With Network Rail under increased scrutiny for its part in train punctuality performance, reliability of the infrastructure becomes ever more important. One of the recurring themes as to why trains are late and cancelled, along with the old chestnuts of signalling failure and leaves on the line, is that the wires are down. This can be anything from a simple break (although even that can take time to fix), to a train having rolled all the catenary up into a ball over a mile or more.

Frequently such incidents are caused by defective pantographs on the trains, which can inflict significant damage to overhead wires and associated apparatus including, in extreme cases, a catastrophic de-wirement.

Real-time monitoring

Pantographs, and the thin carbon strips they carry to draw current from the overhead contact wire, are usually subjected to thorough manual inspections during scheduled maintenance windows.

In-between these checks, maintenance teams will often rely on a visual check taken from the depot floor. However, with pantographs in constant use and operating under all weather conditions, defects can quickly accumulate.

Remote monitoring technology enables infrastructure owners to identify those vehicles in operation that are at greater risk of inflicting damage to the network’s wires due to general wear and tear. It can then help them to work with operators to take early preventative action and, ultimately, extend the life of both the wires and the pantograph equipment carried by the trains.

The current Panchex system was originally installed during the 1980s but only monitors the uplift forces from passing pantographs. It is now expensive and disruptive to maintain and is considered to be reaching the end of its serviceable life.

Furthermore, its location within the live 25kV catenary system means that some of its components can only be accessed when lines are closed to traffic and overhead lines isolated, adversely affecting the availability of the system.

This led to Network Rail and industry stakeholders looking for a ‘modern equivalent’ successor system, combining reliable round-the-clock uplift monitoring with additional condition-monitoring capabilities, whilst being easier and safer to operate and maintain.

Developing PanMon

Ricardo Rail (formerly Lloyd’s Register Rail) developed PanMon to meet this need. The system uses Sensys’ Automatic Pantograph Monitoring System (APMS) to provide high definition images of each passing pantograph through a combination of radar, laser, video and photo technology, and an innovative new contactless optical Uplift Monitoring system developed by Ricardo Rail in association with Italian-based optical monitoring specialists DMA S.r.l, Turin.

Using specialist pattern-recognition analysis software, the system automatically interprets the data to provide ongoing condition reports of each passing pantograph. This includes identifying the remaining thickness of carbon strips or any damage to the pantograph’s head, aerofoils or end horns, which can affect a vehicle’s ability to maintain good contact with overhead wires.

The system can also measure the uplift of the contact wire resulting from the force applied by the pantograph – uplifts exceeding specified limits can cause considerable damage to both the pantograph and catenary.

Approval trials commenced at Cheddington, in Buckinghamshire, in March 2013. During these, the system was assessed against Network Rail’s criteria that it should:

» Measure a minimum of 90% of passing traffic;

» Capture measurements of carbon thickness on pantographs to within 2mm;

» Deliver accurate measurements of uplift forces;

» Consistently detect chips and defects larger than 25% of the carbon surface width;

» Identify each passing vehicle;

» Record and report local weather conditions (wind direction / speed, temperature etc).

Throughout the trials, PanMon proved capable of providing continuous and accurate measurements of pantograph uplift forces and defects (including chips, damaged end-horns and worn carbon strips) from trains passing at speeds of up to 125mph. As a result, the PanMon system is now designated for roll-out as a replacement of the Panchex system.

Network Rail’s project manager for the PanMon trial at Cheddington, Mike Dobbs, was pleased with the result. “Getting new technology to work accurately and reliably in the rail environment can be challenging,” he said, “but Ricardo Rail has worked closely with us to overcome the difficulties and we are now able to start the process of replacing our old Panchex systems with a twenty-first century solution.”