Patent GB-238206-A (GB)
Title: Improvements in and relating to the synchronizing of alternating electric current systems
IPC: H02J3/42
Filed: 1925-07-21
Abstract: 238,206. International General Electric Co., Inc., (Assignees of Allgemeine Elektricitõts Ges.). Aug. 6, 1924, [Convention date]. Synchronizing dynamo-electric machines. - Alternating current systems are paralleled by two controlling devices responsive to variations in the sine and cosine respectively of the phase angle between their voltages. The parallel connection is made only when the sine element remains for a given time in its zero position and when the cosine element is deflected in a given direction, conditions characteristic of synchronism of phase and frequency. Means preventing parallelling when voltages are unbalanced may be included. Distant indicating means are provided to indicate frequency and voltage relationships between the systems and the final closure of the parallelling switch. Wireless signals may be transmitted over the power mains for this purpose. Fig. 2 shows two devices 11, 12 of the Ferraris type connected to voltage transformers on the respective supply systems 1, 2 the sine element having an inductance 8 in series with its " current " winding of the cosine element and ohmic resistance 10. The disc 5 of the sine element is connected through a spring 14 to a lever 15 adapted to close switches 16 when deflected from its zero posititon and so short-circuit the " current " winding of the cosine element. The disc 6 of the latter carries a pin 19 which closes a switch 21 controlling the parallelling switch when driven against the spring 17 with a torque sufficient to move it from its zero 20 to engage the switch 21 during the time the disc 5 is in its zero position. The disc 6 is heavily damped by a brake 18. In an alternative arrangement both sine and cosine devices are continuously connected and but slightly damped and a switch, closed by the cosine device when deflected in one direction only and in series with one closed by the sine device when at zero, controls a parallelling switch with a time lag device. In lieu of the time lag device contacts opened by the sine device through the operation of a magnet 22, arranged as described below, may be inserted in this circuit. The inherent time lag of the parallelling switch may be balanced by earlier contact making and by displacing the " voltage " or " current " fluxes of the instruments, or the sine contact maker may have its zero shifted by a sliding coupling with the actuating disc and stops which adjust this coupling, or by adjusting its control spring anchorage. To prevent the operation of the cosine instrument except when the sine instrument is passing through its zero at a low speed a brake magnet 22, Figs. 4 and 5, may be mounted near the disc 5 so as to be moved by it and close a second pair of switches (not shown) shorting the cosine device when the disc speed is excessive. A. contact may be fitted in series with the other contacts and be operated by the sine device when moving in one direction only so that parallelling can only take place when the incoming supply system is ovextaking the other. Parallelling may be prevented when the volts of systems 1 and 2 are not balanced by a Ferraris disc 33 actuated by two opposed magnets 31, 32 fed by the respective systems as in Fig. 6 and arranged to close switches 36, 37 shorting the cosine system when the volts are not equal. The Specification also refers to the combination of a phase meter and contacts actuated by a brake magnet (e.g. 22) for parallelling, and to the use of a contact actuated by the sum of the voltages in place of the " cosine " system. To indicate to a, distant operator the frequency relationship of the two systems the brake magnet 22 on the sine system is used to actuate two switches 24, 25, Fig. 4, which, when the difference in the frequency is considerable, close intermittently the circuit of one of two relays 26, 27 according as one or other supply system has the greater frequency. The relays are energized by the, sum of the voltages of the two systems or they are arranged in series with a contact closed by the cosine device when this has a positive deflection. The relays may be replaced by valves. Similar relays may be used to indicate voltage relationship, switches 42, 43 controlling them being added to the voltage control device of Figs. 6 and 7. The final closure of the parallelling switch and the frequency and voltage relationships of the systems may be signalled to a distance by high frequency currents transmited along the power line, two different modulation frequencies of the carrier wave being employed for the latter. A modulated high frequency wave may be used for the former signal also. The connection of the automatic devices to desired machines may be effected by a separate carrier wave.