Railway electrification system

Traction current is the electric current used for the drive of electric trains. The power supply to electric vehicles is either via an overhead line or conductor rail. As a return line to serve both the steel rails of the track as well as the the tracks surrounding soil.

Historically developed in different countries or at different railway companies various current systems, which are often independent from the rest of the power supply system of the country.

• 2.2.3.1 use of externally generated three-phase
• 2.2.3.2 AC drive with on-board three-phase conversion

• 3.1 Generation and distribution of electric energy
• 3.2 traction power network 3.2.1 Central Supply
• 3.2.2 Decentralized supply

• 3.5.1 Germany 3.5.1.1 Existing hydropower plants
• 3.5.1.2 Existing nuclear power plants
• 3.5.1.3 Existing thermal power plants
• 3.5.1.4 Former plants

• 3.5.2.1 Railway-owned power plants
• 3.5.2.2 Train Strangers power plants

• 3.5.3.1 Power Plants of the SBB
• 3.5.3.2 power plants with SBB participation
• 3.5.3.3 strangers power plants

• 3.6.1 Bahnstromumformerwerke in Germany 3.6.1.1 Central Umformer-/Umrichterwerke
• 3.6.1.2 Distributed Umformer-/Umrichterwerke

• 3.8.1 Germany
• 3.8.2 Austria
• 3.8.3 Switzerland

History

Because of technically undemanding controllability and high standstill torque, the DC series motor proved to be the ideal drive for rail vehicles. However, such engines can not tolerate high tension and require more higher currents, which in turn require large and expensive cross-sections of the overhead line or conductor rail. If the distance of the breakpoints so it proves to be more economical to supply the locomotives with AC voltage higher and install a transformer. The energy required for his constant Mittransport is lower than it would be losses in the contact line.

The weight of a transformer is mainly determined by its iron core. This, in turn, is approximately inversely proportional to the frequency of the alternating current. Due to the uncontrollable technology in transformer a frequency of 50 Hz in the European networks had prevailed. Due to the resulting brush fire at the collectors, however, failed to operate motors at the required power range with a frequency of 50 Hz. Therefore, traction power supplies came with 25 Hz and 16 ⅔ Hz in order to generate rotating synchronous converters, traction power from the 50- Hz power system, was chosen the divider factors 2 and 3, the use of modern asynchronous converters at an integer division ratio proved to be at high services, however, so that the target frequency of many networks has now been changed to 16.7 Hz as problematic, with 16 ⅔ Hz is within tolerance.

The present state of the art in the field of power electronics makes the reduced frequency of the alternating current is no longer mandatory. Modern vehicles are usually equipped with DC motors with a rated voltage of 6 kV, with a transformer with 25 kV primary voltage and tap at 15 kV, these can be equipped as a multi- system vehicles. A change of the traction current at 25 kV 50 Hz is currently in the field in the DB is not possible since the required safety distance of the overhead line is not added to existing bridges. In new buildings, but greater distances to be scheduled. The balance of Europe-wide standardization of traction power systems in cross-border traffic is a relatively small problem - the additional costs for the transformer in multi-system vehicles are low compared with the cost of the multiple train control systems and the national approval procedures.

Furthermore, the date of a possible conversion of the traction current in Germany is influenced by the life of the older series with AC motors, which can be converted heavy. The 103, 141 and 150 are already retired, under the standard locomotives remain the 110, 140, 139, some of the younger 111 and 151, when the Reichsbahn series 112, 114, 143 and 155 are out of service, remain the property of the Deutsche Bahn only three-phase locomotives. A change is then simply - as a counter value can be omitted Entertainment an independent 110 kV high -voltage transmission system, and the sub-stations can be connected to the high voltage networks of the general energy supply companies. Since the high voltage networks are already established, there is no need for action and the phasing out of the older series can take decades.

Power Systems

Direct current

DC vehicle side, the simplest solution. There is no (heavy ) transformer required. In addition DC motors are smaller for the same power than AC motors, which is favorable especially in confined spaces. The power control of the motors can also pretty easy - albeit lossy - via series resistors through which the motor voltage is regulated.

