Systems, methods, techniques and apparatuses of ground fault protection are disclosed. One exemplary embodiment is a power switch being structured to receive a load current from a power source at a source-side and selectively output the load current from a load-side to a load; a first voltage measuring device structured to measure a first voltage of the source-side while the power switch is conducting the load current; a second voltage measuring device structured to measure a second voltage of the load-side while the first voltage measuring device is measuring the first voltage; and a controller structured to determine a source-side-to-ground voltage based on the first voltage, determine a load-side-to-ground voltage based on the second voltage, determine a ground fault is occurring, and determine a direction of the ground fault relative to the power switch by comparing the source-side-to-ground voltage and the load-side-to-ground voltage.

A method and circuit for determining and extinguishing electrical faults includes a power supply, and electrical load, a controller module, and electrical sensors, and when the controller module does not extinguish the electrical fault, another switch blows a fuse.

A method for operating an electric gardening and/or forestry apparatus system having an accumulator, a gardening and/or forestry apparatus with an electric motor, and a protective electronic circuit including inputs which are connected to the accumulator, outputs which are connected to the gardening and/or forestry apparatus, and a switching element which is disposed in a power path between one of the inputs and one of the outputs. The method turns on the switching element to a first conductive condition, measures an electric current through the power path, turns off the switching element to a second conductive condition, if the measured electric current exceeds a predetermined current limit value, measures an electric output voltage between the outputs, and either again turns on the switching element to the first conductive condition, if the measured electric output voltage reaches and/or exceeds a predetermined voltage limit value, or outputs an error signal, if the measured electric output voltage is below the predetermined voltage limit value.

A method for detecting fault direction of a transmission line of an AC power system and a control system using the same. The method includes sampling current values and voltage values at one end of the transmission line for a series of time points; computing instantaneous voltage values at compensated point on the transmission line from the current value samples and the voltage value samples based on a time domain lumped parameter differential equation for the transmission line for the series of time points; recording the current value samples and the computed instantaneous voltage values at the compensated point; computing at least one voltage fault component each using the recorded computed instantaneous voltage values for at least the at least two of the series of time points; identifying the fault direction in consideration of the at least one computed voltage fault component and the at least one computed current fault component; and generating a fault direction signal indicating the identified fault direction. Where a fault directional element is designed using the voltage fault components at the compensated point, it will work well for the AC power system with strong power source.

A method, control system and protective relay are provided for detecting faulted phases of transmission lines in an AC power system. The method includes sampling electric signals at one end of the transmission lines at a series of time points; computing instantaneous voltage values of electric signals at compensated points on the transmission lines from the values of the sampled electric signals based on a time domain lumped parameter differential equation for the transmission lines for the series of time points; recording the computed instantaneous voltage values of the electric signals; computing fault component or sudden-change of the instantaneous voltage values of the electrical signals; detecting the faulted phases or fault types by comparing the calculated fault component of the instantaneous voltage values at the preset compensated points; and generating signals indicating the faulted phases of fault types.

The present invention relates to a circuit (100) for breaking alternating current, the circuit (100) comprising: an input (102) arranged to receive an alternating current (AC); an output (104) arranged to provide the alternating current (AC) to at least one electrical load (200n); at least one controllable switch (106; 108) coupled between the input (102) and the output (104); an impedance network (Z) coupled between the input (102) and the output (104); a controller (110) coupled to a reference ground (112) common to the controller (110) and the at least one controllable switch (106; 108), wherein the controller (110) is arranged to measure at least one measuring voltage (V1; V2) between a node of the impedance network (Z) and the reference ground (112) and to control the at least one controllable switch (106; 108), so as to control the breaking of the alternating current (AC) provided to the at least one electrical load (200n), based on the value of the measured at least one measuring voltage (V1; V2).

The present invention relates to a circuit and an arrangement for breaking alternating current, the circuit comprising: an input arranged to receive an alternating current (AC); an output arranged to provide the alternating current (AC) to at least one electrical load; at least one controllable switch coupled between the input and the output; an impedance network (Z) coupled between the input and the output; and a transistor network (TN) comprising at least one transistor (T.sub.TN1; T.sub.TN2), the transistor network (TN) being arranged to control the at least one controllable switch, so as to control the breaking of the alternating current (AC) provided to the at least one electrical load, based on a value of at least one voltage (V1; V2) of at least one node of the impedance network (Z).

The redundant power supply device includes a power output port, a converter, a comparator unit and an output protection switch. The output protection switch is electrically connected between an output terminal of the converter and the power output port, and the comparator unit compares the voltage across the output protection switch and controls the output protection switch accordingly. The redundant power supply device has a control module that performs a protection control method. When the voltage of the power output port is higher than a preset voltage value and the output current is lower than a preset current value, the control module outputs a short turn-off signal to the enable terminal of the comparator unit, preventing the comparator unit from failing to perform the output protection as designed due to external abnormal slow rising voltage, and ensuring the redundant power supply unit operates normally.

An active limiting switch includes a comparator and a power switch. The comparator is configured to compare a reference voltage with a sense voltage. The sense voltage is representative of a proportional approximation to power in a load being driven by a battery. The power switch is configured to be, in response to the reference voltage being less than the sense voltage, in an open state. The power switch is also configured to be, in response to the reference voltage being greater than the sense voltage, in a closed state creating a closed circuit between the battery and the load allowing the battery to provide a first amount of power to the load.

Method for the directional determination of an earth fault in an electric power distribution network, characterised in that it comprises the steps of: Determining (E2) a residual current phasor and a residual voltage phasor, Determining (E3) an active current, Comparing (E7) the residual voltage phasor module with a threshold (SVR), and as long as the residual voltage phasor module remains higher than the threshold (SVR) or a fraction of the threshold (SVR), and for a predetermined number of iterations: Determining (E9, E12) the integral of the active current and of its sign, Determining the number of times when the residual current phasor module is greater than a predetermined threshold (SIR), during the predetermined number of iterations, If the residual current phasor module is greater than the predetermined threshold (SIR) at least one time, during the predetermined number of iterations, Determining (E16) the location upstream or downstream of the fault according to the number of times when the sign of the integral of the active current was positive or negative during the predetermined number of iterations.