The Distributed Restart project was a partnership between National Grid Electricity System Operator (ESO), SP Energy Networks (SPEN) and TNEI that was awarded £10.3 million of Network Innovation Competition (NIC) funding. Over a period of four years the project explored how distributed energy resources (DER) could be used to restore power in the highly unlikely event of a total or partial shutdown of the National Electricity Transmission System. Significant technical, organisational and commercial challenges were addressed through the project. TNEI performed the following work on the project’s three main workstreams exploring how best to enable restoration services from DER:
Power Engineering and Trials (PET) workstream
TNEI assessed the viability of Distributed Restart by performing extensive load flow and dynamic power system studies on 33kV case study networks, evaluating different restoration scenarios. By considering and evaluating aspects such as the block load pickup (BPLU) capability of the anchor generator, active and reactive power support from onshore wind farms, and circuit and transformer energisation constraints, TNEI assessed different restoration scenarios and identified the optimum solution of restoring supply to transmission circuits and transformer while adhering to voltage or frequency limits.
Organisational, Systems and Telecommunications (OST) workstream
The Organisational, Systems and Telecommunications workstream considered the DER-based restoration process in terms of the different roles, responsibilities and relationships needed across the industry to implement at scale. TNEI developed a simulation tool to validate the communications process that the project team had developed during a series of desktop exercises. The simulation was web-based and allowed stakeholders from the TSO, TO, DNOs and DERs to interact with a “live” network and see how their actions contributed to the restoration of the network.
Procurement and Compliance (P&C) workstream
The Procurement and Compliance (P&C) workstream explored and addressed the best way to deliver the concept of Distributed Restart to customers. TNEI was contracted to review all relevant GB and European industry codes, and made recommendations for changes to be undertaken to the GB technical codes including the Grid Code, the Distribution Code, the System Operator Transmission Owner Code (STC) , and the Security and Quality of Supply Standard (SQSS). Changes to commercial codes such as the Balancing and Settlement Code (BSC), Connection and Use of System Code (CUSC), and Distribution Connection and Use of System Agreement (DCUSA), were also recommended to support the implementation of Distributed Restart.
Furthermore, TNEI assisted with the development of a set of functional requirements for system restoration providers, as well as a model to evaluate tender submissions as part of a mock tender exercise run by NGESO. An assessment of DER capability across GB was performed, and made available as a web-based tool to NGESO to aid them with the planning and evaluation of future restoration service tenders.
Lastly, TNEI also developed and maintained a robust cost-benefit analysis model to calculate the benefits of Distributed Restart. Costs from the trial projects as well as other inputs were used to determine the cost saving of using Distributed Restart for restoration up to 2050. The results have been used, amongst others, by Ofgem to mandate the implementation of Distributed Restart from 2026 as business as usual.
The Distributed ReStart project was a first of its kind project that aimed to solve the complex challenges associated with re-energising a transmission network using DERs in a bottom-up approach to restoration. TNEI was included as a partner for the PET workstream to perform power system studies to assess various technical scenarios and develop feasible restoration solutions. However, we ended up also supporting the other workstreams by developing several tools. We also utilised our business case modelling capability to develop a robust business case for Ofgem.
The project was originally a 3-year project (2019 – 2021) but was extended by another 2 years due to additional live trials performed by SPEN. Despite the extension, the project has been completed on budget. It has resulted in a number of Cired and Cigré papers, and has been shortlisted for several industry awards, including an IET Award. It has also been hailed a major success by Ofgem in its ESO Performance Panel 2021-2023 review.
Through the direct contributions of TNEI, some of the technical challenges associated with Distributed Restart have been resolved, paving the way for it to be implemented by NGESO as business-as-usual from 2026. Restoration from DER was also found to have a positive business case. The success of the project will enable DERs to compete with conventional fossil fuel generators for the provision of restoration services, which will help to reduce the dependence on carbon emitting providers and achieve GB’s Net Zero ambitions.
