Electrochemical and Infrared Absorption Spectroscopy Detection of SF6 Decomposition Products

Abstract

Sulfur hexafluoride (SF6) gas-insulated electrical equipment is widely used in high-voltage (HV) and extra-high-voltage (EHV) power systems. Partial discharge (PD) and local heating can occur in the electrical equipment because of insulation faults, which results in SF6 decomposition and ultimately generates several types of decomposition products. These SF6 decomposition products can be qualitatively and quantitatively detected with relevant detection methods, and such detection contributes to diagnosing the internal faults and evaluating the security risks of the equipment. At present, multiple detection methods exist for analyzing the SF6 decomposition products, and electrochemical sensing (ES) and infrared (IR) spectroscopy are well suited for application in online detection. In this study, the combination of ES with IR spectroscopy is used to detect SF6 gas decomposition. First, the characteristics of these two detection methods are studied, and the data analysis matrix is established. Then, a qualitative and quantitative analysis ES-IR model is established by adopting a two-step approach. A SF6 decomposition detector is designed and manufactured by combining an electrochemical sensor and IR spectroscopy technology. The detector is used to detect SF6 gas decomposition and is verified to reliably and accurately detect the gas components and concentrations.

Typical Internal Defects of Gas-Insulated Switchgear and Partial Discharge Characteristics

“…Many studies show that the SF 6 gas will decompose under PD and the decomposed components will further react with moisture and oxygen in the gas chamber of GIS to generate a , and SF 4 . By detecting these decomposed components in the GIS gas chamber, it is possible to determine whether there is a PD source [23,24].…”

Optical properties and decomposition mechanisms of SF6 at different partial discharge determined by infrared spectroscopy

“…4,16 CF 4 has been reported as a characteristic product of discharge involving carbon atoms in steel and epoxy resin composites, and as a typical decomposition product for insulation defect rather than floating potential defect. 15 Therefore, the increase in CF 4 concentration can be attributed to the increase of carbon-related defects. Any obvious deviation from a linear increase in CF 4 concentration over time may indicate a change in the condition of PD in GIS.…”

Highly sensitive photoacoustic multicomponent gas sensor for SF6 decomposition online monitoring

“…However, several lower fluorides of sulphur SF x (x = 1, 2 …5) and F atoms can be generated through a corona (also called partial discharge), electric arc or spark in a gas-insulated electric power system. Although, most of the sub-fluorides will rapidly react with F atoms to regenerate SF 6 molecules again, a small portion of SF x can further react with trace levels of unavoidable impurities (typical gases are H 2 O, O 2 and N 2 ) or electrodes to produce numerous stable by-products [3][4][5]. The gaseous SF 6 decompositions (such as SO 2 and H 2 S) are known to be corrosive, poisonous and chemically active, which can chemically attach the internal surface of solid insulating materials.…”