Patent GB-653840-A (GB)
Title: Improvements relating to the control of automatically reclosing circuit breakers
IPC: H02H3/07
Filed: 1947-12-31
Abstract: 653,840. Protective cut-out arrangements. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 31, 1947, No. 35374. Convention date, July 30, 1942. [Class 38(v)] A circuit-breaker interconnecting two networks, or portions of networks, is automatically reclosed when the distance between the contacts and the angular deviation between the voltages of the networks are in a desired relationship to each other. In addition, the reclosure may be made dependent on one or more of the following conditions, (a) the slip between the frequencies of the networks does not exceed a certain value, (b) a serious network fault does not exist, and (c) not more than a certain difference in magnitude exists between the voltages on either side of the breaker. The angular deviation of the voltages may be measured by a synchroscope or a voltmetric relay, and the slip (b) may be measured by comparison of the angular deviation and the time taken for arc extinction on opening, as by a voltmetric relay, a chronometric relay, or a motor-driven distributer. The position of the contacts may be given by a Selsyn equipment successively operated contacts or a rheostat operable by the moving contact, and the soundness of the networks may be tested by measuring their resistance or impedance. The synchroscope comprises a needle, (Fig. 5, not shown), adapted to engage successively contacts respectively connected in series with contacts of chronometric relays which are set in operation when the breaker starts to open, these contacts being in series with the reclosing coil of the breaker. The voltmetric relay, (Fig. 6. not shown), comprises a balanced beam acted upon by two coils, one of which is connected to a condenser, and the other of which is fed by a composite voltage obtained from the two single-phase network voltages. In its balanced position, the circuit of the reclosing coil is completed. In Fig. 7, the needle 13 of a synchroscope 12 cooperates with a contact 17 on an insulating ring 18 which is rotatable by a reversible motor 19. When the breaker is closed, the needle is in the position shown and the contact 17 is adjusted according to the characteristics of the breaker. When the latter opens, the needle moves to the left or right and after a delay a contact 21AV or 21AR is engaged to start the motor 19 so that the ring 18 begins to rotate in the same direction at a constant speed different from that of the needle 13, so that eventually contact 17 is engaged and reclosing coil 14 energized. In a modification, (Fig. 8, not shown), the feature of measuring the position of the movable contact is combined with that of measuring the angular deviation and the time, by using a Selsyn equipment. The relays responsive to the various conditions may be connected as shown in Fig. 1, wherein the contact H represents the relay measuring the angular deviation of the voltages of the networks B, C. L represents that measuring the contact position, K represents that measuring the slip between frequencies, M that governed by the condition of the networks, and N that measuring the magnitude of the voltages, the reclosing coil G of the breaker A being energized when the contact E of an  automatic control unit D is closed. In a/ modified arrangement, Fig. 11, the interval of time since opening of the breaker contacts is shown by a contact K<SP>1</SP> connected in series with the contact H. When these contacts are both closed, a coil 24 is energized to close its contacts 24-1 ... 24-3. the contact 24-1 being a maintaining contact for the coil which is also fed over the contact 27-1 of a relay 27 when one or more of the breaker poles is open. A reclosing relay 14-1 &c. is energized when the appropriate contact L is closed on opening of one breaker pole, provided that the contact 24-3, which reopens after a time delay, is still closed. If reclosure is not effected after one or two attempts in the time during which contact 24-3 is closed. a contact 24-4 of relay 24 closes with a time delay to energize release coils 26-1 ... 26-3 over contacts 28-1 ... 28-3, thereby opening all of the breaker poles. When all the poles reclose, the relay 27 is de-energized and its contact 27-1 opens after a delay, thereby de-energizing coil 24 and returning the arrangement to normal. The Specification also sets out in detail and with reference to curves, the theory underlying the invention. The Specification as open to inspection under Sect. 91 refers to French Specification 832,525. This subject-matter does not appear in the Specification as accepted.