Abstract
Sulphur hexafluoride (SF6), the most popular dielectric medium adopted in compressed gas insulated equipment, has been identified as a highly potent greenhouse gas. This has led to increased interest in finding a more environmentally friendly replacement candidate. In this paper, the technical viability of C3F7CN/CO2 gas mixtures was assessed as a potential retro-fill solution for existing SF6-filled gas insulated lines (GIL) and busbars (GIB). A reduced-scale coaxial prototype was developed to establish the breakdown strength of 20% C3F7CN / 80% CO2 and 16% C3F7CN / 84% CO2 gas mixtures in direct comparison with pure SF6 under the standard lightning impulse (1.2/50 μs). Breakdown results demonstrate that a mixture of 20% C3F7CN / 80% CO2 exhibits comparable insulation capability to pure SF6 in coaxial geometries with similar field uniformity to GIL / GIB. This initial finding has led to the construction of a full-scale GIB demonstrator rated for 420/550 kV. Type tests according to IEC 62271-204 showed that the 20% C3F7CN / 80 % CO2 gas mixture has passed all the required voltage levels as SF6. The research findings in this paper are an encouraging step towards a technically viable SF6-free retro-fill solution for existing GIL / GIB installed for the 400 kV transmission network in the UK.
Original language | English |
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Article number | 9019889 |
Pages (from-to) | 2394-2402 |
Number of pages | 9 |
Journal | IEEE Transactions on Power Delivery |
Volume | 35 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2 Mar 2020 |
Keywords
- Heptafluoro-iso-butyronitrile (C3F7CN)
- gas insulation
- gas insulated lines and busbars
- lightning impulse breakdown
- sulphur hexafluoride (SF6)
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Retrofill replacement of SF6 to accelerate the decarbonisation of electricity networks
Chen, T. (Participant)
Impact: Economic, Environmental, Policy, Technological
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