Relay cabinets for railway switches

Context

Responsibilities of railway operators can be divided into three requirements: safety, availability and fluidity. Such responsibilities are in the scope of two railway subsystems: the interlocking and the traffic management system.

Interlocking systems are made of two main components: the signals defining when trains can move and the switches (also called points) used to allow train or metro to switch tracks. A track switch is a movable railway equipment which links two adjacent tracks and allow a train to move from one track to another or keep it on the same track. Each switch must be in the correct position and locked until the train or metro passes beyond the section of the track involved or the signal to process is withdrawn and a certain time has passed.

Failures in track switch can affect the train movement, leading to track unavailability or even accidents (derailments or collisions). Therefore, track switch is a critical equipment to guarantee the availability and safety of a railway system.

How does a track switch work?

Track switch has two basic operational configurations:

• Normal configuration: train keep the same track ahead (left illustration)
• Reverse configuration: train is routed to an adjacent track ahead (right illustration)

The configuration of a track switch is set by an electric motor (blue) commanded by the switch machine. The motor is activated when a change of direction is required. The command of the activation of the motor is therefore crucial. In addition, end-of-travel sensors provide information on the position of the train, which can be used to warn railway operators in case of problems. The control of these sensors is essential because if they are not properly configured, this can lead to accidents.

Command and control provided by Alpha Innovations cabinets

In this context, the function of the trackside signaling cabinets is to collect all the information from the track and other systems to the central station.

The interfacing function, which is simple to understand, nevertheless requires rigorous and challenging implementation. Therefore, the techniques used and the manufacturing process must be at the cutting edge in order to guarantee this role of central node without any deterioration in safety, availability and fluidity of the metro or train.

Alpha Innovations has developed railway safety equipment to control and monitor train or metro switches. It requires a real investment and very specific skills that we are lucky to have at Alpha Innovations.

Prototype design and tests

In order to develop this type of equipment, the first step was to define the design. Thanks to our team of engineers, a first prototype was developed. To guarantee the safety, efficiency and reliability of this equipment, two types of tests were carried out:

• Environmental tests to ensure the resistance of the cabinet
• Operational tests to ensure that availability and safety requirements are met

As railway standards are very demanding, several tests must be carried out when bringing railway safety equipment to market. We have therefore tested the resistance of our system to vibration, pollution, dust, humidity and temperature. Of course, compliance with EMC standards was also checked.

Thanks to the tests carried out in-house, we were able to demonstrate:

• The mechanical resistance of the enclosure to vibration
• The effectiveness of the surface treatment on the mechanical parts so that they are not affected by pollution, dust and humidity
• The resistance of our cabinet to corrosion
• The effectiveness of the protection against water and dust (IP54)

Once these tests had been carried out and validated, we were able to freeze the industrial file of our equipment.

Development of a test-bench for test on series

The next step is certainly the most delicate: the test on the series. Indeed, it is important to be able to demonstrate that what has been tested and validated on the prototype is still guaranteed during production in larger quantities.

Since a single cabinet contains hundreds of wires and hundreds of meters of cable, testing the connections must be meticulous. The particularity of our process is that these tests are not done by human being but by a test-bench (cable scan) developed by our engineers.

Using this technology brings significant benefits to our customers, such as:

• Greater reliability because the tests are automatic and performed by a perfectly configured machine
• Higher control rate because the machine not only checks that the connections made are good, but also that there are no spurious or unnecessary connections.
• Increased speed of testing as the machine will take a few minutes to check the connections whereas a human being would have taken several hours
• Proof of performance with a test report issued by the machine and automatically archived in our servers.

In addition, our test-bench has been approved by a major player in the railway sector for a series of trackside signal cabinets used in a CBTC system.

But why did we get into this?

It all started with a request from an existing partner for equipment that would allow them to connect relays along the tracks and feed back information to a central station. Over the course of the project, our team gained almost unique experience that opened the doors to this niche market. Being at the forefront of technology through innovation is in our DNA and without our exceptional team, this would not be possible!