For the continuous upgrading and development of infrastructure and mobile equipment, specialists from different countries strive to continuously optimize the existing traction & power supply system on one hand, and work actively to identify new mode of power supply, neutral-section passing, OCS materials, and online monitoring technologies on the other. At the same time, more focus is diverted to the energy and environment efficiency of the traction & power supply system, meaning that it has been growing in technical maturity. Future trends of development are concluded as follows.
(1) Performance of traction & power supply system to be further improved
With higher speed, the requirements for the stability, safety and reliability of the traction & power supply system are also increasing. The Société nationale des chemins de fer français (SNCF) studied the interaction between the traction converter and the power supply network, and developed the SiGHAR model using PSIM simulation software, so as to simulate various conditions of the railway network to the maximum extent. At the same time, relevant database was established to quickly determine the impedance peak value and predict the influence of compensation equipment. Japan's Mitsubishi Electric has developed a high speed DC circuit interruption technology for railway power supply system, which can detect short-circuit faults in real time and isolate the fault circuit in only 13 ms. The new DC circuit breaker meets the requirements specified in Japanese Industrial Standards, namely high interrupting capacity, high current change rate and high cut-off current. By suppressing short-circuit current amplitude within the standard value (55 kA), the technology helps ensure equipment safety, in other words no problem will occur even if the power supply capacity is very large.
(2) Superconducting cables to be further developed
In order to improve the efficiency of railway traction & power supply system, superconducting cable has become the innovative cable product developed countries compete to develop. Japan has been researching and developing superconducting cables since 2007, and has carried out the trial-production of a superconducting coaxial multi-phase transmission cable with a maximum critical current of up to 1,500 A. In 2010, an 8 kA superconducting cable, applicable to railway, was developed, and its critical current was measured to be more than 10 kA. In 2014, a superconducting cable with a length up to 310 meters was developed. The Railway Technical Research Institute (RTRI) of Japan plans to expand tests at railway operation sites in the future, continue to study the long-distance superconducting cable transmission technology, improve the length of superconducting cables used on commercial lines, and promote the commercialization process.
(3) New traction & power supply system and alternative energy sources to become future development trends
As for the new traction & power supply system, Alstom of France has developed a Hesop system for suburban railways. The application of IGBT converter technology has realized the innovation of traction & power supply technology, reduced the number of traction substations and improved the transport efficiency, contributing to the cost cut of infrastructure, the reduction in energy consumption, operation optimization and environment protection.
In terms of alternative energy sources, the railway industry has been actively carrying out researches on liquefied natural gas (LNG), hydrogen energy and other related sources. The Association of American Railroads (AAR) has begun to work on the development of standards for the LNG industry. GE Transportation, a locomotive manufacturer in the U.S., has used the existing GEVO engines to carry out LNG technical tests. BNSF has carried out diesel locomotive renovation projects in cooperation with GE and Caterpillar. Alstom of France, JR East of Japan, Stadler of Switzerland and other companies have engaged actively in developing hydrogen fuel trains, among which some products have been put into operation.
(4) New OCS materials and structures to be widely applied
Countries like Japan, Switzerland and Germany have actively carried out researches on new OCS materials and structures, conducive to the improvement of OCS performance and costs reduction. Swiss Federal Railways (Schweizerische Bundesbahnen, SBB) and HTW Dresden - University of Applied Sciences (HTW) in Germany have jointly carried out relevant experimental researches on copper alloy OCS conductors, the results of which show that the materials once mixed by certain proportion ratio can improve the thermal stability and wear resistance of OCS conductors. In Europe, countries like Denmark has erected OCS masts made of weather-resistant steel, which helps save maintenance costs. Central Japan Railway Company (JR Central) has carried out the development of the next generation of OCS. With the application of technologies such as inter-pantograph connection bus and couple-pantograph current receiving, it facilitates the efforts to eliminate the resonance problem of Tokaido Shinkansen.
