GB216783A - Improvements in and relating to automatic reclosing circuit breaker systems - Google Patents

Abstract

216,783. British Thomson-Houston Co., Ltd., (General Electric Co.). Oct. 25, 1923. Cut-out systems.-In an automatically reclosing circuit-breaker system, the load resistance is so connected in relation to other fixed resistances as to constitute one arm of a Wheatstone bridge, the " galvanometer connection " being constituted by an electron discharge tube the current in which is independent of the voltage of the supply, varies directly with the load resistance and serves to operate a reclosing relay. As shown, the direct current generator 2 supplies the load R<4> through a circuit-breaker 1 which is shunted by a resistance R, R<1>. On overload, the relay 14 opens and the closing and maintaining coil 5 is de-ernergized so that the back contacts 8 are opened and the back contacts 16 closed supplying current to the time relay 17 which closes the contacts 19. This connects two resistance arms R<2>, R<3>, themselves connected together through the cathode 23 of an electron discharge device, to the supply circuit. The other two arms of the bridge are constituted by the resistance R<1> and the load resistance R<4>. The grid 26 is connected in the galvanometer connection, being connected at the junction of the resistances R<1>, R<4>. The plate 25 is connected through the coil 13 of the reclosing relay to the positive of the generator and consequently is more positive than the cathode. The resistances R', R<2>, R<3> are chosen of such value that, with a given generator voltage and the circuit-breaker open, the potential difference between the points to which the cathode and grid are connected is zero when the load resistance is such that the circuit-breaker may safely be reclosed. The relay 13 is so designed that it will operate in response to the value of current that flows through the tube when the potential difference between the points referred to is zero. In order, however, to obtain sufficient current through the tube to operate the relay in the above conditions a battery 20 is connected in series with the grid.