Features: power transmission to the two respective load single-phase traction line three-phase power systems. Two single-phase traction lines respectively to the downlink of locomotive power supply. In the ideal case, the two single-phase loads are the same. So, the traction transformer is used as a three-phase transformer. Traction transformer is a special voltage power transformers, should meet the traction load variation and external short frequent request, is the substation heart".