DC systems are therefore particularly suitable for underground, urban and trams. In subways usually busbars are used because an overhead line would require a larger tunnel profile. Busbars may be operated (typically 500-1200 V) but for security only at low voltages. With trams playing alongside the technically simpler vehicles also safety reasons a role, as a medium voltage overhead wires over streets and between buildings would be too dangerous.

For full tracks direct current networks are less suitable, but still find use in many countries, such as Italy, Slovenia, the Netherlands, Belgium, Eastern Europe, Spain, Southern France, South Africa and Japan (usually 1.5 or 3 kV). The disadvantages arise here from the relatively low voltage: DC motors were previously operated at a maximum at about 1.5 kV; could therefore even with a series connection of two motors not be higher than 3 kV driving voltage. Compared with the case of AC operating voltages of 15 kV usual today or 25 kV, this is a relatively low value, which is why very large currents are necessary for the high performance required for railway operations. This requires a different construction of the overhead line (often multi-conductor ) and the current collectors, or even the use of two current collectors in series.

The conventional power control via series resistors is inferior to corresponding control systems for AC, since it clearly worsens the actually quite good efficiency of electric motors: The resistors heat up and are therefore often located on the roof of vehicles. This disadvantage does not apply to newer vehicles, where with the help of power electronics, DC motors are fed via Thyristor or the DC power is converted to three-phase, so that the simple and robust asynchronous motors can be used. However, falls in modern multi-system locomotives performance under DC generally lower, because the disadvantage of high remains unchanged to be transmitted streams.

The power supply DC -powered lifts done since the 1920s by rectification in fed from the grid substations, where earlier today and mercury vapor rectifier come from semiconductors used. The substations are fed even at full tracks generally from the medium-voltage network.

Alternating current

AC can be used as traction power, as well as for the public electricity supply, easy to generate (generator) and be re-clamped and distributed in transformers.

The power of the drive system is to be distinguished from the power supply. There is a right way to connect any current systems to drive and network with each other side by means of power electronics for every application. With electronically controlled railway vehicles with appropriate inverters, the electrical energy flow can occur in both directions, ie, the vehicle takes during acceleration electrical energy from the power system and when braking the vehicle is part of the electrical energy fed back into the grid.

Single-phase systems

Alternating with standard industrial frequency

Has the world's largest spread of railways alternating with the country-specific mains frequency (usually 50 Hz in the U.S. and partly in Japan 60 Hz).

The operating voltage is usually 25 kV, in the USA ( Lake Powell Railway) and South Africa ( Erzbahn Sishen - Saldanha Bay ), there are tracks with 50 kV.

The advantage of using the standard grid frequency is that a power supply from the mains power source is at least theoretically easy. In practice, however, there is the danger of unbalanced loads in the industrial network. For the avoidance of 20 to 60 km long overhead line sections are connected to the three different phases of the 50 -Hz network. In the catenary phase protection routes are arranged between the catenary sections which are traveled by the trains with momentum and lowered pantograph. 50 - Hz trains can be powered from the electricity grid only at places with the highest network performance, where the unbalanced load is insignificant percentage. Otherwise railway-owned high-voltage lines are needed.

Initially there was a disadvantage that the necessary engines were big and not suitable for high frequency, the AC had therefore to be rectified and needed to power electronics. For power rectifier were needed, a technique which was dominated until the early 1940s. Initially there still mercury arc rectifiers were used; only in the 1960s, semiconductor rectifier prevailed.

The voltage was initially regulated as lower for reduced frequency locomotives variable transformers, later a system of phase angle control was typically used with thyristors.

AC with reduced frequency

In some European countries ( Germany, Austria, Switzerland, Sweden, Norway), the trains run with single phase with an opposite public distribution systems decreased frequency of 16.7 Hz instead of 50 Hz

There are also traction power systems with 25 Hz Even today, the New York - Washington Section operated the East Coast network in the U.S. and the Mariazell Railway at this frequency.

