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Monitoring overhead lines

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Delivery of energy to rolling stock through high-voltage overhead lines is the predominant distribution method used on many of the world’s railways. Indeed, this has become the primary choice, particularly on high-speed, high-profile routes. Ensuring consistent contact at the interface between the pantograph on the train and the overhead line is of fundamental importance to almost every aspect of operation. If this contact is broken, so is the energy supply.

Deutsche Bahn’s ICE-S test train is fitted with a system for contact wire inspection very similar to that which will be used by Network Rail (DB/Hannes Frank)

To ensure a reliable energy supply, where the carbon strips are in constant contact with the overhead wire, it is important that the pantograph and overhead line specifications are appropriately matched. Furthermore, ensuring that the equipment performs as specified, day in – day out, is of fundamental importance in ensuring smooth and safe running, minimising the costly delays of overhead line (OHL) failures.

Simulation and monitoring

Determining conformance with the design requirements is the first stage of ensuring continuing correct system performance.

The initial stage is to perform a simulation of the whole system – train and infrastructure. European standard EN50318 covers simulations of the dynamic interaction between pantograph and overhead line and such a simulation will provide confidence that the current collection system will perform as designed.

At this stage, it is also possible to determine the worst-case vehicle configuration. Normally, for multiple units, this usually happens to be when units have been coupled together, resulting in two pantographs being in close proximity. It is possible to define a homologation test strategy for the system and the expected vehicle configuration.

Firstly, the test pantograph needs to be suitably instrumented and its ‘measurement system’ calibrated according to European standard EN50317. In Germany, DB Systemtechnik (DBST) does this in its laboratory in Munich, which houses its calibrated test rig.

The test rig in DB’s Munich laboratory (DB)

During homologation testing, according to the requirements of various TSIs (technical specifications for interoperabity), including ENE (energy), LOCPAS (locomotive and passenger) and European standard EN50367, on-board engineers monitor the interaction of the pantograph with the overhead line. This testing normally starts with test engineers being located at a test track in mainland Europe, followed by specific route testing in the country concerned. So for the UK, for example, DBST and ESG Rail have been supporting Hitachi Rail Europe with the testing and commission of its new trains for the Intercity Express programme, and this has involved pantograph and OHL testing.

Contact forces, accelerations, height and stagger are all monitored, and it is normal to include a speed and location system to ensure that the location of the captured data is accurately recorded.

Engineers monitor the interaction between the pantograph and overhead line. As part of the testing, they also determine the contact forces between the pantograph and overhead line, as well as the aerodynamic performance in each direction of travel and the directional flow.

A test pantograph similar to the one which will be used on the MENTOR test coach (DB)

In-service trains

The same technologies can be deployed, in a very similar manner, on passenger trains in service, albeit the equipment is capable of unattended operation without the requirement for operator intervention.

This provides a wealth of monitoring data, on a daily basis, simply as a consequence of passenger operations. Collected data is transmitted off-board for data interrogation and analysis purposes.

Occasionally, the system’s video image capture and analytics capability is also required. This involves the addition of high-resolution cameras and lighting to enable the system to operate in poor light conditions and at night. The additional benefit here is that the operator gets to make use of analytics software that provides additional data and analysis and is capable of identifying infrastructure anomalies.

The illuminated pantograph on the ICE-S test train in Germany (DB/Matthias Vogt)

The true benefits of this monitoring lie in the early detection of vulnerabilities in the catenary system, providing warnings of impending infrastructure failures. This leads to:

  • Fewer incidents, leading to improved safety;
  • Avoidance of costly and time-consuming repairs to infrastructure and trains;
  • Improved passenger services and confidence.

One of the most important benefits, and one that is often overlooked, is the ability to ‘learn’ from such events by understanding the root causes of any incidents. Knowing this is essential to the elimination of future and repeat failures of the same type.

New contract

At the beginning of November, ESG Rail announced that it has received a new contract from Network Rail for overhead line monitoring. DBST will provide the overhead line monitoring equipment, which has the capability to measure a number of interface attributes, most notably contact force, as well as contact wire height and stagger (lateral alignment). There are also a number of other supporting data channels that will be collected during operation.

Initially, the focus will be to deploy two monitoring systems onto Network Rail’s Mobile Electrical Network Testing, Observation and Recording (Mentor) test coach.

Network Rail’s asset information services team is responsible for monitoring the condition of the UK’s railway infrastructure and reporting condition exceedances to the route asset managers and maintenance teams. This delivers compliance with standards and supports maintenance planning for safe network operation. Network Rail has a number of dedicated vehicles deployed across the network on a periodic basis, with Mentor dedicated to overhead line monitoring.

Following the fitment on Mentor, ESG Rail will then install a single system onto a Class 390 Pendolino unit to cover a specific area of the network. This system will provide data on a daily basis, via normal passenger train service operation. The regular collection and assessment of asset condition data will support Network Rail’s ambition to move towards a ‘predict and prevent’ maintenance approach.

Kevin Hope, principal engineer – mobile monitoring, explained: “As well as enabling a transition to more predictive maintenance regimes, this contract is the starting point for Network Rail’s strategy to use in-service passenger vehicles to make dynamic measurements of the overhead line at 125mph – something that isn’t possible using just Mentor, which is limited to 100mph. In addition, the use of EN compliant systems will also enable commissioning of new OLE infrastructure in accordance with the TSI.”

The monitoring system will measure the force between the contact wire and pantograph carbon strips, via high fidelity sensors mounted directly to the pantograph head. All sensors will be subject to a thorough calibration process at DBST’s laboratory in Munich, Germany, before they are deployed in the UK.

The programme will see the Mentor systems operational towards the end of 2019, with the Class 390 deployment scheduled for a few months later. While all three systems will be fundamentally the same, additional equipment will be fitted onto the Class 390 unit to allow for the tilting capabilities of this fleet.

Commenting on the importance of this new arrangement, Nick Goodhand, managing director of ESG Rail, said: “One of the key infrastructure to vehicle interfaces is the contact between the overhead line and the train’s pantograph. Because traction energy is supplied via this interface, on-going, correct operation is essential for maintaining service performance. Failures at this interface can be catastrophic, with extensive service disruption and significant financial consequences.”

“So this is a landmark project, and we recognise the important role that ESG Rail and DB Systemtechnik will play in supporting Network Rail’s asset management team.”

Written by Martin Loibl and Kevin Dilks of DB Systemtechnik/ESG


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