Relay-based installations currently represent the backbone of most railway signalling assets. Many experts believe that relay-based signalling installations will be in operation in most countries far beyond 2030; relay-related knowledge therefore needs to be maintained. However, many stakeholders are facing a significant relay-related brain drain. Unfortunately, quite often, neither sufficient documentation nor training possibilities are available, so that there is a risk of losing know-how over time. The UIC Signalling Expert Group (SEG) has therefore published a technical report entitled “Use of Signalling Relays”. The report can be downloaded free to charge from the UIC ETF Shop at https://www.shop-etf.com.
The technical report is the main outcome from the SEG Use of Signalling Relays project, in which UIC SEG members worked in close collaboration with experts from various railways. The report refers to both class C and class N relays in accordance with UIC Leaflet 736. However, the focus is on the C relay, mainly because of the background and knowledge of the experts involved in the project. The report is now available in English and German, and the French version will be published in 2021.
The technical report provides information on more than 100 potential failures and associated risks as well as almost 100 elementary and frequently used measures to eliminate them. The main deliverable is the so-called impact matrix, which evaluates the impact of measures on given failures and risks, with more than 700 recommendations in total (of which 500 are relevant to functional safety). In addition, the report includes common wiring diagrams and symbols as well as information on how to conduct quantitative analyses of relay circuits.
The technical report focuses on DC relays. Specific measures regarding the use of AC relays and electronic solid-state relays are not explained because of the limited resources available. The same is true for interfacing relays with electronic components.
The UIC SEG Use of Signalling Relays project has the potential to maintain relay-related knowledge beyond 2030. The structure of the report supports self-study. Knowledge gained from one chapter can be verified by reading another chapter. Furthermore, the outcomes of the Use of Signalling Relays project will be used to further improve requirements and recommendations defined in UIC Leaflet 736, which is to be converted to International Railway Solution (IRS) 70736 in 2021.
The UIC Signalling Expert Group is a railway signalling-related forum in which experts from different railways share information. The group holds meetings around 3-4 times a year, and new members are more than welcome to join the group.