Since AC allows a transformation of the contact wire voltage to the appropriate for the motors voltage, a significantly higher contact wire voltage can be selected as on DC (initially about 5 kV, today in the countries listed at the beginning of Section 15 kV). The transformers were designed as variable transformers (see also step switch for power transformers ) and allow for voltage regulation without using resistors. The weight of the transformers is the factor limiting performance in electric locomotives.

The actions of the public power grids decreased frequency was chosen in the early 20th century, because it was not possible to operate large single-phase electric motors with high frequencies because they can lead by the so-called transformational voltage to excessive sparking at the commutator. For historical reasons, has been working with Maschinenumformern or generators, through the pole pitch of the grid frequency was divided into three portions of 50 Hz, yielded 16 ⅔ Hz as the frequency of the current track. The actual value of the frequency was, however, depends on the constancy of speed of the generator.

When forming the orbital energy by means of synchronous synchronous converters, the frequency of the traction current is in practice exactly one third of the current line frequency of the supply country network. Such converters are among other things in Sweden and in northeastern Germany in operation.

Despite the greater spread of the 50 -Hz system today do not consider the expert 16.7 Hz system as inferior. As already mentioned, the supply of a railway line with 50 Hz from the national grid is not without problems because of the risk of unbalanced load. The reduced power frequency also has the advantage that the reactive power caused by voltage drops only one-third as large. On the other hand, the transformers need to be larger and the substations can not be powered directly from the mains power source. Often completely independent networks will be entertained with traction current lines for this reason. The traction current network allows also to produce the current at the cheapest place or shopping. The poles of this network usually have two pairs ( 2 x single phase).

16 ⅔ Hz vs. 16.7 Hz

The line frequency of the traction power network is, as well as the 50 Hz mains frequency of the European interconnected system held in a certain range of tolerance. The current actual network frequency depends inter alia on the current demand and the current supply of electrical energy and therefore wavering. The tolerance range of 16.7 Hz systems in railway power supply is 16.5 Hz to 17.83 Hz while 99.5 % one year and 15.67 Hz to 17.33 Hz while the remaining 0.5 % a year.

For power balance between the traction power network and the European network, among other converters are used. This is a mechanical combination of two rotating electrical machines, as shown in the adjacent figure, one of which operates as a motor and as a generator. This can be transferred between the various power grids with different grid frequency performance. In the doubly-fed induction machines used therein - these machines are used instead of synchronous machines in order to control the power flow and its direction at the converter can - is a slip necessary. The setting of the power flow by means knob on the running with slip rings rotor circuit.

Since the target value of the mains frequency in the European interconnected grid three times the value of the former setpoint is 16 ⅔ Hz traction power network with exactly 50 Hz, it was in the past especially at off-peak times such as at night cause the necessary for the induction machine slip is zero. In that the synchronous running, it is in the rotor circuit to an undesirable DC component in one phase, which leads to non-uniform thermal load on the engine and may cause the thermal protection operation and an emergency stop in extreme cases.

With a displacement of the reference frequency from the scheme since 1995 by 16 ⅔ Hz to 16.7 Hz now - this corresponds to a deviation of 0.2 % and is within the allowable tolerance range - a small slip in the induction machine is guaranteed even during low-load operating hours. Wherein the slowly rotating DC component is evenly distributed over the stages of the rotor circuit of the slip rings and the brushes in this case, stationary, whereby the thermal load is distributed and local peaks are avoided. It is true that with the new reference frequency of 16.7 Hz at frequency variations briefly an undesirable synchronous operation occur in the machine set, but this is by regulating only a transient event that can not occur as a steady state operation. So that the thermal load on the components of the transducer is maintained within permissible limits.

