Project Summary
The primary focus of REVISE is revisiting the current methodology for assigning overhead line ratings. The calculation process uses historical environmental data captured in the 1980s that is applied uniformly across the UK disregarding local/regional climate variations. The existing transmission network is increasingly constrained by system capacity limits exacerbated by rapidly increasing renewable integration. Improving understanding of line ratings, using latest generation highresolution weather topographic data combined with the latest techniques for system modelling, will allow for improved targeted investment to ensure we meet demand for the connection of new renewables to the network, securing a safer and greener future.
Innovation Justification
The core innovation of REVISE is a pathway to implementation of an updated process and supporting tool to revise existing OHL ratings, which builds on previous and ongoing research. The University of Strathclyde has recently completed a literature review of the line-uprating approaches that various networks across the world have taken.
The TRL of revising line capacity ratings using environmental data accurate to a line's location/region is 9, as this is a mission-proven BaU. However, the innovative aspect of this project is harnessing this proven technology and pairing it with the latest generation high-resolution weather topographic data combined with the latest techniques for system modelling to implement the solution within the UK. By the end of Discovery, through the engagement with key customers work package an IRL of 2 will be also achieved. Further understanding of requirements, use case, and constraints will be gained, and a cost-benefit analysis will be established pushing the CRL to 4.
An agile approach will be taken over the 3 months to gain a deeper understanding of how current processes could be improved to support the management and operation of a net zero power system. By completion of Discovery, understanding will be sufficient to decide whether the project should be progressed to an Alpha phase application. Alpha will include identification and processing of region(s), proof of concept, and further exploration of required implementation activities.
As the project involves revisiting and potentially re-rating existing OHL infrastructure, requiring a high level of validation and confidence to avoid designing in significant risk. For greatest strength, the solution/process needs to be applicable to all of GB and be open to other networks. GB-wide co-ordination is therefore required and means that funding via BaU is not suitable. It is felt that the use of the SIF fund is wholly appropriate for this project as it brings together industry and academia, representing the entire network. Involvement from NGET and the ESO will lead to a common standard across the UK.
During project ideation, consideration was given to adopting 'post fault' ratings on lines not at risk of fault conditions or, for windfarms, attempting to correlate generation, line rating, and windspeed to produce a pseudo-dynamic rating. These were not progressed due to their inability to reduce constraints on the majority of the network and the high risk of regularly exceeding the line rating resulting in a risk to the network and public.
Appendix Q3 REVISE.pdf (opens in a new window)
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Impacts and Benefits
REVISE will deliver the following benefits:
Financial - future reductions in the cost of operating the network
By 2025, total UK constraint costs are expected to peak at around £1 billion to £2.5 billion a year which is ultimately paid by consumers. The total cost of managing power flow constraints on the GB transmission system in 22/23 was £1.1bn (£740m on SSEN-T network). Even if potential savings from REVISE account for only a small portion of these costs, it will be sufficient to justify the project deployment costs, for example:
% Reduction in Constraint Est. Annual Saving [SSEN-S (North to South) boundary]
2.5 £ 8,234,400
5.0 £16,468,800
10.0 £32,937,600
REVISE could also reduce connection costs by allowing smaller, wood pole lines, 132kV circuits etc., and less costly overhead lines to be viable for a larger number of connection schemes.
Environmental - carbon reduction -- indirect CO2 savings per annum
Revise offers the following:
- Alleviating the constraint on renewable generation reduces the partial reliance on gas/diesel generation used to offset the difference.
- Circuit rating achieved with no physical works and the associated embedded carbon involved.
- May enable smaller renewable schemes to connect without the need to wait for further infrastructure works, helping to progress the connection queue.
- May remove the need to upgrade/replace circuits following a connection request.
New to market - processes
REVISE will be a new process/tool that will calculate overhead line ratings using high-resolution weather topographic data. This will replace the existing process developed 1980s and applies uniformly across the UK. After a successful demonstration and pilot of the tool it will be available to other UK transmission network operators.
It is possible that a new commercial tool could be created, this will be determined in later phases of the project.
Others that are not SIF-specific
REVISE will offer the opportunity to improve the reliability, stability, and safety of the network. Firstly, by identifying circuits that, using the current rating methodology, are at risk of exceeding their safe operating temperature, and thus may put the public and network at risk. Secondly, increasing the post-fault rating of circuits enabling the network to recover demand more quickly in the event of a fault; compared to having to wait for a circuit under outage to be reinstated.
Overall, REVISE will lead to a more flexible and adaptable network.
A cost-benefit analysis will be undertaken as part of Discovery.
