| 摘要 |
1,199,200. Protective arrangement. COMPAGNIE DES COMPTEURS. 6 Sept., 1967 [12 Sept., 1966], No. 40661/67. Heading H2K. A distance protective arrangement for a threephase system with an earthed neutral, comprises for each phase a series circuit consisting of the secondary winding of a transformer 21, 22 or 23 having a primary winding connecting the phase to earth, a replica impedance 14, 15 or 16 supplied by a current proportional to the phase current, and a replica impedance 17 supplied by the zero sequence current. These circuits are connected to amplifiers 1 . . . 3 which convert their input voltages to two-state logic output signals. These output signals are applied to an AND circuit 4 and a NOR circuit 5 and the output signals of these circuits are applied to an OR circuit 6 which is connected to a temporary storage circuit 7. This circuit 7 is connected to a tripping device (not shown). When a fault to earth occurs within the protected zone, the three voltages applied to the amplifiers 1, 2, 3 are simultaneously positive or negative during parts of a cycle. When the voltages are simultaneously positive the AND circuit produces a signal and when the voltages simultaneously negative the NOR circuit produces a signal. These signals are of short duration, but are converted by the circuit 7 into a steady tripping signal. A delay circuit may be provided between the circuits 6 and 7. |