That exactly 16.7 Hz were chosen, it has no deeper meaning; at too great a shift there would have been problems with locomotives, whose technique is designed for a frequency of 16 ⅔ Hz. The traction power supplies from Germany, Austria and Switzerland, presented on 16 October 1995 at 12:00 clock the desired frequency to 16.7 Hz around. In programs based on power electronics HVDC Kurzkupplungen the conversion of the orbital frequency does not play a role, as in electrically isolated from the remaining rail network sections, which are operated with rotary converters of synchronous machines.

Two-phase systems

Two -phase systems are also referred to as "two voltage systems " or autotransformer system. Such systems can be found in various electrified with 50 Hz high-speed rail lines in France and in Belgium, the Netherlands, Luxembourg and Italy. When driven at 16.7 Hz networks is in Germany only a pilot plant between Stralsund and Prenzlau operation.

Three-phase systems (three-phase )

Phase current, accurate three-phase alternating current, is ideally suited for a railway drive due to the good properties of the three-phase motor, because induction motors are very robust and requires little maintenance because they do not require brushes and based on their performance have a relatively low weight.

Use of externally generated three-phase

Most of the historical applications of the three-phase drive worked with lead multi-pole overhead lines. This was disadvantageous that induction motors can only be operated economically with specific, dependent on the frequency speeds. So therefore may have to be modified at the factory to the power change of the driving speed of the frequency, as long as a frequency conversion on the engine has not been possible. This, however, was suitable only for testing, not for practical operation. Thanks to a special circuit of the motors ( pole changing ) this can indeed be designed for multiple speeds, however, a fine-grained or continuous change as in DC motors is not possible.

Another disadvantage of a three-phase rail system is the need for a three-pole power supply, which one of the terminals requires a two-pole cable with the use of the upper rails. However, this is complicated (especially on switches and crossings ) and prone to failure ( short circuit ).

In fact, three-phase traction power networks therefore found only very limited use: In northern Italy there have been 1912 to 1976 a long time a larger three-phase system (3.6 kV/16 ⅔ Hz). The Gornergrat Bahn (750 V/50 Hz) and the Jungfrau Railway ( 1125 V/50 Hz) drive today with AC, as well as the Chemin de Fer de la Rhune (3 kV, 50 Hz) in the French Pyrenees and the Corcovado mountain railway ( 800 V, 60 Hz).

In the years 1901-1903 there were test drives with three- speed rail cars on a military railway between Marie Felde and Zossen near Berlin. Here, a three-pole overhead line with superimposed wires were used, which were picked off the side. A world speed record of all transportation was on October 28, 1903 there with 210.2 km / h set up, which was only broken in 1931 with the Rail Zeppelin, which reached 230 km / h.

The Passion Play 1900 Ammergaubahn 1899 electrified with AC. After the practical operation failed, the Siemens - Schuckert the power supply and the vehicles 1904-1905 built successfully converted to single-phase AC voltage at 15 Hz.

AC drive with on-board three-phase conversion

By using modern power electronics locomotives can take advantage of the three-phase current in any railroad networks, without having to accept the disadvantages of the additions to the vehicle in purchasing. Voltage and frequency can be regulated steplessly electronically ( frequency converter). This type of drive has now been widely accepted as a common practice. The first locomotive, the single phase alternating current is converted to power electronics on board in three-phase, 1972 was the Versuchslok Be 4/4 12001 Swiss Federal Railways. 1979 followed by the first examples of the class 120 of the German Federal Railroad. There was locomotives where the deformation of board performed with rotary converters.

Power supply

Generation and distribution of electric energy

Paths, which are operated with alternating current whose frequency differs from that of the public network, obtain their energy either from the conversion of other sources of energy in a train engine or through frequency conversion in so-called converters or switching stations from the public power grid. Here, the supply on a railroad networks ( centralized) or a decentralized supply based. The control of the assets were previously largely in the systems themselves Today, power generation and control of the systems are separated.

Traction power network

For reasons of network availability and reliability of the traction power supply for traction and the ancillary facilities are usually kept separate. In addition, the European network largely uniform with frequency of 50 Hz is not compatible with all networks of the traction supply, and their different frequencies.

