Multiphase blocking circuitry for electrical power supply networks

Abstract

In circuitry for generating tripping and blocking signals for the protection of electrical power supply network components as a result of the occurrence of faults, the blocking signals are selected from each phase of the electrical power supply network to prevent tripping in each phase for faults occurring behind the protected component. A sequence detector includes a partial detector for each phase of the electrical power supply network and includes logic circuitry responsive to respective tripping and blocking signals generated for each phase of the electrical power supply network in dependence on whether the fault lies ahead or behind the protected electrical component, respectively. Each logic circuit includes a gate and a delay circuit responsive to the output of the gate. The output of the delay circuit in the tripping logic circuit is input to the gate in the blocking logic circuit and vice-versa. Each blocking logic circuit includes an additional gate for receiving a blocking input from another protection circuit which is common to all the partial detectors for passing blocking signals and blocking tripping signals.