Patent GB-263980-A (GB)
Title: Synchronizing systems for interconnecting electric distribution circuits
IPC: H02J3/42
Filed: 1925-11-06
Abstract: 263,980. British Thomson-Houston Co., Ltd., (General Electric Co.). Nov. 6, 1925. Synchronizing dynamo-electric machines.- Electron-discharge devices are used to cause operation of a synchronizing switch for interconnecting two electric power sources or systems when they are in phase or operating at substantially the same voltage or frequency. In the system shown in Fig. 2, the switch 2 closes when the frequency supplied to a resistor 17 and reactor 16 decreases to a certain value. As the frequency decreases, the voltage drop across the reactor 16 decreases, therefore the potential of the grid 7 of a valve 4 increases and an anode current circulates through the closing coil of the switch 2. By interchanging the resistor and reactor relatively to the cathode and grid of the valve, the switch is closed when the frequency rises to a predetermined value. In the system shown in Fig. 3, the source 19 is operating at normal frequency and the source 18 at a high but decreasing frequency. These sources are cross connected through reactors 21, 22 and resistors 20, 23, the grid circuit of the valve being connected across the resistor 20. As the frequency of the source 18 approaches that of the source 19, the frequency in the reactor 21 decreases towards zero, thus causing an increase of voltage drop across the resistor 20. This voltage drop only reaches the maximum when the two sources are in phase, whereupon the valve 4 passes an anode current and the switch 2 closes. If the source 18 is being brought up to synchronism with the source 19 instead of falling thereto, then the grid circuit is connected across the reactor 21 instead of the resistor 20. In a slight modification the cross connections between the sources 18. 19 are purely resistors, across a part of one of which the grid circuit is connected, and the grid circuit includes a condenser in place of the reactor. In the system shown in Fig. 5, the switch 2 closes when the voltage of the two sources 18, 19 are equal. The two A.C. voltages are rectified by valves 32, 36 and are impressed respectively on resistors 30, 34 which are connected in series opposition across the grid circuit of the valve 4. When equality of voltage is attained, the valve 4 ceases to pass an anode current, and the switch 2 drops to its closed position. A condenser 27 and resistance 26 may be arranged to delay the closure of the switch 2. In the system shown in Fig. 6, the sources 43, 44 are connected by a switch 52 which closes when the three switches 150, 54, 51<1> close, and these latter close respectively when phase and frequency, when frequency, and when phase and voltage are the same in the two sources. A usual type of electrodynamic device 42 drives a dynamo 50 connected to the cathode 55 and grid 57 of a valve, in the anode circuit of which is the coil of the switch 54. Thus this switch drops when the device 42 ceases to rotate, that is when equality of frequency exists. The device 42 also rotates a disc 151 having an insulating segment 161 connected in the grid circuit of a valve 152, the anode circuit of which includes the coil of the switch 150. When the phases are the same, the segment 161 stops under one of the brushes and the switch 150 drops to the closed position. Owing to time lag in the switch 150, it does not close when the segment 161 passes under the brushes at a moderate speed, that is when there is a substantial frequency difference. The voltage drop across part of a resistor 63 connecting the two sources is impressed on a valve having two grids 61 and anodes 59. When the voltages of the sources 43, 44 attain equality and are in phase, anode current ceases to flow through the coil of the switch 55', which thereupon drops to its closed position. This system may be modified by causing the device to drive an alternator, across the slip rings of which is connected a reactor and the grid and cathode of a valve, in, the anode circuit of which is the coil of the switch 52. In the system shown in Fig. 7, the switch 68 connects the sources 66, 67 when switches 71, 72, 73 close, these closing respectively when frequency, voltage and phase equality is attained. The grids of a double valve 74 are energized according to the voltage drop across reactors 80, 81 in a high impedance circuit which also includes resistors 82, 82<1>, 83. As the frequencies of the sources attain equality the voltage drop across the reactors falls to zero, thus the anode currents cease and switch 71 drops to its closed position. A valve 89 rectifies the voltages of the two sources and impresses them upon a resistor 96, so that the voltage thereacross is proportional to the difference of the voltages of the sources, and is impressed across the cathodes and grids of a double valve 90. When the voltages attain equality, the cathode currents of the valve 20 cease, and switch 72 drops to its closed position. A double valve 107 rectifies both supply voltages and impresses them upon resistors 116, 117 which are connected in series, with the negative terminal connected directly to a cathode 127 of a valve 108 while the positive terminal is connected through conductor 119, source 67, resistor 83<1>, source 66, conductor 120 with a grid 125. Another double valve 108' functions similarly to the valve 107, only the negative of the associated resistors 116<1> 117<1> is connected to a grid 126 while the positive is connected through the two sources to a cathode 128. When both sources are in phase, no current flows in either of the coils of the switch 73 which therefore drops to its closed position.