Correlation analysis between formation process of SF6 decomposed components and partial discharge qualities

To obtain relationship between concentration of SF₆ decomposed characteristic components (or their concentration ratio) during the formation process and partial discharge qualities and pulse repetition rate, this paper used needle-plate electrode to simulate outthrust insulation fault and conducted a serial of experiments. First, the SF₆ decomposition characteristic under different PD strengths is obtained. Then this paper defines average discharge qualities per second as Q_SEC. It considers both apparent discharge qualities and discharge pulse repetition rate, and analyzes the relation feature between SF₆ decomposition characteristic (both concentration of component and their effective formation rates RRMS) and Q_SEC. Besides, it proposes C(SO₂F₂)/C(SOF₂) as the energy characteristic ratio (ER) to represent PD energy, and defines the effective energy characteristic ratio as (ER_RMS). Moreover, it achieves the inner correlation feature between Q_SEC and all the characteristic component concentration, the RRMS of each characteristic component and ERRMS. The results show that: since number of C atoms from stainless steel surface and content of trace H₂O and O₂ in gas chamber were limited, both decomposed component concentration and component concentration ratio accords with the famous "Logistic Population Model" growth trend in ecology, which means they present "S"-curve increase with Q_SEC. The proposed ER can effectively indicate the amount of PD energy and the defined ER_RMS can objectively reveal the variance regularity of PD energy with Q_SEC. Hence, the correlation mathematic formula between ER_RMS and Q_SEC is obtained and ER_RMS can be used as the new characteristic parameter to represent PD energy. It establishes the foundation for the further fault diagnosis research.