National Grid ESO has raised an urgent Grid Code modification that would allow it to disconnect embedded generation.
The modification – raised on 30 April – will clarify the ESO’s legal powers to instruct DNOs to disconnect embedded generation. This is classified as generation that is connected to the distribution network, for example domestic solar and battery storage.
This applies to embedded generation that is not part of the Balancing Mechanism (BM), with the ESO already having the ability to turn down and disconnect BM participants.
The modification has been raised due to the current challenges faced by the ESO in balancing the grid due to the dramatic drop in demand seen as a result of the COVID-19 lockdown.
Demand has, the ESO said, dropped 20% lower than predicted levels, a situation it said in its Summer Outlook report that would cause it to use its existing balancing services more often as well as create new sources of flexibility and curtail wind output in particular.
As a result, it is requesting the ability to disconnect embedded generation as “a last resort” to maintain system stability during periods of exceptionally low demand.
Whilst the ESO said it is establishing a new service for downward flexibility management to mitigate the operational risks caused by COVID-19, it “may be necessary to seek to control embedded generators” if all commercially available options through the new service and the BM have been taken.
Embedded generators that are not part of the BM but are disconnected will not be compensated for the emergency action, it said.
Outlining an implementation date of 7 May, the ESO stressed the importance of having this in place prior to the 8 May bank holiday, when it expects particularly low demand and “significant operational risk”.
Currently, it said, the Grid Code shows its ability to make these instructions is "ambiguous" and leaves DNOs in a position that may expose them to legal risk, resulting in the need for clarity through the modification.
If the modification goes ahead, there are a number of instructions National Grid ESO may give, including:
- Specific instructions requiring the network operator to disconnect specified embedded power stations.
- Asking the network operator to disconnect embedded power stations supplied via one or more specified Grid Supply Points with an aggregate Registered Capacity of a specified value.
- Asking the network operator to disconnect embedded power stations supplied via one or more specified Grid Supply Points so that a specified proportion of the aggregate Registered Capacity is disconnected.
However, the ESO is looking to establish a more considered solution, suggesting a potential option of the development of a roughly symmetrical arrangement to the existing demand conditions in section OC6 of the Grid Code. To support this, it has included a sunset clause that will time out the additions to the Grid Code in October 2020 if not further amended.
Ofgem must approve the modification for it to be implemented, with a decision due 7 May.
The full modification proposal form can be read here.