A thermal corrosion evaluation method for polytetrafluoroethylene in SF6 atmosphere
Through the combined use of integrated thermal analysis system and gas chromatography technology, the thermal corrosion reaction of PTFE materials under SF6 atmosphere was studied, which solved the problem that the existing technology was difficult to accurately diagnose, and realized the detailed analysis of thermal corrosion reactions and trace gas products, providing a new method for circuit breaker fault detection and material selection optimization.
Patent Information
- Application Number
- CN202111015044.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-08-31
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2041-08-31
AI Technical Summary
The prior art is difficult to accurately study and diagnose the thermal corrosion reaction of PTFE materials in the GIS circuit breaker in SF6 atmosphere and its impact on SF6 trace gas products, resulting in the inability to effectively deal with latent faults.
The combined use of integrated thermal analysis system and gas chromatography technology is used to simulate the thermal corrosion reaction of PTFE materials under different conditions, measure mass, energy and kinetic information, and detect the types and content of trace gas products through gas chromatography.
The thermal corrosion reaction of SF6 on PTFE materials was successfully studied, revealing the impact of the heating rate on the thermal corrosion process, and providing new research ideas and methods for circuit breaker fault detection and PTFE material selection optimization.
Smart Images
Figure CN113588538B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of data power engineering, and relates to a method for evaluating thermal corrosion of polytetrafluoroethylene in an SF6 atmosphere, and specifically to thermal corrosion behavior and trace gas products of polytetrafluoroethylene materials at air chamber nozzles in circuit breaker equipment in an SF6 atmosphere. Background Art
[0002] Polytetrafluoroethylene (PTFE) material has excellent chemical inertness and resistance to electrothermal corrosion, and is widely used as an organic insulating material for high-voltage GIS circuit breakers. During the circuit breaker opening process, the ablation of PTFE mainly occurs at the nozzle of the gas chamber. During the arc extinguishing process of SF6, the high-speed airflow erodes the PTFE surface produced after the high-energy arc radiation, causing the loss of nozzle insulation material. According to the SF6 plasma decomposition reaction model, SF6, SF5, SF4, SF3, SF2, SF4, CF3, CF2, and CF fragments are generated in the SF6-PTFE plasma, and the fragment ions and F, S, and C atoms are rebonded to form CF4, C2F4, C2F6, C3F8 and other gas characteristic decomposition products. These characteristic decomposition products contain the corrosion information of the gas chamber body material, but their formation mechanism is not clear and cannot be accurately matched to the latent fault.
[0003] In fact, after the GIS circuit breaker is opened and the arc is extinguished, the SF6 molecules that absorb the arc energy may undergo a thermal corrosion reaction with the nozzle insulation material, and the characteristic products such as CF4, C2F4, C2F6, and C3F8 may come from the thermal corrosion reaction. So far, there are few reports on the thermal corrosion reaction of SF6 on PTFE materials and its influence on the formation of trace characteristic gas products of SF6. Therefore, studying the thermal corrosion reaction of the PTFE body material in the gas chamber of the GIS circuit breaker in the SF6 atmosphere provides a new method to clarify the formation mechanism of the characteristic gas decomposition products. Summary of the invention
[0004] The invention provides a method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere.
[0005] In view of the above purpose, the technical scheme adopted by the present invention is: weighing polytetrafluoroethylene material into a crucible, and placing the crucible on a sample tray in a furnace of a comprehensive thermal analyzer; introducing SF6 gas into the furnace, and after the furnace is filled with SF6 gas, starting program-controlled temperature increase and continuously introducing SF6 gas; collecting mass, energy, and kinetic information of SF6 thermal corrosion of polytetrafluoroethylene through a comprehensive thermal analysis system; the gas in the furnace is discharged through a pipeline, cooled by a gas cooling tube, and then introduced into a gas chromatograph, and the type and content of trace gas products generated by SF6 gas thermal corrosion of polytetrafluoroethylene are detected by gas chromatography as a function of temperature and time.
[0006] The measurement temperature range of the above-mentioned comprehensive thermal analysis system is 25°C to 1550°C, the temperature accuracy is ±0.1°C, and the heating rate is 0.1-100°C / min.
[0007] The measurement range in the above comprehensive thermal analysis system is 1 to 300 mg.
