Abstract: A monitoring arrangement for monitoring a surge through a surge arrester, the surge arrester being adapted to be connected to a power network in order to protect an electrical equipment of the power network against incoming surges passing through the surge arrester. The monitoring arrangement detects a reignition surge, which reignition surge has been occasioned by a switching of a circuit breaker. The monitoring arrangement further calculates the number of detected reignition surges.

Abstract: A method of performing a circuit opening and closing operation in a power system including three phases, a three-phase transformer, and a circuit breaker system, the method including a) opening all three phases simultaneously such that a reference current of a reference phase is interrupted first at a first current zero crossing after the opening; and b) closing all three phases simultaneously at a phase to ground voltage of the phase lagging the reference phase by 120°, in a time range of ±90° from a negative peak of said phase to ground voltage if the current zero crossing is a positive current zero crossing, or in a time range of ±90° from a positive peak of said phase to ground voltage if the current zero crossing is a negative current zero crossing.

Abstract: A method of performing a circuit opening and closing operation in a power system including three phases, a three-phase transformer, and a circuit breaker system, the method including a) opening all three phases simultaneously such that a reference current of a reference phase is interrupted first at a first current zero crossing after the opening; and b) closing all three phases simultaneously at a phase to ground voltage of the phase lagging the reference phase by 120°, in a time range of ±90° from a negative peak of said phase to ground voltage if the current zero crossing is a positive current zero crossing, or in a time range of ±90° from a positive peak of said phase to ground voltage if the current zero crossing is a negative current zero crossing.

Abstract: A method of performing a circuit opening and closing operation in a power system having a first phase, a second phase), and a third phase, the method including a) opening only a reference phase among the first phase, the second phase and the third phase such that a reference current of the reference phase is interrupted at a first current zero crossing after the opening; b) opening the remaining phases after step a); c) closing only the reference phase and a phase lagging the reference phase by 120° simultaneously or essentially simultaneously at a closing phase angle of a phase to ground voltage of the reference phase of 320°±70° when the current zero crossing is a positive current zero crossing, or of 140°±70° when the current zero crossing is a negative current zero crossing; and d) closing the phase lagging the reference phase by 240° after step c).

Abstract: A monitoring arrangement for monitoring a surge through a surge arrester, the surge arrester being adapted to be connected to a power network in order to protect an electrical equipment of the power network against incoming surges passing through the surge arrester. The monitoring arrangement detects a reignition surge, which reignition surge has been occasioned by a switching of a circuit breaker. The monitoring arrangement further calculates the number of detected reignition surges.

Abstract: An arc detector for detecting undesired arcs. The arc detector includes: an antenna for receiving an electromagnetic signal representing an arc; and a discriminator for analyzing a signal from the antenna, the discriminator including a spectrum analyzer arranged to detect whether the signal represents a normal arc or an undesired arc. The discriminator is arranged to detect whether the signal represents a normal arc or an undesired arc by comparing signal levels at frequencies of a spectrum of the signal corresponding to at least one partial reference spectrum, and determining the arc to be a normal arc if a deviation from the reference spectrum is less than a threshold deviation. A corresponding method is also presented.

Abstract: A device for switching in and out a load with respect to an alternating voltage feeder has two mechanical switches connected in series in a current path between the load and the feeder and each having a by-pass branch with at least one member with ability to block current therethrough in at least a blocking direction and conduct current therethrough in at least one direction. A unit is adapted to control a procedure of a switching out and switching in by synchronization with the current in the feeder and the voltage of the feeder, respectively.

Abstract: An arc detector for detecting undesired arcs. The arc detector includes: an antenna for receiving an electromagnetic signal representing an arc; and a discriminator for analysing a signal from the antenna, the discriminator including a spectrum analyser arranged to detect whether the signal represents a normal arc or an undesired arc. The discriminator is arranged to detect whether the signal represents a normal arc or an undesired arc by comparing signal levels at frequencies of a spectrum of the signal corresponding to at least one partial reference spectrum, and determining the arc to be a normal arc if a deviation from the reference spectrum is less than a threshold deviation. A corresponding method is also presented.

Abstract: A device for switching in and out a load with respect to an alternating voltage feeder has two mechanical switches connected in series in a current path between the load and the feeder and each having a by-pass branch with at least one member with ability to block current therethrough in at least a blocking direction and conduct current therethrough in at least one direction. A unit is adapted to control a procedure of a switching out and switching in by synchronization with the current in the feeder and the voltage of the feeder, respectively.