Central Supply

In a traction power network with central supply the traction power is generated in power plants. The transport of energy to the railways is realized via rail power lines to the sub-stations on the railway line. In the factory, the voltage of the power line path is optionally transformed in a trolley wire voltage and fed to the overhead line. The traction current network therefore allows to transport energy without frequency conversion in other regions. The inverter or Umformerwerke used here are called because of their use in the power generation network as a central inverter or Umformerwerke. The control of the switching took place earlier in the power generators or in small remote control units and is now carried in control centers. The disadvantage of this construction is that in case of failure of a supply unit, the whole network may be affected. Traction power supplies are available in Germany, Austria and Switzerland ( 16.7 Hz), these are also connected to each other. Also the route New York - Washington ( 25 Hz ) and the Mariazell Railway (25 Hz) have a traction power network.

Decentralized supply

In the decentralized structure of the energy supply from the public network takes place. The sub-stations at the entry points have static converter or rotary converters, in which the voltage and frequency of the general power grid is transformed into the traction power (decentralized inverter or Umformerwerke ). In principle, the supply would also be possible by a nearby train power plant.

The main difference to centrally supplied traction power network is that the Umformerwerke be connected in particular for phase synchronization only on the top line with same Umformerwerken parallel. Separate power lines or railway traction power supplies are not present here. This is practiced in Sweden, Norway, Brandenburg, Mecklenburg -Western Pomerania and parts of Saxony- Anhalt. The control of the assets are in the control centers.

Voltage levels at railroad networks

As in the public power grid, there are several voltage levels, a high voltage level and a medium voltage level. The high voltage level is used in Germany and Austria with 110 kV, in the area of the Vienna S -Bahn with 55 kV and is used to transport the traction power of the railway power plants to substations. Sometimes they hang on poles which carry also circuits of the public power network. In Switzerland there are two high voltage levels (132 kV and 66 kV) with virtually equivalent function. The in all three countries operated with 15 kV medium voltage level corresponding to the contact wire tension and serves to supply the locomotives the traction power on the overhead line. Deviating from the standard, the contact wire voltage is in the narrow-gauge Rhaetian Railway network and the Matterhorn- Gotthard -Bahn for historical reasons only 11 kV.

Application Examples

A private railway power system with single-phase 25 Hz, the Mariazell Railway. In this path, the tension in the mounted to the overhead line masts conductor cables of the traction current lines 27 kV and 6.5 kV in the catenary is.

In the U.S., some stretches of the former Pennsylvania Railroad between New York, Philadelphia and Washington are still operated with single-phase reduced frequency ( 25 Hz, although the frequency of the power distribution network in the U.S., 60 Hz ), where only the passenger with electric traction wrong. These tracks have their own high-voltage grid, the conductors of the web -current, high -voltage power lines are usually mounted on the overhead line masts here.

Italy possessed for the supply of its electrified with AC lines ( 3.6 kV 15 Hz ) in Northern Italy through a run with 60 kV traction power network, which was fed from hydropower plants and a thermal power plant. For the supply of the catenary and mobile substations were used.

For paths that go with single-phase from mains frequency or DC power needed for operating energy required in substations by concatenating the phases of the three-phase system (in the case of AC railways ) and with rectification is obtained (in the case of DC railways ). Dedicated traction current lines exist only sporadically in these cases.

Railway power plants

A railway power plant is a power plant that generates traction power. While the Austrian Federal Railways operate nearly pure Railway power plants are those in other countries, such as in Germany, rather rare. Far more common are power plants, in which both industrial power generators, as well as traction power generators are located. Railway power plants are designed as hydro, conventional thermal power plants and nuclear power plants. Wind and solar power plants have not been implemented for the sole production of traction power.

The traction power generators for alternating current with reduced frequency are significantly larger than that for the public power grid, the associated turbines are special.

