An interactive simulator for unbalanced systems

Unbalances due to faults and line switching have traditionally been calculated using symmetrical components. By contrast, compensation methods or their mathematical equivalent, the Matrix Modification Lemma (MML), a powerful tool for the solution of modified networks, are still employed primarily for contingency calculations. However, they can be efficiently applied to the calculation of voltages and currents due to faults and/or line switching. In the paper, the MML is applied for closing or opening of a switch which may also represent a fault. For better efficiency, the computations are performed in symmetrical components and sparsity techniques are used. To determine the effect of the switching operations, these are performed interactively and sequentially. Generators and loads are represented by appropriate Norton equivalents. Illustrative results are presented.