A disconnector device including an isolator connected between a first terminal and to a second terminal, and a sleeve positioned around the isolator and moveable between an un-extended position prior to the isolator operating and an extended position after the isolator operates, the sleeve being configured to trap debris produced by operation of the isolator.

A momentary circuit interrupter in series connection with a mechanical switch to provide protection against short circuit faults in a DC power circuit. The momentary circuit interrupter injects a transient voltage pulse via a pulse transformer to reduce a DC fault current to near zero in a DC circuit branch, thus allowing the mechanical switch to disconnect the faulty branch under a near zero-current condition. The power electronic circuit on the primary side of the transformer controls the discharge of a plurality of pre-charged capacitors to generate the transient voltage pulse during the fault interruption process, but otherwise does not incur any power loss during normal operation. The secondary winding of the pulse transformer conducts the main DC current, and is highly conductive to minimize the conduction power loss. The invention provides ultrafast response to a short circuit fault (even faster than solid-state circuit breakers and much faster than hybrid circuit breakers), significantly reduced overcurrent stress in the power system, and/or ultralow conduction power losses.

A DC electrical network comprising DC terminals operatively connectable to a converter; and DC transmission paths arranged to interconnect the DC terminals, and including a DC power transmission medium and a switching apparatus. The DC network further including: an active power electronic device connected in at the DC transmission paths, the active power electronic device; a detector configured to detect faults in the DC transmission paths; and a control unit programmed to operate the active power electronic device to vary an apparent impedance of a faulty DC transmission path to force a current flowing in the faulty DC transmission path to reduce to a target current level, and operate the switching apparatus to block current from flowing in the faulty DC transmission path when the current flowing in the faulty corresponding DC transmission path is reduced to the target current level.

A solid-state zero current switching circuit breaker is configured to interrupt current flow between a voltage input and a load. The solid-state zero current switching circuit breaker includes at least one resonant capacitor cell having an input configured to receive a source voltage and an output configured to deliver drive current to the load. The resonant capacitor cell is configured to selectively limit the drive current to the output based on a variable voltage. The solid-state zero current switching circuit breaker further includes at least one voltage clamping switch configured to detect a short-circuit fault or an overload condition. The voltage clamping switch adjusts the variable voltage in response to detecting the short-circuit fault condition or the overload condition such that the resonant capacitor cell limits the drive current.

A fault clearing circuitry provided for connecting to at least one electrical line transmitting power includes: an electrical energy storage; at least one controllable switch connectable between the electrical energy storage and at least one electric line; and a control circuit for monitoring the at least one electric line for a fault and to close the at least one controllable switch if a fault is detected. The electrical energy storage stores an amount of electrical energy dimensioned to be sufficient for releasing one or more circuit breakers or clearing one or more fuses in the at least one electrical line in order to clear the fault. The control circuit closes the at least one controllable switch if a fault is detected such that a discharging of the electrical energy stored in the electrical energy storage is incurred injecting a current pulse in the at least one electrical line.

A method for synchronizing opening of a circuit breaker is presented. The circuit breaker is arranged to interrupt a current to an inductive load. The method is performed in a control device (2) and comprises measuring (S100) a reference signal as a function of time for a circuit breaker (1) connected to an inductive load (5), obtaining (S110) an indication of a power factor of the inductive load through the circuit breaker, determining (S120) an arcing time for opening of the circuit breaker, the arcing time being dependent on the obtained indication of a power factor, predicting (S130) a zero crossing of a current through the circuit breaker based on the measured reference signal, and providing (S140) contact separation of a contact pair of the circuit breaker at a point of time before the predicted zero crossing, the point of time being determined by the determined arcing time and the predicted zero crossing. A control device, a circuit breaker arrangement, and a computer program for synchronizing opening of a circuit breaker are also presented.

A protection IC protects an external load connected to mains supply lines from dangerous or undesired conditions such as overvoltage, undervoltage, and overcurrent, by disconnecting the external load for at least the duration of such a condition. The IC has a range detector, a zero-crossing detector, a control unit, a switch driver, and a dummy DAC. The range detector senses the presence of an unwanted condition. The control unit then waits for a zero crossing, upon which it disconnects the load. A lockout timer may introduce a minimum wait time before reconnecting the load. To prevent instabilities around the switching points, hysteresis in the window thresholds prevents impact from noise. The dummy DAC regulates a dummy current that linearizes the IC's current consumption around the switching points to prevent instabilities caused by positive feedback in non-linear transitions.

First and second output transistors are connected in series between a power supply terminal and a ground terminal through an output node connected to an output terminal. An output transistor control circuit is arranged corresponding to at least one of the first and second output transistors and is configured to input a voltage at the output terminal to the gate of the first output transistor at a time of occurrence of disconnection of the power supply terminal and input the same to the gate of the second output transistor at a time of occurrence of disconnection of the ground terminal. The first output transistor has a conductivity type to turn off when a power supply voltage is input to the gate, and the second output transistor has a conductivity type to turn off when a ground voltage is input to the gate.

A hybrid circuit interrupter can be used for medium voltage direct current applications, among other applications. The circuit breaker includes a vacuum circuit interrupter and an electronic power interrupter that are electrically connected in parallel. The vacuum circuit interrupter is normally closed and the electronic power interrupter is normally off, so that current passes through the vacuum circuit interrupter in a non-interrupt mode. When an interrupt condition is detected, the electronic interrupter will turn on, and current will pass through the electronic interrupter as the vacuum interrupter is opened. A current injector may draw current from the vacuum interrupter to the electronic power interrupter. An isolation switch may maintain the system in a non-conducting state when interruption is complete.

Overcurrent protection of an electrically powered, motorized device, such as a power tool, wherein the tool includes a tool housing, an output assembly, a trigger, an electrical safety device, a motor, an indicator, a controller, and a power source. The electrical safety device, for example a fuse, is disposed in series with a power connection from the power source to the controller. The controller measures current passing through the electrical safety device in time intervals when the trigger is actuated. The controller determines accumulated thermal energy passing through the electrical safety device, and compares the accumulated thermal energy to a threshold. If the accumulated thermal energy exceeds the threshold, the controller ceases or discontinues to allow power to be provided to the motor from the power source, thereby shutting off the motor. The controller may also activate the indicator to indicate a fault to the user.