Patent GB-190504878-A (GB)
Title: Improvements in and relating to Electric Distribution Systems and Controlling Apparatus therefor.
Filed: 1905-03-08
Granted: 1906-02-01
Abstract: 4878. British Thomson-Houston Co., and Wedmore, E. B. March 8. Distributing.-In an alternating-current distributing-system having two or more sets of parallel feeders supplying common bus-bars through transformers, means are provided for automatically disconnecting a transformer secondary from the bus-bars when the feeders supplying this transformer are disconnected at the main generating- station or upon the occurrence of a fault. The two sets of feeders A, A', Fig. 1, supply current to the bus-bars C through transformers B, B' and automatic switches D, D<1>. In one of the feeders of each set there is provided a transformer E, E', the secondaries of which are connected in series and are shunted by a circuit F, in which are arranged a pair of solenoids G, G<1> which act differentially with potential coils H, H<1> on the release gear of the switches D, D'. The potential coils are excited from the bus-bars through a starresistance C' or in any suitable manner. If the feeders A, A' are unequally loaded, a current flows through the shunt F, the direction depending upon the feeder which is more heavily loaded. For example, when the primary side of the feeders A is disconnected from the source of supply, the current in the shunt F causes the coil G to assist the trip-coil H to open the switch D, while the coil G<1> opposes the trip-coil H<1> of the switch D<1>. The current flowing in the shunt F may be utilized to operate the switches in other ways, for example, as described in Specification No. 22,465, A.D. 1903. The Provisional Specification states that in some cases the electro-magnetic tripping- devices may be interlocked so as to prevent the operation of more than one switch at a time. Fig. 2 shows the application of the invention to a single-phase distributing-system, in which the tripcoils N, N' for the switches M, M' are connected in circuit between a pair of contact-studs O, O<1>. The secondaries of the transformers P, P<1> are in circuit with the stationary windings Q, Q<1> of a reverse-current protective device such as that described in the above-mentioned Specification. The shunt R across the transformer circuit contains a movable coil S mounted upon a pivoted arm S<1> and carrying a contact S<2> which normally engages with a stud O<2>. One extremity of the coil S is connected to the contact S', which is sufficiently broad to contact with either of the studs O, O<1> before it leaves the stud O<2>. The coils Q, Q', S are mounted upon a common magnetic core. When one set of feeders is disconnected, the coil S is excited by the shunt current, and, by the combined attraction and repulsion of the fixed coils Q, Q<1>, the contact S<2> is moved into engagement with one or other of the contacts O, O<1>, to energize the trip-coil N or N', which thereupon opens the corresponding main switch. In order to re-set the coil S, shunt circuits T, T' to the transformers P<1>, P are closed at the contacts T<2>, T<3> when the switches M, M' are opened. In a multiple-feeder system, the series transformers P, P<1> of all the feeders have their secondaries connected in series, and each secondary is shunted by a coil controlling the circuit-breaker of the feeder. In a polyphase distributing-system, the arrangement may be applied to one or more of the phases of each set of parallel feeders. In place of differentially-wound coils acting directly upon the main switches, the coils may energize relay operating-devices.