Adsorption Influence Of Adsorbent On SF₆ Decomposition Characteristics Under Partial Overthermal Fault

SF₆ gas-insulated equipment have been considered as low failure rate high voltage electrical equipment. However, contact resistance is often too large due to reasons such as poor contact of the connectors, which could cause partial overheating fault combined with the large current flow. Numerous studies have shown that: when the local abnormal temperature reaches a certain temperature, SF₆ as the main insulation medium inside the equipment would decompose to generate the corrosive poisonous gas such as SO₂, SOF₂ and SO₂F₂. Therefore, our research group proposed the method of using SF₆ thermal decomposition characteristics to monitor partial overheating fault. Different kinds and quantity of adsorbent have been placed in the equipment during installation or maintenance. Adsorbent influences the production process of SF₆ decompositions because of its adsorption of trace water, as well as adsorbs SF₆ decomposition products to varying degrees, making it more complex when using SF₆ decomposition products as characteristic quantities to diagnose inner insulation fault of gas insulated equipment.Therefore, a series SF₆ thermal decomposition experiments with five different adsorbent amounts such as 10%, 5%, 3%, 2%, 0% at the partial overheating temperature of 400? were carried out on the SF₆ thermal decomposition platform to research the adsorption regularity of SF₆ decomposition characteristics components. The formation rules of SF₆ decomposition components were achieved. Besides, the chemical speciation of the elements in the metallic material and adsorbent were obtained using x-ray photoelectron spectroscopy analysis, Fourier transform infrared spectroscopy analysis and Raman spectroscopy analysis. The corrosion mechanism of SF₆ decomposition components on the metallic material and the adsorption mechanism of adsorbent on SF₆ decomposition components under partial overheating fault were preliminarily discussed.Results show that: SF₆ thermal decomposition components including SO₂, SOF₂, CO₂, SO₂F₂ and CS₂ can be detected when adsorbent exists. Due to the different adsorption mechanism of SF₆ decomposition components, the concentrations of these components show different change trends with the adsorbent amounts increasing. The effective gas formation rates of these components show slightly different change trends with the adsorbent amounts increasing, but all the effective gas formation rates decreases with the adsorbent amounts increasing, which have good correlation with the adsorbent amounts. The adsorbent amounts have a significant effect on c?SO₂F₂?/Log10c?SOF₂+SO₂? and c?SO₂+SOF₂+SO₂F₂+CS₂?/c?CO₂+CS₂?, and the influence has obvious regularity. The metallic material would be corroded by SF₆ decomposition components generating FeF3 and some iron sulfur compounds under partial overheating fault. SO₂, CO₂, SO₂F₂, H2 O were detected in the adsorbent after experiment but no SOF₂, justifying that the adsorption of SO₂, CO₂, SO₂F₂, H2 O is physical adsorption and the adsorption of SOF₂ is both chemical adsorption and physical adsorption.