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Appendix A: Symmetrical
Components
The unsymmetrical operation of a 3-phase ac system—in steady state or during short
circuit—is analyzed by resolving the unsymmetrical applied voltages and resulting
currents into symmetrical components that are orthogonal in mathematical sense (not
physical space). The method was rst developed by Fortesque and later fully expanded
by Wagner, Evans, and Clarke for applications in practical power systems. It is analo-
gous to resolving any space vector force into three orthogonal components. It involves
algebras of complex numbers and matrices. We study here a brief theory and its appli-
cations in power sys ...