. The lower metal fitting 85 has threaded to it a metal support 87 on which is threaded a contact structure 111 co-operating with the upper end 115 of actuating member 117 to form a series isolator, which is opened subsequently to, and closed prior to, the contacts of elements 53, 55, the actuating means and substructure being illustrated in Figs. 1 and 2 (not shown) and including a current transformer. When the switch is being opened, and due to the relative diameters of the washers 99 and members 101, 105, the washers 99 behave as pistons causing a partial vacuum above them, into which the arc gases escape, and a pressure below them for sending a stream of liquid longitudinally of the arc to cause it to be quenched at zero of the cycle, so avoiding voltage surges due to sudden reduction of the current to zero.