RAIL E-SSENTIALS

Your regular update for technical and industry information

Your regular update for technical and industry information

Keeping rail safety on the right track

The future development of rail transport is being shaped by the rising demand for passenger and freight capacity, alongside rapid global urbanisation and digitisation. While innovative technologies are having positive impacts, the rail industry must rise to the associated challenges and complexities they bring, while appropriate new testing techniques must be developed.

Before new rail vehicles can be approved for service, they must undergo type testing in accordance with the mandatory regulations. Dynamic running tests, performed by third-party external test centres and evaluated by independent inspection bodies, are therefore an indispensable element of the approval process. Manufacturers and operators can then be assured that trains run safely, do not damage tracks and remain safe at speeds up to the permitted maximum.

The good news for the rail industry is that standards, such as EN 14363:2022, state that the data gained from simulation can be used to replace some conventional measurement data. This may reduce the duration of cost-intensive on-track tests that are designed to ensure that the train does not derail, causes displacement or other overloading of the track. Simulations can therefore be used to ensure that driving dynamics are optimised early on in the development process, helping save both time and costs.

When it comes to track testing, the route sections of the rail network operator that are required for tests must be selected and evaluated early on. An ideal test track includes both straight sections and numerous curves of varying radii, and the exact characteristics and the minimum length will depend on the rail vehicle’s approval parameters.

 

Norwegian high-speed train tests

RailAdventureThe operational handling of the testing of a Norwegian high-speed train was carried out by the Munich-based rail test runs specialist, RailAdventure. This very special test is an example of how the characteristics and minimum length of a test track depends on the approval parameters of the rail vehicle under test.

In this case, the train needed approval for a maximum speed of 245 km/h, meaning that it had to navigate curves with radii of less than 3,000 metres at a speed of approximately 270 km/h. However, although a suitable track in Germany was identified, with curves that had the radii required by the appropriate standards, the overhead line system was only approved for a maximum speed of 230 km/h. High speeds can significantly impact the pantograph’s contact force and the uplift of the contact wire, with an excessive increase in uplift potentially damaging the overhead contact line. To add to the complexity, the Norwegian train exceeded the German vehicle gauge, had a narrower pantograph head and did not have on board train safety equipment compatible with German signalling systems.

To ensure that the test runs could take place, RailAdventure worked in close collaboration with TÜV SÜD and the rail network operator to develop a concept that proved it was safe to exceed the maximum permitted speed.

 

Test process

In a first step, the test experts from TÜV SÜD carried out simulation analyses to evaluate the interaction between the pantograph and the overhead contact line. Based on the results, a comprehensive safety concept was developed for this special test and agreed with the network operator. Once the green light had been given for the on-track test, they then had to ensure that the uplift of the contact wire remained within tolerable limits. As uplift is determined by taking stationary measurements at a few points along the route, the selected points had to be representative of the entire route. The experts therefore used data from a catenary measuring vehicle that regularly inspects the entire line and uses the most critical points identified in the process to monitor the uplift. The experts then optimised the pantograph so that the forces occurring at 270 km/h were identical to those during regular running at 230 km/h.

Consequently, pantograph behaviour was optimised so that the contact wire uplift remained within the permissible limit, even at the most critical point along the route. As a further safety measure, the test runs were undertaken in single traction with a single pantograph, thus minimising the wave motion of the overhead contact line compared to a run conducted with multiple raised pantographs.

The running tests were then performed on the selected route. After initial runs at the maximum speed permitted on the route (230 km/h), the test experts gradually increased velocity up to the train’s maximum speed of 270 km/h, while closely monitoring the values measured at the rail and overhead line contact points.

The values measured revealed that at lower speeds, the contact force now fell short of the minimum values defined in the standards. However, this was necessary and intended for this very special application. This meant that the pantograph’s normal operation settings were readjusted to ensure compliance with all approval-relevant limit values. The special aerodynamic optimisation of the pantograph proved particularly critical for ensuring the force between the contact strip and the contact wire was set precisely for the test runs.

The end result was that all required on-track tests were successfully completed, without exposing the pantograph, overhead contact line or route itself to excessive loads or damage. Despite initial findings at the start of the test programme, suggesting that a suitable test route could not be found, the Norwegian train was successfully approved.

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