The objective of the project is to develop methodologies for (a) accurate computation of the total fault current and (b) selection of safety margins for the purpose of determining breaker adequacy or selection of breakers. The goal is to identify methods that will be applicable to all nominal voltages from distribution to ultra-high voltage equipment. Any new methods should be efficient and applicable to large scale systems.
The report provides an analysis of the standard methods. The report also provides a reference fault analysis method that is based on a high fidelity model of the power system (fully asymmetric, three-phase, physically based model) and an accurate time domain simulation method. The reference method captures all the details of the fault evolution and the changing impedances as trapped fluxes in the power system models decay with time after fault initiation. The reference fault analysis method is used to evaluate the standard methods and to propose a new simplified method that provides fault currents very close to those computed with the reference method but at a computational cost that is comparable to the standard methods. This is important because the reference method may be impractical for large scale systems.