The project aims to address thermal limitations of underground distributions networks, particularly in HV/LV networks, by incorporating real-time temperature data to challenge existing cable rating methodologies. Existing cable ratings are based on assumed environmental factors, leading to potential over- or underestimation of network true capacity. The DIRT project will first conduct a feasibility study to explore temperature monitoring technologies, follow on value streams will then develop monitoring technologies through real-world trials to validate environmental assumptions and refine rating methodology. The goal is to optimize network capacity, thus reduce the need for costly replacement, utilising existing assets. whilst facilitating the installation of low-carbon technologies essential for achieving NetZero. The project will help identify thermal vulnerabilities within networks, informing future decisions that will improve the resilience and reliability of networks for customers whilst enhancing understanding of climate change thermal impacts. Success will be measured by the development of refined cable rating methodology and the demonstrated cost savings from more efficient network planning and asset utilisation.
Benefits
The insights gained from DIRT will provide valuable benefits to both UK DNOs and their customers.
By investigating the potential of real-time thermal data, DIRT will challenge traditional cable rating and asset replacement methods. Updating UK DNO cable rating practices with real-time thermal data could reveal untapped network capacity, reducing the need for expensive network upgrades and making better use of existing networks, ultimately delivering greater value to customers.
Expanding network capacity will facilitate the installation of low-carbon technologies essential for achieving NetZero targets. The project will also enhance understanding of climate change impacts and contribute to the UK’s climate change adaptation efforts, which will be increasingly important in the coming years.
The project will help identify thermal vulnerabilities within networks, informing future decisions that will improve the resilience and reliability of networks for customers. Better network reliability will reduce unplanned outages and minimize the costs of repairs and the broader societal impacts.
The initial feasibility study will be research-focused, with financial benefits to be determined only after this phase.
Learnings
Outcomes
Early findings have delivered a comprehensive set of outcomes that significantly improve understanding of underground cable thermal behaviour and the limitations of current rating methodologies. These will be fully summarised in the final recommendations report due April 2026.
A key outcome has been the quantification of uncertainty within existing cable rating approaches, demonstrating that reliance on assumed inputs for both ground conditions and load behaviour can lead to underutilisation of capacity and unrecognised thermal risk.
To date the project identified three primary areas for future improvement:
- Lack of direct cable temperature data
- Simplified representation of ground and soil conditions
- Use of non-representative load assumptions (load curve G)
The project has advanced the concept from approximately TRL 2 (research stage) to TRL 6 (validated for controlled testing), representing a significant step toward practical application of update cable rating methodology.
Overall to date, the project has demonstrated that transitioning from assumption-based to evidence-based cable rating is feasible and beneficial, providing a strong foundation for future development and implementation.
Lessons Learnt
The project has generated important lessons to inform future phases and similar innovation activities, these lessons will be expanded on in the final recommendations report along with next steps and associated road map.
A key early finding is that current cable rating methodologies are heavily dependent on simplified assumptions, particularly for ground conditions and load behaviour. The absence of real-world measurement data introduces uncertainty, which limits confidence in both available capacity and thermal risk which unpins many industry decisions. The importance of better utilising existing datasets has been clearly identified. For example, replacing standardised load assumptions (Load Curve G) embed in current methodology with feeder-specific profiles represents a high-value, low-cost opportunity to improve cable rating accuracy
The project demonstrated that no single solution is sufficient to address this challenge. Instead, a layered approach is required, combining improved utilisation of existing datasets (e.g. LV monitoring and environmental data) with targeted deployment of monitoring technologies.
The project has highlighted that full network-wide monitoring is not proportionate for LV systems. A targeted deployment strategy, focusing on constrained or representative circuits, provides the most cost-effective route to gaining insight while maintaining scalability.
Future projects should prioritise validation activities, including laboratory testing and field trials, to calibrate models against real-world data. Without validation, it remains difficult to determine whether existing ratings are overly conservative or optimistic.
In terms of Technology Readiness Level (TRL), the project has advanced from early concept to a stage where solutions are defined and ready for validation (approximately TRL 6). Further trialling and validation is required before large-scale deployment.
