Implementation of New Technologies in Traction Power Systems

Due to significant developments in power electronics since the 1980’s, a row of new components are being used for both utility [1] and traction power substations, leading to new concepts in their design and construction. Among others, such innovations as incorporation of microprocessor-based multifunction protective relays and programmable logic controllers are changing traditional substations’ equipment layout and inter-connections; the development and experimental use of thyristor rectifiers and solid-state DC circuit breakers is under way. A significant reduction in the amount of protective and control devices (and associated wiring) has been achieved by introduction of multi-function relays (MFR or MPR – Multi-Purpose Relay), capable of replacing a whole group of relays used for equipment protection and automated control; for example, one MFR may perform functions of overcurrent and ground fault protection, over- and undervoltage protection, fault sensing and reclosing. Plus, it may be used for data logging and data recording purposes [2]. Additionally, high end MPRs have remote access features allowing not only to set any parameters, but even provide firmware upgrade without visiting the substation, thus providing labor savings. Therefore, one MFR may replace about a dozen of traditional relays and devices, along with their wiring and save maintenance expenses as well. Thyristor Controlled Rectifiers (TCR’s) are another significant innovation in traditional DC traction power substation design. Thyristor rectifiers are offering very important benefit of regulated DC voltage: at the substation’s bus output, the voltage may be constant from 0 to a 100% or even 150% load, which means improved train performance in terms of speed and reliability, as well as lower losses of energy in third rails, and possibility of raising third rail system voltage in the future, thus further lowering losses of energy in the system. Alternatively, it allows to increase the distance between the substations and thus reduce total number of substations. LIRR installed one thyristor rectifier for experimental use in 2003. Flywheel-based energy storage system is another important innovation that is being installed by the LIRR for experimental use. LIRR is installing for experimental use trackside fly-wheel energy storage system developed and tested by the British uranium enrichment company URENCO. According to Tarrant [3], in March 2002 the company successfully tested the KESS – Kinetic Energy Storage System and demonstrated 11% to 18% energy savings in different conditions of operation, because of the lower losses due to higher voltage during the acceleration period.