Systematic short-circuit-analysis method for unbalanced distribution systems

A systematic short-circuit-analysis method for unbalanced distribution systems is proposed. The proposed method employs the actual three-phase models to handle unsymmetrical faults. Two matrices developed from the topological structures of distribution systems are used to analyse the variations of bus voltages, bus-current injections and branch currents under fault conditions. A short-circuit-analysis method can then be developed from these two matrices and be used to solve the various types of single or simultaneous unsymmetrical faults. Since the proposed method does not use the traditional admittance matrix, the time-consuming procedures such as tri-factorisation or inverse of admittance matrix are not necessary; therefore, the proposed method can achieve the advantages of high speed, robust convergence and improved accuracy with lower memory requirements. Test results show that the proposed method is systematic, efficient, accurate and easily programmable.