1. A method of fault analysis for an electric network having a plurality of multi-phase buses, the method comprising: computing equivalent circuits for the multi-phase buses of interest, each equivalent circuit including an N×N impedance matrix where N corresponds to the number of phases of the multi-phase bus for which that equivalent circuit is computed; determining elements of the impedance matrices based on voltages resulting from a plurality of experimental current injection vectors and a factorized pre-fault admittance matrix, the pre-fault admittance matrix representing nodal admittance of the multi-phase buses without faults; determining a fault current injection vector for each multi-phase bus and fault type of interest based on the equivalent circuit determined for that multi-phase bus; and determining a fault voltage vector for each multi-phase bus and fault type of interest based on the factorized pre-fault admittance matrix and the fault current injection vector determined for that multi-phase bus and fault type.