page_title: 15 kV AC railway electrification
section_title: Distribution networks
hierarchical_section_title: 15 kV AC railway electrification / History / Distribution networks
caption_attribution_description: Deutsch: Abspannmasten der Bahnstromleitungen am Umformerwerk Karlsruhe
context_page_description: Railway electrification systems using alternating current at 15 kilovolts and 16.7 Hertz are used on transport railways in Germany, Austria, Switzerland, Sweden, and Norway. The high voltage enables high power transmission with the lower frequency reducing the losses of the traction motors that were available at the beginning of the 20th century. Railway electrification in late 20th century tends to use 25 kV, 50 Hz AC systems which has become the preferred standard for new railway electrifications but extensions of the existing 15 kV networks are not completely unlikely. In particular, the Gotthard Base Tunnel still uses 15 kV, 16.7 Hz electrification.
  Due to high conversion costs, it is unlikely that existing 15 kV, 16.7 Hz systems will be converted to 25 kV, 50 Hz despite the fact that this would reduce the weight of the on-board step-down transformers to one third that of the present devices.
context_section_description: In Germany (except Mecklenburg-Western Pomerania and Saxony-Anhalt), Austria and Switzerland, there is a separate single-phase power distribution grid for railway power at 16.7 Hz; the voltage is 110 kV in Germany and Austria and 132 kV in Switzerland. This system is called the centralized railway energy supply. A separate single-phase power distribution grid makes the recuperation of energy during braking extremely easy in comparison with 25 kV 50 Hz system tied to 3 phase distribution grid.
  In Sweden, Norway, Mecklenburg-Western Pomerania and Saxony-Anhalt, the power is taken directly from the three-phase grid (110 kV at 50 Hz), converted to low frequency single phase and fed into the overhead line. This system is called the decentralized (i.e. local) railway energy supply.
caption: single-phase (two-wire) lines coming out of a converter plant
exif: {"Thumbnail JPEGInterchangeFormat": "44", "Thumbnail JPEGInterchangeFormatLength": "6207"}