Evaluation of negative sequence current injecting into the public grid from different traction substation in electrical railways

This paper formulated the mathematical model of traction transformers of single phase traction substation, Three phase- two phase traction substations (V/V traction transformer, Scott transformer, impedance-matching balance transformer) which are widely used in China electrified railways. The negative-sequence current injected into the public grid and three - phase voltage unbalance at PCC is quantitatively analyzed. At the same time, the influence of feeder load proportion and feeder load phase error on the negative sequence current is also discussed. This proposed method provides significant assistance for the selection of traction substation types and external power supply schemes of other electrified railways.