Feasibility of C ₃ F ₇ CN/CO ₂ gas mixtures in high‐voltage DC GIL: a review on recent advances

Abstract

With the rise of renewable energy resources, especially offshore wind power plant, the DC transmission concept has attracted more and more attention. The selection of eco‐friendly insulating gas, as most critical insulating part of gas‐insulated equipment is top priority for developing highly reliable system. Moreover, it is acknowledged that eco‐friendly C3F7CN/CO2 gas mixtures have become a potential alternative to SF6 gas due to its excellent performance. This study reviews the basic physical properties of C3F7CN gas/gas mixtures and insulation properties including the gas gap breakdown and surface flashover performance at DC, as well as lightning impulse voltage. Investigation about the gas stability is presented, including the compatibility of gas with solid materials in gas‐insulated transmission line (GIL), and the decomposition characteristics under long‐term electrical and thermal stresses. The important progress on the charge accumulation characteristics of gas–solid interface in the novel gas environment under DC voltage stress is analysed. Finally, the key issues that need to be paid attention to and further followed through regarding the application of this novel gas in GIL are summarised and put forward. This study hopefully can provide a complete reference for the development of eco‐friendly DC gas insulation equipment with C3F7CN/CO2 gas mixtures.

Review of the decomposition characteristics of eco‐friendly insulation gas

“…(2) SF 6 with N 2 or CF 4 gas mixtures [14,15]; (3) CF 3 I, c-C 4 F 8 with N 2 or CO 2 gas mixtures [16][17][18][19] [3,20]. From a long-term perspective, the use of SF 6 and its gas mixtures cannot fundamentally solve environmental issues, and the use of natural gases brings about the problem of mechanical and electrical structure redesign and manufacturing, together with a sharp rise in costs.…”

“…In recent years, hundreds of eco-- 1 friendly alternative gases and their binary or multi-component mixtures have been studied internationally, among which CF 3 I, c-C 4 F 8 , C 5 F 10 O, C 6 F 12 O and C 4 F 7 N are considered to have good application prospects due to their excellent properties such as high insulation strength and low GWPs. C 4 F 7 N gas insulated 420kV GIL and 145 kV GIS, C 5 F 10 O gas insulated 22kV ring switch cabinet and C 6 F 12 O gas insulated C-GIS equipment have been developed [11][12][13][14][15][16][17][18][19][20].…”

“…Searching for SF 6 alternative gases is a prominent topic in the electric power industry [11,12]. The main alternative gases include (1) CO 2 , N 2 , dry air and other natural gases [13]; (2) SF 6 with N 2 or CF 4 gas mixtures [14,15]; (3) CF 3 I, c-C 4 F 8 with N 2 or CO 2 gas mixtures [16][17][18][19]; (4) C 5 F 10 O and C 6 F 12 O with N 2 or CO 2 gas mixtures; (5) C 4 F 7 N with N 2 or CO 2 gas mixtures [3,20]. From a long-term perspective, the use of SF 6 and its gas mixtures cannot fundamentally solve environmental issues, and the use of natural gases brings about the problem of mechanical and electrical structure redesign and manufacturing, together with a sharp rise in costs.…”

Research on Steady‐State Thermal Behavior ofSF6/N2andCF3I/N2Mixtures in High Voltage Gas‐Insulated Lines (GIL)

“…High voltage (HV) gas‐insulated transmission lines (GIL) is widely used in power plants and substations. Currently, more than 200 km of GIL are installed worldwide at voltage levels from 135 to 1100 kV [1, 2]. GIL has many advantages such as less occupied area, easy installation, high operational safety and high reliability.…”

Research on discharge phenomenon caused by cross‐adsorption of linear insulating fibre and metal dust under DC voltage

“…The Gas-Insulated Transmission Line (GIL) has large transmission capacity, low environmental requirements, and meets the requirements of modern power systems, and has received more and more attention [1][2][3]. During the on-site installation process, due to the poor installation environment conditions, inadequate control of on-site installation and inspection and cleaning before capping was not strictly performed in accordance with process documents, impurities are likely to be brought in or left behind [4].…”