Experimental Study on Power Frequency Breakdown Characteristics of C₄F₇N/CO₂ Gas Mixture Under Quasi-Homogeneous Electric Field

Abstract

As a new environmental-friendly gas insulating medium, perfluoroisobutyronitrile (C 4 F 7 N) has been widely concerned in recent years due to its relatively low global warming potential and excellent dielectric strength, which has the potential to replace the most greenhouse gas, sulfur hexafluoride(SF 6). However, there are a few systematic studies on the influence of gas pressure and mixing ratio on the dielectric strength of C 4 F 7 N/CO 2 gas mixture at present. In this paper, the power frequency breakdown characteristics of C 4 F 7 N/CO 2 gas mixture under different pressure and mixing ratio conditions were tested using the gas insulation performance test platform. The optimal mixing ratio and pressure range of C 4 F 7 N/CO 2 gas mixture for engineering application were also discussed. It is found that the breakdown voltages of C 4 F 7 N/CO 2 gas mixture show a saturated growth trend with gas pressure and mixing ratio. The breakdown voltage of the gas mixture with 10% C 4 F 7 N can reach 80% of pure SF 6 under the same condition. The insulation performance of the gas mixture with 20% C 4 F 7 N can reach more than 95% of pure SF 6. Relevant results indicate that the gas mixture with 4%-12% C 4 F 7 N has the potential to be applied to high-voltage gas-insulated equipment. INDEX TERMS C 4 F 7 N/CO 2 , SF 6 alternative gas, quasi-homogeneous electric field, power frequency breakdown characteristics.

Green Gas for Grid as an Eco-Friendly Alternative Insulation Gas to SF6: A Review

“…where p and p c are the partial pressure and critical pressure of gas mixtures, and T and T c are the thermodynamic temperature and critical temperature, respectively [27,58].…”

“…Liquefaction temperature of the gas mixture at different gas ratios and pressures. (a) Novec TM /Nitrogen (N2) [27] and (b) Novec TM /CO2 [58].…”

Environment-Friendly and Efficient Gaseous Insulator as a Potential Alternative to SF6

“…All experimental results were obtained at room temperature (20-25 • C). The pressure vessel's temperature rise has been avoided by the interval of 5 min between two consecutive breakdowns as recommended in [14]. Testing vessel for vacuum and gas is made of steel and equipped with a pressure gauge to measure pressure up to 6 bars.…”

“…This novel alternative R152a/CO 2 gas mixture has been particularly developed to significantly reduce GWP as compared to SF 6 . According to environmental protection view, the GWP is calculated as a weighted average of this proposed gas mixture, and from the sum of the weight fractions of each substance and multiplied with their individual GWP as given in Equation (4) where k shows the base gas mixing ratio, 140 is the GWP of R52a and 44 and 56 is the molar mass of R152a and CO 2 respectively [14].…”

“…Therefore, molecular filters were used for harmless exclusion and absorption purposes [4]. Earlier investigations were carried out to expand CF 3 I/N 2 [5][6][7][8][9], C 5 F 10 O [10,11], C 6 F 12 O [12], C 3 F 7 CN [13] and C 4 F 7 N [14] as an alternate of SF 6 , but these candidates have some disadvantages described in Table 1. Gases cannot be maintained in a closed vessel, according to IEC 62271-1 standard there will be a 0.1% leakage from a closed vessel [15].…”