New arrangements for rebooting power grid approved

Ofgem has approved a suite of modifications to energy industry codes to implement the new Electricity System Restoration Standard (ESRS) introduced by the government in a policy statement in April 2021.

The ESRS mandates that in the event of a total or partial shutdown of Great Britain’s power grid, the Electricity System Operator (ESO) must be able to restore 60% of demand on the transmission network within 24 hours, and 100% within five days.

It says these requirements must be met by the end of 2026.

The code modifications approved by Ofgem comprise:

• DCRP/MP/22/02 (Distribution Code) – Codifies the high-level requirements for the introduction of the “bottom-up” restoration method trialled as part of the ESO’s Distributed Restart project, including for the development and implementation of Distribution Restoration Zone Plans. Replaces references to “black start” with “electricity system restoration” to align the terminology in the code with the government’s ESRS policy statement.
• GC0156 (Grid Code) – Puts in place measures, tools and procedures to enable the ESO to implement the ESRS. These include requirements for generators and network substations to be able to continue operating for at least 72 hours following the loss of external electricity supplies, and for generators to be able to operate as part of a power island. Replaces references to ‘black start’ with ‘electricity system restoration’ and to ‘black start plant’ with ‘anchor plant.’ Introduces the new category of ‘top-up restoration’. Also defines the 24-hour restoration target in the ESRS as 60% of forecast peak demand on the transmission network over the 24-hour period following a shutdown.
• GSR032 (Security and Quality of Supply Standards) – Introduces requirements for transmission systems to be designed to facilitate participation in restoration plans, permit power stations to synchronise with power islands and prevent system collapse during restoration.
• CM089 and CM091 (System Operator Transmission Owner Code) – Align the STC with the Grid Code following the approval of GC0148 and GC0156 respectively. Require transmission owners to consider the impact of proposed outages on the ESRS.

All of the modifications will take effect 20 working days after their approval on Monday (5 February). Ofgem approved a series of modification to electricity network licence conditions to implement the ESRS in August 2021.

In December last year, the regulator approved several modifications to the Grid Code to protect critical sites from being disconnected during emergency load shedding.