Asea Aktiebolag

Salomon Liberman

Leif Eriksson

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.

Multiphase blocking circuitry for electrical power supply networks

In directional wave detector apparatus for electrical power line relay protection devices determining the direction to a fault, the current and voltage of the travelling waves generated by a fault point are combined at a measuring point and the sign of the combined signal is determined. A tripping or blocking signal is emitted depending on whether the sign of the combined signal indicates that the fault lies within or outside the range protection of the relay protection device.

Directional wave detector apparatus

In circuitry for generating tripping and blocking signals for the protection of electrical components in an electrical power supply network as a result of the occurrence of faults therein, respective tripping and blocking outputs for each phase of an electrical power supply network are generated such that double or triple pole tripping is prevented unless the presence of an actual second tripping signal is detected subsequent to the detection of a first tripping signal. The respective tripping signals and blocking signals for each phase of the electrical power supply network are generated in dependence on whether the fault lies ahead or behind the electrical component to be protected, respectively, in response to measurement of the voltage and current associated with transient waves generated by faults in each electrical power supply network phase. The presence of a tripping signal resulting from the occurrence of a single phase fault, and the presence of a second tripping signal resulting from the occurrence of a fault in another phase are detected. The functional level of detecting the second tripping signal is modified or adjusted upon detection of the first tripping signal.

Multiphase fault protection circuitry with variable functional level

Circuitry for generating tripping and blocking signals for the protection of electrical components included in electrical power supply networks as a result of the occurrence of faults therein provides multiphase pole tripping in the event that, after a single pole tripping has been executed, a new single phase fault occurs in any of the remaining phases of the electrical power supply network. Respective tripping and blocking signals are generated for each phase of the electrical power supply network in dependence on whether the fault lies ahead or behind the electrical component to be protected, respectively, in response to measurement of the voltae and current associated with transient waves generated by faults associated with each electrical power supply network phase. Multiphase pole tripping signals are generated by undervoltage detector logic circuitry responsive to the generation of the tripping signals upon the occurrence of a single phase fault, and the sensing of an undervoltage in another phase of the electrical power supply network before reclosing of the faulty phase.

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Ra'anana, Israel

Salomon Liberman