Protection scheme for a new AC railway traction power system

Abstract

The new, 160 mile long Amtrak Northeast Corridor railway electrification project has four supply substations that connect 115 kV utility power to the 55 kV single-phase, AC traction power system. Eighteen autotransformer-paralleling stations are spaced along the route. Each autotransformer connects the overhead catenary to an auxiliary feeder line, with the rails tied to an intermediate point of the autotransformer. Each train draws power from two adjoining autotransformers. The protection scheme includes distance protection for the catenary and feeder lines, transformer protection for the power transformers and autotransformers, plus bus protection and backup protection. The protection scheme uses a specialized type of numerical distance protection relay optimized for railway traction systems. In the event of a fault on the protected part of the line, a trip occurs and the relay calculates the distance to the fault. All the autotransformers within that distance are automatically disconnected, and the relay attempts a reclose. If the reclose is successful, the autotransformers are reconnected.