A Statistical Analysis of Disturbance Data from Power Transmission and Distribution Grids in Sweden

In this report we analyse disturbance data from Swedish electric transmission and distribution grids. Under normal operating conditions lighting strikes are the main cause of disturbances in the Swedish national transmission grid. Further, there are only a few disturbances that lead to unserved energy. Also, the unserved energy in relation to the total amount of transmitted energy is extremely small. In the distribution grid of Stockholm, cable failures are the dominant cause of disturbance. For the studied transmission and distribution grids, unserved energy and the number of disturbances appears to be constant under the studied period. Finally, we demonstrate that the time between disturbances is exponentially distributed, and for the larger disturbances we show that the size follows a power law.