15 kV AC railway electrification
s using at 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 AC systems which has become the preferred standard for new railway electrifications but extensions of the existing 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 systems will be converted to despite the fact that this would reduce the weight of the on-board step-down transformers to one third that of the present devices.
History
The first electrified railways used series-wound DC motors, first at 600 V and then 1,500 V. Areas with 3 kV DC catenaries used two 1,500 V DC motors in series. But even at 3 kV, the current needed to power a heavy train can be excessive. Although increasing the transmission voltage decreases the current and associated resistive losses for a given power, insulation limits make higher voltage traction motors impractical. Transformers on each locomotive are thus required to step high transmission voltages down to practical motor operating voltages. Before the development of suitable ways to efficiently transform DC currents through power electronics, efficient transformers strictly required alternating current ; thus high voltage electrified railways adopted AC along with the electric power distribution system.The 50 Hz AC grid was already established at the beginning of the 20th century. Although series-wound motors can in principle run on AC as well as DC large series-wound traction motors had problems with such high frequencies. High inductive reactance of the motor windings caused commutator flashover problems and the non-laminated magnetic pole-pieces originally designed for DC exhibited excessive eddy current losses. Using a lower AC frequency alleviated both problems.
In the German-speaking countries, high-voltage electrification began at, exactly one third of the national power grid frequency of 50 Hz. This facilitated the operation of rotary converters from the grid frequency and allowed dedicated railway power generators to operate at the same shaft speed as a standard 50 Hz generator by reducing the number of pole pairs by a factor of three. For example, a generator turning at would be wound with two pole pairs rather than six.
Separate plants supply railway power in Austria, Switzerland and Germany, except for Mecklenburg-Western Pomerania and Saxony-Anhalt; converters powered by the grid supply railway power in those two German states plus Sweden and Norway. Norway also has two hydro-electric power plants dedicated for railway power with output.
The first generators were synchronous AC generators or synchronous transformers; however, with the introduction of modern double fed induction generators, the control current induced an undesired DC component, leading to pole overheating problems. This was solved by shifting the frequency slightly away from exactly ⅓ the grid frequency; was arbitrarily chosen to remain within the tolerance of existing traction motors. Austria, Switzerland and Southern Germany switched their power plants to 16.7 Hz on 16 October 1995 at 12:00 CET. Note that regional electrified sections run by synchronous generators keep their frequency of just as Sweden and Norway still run their railway networks at throughout.
One of the disadvantages of locomotives as compared to or locomotives is the heavier transformer required to reduce the overhead line voltage to that used by the motors and their speed control gear. Low frequency transformers need to have heavier magnetic cores and larger windings for the same level of power conversion. The heavier transformers also lead to higher axle loads than for those of a higher frequency. This, in turn, leads to increased track wear and increases the need for more frequent track maintenance. The Czech Railways encountered the problem of the reduced power handling of lower frequency transformers when they rebuilt some AC, locomotives to operate on AC, lines. As a result of using the same transformer cores at the lower frequency, the transformers had to be de-rated to one third of their original power handling capability, thereby reducing the available tractive effort by the same amount.
These drawbacks, plus the need for a separate supply infrastructure and the lack of any technical advantages with modern motors and controllers has limited the use of Hz and 16.7 Hz beyond the original five countries. Most other countries electrified their railways at the utility frequency of 50/60 Hz. Newer European electrification is mostly 25 kV AC at 50 Hz. Conversion to this voltage/frequency requires higher voltage insulators and greater clearance between lines and bridges and other structures. This is now standard for new overhead lines as well as for modernizing old installations.
Simple European standardization with an alignment of voltage/frequency across Europe is not necessarily cost-effective since trans-border traction is more limited by the differing national standards in other areas. To equip an electric locomotive with a transformer for two or more input voltages is cheap compared to the cost of installing multiple train protection systems and to run them through the approval procedure to get access to the railway network in other countries. However, some new high-speed lines to neighbouring countries are already intended to be built to 25 kV. Newer locomotives are always built with asynchronous motor control systems that have no problem with a range of input frequencies including DC. However the Deutsche Bahn train operator does still use older models from the standard electric locomotive series - even though some are now as much as 50 years old. As soon as these obsolescent models are decommissioned, it will be easier to standardise, but this may take a few decades to happen. Meanwhile, the Deutsche Bahn tends to order train sets that are capable of running multiple electrification systems.