[0008] The gas control system in the above-mentioned comprehensive thermal analysis system adopts a mass flow controller.
[0009] The crucible is any one of an aluminum crucible, a graphite crucible, a quartz crucible, a platinum crucible, a copper crucible, and a ceramic crucible.
[0010] The gas cooling pipe is a metal pipe.
[0011] The above gas chromatography detected that the trace gas products produced by SF6 gas thermal corrosion of polytetrafluoroethylene include SO2, H2S, CO, H2, O2, N2, CO2, CH4, CF4, C2F6, C3F8, cyclo-C4F8, C4F 10 , SOF2, SO2F2, COS, CS2 gases. The detection system of the gas chromatograph includes a first pulse discharge helium ion detector channel and a second pulse discharge helium ion detector channel; the first helium ion detector channel is used to detect trace gas products H2, O2, N2, CO, CO2, C2F6, CH4, and the second helium ion detector channel is used to detect trace gas products SO2, CF4, C3F8, CS2, COS, H2S, SOF2, cyclo-C4F8, C4F 10 .
[0012] The present invention adopts a comprehensive thermal analysis system-gas chromatography technology to determine the thermal corrosion reaction process of PTFE in SF6 atmosphere, systematically studies the thermal corrosion reaction of SF6 to PTFE, focuses on the influence of the heating rate on the thermal corrosion process, and analyzes the reaction enthalpy change and reaction type of SF6-PTFE in low-speed and high-speed heating thermal reactions; uses a synchronous comprehensive thermal analysis system and gas chromatography to detect the gas decomposition products of the thermochemical reaction, and qualitatively and quantitatively analyzes the generation rules of the characteristic decomposition products. Compared with the closest prior art, the present invention has the following beneficial effects:
[0013] 1. The present invention uses a comprehensive thermal analysis system to simulate the thermal corrosion reaction process of PTFE materials in SF6 under different conditions, and collects the mass, energy, and kinetic information of SF6 thermal corrosion of polytetrafluoroethylene; gas chromatography technology is used to determine the gas products of the thermal corrosion reaction of PTFE materials in SF6 under different conditions, and the generation relationship between the thermal corrosion reaction of PTFE materials and the trace products of SF6 gas is determined, providing new evidence for the source of the trace products of SF6 gas.
[0014] 2. The present invention provides further research ideas and methods for SF6-PTFE fault detection of circuit breakers, provides experimental basis for diagnosing the source of gas products and nozzle material fault analysis of circuit breakers, and provides new ideas for the selection and optimization of PTFE materials in GIS circuit breakers. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 This is a diagram of a device for measuring characteristic products of thermal corrosion of SF6-PTFE according to the present invention.
[0016] Figure 2 It is the change curve of mass (TG, DTG) and energy (DSC) of thermal corrosion reaction of SF6-PTFE when the temperature rises at 5℃ / min.
[0017] Figure 3 It is the change curve of mass (TG, DTG) and energy (DSC) of thermal corrosion reaction of SF6-PTFE when the temperature rises by 10℃ / min.
[0018] Figure 4 It is the change curve of mass (TG, DTG) and energy (DSC) of thermal corrosion reaction of SF6-PTFE when the temperature rises at 15℃ / min.
[0019] Figure 5 It is the change curve of mass (TG, DTG) and energy (DSC) of thermal corrosion reaction of SF6-PTFE when the temperature rises at 20℃ / min.
[0020] Figure 6 It is the change curve of mass (TG, DTG) and energy (DSC) of thermal corrosion reaction of SF6-PTFE when the temperature rises at 25℃ / min.
[0021] Figure 7 It is the change curve of the mass (TG, DTG) and energy (DSC) of the thermal corrosion reaction of SF6-PTFE when the temperature rises at 30℃ / min. DETAILED DESCRIPTION
[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.
