SF6 Gas Decomposition Research Articles

Application of sulfur hexafluoride in electrical engineering. Historical past, current state and prospects in future

A pressing issue today is the analysis of the possibilities of using SF6 gas and its possible limitations of use from the point of view of harmful effects on the environment. The article, based on free sources of information, systematizes the historical facts of the development of SF6 gas, the main stages of the formation of the SF6 gas environment as insulation for electrical equipment. Comparative characteristics of electrical strength for various insulating substances are presented. Research has been carried out on modern examples of the use of SF6 gas in medium and high voltage circuit breakers. Examples of the use of SF6 gas and its mixtures as gas insulation for high-voltage power lines are analyzed. It is shown that a promising direction for the development of SF6 gas is its use in gas-insulated power lines. Design features and examples of practical application of high-voltage gas-insulated power lines are presented. The features of using SF6 insulation in electrical equipment of different voltage classes are determined. Current environmental problems associated with the use of SF6 gas are analyzed and possible directions for overcoming them are established. The elements of SF6 gas decomposition products that are toxic and pose the greatest danger are considered. The characteristics of SF6 gas as a greenhouse gas are given and promising ways to reduce its use are shown. It has been established that by using not pure SF6 gas, but gas mixtures based on it, it is possible to significantly reduce the percentage of SF6 gas use. Promising directions for further development of gas insulating medium for electrical equipment without the use of SF6 gas have been established.

Monitoring and Leak Diagnostics of Sulfur Hexafluoride and Decomposition Gases from Power Equipment for the Reliability and Safety of Power Grid Operation

Sulfur hexafluoride (SF6) is a typical fluorine gas with excellent insulation and arc extinguishing properties that has been widely used in large-scale power equipment. The detection of SF6 gas in high-power electrical equipment is a necessary measure to ensure the reliability and safety of power grid operation. A failure of SF6 insulated electrical equipment, such as discharging or overheating conditions, can cause SF6 gas decomposition, resulting in various decomposition products. The decomposed gases inside the equipment decrease the insulating properties and are toxic. The leakage of SF6 can also decrease the insulating properties. Therefore, it is crucial to monitor the leakage of SF6 decomposed gases from electrical equipment. Quantitative testing of decomposition products allows us to assess the insulation state of the equipment, identify internal faults, and maintain the equipment. This review comprehensively introduces the decomposition formation mechanism of SF6 gas and the current detection technology of decomposition products from the aspects of principle and structure, materials, test effect, and practicability. Finally, the development trends of SF6 and decomposition gas detection technology for the reliability and safety of power grid operation are prospected.

Trace detection of SF6 gas decomposition component H2S based on Pr6O11-In2O3

Sulfur hexafluoride (SF6) from Gas Insulated Switchgear (GIS) will decompose and produce hydrogen sulfide (H2S) in the event of equipment failure. Therefore, the detection of H2S can determine whether the equipment has malfunctioned. Due to the low concentration of the SF6 decomposition product H2S and its application in industrial environments, sensors must have a low detection limit and rapid response time. Considering that the oxides of rare earth elements can improve the sensing characteristics, praseodymium oxide (Pr6O11)-indium oxide (In2O3) was prepared. The impact of Pr6O11 doping on In2O3 was investigated through characterization methods. To validate its feasibility for use in GIS, the best sensor (F3) exhibits good sensing characteristics for H2S in the SF6 and air ambient. The responses to 10 parts per million (ppm) H2S at 190°C were 146.6 in SF6 and 190.8 in air. In SF6 ambient, the F3 sensor demonstrated a low detection limit (50 parts per billion (ppb)). The good sensing characteristics are attributed to the doping of rare earth elements, which induces an increase in the proportion of defect oxygen and accelerate the chemical reaction. The sensing characteristics of the material can be attributed to the doping of Pr6O11 and the electronic effect. This study provides a novel approach for detecting H2S generated from SF6 decomposition.

Research on Joint Sensing Technology for Vibration and Dielectric Spectrum of Power Equipment in the Context of New Power Systems

Abstract This paper has carried out the test results of SF6 gas decomposition products and the dielectric spectrum detection, proposed method for the identifying equipment defects based on decomposition products, and the partial discharge detection and diagnosis method for the equipment discharge defects. Combining the above two methods, the GIS discharge defects are comprehensively evaluated by decomposition products and partial discharge detection, achieving the type prediction of latent faults in operating switch-gear. In the aspect of vibration signal analysis, this paper conducts the wavelet analysis of the vibration signals and obtains frequency spectrum results under multi-layer wavelet decomposition. In the aspect of dielectric spectrum analysis, a model of three HN function superposition was used to fit the experimental data to verify the validity of the model, and the characteristic parameters such as the DC conductivity were extracted. It was found their dependence on temperature basically conformed to the Arrhenius formula. On this basis, the thermal aging test platform for the epoxy resin samples was established, and an accelerated thermal aging experiment was conducted at the temperature of 115 °C. The dielectric response test system was used to measure dielectric spectra of the samples with different aging times, compare the dielectric spectra at different aging times, and analyze the reasons for the differences.

