Systems and methods may be used to determine fault types and/or directions even during a loss of potential by receiving, at one or more processors, an indication of a pre-fault power flow direction for a power delivery system. The one or more processors then determine a fault direction during a fault for the power delivery system using current vector angles and the pre-fault power flow direction.

A method that tests a differential protection device having a first and a second differential protection chain includes: a step of controlling the flow of a test signal for a duration smaller than a no-trip time, and steps of determining the state of the two differential protection chains after the flow of a test signal, of monitoring the conformity of the evolution of the protection chains, and of determining the state of the test. The differential protection device includes two differential protection chains and controls the flow of a test current for a duration smaller than a no-trip time. It includes modules for monitoring the evolution of the protection chains and determining the state of the test in order to control the opening of an electrical unit if the test is good. The device can be included in the electrical unit.

An electric power delivery system may be protected upon occurrence of a fault condition by the systems and methods disclosed herein by detecting the fault condition and signaling a protective action before the overcurrent condition reaches the protective equipment. The protective action may be an opening of a circuit breaker or engagement of a fault current limiter. The overcurrent condition may be a non-steady-state condition. The fault may be detected using traveling wave or incremental quantity techniques.

The present disclosure relates to generating reference signals for distance and directional elements in power systems. For example, an intelligent electronic device (IED) may receive A-phase, B-phase, and C-phase electrical measurements of a power system. The IED may transform the A-phase, B-phase, and C-phase measurements to a d-component, a q-component, and a 0-component. The IED may include an adaptive notch filter that reduces or eliminates a double frequency component that may be present when step changes of frequency and/or amplitude occur and/or when the A-phase, B-phase, and C-phase measurements have different amplitudes. By reducing the double frequency component, the IED may generate a more accurate which may allow for more accurately tracking changes to the polarizing source. Further, the IED may separately add inertia to the estimated angular frequency used in generating a reference signal.

A semiconductor current cutoff device, including a circuit having a first branch including an energy absorbing member and a second branch including a semiconductor switch, the semiconductor switch being connected in parallel with the first branch, a current measuring means for measuring the intensity of the electrical current at a connection terminal of the device, and an electronic control unit for controlling the semiconductor switch, programmed to control the opening of the semiconductor switch when the current intensity measured by the current measurement means reaches a predetermined value, the device then switching from a conductive state to a cutoff state, the circuit including a third branch including a mechanical switch, and the electrical control unit being programmed so that the semiconductor switch is closed before the mechanical switch.

This application relates to methods and apparatus for handling a fault associated with a voltage source converter (VSC) for exchanging electrical power between an AC system (101, 102) and a DC system (106-1, 106-2). The VSC (104) is connected to the AC system via an interface apparatus, comprising a transformer (107) with a set of primary windings (202) for coupling to a plurality of AC phases (A, B, C) of the AC system. In embodiments of the disclosure the set of primary windings having a neutral point (N) and the interface apparatus includes a fault module (301) having an energy storage element (302) connected in parallel with a resistive element (303) between the neutral point of the set of primary windings and a reference voltage, such as ground. The fault module does not interfere with normal operation but in the event of a phase-to-ground fault on the secondary side of the transformer, can induce earlier zero-crossing in the AC phases than otherwise would be the case, thus allowing AC breaker (108) to open with a reduced arcing time.

An electrical apparatus configured to electrically connect to a multi-phase alternating current (AC) electrical power distribution network includes: an input electrical network including: a plurality of input nodes, each configured to electrically connect to one phase of the multi-phase AC electrical power distribution network; at least one non-linear electronic component electrically connected to the input electrical network; an impedance network electrically connected between the input electrical network and ground; and a control system configured to: access a voltage signal that represents a voltage over time at the input electrical network; determine a frequency content of the voltage signal; determine a property of the frequency content; and determine whether an input current performance condition exists in the electrical apparatus based the property of the frequency content.

A vehicle drive control device that controls a vehicle drive device in which a first engagement device, a rotating electrical machine, and a second engagement device are provided in this order from an input side in a mechanical power transmission path connecting an input to an output, the input being drive-coupled to an internal combustion engine serving as a vehicle drive power source, and the output being drive-coupled to wheels, wherein each of the first engagement device and the second engagement device can be changed between an engaged state in which drive power is transmitted and a disengaged state in which drive power is not transmitted, the vehicle control device including an electronic control unit.

A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120, and a third phase lagging the first phase by 240, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 in a time range from 60 before a peak of the phase to 90 after the peak.

A surge suppression circuit is used in a rotating electrical machine system including a switching circuit composed of a plurality of switching elements and a rotating electrical machine connected thereto via an electrically conducting path comprising a plurality of electrically conductive bodies. The surge suppression circuit suppresses surge voltage generated in a plurality of connecting lines connecting the plurality of electrically conductive bodies to windings of plural phases of the rotating electrical machine. The surge suppression circuit includes a plurality of upper diodes with anodes respectively connected to the plurality of connection lines, a plurality of lower diodes with cathodes respectively connected to the plurality of connection lines, an upper line connected to respective cathodes of the plurality of upper diodes, a lower line connected to respective anodes of the plurality of lower diodes, and a voltage holding circuit connected between the upper line and the lower line. The voltage holding circuit includes a charging unit to store electric charge by the surge voltage and a discharge unit to discharge the electric charge stored in the charging unit.