Advanced power system fault analysis method

This paper describes the capabilities and mathematical basis of an advanced fault analysis program. This program handles simultaneous unbalanced fault analysis with detailed treatment of shunt branches, off-nominal transformers, and loading conditions as given by a base case load flow solution. Provision is made for large groups of branches with common mutual coupling. The program uses the diakoptic (piecewise) solution method to allow each sequence network to be handled independently, even though they are effectively interconnected by unbalanced faults. Efficient computer implementation is based on the optimally ordered triangular factorization of the individual sequence admittance matrices within the diakoptic procedure, and an efficient iterative method of handling mutual couplings.