Fault analysis of multi-phase unbalanced nonradial power distribution systems

Algorithms are presented in this paper for the accurate determination of voltages, currents, and power flows in faulted three-phase unbalanced nonradial power distribution systems. The calculation of steady-state fault currents begins from a converged power flow solution and uses generalized models for all power system components. These component models are formulated using a linear graph theory approach to network modeling. The linear graph modeling techniques are extended to form an admittance matrix system model. The three-phase source and load models that are used are based on an extension of the traditional models used to represent these elements in fault studies using symmetrical components. The distribution system model consisting of sources, loads, lines, transformers, and other components is modified to account for the fault and solved to yield the line-to-neutral voltages at each bus in the faulted distribution system. The faulted system current and power flows are determined using these voltages. The results obtained using the proposed modeling approach on a system provided by a local industry are compared with the results obtained from an existing classical three-phase fault analysis algorithm, and conclusions are drawn based on these comparisons