System Operability Framework (SOF)

Evolving year-on-year 

Through extensive industry interaction, the SOF evolves year‑on‑year to meet changing operational and stakeholder needs.

Growth of low carbon and renewable generation, closures of conventional thermal power stations and changing interactions across the whole of the power system are just a few of the areas considered in the context of a rapidly changing power system.

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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Operability Impact of Distributed Storage and Electric Vehicles

The high penetration of these devices would alter the demand seen by ESO control centre and impact the system operability. With appropriate market and framework design, storage and electric vehicles will be able to support electricity system operation and be enablers to the decarbonization transition.

Download the operability impact of distributed storage and electric vehicles document

Operating a Low Inertia System

We are always looking at how to best operate the network, as we see reductions in system inertia. We have processes in place for managing each operability challenge. We are already looking to address the future challenges we see ahead of us as we transition to a zero carbon system.

Download the operating a low inertia system document

Past Frequency Events

We control frequency by balancing electricity supply and demand. Occasionally we see a large loss of generation or demand which can cause a swing in system frequency. This report provides the brief summary of significant frequency events which has previously been provided in the System Incident report to the Grid Code Review Panel.

Download the past frequency events document

Impact of declining short circuit levels

We are identifying and quantifying system requirements which are affected by reductions in Short Circuit Level and we share some of our work in this document.

Download the Impact of declining SCLs document

Whole system short circuit level

Short circuit levels on the distribution networks are increasing driven by the growth in distributed generation and demand. This report looks at how these two trends interact and their net effect on the whole system.

Download the whole system SCL document

Regional Trends and Insights

Changes in the generation and demand are effecting how the power system is operated on a regional basis.

Find out about our latest analysis by downloading the report.

Download the regional trends and insights document

Voltage and Frequency Dependency 

Traditionally, voltage and frequency have been treated independently when considering operability. In the future, they will interact more.

Find out about our latest analysis by downloading the report.

Download the voltage and frequency document

Past SOF documents