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.

In a protective relay device, a current differential relay computation unit determines whether or not a fault has occurred within a protected section based on an operating quantity and a restraint quantity. A disconnection detection unit computes a first amount of difference by subtracting the operating quantity a certain time period ago from the operating quantity at a present point in time, computes a second amount of difference by subtracting the restraint quantity the certain time period ago from the restraint quantity at the present point in time, and determines that a disconnection has occurred at one of first and second current transformers when a first determination condition that an absolute value of a sum of the first amount of difference and the second amount of difference is equal to or smaller than a first set value is satisfied.

An integrated circuit-based nano-relay, comprising: an integrated circuit system of the nano-relay constructed according to an integrated circuit module built from a combinational logic circuit. An integrated power data processing algorithm is called by means of the integrated circuit module to perform signal processing on an input power signal, and power service data is output, that is, an integrated circuit is mainly constructed by means of the combinational logic circuit, the protection logic of the nano-relay is achieved by means of a hardware circuit module, and a response speed of the relay is improved.

An over-current protection apparatus constituted of: a transistor disposed on a substrate; a first thermal sense device arranged to sense a temperature reflective of a junction temperature of the transistor; a second thermal sense device arranged to sense a temperature reflective of a temperature of a casing surrounding the substrate; and a control circuitry, arranged to alternately: responsive to the sensed temperature by the first thermal sense device and the sensed temperature of the second thermal sense device being indicative that the temperature difference between the transistor junction and the substrate casing is greater than a predetermined value, switch off the transistor; and responsive to the sensed temperature by the first thermal sense device and the sensed temperature by the second thermal sense device being indicative that the temperature difference between the transistor junction and the substrate casing is not greater than the predetermined value, switch on the transistor.

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.

A photovoltaic power generation system includes a plurality of photovoltaic arrays, a plurality of shutdown units and an inverter. The shutdown unit is adjacent to the corresponding photovoltaic array, connected in parallel with the corresponding photovoltaic array, and electrically connected to the inverter via high voltage wires; the photovoltaic power generation system further includes a control unit configured to receive a detection signal indicating a state of the AC side of the inverter, monitor whether the AC side of the inverter is in a power-off state according to the detection signal, and generate a first power-off signal when the AC side of the inverter is in the power-off state; and the shutdown units are configured to receive the first power-off signal, and stop a power transmission from the photovoltaic arrays to the inverter according to the first power-off signal.

A device and method for fuse protection of a line includes at least two sensors for sensing a corresponding electric variable in a first location and a second location along a conductor line, and for outputting a corresponding first value and second value of the electric variable at the first and second locations, respectively. An evaluation unit evaluates the generated first and second values in order to generate an evaluation result. The evaluation unit controls, based on the evaluation result, an isolating element to cause the isolating element to interrupt a current flow in the conductor line.

Disclosed are a photovoltaic system and its rapid shutdown method. The photovoltaic system includes a photovoltaic array including a photovoltaic array panel and a shutdown device, a junction box and an inverter, the shutdown device is electrically connected to the photovoltaic array panel and is connected to the inverter; the photovoltaic system further includes a shutdown device controller, which is coupled to the high voltage wires, and is configured for receiving a first detection signal reflecting a state of the AC side of the inverter, determining whether the AC side of the inverter is in a power-off state, outputting a first power-off signal when the AC side of the inverter is in the power-off state, and transferring the first power-off signal to the shutdown device ; and the shutdown device receives the first power-off signal and prohibits the electric energy from transferring to the inverter.

A current consumed by an electric consumer is sampled as a first sampled current, and a main current sensor samples a current provided by an electric supply system as a second sampled current. A fault current detector detects a fault current between the electric supply system and the electric consumer, based on a non-zero difference between the first sampled current and the second sampled current and, in response, generates a circuit break signal. A residual current device receives the circuit break signal and, in response, to breaks a circuit between electric supply system and the electric consumer.

A method in a power system which includes a protected unit, such as a transmission line, adapted to convey power from a first position in the protected unit to a second position in the protected unit, or vice versa, via a plurality of conductors. A first travelling wave differential current (ITWdiff) is determined based on a comparison between a determined first travelling wave current or a second travelling wave current in first and second positions and an estimation of the first travelling wave current or the second travelling wave current, respectively. The estimation is carried out using a propagation function which takes into account any distortion, attenuation and/or delay of the waveform of a wave due to propagation of the wave in the protected unit. A second or normalized travelling wave differential current (ITWdiff) is determined by means of, based on the propagation function, adjusting at least one of magnitude and phase of the first travelling wave differential current such that all modes attain equal or increasingly equal modal characteristics. The method may facilitate or enable mitigating or even eliminating any false differential current in elements of a travelling wave differential current vector which correspond to healthy conductors, caused by coupling effects between conductors.