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 (N-2 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)/N-2 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 degrees 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.