The electricity system operator NGESO has set out the capabilities it needs to operate the electricity system through its rapid change to a renewables-based system, in its annual Operability Strategy Report. It summarises progress and upcoming issues in five aspects of system operation.
• The system operator says that inertia will experience a “notable and continuous decline”. It is procuring inertia to meet the shortfall through its Stability Pathfinders, and it can meet inertia requirements until 2027. It says, “We know that from 2027 our requirement will increase, and we continue to explore options for meeting this … Operating the system with low inertia will continue to represent a key operational challenge into the future and we will need to ensure we improve our understanding of the challenges this will bring.”
• Because system inertia is falling and supply and demand are more variable, NGESO says a “step change” is needed to manage frequency. That requires both response – it is using pre-fault services to manage frequency close to 50Hz and post fault services to contain the frequency following a fault – and ‘reserve’, which is manually activated and can be used to move frequency back towards 50Hz following the activation of response. It says, “our frequency control strategy is based around the need to contain and recover from sudden unplanned faults. However, the next big challenge may be around managing system imbalance during normal operation, as system imbalance grows to be more variable due to less predictable supply and demand patterns.”
• Thermal constraints that limit the amount of power that can be transported are among the most urgent issues, not least because strengthening the network can be subject to planning consent delays. The cost of redispatch to manage this issue is expected to rise significantly until new cables can be installed. NGESO has interim options to mitigate the effects, including intertripping generation, optimising outage patterns with better forecasting, and enhancing existing assets. It is also using commercial solutions such as an intertrip scheme on the Scotland-England boundary which will be available from October 2023. But NGESO says by 2030 some areas of the network will see peak power flows which are 400% greater than current boundary capability and reinforcement will be necessary.
• On voltage, NGESO says that it will need an additional 1,600MVAr of reactive power absorption by 2025 to manage voltage levels within the required limits, largely across the middle to south of England, because it will lose access to 3,600MVAr of reactive capacity by 2025, and an additional 1,000MVAr by 2030, through plant closures. Further work is planned which will identify the reactive power requirements out to 2030.
• The system operator has made substantial progress in using distributed assets to bring the system back on after a blackout – a facility, known as ‘black start’ it has to have in place. It says, “By the mid-2020s, we aim to be running a fully competitive restoration procurement process with submissions from a wide range of technologies connected at different voltage levels on the network”.
Read the full report here.