Long Term Stability Testing of Alternative Gases 2: C5F10O

Completed

Other Power and Storage Technologies(Electricity transmission and distribution)

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 April 2020

01 April 2021

ENA months

£200,000

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

The main work packages of the technical concept study are: (i) A specialist stainless test rig will be used to conduct the tests. First, the effect of discharges and flashover in the gas mixtures will be measured in terms of by-products. Both short term and long-term tests will be explored. An in-house technique employing a GCMS system will be used to analyze the gas by-products following incremental periods of time of discharges and number flashover events. A list of by-products will be developed for each mixture tested in this programme and its correlation with severity of electrical discharge activity will be quantified. Furthermore, for the above tests, comparison of NOVEC™ 5110 with its various mixtures with CO2 and/or N2 will be conducted (at 5, 10 and 20%). This will work will further help to indicate if any health and safety studies of the gas mixtures are required.(ii) The second major axis of this work is to investigate the stability of the gas and its mixtures. Building on the previous work of breakdown gas by-products analysis, quantifying the impact of the gas and its mixtures on the surrounding materials will be necessary to determine the long-term stability of the gas and the GIS system. In this case, various materials used in GIS technologies will be sourced (through National Grid) and investigated. Existing methods analysis of dielectrics will be considered and adapted for the gas mixtures in the presence of various materials and under various diverging electric field conditions. This work will determine the overall stability of the gas mixtures and their reaction with the surrounding materials. Scanning electron microscopes (SEM) will be used to investigate the changes of surface properties of various materials used in GIS systems. This will form a solid platform for future detailed analysis of the gas long term stability. This project will investigate the stability of the new gas mixture (Novec™ 5110 and other modified mixtures) in the presence of various materials and under different working pressures. Measurement of gaseous breakdown by-products when the gas mixture is subjected to electrical flashover and partial discharges will be carried out to understand their nature and their effect on the stability of the gas properties. An overview of the research into the health effects of the gas will also be conducted. The aim of this work is to gain a better understanding of the recently proposed alternative gases (C5F10O or Novec™ 5110) gas mixtures to replace SF6 gas. It will also enable obtaining a better understanding of the health and safety implications when using the newly proposed alternative gas mixtures, through by-products analysis. Moreover, it will allow the assessment of the stability of the new gas mixtures and their impact on surrounding equipment.The objectives of this work are to: quantify the impact of electrical discharges and flashover on the dielectric properties of the gas mixtures measure the by-products of the gas mixtures following flashover determine the impact of the gas mixtures and their by-products on surrounding materials. develop an indicator of gas mixture degradation and estimate long term stability.

Sulphur hexafluoride gas, SF6, is unique in its electrical and thermal performance. However, its Global Warming Potential, GWP, is very high at around 23900, compared with CO2 which has a GWP of one. Such negative impact on the environment led to the designation of the gas as a “Kyoto Gas”. In the UK, it is estimated that SF6 contributes 0.2% of the annual greenhouse emissions. In recent years, new gas molecules and mixtures of gases have been considered and tested. A number of candidates have been particularly studied, these include dry air, N2 or CO2, polyfluorinated gases especially Trifluoroiodomethane (CF3I), Perfluorinated Ketones, Octafluorotetra-hydrofuran, Hydrofluoroolefins (HFOs), and Fluoronitriles. This proposal is to extend the work being conducted on the stability of Novec™ 4710 and its mixtures under project NGTO002 to Novec™ 5110 (C5F10O) and its mixtures. Similar techniques, as developed for the Novec 4710™ gas mixtures project, will be adopted here.

02/11/22