Arrangement for determining ground faults and for the protection of the conductors in a three-phase mains with a grounded zero point

摘要

1,233,245. Protective arrangements. COMPAGNIE DES COMPTEURS. 6 Sept., 1968 [20 Sept., 1967], No. 42516/68. Addition to 1,199,200. Heading H2K. To ensure that the distance protective arrangement of parent Specification does not respond incorrectly to an earth fault outside a protected section, a further amplifier 8 is connected to a NOT circuit and energized by a voltage derived from and in phase with the zero sequence current Ir. The NOT circuit is connected to the AND and NOR circuits 4, 5 and the amplifier 8 is connected by a transformer 25 across a resistor 26 in series with the zero sequence replica impedance 17. The resistor 26 may be omitted or replaced by anti-parallel diodes.