Distribution networks
In Germany, Austria and Switzerland, there is a separate single-phase power distribution grid for railway power at ; the voltage is in Germany and Austria and 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 25kV 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, converted to low frequency single phase and fed into the overhead line. This system is called the decentralized railway energy supply.
Generation and conversion
The centralized system is supplied by special power plants that generate AC at and by rotary converters or AC/AC converters that are supplied from the national power grid, they convert it to 55-0-55 kV AC at. The 0 V point is connected to earth through an inductance so that each conductor of the single phase AC power line has a voltage of with respect to earth potential. This is similar to split-phase electric power systems and results in a balanced line transmission. The inductance through which the earthing is done is designed to limit earth currents in cases of faults on the line. At the transformer substations, the voltage is transformed from AC to AC and the energy is fed into the overhead line.Asynchronous converters
The frequency of depends on the necessity to avoid synchronism in parts of the rotary machine, which consists principally of a three phase asynchronous motor and a single phase synchronous generator. Since synchronism sets in at a frequency of in the single phase system, the frequency of the centralized system was set to.Power plants providing,, are either dedicated to generating this specific single phase AC or have special generators for the purpose, such as the Neckarwestheim nuclear power plant or the Walchensee hydroelectric power station.
Synchronous converters
The power for the decentralized system is taken directly from the national power grid and directly transformed and converted into, by synchronous-synchronous-converters or static converters. Both systems need additional transformers. The converters consist of a three-phase synchronous motor and a single-phase synchronous generator. The decentralized system in the north-east of Germany was established by the Deutsche Reichsbahn in the 1980s, because there was no centralized system available in these areas.Facilities for 15 kV AC railway electrification in Germany, Austria and Switzerland
Germany, Austria and Switzerland operate the largest interconnected 15 kV AC system with central generation, and central and local converter plants.Germany
Substations
In these facilities electricity is transformed down from 110 kV-level of DB to 15 kV.There is no conversion or generation of power.
| Facility | Coordinates |
| Aalen | |
| Adelsheim | |
| Almstedt | |
| Amstetten | |
| Appenweier | |
| Aschaffenburg | |
| Aubing | |
| Augsburg | |
| Bachstedt | |
| Baden-Baden | |
| Bad Reichenhall | |
| Barnstorf | |
| Bebra | |
| Bengel | |
| Berlin-Schönefeld | |
| Biblis | |
| Bingen | |
| Böhla | |
| Boizenburg | |
| Borken | |
| Borne | |
| Braunschweig | |
| Buchholz | |
| Burgdorf | |
| Burgweinting | |
| Chemnitz | |
| Datteln | |
| Denkendorf | |
| Donauwörth | |
| Dörstewitz | |
| Dortmund | |
| Dortmund-Scharnhorst | |
| Dresden | |
| Duisburg | |
| Düsseldorf | |
| Ebensfeld | |
| Eggolsheim | |
| Eichenberg | |
