World-first trial brings renewables one step closer to restarting GB’s electricity grid

• Successful trial in Scotland involved hydro generator and wind farm turbines

• Potential blueprint for restoring demand in the highly unlikely event of GB network shutdown scenario through the establishment of “local power islands”

• Paves way to incorporate distributed energy resources (DER) in providing vital network restoration service

• Renewables-led grid restart would reduce costs while helping GB hit net zero targets

A live trial in Galloway, south-west Scotland saw a hydro generator connected to the distribution network self-start, energise the local transmission and distribution network, and power up wind turbines on two wind farms within an isolated test network.

There has never been a need to restart GB’s electricity system from scratch and the prospect remains improbable. However, the success of the trial could create a blueprint for incorporating distributed energy resources (DER) using numerous green energy sources, to fire up Britain’s electricity system in the highly unlikely event of a shutdown of the electricity network.

The scale of the trial and its innovative approach is a world first and ground-breaking moment in the Distributed ReStart project: a collaboration between National Grid ESO, SP Energy Networks and specialist energy consultancy TNEI.

Traditionally, large power stations are used to energise the higher voltage transmission network in the unlikely event of a partial or total shutdown of the electricity system, followed by a ‘top-down’ restoration of demand at lower voltages.

The three-year Ofgem-funded Distributed ReStart project is instead trialling a ‘bottom-up’ approach by utilising DERs such as solar, wind or hydro, to fire up the electricity system. Its aim is to show how this process would restore demand to localised areas of electricity network and establish Distribution Restoration Zones (DRZs).

The trial was a truly collaborative effort with coordination not only required between the National Grid ESO and SP Energy Networks control rooms, but also in the coordination of multiple operational resources and people in preparation for and during the live testing. 

The result was establishing a stable ‘power island’ incorporating the hydro generator as the ‘anchor’, used to initially self-start and energise the local electricity network, and then power up several turbines at Glenchamber and North Rhins wind farms.

These tests proved the viability of connecting multiple DERs to a ‘weak’ islanded section of the electricity network, and now has the potential to be rolled out across Britain to establish working DRZs and to restore local demand in the event of a partial or total shut down of the electricity system.

Using DER and green energy sources to restore GB’s electricity system and increasing the diversity of providers would save millions of pounds in costs for consumers through increased competition.

It would also save hundreds of thousands of tonnes of carbon emissions by avoiding warming conventional coal and gas power stations, while boosting the ESO’s plans to be able to operate a carbon-free grid by 2025 – an important milestone within the Government’s own 2050 net zero target.

Flexible demand companies and DERs would also secure revenue benefits for the provision of system restoration services.

Julian Leslie, Head of Networks at National Grid ESO, said:

We have one of the world’s most reliable electricity networks, but our role is to be prepared for the most extraordinary of scenarios, including a nationwide power outage.

This trial is a breakthrough moment for our Distributed ReStart project, which stands to improve system resilience and security of supply in a cleaner and cheaper way.

We are always innovating for a greener future and the huge growth of green energy sources on distribution networks presents an opportunity to reduce our reliance on fossil fuels and co-ordinate a system restoration process using renewables.

The concept of meeting our grid restoration needs by renewable generation alone has become closer to reality as a result of this trial.

Scott Mathieson, Network Planning and Regulation Director at SP Energy Networks, said:

The increasingly complex needs of our energy system, coupled with the significant increase in both demand and generation we need to accommodate on our transmission and distribution network, mean it is crucial we ensure the continued security and resilience of our electricity system.

We’re really encouraged by the results of this latest trial on the Distributed ReStart project, where we’re seeing a real opportunity for this innovative approach to improve resilience and timelines for system restoration.

Our customers are becoming increasingly dependent on their electricity supply for all of their activities, which is why we’re absolutely focused on ensuring we build the network we know they need now and long into the future.

Trial details

The live trial, led by SP Energy Networks, involved utilising the Kendoon hydro generator as the anchor (used to initially energise the network), along with multiple turbines at Glenchamber and North Rhins wind farms connected to the Glenluce 33 kV Grid Supply Point (GSP). In addition, a 33 kV loadbank was connected to the test network to simulate customer demand and allow the distributed energy resources (DER) to generate.

The trial successfully:

• energised primary (33/11 kV) transformers (up to 24 MVA) from the Kendoon hydro generator operating at normal voltage levels (11 kV)

• proved the Block Load Pick Up (BLPU) capability of the anchor generator (the amount of instantaneous demand which can be applied while maintaining the frequency above 47.5 Hz)

• energised the Glenchamber and North Rhins wind farm 33 kV cable arrays, and associated turbine transformers, from the anchor generator (initially all turbines were shut down)

• connected several wind turbines at Glenchamber and North Rhins wind farms to the ‘weak’ islanded network (supplied from Kendoon hydro) and proved stable turbine operation both in power factor and voltage control modes

• established a stable power island with Kendoon hydro and several turbines connected across Glenchamber and North Rhins wind farms simultaneously.

Notes to Editors

• More information on electricity system restoration is available here.

• DER include renewable sources of energy such as wind turbines, solar panels, embedded hydro-power generators, biomass generators and natural gas turbines.

• Two more live Distributed ReStart trials are planned for later this year.