# Research on Liquefaction Characteristics of SF6 Substitute Gases

• Yuan, Zhikang (State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University) ;
• Tu, Youping (State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University) ;
• Wang, Cong (State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University) ;
• Qin, Sichen (State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University) ;
• Chen, Geng (State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University)
• Accepted : 2018.03.27
• Published : 2018.11.01

#### Abstract

$SF_6$ has been widely used in high voltage power equipment, such as gas insulated switchgear (GIS) and gas insulated transmission line (GIL), because of its excellent insulation and arc extinguishing performance. However, $SF_6$ faces two environmental problems: greenhouse effect and high liquefaction temperature. Therefore, to find the $SF_6$ substitute gases has become a research hotspot in recent years. In this paper, the liquefaction characteristics of $SF_6$ substitute gases were studied. Peng-Robinson equation of state with the van der Waals mixing rule (PR-vdW model) was used to calculate the dew point temperature of the binary gas mixtures, with $SF_6$, $C_3F_8$, $c-C_4F_8$, $CF_3I$ or $C_4F_7N$ as the insulating gas and $N_2$ or $CO_2$ as the buffer gas. The sequence of the dew point temperatures of the binary gas mixtures under the same pressure and composition ratio was obtained. $SF_6/N_2$ < $SF_6/CO_2$ < $C_3F_8/N_2$ < $C_3F_8/CO_2$ < $CF_3I/N_2$ < $CF_3I/CO_2$ < $c-C_4F_8/N_2$ < $C_4F_7N/N_2$ < $c-C_4F_8/CO_2$ < $C_4F_7N/CO_2$. $SF_6/N_2$ gas mixture showed the best temperature adaptability and $C_4F_7N/CO_2$ gas mixture showed the worst temperature adaptability. Furthermore, the dew point temperatures of the $SF_6$ substitute gases at different pressures and the upper limits of the insulating gas mole fraction at $-30^{\circ}C$, $-20^{\circ}C$ and $-10^{\circ}C$ were obtained. The results would supply sufficient data support for GIS/GIL operators and researchers.

