SE8903701L - HOEGSPAENNINGSBRYTARE - Google Patents

Abstract

The invention concerns an outdoor circuit breaker which has a contact system enclosed in a casing 1 which is filled with gas, e.g. SF6, at a certain positive pressure. The casing consists of a jacket insulator 10 of porcelain with two flanges 11, 12. A rupture disc 9 prevents the jacket insulator from bursting in the event of an abnormally great increase in pressure in the circuit breaker. If a flash-over takes place in such a way that the arc cannot be extinguished, e.g. across an open pole and a low current (less than approx. 1 kA) thereafter flows for several seconds, there is a danger that the pressure will not rise sufficiently to release the rupture disc 9 while on the other hand the porcelain 10 which in addition is subjected to strong thermal stresses on account of the arc, can break even at the filling pressure. In this case the pressure can be reduced by placing a suitably shaped seal 14 of an alloy with a suitable melting point at the end of a pipe 13 entering from outside which ends in the vicinity of the breaking position. The design and melting point are selected so that the device does not operate in the event of normal breaking. If required this device can be integrated with the fixed contact 4 of the breaker. Alternatively the rupture disc 9 can be supplemented by a device which makes a hole in the disc in the event of too great an exchange of heat between the contacts 4, 5. <IMAGE>