The application of reliability criteria to a railway power supply network

Power systems have evolved over decades with their main emphasis focused towards providing reliable and economic supply of electrical energy to their customers. Spare or redundant capacities in generation and network facilities can be built but the main question has been, "how much redundancy and at what cost?" economic concerns like these have been widely recognised and are part of the design, planning, and operating criteria for most power system operators. Techniques such as Reliability Assessment have been developed in an attempt to resolve and satisfy the dilemma between economic and reliability constraints.