| Eilenburg | |
| Eischleben | |
| Eisenach | |
| Elmshorn | |
| Elsfleth | |
| Emden | |
| Emskirchen | |
| Essen | |
| Eutingen | |
| Eystrup | |
| Fallersleben | |
| Finnentrop | |
| Flieden | |
| Flörsheim | |
| Freiburg | |
| Friedberg | |
| Fronhausen | |
| Fulda | |
| Gabelbach | |
| Garssen | |
| Geisenbrunn | |
| Geltendorf | |
| Gemünden | |
| Genshagener Heide | |
| Gleidingen | |
| Golm | |
| Gössnitz | |
| Gössnitz | |
| Grafing | |
| Grönhart | |
| Grossheringen | |
| Grosskorbetha | |
| Grünauer Kreuz | |
| Güsen | |
| Hagen | |
| Hahn | |
| Halbe | |
| Haltingen | |
| Hamburg-Harburg | |
| Hameln | |
| Haren | |
| Heeren | |
| Herbolzheim | |
| Herchen | |
| Hessental | |
| Höchst | |
| Holzkirchen | |
| Ihringshausen | |
| Ilmenau-Wolfsberg | |
| Ingolstadt | |
| Jübek | |
| Kaiserslautern | |
| Karow | |
| Karthaus | |
| Kirchheim | |
| Kirchmöser | |
| Klebitz | |
| Koblenz | |
| Köln | |
| Köln-Mülheim | |
| Körle | |
| Kreiensen | |
| Kyhna | |
| Landshut | |
| Leer | |
| Lehrte | |
| Leipzig-Wahren | |
| Leonberg | |
| Limburg | |
| Löhne | |
| Lüneburg | |
| Magdeburg | |
| Mainbernheim | |
| Mannheim | |
| Markt Bibart | |
| Markt Schwaben | |
| Marl | |
| Meckesheim | |
| Mehrhoog | |
| Montabaur | |
| Mörlach | |
| Mottgers | |
| Mühlacker | |
| Mühlanger | |
| Muldenstein | |
| Müllheim | |
| München-Freimann | |
| München-Ost | |
| Münster | |
| Murnau | |
| Nannhofen | |
| Neckarelz | |
| Neumarkt | |
| Neudittendorf | |
| Neuhof | |
| Neumünster | |
| Neu-Ulm | |
| Niedernhausen | |
| Niemberg | |
| Nörten-Hardenberg | |
| Nürnberg | |
| Nürnberg-Stein | |
| Oberacker | |
| Oberdachstetten | |
| Oelde | |
| Offenbach am Main | |
| Offenburg | |
| Orscheid | |
| Osnabrück | |
| Plattling | |
| Plochingen | |
| Pretzier | |
| Pulling | |
| Rathenow | |
| Remagen | |
| Rethen | |
| Riesa | |
| Ritterhude | |
| Rödelheim | |
| Rohrbach | |
| Röhrmoos | |
| Rosenheim | |
| Rotenburg | |
| Rotenburg | |
| Roth | |
| Rottweil | |
| Rudersdorf | |
| Saalfeld | |
| Saarbrücken | |
| Salzbergen | |
| Saubachtal | |
| Siegburg | |
| Sindorf | |
| Singen | |
| Solpke | |
| Sommerau | |
| Steinbach am Wald | |
| Stetzsch | |
| Stolberg | |
| Stuttgart-Rohr | |
| Stuttgart-Zazenhausen | |
| Traunstein | |
| Uelzen | |
| Urbach | |
| Vaihingen / Enz | |
| Wächtersbach | |
| Waiblingen | |
| Waigolshausen | |
| Warburg | |
| Weimar | |
| Weiterstadt | |
| Werdau | |
| Wickrath | |
| Wiesbaden | |
| Wiesental | |
| Wolfratshausen | |
| Wörsdorf | |
| Wunstorf | |
| Würzburg | |
| Wurzen | |
| Wustermark | |
| Zapfendorf |
Switching stations
Stations for connecting/isolating parts of the system.| Facility | Coordinates |
| Gabelbach | |
| Kirchhellen | |
| Neckarwestheim | |
| Nenndorf | |
| Nitzahn | |
| Schönarts |
Central converter plants
In these facilities the AC from the public grid is transformed and converted into the single phase AC and fed into the railway current distribution grid. At some facilities, power is also fed to the overhead line. Conversion is done by rotary converters or electronic inverters.| Facility | Year of commissioning | Power | Technology | Coordinates |
| Aschaffenburg | 2010 | 60 MW | GTO-Thyristor | |
| Borken | 1963 | 50 MW | Rotary converter | |
| Bremen | 100 MW | GTO-thyristor | ||
