Amtrak's 60 Hz traction power system
Amtrak operates a 60 Hz Traction power system along the Northeast Corridor between New Haven, Connecticut and Boston, Massachusetts. This system was built in the late 1990s and supplies locomotives with power from an overhead catenary system at 25 kV, 60 Hz. The system is also commonly known as the Northend Electrification, in contrast to the Southend Electrification that runs from New York City to Washington DC.
The basic system unit is an Elementary Electrical Section consisting of a segment of one or more parallel tracks, each with a contiguous contact (or catenary or trolley) wire for the locomotive pantograph and an electrically separate feed wire. Elementary electrical sections are separated by section breaks where the contact and feeder wires can be interrupted with motor-operated air switches to isolate a section in the event of a fault or to permit maintenance.
An Electrical Section is a collection of elementary electrical sections, section breaks, air switches and paralleling stations between a Substation and a Switching Station.
At each substation, utility supplied single phase power is transformed and injected into the two electrical sections terminating at that substation. There are eight electrical sections in the system, two for each substation. The substations drive the contact and feed wires in a split phase arrangement so that each wire is at 25 kV with respect to the grounded running rails with 50 kV between them.
At periodically spaced Paralleling Stations within each electrical section the tracks' catenary wires are connected together to one side of an autotransformer and the feeder wires are connected together to the other side of the autotransformer. The autotransformer center-tap is connected to the grounded running rails that return the current from the locomotives. The paralleling stations thus reduce voltage drops by feeding a locomotive from both directions along its contact wire and spreading the load across all the contact and feed wires of a multitrack system. The split-phase arrangement also gains the increased efficiency of operating at 50 kV while the highest voltage with respect to ground remains only 25 kV. (The same split-phase method is used in North American homes to supply high power loads such as air conditioners with the efficiency of a 240 V supply while retaining the safety advantages of a 120 V supply.)
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