Adsorption of SF6 decomposition gases (H2S, SO2 and SOF2) on TM (Pd and Pt) modified monolayer ZrS2: A DFT study

Fast and effective detection of SF6 gas decomposition products is essential. In this study, the adsorption behaviors of H2S, SO2 and SOF2 on Pd-ZrS2 and Pt-ZrS2 monolayers were analyzed using density-functional theory (DFT), and the electronic properties of the different adsorption systems and their sensing properties were discussed in depth. The results show that the Pd and Pt modifications significantly improve the surface activity of the intrinsic ZrS2 monolayers, giving them better adsorption and sensing properties. The reasonable adsorption energies and significant sensitivity differences suggest that the Pd(Pt)-ZrS2 monolayers may be potential candidates for H2S, SO2 and SOF2 sensors. This study provides theoretical guidance for the prospective application of Pd(Pt)-ZrS2 in the operational condition assessment of GIS equipment.

Mid-infrared photoacoustic spectrum analysis of SF6 gas-decomposition system

Mid-infrared photoacoustic spectrum analysis of SF6 gas-decomposition system

A Case Analysis of Particle Defects Found in 220kV GIS by Ultrasonic Partial Discharge and SF6 Gas Decomposition Products Joint Detection

The particles inside GIS have become the biggest factor affecting the safe and stable operation of GIS. How to effectively and timely find the particle defects is very important to ensure the reliable operation of GIS. This article describes in detail how to find particles in GIS through ultrasonic partial discharge method and comprehensive diagnosis of SF6 gas decomposition products, and gives specific solutions, which will provide very useful experience for subsequent GIS operation and maintenance.

Detection of SF6 gas decomposition component H2S based on fiber-optic photoacoustic sensing

A high-sensitivity fiber-optic Fabry-Perot (F-P) photoacoustic gas detection system with properties of anti-electromagnetic interference and intrinsically safe was presented for quantitative analysis of SF6 decomposition component H2S. Erbium-doped fiber amplification was combined with acoustic resonance amplification to enhance the photoacoustic signal. A fiber-optic cantilever acoustic sensor (FOCAS) was used to sense weak photoacoustic signals. To enhance the sensitivity and stability of photoacoustic signals detection, the effect of SF6 gas on the responses of FOCAS and photoacoustic cell (PAC) was investigated. When SF6 is the background gas, the resonance frequency of the PAC will be greatly reduced and the sensitivity of the FOCAS will be improved. With the excitation light power of 1 W and an averaging time was 200 s, the minimum detection limit (MDL) of H2S gas in the SF6 background reached 14 ppb, and the normalized noise equivalence absorption (NNEA) was calculated to be 3.14 × 10−9 cm−1·W·Hz−1/2. The combination of excitation enhancement and detection enhancement of the photoacoustic signal solves the problem that the traditional sensor is difficult to improve the detection sensitivity due to the low absorption coefficient of H2S gas in the near-infrared region.

A Numerical Study on the Decomposition and Diffusion Characteristics of SF6 in Gas-Insulated Switchgear with Consideration of the Temperature Rising Effect

The optimized concentration of SF6 gas is the key to maintaining a good insulation performance by GIS equipment. The precise measurements of the SF6 concentration and decomposition byproducts could be used to indicate the remaining GIS insulation level during long-term operations. In this paper, a finite-element simulation model was created to investigate the SF6 gas decomposition and diffusion dynamics. A theoretical analysis and simulation of the overheating fault, i.e., the contact between the GIS disconnect switches, were carried out, followed by an estimation of the SF6 decomposition and diffusion characteristics caused by the local heating faults, based on the calculated flow velocity field and temperature field.

Analysis of Suspended Potential Discharge Defects by SF6 Decomposition Products

The type and content of SF6 decomposition products are directly related to the type, location and degree of fault. Based on the analysis of the abnormal SF6 gas decomposition product content and discharge type of 126kV Porcelain Column type circuit breaker, the potential fault of the circuit breaker is judged to be suspension potential discharge fault. After disassembling the circuit breaker, it is found that the abnormal phase of the insulation rod is deformed, the pin become thin, and there are solid decomposition products, the sulfides and fluoride, which are mainly composed of iron, aluminum, chromium and manganese, further confirm that the potential fault of the circuit breaker is suspension potential discharge fault. The forming process and reaction mechanism of the suspended potential discharge fault are analyzed. Once the fault occurs, its function will promote the development of the fault. The influence of the suspension potential discharge fault on the performance of the circuit breaker is also analyzed. When the suspension potential discharge fault exists, it will cause the abnormality and even affect the normal operation of the circuit breake.