| Chemnitz | 1965 | Rotary converter | ||
| Dresden | 1977 | Rotary converter | ||
| Düsseldorf | 30 MW | GTO-thyristor | ||
| Hamburg-Harburg | Rotary converter | |||
| Jübek | 14 MW | GTO-thyristor | ||
| Karlsfeld | 100 MW | GTO-thyristor | ||
| Karlsruhe | 1957 | 53 MW | Rotary converter | |
| Köln | 1957 | 75 MW | Rotary converter | |
| Lehrte | 1963 / 2010 | 37 MW / 64 MW | Rotary converter/ inverter | |
| Limburg | 120 MW | IGCT inverter | ||
| Marl | 1963 | 25 MW | Rotary converter | |
| Neckarwestheim | 1989 | 140 MW | Rotary converter | |
| Neckarwestheim II | 2011 | 140 MW | GTO-thyristor | |
| Neu-Ulm | Rotary converter | |||
| Nürnberg | 1939 | 34 | Rotary converter | |
| Nürnberg | 2012 | 75 | IGBT-Inverter | |
| Pforzheim | Rotary converter | |||
| Saarbrücken | Rotary converter | |||
| Singen | Rotary converter | |||
| Thyrow | 2004/2005 | 8×15 = 120 MW | GTO-thyristor | |
| Weimar | 1973 | Rotary converter |
Local converter plants
In these facilities the AC from the public grid is transformed and converted into the single phase AC and fed to the overhead line. Conversion is done by rotary converters or electronic inverters.| Facility | Year of commissioning | Power | Technology | Coordinates |
| Adamsdorf | 1984 | Rotary converter | ||
| Anklam | Rotary converter | |||
| Berlin-Rummelsburg | 1984 | Rotary converter | ||
| Bützow | Rotary converter | |||
| Cottbus | 1989 | Rotary converter | ||
| Doberlug-Kirchhain | 1981, 2008 | Inverter | ||
| Eberswalde | 1987 | Rotary converter | ||
| Falkenberg | 1987 | Rotary converter | ||
| Oder | Rotary converter | |||
| Lalendorf | Rotary converter | |||
| Löwenberger Land | Rotary converter | |||
| Ludwigsfelde | 1981 | Rotary converter | ||
| Lübeck-Genin | 2008 | Inverter | ? | |
| Magdeburg | 1974 | Rotary converter | ||
| Neustadt | Rotary converter | |||
| Oberröblingen | Rotary converter | |||
| Prenzlau | Rotary converter | |||
| Rosslau | Rotary converter | |||
| Rostock | 1985 | Rotary converter | ||
| Schwerin | 1987 | Rotary converter | ||
| Senftenberg | 1988 | Rotary converter | ||
| Stendal | Rotary converter | |||
| Stralsund | Rotary converter | |||
| Wittenberg | 1978 | Rotary converter | ||
| Wittenberge | 1987 | Rotary converter | ||
| Wolkramshausen | Inverter | |||
| Wünsdorf | 1982 | Rotary converter | ||
| Wustermark | Rotary converter |
Power plants
| Facility | Year of commissioning | Power | Type | State | Coordinates |
| Bad Abbach | 2000 | 3.5 MW | Hydroelectric power plant | Bavaria | |
| Aufkirchen | Hydroelectric power plant | Bavaria | |||
| Bad Reichenhall | 1912 | 7.2 MW | Hydroelectric power plant | Bavaria | |
| Bergheim | 1970 | 23.7 MW | Hydroelectric power plant | Bavaria | |
| Bertoldsheim | 1967 | 18.9 MW | Hydroelectric power plant | Bavaria | |
| Bittenbrunn | 1969 | 20.2 MW | Hydroelectric power plant | Bavaria | |
| Datteln | Coal-fired power plant | North Rhine-Westphalia | |||
| Eitting Hydroelectric Power Plant | Hydroelectric power plant | Bavaria | |||
| Ingolstadt | 1971 | 19.8 MW | Hydroelectric power plant | Bavaria | |
| Kammerl | 1905 | Hydroelectric power plant | Bavaria | ||
| Kirchmöser | 160 MW | Gas turbine power plant | Brandenburg | ||
| Langenprozelten | 1976 | 160 MW | Hydroelectric power plant | Bavaria | |
