Traction power systems reliability concepts

Reliability of a traction power system may be defined as its ability to continuously supply electrical power of adequate quality during sudden disturbances such as a short circuit or loss of system elements, while operating with a normal scheme configuration, or during scheduled maintenance and repairs, without causing safety hazards, train delays or public nuisance. While the utility power systems\´ reliability may be expressed in outage minutes per year (or any other time period), which is calculated as a ratio of customers\´ electrical energy deprivation to system\´s total power capacity, for a traction power systems\´ reliability evaluation, minutes of train delays caused by power interruption or relative values such as delay minutes per passenger-mile may be utilized. Considering the accelerated growth of traction power systems across the US in recent and coming years, creation of a reliability council similar to NERC to develop reliability standards within the railroad industry may be highly beneficial: it could pull together statistical data on reliability from different railroads, analyze them, and develop guidelines and recommendations for optimal solutions to provide adequate reliability with the lowest cost possible. IEEE Traction Power Substation Committee and AREMA Committee 33 on Electrical Energy Utilization could initiate and lay groundwork for the creation of such a council. While most of the contingency situations may be predicted and counteracted on the design stage, only the real-life experience is the ultimate test for reliability. That\´s why it is so important to keep and analyze records of any outages and contingencies encountered during traction power system operations. Records for these purposes may be provided by multi-purpose relays that become widely used in recently built substations. Classification of voltage events in future Standard may be based on the Institute of Electrical and Electronic Engineers Standard 1159-1995 "IEEE Recommen- - ded Practice for Monitoring Electric Power Quality", classification of reliability events - according to NERC Planning Standards.