City, University of London and Brecknell Willis

City, University of London and Brecknell Willis


This initiative highlights the technological breakthrough made by City University London in collaboration with Brecknell Willis, specialists in railway electrification, by successfully instrumenting a railway current-collecting pantograph with an optical fibre sensor system for real-time monitoring of its contact condition with the overhead line electrification (OLE) system.
The pantograph operates in a particularly harsh environment, being exposed to all weathers as its carbon strip rubs along the OLE at speeds up to 125 mph and at 25,000 volts conditions: monitoring its condition in real-time has posed a real technical challenge.

There are some measurement systems available by using multiple strain gauges and accelerometers, however their power delivery and data transmission require a careful insulation under such a high voltage condition. This limitation could lead to some extreme scenarios, such as dewirement, thus causing a widespread traffic disruption.

This innovation aims to address the above challenge by exploiting the ideal insulator nature of the optical fibre itself: it transmits operational data using light rather than electrical current and therefore is intrinsically safe under high voltage conditions.
In addition, a fibre is very small and of light weight, so its integration into a pantograph for sensing does not change much the original mass of the pantograph. Added to this is the innovative use of fibre Bragg grating (FBG) technique which allows a single fibre to be inscribed with a number of sensors (FBGs) using multiplexing technique.
By carefully instrumenting a number of FBGs into each pantograph head and monitoring their corresponding wavelength shifts, the joint research team from City University London and from Brecknell Willis have been able to successfully extract the temperature-corrected data, thus allowing for the continuous measurement of both the contact force and the contact location between the pantograph and the OLE.
The impact of this initiative would be significant were it adopted more widely to:
  • The rail operation and maintenance staff: they are better informed of the condition of the electrification system for preventive actions to be taken.
  • The public: minimized traffic disruption and delay/cancellation of train services due to the pantograph dewirement.
  • The UK business: This innovation will give the UK business a competitive edge over its overseas counterparts and huge business opportunities as every OLE system throughout the world has a pantograph but none of which has the ability to monitor the condition of the OLE and actively adapt to the condition of the environment in which it operates. The market potential would thus be significant as every year there are 18,000 to 23,000 new pantographs (approximately 5,000 in Europe, 8,000 – 10,000 in Asia and Middle East, and 5,000 – 8,000 in North & South America) are required to be manufactured in order to meet the increasing market demand.
  • City University London: enhanced profile as a result of the innovation and the impact it would make to the rail industry internationally.
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