Germany

Power plants in Germany, which serve all or part of the traction current generation:

Existing hydropower plants

• Pumpspeicherwerk Langenprozelten
• Power plant Bertoldsheim
• Power plant Bittenbrunn
• Kraftwerk Bergheim
• Power plant in Ingolstadt
• Power plant Vohburg
• Railway power plant in Bad Abbach
• Power plant in Santa Maria
• Kraftwerk Eitting
• Power plant Pfrombach
• Saalachstrasse power plant in Bad Reichenhall
• Walchensee to begin construction in 1918, completed in 1924 for the electrically operated railway lines in Bavaria
• Gone hydropower plant Kammerl, built from 1897 to 1899, after replacing the generators 1905 5500 V AC 16 Hz in operation

Existing nuclear power plants

• (Community) nuclear power plant Neckarwestheim, block 1 ( GKN -1 ) with additional traction power turbine and block 2 ( GKN -2) with coupling via frequency

This part of the traction power supply is different from the current advertising strategy of the DB AG, no "green traction power " within the meaning of the general term understanding.

Existing thermal power plants

• Large-scale power plant in Mannheim
• Power plant dates
• Lünen power plant
• Kraftwerk Schkopau
• Power plant Kirchmöser
• Power plant Dusseldorf - Lausward

Furthermore, there are connections to the power plants of the Austrian and the Swiss Federal Railways, can be exchanged via the electrical energy with the German railway power network.

Former plants

• Power station Hamburg- Altona suburban railway, built in 1906 as the first railway power plant in Germany, now abandoned.
• Railway power plant Muldenstein, built in 1912 as the second track power plant in Germany for the railway line from Magdeburg Dessau and Bitterfeld to Halle, now abandoned.
• Railway power plant means stones, erected in 1913 as the third rail power plant in Germany for the supply of the Silesian network in 1945 dismantled as reparations
• Power plant in Stuttgart-Münster, 1933, taken a traction power machine to feed the newly created railway power line from Munich to Stuttgart and the Stuttgart suburban services in operation ( the year of retirement unknown)
• Railway power plant Penzberg, 1951-1971, steam power plant with coal fired.
• Block 1-3 in the power plant Mittelsbüren; Blast furnace gas power plant with traction power machines. Unit 1 was shut down in 2002, 2004 Block 2, Block 3 at Easter 2013.

Austria

The Austrian Federal Railways produce their traction power for the most part, the energy itself is (mostly hydropower ) won at present to 93 percent from renewable energy sources. Six percent of the energy is purchased from wind power and biomass. Moreover, negotiations were held about possible investments in wind turbines. In 2010, talks were confirmed and cited as potential sites Burgenland of wind turbine manufacturer Leitner. In Burgenland, the Austrian Railways currently has no facilities to generate electricity.

Railway-owned power plants

All railway-owned power plants are unoccupied operated and controlled by the main control center of Innsbruck and monitored.

Train foreign power plants

Switzerland

In Switzerland, the traction power is derived in part from power plants SBB and from other power plants.

Power plants of the SBB

• Etzelwerk
• Massaboden
• VERNAYAZ
• Châtelard Barberine (Lac d' Emosson )
• Amsteg
• Ritom

Power plants with SBB participation

• Rupperswil - Auenstein
• Göschenen
• Wassen

Alien plants

• Gösgen
• Hang about
• Muhlenberg
• Klosters ( RhB)

Umformer-/Umrichterwerke

The interface between the public high - or high-voltage grid and the web -current, high -voltage grid forms a Bahnstromumformer or Bahnstromumrichterwerk. While three-phase AC are common for the public high-voltage grid at voltages such as 220 kV or 380 kV and a frequency of 50 Hz, lead track current, high- voltage grids everywhere only an AC phase, in Germany, Austria and Switzerland, the frequency 16.7 Hz and voltages of 66, 110 or 132 kV are common. In addition to the now considered to be stricken converters, in which the networks are mechanically coupled between the generator and the motor and rotating masses between the two power systems, systems are used without any mechanical parts in Germany since 2002, which convert electricity alone with electronic components. In this case one speaks of inverters. The Umformerwerke be successively replaced by Umrichterwerke.

