Modern transportation is characterized by high efficiency and high efficiency. The high-speed, large-scale and long-distance transportation of transportation are leading the development trend of the industry. Among them, the power supply and distribution system of airports, subway stations and expressway service areas are relatively close to the construction industry. The representative loads of ports include gantry cranes and ship shore power, while the electrified railway traction system uses 27.5kV line voltage power supply and DC drive Way, so it has its particularity.