Rigorous evaluation of the voltage unbalance due to high-speed railway demands

A rigorous way of evaluating the voltage unbalance due to single-phase high-speed railway (HSR) demands on a three-phase power system is introduced in this paper. A three-phase power-flow program with simplified models of electric railway substations is adopted for rigorous studies. Various transformer connection schemes, including single-phase, V, Scott, and Le Blanc connections, are considered. The results are compared with those obtained by simple formulas that currently are commonly used to approximate the voltage unbalances. The comparison results indicate significant differences between these two approaches and emphasize that related improvement projects should be evaluated and implemented by the rigorous approach, not the simple formulas.