Negative DC Dielectric Breakdown Characteristics and Synergistic Effect of HFO-1336mzz(E) Mixtures

HFO-1336mzz(E), a substitute for sulfur hexafluoride (SF6), has received much attention owing to its excellent insulation and environmental performance. To provide a reference for selecting suitable buffer gas type and mixing ratio in engineering applications, this article investigated the saturated vapor pressure characteristics, negative direct current (-dc) breakdown properties, and synergistic effect of HFO-1336mzz(E)/CO2 and HFO-1336mzz(E)/N-2 mixtures. Experimental results show that although the allowable percentage of HFO-1336mzz(E) in the HFO-1336mzz(E)/CO2 mixture is lower than that of the HFO-1336mzz(E)/N(2 )at the same gas pressure and limiting temperatures, the former one has a higher breakdown voltage in the gas pressure range from 0.1 to 0.7 MPa. Compared with HFO-1336mzz(E)/N-2, the shorter distance within the bimolecular composite structures of HFO-1336mzz(E)/CO2 leads to stronger interaction energy (Eint). As a result, HFO-1336mzz(E)/CO2 has a better synergistic effect in view of breakdown voltage. Based on the comprehensive analysis of saturated vapor pressure, liquefaction temperature, and insulation properties of HFO-1336mzz(E)/buffer gas mixtures, CO2 is superior as a buffer gas to N-2 being mixed with HFO-1336mzz(E). The negative dc breakdown voltage of 0.7 MPa HFO-1336mzz(E)/CO2 occupies 99.17%, 93.03%, and 85.92% of that of 0.7 MPa 20%SF6/80%N(2 )mixture under -5 degrees C, -15 degrees C, and -25 degrees C limiting temperatures, guaranteeing its application as an insulation medium in electrical equipment under 220 kV.