Rolling stock type approval tests for greater safety
Railway signalling systems are complex. Their role is to transmit information automatically to the train driver so he can adapt his driving techniques to circumstances and thereby work his train in complete safety. Signalling systems are therefore designed to overcome the dangers inherent in rail vehicle movements.
It is therefore necessary, when submitting rolling stock to type approval, to take account of interference that could be created by the electrical systems used on the particular vehicles and ensure that this interference will not affect the signalling systems on the lines over which these vehicles are likely to run.
These tests must be carried out on new rolling stock or on existing rolling stock to which alterations have been made that could impact on the interference phenomenon.
On-board COFRAC measurement of interference currents
The LEM can boast sophisticated test equipment that can be adapted to all types of rolling stock. With this equipment and its knowledge of the railway environment, the LEM is in a position to carry out COFRAC measurements on interference currents up to 20 kHz (*) on all urban transport networks with d.c. traction current supply, in accordance with standard EN 50238 (§6) of May 2003.
(*)LEM test resources are also suitable for non-COFRAC measurements up to 1 MHz.
For a number of different static and dynamic configurations defined in the standard, interference currents are measured in the supply cables, at the point of current collection (“+HT”») and at the train’s negative return current circuit (“-HT”).
Further measurements may also be taken on the different power devices on the train (static converter, traction and braking equipment, etc.) to try and identify the sources of the interference currents and also obtain a clearer understanding of the circuits formed by this interference in the bodywork of the train.
This data is then computer processed, using a selective voltmeter-type analysis, to establish the maximum current level measured for each test configuration and for each track circuit frequency on the line considered.
It is also possible to carry out a weighted analysis in relation to the power in fact “picked up” by the track circuits. In order to do this, it is first necessary to establish the characteristics of the track circuits.
To simplify the task of analysing results, the LEM is also able to conduct a whole series of other measurements on a parallel to those on interference current (current intensity, voltage, speed, traction/braking information, static magnetic field, etc.).
The levels (raw and weighted data) measured by the LEM may then be easily compared with templates in order to complete the type approval process.
Ground-based measurements for a better understanding of the interference current phenomenon
Sometimes measurements conducted on board are not enough to establish the exact path followed by the interference currents. These currents may, for example, simply complete a loop within the train bodywork without ever returning to the rails (or rollways).
For this the LEM has developed a system for measuring interference current in the rails (or rollways). These measurements are easily performed using the same approach as for on-board measurement. With this technique results can be more easily analysed and the paths followed by the interference currents measured on rolling stock better understood.
Know-how at the service of all urban rail transport networks
For a number of years the LEM has been conducting measurements on interference currents in rolling stock for a number of rail vehicle manufacturers and urban transport companies.
In practice, the LEM is able to play this role for all urban transport networks fed by d.c. current (750 volts, 1,500 volts, etc.) and for all types of railway rolling stock (metro, light rail, trams, etc.).
The following are some of the test campaigns recent carried out by the LEM
- MF2000 (Client: ALSTOM)
- M3-M4 (Client: STIB)
- M5 (Client: STIB)
- M6 (Client: STIB)
- MI79R (Client: ALSTOM)
- MP89 (Client: RATP)
- MP05 (Client: ALSTOM)
- MI09 (Client: ALSTOM)