| 摘要 |
1,192,640. Distance protective arrangements. ENGLISH ELECTRIC CO. Ltd. 20 Sept., 1968 [22 Sept., 1967], No. 43335/67. Heading H2K. In a distance relay arrangement the derivative (di/dt) of a current derived from the current of a protected system is compared with the largest instantaneous value of two rectified voltages as the current passes through zero, one voltage being phase shifted from the other and both being derived from the system voltage, operation being effected when the ratio of the compared quantities exceeds a predetermined value. The arrangement may comprise a current transformer 13 having primary windings energized by a phase current IR and the residual current IO. The output from the transformer is applied to the differentiator circuit 6. This circuit comprises two networks operative on the opposing half cycles to provide a differentiated pulse at each passage of the current through zero. These pulses are applied between a junction 30 in summing network 44, 45, 46 and a junction 29 between bridge rectifiers 31, 32 forming a switching circuit which is gated by differentiated pulses derived from the voltage ER of the protected systems. The rectified voltages are obtained from a voltage transformer secondary winding 49, resistors 50 ... 52 and a rectifier 48, and from a secondary winding 57, a phaseshifting circuit 58 . . . 60 and a rectifier 55. The rectifiers 48, 55 are connected in series across the resistor 46 so that the voltage across the resistor is that which has the largest instantaneous value. A polarity sensitive device 11 responds to the sum of the voltages across the resistors 44... 46 to effect the tripping of a circuitbreaker. A somewhat similar circuit arrangement, Fig. 7 (not shown) may be used as a starting unit and control the opening of a time switch 54 to extend the reach of the relay arrangement. |
