15 kV AC railway electrification

The 15 kV, 16.7 Hz AC railway electrification system is used in Germany, Austria, Switzerland, Sweden and Norway. The high voltage enables high power transmission with low losses powering traction motors available since the beginning of the 20th century. Railway electrification in late 20th century tended 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.

Contents

History

The earliest electrification of railways used DC series-wound motors. Starting at 600 V these power trains were able to be pushed to a voltage of 1,500 V - railway electrification of 3 kV puts two of these DC motors in series. This is still a relatively low voltage to allow for long and heavy trains to be pulled so that research was performed on other traction motors that could be run with higher voltage. The AC 50 Hz power grid (60 Hz in the US) was already established at the beginning of the 20th century, however the universal motors AC motor type had flashover problems in the motor brushgear. Tests showed that the problems were reduced at lower frequencies, in particular the reduction of the reactive impedance of motor windings and the eddy current losses in non-laminated magnetic pole-pieces originally designed to work with DC. In the German-speaking countries it was decided to start high-voltage electrification running at exactly one third of the frequency of the national power grid being 50 Hz making for 16⅔ Hertz. The 15 kV AC power can be transformed to the motor voltage needed for a specific drive power.

In Austria, Switzerland and Germany (except Mecklenburg-Western Pomerania and Saxony-Anhalt), the railway power grid is run by separate power plants. For these countries, 16⅔ Hz is equivalent to 1,000 rpm in a two-pole electrical generator. The first generators were synchronous alternate current generators or synchronous transformers; however, with the introduction of modern double fed induction generators, there was a bad side-effect of inducing a low DC power from the control current. Since this led to problems overheating the pole, it was decided to move the frequency of these generators slightly off the ⅓ frequency - the choice of 16.7 Hertz is completely arbitrary (it was just required to have the new frequency within the input tolerance of the traction motors that did already exist). Austria, Switzerland and Southern Germany switched to the new nominal frequency beginning on 16 October 1995 at 12:00 CET for their power plants[1][2]. Note that regional electrified sections run by synchronous generators keep their frequency of 16⅔ Hz just as Sweden and Norway still run their railway networks at 16⅔ Hz throughout.

One of the disadvantages of 16.7 Hz locomotives as compared to 50 Hz or 60 Hz 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. (See effect of frequency on the design of transformers.) 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 25 kV AC, 50 Hz locomotives (series 340) to operate on 15 kV AC, 16.7 Hz lines. As a result of using the same transformer cores (originally designed for 50 Hz) 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 (to around 1,000 kW).

There are no longer any technical reasons for not using 50 Hz systems - the disadvantage of needing to create a separate supply infrastructure has inhibited the spread of the concept beyond the original five countries. Other countries that started their railway electrification process later used 50 Hz systems (or 60 Hz systems in the US) early on. Newer electrification in Europe is mostly 25 kV AC at 50 Hz. Switching to this voltage/frequency is inhibited by some minor problems: on the network side, all insulators of overhead lines need to be checked to allow for the higher voltage and the distance to bridges and other structures needs to be increased slightly. 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 transport 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 (e.g. in Austria to Eastern Europe). 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 (except Mecklenburg-Western Pomerania and Saxony-Anhalt), Austria and Switzerland, there are special power grids for single phase AC current at 16.7 Hz; the voltage of these grids is 110 kV in Germany and Austria and 132 kV in Switzerland. This system is called centralized railway energy supply.

In Sweden, Norway, Mecklenburg-Western Pomerania and Saxony-Anhalt, there are no special single phase power grids. The energy 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 decentralized railway energy supply.

Generation and conversion

There are two possibilities to supply the centralized system with electricity: either the energy is provided by a special power plant that generates 110 kV (or 132 kV in the Swiss system) AC at 16.7 Hz or the energy is taken from the national power grid (e.g. 110 kV, 50 Hz) and converted into 55-0-55 kV (or 66-0-66 kV) AC at 16.7 Hz by rotary machines or AC/AC converters. 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 55 kV (or 66 kV) 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 110 kV (or 132 kV) AC to 15 kV AC and the energy is fed into the overhead line.

Asynchronous converters

The frequency of 16.7 Hz 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 16⅔ Hz (according to the technical details) in the single phase system, the frequency of the centralized system was set to 16.7 Hz.

