Considerations for AC railway traction power equipment-cost or performance-contradiction or challenge?

AC railway systems pose several challenges to the power supply installations: they should satisfy high nominal and peak power load demands, be highly efficient and reliable, allow for remote control of all operational functions and offer detailed analysis in case of faults. Faults, regardless of whether internal or external to the substations, should restrain the train operation as little and for as short a time as possible. The traction power supply system should be safe to the operators and the public, should require little maintenance, and have minimum life cycle cost, and after all, the traction power installations should fit into limited available space and should not produce much acoustic and electromagnetic noise