Abstract: A start-up method for reducing inrush current to a transformer when closing a switching device. The switching device includes three single-pole operated current interrupting means. The method includes monitoring a voltage. The method includes, for each of a sequence of iterations: at a same opening angle relative to a reference angle of the voltage, starting an opening sequence of the switching device; at a closing angle relative to the reference angle, which is shifted in relation to the closing angle of all other iterations in the sequence, starting a closing sequence of the switching device; and obtaining an indication of the overall inrush current resulting from the closing. The method includes selecting for future use with the opening angle, the closing angle of one of the iterations in which the overall inrush current is relatively low when compared with the other iterations of the sequence.

Abstract: A method of operating a switching device in a system. The method includes monitoring a voltage; operating the system at each of a plurality of system configurations; and, for each of the system configurations and a predetermined same opening angle relative to a reference angle of the monitored voltage, determining a suitable closing angle relative to the reference angle and storing information about the determined suitable closing angle in association with the system configuration in a database. The method then includes, determining a system configuration in the system; at the predetermined same opening angle, opening the switching device; from the database, obtaining a closing angle of the determined suitable closing angles, wherein the system configuration with which the obtained closing angle is associated in the database corresponds to the determined system configuration; and at the obtained closing angle, closing the switching device.

Abstract: An arc quenching device for a three-phase electrical switchgear. The device includes a first busbar, a second busbar and a third busbar, each of a respective phase of the three-phase switchgear. The device also includes a first piston and a second piston, each of an electrically conductive material. The device also includes at least one pyrotechnical actuator arranged with the first and second pistons to axially move each of the first and second pistons if the at least one pyrotechnical actuator is fired. The first and second pistons are arranged in relation to the first, second and third busbars such that said axial movement brings the first piston into contact with both the first busbar and the second busbar, and the second piston into contact with both the first busbar and the third busbar.

Abstract: An arc quenching device for a three-phase electrical switchgear. The device includes a first busbar, a second busbar and a third busbar, each of a respective phase of the three-phase switchgear. The device also includes at least one piston of an electrically conductive material and having a tapered shape, tapering towards its front end. The device also includes only one pyrotechnical actuator arranged to, when the pyrotechnical actuator is fired, axially move each of the at least one piston until all of the first, second and third busbars are short-circuited to each other via the at least one piston.

Abstract: The invention relates to a control unit for a medium voltage switching apparatus. The control unit is adapted to carry out a diagnostic method to check operating conditions of one or more components of said electric poles. The diagnostic method includes the following steps: basing on a selected ideal position curve, obtaining one or more first curves indicative of an ideal behaviour of said switching apparatus, during an opening manoeuvre or closing manoeuvre of the switching apparatus; basing on detection signals provided by a closed-loop control arrangement of said control unit, calculating one or more second curves indicative of an actual behaviour of said switching apparatus, during an opening manoeuvre or closing manoeuvre of said switching apparatus; and carrying out a comparison procedure among said first and second curves.

Abstract: 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.

Abstract: The invention relates to a medium voltage switching apparatus. The medium voltage switching apparatus includes one or more electric poles, each electrically coupleable with a corresponding electric line; for each electric pole, a fixed contact and a movable contact, the movable contact being reversibly movable between a decoupled position from the fixed contact and a coupled position with the fixed contact, the movable contact moving from the decoupled position to the coupled position during an closing manoeuvre of the switching apparatus and moving from the coupled position to the decoupled position during an opening manoeuvre of the switching apparatus; and actuating means adapted to actuate the movable contacts of the one or more electric poles. A control unit is adapted to select and carry out a selectable control routine in response to receiving an input signal at an input arrangement corresponding to the selectable routine.

Abstract: The present invention relates to a method for controlling a motor-driven vacuum circuit breaker. The method comprises initiate opening (S100) the circuit breaker, wherein the circuit breaker moves with an average opening speed of a contact pair of the circuit breaker, from a closed position to an open position of the circuit breaker, and decelerating (S110) the opening speed of the contact pair to below the average opening speed before the open position is reached to avoid overshoot, and initiate closing (S120) the circuit breaker, wherein the circuit breaker moves with an average closing speed of the contact pair, from the open position to the closed position, and decelerating (S130) the closing speed of the contact pair to below the average closing speed before contact touch at the closed position, wherein the circuit breaker moves with the decelerated speed at contact touch. A motor-driven vacuum circuit breaker, a computer program and a computer program product are also presented.

Abstract: The present invention relates to a method for controlling a motor-driven vacuum circuit breaker. The method comprises initiate opening (S100) the circuit breaker, wherein the circuit breaker moves with an average opening speed of a contact pair of the circuit breaker, from a closed position to an open position of the circuit breaker, and decelerating (S110) the opening speed of the contact pair to below the average opening speed before the open position is reached to avoid overshoot, and initiate closing (S120) the circuit breaker, wherein the circuit breaker moves with an average closing speed of the contact pair, from the open position to the closed position, and decelerating (S130) the closing speed of the contact pair to below the average closing speed before contact touch at the closed position, wherein the circuit breaker moves with the decelerated speed at contact touch. A motor-driven vacuum circuit breaker, a computer program and a computer program product are also presented.

