| 摘要 |
1,232,641. Protective systems. COMPAGNIE DES COMPTEURS. 28 May, 1968 [1 June, 1967; 20 March, 1968], No. 25518/68. Heading H2K. A distance protective arrangement for a three-phase transmission line has for each phase devices 10, 12, 13 deriving signals proportional to the voltage to earth, the line current and the derivative of the line current, and switching or counting means 21, 21a, 21b controlled by a timer 6 to periodically apply the signals to a computer 7 which functions to add two products, dependent on the inductive and resistive voltage drops, for each phase, the resulting straight line characteristics for the three phases passing through a common point on an impedance diagram, the position of the point being representative of the distance to a fault. The computer 7 is programmed to repeatedly perform the calculations necessary to determine both interphase and phase/earth faults within a protected section, the underlying theory being given in the Specification. In the arrangement disclosed, the devices providing the signals are a capacitive voltage divider 10, a shunt 12 and an air-cored transformer 13. The transmission of the signals from the components 12, 13 at high potential to the equipment at earth potential may be effected by radio, or as shown by light transmission. Thus the signals are applied to converters 11, 11a, 11b which provide output signals with frequencies dependent on the magnitude of the respective input signal, the output signals from converters 11a, 11b being applied to light emitting diodes in transmitters 14a, 14b connected by glass-fibre light guides to photo-diodes in receivers 15a, 15b. The signals from the converter 11 and receivers 15a, 15b are frequency multiplied at 16, 16a, 16b and mixed at 20, 20a, 20b with frequency multiplied signals from a reference generator 17, the filtered outputs from the mixers 20, 20a, 20b being repeatedly counted by counters 21, 21a, 21b under the control of the clock timer 6 for application to the computer 7. Various modifications and circuits for the components are described. |
