A systematic approach to evaluate the overall impact of the electric traction demands of a high-speed railroad on a power system

This paper introduces a systematic approach to the evaluation of the overall impact of the electric traction demands of a high-speed railroad (HSR) on a power system. These large unbalanced traction loads may cause system voltage and current unbalances and, therefore, overheat rotating machines, increase system losses, interfere with neighboring communication systems, and cause protection relays and measuring instruments to malfunction. Some of these problems may significantly affect the operation of the power system and other equipment connected to it. Hence, the proposed approach is oriented toward applications in system operation analysis rather than planning analysis. On the basis of the Newton-Raphson algorithm, a three-phase powerflow program was developed. In this program, most of the component models and solution techniques are those that were developed for three-phase power-flow studies. They are applied to accurately simulate a three-phase high-voltage network supplying the traction loads. Rigorous component models, such as generator, transmission line, power transformer and traction substation models, were incorporated into this program. By combining the electric demands of traction substations along an HSR, this program can be used to evaluate the overall impact of traction loads on a power system. On the basis of the simulation results, related improvement projects can be evaluated and conducted if necessary. This approach has been successfully tested on Taiwan's power system (Taipower system), to which the power-supply system of a planned HSR will be connected in the near future.