System Operability Framework (SOF)

Power Quality in the GB Transmission Network

Power quality is critical to the performance of the plant and equipment connected to the power network. Poor power quality can reduce the efficiency, cause excessive heating or even damage the assets. Driven by the net zero targets, the penetration of Inverter-Based Resources (IBR) will continue to increase, which will reduce the system strength in certain areas of the network.

There is a direct correlation between system strength, traditionally measured by the Short Circuit Levels (SCL), and some of the power quality aspects, including harmonics, voltage unbalance and voltage flicker. This report discusses the main power quality aspects in the future GB transmission network.

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Provision of short circuit level data

This paper explores options for how to define and reference short circuit level (SCL) for new and existing connections to the GB electricity system. This is required as more non-synchronous generation connects to the electricity system, alongside a reduction in traditional synchronous generators, impacting system stability. We describe why short circuit level is important and explore several options as to how short circuit requirements could be defined for new and existing generation. We are also seeking feedback from industry as to which of these options provides the optimum solution for defining short circuit level.

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Removing barriers to flexibility on the grid: interconnection

By 2025 interconnectors will become a key source of flexibility and will constitute a significant portion of the overall generation mix. Accessing flexibility and ancillary services on interconnectors will become key for system operability and an important pillar in our ambition for competition everywhere. So, following the publication of the BEIS Smart Systems and Flexibility plan, we’ve been looking into the barriers to interconnector participation in the Dynamic Containment market. Our report outlines those barriers and what mitigating actions could be taken.

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National Trends and Insights

The UK’s transition to a low carbon economy is bringing many new challenges and opportunities to how National Grid ESO operates the GB electricity system, with flexibility becoming an increasingly valuable characteristic. As the Electricity System Operator, we are continuously working with industry stakeholders to transform our operations and delivering the right market solutions at the right time to benefit the end consumer. This document takes the output of National Grid’s ETYS and NOA processes in 2020 and looks further into the technical issues which may need to be addressed for the successful operation of a low carbon electricity system.

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Low Demand - Operability Challenges from COVID-19 (Spring and Summer 2020)

The COVID-19 pandemic led to partial or total lockdowns in Great Britain in the spring of 2020, which in turn caused a reduction in electricity demand. This low demand, combined with large renewable output at times, resulted in a high penetration of non-synchronous machines on the system. This combination led to challenges with demand forecasting and maintaining flexibility for system integrity, voltage profiles and system stability. This paper provides a brief on the challenges in 2020 which National Grid ESO faced, the measures applied to tackle the challenges and the work we will look to carry out to improve the system operability in the future.

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The potential operability benefits of Virtual Synchronous Machines and related technologies

We at National Grid ESO are always looking at ways to enable new technologies to connect to the network in the most safe, secure and efficient manner. This report discusses how new technologies can support system stability by adopting Virtual Synchronous Machine (VSM) technologies and associated control approaches which will enable transition to a zero carbon system.

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More reports

Past SOF documents