Patent GB-276552-A (GB)
Title: Device for automatically disconnecting faulty conductors in electric mains
IPC: H02H3/06
Filed: 1927-01-10
Abstract: 276,552. Schild, S. Jan. 10, 1927. Cut-out arrangements. - A number of feeders a<1> - - a<3> connected to a common bus-bar S are protected by circuit-breakers b<1> - - b<5> which have tripping coils (on the left-hand side) and resetting coils (on the right) the resetting being effected, after fault, in accordance with the conditions of the several lines as determined by a high testing voltage supplied from a separate small generator g and imposed on the lines in succession through a number of rotary controller switches k<1>, k<2>, k<3>. In the arrangement shown, applied to an A.C. circuit the reduction of voltage at the transformer T due to a fault releases a voltage relay N<1> which effects the tripping of all the circuitbreakers of the feeders. At the same time the relay N' closes contacts which complete the battery supply circuit to a small motor f driving the A.C. generator g and also the controllers. The controllers, as their rotating arms go round through the positions indicated, serve to connect the primary p' of a testing transformer to the testing voltage, in turn to connect the feeders to the secondary p<2> of the testing transformer and, if no fault exists on the lines after test, to energize the resetting coils of the circuit-breakers. If after the fault and the testing and resetting process has begun a voltage exists on the first feeder (notwithstanding that its circuit breaker is open), a voltage appears on the primary p' (acting as a secondary) and this voltage causes the opening of an alien voltage ' relay i which prevents the testing voltage from being put on the feeder and prevents the resetting action. If such alien voltage does not exist, the current taken from the auxiliary generator by the primary p<1> through the relay M<1> is small if there is no short-circuit on the tested feeder to which the secondary p<2> is connected. In consequence, relay M<1> is not operated and a reclosing circuit for the circuit-breaker b<1> is completed from the auxiliary battery through the relay M<1> and through the contact 1 of controller k<3> in position W of the controller arm. The remaining lines are tested and if sound reconnected as the controller arms rotate. The motor is automatically switched off and the contact-arm l<3> remains at position 6 until the normal working voltage appears on the lines whereupon the voltage relay N<2> closes, restarts the motor which automatically stops again at the original position. In the case of D.C. tapped resistances take the place of the transformers. In a modification, holding relays are introduced to prevent automatic testing or resetting of a line under inspection or repair and to cut out remote control and return signalling devices during the resetting process. Provision is also made for testing the bus-bar independently. In a further modification, the auxiliary testing transformer p<1>, p<2> is dispensed with and the transformer T (which may be the usual measuring transformer) is made to serve this purpose. The several drums nf the controller may be combined into a single drum and the resetting of all the circuit-breakers may take place together after each feeder has been successively tested.