#### Acknowledgement

Supported by : Central Universities

#### References

1. Y. Deng and D. Xiao, "Analysis of the insulation characteristics of $CF_3I$ gas mixtures with Ar, Xe, He, $N_2$, and $CO_2$ using Boltzmann equation method," Japanese Journal of Applied Physics, vol. 53, no. 9, pp. 3253-3259, 2014.
2. W. Xing. "Basic study on c-$C_4F_8$/$N_2$ Gas mixtures substituting using For $SF_6$ in electrical apparatus," PhD diss., Chinese Academy of Sciences, pp. 27-28, 2011.
3. L. Zhang, "Study on insulation characteristics of c-$C_4F_8$ and its gas mixtures substituting $SF_6$," PhD diss., Shanghai Jiao Tong University, pp. 77-79, 2007.
4. H. Zhao, X. Li and H. Lin, "Insulation Characteristics of c-$C_4F_8$-$N_2$ and $CF_3I$-$N_2$ Mixtures as Possible Substitutes for $SF_6$," IEEE transaction on power delivery, vol. 32, no. 1, pp. 254-262, 2017. https://doi.org/10.1109/TPWRD.2016.2587898
5. D. Peng, D. Robinson, "A new two-constant equation of state," Industrial and Engineering Chemistry Research Fundamentals, vol. 15, no. 1, pp. 59-64, 1976.
6. T. Kwak and G. Mansoori, "Van der waals mixing rules for cubic equations of state. Applications for supercritical fluid extraction modelling," Chemical Engineering Science, vol. 41, no. 5, pp. 1303-1309, 1986. https://doi.org/10.1016/0009-2509(86)87103-2
7. E. Lemmon, M. Huber, M. Mclinden, Reference Fluid Thermodynamic and Transport Properties (REFPROP), NIST Standard Reference Database 2.3, version 9.0. Thermophysical Properties Division, National Institute of Standards and Technology: Boulder, USA, 2010.
8. R. Watson, "Common themes for ecologists in global issues," Journal of Applied Ecology, vol. 36, no. 1, pp. 1-10, 1999. https://doi.org/10.1046/j.1365-2664.1999.00390.x
9. J. Devins, "Replacement gases of SF6," IEEE Transactions on Electrical Insulation, vol. 15, no. 2, pp. 81-86, 1980.
10. L. Christophorou, J. Olthoff, R. Brunt, "Sulfur hexafluoride and the electric power industry," IEEE Electrical Insulation Magazine, vol. 13, no. 5, pp. 20-24, 1997. https://doi.org/10.1109/57.620514
11. N. Malik, A. Qureshi. "A review of electrical breakdown in mixtures of SF6 and other gases," IEEE Transactions on Electrical Insulation, vol. 14, no. 1, pp. 1-13, 1979.
12. D. Xiao, "Development prospect of gas insulation based on environmental protection," High Voltage Engineering, vol. 42, no. 4, pp. 1035-1046, 2016.
13. X. Li, H. Zhao, "Review of research progress in $SF_6$ substitute gases," High Voltage Engineering, vol. 42, no. 6, pp. 1695-1701, 2016.
14. Y. Qiu, "Dielectric strength of $SF_6$/$N_2$ and $SF_6$/$CO_2$ gas mixtures," Journal of Xi'an Jiaotong University, vol. 19, no. 3, pp. 9-16, 1985.
15. H. Uhm, Y. Byeon, K. Song, E. Choi, H. Ryu and J. Lee, "Analytical investigation of electrical breakdown properties in a nitrogen-$SF_6$ mixture gas," Physics of Plasmas, vol. 17, no. 11, pp. 1291-1298, 2010.
16. Y. Tu, Z. Yuan, B. Luo, C. Wang, X. Zeng and X. Dong, "Calculation on dew temperatures of binary gas mixtures $SF_6$/$N_2$ and $SF_6$/$CO_2$ under 0.4-0.8 MPa gas pressures," High Voltage Engineering, vol. 36, no. 5, pp. 1446-1450, 2015.
17. P. Osmokrovic, M. Stojkanovic, K. Stankovic, M. Vujisic and D. Kovacevic, "Synergistic effect of $SF_6$ and $N_2$ gas mixtures on the dynamics of electrical breakdown," IEEE Transactions on Dielectrics and Electrical Insulation, vol. 19, no. 2, pp. 677-688, 2012. https://doi.org/10.1109/TDEI.2012.6180263
18. B. Wu, D. Xiao, Z. Liu, L. Zhang and X. Liu, "Analysis of insulation characteristics of c-$C_4F_8$ and $N_2$ gas mixtures by Monte Carlo method," Journal of Physics D-Applied Physics, vol. 39, no. 19, pp. 4204-4207, 2006. https://doi.org/10.1088/0022-3727/39/19/012
19. Z. Yuan, Y. Tu, C. Wang, Y. Zhao, X. Dong, "Experimental research on (vapor + liquid) equilibria for the {trifluoroiodomethane ($CF_3I$) + carbon dioxide ($CO_2$)} system from 243.150 to 273.150 K," Journal of Chemical Thermodynamics, no. 101, pp. 49-53, 2016.
20. L. Chen, P. Widger, M. Kamarudin, H. Griffiths and A. Haddad, "$CF_3I$ Gas Mixtures: Breakdown Characteristics and Potential for Electrical Insulation," IEEE Transactions on power delivery, vol. 32, no. 2, pp. 1089-1097, 2017. https://doi.org/10.1109/TPWRD.2016.2602259
21. M. Hikita, S. Ohtsuka, S. Okabe and G. Ueta, "Breakdown Mechanism in $C_3F_8$/$CO_2$ Gas Mixture under Non-uniform Field on the Basis of Partial Discharge Properties," IEEE Transactions on Dielectrics and Electrical Insulation, vol. 16, no. 5, pp. 1413-1419, 2009. https://doi.org/10.1109/TDEI.2009.5293955
22. H. Zhao, X. Li, and H. Lin, "Insulation Characteristics of c-$C_4F_8$-$N_2$ and $CF_3I$-$N_2$ Mixtures as Possible Substitutes for $SF_6$," IEEE Transactions on power delivery, vol. 32, no. 1, pp. 254-262, 2017. https://doi.org/10.1109/TPWRD.2016.2587898
23. S. Zhao, D. Xiao, H. Zhang and Y. Deng, "Discharge Characteristics of $CF_3I$/$N_2$ Mixtures under Lightning Impulse and Alternating Voltage," High Voltage Engineering, vol. 24, no. 5, pp. 2731-2737, 2017.
24. H. Koch, Gas-insulated transmission lines(GIL), 1st ed., John Wiley & Sons Inc, New Jersey, 2012.
25. Y. Deng, D. Xiao, J. Chen, "Insulation Performance of $CF_3I$-$N_2$ Gas mixtures as alternative for $SF_6$ in GIS/C-GIS," High Voltage Engineering, vol. 39, no. 9, pp. 2288-2293, 2013. https://doi.org/10.3969/j.issn.1003-6520.2013.09.032
26. H. Katagiri, H. Kasuya, H. Mizoguchi and S. Yanabu, "Investigation of the performance of $CF_3I$ gas as a possible substitute for $SF_6$," IEEE Transactions on Dielectrics and Electrical Insulation, vol. 15, no. 5, pp. 1424-1429, 2008. https://doi.org/10.1109/TDEI.2008.4656252
27. Y. Deng and D. Xiao, "The effective ionization coefficients and electron drift velocities in gas mixtures of $CF_3I$ with $N_2$ and $CO_2$ obtained from Boltzmann equation analysis", Chinese Physics B, vol. 22, no. 3, pp. 035101, 2013. https://doi.org/10.1088/1674-1056/22/3/035101