Dielectric and Design and Experimental Study of GIS Gas Chamber HF and Micro Water Dual Fiber Laser Detection System

HF gas and trace moisture content, as the primary characteristic by-products of SF6 gas decomposition reaction, are of great significance to the fault diagnosis of high voltage SF6 gas insulated high voltage power equipment. In this paper, the typical discharge fault types in GIS are analyzed, and the decomposition products corresponding to different discharge types are summarized. The physical and chemical mechanism of HF generation in the early dissociation process of SF6 and under certain micro water and micro oxygen conditions is explained, and the experimental platform is built to carry out the simulation generation experiment of HF gas and micro water. The results show that choosing the best target absorption line suitable for sensitive and selective gas sensing can eliminate interference, simplify the system and reduce the cost. Furthermore, under the experimental conditions, the self-developed TDLAS online detection technology is used to realize the effective detection of HF gas and trace water in GIS discharge room. The 1278nm and 1392nm laser sources are selected respectively, and the TDLAS technology based on dual fiber time-sharing multiplexing is feasible for HF and trace water measurement. The stability and reliability of the technology are verified, which can provide effective technical support for on-line detection of HF gas in GIS, and has good engineering application value.

Gas-sensing properties of Ptn-doped WSe2 to SF6 decomposition products

Two-dimensional transition metal disulfides (TMDs) has attracted considerable attention due to its excellent physicochemical properties. In order to detect the SF6 decomposition products, transition metal Pt cluster doping was chosen to enhance the adsorption property of intrinsic WSe2 monolayer. The adsorption of SO2, SOF2 and SO2F2 on Ptn (n=1–3) doped WSe2 monolayer is studied based on the first-principle calculation. The adsorption energy, charge transfer, and density of states of the interaction between the target gas molecules and Ptn-WSe2 were studied. The calculation results showed that Pt3 doping dramatically enhances the adsorption of WSe2 to SO2 and SOF2 and SO2F2 molecules. Meanwhile, electrons transfer from Ptn-WSe2 surface to these three kinds of target gas molecules, reducing the conductivity of the adsorption system in different degrees. The results of this study not only have important significance for explaining the sensing mechanism of Ptn-WSe2 adsorption to SF6 gas decomposition products, but also provide a potential material for further development of gas sensing sensors.

Study on Determination of SF6 Decomposition Based on Gas Chromatography

The current research about SF6 switchgear failures mainly focuses on various troubleshooting methods, while ignoring the impact of SF6 gas decomposition products on equipment and the types of failures they reflect, and the application of SF6 gas decomposition products to diagnose equipment failures still needs to be further explored and improved. Therefore, this paper focuses on the study of the decomposition process of SF6 under partial discharge failure, and conducts theoretical analysis of the decomposition product composition of SF6 under partial discharge failure, and detects SF6 gas decomposition products by gas chromatography. Finally, it can be concluded that when the concentration of S2F10 and S2OF10 is about 5μL/L, the switchgear is likely to have a partial discharge failure. At this time, the maintenance personnel should deal with it in time to ensure that the switchgear can be put into use normally.

A new detection device for decomposition products of insulating gas in electrical equipment

In this paper, a multi-functional SF6 gas decomposition products comprehensive analysis device is realized by using spectral absorption technology, integrating the existing electrochemical sensor technology, and integrating a variety of detection modules. In this paper, a set of hardware system is researched and implemented, which takes microprocessor as the control core and touch LCD as the human-machine interface to realize the SF6 Electrical Equipment multi-functional gas analysis equipment.

Study on the Correlation between Partial Discharge Energy and SF6 Decomposition Gas Generation

In this paper, the amount of SF6 decomposition gases due to the partial discharge (PD) was studied in the SF6 gas-insulated transformer. The long-term PD degradation experiment was performed while controlling the discharge magnitude using the surface discharge, and the gas generation amount was measured by using gas chromatography for SO2F2, SOF2, SO2, CO, and CF4. In addition, to investigate the relationship between the partial discharge energy and the decomposed gas generation amount, partial discharge energy was calculated by a data processing program and converted to the unit of joule per mole. With the finite element method (FEM), the electric field distribution and SF6 gas decomposition mechanism were explained for the partial discharge energy effect on the gas generation. This study helps understand the relationship between the partial discharge energy and the decomposed gas generation ratio with the experimental results and can be used for the diagnosis of PD and maintenance process for the gas-insulated transformers.

