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Daniel Karlsson

Sture Lindahl

Göran Runvik

Lars Messing

Per-Anders L&ouml;f

A method for controlled reclosing of branch elements in an electric power system that has been subjected to a disturbance and that includes at least one branch element and at least one circuit breaker connected thereto. The angular difference between voltage vectors on both sides of the circuit breaker or at two end points of the branch element is detected and compared with a comparison value. In dependence on a magnitude of a deviation of the angular difference from the comparison value, the reclosing is either completed or blocked. The comparison value is updated automatically and regularly in such a way that an adaptive value is obtained. A system includes an element arranged to update the comparison value automatically and regularly in such a way that an adaptive value is obtained.

Method and device for controlled reclosing of a circuit breaker

A method for stabilization of the power balance in an electric power system including a number of nodes. An instantaneous value of the mains frequency of the electric power system is sensed. In dependence on the frequency deviation of the instantaneous value from a reference frequency value, a selected part of the electric power system, connected in a node, is disconnected in the node. A voltage amplitude value is sensed in the node. A measure of the magnitude of the deviation of the voltage amplitude value from a reference amplitude value is formed. A time lag is formed in dependence on the measure of the magnitude. The part of the electric power system is disconnected in dependence on the time lag.

Device and a method for power balancing

A method for determining/dimensioning measures for restoring an electrical power system, which experiences or is heading for a voltage instability, to a steady-state condition, wherein there is no immediate risk of instability. An actual voltage/phase angle in the electrical power system is determined. The power unbalance within at least one sub-area in the electrical power system is determined. Suitable power-balancing measures are determined. The extent of the respective measures is determined. The power-balancing measures are carried out. Also, a device for carrying out the method.

Method and a device for selecting and dimensioning measures in a case of instability in an electrical power system

The present invention discloses a system protection scheme comprising of at least two system protection terminals ( ), introduced at suitable locations in an electric power system ( ). The system protection terminals ( ) are interconnected by a communication system ( ), preferably using a substantially dedicated communication resource. At least-two of the system protection terminals ( ) are equipped to collect measurement signals ( ) associated with time stamped voltage or current values of the power system at that particular location or quantities derivable therefrom. The measurements are evaluated and related data is spread to other system protection terminals ( ). At least one of the system protection terminals ( ) is equipped to evaluate the existence of poorly damped power oscillations in the power network and if necessary provide control signals ( ) to power system actuating units. The evaluation is preferably based on changes in the node angle differences between the measurement locations.

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Malmö, Sweden

Daniel Karlsson