Steuerung fuer parallelgeschaltete,unter Last schaltbare Wahlschalter

摘要

991,944. Transformer arrangements. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 18, 1963 [Oct. 1, 1962; Dec. 31, 1962], Nos. 37116/62 and 49101/62. Heading H2H. [Also in Division H1.] A number of parallel connected transformer tap-changers are provided with detecting and control means which ensure that no tap-changer can move out of step with the others by more than one position. Tap changing may be initiated under control of voltage sensing means associated individually, or in common, with the several tapchangers which may operate in a sequential manner to reduce the voltage steps. Fig. 1 shows three multi-position switches M1, M2, M3 which move with three associated tap-changers, relays X1, X2, X3 and Y1, Y2, Y3 being connected so that the appropriate ones of these relays are energized when one of the tap changers gets one position out of step with the others. Energization of these relays (which may have different sensitivities) prevent further onward movement of the last-operated tap changes and movement in the opposite direction of any tap changers which have fallen behind it. Fig. 2 shows a voltage sensitive time delay relay arrangement in which a voltage sensitive coil V closes contacts H or L according to whether its voltage is above or below a predetermined value. Closure of contacts H or L causes closure of contacts Y1 or X1 and hence energize an appropriate tap change by the associated tap changer. If the voltage is too high contacts H are closed, the associated tap changer moves down one step and, if all the other tap changers do not move to the same new step one or more of the Y relays (Fig. 1) is energized and contacts Y (Fig. 2) in circuit with contacts H are opened to prevent any further downward change. With the opening of contacts Y the time delay relay wiper contact r (Fig. 2) is reset to its open position by solenoid l. In addition to the opening of contacts Y the coils, e.g. X2 or X3, associated with the multiposition switch of any tap changer(s) which has not also moved to the next lower voltage step are energized and open contacts X in the time delay relay circuit associated with that tap changer. This ensures that upward tap changing by that tap changer is prevented. An alternative time delay relay arrangement (Fig. 3, not shown) omits the contacts X, Y. A system of switching is described (Fig. 4, not shown) in which the tap-changers are actuated in sequence by a single time delay arrangement as shown in Fig. 2 each tap changer being de-energized after moving one step by its associated X or Y relay as appropriate and contacts being simultaneously closed to actuate the next tap-changer. The control of tap changing may be effected in response to circulating current; a reverse reactance control system being used to energize the means for limiting out of step operation and the switches M1, M2, M3 can then have only one contact each.