Study on the influence mechanism of trace H2O on SF6 thermal decomposition characteristic components

To explore the influence mechanism of trace H₂O on SF₆ decomposition characteristics under partial thermal fault and establish the foundation of using SF₆ thermal decomposition principle to diagnose the thermal fault of SF₆ electrical equipment, a series of artificial thermal fault decomposition experiments with different H₂O concentrations were conducted on the designed SF₆ thermal decomposition experimental system. A trace water injector was used to control the content of trace H₂O accurately and gas chromatograph, chromatography-mass spectrometry as well as Fourier transform infrared spectroscopy were used to measure decomposed components. Finally, the thermal decomposition characteristic under 340°C was achieved. The analysis results indicate no matter how much H₂O content is, SF₆ can decomposes into many kinds of decomposition characteristics, such as CO₂, SOF₂, SO₂, SOF₄, SO₂F₂, H₂S, HF. The concentrations of all these decomposition characteristics increase with the time extended, but change differently with the increase of H₂O content, because H₂O plays different role in the formation process of each decomposition characteristic components. The variation of H₂O content not only affects the production of the decomposition characteristic components, but also makes SO₂ and HF gradually evolved into the main characteristic components of SF₆ thermal decomposition. In addition, the higher the H₂O content is, the stronger the promoting effect on SO₂ and HF is.