Abstract: The invention relates to a medium voltage switching apparatus. The medium voltage switching apparatus comprises: one or more electric poles, each electrically coupleable with a corresponding electric line; for each electric pole, a fixed contact and a movable contact, said movable contact being reversibly movable between a decoupled position from said fixed contact and a coupled position with said fixed contact, said movable contact moving from said decoupled position to said coupled position during an closing manoeuvre of the switching apparatus and moving from said coupled position to said decoupled position during an opening manoeuvre of the switching apparatus; actuating means adapted to actuate the movable contacts of said one or more electric poles. The switching apparatus is operatively coupled with or comprises a control unit to control said actuating means.

Abstract: The invention relates to a control unit for a medium voltage switching apparatus. The control unit is adapted to carry out a diagnostic method to check operating conditions of one or more components of said electric poles. The diagnostic method includes the following steps: basing on a selected ideal position curve, obtaining one or more first curves indicative of an ideal behaviour of said switching apparatus, during an opening manoeuvre or closing manoeuvre of the switching apparatus; basing on detection signals provided by a closed-loop control arrangement of said control unit, calculating one or more second curves indicative of an actual behaviour of said switching apparatus, during an opening manoeuvre or closing manoeuvre of said switching apparatus; and carrying out a comparison procedure among said first and second curves.

Abstract: A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120°, and a third phase lagging the first phase by 240°, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120° in a time range from 60° before a peak of the phase to 90° after the peak.

Abstract: 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.

Abstract: A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120°, and a third phase lagging the first phase by 240°, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120° in a time range from 60° before a peak of the phase to 90° after the peak.

Abstract: The present invention relates to a method for controlling a motor-driven vacuum circuit breaker. The method comprises initiate opening (S100) the circuit breaker, wherein the circuit breaker moves with an average opening speed of a contact pair of the circuit breaker, from a closed position to an open position of the circuit breaker, and decelerating (S110) the opening speed of the contact pair to below the average opening speed before the open position is reached to avoid overshoot, and initiate closing (S120) the circuit breaker, wherein the circuit breaker moves with an average closing speed of the contact pair, from the open position to the closed position, and decelerating (S130) the closing speed of the contact pair to below the average closing speed before contact touch at the closed position, wherein the circuit breaker moves with the decelerated speed at contact touch. A motor-driven vacuum circuit breaker, a computer program and a computer program product are also presented.

Abstract: A method for controlling a circuit breaker, the circuit breaker is connected in a three-phase system having an inductive load, and the method includes a method for controlling a circuit breaker, the circuit breaker being connected in a three-phase system having an inductive load, the method includes opening a first phase of the three-phase system before a zero crossing of a current in the first phase, opening the second and third phases of the three-phase system a quarter period after opening the first phase, closing the first and second phase at a peak voltage of a voltage between the first and second phases, and closing the third phase a quarter period after closing the first and second phases. A circuit breaker controller is also presented.

Abstract: A method for controlling a circuit breaker, the circuit breaker is connected in a three-phase system having an inductive load, and the method includes a method for controlling a circuit breaker, the circuit breaker being connected in a three-phase system having an inductive load, the method includes opening a first phase of the three-phase system before a zero crossing of a current in the first phase, opening the second and third phases of the three-phase system a quarter period after opening the first phase, closing the first and second phase at a peak voltage of a voltage between the first and second phases, and closing the third phase a quarter period after closing the first and second phases. A circuit breaker controller is also presented.

Abstract: An electric power distribution switchgear is connected between an electric power grid and an electric power equipment. The switchgear includes a synchronized vacuum switching apparatus configured to break the current to the electric power equipment using a synchronized technique to avoid re-ignition during the breaking and thus any transients caused by such re-ignition; and a surge arrester arrangement connected to the electric power equipment, the surge arrester arrangement being designed and configured to only handle transients caused by the current chopping at the breaking. The surge arrester arrangement can be arranged remote from the electric power equipment, such as e.g. in the same casing as the synchronized vacuum switching apparatus.

Abstract: An electric power distribution switchgear is connected between an electric power grid and an electric power equipment. The switchgear includes a synchronized vacuum switching apparatus configured to break the current to the electric power equipment using a synchronized technique to avoid re-ignition during the breaking and thus any transients caused by such re-ignition; and a surge arrester arrangement connected to the electric power equipment, the surge arrester arrangement being designed and configured to only handle transients caused by the current chopping at the breaking. The surge arrester arrangement can be arranged remote from the electric power equipment, such as e.g. in the same casing as the synchronized vacuum switching apparatus.

Abstract: A system for transient over voltage protection of a three-phase transformer. Two surge arresters are series connected across each winding of the transformer and the center point connection of the two surge arresters is electrically connected to a middle location of the winding. Three additional surge arresters are electrically connected from each phase to ground in the case of either a delta or Y connected transformer; and/or connected from a neutral point to ground in the case of a Y connected transformer. The system allows for all of the surge arresters to be packaged as an integrated surge arrester system to minimize induced transient over voltages and high stresses on the transformer winding due to internal resonances.