Effects of Oxygen on the Insulation Characteristics of Eco-Friendly Insulating Gas HFO-1336mzz(E)/CO2

HFO-1336mzz(E)/CO₂, an eco-friendly insulating gas, garnered considerable interest recently as a potential substitute for SF₆ in gas-insulated equipment. To reduce the precipitation of fluorocarbon gases and solids during the decomposition process of HFO-1336mzz(E)/CO₂ gas mixture, O₂ is normally introduced as an additive. Herein, we investigated the influence of oxygen on the insulation performance of HFO-1336mzz(E)/CO₂ under different electric field non-uniformities by evaluating the breakdown voltage, PDIV, PDEV and decomposition characteristics. The findings indicate that in a quasi-uniform electric field, the breakdown voltage of the gas mixture progressively increases with the oxygen volume fraction. Under the extremely non-uniform electric field, both the breakdown voltage and PDIV initially rise and subsequently decline with the increase of oxygen volume fraction, reaching a peak at 6%. The PD decomposition analysis reveals that the addition of 4% oxygen can reduce the decomposition of HFO-1336mzz(E), which is most beneficial to improve the comprehensive insulation performance of the gas mixture.