Bahnstromumformerwerke in Germany

Central Umformer-/Umrichterwerke

Distributed Umformer-/Umrichterwerke

The following Umformerwerke come from the large part by forming from the 50 Hz national grid directly powered network of the Deutsche Reichsbahn and were first in three shifts in two-man cast, later a one-man cast, and operated remotely controlled in part from the mid-1990s. The Umrichterwerke come recently, and they increasingly replace or be Germany's newly built.

Bahnstromumformerwerke in Austria

From the ÖBB Infrastructure AG following Umformerwerke be operated:

Bahnstromumformerwerke in Switzerland

In Switzerland, there are eight Bahnstromumformerwerke, one is under construction. These are:

• Rupperswil
• Seebach
• Brodhüsi
• Kerzers
• Giubiasco
• Massaboden (plant converters )
• Grafenort (eg, in construction)
• Bever (RhB )
• Country Quart ( RhB)

Substations ( Uw )

A sub-station is about one substation in the public network. A substation transforms the energy from the high-voltage grid in the overhead network.

It AC substations are used to generate the power at frequencies of 16.7 (DB, SBB and ÖBB), 25, 50 or 60 Hz and voltages between three and 50 kV. In Germany and Austria substations are only responsible for the change in voltage. In the language Umformerwerke therefore often referred to as substations, which, however, is only a generalization. It AC substations are used to generate electricity at voltages of between three and 50 kV.

In a traction power substation, DB, SBB and ÖBB is single-phase from the high- voltage grid ( see above), of 132, down transformed 110 or 66 kV for feeding into the contact wire at 15 kV, the frequency of 16.7 Hz does not change.

In Germany, Switzerland and some other countries, mobile substations ( FUW ) are used. They are so constructed that they can be moved without major adjustment via the rail network to another site.

In Switzerland ports are in different places prepared to the high-voltage grid, so that the mobile substations with special needs (Revision of solid works, temporary traffic bulk ) can be moved to other locations. The SBB currently has 18 mobile base stations, consisting of a four-axis command car and eight-axle transformer cars, in inventory.

In substations for DC railway (S- Bahn Berlin and Hamburg, trams, metros, industrial railways in mining ), the three-phase AC voltage of a public or railway-owned power grid current is rectified by a rectifier into DC voltage. For this purpose are silicon diodes can be used. Earlier this rotary converters and water-or air-cooled mercury arc rectifiers were used.

To avoid electrolytic corrosion and bias of AC systems due to stray DC currents of the device connected to the same time serving as a return line railroad terminal of the DC voltage along the tracks is electrically isolated from the ground and only the sub-station via diodes or directly with non-system grounded parts (eg water pipes ) connected. The top line is usually positive, so that always builds only a positive potential of the tracks opposite the Earth along the rail line due to the load current. Thus, the electro-corrosion remains on the rails themselves limited and does not damage non-system lying in the ground metal parts. At high potential differences between the return line and ground -automatic, so-called grounding Earthing apply.

Management of railway networks

The operation of the traction power supplies is monitored as with all other electric power supply networks of one or more control centers. These contribute depending on the country and also from a historic point of different names such as load balancing, network control center, central switching etc. The control centers have among its tasks to monitor the switch status of the networks, to secure through planned switching operations and switching actions in case of failure of supply, predictable circuits coordinate from the point of supply.

Germany

The top central switching point ( CECS) of DB energy is located at the company headquarters in Frankfurt / Main. There are 18 regional central switching stations (as of 2008 ) in the network of the Deutsche Bahn. The most advanced computer-controlled ZES are located in Berlin, Leipzig, Borken ( Hessen) and Karlsruhe.

Austria

Central station Innsbruck Already in 1925, for receiving the electrical operation of the Arlberg railway, the load distribution in Innsbruck was put into operation for receiving the composite operation of power plants Spullersee and Schoenberg. This had the task to control the electricity to control the synchronization of the individual power plants and to ensure the supply of substations with the required traction power.

