A method of operating a protection device arranged between an electrical three-phase power source and at least one electric motor, the method including for each phase of the power source, acquiring over time a corresponding phase current flowing from the power source to the at least one electric motor; based on the acquired phase currents, detecting in which current stage each electric motor is, among an initial stage, an intermediate stage successive to the initial stage and a steady-state stage successive to the intermediate stage; calculating an active threshold value depending on the detected stage of each electric motor, the active threshold value during the intermediate stage following a predetermined decreasing function over time.

Systems and methods are provided for detecting and compensating for loss of a phase of a three-phase power source, elements of the system including: a sensing unit, which measures current and voltage levels of each phase of the three-phase power source; a switching unit having three primary relays and three backup relays; and a microcontroller, configured to receive measurements from the sensing unit, to determine from the measurements a lost phase and a less-loaded phase of the two remaining phases, and responsively to activate the switching unit to disconnect the lost phase and to connect the less loaded phase to provide backup power in place of the lost phase.

A system for detecting overloads of a motor comprises a motor configured to receive power via a lead line, a first sensing device configured to sense a temperature of a motor, and a second sensing device electrically coupled to the motor and configured to detect a target current of the motor and trigger a contact of the lead line associated with second sensing device when the target current equals or exceeds a trip value.

The present disclosure relates to detection of faults in an electric power system. In one embodiment, a time-domain traveling wave directional subsystem is configured to receive a plurality of current traveling wave and a plurality of voltage traveling wave time-domain representations based on electrical conditions in the electric power delivery system. The plurality of current and voltage traveling wave time-domain representations may be compared to respective minimum thresholds. An integral may be generated based on a product of the plurality of current and voltage traveling wave time-domain representations when the current and voltage traveling wave time-domain representations exceed the minimum thresholds. A sign of the integral may reflect whether the fault is in the forward or reverse direction. A fault detector subsystem configured to declare the fault when the sign reflects that the fault is in the forward direction and the integral exceeds a security margin.

The present invention provides a method for current for fault identification in a transmission line and an apparatus thereof. The method comprises the following steps: measuring the real-time values of the currents and the voltages of the other unbroken healthy phase conductors when a single-phase fault occurs; calculating the inductive voltage and the capacitive coupling voltage according to the measured currents and voltages respectively; comparing the capacitive coupling voltage with the inductive voltage multiplied by a factor, in which the multiplication result is used as a self-adjusted threshold based on the real time load condition of the transmission line; and identifying the fault type based on the maximum of the capacitive coupling voltage and the multiplication.

A circuit for detecting loss of phase in three-phase power systems. The circuit includes a current sensor and a microprocessor. The current sensors are coupled to respective phases of a three-phase power source configured to supply power to a load. The microprocessor is coupled to the current sensors to process current measurements and detect loss of phase in the three-phase power source.

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.

A motor control system for selectively controlling power from a power source to a load is provided. The motor control system includes at least one PCB structure and a plurality of protection and control components mounted onto the at least one PCB structure so as to be electrically coupled therewith. The plurality of protection and control components includes a power converter operable to provide a controlled output power to the load, a plurality of switching devices operable to selectively control power flow from the power source into the power converter and to bypass the power converter, and one or more protection devices configured to selectively interrupt current flow from the power source to the power converter during a fault condition. The motor control system also includes a housing enclosing the at least one PCB structure and the plurality of protection and control components.

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.

The present disclosure relates to detection of faults in an electric power system. In one embodiment, a time-domain traveling wave differential subsystem is configured to determine at a first terminal a first index between an arrival maximum of a traveling wave generated by a fault at the first terminal and an exit maximum of the traveling wave. The traveling wave subsystem also determines a second index between an arrival maximum of the traveling wave at the second terminal and an exit maximum of the traveling wave. An operating quantity and a restraint quantity may be determined based on a magnitude of the representations of electrical conditions in the first index and the second index. A fault may be declared based on a comparison of the operating quantity and the restraint quantity. A protective action subsystem may be configured to implement a protective action based on the declaration of the fault.