Study on the decomposition mechanism and insulation stability of HFO-1336mzz(E)/air mixtures as a new environment-friendly insulation medium under AC voltage

As one of hydrofluoroolefins (HFOs), HFO-1336mzz(E) is regarded as a promising eco-friendly alternative insulation medium to Sulfur Hexafluoride (SF6) owing to its excellent environmental effect and insulation property. To study the decomposition mechanism and insulation stability, the decomposition experiment of a 0.5 MPa mixture containing 8% HFO-1336mzz(E) and 92% air was performed under AC breakdown conditions. The results indicated that the main decomposition products were CF4, C2F6, C3F8, CF3H, CF3C=CH, CF3CH=CHF(E), CF3CHF2, CF3CH=CH2, CF2=CFH, CF2=CH2, CH=CH, C4H2F6O, CF3O3CF3, etc. Among them, the generation of C3F8, CH=CH, and C4H2F6O was relatively more difficult than others. Thus, these three compounds can be considered typical decomposition products. New elements, namely C, F, and N, appeared on the electrode surface after breakdowns compared to the state before breakdowns. It can be concluded that some complex chemical reactions were triggered between the electrode material and gas mixture under the action of breakdown discharge. Additionally, the breakdown voltage of the HFO-1336mzz(E)/air mixture almost remained unchanged, showing that the gas mixture still exhibited an excellent insulation stability after multiple breakdowns.