Assessing the Impact of Weak and Moderate Geomagnetic Storms on UK Power Station Transformers

It is well documented that space weather can impact electricity infrastructure, and several incidents have been observed in recent decades and directly linked to large geomagnetic storms (e.g., the Hydro Québec incident in 1989). However, less is understood about the impact of lower‐level geomagnetically induced currents on the health of transformers in the long term. In this study, the long term impact of geomagnetic activity on 13 power station transformers in the UK is investigated. Dissolved gas measurements from 2010 to 2015 were used to look for evidence of a link between degradation of the transformer and heightened levels of the global SYM‐H index and dBdt $\frac{\mathrm{d}B}{\mathrm{d}t}$ as measured at Eskdalemuir magnetometer station in southern Scotland. First, case studies of the most significant storms in this time period were examined using dissolved gas analysis methods, specifically the Low Energy Degradation Triangle. These case studies were then augmented with a statistical survey, including Superposed Epoch Analysis of multiple storm events. No evidence of a systematic space weather impact can be found during this time period, likely owing to the relatively quiet nature of the Sun during this epoch and the modernity of the transformers studied. Plain Language Summary Space weather (changes in the magnetic conditions at Earth due to changes in the Sun's activity) is known to impact electricity networks. Several incidents have been observed in recent decades and directly linked to large space weather events (e.g., the Hydro Québec incident in 1989). In this study, the long term impact of lower‐level geomagnetic activity on 13 power station transformers in the UK is investigated. Transformer health data from 2010 to 2015 were used to look for evidence of a link between damage to the transformers and increased levels of global and local space weather metrics. First, case studies of the most significant storms in this time period were examined using dissolved gas analysis methods, which measure the levels of different gases within the transformer and are an indication of its health. The case studies were then expanded to look for general trends in the data. No evidence of a strong space weather impact can be found during this time period, which is likely to be due to the relatively quiet nature of the Sun at the time. Key Points Data from 13 UK power transformers during 2010–2015 were analyzed to look for evidence of space weather impact on