Power plants providing 110 kV, 16.7 Hz, 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 15 kV, 16⅔ Hz 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, which uses central generation, central and decentral 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
Aschaffenburg
Aubing
Augsburg
Baden-Baden
Barnstorf
Bebra
Bengel
Biblis
Bingen
Böhla
Boizenburg
Borne
Braunschweig
Buchholz
Burgdorf
Burgweinting
Datteln
Denkendorf
Donauwörth
Dortmund
Duisburg
Düsseldorf
Ebensfeld
Eichenberg
Eilenburg
Eisenach
Elmshorn
Elsfleth
Emden
Emskirchen
Essen
Eutingen
Eystrup
Fallersleben
Finnentrop
Flieden
Flörsheim
Fulda
Freiburg
Friedberg
Fronhausen
Gabelbach
Garssen
Gemünden
Geltendorf
Geisenbrunn
Genshagener Heide
Gleidingen
Golm
Gössnitz (old)
Gössnitz (neu)
Grönhart
Grossheringen
Grosskorbetha
Güsen
Hagen
Halbe ( feed from 15 kV-line from Neuhof)
Hameln
Haren
Heeren
Herchen
Hessental
Holdingen
Holzkirchen
Höchst
Ihringshausen
Ingolstadt
Kaiserslautern
Karow
Karthaus
Kirchheim
Kirchmöser
Klebitz
Koblenz
Köln-Mülheim
Körle
Kreiensen
Kyhna
Landshut
Leer
Leipzig-Wahren
Leonberg
Limburg
Löhne
Lüneburg
Magdeburg
Mainbernheim
Markt Bibart
Mannheim
Markt Schwaben
Montabaur
Mörlach
Mottgers
Mühlacker
Muldenstein
Mühlanger
München-Freimann
München-Ost
Münster
Murnau
Nannhofen
Neckarelz
Neumarkt (Oberpfalz)
Neudittendorf
Neuhof
Neumünster
Niemberg
Nörten-Hardenberg
Oberacker
Oberdachstetten
Offenbach am Main
Offenburg
Orscheid
Osnabrück
Plattling
Plochingen
Pretzier
Pulling
Rathenow
Remagen
Rethen
Riesa
Ritterhude
Rödelheim
Rohrbach
Röhrmoos
Rosenheim
Rotenburg
Rottweil
Rudersdorf
Saalfeld
Salzbergen
Sindorf
Singen
Solpke
Sommerau
Steinbach am Wald
Stetzsch
Stolberg
Stuttgart-Rohr
Stuttgart-Zazenhausen
Traunstein
Uelzen
Enz
Wächtersbach
Waiblingen
Waigolshausen
Warburg
Weiterstadt
Werdau
Wickrath
Wiesental
Wolfratshausen
Wörsdorf
Wunstorf
Würzburg
Wurzen
Wustermark
Zapfendorf (shut down)

Switching stations

Switching stations without power conversion, generation or feeding in overhead wire

Facility Coordinates
Neckarwestheim
Nenndorf
Nitzahn
Schönarts

Central converter plants

In these facilities AC from public grid is transformed into single phase AC and fed into traction current grid. At some facilities, power is also fed in overhead wire. Conversion is made by machines or on electronic way.

Facility Year of inauguration Maximum transmission rate Used technology Coordinates
Borken 1963 50 MW Rotary converter
Bremen 100 MW GTO-Thyristor
Chemnitz 1965 Rotary converter
Dresden 1977 Rotary converter
Düsseldorf 15 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 ( rotary converter)/ 2010 ( inverter) 37 MW ( rotary converter), 64 MW ( inverter) 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 Rotary converter
Pforzheim ( shut-down) [1] Rotary converter
Saarbrücken Rotary converter
Singen ( shut-down in 2002) Rotary converter
Thyrow 2004/2005 8*15 = 120 MW GTO-Thyristor
Weimar 1973 Rotary converter

Decentral converter plants

In these facilities AC from public grid is transformed into single phase AC and fed only in overhead wire. Conversion is made by machines or by electronic means.

