TY - JOUR
T1 - Technical Viability of Retro-filling C3F7CN/CO2 Gas Mixtures in SF6-designed Gas Insulated Lines and Busbars at Transmission Voltages
AU - Loizou, Loizos
AU - Chen, Tony
AU - Liu, Qiang
AU - Cotton, Ian
AU - Waldron, Mark
AU - Owens, John
N1 - Funding Information:
Manuscript received October 18, 2019; revised November 27, 2019; accepted January 10, 2020. Date of publication March 2, 2020; date of current version September 23, 2020. This work was supported in part by a Ph.D. studentship from the Engineering and Physical Sciences Research Council (EPSRC), Industrial Cooperative Awards in Science & Technology, and in part by National Grid, UK. The authors also acknowledge EPSRC for support through ‘High Voltage Test Systems for Electricity Network Research’ under Grant EP/P030343/1. Paper no. TPWRD-01190-2019. (Corresponding author: Lujia Chen.) Loizos Loizou, Lujia Chen, Qiang Liu, and Ian Cotton are with the Department of Electrical and Electronic Engineering, The University of Manchester, Manchester M13 9PL, U.K. (e-mail: loizos.loizou@manchester.ac.uk; lujia.chen@ manchester.ac.uk; qiang.liu@manchester.ac.uk; ian.cotton@manchester.ac.uk).
Publisher Copyright:
© 1986-2012 IEEE.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/3/2
Y1 - 2020/3/2
N2 - 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.
AB - 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.
KW - Heptafluoro-iso-butyronitrile (C3F7CN)
KW - gas insulation
KW - gas insulated lines and busbars
KW - lightning impulse breakdown
KW - sulphur hexafluoride (SF6)
U2 - 10.1109/TPWRD.2020.2967582
DO - 10.1109/TPWRD.2020.2967582
M3 - Article
VL - 35
SP - 2394
EP - 2402
JO - IEEE Transactions on Power Delivery
JF - IEEE Transactions on Power Delivery
SN - 0885-8977
IS - 5
M1 - 9019889
ER -