| Lausward | 1957 | 520 MW | Gas turbine power plant | North Rhine-Westphalia | |
| Lünen | 1984 | 110 MW | Coal-fired power plant | North Rhine-Westphalia | |
| Mannheim | 1955 | 190 MW | Coal-fired power plant | Baden-Württemberg | |
| Muldenstein | 1912 | 11.3 MW | Coal-fired power plant | Saxony-Anhalt | |
| Mittelsbüren | 110 MW | Coal-fired power plant | Bremen | ||
| Neckarwestheim I | 1976 | 190 MW | Nuclear power plant | Baden-Württemberg | |
| Pfrombach | Hydroelectric power plant | Bavaria | |||
| Vohburg | Hydroelectric power plant | Bavaria | |||
| Walchensee | 1924 | Hydroelectric power plant | Bavaria |
Points where two powerlines for traction current crosses each other without interconnection
| Lines | Coordinates |
| Flieden-Bebra / Fulda-Mottgers | |
| Bebra-Borken / Kirchheim-Körle | |
| Karlsruhe-Mühlacker /Vaihingen-Graben/Neudorf | |
| Orscheid-Köln / Orscheid-Montabaur | |
| Mannheim-Neckarelz / Mannheim-Wiesental |
Border-crossing power lines
Germany – Austria
| Line | Coordinates |
| Walchenseekraftwerk – Zirl | |
| Traunstein – Steinsdorf |
Former border between West and East Germany
| Line | Coordinates |
| Lehrte – Heeren | |
| Bebra – Weimar | |
| Steinfeld am Wald – Saalfeld |
Switzerland
Substations
In these facilities electricity is transformed down from 132 kV or 66 kV to 15 kV.There is no conversion or generation of power.
| Facility | Coordinates |
| Balerna | |
| Biel | |
| Brugg | |
| Burgdorf | |
| Bussigny | |
| Chur | |
| Croy | |
| Courtemaîche | |
| Delémont | |
| Eglisau | |
| Emmenbrücke | |
| Etzwilen | |
| Farsch | |
| Filisur | |
| Flüelen | |
| Fribourg | |
| Frutigen | |
| Gampel | |
| Genève-Tuleries | |
| Giornico | |
| Gland | |
| Hendschiken | |
| Kandersteg | |
| Küblis | |
| Melide | |
| Muttenz | |
| Neuchâtel | |
| Killwangen | |
| Olten | |
| Puidoux | |
| Rapperswil SG | |
| Rivera | |
| Roche | |
| Romont FR | |
| Rotkreuz | |
| Sagliains | |
| Saint Léonard | |
| Sankt Margrethen | |
| Sargans | |
| Seebach | |
| Selfranga | |
| Sihlbrugg | |
| Sils | |
| Stein AG | |
| Steinen | |
| Tavanasa | |
| Thun | |
| Varzo | |
| Wanzwil | |
| Wetzikon ZH | |
| Winterthur-Grüze | |
| Yverdon | |
| Ziegelbrücke | |
| Zürich |
Central converter plants
In these facilities the AC from public grid is transformed and converted into the single phase AC and fed into the railway current distribution grid. At some facilities, power is also fed to the overhead line. Conversion is done by rotary converters or electronic inverters.| Facility | Year of commissioning | Power | Technology used | Coordinates |
| Bever | 4,6 MW | Rotary converter | ||
| Landquart | 5 MW | Rotary converter | ||
| Giubiasco | Rotary converter | |||
| Kerzers | Rotary converter | |||
| Massaboden | Rotary converter | |||
| Rupperswil | Rotary converter | |||
| Seebach | Rotary converter | |||
| Wimmis | Rotary converter |
Switching stations
Stations for connecting/isolating parts of the system.| Facility | Coordinates |
| Zollikofen |
Power plants
Points, where two powerlines for traction current crosses each other without interconnection
| Lines | Coordinates |
| Bussigny-Croy / Romanel-Les Tuileries | |
| Puidoux-Kerzers / Bussigny-Chamoson | |
| Puidoux-Vernayaz/ Bussigny-Chamoson | |
