Ofgem fast tracks blackout protections for critical sites

Ofgem has granted urgent status to a proposal to protect critical sites such as hospitals, airports and railways from being disconnected during emergency load shedding to prevent a wider shutdown of the power grid.

The issue was previously highlighted by the Energy Emergencies Executive Committee in its report into the blackout in August 2019, which caused widespread disruption to rail services around London as commuters made their way home during the Friday evening rush hour.

This was partly the result of emergency load shedding through the Low Frequency Demand Disconnection scheme, which also cut power to several hospitals and an airport.

The Grid Code sets out a number of tools and processes for disconnecting demand at short or no notice if the Electricity System Operator (ESO) is unable to keep the power grid in balance due to a generation shortfall or operational issues. The arrangements are detailed in Operating Code 6, which currently prohibits any discrimination in the application of demand control, meaning critical sites cannot be protected from being disconnected.

In June, Ofgem granted urgent status to the Grid Code modification GC0161 that would remove a section of text in OC6 that prevents demand control from discriminating between different groups of suppliers, network operators and non-embedded customers.

The modification would also remove another clause, which states that provisions in the government’s Electricity Supply Emergency Code (ESEC) to prevent the disconnection of protected sites, do not apply to demand control under the Grid Code.

According to the ESEC, sites should be protected from disconnection if their electricity supplies must be maintained because of a critical national or regional need, public health and safety issues, and the potential for damage to high value plant.

The protected sites listed in the code include electricity generators, oil and gas facilities, water and sewerage installations, essential telecommunications infrastructure, hospitals, major railways, airports, ports and docks, sites for key financial services, and certain factories such as for food production.

The ESEC, which sets out arrangements for demand control during longer, pre-warned events, also divides non-protected sites into a number of equally sized “load blocks”. During an emergency, disconnections would be rotated through these blocks to ensure that they each receive an equal share of the available electricity supplies.

GC0161 would similarly allow disconnections to be rotated between sites. However, the modification would only protect critical sites from being included in the first 20% tranche of demand to be disconnected by distribution network operators (DNOs) in the event of an emergency. Ofgem has not yet made a decision on whether to approve the modification.

The regulator has now granted urgent status to the modification GC0162 that would also allow critical sites to be protected from being included in the second tranche (20% to 40%).

Ofgem said it agreed with the majority view of the Grid Code Review Panel that the modification does meet its urgency criteria concerning the impact on the safety and security of the electricity system. However, the regulator said this is not for reasons outlined by the ESO, which proposed the modification and focused on the societal benefits of protecting critical sites.

In the “very unlikely” event of long demand disconnections, Ofgem said it is probable that demand control will first be enacted under the Grid Code then transitioned to the arrangements set out in the ESEC. In allowing DNOs to use “ESEC-style load blocks” to disconnect demand, the regulator said the modification will help to prevent block misalignment during this transition.

Ofgem acknowledged concerns raised by the Grid Code Review Panel over increased switching times for DNOs to enact the second tranche of demand control but said these concerns should be fully investigated and addressed as part of the development of the modification.

The regulator said the modification also meets its urgency criteria concerning the potential breach of legal requirements by a code party. It said the “current legal obligation preventing protections for critical sites could conflict with requests made to DNOs in certain circumstances.”

If approved, Ofgem said it is aiming to implement the modification by 15 December.