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Britain’s National Energy System Operator (NESO) judges that the country’s energy system is well-protected against the sequence of events that led to April’s blackout in Iberia.
In a new paper reflecting on the April 28 blackout in Spain and Portugal, the NESO states that it has worked with the energy sector to implement rigorous planning, testing, monitoring and control measures to ensure the resilience of the power system.
Thus it has taken action to mitigate many of the risks seen in Iberia but must continue to build on existing planning, testing and system monitoring capabilities, particularly in voltage management.
The report is based on the published findings to date with the key conclusion that the blackout was caused by a series of cumulative circumstances, leading to a system overvoltage thus triggering a cascading shutdown of generation.
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Factors contributing to high voltages and the ability to manage that increase are the most pertinent with three main themes – oscillations, voltage and restoration.
Energy system management
On oscillations, the NESO says the incident highlights the importance of understanding, monitoring and reducing oscillations through modelling, simulations, testing and compliance.
Through its work with cross-industry partners and transmission owners, new measurement tools that can identify the presence of oscillations are monitoring the system.
The operator is working with the transmission operators to prioritise installation of further phasor measurement units as additional capability to monitor and measure oscillations and looking ahead will work with network owners to expedite plans to increase real time monitoring across the network.
Considering voltage instability, which was a key contributing factor to the incident, the NESO reports recognising the trend toward increasing voltage fluctuations and is taking steps to manage.
New reactive power markets to procure additional voltage regulation services through competition have been developed and should improve the voltage situation significantly in the short to medium term.
Modelling is an area for improvement in medium to long term timescales for both NESO and the transmission owners. For example, modelling could be improved to account of market sensitivities and asset availability
Restoration in the GB system is carried out using a designated fleet of power stations and interconnectors that are contracted for restoration services. To ensure maintaining the capability to restore the system, the NESO reports having adapted its restoration contracting strategy to include a range of new technologies both at transmission and distribution level.
Other efforts include enhanced operational coordination with network companies, partnerships with industry and academic institutions for research and development and engagement with international system operators to learn from diverse restoration strategies.
The NESO is mandated to ensure sufficient capability and arrangements are in place by 31 December 2026 to restore 100% of the GB’s electricity demand within five days. This requirement must also be implemented at a regional level, with an interim target of restoring 60% of regional demand within 24 hours.
This new standard represents a significant advancement over the current system restoration expectations for NESO.
As the NESO, ensuring a safe and secure electricity supply is at the heart of everything it does, the operator says in a statement.
“NESO has a responsibility to learn from major incidents that happen elsewhere. Even though GB has one of the most reliable networks in the world – a record NESO, network operators, and the whole energy industry work tirelessly to maintain – exploring every opportunity for learning and improvement is essential.”
Vincent Thornley, managing director of UK voltage control company Fundementals, said the NESO report “is a timely reminder that Britain’s energy grid, built in the 1950s is being tasked with doing things which it was never designed to cope with.”
He said the report “rightly flags voltage instability as a growing risk”.
“Connecting thousands of low-carbon technologies, including EV chargers, heat pumps and community batteries, to an ageing system demands smarter power flow management and voltage compliance.
“To secure resilience, we need a whole-system approach to voltage control, spanning both low and high voltages. Smarter strategies across the grid will allow system owners and operators to use existing assets more efficiently, delay costly reinforcement and replacement. This will ultimately protect customers and future-proof the network.”
