The Distributed Restart NIC project is exploring how Distributed Energy Resources (DERs) can be used to restore power in the event of a total or partial shutdown of the GB Electricity Network. Current approaches rely on large power stations and interconnectors but, as the UK moves to cleaner and more decentralised energy, new options must be developed, leading to reductions in both cost and carbon emissions.
Two live trails have been completed at Galloway and Chapelcross Grid Supply Points (GPSs). This follow-on NIA project will support an additional live trial at Redhouse GSP to demonstrate the use of a battery energy storage system (BESS) with grid-forming technology to restart the network and use of a prototype Distribution Restoration Zone Controller (DRZC) to stabilise and maintain the power island within voltage and frequency limits.
Benefits
Based on the latest project cost/benefit analysis, the developed method has the potential to deliver financial benefits of at least £115m (net present value in 2018/19 prices) and carbon benefits of 0.81MT of cumulative avoided CO2e for consumers by 2050, breaking even by 2027 (within 5 years of the end of the project).
Extending the project to deliver the Redhouse live trial will bring additional benefits to the consumer (using economies of scale and existing expertise via the project vs. time and financial costs in starting a new ‘Redhouse’ project from scratch) and industry by ‘de-risking’ the rollout of the new Electricity System Restoration Standard (ESRS), demonstrating that automation is achievable in an operational/BAU environment.
Learnings
Outcomes
Final project outcomes
Since the award of NIA funding in February 2023, the final live trial has been delivered at Redhouse, including preparation of the necessary legal agreements for the Redhouse trial to go ahead with the trial generators. These were successfully completed, but remain confidential, and as such will not be publicly available on the website. Interested parties with a legitimate need to view these agreements may refer to the statement at the end of this document if required. In addition, we have produced the third and final Power Engineering & Trials (PET) Part 3 report on our website, along with hosting a Redhouse Live Trial webinar on Wednesday 11th October 2023. Almost 100 external project stakeholders attended, to meet the presenters virtually, and ask detailed questions from the engineering experts on the bridge.
Background
This report details the methodology, results and findings from the Distributed Restart Redhouse live trial, undertaken in June 2023. This trial was the third and final trial undertaken as part of a series of world-first trials. The trials were designed to provide detailed understanding on how distributed energy resources (DERs) can build, maintain, and optimise power islands isolated from the main grid – with a view to driving down the time it would take to restore the network following the extremely unlikely event of total shutdown of Great Britain’s electricity grid.
The traditional top-down approach would be complimented by the DER enabled bottom-up approach to help ensure the target of 60% of demand would be restored within a 24-hour period from 2026 onwards, as detailed in the Electricity System Restoration Standard (ESRS).
The trial at Redhouse was fundamentally different to the two previously completed trials at Galloway and Chapelcross in that the anchor generator for this test was a non-synchronous inverter-based asset, this being a BESS, as opposed to a synchronous generator. Details of how the test network was enabled, what tests were undertaken, and the result of the tests are included in this report, alongside supplementary supporting material.
The tests took place at SP Energy Networks’ Redhouse substation near Glenrothes in central Scotland. The test networks’ main elements comprised of:
- 11.6 MVA (8 MW, 8 MWh) grid-forming capable BESS.
- 24 MVA 11/33 kV primary distribution transformer connected via an underground cable.
- 10 MVA 11/33 kV primary distribution transformer connected via an overhead line (OHL).
- 5 MVA load bank used to simulate customer demand.
- 3 MVA solar farm utilised as the top-up generator for the island.
- 90 MVA 33/132 kV grid transmission transformer located at Redhouse.
- 10.6 km 132 kV OHL to the neighbouring Glenniston substation.
- 33 kV earthing transformer (ET) for use during the tests when another earth point was not connected.
- Supporting 5 MVA diesel genset and auxiliary supplies.
Summary of findings
The tests overall were hugely successful, and the BESS’ performance was tested and observed to be excellent when acting as the anchor generator for the power island. Furthermore, the tests proved that:
- BESS can be utilised as anchor generators to start, maintain, and control power islands very effectively, with the aid of diesel gensets or without.
- They can energise both distribution and transmission transformers and lines and are much more effective at doing so when point on wave (PoW) switching is active.
- The block load pickup (BLPU) capability of the BESS when compared to synchronous generators of the same capacity is far superior and, in this case, needed to be derived as opposed to measured due to its ability to outperform the biggest load step the equipment could implement (4 MW).
- The DRZC can automate the startup and operation of the BESS system, optimise the power island’s performance, and can utilise its functionality to resync with the intact grid.
- The island assets can be used together as a dynamic virtual power plant (DVPP) and dispatch load or generation as needed when connected to the grid.
- Comparatively small diesel gensets in isolation can energise both distribution and transmission transformers and lines and are much more effective at doing so when point on wave (PoW) switching is active.
Ultimately, these world-first tests set a precedent for the use of BESS assets to be used, not just in the UK but around the world, as viable network restoration service providers.
Lessons Learnt
The Distributed ReStart project has led to the development of clear and detailed information to allow other network operators and industry stakeholders to understand how distributed energy resources (DERs) can be used to restore power in the highly unlikely event of a total or partial shutdown of the national electricity transmission system (NETS).
To provide a central, focused point for accessing this information, the outcomes of the project are presented in our ‘Final Findings and Proposals for Electricity System Restoration from DERs’ report, allowing interested parties involved in the BAU rollout of contracting for distributed generation, to be able to understand how Distributed ReStart can be applied on their networks, and where detailed supporting information can be found.
Review of benefits case
The 2018 funding submission to Ofgem for Distributed ReStart included a Cost Benefit Analysis (CBA). This appraised the potential benefits to the system and consumers of having access to restoration services from distributed energy resources.
The original 2018 CBA calculated a net present value (NPV) of up to £115m by 2050. A small update to this CBA, based on interim project learning, was then provided in the 2020 end of year report. This resulted in an increased NPV of £145m. In our formal Closedown report for the original 10 Ofgem deliverables, we provided a further update to the CBA which, compared to the original 2018 version, incorporates further project learning, updated data and assumptions, and some refinements of the overall modelling methodology. The updates described above have resulted in an updated calculated net present value of £130m.
