Patent GB-337032-A (GB)
Title: Improvements in or relating to the automatic or semi-automatic control of synchronous dynamo-electric machinery
IPC: H02P9/42
Filed: 1929-07-25
Abstract: 337,032. Reyrolle & Co., Ltd., A., and Lambert, D. E. July 25, 1929. Synchronizing dynamo-electric machines; running generators in parallel; regulation, automatic. -The frequency of a system particularly where A.C. generators in parallel are employed is controlled by apparatus mainly as described in. Specification 303,779 modified inasmuch as a contact making rotary synchroscope is included. The present invention is also applicable to the control of A.C. motors when a source of E.M.F. dependent on the speed of the motors is available. The frequency-controlling means are combined with load-sharing arrangements for a group of parallel-operated machines so that the load-sharing device associated with each machine prevents alteration of the speed of the machine when the share of the load taken by such machines be varied beyond predetermined limits so that alteration would tend to cause the machine to deviate still further from such limits. The apparatus may be used for the automatic synchronizing of an additional machine, when required, and the arrangement may be applied to the automatic remote control of frequency and load from a control station of a system supplied from a number of generating substations and for hand-control of the distribution of load between the various substations, with or without automatic synchronizing of additional machines in each station under the control of a suitable selective remote control system. Fig. 1 shows the application of the apparatus to the frequency and load-sharing control of a system employing two A.C. generators in parallel. Load-sharing devices M of the kind described in Specification 296,815 are incorporated. Two A.C. generators A are shown connected to A.C. mains by main circuit-breakers L. A contact-making rotary synchroscope F together with relays J, O, and timedelay relay P together with the source of E.M.F. of constant frequency D in the form of a A.C. motor driving a single-phase generator form the control apparatus common to the system. The movable member of the synchroscope operates contacts by, for example, mounting a conducting member longitudinally on an insulated cylinder rotating with the pointer E3 to co-operate with fixed segmental brushes arranged in three coaxial rings surrounding the insulated cylinder. Various ways in which the synchroscope may cause the transmission of the speed controlling currents may be employed as, for examples, the synchroscope pointer may be provided with a friction device which makes one or the other of two sets of contacts in accordance with the direction of rotation of the pointer. An interrupter may then be incorporated to cause the transmission of impulses instead of continuous current. As shown in Fig. 1, three rings of segmental brushes are concentrically arranged in one plane and the conducting member E4 is carried by the pointer in a radial direction. The outer ring contains four brushes F, Fl, F2, F3. The middle ring contains one continuous brush G1 and the inner ring contains three brushes H, H1, H2. When the apparatus is being used to control the frequency of a system with A.C. generators working in parallel the coil E1 is energized from the source of current of constant frequency D, D1 and the coil E2 is connected across bus-bars C, C1 which are connected through plugs B, B1 to the leading and lagging phases A2, A4 of potential transformers A1 associated with each generator. If the system frequency is higher than the standard frequency the synchroscope pointer E3 rotates say in a clockwise direction. Brushes F, F1, F2 and F3 may be called in order " Make," " Lower speed." " Break," and " Raise speed," contacts. The middle brush G1 is permanently connected to the negative side of D.C. bus-bars C3, C4. When the pointer E3 is on the " Make " contact the operating coil of a relay J will be energized and auxiliary contacts J1, J2 closed. At the same time a retaining- circuit will be made through contacts J3. When the pointer moves to brush Fl, a current will be transmitted through E4, F1, contacts J1, through bus-bar C5, through auxiliary switches L2, on main circuit-breakers L through contacts M1 on the load-sharing devices if the loads on the machines are not too low, through operating coils K1, through auxiliary switches L4 and contacts 02 to the positive D.C. bus-bar C4. Energization of coil K1 closes a circuit to motors K2 which operate to vary the speed governor on say the prime mover driving the generators. When the pointer E3 passes to the "break" contact F2 the coil J is short-circuited and further movement of the pointer to brush F3 causes no transmission of current as contacts J1, J2 are open. The operation is repeated if the pointer continues to revolve in a clockwise direction. When the pointer rotates in the opposite direction the " raise speed " bus-bar C6 is energized and by energization of coil K the motors K2 actuate the speed governor in a direction to raise the generator frequency. The load-sharing devices M' are described in the Specification 296,815. When it is desired to synchronize an additional machine the synchronizing-plugs B2, B3, B4, B5 axe inserted. The circuit-breaker of the incoming machine will be open and the closure of plug contacts B2 energizes operating coil 0 to disconnect the source of constant frequency current D, D1, and energize coil E1, of the synchroscope from the leading phase A2 of the potential transformer on the incoming machine through contacts 01, and at the same time open contacts 02. The pointer E3 revolving in a clockwise direction passes in order over inner brushes H, III and H2 when the incoming machine is running up to speed. When the contact. E4 engages with brush H1 the coil P of a time-delay relay is energized and closes auxiliary contacts P1, but on passing on to brush H2 coil P is short-circuited and contacts PI open. At the same time the brushes F, F1 F2, F3 are operating as before to bring the incoming machine up to speed, the coils K1, K1 now being energized through auxiliary switches L2, L3 and L4 direct from the D.C. bus-bars C3, C4. When the incoming machine is just over speed the pointer slowly rotates in an anti-clockwise direction and after passing over brush H2 passes to brush HI energizes coil P and due to the slow rotation allows the relay P to close contacts P1. When the pointer reaches brush H if moving sufficiently slowly a current is allowed to flow from brush G1 through E4, H1, contacts PI, bus-bar C7 through closing coil L1 of main circuit-breaker through plug contacts B3 to D.C. bus-bar C4 thus closing breaker L and connecting generator A with the A.C. mains. An arrangement adapted to control the frequency of two A.C. machines running in parallel is similar to that shown in Fig. 1, except that no provision is shown for synchronizing an incoming machine and the load-sharing device takes the form of a relay which may be of the beam type having two operating coils acting differentially on the contact-operating beam.