| 摘要 |
<p>1,120,460. Protective systems; converting, MOSKOVSKY ENERGETICHESKY INSTITUT. 21 Dec., 1965, No. 54190/65. Headings H2F and H2K. [Also in Division H3] A protective arrangement for a D.C. transmission line comprises a voltage divider 10 connected to the protected line, a differentiating unit 1 connected to the voltage divider and an actuating unit 2 connected to the unit 1 which comprises two transformers 3, 4 interconnected by a capacitor 7. When the line voltage falls due to a short circuit condition, the differential unit produces a single voltage pulse which is approximately proportional to the third derivative of the line voltage and enables the arrangement to distinguish between a short circuit on the line and a short circuit in an inverter. Diodes 5, 6 and 9 in the differentiating unit increase the sensitivity of the arrangement. The voltage pulse is applied to the base of a normally non-conducting transistor 11 in a monostable circuit. This circuit includes a normally conducting transistor 12 having its collector connected to the base of the transistor 11 through a resistor 16 and a choke 17 to prevent the input voltage being shorted out by the transistor 12. A relay 24 is connected to the collector circuit of the transistor 11 and a time delay is provided by a resistor 22 and capacitor 21. In a modified arrangement, Fig. 2 (not shown), the second transformer has a rectangular hysteresis loop core and a magnetizing winding.</p> |