Since August 1998, the load distribution ( central station Innsbruck) is housed in one of the most modern control room in Europe. From here, the machines use the force and is Umformerwerke according to the load situation in the rail network are centrally controlled and optimized through online programs. Also monitored by the control center of Innsbruck all 110 kV and 55 kV transmission lines of the ÖBB railway power network and made ​​the necessary circuits. The control of work assignments, or switching operations in the event of a fault to fault isolation and recovery care for all Austrian transmission lines are thus in one hand. When outages of power plants or power lines caused by natural events ( heavy rainfall, storms, avalanches ) so that large-scale supply bottlenecks can be prevented by early intervention. In addition, necessary measures such as suppression orders to the responsible employees (outside of normal working hours to the call ), operating limitations, energy schedule changes can be done in the fastest way.

Regional control centers In addition to the main control center of Innsbruck, ÖBB has installed four regional control centers. Their task is to make the load balancing among the 56 sub-stations.

Switzerland

The central network control center ( ZLS) SBB is operated by the Energy Division of the Infrastructure Division in Zollikofen. From there, the power plant and almost all Umrichterwerke can be remotely controlled.

Power consumption and origin of Deutsche Bahn

The power consumption of the Deutsche Bahn AG was at around 2012. 12,000 GWh. Compared to last year he was almost unchanged. The traction power came from to 45 % from coal power plants (mainly coal ), 22% from nuclear power plants to also 22 % from renewable energy sources ( half water power plants, which cover about 12 % of electricity ) to 9% from natural gas plants, and 2% other installations. This mix is nearly exactly the national average in the shares of coal and nuclear power. The share of electricity from renewable energy sources is slightly higher than the nationwide average due to the higher proportion of hydroelectric power plants. Accordingly, the lower the share of gas-fired power plants. In 2011, the German Bahn AG 275 GWh of electricity from renewable energy sources for bought to " the green DB offers" in addition. (2.5% of total consumption).

The costs of electricity in the years 2011 and 2012 according to the annual report of the Deutsche Bahn AG almost the same at around. € 1.05 billion have been - like the almost remained the same consumption. In total expenditure of approx. € 37 billion. take the cost of electricity 2012 accounted for nearly 3% of the total expenditure of the Deutsche Bahn a.

The cost per kilowatt hour of electricity was for the German Bahn AG, 2012 at 8.75 cents / kWh (expenditure of € 1.05 billion for the electricity consumption of 12,000 GWh). By comparison, the price for industrial electricity was 2012 in Germany on average approx. 13 ct / kWh.

Traction power and EEG apportionment

With the current EEG the German Bahn AG is mostly exempt for electrical generation of the EEG apportionment, because energy-intensive manufacturing industries and railways are to be protected in its international and intermodal competitiveness through a special compensation scheme. Due to these regulations (EEG 2012 § 40 with associated regulations § § 41-44 ) is calculated on the current reference only to 1 GWh / a, the EEG apportionment in full. 10% of the EEG levy are payable for the current portion 1 to 10 GWh / a. 1% of the EEG apportionment shall pay for the electricity share of between 10 and 100 GWh / a. The power-generating systems are exempt from the EEG apportionment.

According to the power supply of the DB energy is called EEG surcharge is a surcharge of 1.0 cents and 0.1 cents per kWh ( with approved hardship application under EEG 2012 § 40; ff ) levied.

Beginning of 2013 were the " energy price brake" as an amendment proposal by Environment Minister Altmaier both schemes - partial exemption from the EEG surcharge for electricity-intensive companies and liberation of the power-generating systems - for discussion. The German Bahn AG saw himself in their implementation burdened with additional expenses of 500 million euros, of which 137 million euros would be caused by the possible elimination of impaired EEG apportionment and 350 million euros by the possible introduction of the EEG surcharge for self-generated electricity.