| 摘要 |
<p>1,102,552. Protective systems. ENGLISH ELECTRIC CO. Ltd. 14 Sept., 1965 [16 Sept., 1964], No. 37916/64. Heading H2K. [Also in Division H3] In a protective relay responsive to an input signal and requiring a power supply, this supply is provided by a battery when a D.C. output derived from the signal is of insufficient magnitude, but when the output is sufficient it provides the power supply for the relay and charging current for the battery. The Figure illustrates a power supply circuit for a distance relay (not shown) and includes two input circuits 10 ... 13 and 16 ... 19 providing D.C. outputs dependent on the voltage and current respectively of a protected circuit. When the voltage is normal, a battery 30 is charged from the circuit 10.. .13 through a diode 25 and a Zener diode 22 breaks down so as to render transistors 27, 28 conductive and thus provide a D.C. supply to the relay measuring circuits (represented by a resistor 26). Similarly, when the current is sufficient, the output from the circuit 16 . . . 19 increases the voltage across a resistor 24 to cause the transistors 27, 28 to conduct and the battery to charge if the voltage on diode 25 is sufficient. A similar arrangement of diode 31, battery 36 and transistors 33, 34 provide a D.C. supply for supervisory circuits (represented by a resistor 32). A safety circuit which decreases the relay operating time when a power line having a fault near the relay point is switched in, may be provided. This safety circuit includes a transistor 40 which is rendered conductive by the initial charging current of a capacitor 39. A holding current for the transistor flows through a resistor 45 and diode 43 after a delay provided by the charging of a capacitor 44, this delay preventing incorrect operation due to spurious signals.</p> |
