Introduction: 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.

Objectives: 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.