Short circuit analysis in unbalanced distribution networks

In this paper a short circuit analysis algorithm for radial three-phase distribution networks, based on two relationship matrices method, is presented. Two relationship matrices, the bus-current-injection-to-branch current matrix and the bus-current-to-bus-voltage matrix are used to represent the special topological characteristics of distribution networks. These two matrices can be accomplished by simple building algorithms and are easily implemented. The proposed short circuit analysis method is developed from these two matrices and can be used to analyze the various types of unsymmetrical faults only by one model. This model is included from four impedances that their amounts can be set from zero to extreme. Therefore, each kind of unsymmetrical faults is modelled by adjusting these impedances suitably. Since the proposed method does not use the traditional admittance matrix and only uses one model for fault calculations, therefore, the proposed method can achieve the advantages of reducing computation time, improving accuracy and efficiency, with lower memory requirements especially. Simulation results such as phase current and post- fault voltage profiles obtained using the proposed technique and IEEE 34-bus network are presented and discussed.