Caltrain Modernization Program: Difference between revisions

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Power is supplied to the trains through an [[overhead line|overhead contact system]] (OCS), consisting of a messenger wire, which assumes a parabolic[[catenary]] shape due to sag, and a contact wire suspended below the messenger wire. The contact wire is nearly parallel to the ground, and supplies traction current to the pantograph(s) of an electric train. Both the messenger wire and the contact wire are energized with single-phase alternating current at 25 kV with a frequency of 60&nbsp;Hz. This allows the OCS to be used for both Caltrain and future California High-speed Rail service, and this electrical configuration matches that of Amtrak on [[Amtrak's 60 Hz traction power system|portions of the Northeast Corridor]] and portions of the [[New Jersey Transit]] commuter rail system.<ref name=DEIR-14-ch2 />

The [[25 kV AC railway electrification#2 x 25 kV autotransformer system|2×25 kV autotransformer electrification system]] includes a third energized parallel negative feeder wire which helps control [[electromagnetic field]] propagation.<ref name=DEIR-14-ch2 /><ref name=HSR-Sibal>{{cite report |url=http://www.hsr.ca.gov/docs/programs/eir_memos/Proj_Guidelines_TM3_1_1_1R02.pdf |title=Technical Memorandum: Traction Power 2x25 kV Autotransformer Feed Type Electrification System & System Voltages, TM 3.1.1.1 |date=April 2010 |author=Sibal, Vinod |publisher=California High-Speed Rail Authority |access-date=14 June 2018}}</ref> The feeder wire is electrified at the same voltage and frequency, but is shifted 180° out of phase so the voltage difference between the contact wire and the feeder wire is always 50kV.<ref>{{cite web |url=http://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M169/K717/169717211.docx |title=Resolution SED-2 adopting safety requirements governing the design, construction, installation, operation, and maintenance of the 25 kV AC (Alternating Current) railroad electrification system of the Peninsula Corridor Joint Powers Board (Caltrain) on the San Francisco Peninsula Rail Corridor |date=10 November 2016 |publisher={{DOClink}} Public Utilities Commission of the State of California, Electric Safety and Reliability Branch, Safety and Enforcement Division |access-date=14 June 2018}}</ref> The choice of a 2×25 kV autotransformer system means more traction power facilities are required in total, but also requires fewer traction power substations.<ref name=HSR-Sibal />