Surface Flashover Characteristics of Epoxy Resin in HFO-1336mzz(E)/CO2 Gas Mixtures under Negative DC Voltage

Eco-friendly HFO-1336mzz(E) is promising as an insulating gas in medium-voltage equipment. However, the surface flashover characteristics of epoxy resin in HFO-1336mzz(E) /buffer-gas mixtures, significantly influencing the insulation performance and operational safety, have gained little academic attention by far. This article has studied the effects of typical buffer gas (N2 and CO2), pressure, and mixing ratio on the surface flashover characteristics under negative dc voltage. The results show that more solid by-products have been generated after several flashovers in the HFO-1336mzz(E) /N2 gas mixtures, leading to a lower tolerance than HFO-1336mzz(E) /CO2 gas mixtures. The surface flashover voltage of HFO-1336mzz(E) /CO2 gas mixtures increases with gas pressure or mixing ratio, and there is a positive synergistic effect between HFO-1336mzz(E) and CO2. The available concentration of HFO-1336mzz(E) gas in the mixtures depends on the limiting liquefaction temperature and gas pressure. When the liquefaction temperature is limited to −15 °C, the HFO-1336mzz(E)/CO2 gas mixtures with 4%–6% HFO-1336mzz(E) at 0.40 MPa and 6%–10% HFO-1336mzz(E) at 0.30 MPa can be used to replace pure SF6 at 0.13 MPa in medium-voltage equipment. This article can provide an essential reference for its engineering application.