Overcurrent limitation

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Overcurrent limitation is a limitation of the maximum current that electric traction vehicles can accept in the feed area of ​​a substation . Since the contact wire tension (in the mainline system from Germany, Austria, Switzerland, Sweden and Norway 15  kV ) must be considered within acceptable tolerances as constant, with the upper current limit and the maximum power is limited, the electric locomotives and electric railcars in traction power to implement can.

The current taken up by an electric traction vehicle from the overhead line via the pantograph and fed to the primary side of the main transformer is referred to as the overcurrent .

realization

In older electric locomotives, the maximum current consumption had to be monitored by the driver using the overcurrent ammeter . If the current consumption approached the upper current limit, he had to turn down the drive switch. With some vehicles, the driver can now enter the upper current limit in the on-board computer. In Germany, the linear train control or ETCS on upgraded and high- speed routes can enable higher speeds than the 160 km / h permitted with PZB . In both cases, the vehicle technology automatically monitors compliance with the upper current limit.

Due to the linear tension control, up to 1000 A upper current can be released, with CIR-ELKE (I) up to 1500 A.

ETCS

With the 10-bit variable M_CURRENT, ETCS allows the release of 0 to 10,000 A (in 10-ampere steps) and the release of any overcurrents.

The overcurrent limitation per train or pantograph are 2 of 15 properties that describe a national traction system (using the NID_CTRACTION variable ) in ETCS. The traction system, in turn, is one of three properties that a train has to meet in order to travel a route , along with the loading gauge and the axle load . If at least one property required by the infrastructure does not match the train, the travel permit should be shortened to the beginning of that section of the route and the driver should be informed. The list of traction systems permitted for the vehicle cannot be changed by the driver and is transmitted from the train to the infrastructure after the connection to the RBC has been established . A total of 39 such systems are described in the list maintained by the European Railway Agency.

Pending changes in the traction system ( NID_CTRACTION ) are announced together with the associated voltage ( M_VOLTAGE ) by means of the ETCS package 39. The announcement of the permissible overcurrent ( M_CURRENT ) takes place by means of the ETCS package 40. The two properties are 2 of 15 types of track conditions that can be defined in ETCS . If no such information is transmitted, the traction system or overcurrent limitation on the vehicle remains unchanged.

Effects of the upper current

Operational Impact

The limitation of the maximum energy conversion influences the acceleration or start-up behavior of the trains , as most of the energy is used for this. The overcurrent limitation also limits the achievable speed of the train. This maximum speed depends on the absolute upper current limit as well as the train load, the inclination conditions, the curve radii and the wind. If the overcurrent limit is in place, the trains start up more slowly, may not reach the otherwise permissible speed and thus occupy track and route sections longer. In addition, overcurrent limits can reduce the permissible tensile loads.

On the other hand, overcurrent limits prevent the entire feed area from being switched off due to overload when too many electric traction vehicles are traveling. A shutdown would mean that no trains could run in the feed area for a short time, regardless of which locomotive ultimately contributed to exceeding the maximum feed current of the substation.

Inductive and capacitive influence

The current strength that flows through the supply and overhead lines as well as rails and the ground (as return current ) influences capacitively and inductively overhead lines and cables running in the vicinity. This can e.g. B. in telecommunication lines and cables to disrupt the low-energy telecommunication flows, so to disrupt their transmission. This applies to telephone, TV, radio, mobile phone, data u. a. Links.

Rule limitation

purpose

The maximum current is specifically defined for the individual railway lines . The starting point is the maximum desired performance for the trains on this route, which is determined by the maximum speed, the maximum load, the inclination and curve conditions, etc. a. results. Basically, the higher the maximum traction current , the higher the short-circuit current of the system. Once the maximum traction and short-circuit current has been determined, the systems and components of the railway power supply, the overhead line , the earthing and the return current must be dimensioned accordingly.

At the same time, one must derive the influence of telecommunications and control systems running in the vicinity and dimension their shielding resistances against inductive and capacitive influences from the maximum traction and short-circuit current.

Upstream classes per train at DB AG

The overcurrent limitation in the Deutsche Bahn network (excluding S-Bahn lines) is (as of 2000) 600 A. 1000 to 1500 A are permitted on high-speed lines , and 900 A as a rule on upgraded lines .

1 - up to 600 A for all trains (generally passenger trains with max. 160–200 km / h)

2 - up to 900 A for high-speed passenger trains (generally max. 160-230 km / h) and 600 A for all others

3 - up to 1200 A for high-speed passenger trains and 600 A for all others (class 3 is currently not used at DB AG - as of 2007)

4 - up to 1500 A for high-speed passenger trains (generally max. 230-300 km / h) and 600 A for all others

5 - Overcurrent limitation in specific special cases

Type of overcurrent limitation

Overcurrent limitation in time-limited exceptional cases

An overcurrent limitation is also necessary if

  • Work or malfunctions in the feed area cannot guarantee full feed,
  • Substations show insufficient energy performance or
  • too many customers ( electric locomotives, electrical point heaters , train preheating, etc.) are operated in the feeding area.

In such cases, the driver is informed separately by La entries or orders .

history

The catenary systems of the existing German network that were created as part of the electrification were designed for overcurrents of around 400 A per train and maximum speeds of 140 to 160 km / h. In the second half of the 1960s, the power requirements for double- traction freight trains and the new class 103 locomotives increased significantly. For feed-related reasons, to avoid influencing signaling systems and to protect the new high-performance locomotives, the permissible overcurrent was limited to 600 A per train.

Class 420 multiple units, which were used for the first time at the 1972 Summer Olympics, required 1050 A overhead current as a long train (three coupled units) when starting and accelerating and required extensive adaptation measures to the contact line systems and substations.

The new Wolfsburg – Berlin line was designed for an overcurrent of 1500 A per train. After a test carried out in 2001, the overcurrent limitation on the new Mannheim – Stuttgart and Hanover – Würzburg routes was to be increased to 1500 A. Nevertheless, only 1000 A are released via the linear train control .

The high-speed routes Cologne – Rhine / Main , Nuremberg – Ingolstadt , Ebensfeld – Erfurt and Erfurt – Leipzig / Halle also allow 1500 A. This means that the full power of the ICE 3 multiple units can be used even when double units are operated.

Individual evidence

  1. ↑ a b c Electrical operation at Deutsche Bahn in 2001 . In: Elektro Bahnen , issue 1-2 / 2002, p. 17.
  2. ↑ ETCS specification, subset 026, version 3.6.0, section 7.5.1.62.1.
  3. ↑ a b Assignment of Values ​​to ETCS variables. (PDF) ERA_ERTMS_040001. European Union Agency for Railways, December 12, 2019, pp. 6, 26 f., 42, 46–72 , accessed on June 1, 2020 (English).
  4. ↑ ETCS specification, subset 026, version 3.6.0, section 3.12.2.
  5. ↑ ETCS specification, subset 026, version 3.6.0, section 3.18.3.2.2
  6. ↑ ETCS specification, subset 026, version 3.6.0, section 3.18.3.4
  7. ↑ ETCS specification, subset 026, version 3.6.0, section 7.4.2.8
  8. ↑ ETCS specification, subset 026, version 3.6.0, section 7.4.2.8.1.
  9. ↑ ETCS specification, subset 026, version 3.6.0, section 3.12.1.3.
  10. ↑ a b c Electrical operation at Deutsche Bahn in 2000 . In: Elektro Bahnen , issue 1-2 / 2001, p. 12.