Bbc Brown, Boveri & Company, Limited

Brown, Boveri & Co., Ag

Venkat Narayan

Jacques Boniger

The voltage-to-ground or neutral of one phase conductor of a three-phase line is compared with the mesh or interphase voltage of the other two phases on an amplitude basis and the comparison result is used to trigger a threshold switch if the former is much smaller than the latter. The threshold switch may be connected to the selector of an excitation system of a network protection assembly or a nonselective excitation system may utilize the outputs of the threshold switches for each of the three comparisons, in order to produce selective triggering of a network protection assembly.

Method and apparatus for fault detection in a three-phase electric

A distance protection device and an overcurrent protection device are coupled to a circuit breaker means of the network being protected by means of a logic system which enables the circuit breaker means to be activated by one of the two protection devices as a function of at least one signal derived from the network being protected, the at least one signal being also used in determining faults in at least one of the two protection devices. The logic system is activated by, for example, the at least one signal falling below a set minimum value. The result is the automatic change of function between distance and overcurrent protection.

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Spreitenbach, Switzerland

Venkat Narayan