Current Insight on Infrastructure Conditions
Reliable infrastructure is a major concern for railways, airport authorities, power-grid operators, and industrial companies. Besides inspecting assets periodically by taking measurements, Inspectation acknowledges the trend of monitoring assets over longer periods to identify failures early. As a result, we started developing our own online condition monitoring system, FlexMonitoring, for use in rail infrastructure to monitor tracks, relays, turnouts, level crossings and signaling. The system, which is rugged, autonomous, and intelligent, timestamps multiple events and measures a variety of signal types.
Railway Infrastructure Condition Monitoring
Soon after we started development, Dutch railway owner ProRail granted our customer VolkerRail a maintenance contract for a large geographic area. For this contract, VolkerRail needed to guarantee a minimum availability, or uptime, of the railway infrastructure. If VolkerRail achieves better results than the promised uptime, they get a bonus; if VolkerRail does not achieve the promised uptime, there will be high penalties. How VolkerRail delivered the required uptime was negotiable, but it made sense to install an online condition monitoring system at the most critical tracks, points and level crossings.
In a railway net, several items are prone to failure, especially the following:
- Signage—the most common failure is defective lights, so we decided to replace all lightbulbs with LED lighting
- Turnouts—also known as points and switches (or the means of directing a train onto a diverging section of a track) that contain several relays and electric motors to move switching tracks left or right
- Signaling, or train detection systems—a common method of block signaling divides the track into zones where guarded automatic control devices allow only one train in a block at any time
- Level crossings—automatic barriers to stop road traffic that contain relays, electric motors, and signage
For the last three items, problems are often caused by mechanical issues, such as stones on turnouts, aging relays, conductive materials on the track during autumn and winter, or aging electrical motors. By taking multiple measurements and monitoring them over time, we can understand the state of the infrastructure. By automatically analysing trends, we should be able to determine and detect a failure before it actually occurs, and we can inform the maintenance team about the most likely root cause, thereby decreasing downtime during repair work.
Requirements for the Online FlexMonitoring System
For setup of more than 200 monitoring units, we determined that the following requirements were the most important:
- Ruggedness—the rail infrastructure is a very rough electromagnetic compatibility (EMC) environment because of long wires and relay switching, high voltages, and motors turning on and off
- Short time to market—the monitoring systems had to be deployed and operational within a year
- Capability to include various sensors, such as current, temperature, and digital levels, and measure the sensors at different rates, from 2 kS/s to 30 kS/s
- Online buffering of sensor data, online data reduction, and key parameter determination
- System synchronization through GPS—sensors are distributed inside a substation and connected to different logging units, but they might be related to each other
- One software stack for all units that is remotely upgradable and can be configured independently
- 3G connectivity to transfer the data over cellular networks to a central database
- System health monitoring
A server stores all data in a database and contains the configuration for all units and channels. The monitoring units need to be remotely updated and configured. A subset of the data is also made available to an external server, which provides the main interface to the system for the end users. On this server, queries run constantly to detect event failure patterns, show trends, and send text/SMS alarms and warnings to the surveillance teams.
For the monitoring units, we decided to use CompactRIO hardware and base the monitoring system on LabVIEW system design software. We looked at other data loggers and monitoring systems, but we discovered that most of them don’t offer a high sample rate, or, if they feature sample rates up to 1 kS/s, they don’t have enough buffering capabilities to transfer the data later over 3G Universal Mobile Telecommunications System (UMTS) networks. Our systems sometimes may need to sample at 5 kS/s, or even up to 30 kS/s; therefore, an industrial PC, or NI CompactRIO, was the only viable solution. CompactRIO is small and rugged, and integrates with many I/O signals. When combined with the SEA CompactRIO 3G module, it has GPS synchronization and UMTS communication capabilities.
Because of the wide bandwidth of the I/O modules and the rough EMC environment inside the substations, we asked National Instruments Alliance Partner INCAA Computer B.V. to develop an interface board with input protection circuits to the I/O and a watch dog. Besides the NI C Series modules, we use the SEA GPS and GPRS modules to synchronize systems and communicate over wireless cellular networks with the systems for data transfer and remote upgrades.
The software in all CompactRIO units is generic. All systems deployed share the same software. Channels are remotely configured per installation with the type of sensors, characteristics, and measurements. All measurements are event-driven. When an event, such as a digital state change or voltage change, occurs, the logging starts and data is time stamped using GPS clocks. For each channel, a measurement scenario is defined depending on the characteristics of the hardware. For some events, the data is down sampled and transmitted so the user can view the shape of the signal for better understanding of the event.
Several watchdog mechanisms record CompactRIO system health and state, including the communication and GPS signal strength, memory usage, and cabinet temperature. In the unlikely case of an error, the system is fail-safe and resets either the communication modem or the CompactRIO unit completely.
On the server side, a LabVIEW application receives the data and stores it in the SQL database. The application can upgrade the CompactRIO units and monitors their health. Also, it can send raw data to users for detailed analysis.
Finally, a second server receives data and runs a web service to display data to the customer. This server contains different tools, including a calculator tool to perform operations on the data and an event handling tool with alarming. These tools run queries constantly and detect signals that should be displayed to 24/7 surveillance teams as warnings or alarm conditions. The teams and maintenance crew can also be informed by SMS/text messages or email.
The system is now up and running, and we are proud that we developed and deployed more than 200 complex monitoring systems throughout the country within a year. We chose CompactRIO and LabVIEW because of the flexibility to connect all necessary sensor types and signal processing algorithms, the short development time, and our familiarity with the software.
We are looking into other application areas besides the railway infrastructure, such as waterways, and including other types of measurement capabilities, such as programmable logic controller connectivity and image acquisition.