‘No technical barriers’ to rebooting power grid using distributed energy

Distributed energy resources, including solar and wind farms, can be used reboot the power grid following a blackout, National Grid Electricity System Operator (ESO) has stated in a new report.

However, the ESO has also highlighted a raft of technical and operational challenges that will need to be overcome before it can offer so-called black start services.

At the moment, black start services are provided by large transmission-connected power stations with backup generators that enable them to start up without access to an external power source.

In the case of a blackout, these power stations are used as an “anchor” for the reboot process, supplying electricity to other plants that cannot be restarted by themselves.

But with many of these facilities set to retire, the ESO is looking to distributed energy resources (DER) – smaller assets connected to distribution networks – as an alternative.

Alongside SP Energy Networks and the consultancy TNEI, the ESO launched a three-year programme at the beginning of 2019 with the aim of demonstrating the use of DER to provide black start services by mid-2022, provided it is shown to be cost-effective and feasible.

The ESO has now published some preliminary findings for the project, dubbed Distributed ReStart.

Following a “thorough analysis of the existing technical capability of DER and distribution networks”, the body has concluded that providing black start services using DER is “potentially technically viable on a GB-wide basis”.

There is currently 4GW of distributed generation connected at the 33kV level, which could potentially provide black start services, and this figure is set to double if all of the projects with a connection agreement are completed as planned.

The ESO said “no technical issues have been identified which would prove insurmountable to the concept of providing black start services from DER”.

But, the report added that “many technical challenges do exist which will require further exploration in future stages of the project”.

For instance, anchor generators will need to provide frequency and voltage control – most potential candidates are currently lacking this capability.

The vast majority also lack sufficient backup generation to self-start. In instances where backup generation is available, it sometimes comes in the form of battery storage, which can only provide power for a few hours.

Furthermore, the power islands created during the restart process will need a new method of earthing as they will be isolated from the existing earthing transformers. This will require the installation of new earthing transformers at most anchor generator installations.

The ESO originally intended to conduct full live trials during 2021. However, based on the findings it has decided to instead begin with trials of individual elements of the black start process, starting in 2020.