Learnings

Outcomes

The SWIFTER team delivered the final report which identified vulnerabilities, impacts and mitigations associated with the three main failure mechanisms caused by space weather: thermal heating, voltage instability, and harmonic failure. Through stakeholder engagement, we have successfully built industry awareness in the consequences of a RWCS space weather event.  
 
The main outcomes of the project were a series of recommendations for further work to enhance the accuracy of thermal heating and voltage instability models, expand GIC monitoring infrastructure, and deepen understanding of harmonic-related risks. In addition, the project identified which assets are most vulnerable to failure under a RWCS scenario, providing a basis for prioritise resilience measures. The recommendations include: 

Operational Preparedness 
> Engage with generators and interconnectors to understand their operational intentions during space weather events and develop contingency plans for potential disconnection alongside generators and the regulator. 
> Update system contingency and response plans to: 
- Monitor vulnerable transformers when space weather events are forecast. 
- Prepare for controlled disconnection if GIC levels rise beyond safe thresholds. 

Model and Data Improvements 
> Quantify uncertainty at each stage of the modelling process to better prioritise future research efforts on the elements that add most uncertainty to findings. 
> Enhance the BGS GIC model accuracy by: 
- Installing GIC monitors at the most vulnerable locations and sharing both new and existing GIC data with BGS on a regular basis. NGET plans to install 60–70 GIC monitors during RIIO-T3; the placement of these monitors should be reviewed considering the report’s findings. Better sharing of GIC data with space weather researchers may also be in the interests of both the TOs and NESO. 
- Providing BGS with measured transformer earthing resistances, particularly for high-risk transformers. 
- Extending the BGS model to include interconnector- and generator-owned transformers and simulate the impact of their disconnection both on GIC and available supply capacity. 
- Incorporating targeted simulation of the 132 kV distribution network in England and Wales, focusing on substations with vulnerable transformers or multiple 132 kV connections, rather than attempting to model the entire network. 

Advanced Thermal Modelling 
Conduct FEA to more accurately simulate the temperature response of transformers identified as most vulnerable to thermal heating. 

Harmonics Risk Assessment 

Develop NESO’s capability to model and simulate harmonic-related failures, including their interaction with system resonances and inverter-based resources. 

Integrated Modelling and Real-Time Simulation 
> Build an integrated modelling platform that combines the BGS, Frazer­Nash, and NESO models into a unified tool. This would: 
- Enable simulation of additional scenarios and sensitivities. 
- Support real-time updates during space weather events to inform operational decision-making. 

Long-Term System Resilience 
> Continue to assess how evolving network characteristics, such as increased reliance on inverter-based resources, expansion of offshore infrastructure, and adoption of digital control systems, may influence future vulnerability to space weather events. 
> Further evaluate more costly mitigations once more detailed models have been developed. 

Lessons Learnt

A small number of transformers are likely to be vulnerable to thermal heating failure under a reasonable worst-case scenario. Vulnerability depends on local geology, earthing resistances, extent and number of connections and capacity and type of transformers. The most recent model shows three transformers being at risk of failure (exceeding temperatures of 200 °C for their structural elements) under a 1-in-200-year event. The model could be improved by capturing the 132 kV network in England for vulnerable substations, capturing better earthing resistance data, including generator and interconnector owned transformers and further validation against measured geomagnetically induced current data. Finite element analysis of the most vulnerable transformers would help to confirm the anticipated temperature response and thermal heating failure likelihood.  
  
Reactive power losses were calculated at each feeder and inputted into a voltage instability model. Calculated voltage drops remain within Grid Code and SQSS thresholds, indicating that widespread outages are unlikely under RWCS conditions. However, reduced voltage margins and constrained power transfer capability could increase the risk of post-fault instability and incur significant constraint costs. 
 
Harmonics pose a credible risk to system stability, particularly through their impact on protection systems, reactive power assets, and communications infrastructure. Harmonic modelling is complex, although tools such as PowerFactory and PSCAD/TOTEM would help, further work is required to perform these calculations. To support this, a framework for harmonic modelling was also developed, based on EPRI guidance.  
  
There is a large stakeholder community interested in space weather and its impact on the electricity grid. Multiple stakeholders across different organisations have unfortunately slowed the pace of the project. This is especially true of the modelling, with different elements of the models owned by BGS, Frazer-Nash and NESO.  
  
External guidance, particularly that published by EPRI, has been hugely valuable to the project. Much of that guidance is only available behind a paywall, however.