Latest NewsAll the Latest Technical Advances in Remote Monitoring
After a disappointing early history, remote monitoring technology of signalling and other trackside assets is now providing real benefits in preventing train delays and reducing the cost of maintenance: there are also some significant safety benefits.
1. Introduction
This article describes the new accessibility to asset behaviour, in terms of need-to-know alerts and real time information on the internet, before looking in turn at the benefits with respect to specific signalling and other assets, to the maintainer, the operator and the engineer.
2. User-friendly access to assets
2.1 SMS and e-mail alerts
The latest technology can now provide early warning alerts by SMS text or e-mail to maintenance and operational staff. Maintenance managers can set their own alert levels and configure which individuals should receive which alerts. The fanciful idea of an asset 'ringing in sick' has now become a reality.
Users can acknowledge alerts from their mobile phones, and other facilities are available, such as highlighting or suppressing alerts when caused during maintenance action.
2.2 Asset information on the net
In addition to the alert service, users can now access all their asset information in real time from any lap-top or BlackBerry. The information is presented in Windows-based web pages, with all assets on one 'Explorer' type folder structure. User-friendly features such as instant zoom, and drilling down by clicking on alerts make navigating around the data intuitive and trouble-free.
2.3 One scalable system
The latest technology means that a trackside asset monitoring system can be scalable both 'vertically' in the number of one type of asset being monitored, or 'horizontally' in adding to the asset types being simultaneously monitored.
The monitoring hardware at trackside is also available in a number of sizes, from a small PCB located within the asset itself, to a location case with a capacity of thousands of inputs. The CDSRail Atlas platform uses a master-board with slaves that can pick up digital or analogue data, or a serial databus such as Modbus. All information is sent by standard protocols to a central database server, preferably wirelessly by GSM, Ethernet or GPRS, but if none of these is available, by phone line.
Generally data is 'pulled' from assets every hour, but when an alert is detected, it is 'pushed' immediately to the server. The exception is Point Condition Monitoring, where data is dispatched from each swing of the points
3. Specific assets for monitoring - Signalling
Asset monitoring generally provides 3 types of early warnings of failure - simple level warnings, analysis of sequences of digital events (usually derived by intelligent algorithms from relay movements, but also from decoding data streams from computer-based interlockings), and analysis of analogue measurements of, for example, point machines.
3.1 Point and track flick
Point and track flick are a consistent early warning of failure of the point machine or track circuit respectively. Point flick is a momentary loss of detection during the passage of a train, whereas track flick is a momentary reversal of occupied/unoccupied status, also usually under the impact of a train. Maintainers who attend to the assets exhibiting these behaviours can restore them to a resilient state before they fail. The conditions are detected by analysis of the timing of track circuit and point relay movements, or the equivalent data in the datastreams of electronic interlockings.
A similar benefit can be obtained by measuring point swing time inconsistency, another reliable warning of failure if corrective action is not taken.
3.2 Signalling power supply earth leakage detection
Equipments have existed for some time that can reliably detect earth leakage in signalling power supplies. Remote monitoring allows the analogue value of leakage, as well as digital warnings and alarms, to be transported direct to the maintainer, with an SMS or e-mail alert when appropriate.
3.3 Point Condition Monitoring (PCM)
PCM takes the early warning of point machine failure to a different level by monitoring the analogue profiles of force, current and (where applicable) hydraulic pressure, and analysing the beginnings of anomalous behaviour. Synchronous (parallel) measurement of inputs is essential to overlay profiles precisely, and intelligent algorithms are required to define typical behaviour for that particular machine, and hence to detect any significant divergence. Experience of failure modes and their incipient effect on profiles is needed to refine the algorithms and ensure that spurious alarms are not generated from harmless deviations.
3.4 Leaf fall contamination
Leaf fall contamination is a threat to the correct working of track circuits and the waveform of the track circuit is utilised to detect noise on the waveform and to alert the maintainer.
3.5 Level Crossing correct working
Confirmation of the correct function of a level crossing is not always available to the signalman, so if there is a driver or pedestrian report of a malfunction, remote monitoring is required to verify and diagnose the report if lengthy interruptions to the timetable are to be avoided. The sequence of lamps and barriers at every train passing is captured and time stamped from the interlocking and may be replayed at the Graphic User Interface. This is currently being extended to include road lamp function.
3.6 Battery monitoring
Lead acid batteries are used as back-up power supplies for example for a group of point machines. If the failure of the battery charger goes undetected, then there is a risk that all the point machines around a junction can become simultaneously unserviceable, a major risk to the timetable.
Simple battery voltage level can be remotely monitored to provide an early warning, or more sophisticated analogue measurement can be used to aid the maintenance and replacement frequency of the batteries.
3.7 Signals
An anomalous change of aspect can be detected by comparing the aspect change with what should be expected.
4. Specific assets for monitoring - non-Signalling
4.1 Point heating
Point heating to prevent the damaging effects of ice and snow is not required frequently, so it is all the more important that it is functionally checked. Remote monitoring can be applied to proprietary point heating equipments and the maintainer warned in the case of failure.
4.2 Rail Temperature and SFT
Depending on how optimum is the stressing of a section of rail, rail temperature can be critical in terms of the danger of buckling in high temperatures or fracturing in low temperatures. In extremes of temperature, multiple maintenance teams often have to be deployed to take temperatures manually at a wide number of locations. The technology is now available to measure rail temperature with simple clip-on devices and to radio the temperature to a central system, from where it can be converted to amber and red warning levels for SMS text alert or e-mail. The frequency of readings can be increased as the temperature becomes more critical, and the condition of the equipment itself is also reported. A BlackBerry is particularly useful for Rail Temperature, giving all temperatures continually over a wide area to a hand-held device.
At present knowledge of the stress-free temperature (SFT) which indicates the optimisation of the rail stress, is required to set rail temperature alarm levels, but the technology will shortly be available to track remotely the changes in stress from a known datum, as well as in temperature.
4.3 Power Supplies
Sometimes the voltage and frequency of power supplies can cause problems in the equipment powered, so it is important to be able to have a sure record of these parameters, to analyse the cause and determine the responsibility for the problems.
4.4 Earthworks monitoring and Flood warning
Reliable monitoring of earthwork movement for example in cuttings, is available today, but in common with other self-contained systems, requires a periodic visit by track staff, invariably wasted in that the visit confirms no problem is present. Remote monitoring is a quick win on maintenance cost in that the measurements are continually available, with immediate text or e-mail alerts if they move outside selected ranges. The safety improvement from this is obvious.
Similarly flood levels with amber and red warnings can also be detected remotely to aid operational decisions and safety.
5 Reliability and Availability
For many years, remote monitoring systems have been sold that generated great volumes of uninterpreted data that no-one had time to analyse, in a state of development that generated frequent false alarms, and requiring a level of maintenance approaching that of the asset whose maintenance they purported to reduce.
The advent of systems of very high reliability is at least as important to the user railways as the technological advances in functionality and accessibility described above. A breakthrough is also available in the maintainability of the monitoring systems: the remote access to the systems allows the user or the supplier to monitor the continued functionality of the monitoring system itself.