Projects

Started

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering)

Not Cross-cutting

Project Contact
National Grid Electricity Transmission

Network Innovation Allowance

Ofgem

01 September 2025

30 September 2026

ENA months

£464,335

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

The need for partial discharge (PD) and gas species monitoring inside the switchgear will be investigated by recording and analysing the PD activity before and after arcing in a laboratory set-up. Arcs in a representative gas mixture containing C4-FN will be generated between a pair of contacts and PD sensors placed at a location that reflects the arcing effect and transport of the active species and by-products in the gas environment.An existing switching arc model, developed for simulating the arcing process in SF6, will be adopted to the SF6 alternative gas by implementing a set of real gas material properties for the SF6 alternative gas mixture,solving an additional species concentration equation to quantify the variation of the active species,and adding new source terms to represent the consumption of the active species.Numerical simulation will then be performed on a model gas blast circuit breaker under conditions typical to Type Test duties to characterise the local change of the concentration of the active species as well as the influence of the gas flow and diffusion on the transport of the active insulation species during and immediately after the highly transient arcing process. Based on the findings, the technical need and key requirement for online sampling of the gas medium inside circuit breakers will be established to propose a method for real time monitoring of the active species. The SATPaSS project is a 12-month research initiative examining whether current Type Testing standards and procedures remain adequate for SF6-free switchgear technologies employing C4-FN gas mixtures. The project specifically focuses on analysing the unique behaviours and characteristics of these alternative insulating and interruption gases compared to SF6, particularly regarding their stability, distribution, and performance following high-current switching operations.The project encompasses three integrated work packages:Review of existing standards and Type Testing procedures to identify gapsComputational modelling of C4-FN gas behaviour during switching operationsExperimental assessment of partial discharge behaviour and development of monitoring methodologiesThe research addresses critical knowledge gaps in the long-term reliability of SF6-free technologies that current Type Testing procedures may not adequately evaluate, focusing on uniformity of gas distribution, partial discharge patterns, stability of gas mixtures, and material compatibility concerns. The objectives of this project are toIdentify potential gaps in Type Testing regimes and international standards for SF6-free switchgear, particularly circuit breakers.Develop a computational model to predict dynamic composition changes and distribution of C4-FN inside gas-blast circuit breakers.Assess potential long-term operational and maintenance risks associated with C4-FN gas mixtures in transmission network assets.Generate empirical evidence regarding changes in partial discharge behaviour in C4-FN mixtures following current interruption.Propose methodologies for active species monitoring in SF6-free switchgear.

There are knowledge gaps on the behaviour of SF6 alternative gases, especially for the C4-FN mixtures being used widely in GB networks. Type test procedure/standards developed for the SF6 gas may need to be updated for the non-SF6 gas mixtures especially for switching applications. A comprehensive literature review, experiment and arc modelling will be conducted to 1) understand the key aspects of the circuit breaker Type Testing standards and procedures and summarise the gaps in technical specifications in relation to the adoption of SF6 alternative technologies in the power grids, and 2) present and analyse the existing evidence in relation to the long-term variation in composition of the mixtures of C4-FN with CO2, CO2/O2, or N2/O2 in a switching environment.

24/04/26