Calculation of voltage dips in meshed grids

Knowing the network parameters and the failure statistics of a network, the number of dips per year and the distributions of remaining voltages and dip durations can be estimated. Two approaches have been chosen by the authors: using a Monte-Carlo-method, the remaining voltages for random failure locations in the network are calculated. The simulation can be done for an arbitrary number of years, the number of dips per year is taken from the fault statistics. Using the second method, the calculation of the remaining voltage is performed for failures in every node of the network. The results are weighted according to the failure probability of each node. The dip duration is derived from the network´s protection system. These methods have been applied to a real network. The results are compared with a 2-years-measurement in the network. Furthermore the rating of an appropriate dynamic voltage restorer is discussed.