Design and Development of 220kV SF6 Gas Insulated GIS Actual Testing Platform

To simulate the performance parameters of SF6 gas insulated AC GIS equipment under normal and failure condition in the laboratory environment, and the development trend of characteristic parameters such as partial discharge and SF6 gas decomposition can be monitored periodically and quantitatively, the 220kV SF6 gas insulated GIS type test platform is designed and developed. The test platform is in accordance with GIS specifications used in substation, including gas insulated circuit breaker and other typical GIS equipment. The external voltage is realized by the series resonant circuit. The paper starts from the design of the GIS bus and the solid insulation structure, and the three-dimensional E-field distribution characteristics of the solid insulator are simulated and analyzed. The hardware installation of the partial discharge measurement and SF6 gas decomposition monitoring on GIS model test platform are discussed. Through design and development of 220kV SF6 gas insulated GIS type-test platform, the feasibility of the structure design of GIS bus and the solid insulation are verified, it provides theoretical and practical basis for the operation and maintenance of SF6 gas insulated GIS equipment.

Research and Development of NDIR Sensor and Its Application In On-Line Detection of CF4 Gas

Due to the excellent insulation and arc extinguishing properties of SF6 gas, it is widely used in the production and use of high voltage GIS. However, due to the breakdown of discharge and overheat, SF6 gas decomposes and produces a variety of low fluorine sulfides. Therefore, the concentration of CF4 gas in the high-voltage switch state can be effectively determined by detecting high-voltage GIS. This paper puts forward a kind of semiconductor laser based gas detection (NDIR) technology, the flange fixed installation in high voltage switch, optical fiber sensing structure can realize remote, real-time online monitoring of CF4 gas content. The experiment shows that the flange fiber optic sensor on-line monitoring device can realize the effective measurement of CF4 gas. The research results show that maximum field intensity on the surface of basin insulator is 10.788kV/mm, which is lower than the control field strength of 20kV/mm under the SF6 gas insulation condition, therefore the E-field near the basin insulator does not affect the operation of the optical fiber sensor. In the case of 1m light path, the detection limit of CF4 gas near 1312nm is less than 0.5ppm. The results of this study can provide an entirely new scheme for on-line monitoring of high-pressure open-light SF6 gas decomposition products, which can realize real-time on-line monitoring of the internal gas of the high voltage GIS equipment.

Triangle Fault Diagnosis Method for SF6 Gas-Insulated Equipment

The use of SF6 gas decomposition components for the fault diagnosis of gas-insulated equipment (GIE) has received widespread attention and been extensively adopted by the power industry. However, the present focus is mainly on the use of a component type or absolute content for generating qualitative judgments on the existence of a fault, and the practical diagnosis method for field diagnosis is extremely lacking. In this paper, ten-year fault data were collected and analyzed. Decomposition components were extracted and combined, based on the decomposition characteristics of SF6, and enhancement factors were given to three component characteristic quantities using fuzzy C-means clustering algorithm. The component characteristic quantities that characterized the high-energy discharge fault, partial discharge, and partial over-thermal fault of the device were extracted: % (SOF2+SO2), % (9SO2F2), and % (5CO2). With adoption of these characteristic quantities as the coordinate axes of the triangle coordinate system, a triangle fault diagnosis method for field diagnosis of SF6 GIE was constructed. The diagnosis method was validated by a large number of experimental data and field failure data, and 128 of the 150 experimental samples were correctly recognized. Moreover, the test conditions did not considerably affect the diagnostic results of the method. This technique can provide a simple and effective field diagnostics technology for the power industry.

Electrochemical and Infrared Absorption Spectroscopy Detection of SF₆ Decomposition Products.

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.

The Application of Complex Wavelet Transform to Spectral Signals Background Deduction

The accuracy of spectrograms may be affected by baseline excursion or drift when infrared spectrometers are used in the analyses of gases. Background deduction or baseline correction is one of the effective pretreatment methods that can improve measurement accuracy. This paper presents a novel methodology based on complex wavelet transform algorithm to perform background deduction. The complex wavelet transform methodology establishes a complex wavelet filter to decompose the spectral signals first, and set the decomposition coefficients in the high-frequency section to zero, and then reconstruct the background signals; finally, the background deduction can be realized by deducting the background signals. In this study, the complex wavelet established by Daubechies was selected to demonstrate background deduction aiming at simulative spectral signals with different backgrounds and the real spectral signal of SF6 decomposition gases. Compared with the results done by the real wavelet transform in the same conditions, the results indicate that complex wavelet transform methodology can perform background deduction more efficiently than real wavelet transform methodology, thus improving the effectiveness and precision of spectrogram measurements greatly, which is useful for SF6 gas decomposition compositions analysis