A power system includes: a self-commutated power converter including a first arm and a second arm, each including switching elements; a first circuit breaker configured to interrupt a current flowing through a power transmission line provided between a first bus and a second bus; a first circuit breaker control unit configured to control the first circuit breaker; a converter control unit configured to stop the switching elements based on a first arm current value and a second arm current value; and a setting unit configured to set a voltage value of an AC voltage output from the power converter such that when a fault occurs in the power transmission line, the first circuit breaker is opened while the switching elements are not stopped. The converter control unit is configured to operate the switching elements such that an AC voltage with the set voltage value is output.

A current differential relay apparatus includes a first relay and a second relay. The first relay calculates a first differential current and a first suppression current, using a first current and a second current, and performs a ratio differential relay operation based on the first differential current and the first suppression current. The second relay calculates a maximum of results of add operations of the first current and the second current as a second differential current, calculates an add operation of the maximum of the first current and a maximum of the second current as a second suppression current, and performs a ratio differential relay operation based on the second differential current and the second suppression current. The current differential relay apparatus includes an output controller that outputs an operation signal based on results of operations performed by the first and second relays.

Provided is a determination method of differential protection suitable for an electricity transmission line with multi-terminal T-connection. The determination method includes: sampling and calculating all phase currents, and calculating a maximum fault component current Δİ.sub.max in phase current amplitudes of each phase current, a differential current I.sub.cd in the each phase current, a resistive current I.sub.res in the each phase current and a vector sum Δİ.sub.Σ of fault component currents except Δİ.sub.max in the phase current amplitudes of the each phase current; and comparing the maximum fault component current Δİ.sub.max in phase current amplitudes of each phase current and a threshold setting value I.sub.max0, determining a value of a resistive coefficient K corresponding to the phase current amplitudes of the each phase current according to a comparison result, and performing differential determination on the differential current I.sub.cd and the resistive current I.sub.res in phase current amplitudes of the each phase current according to a differential determination formula: if the differential current I.sub.cd of the target phase satisfies the above differential determination formula, it is determined that a fault occurs in an area of the target phase.

Provided is a determination method of differential protection suitable for an electricity transmission line with multi-terminal T-connection. The determination method includes: sampling and calculating all phase currents, and calculating a maximum fault component current Δİ.sub.max in phase current amplitudes of each phase current, a differential current I.sub.cd in the each phase current, a resistive current I.sub.res in the each phase current and a vector sum Δİ.sub.Σ of fault component currents except Δİ.sub.max in the phase current amplitudes of the each phase current; and comparing the maximum fault component current Δİ.sub.max in phase current amplitudes of each phase current and a threshold setting value I.sub.max0, determining a value of a resistive coefficient K corresponding to the phase current amplitudes of the each phase current according to a comparison result, and performing differential determination on the differential current I.sub.cd and the resistive current I.sub.res in phase current amplitudes of the each phase current according to a differential determination formula: if the differential current I.sub.cd of the target phase satisfies the above differential determination formula, it is determined that a fault occurs in an area of the target phase.

Disclosed are a household appliance, an apparatus and a method for detecting an arc fault in the household appliance. The apparatus includes: a grid current detecting unit, configured to detect a current from a power grid to the household appliance so as to generate a first current detecting signal; a filter protecting unit, configured to perform an attenuation processing on an arc signal in the power grid; a load current detecting unit, configured to detect an actual running current in a load of the household appliance so as to generate a second current detecting signal; and a control unit connected to the grid current detecting unit and the load current detecting unit respectively, and configured to identify and compare the first current detecting signal and second current detecting signal so as to determine a source of the arc fault.

An electrical protection system arranged to detect and isolate faults either in a electrical power distribution. The system comprises at least a first busbar and a second busbar in electrical communication with each other through s powerline having a first end electrically coupled to the first busbar by a first circuit breaker and a second end connected to the second busbar by a second circuit breaker. It is connected to the at least two busbars, and configured to simultaneously collect/determine a first electrical quantity at each of the at least two busbars and compare the collected/determined electrical quantity to a second. When the first electrical quantity value less than the second quantity value, the system causes the first and second circuit breakers to open so as to decouple the electrical connection between first and second busbars. The system 100 detects and isolates fault efficiently while using voltage measurements.

A current differential relay apparatus includes a first relay and a second relay. The first relay calculates a first differential current and a first suppression current, using a first current and a second current, and performs a ratio differential relay operation based on the first differential current and the first suppression current. The second relay calculates a maximum of results of add operations of the first current and the second current as a second differential current, calculates an add operation of the maximum of the first current and a maximum of the second current as a second suppression current, and performs a ratio differential relay operation based on the second differential current and the second suppression current. The current differential relay apparatus includes an output controller that outputs an operation signal based on results of operations performed by the first and second relays.

A method of identifying an arc fault in a wire operably connected between a controller and a load. The method includes operably connecting a sense wire to the wire in close proximity to a load supplied by the controller via the wire, measuring a first voltage on the wire at the load via the sense wire, measuring a second voltage on the wire at an output interface of the controller and measuring a current in the first wire. The method also includes identifying any differences between the voltage on the wire measured at the load and the second voltage on the wire measured at the output interface, ascertaining any anomalies in the current measured in the wire, and correlating the differences between the first voltage and the second voltage with any anomalies in the current to identify an arc fault.

A current differential protection method for a self-adaptive half-wavelength line based on a time-difference method. Since an electrical distance of half-wavelength power transmission is long, after a fault occurs, there is an obvious time difference between the actuation times for protecting starting elements at two sides of a line. According to the principles of wave propagation, the position of a fault point can be determined by means of a difference between the actuation times for protecting the starting elements at the two sides of the line. By means of taking the fault point as a differential point, a current value at the differential point can be obtained according to a long line equation by means of the voltage and current at protection-mounted positions at the two sides of the line, and a differential current is then calculated.

A control method allows the control of an installation for transmitting electricity comprising a DC transmission network including a group of electricity transmission lines that are linked to one another. The method allows the opening of at least one N-1 safety system, for each safety system being opened, the contribution to the flow of current through the group of transmission lines, originating from the converter station associated with the safety system that is opened, is removed. Furthermore, the method also allows a search for the short-circuit fault in order to identify the faulty transmission line, and an operation, implemented after identification of the faulty transmission line by the search step, of isolating the faulty transmission line by opening the line circuit breakers of the faulty transmission line.