| Puidoux-Vernayaz/ Bussigny-Chamoson | |
| Puidoux-Vernayaz/ Vernayaz Branch | |
| Vernayaz-Brig/ Bussigny-Chamoson |
Border-crossing power lines
Germany–Switzerland
| Line | Coordinates |
| Holdingen – Muttenz | |
| Singen – Etzwilen |
Austria
Substations
In these facilities electricity is transformed down from 110 kV to 15 kV. No conversion or generation of power takes place.| Facility | Coordinates |
| Absdorf | |
| Angern | |
| Amstetten | |
| Asten | |
| Attnang-Puchheim | |
| Bad Vöslau | |
| Bludenz | |
| Bruck Mur | |
| Dölsach | |
| Dorfgastein | |
| Elsbethen | |
| Feldkirch | |
| Florisdorf | |
| Fritzens-Wattens | |
| Gaisbach Wartberg | |
| Golling-Abtenau | |
| Göpfritz | |
| Gries am Brenner | |
| Götzendorf | |
| Graz | |
| Haag | |
| Hohenau | |
| Hütteldorf | |
| Kitzbühel | |
| Küpfern | |
| Landeck | |
| Mallnitz | |
| Marchtrenk | |
| Mariahof | |
| Matrei | |
| Meidling | |
| Mistelbach | |
| Münster | |
| Parndorf | |
| Pettneu | |
| Pusarnitz | |
| Riedau | |
| Rohr | |
| Sankt Johann im Pongau | |
| Sankt Pölten | |
| Sankt Veit | |
| Schladming | |
| Schlöglmühl | |
| Semmering | |
| Wien-Simmering | |
| Steindorf | |
| Tulln | |
| Unterberg | |
| Villach | |
| Wald am Schoberpass | |
| Wartberg an der Krems | |
| Wegscheid | |
| Wiener Neustadt | |
| Wörgl | |
| Zellerndorf | |
| Zirl | |
| Zirl |
Central converter plants
In these facilities the AC from the public grid is transformed and converted into the single phase AC and fed into the railway current distribution grid. At some facilities, power is also fed to the overhead line. Conversion is done by rotary converters or electronic inverters.| Facility | Year of commissioning | Power | Coordinates |
| Auhof | 1956 | 90 MW | |
| Bergern | 1983 | ||
| Haiming | 1995 | ||
| Kledering | 1989 | ||
| Sankt Michael | 1975 |
Power plants
| Facility | Year of commissioning | Power | Type | Coordinates |
| Annabrücke | 20 MW | Hydroelectric power plant | ||
| Braz | 1954 | 20 MW | Hydroelectric power plant | |
| Enzigerboden | 20 MW | Hydroelectric power plant | ||
| Fulpmes | 1983 | 15 MW | Hydroelectric power plant | |
| Obervellach | Hydroelectric power plant | |||
| Schaltposten Schönberg | Hydroelectric power plant | |||
| Sankt Pantaleon | Hydroelectric power plant | |||
| Schneiderau | Hydroelectric power plant | |||
| Spullersee | 1925 | 36 MW | Hydroelectric power plant | |
| Steeg | 1910 | Hydroelectric power plant | ||
| Uttendorf | Hydroelectric power plant | |||
| Weyer | Hydroelectric power plant |
Points, where two powerlines for traction current crosses each other without interconnection
| Lines | Coordinates |
| Sankt Johann im Pongau-Bruck/Fusch / Sankt Johann im Pongau-Selzthal | |
| Sankt Johann im Pongau-Uttendorf / Sankt Johann im Pongau-Mallnitz | |
| Sankt Johann im Pongau-Bruck/Fusch / Sankt Johann im Pongau-Mallnitz | |
| Sankt Johann im Pongau-Schneiderau / Bruck/Fusch-Uttendorf | |
| Sankt Johann im Pongau-Schneiderau / Uttendorf-Kitzbühl | |
| Sankt Johann im Pongau-Schneiderau / Uttendorf-Kitzbühl | |
| Bruck/Fusch-Enzingerboden / Uttendorf-Kitzbühl | |
| Uttendorf-Enzingerboden, Schneiderau Branch / Schneiderau-Enzingerboden | |
| Uttendorf-Enzingerboden / Schneiderau-Enzingerboden | |
| Uttendorf-Enzingerboden / Schneiderau-Enzingerboden |