0.4～0.8MPa气压下二元混合气体SF_6/N_2和SF_6/CO_2露点温度计算

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

金属封闭开关设备(gas insulated switchgear,GIS)和气体绝缘输电线路(gas insulated transmission line,GIL)等高压电力设备多采用提升气压的办法来提高SF6混合气体的绝缘强度,而随着气压的升高,混合气体的露点温度随之上升,在一定条件下,甚至超过了GIS和GIL设备的适用范围。该研究采用Peng-Robinson(PR)状态方程结合van der Waals混合规则(PR-vd W方法)分别对二元混合气体SF6/N2和SF6/CO2的汽液相平衡数据进行了计算,得到在0.4～0.8 MPa气压下,不同配比的SF6混合气体的露点温度。结果显示:对于目前使用的GIS和GIL设备,当气压分别为0.6、0.7和0.8 MPa,建议SF6/N2混合气体运行在SF6气体占混合气体摩尔分数分别<0.84、<0.74和<0.66的情况下,SF6/CO2混合气体运行在SF6气体占混合气体摩尔分数分别<0.77、<0.60和<0.47的情况下。且在GIS和GIL设备中,SF6/N2混合气体的环境适用范围较SF6/CO2混合气体的更广。

The gas pressure is usually increased so as to improve the electric strength of SF6 gas mixtures in gas insulated switchgear（GIS） and gas insulated transmission line（GIL）, leading to the increase of the dew temperature. As the dew temperature of gas mixtures increases, the liquefaction characteristics may be beyond the application scope of GIS and GIL considering the temperature of the operation environment. Therefore, we calculated the vapor-liquid equilibrium （VLE） data of SFJN2 and SFr/CO2, respectively, to get the dew temperature of gas mixtures under 0.4～0.8 MPa. The cal- culating model is based on the Peng-Robinson （PR） state equation using the classical van der Waals（vdW） mixing rule （namely PR-vdW method）. The results show that when the gas pressure of GIS and GIL is at 0.6, 0.7, 0.8 MPa, the mole fraction of SF6 in SF6/N2 gas mixtures should be controlled under 0.84, 074, and 0.66, respectively. And the mole fraction of SF6 in SF6/CO2 gas mixtures should be controlled under 0.77, 0.60, and 0.47, respectively. Therefore, SF6/N2 gas mix- tures have a wider range of application than SF6/CO2 gas mixtures in GIS and GIL.