ESO calls for review of security of supply standards following blackout

National Grid’s electricity system operator (ESO) has called for a review of the security and quality of supply standards (SQSS) to determine whether it is necessary to provide “higher levels of resilience”.

The ESO made the recommendation in its final report to Ofgem on the August blackout which left more than a million customers without power. The report will inform the regulator’s investigation into whether any of the network operators or generators involved breached their license conditions.

The customers were disconnected to prevent a wider power cut after the ESO was unable to contain a large frequency drop following unplanned outages by two large generators.

Some industry figures said the ESO should have had more frequency response to hand to counteract the losses. The ESO said it had enough available to meet the requirements of the SQSS in their current form.

As a “defensive measure”, the ESO increased its reserves of frequency response by 100MW in the days following the blackout. However, according to the report’s appendices, the body has since dropped this extra holding.

The report also recommends:

• A review of the low frequency demand disconnection (LFDD) scheme to ensure “no critical infrastructure or services are inadvertently placed at undue risk of disconnection”. Newcastle Airport was among the customers to be disconnected when the procedure was triggered.
• A review of the timetable for the industry programme to replace or recalibrate loss of mains protections for distributed generators to prevent so-called nuisance tripping. The incident was exacerbated by the disconnection of 500MW of distributed generations due to loss of mains protections.
• A review of communications processes and protocols, particularly during the first hour following an incident.
• A review of the settings on the internal protection systems on electric trains to ensure they can continue to operate through “normal” disturbances on the power grid. Around 60 trains unexpectedly shut down when the frequency of the power grid dropped below 49Hz. Half required a visit from a technician in order to restart.
• An assessment of whether it is necessary to establish standards for critical infrastructure and services “setting out the range of events and conditions on the electricity system that their internal systems should be designed to cater for”. Ipswich Hospital lost power during the blackout when its own protection systems were triggered.

A spokesperson for the ESO said: “We have been working hard, in parallel with colleagues across the industry to understand the causes of the 9 August power cuts and why it caused disruption to services across Great Britain.

“We have now published the final technical report submitted to our regulator Ofgem, which confirms the rare circumstances that led to the power cut and how the electricity system operated as it should and within the operational guidelines by which we are governed.

“We welcome Ofgem’s response and the opportunity to submit further reports to the Energy Emergencies Executive Committee enquiry, making sure any lessons learned and changes made are in the best interests of the consumer.”

Richard Black, director of the Energy and Climate Intelligence Unit, said the report raises questions about the regulator as well as the actions of the ESO and DNOs.

He added: “Perhaps the most interesting of the report’s recommendations centres on the smaller generators which tripped out automatically due to oversensitive sensors. The industry has been aware of this for at least 10 years, and yet under current plans it won’t be fixed until 2022, which the report suggests is inadequate.

“What it doesn’t say – because it’s a report to Ofgem – is that Ofgem as regulator has final responsibility for having allowed this fault to persist. It’ll be interesting to see whether MPs or any other body decide to look into the regulator’s apparent lack of interest in the issue.”

The interim report to Ofgem was published on 20 August.