Facility Year of inauguration Maximum transmission rate Technology Used Coordinates
Adamsdorf 1984 Rotary converter
Anklam Rotary converter
Berlin-Rummelsburg 1984 Rotary converter
Bützow ( demolished) Rotary converter
Cottbus 1989 Rotary converter
Doberlug-Kirchhain 1981 (Umformer), 2008 (Inverter) 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 ( shut down) 1974 Rotary converter
Neustadt (Dosse) 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 inauguration Power Facility 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 Coal fired 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 (retired) 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

Border crossing powerlines

Germany - Austria

Leitung Coordinates
Walchenseekraftwerk - Zirl
Traunstein - Steinsdorf

Former inner German border

Leitung Coordinates
Lehrte - Heeren
Bebra - Weimar
Steinfeld am Wald - Saalfeld

Switzerland

Substations

In these facilities electricity is transformed down from 132 kV|66 kV-level of SSB to 15 kV. There is no conversion or generation of power.

Facility Coordinates
Biel
Brugg
Bussigny
Chur
Courtemaîche
Delémont
Eglisau
Emmenbrücke
Etzwilen
Farsch
Filisur (RhB)
Flüelen
Fribourg
Frutigen
Gampel
Genf-Tuleries
Giornico
Gland
Hendschiken
Kandersteg
Küblis ( RhB)
Melide
Muttenz
Neuchâtel
Killwangen
Olten
Puidoux
Rapperswil SG
Rivera
Roche
Romont FR
Rotkreuz
Saglianias (RhB)
Saint Léonhard
Sankt Margrethen
Sargans
Seebach
Selfranga
Sihlbrugg
Sils (RhB)
Stein AG
Steinen
Tavanasa (RhB)
Thun
Wetzikon ZH
Winterthur-Grüze
Yverdon
Ziegelbrücke
Zürich

Central converter plants

In these facilities AC from public grid is transformed into single phase AC and fed into traction current grid. At some facilities, power is also fed in overhead wire. Conversion is made by machines or on electronic way.

Facility Year of inauguration Maximum transmission rate Technology Used Coordinates
Bever (RhB) Rotary Converter
Landquart (RhB) Rotary Converter
Giubiasco Rotary Converter
Kerzers Rotary Converter
Massaboden Rotary Converter
Rupperswil Rotary Converter
Seebach Rotary Converter
Wimmis Rotary Converter

Switching stations

Switching stations without power conversion, generation or feeding in overhead wire

Facility Coordinates
Zollikofen

Power plants

Facility Year of inauguration Maximum
Power
Technology Used Coordinates
Amsteg 1922 55 MW Hydroelectric Power Plant
Le Châtelard VS Hydroelectric Power Plant
Etzelwerk Hydroelectric Power Plant
Göschenen Hydroelectric Power Plant
Klosters Hydroelectric Power Plant
Gösgen 51,3 MW Hydroelectric Power Plant
Massaboden 1916 7,2 MW Hydroelectric Power Plant
Mühleberg 1921 45 MW Hydroelectric Power Plant
Ritom 1920 Hydroelectric Power Plant
Rupperswil 1945 Hydroelectric Power Plant
Vernayaz Hydroelectric Power Plant
Wassen Hydroelectric Power Plant

Border crossings

Germany-Switzerland

Leitung Coordinates
Holdingen - Muttenz
Singen - Etzwilen

Austria

Substations

In these facilities electricity is transformed down from 110 kV-level of OBB to 15 kV. There is no conversion or generation of power.

Facility Coordinates
Absdorf
Angern
Amstetten (Österreich)
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 (old)
Zirl (neu)

Central converter plants

In these facilities, AC from the public grid is transformed into single phase AC and fed into the traction current grid. At some facilities, power is also fed to overhead wires. Conversion may be performed mechanically or electronically.

Facility Year of inauguration Power Maximum transmission rate Coordinates
Auhof 1956 90 MW
Bergern 1983
Haiming 1995
Kledering 1989
Sankt Michael 1975

Power plants

Facility Year of inauguration Power Type of power plant 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 (only direct fed of overhead wire)
Uttendorf Hydroelectric Power Plant
Weyer Hydroelectric Power Plant

See also

References

  1. ^ Bahnstromsystem (German) railway electrification systems
  2. ^ C. Linder: Umstellung der Sollfrequenz im zentralen Bahnstromnetz von 16⅔ Hz auf 16,70 Hz (English: Switching the frequency in train electric power supply network from 16 2/3 Hz to 16,70 Hz). In: Elektrische Bahnen. Book 12, Oldenbourg-Industrieverlag, Munich 2002, ISSN 0013-5437.

External links