Modelling the impacts of space weather on UK railway signalling systems

Patterson, Cameron and Wild, Jim (2024) Modelling the impacts of space weather on UK railway signalling systems. PhD thesis, Lancaster University.

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Abstract

This thesis presents an investigation to model geomagnetic effects on DC track circuit signalling for AC-electrified railways in the UK, using the Glasgow to Edinburgh via Falkirk line and the Preston to Lancaster section of the West Coast Main Line as examples. In Chapter 4, the electric field strengths needed to cause "right side" failures, where green signals for blocks that are unoccupied by trains are turned red, are examined. It is suggested that the threshold is equivalent to an electric field generated by a storm that occurs approximately once every 30 years. Chapter 5 expands this work to "wrong side" failures, where the red signals for blocks that contain trains are turned green, a potentially more hazardous misoperation mode. It is shown that the position of the train along the block or, more precisely, the distance between the rearmost axle and the relay, has a large impact on how susceptible the relay is to geomagnetic disturbances. Assuming each train is near the end of the block it is occupying in the modelling, the electric field strength needed to cause "wrong side" failures is lower than that for "right side" failures, equivalent to the electric field generated by a storm occurring approximately once every 10 to 20 years. In Chapter 6, time-varying electric fields from the March 1989 and October 2003 storms are applied to both routes, as well as 1-in-100 year and 1-in-200 year extreme storm proxies, obtained by scaling the March 1989 storm by 2 and 4 times respectively. For the historic storms, it is shown that there was the potential for a small number of "wrong side" failures, but no "right side" failures to occur. For the extreme storm estimates, it is suggested that a large number of misoperations of both types could occur across each route.