[0023] Example 1
[0024] like Figure 1As shown, the device used in the thermal corrosion evaluation method of polytetrafluoroethylene under SF6 atmosphere provided in this embodiment includes a comprehensive thermal analyzer, a gas cooling tube, and a gas chromatograph. Among them, the comprehensive thermal analyzer is used to determine the state of the thermal corrosion decomposition process of PTFE materials under SF6 atmosphere; the gas cooling tube is used to reduce the temperature of the gas decomposition products after SF6 corrodes the PTFE material in the comprehensive thermal analyzer to protect the subsequent equipment; the detection system of the gas chromatograph includes a first pulse discharge helium ion detector channel and a second pulse discharge helium ion detector channel, and the gas chromatograph is combined with two different pulse discharge helium ion detectors to determine the trace gas decomposition products from the comprehensive thermal analyzer. Among them, the first helium ion detector channel is used to detect the trace gas products H2, O2, N2, CO, CO2, C2F6, CH4 produced by the thermal corrosion of polytetrafluoroethylene by SF6 gas, and the second helium ion detector channel is used to detect the trace gas products SO2, CF4, C3F8, CS2, COS, H2S, SOF2, cyclo-C4F8, C4F 10 .
[0025] Specifically, the method for determining trace gas decomposition products by thermal corrosion of SF6-PTFE is as follows:
[0026] Weigh 5 mg of the PTFE sample to be tested into a ceramic crucible, and place the ceramic crucible on the sample tray in the furnace of the comprehensive thermal analyzer; introduce high-purity (99.999%) SF6 gas into the furnace at a flow rate of 50 mL / min. After the furnace is filled with SF6 gas, start program-controlled heating and continue to introduce SF6 gas. The heating rates β are controlled to be 5, 10, 15, 20, 25, and 30°C / min, respectively. The measuring temperature range is 25 to 800°C. Six groups of experiments are carried out. The mass, energy, and kinetic information of SF6 thermal corrosion of polytetrafluoroethylene are collected by the comprehensive thermal analysis system, and the TG-DTG-DSC curve is obtained, as shown in FIG. Figures 2 to 7 . The SF6 trace gas decomposition products generated by thermal corrosion in the furnace of the comprehensive thermal analyzer are discharged through the pipeline, cooled to room temperature by the gas cooling tube, and then introduced into the gas chromatograph. The gas chromatography is used to detect online the types and contents of the trace gas products generated by the thermal corrosion of PTFE by SF6 gas as the temperature and time change. Considering that the temperature factor directly affects the decomposition reaction process of SF6-PTFE, we determined the component composition of the SF6 trace gas products at different heating rates and decomposition temperatures. Table 1 lists the types and contents of the trace gas products of the SF6-PTFE thermal corrosion reaction at heating rates of 10℃ / min and 30℃ / min and test temperatures of 470℃, 526℃, 543℃, 588℃, and 572℃.
[0027] Table 1 Types and contents of trace gas products produced by SF6 gas thermal corrosion of PTFE (ppm)
[0028]
[0029] Depend on Figures 2 to 7 It can be seen that as the heating rate gradually increases, the starting temperature of SF6 thermal corrosion of PTFE increases, but the temperature is below 500℃; the weight loss curves at 5 and 10℃ / min show the same law, and another same law at other heating rates. The heating rate has an effect on the SF6-PTFE process, showing two different reaction processes; the DSC curves at 5 and 10℃ / min show that the weight loss process is an exothermic reaction, and the other heating rates show an endothermic effect. Increasing the heating rate will accelerate the thermal cracking process of PTFE, while the fluorination decomposition process is inhibited. Online chromatographic analysis found that the main decomposition products of SF6-PTFE are perfluorocarbon small molecules tetrafluoromethane (CF4), hexafluoroethane (C2F6) and octafluoropropane (C3F8). Under the heating condition of 10℃ / min, SF6-PTFE decomposes to generate a large amount of C2F6 and C3F8; while at a heating rate of 30℃ / min, the decomposition products of C2F6 and C3F8 are significantly reduced. As can be seen from Table 1, the thermal corrosion of SF6 on PTFE materials is a source of C2F6 and C3F8 in the trace products of SF6 gas. The results of the changes in trace gas components in Table 1 are consistent with the results of TG / DSC analysis, indicating that the heating rate controls the decomposition reaction process. During the slow heating process, high-temperature activation of SF6 can selectively segment the carbon chain of PTFE, and the thermal decomposition process is mainly fluorination decomposition reaction; while rapid heating will cause the PTFE carbon-carbon chain to crack, and the thermal decomposition process is mainly cracking reaction. It is worth noting that no large amount of CF4 was found to be formed during the entire decomposition process, which also means that the CF4 that appeared in the circuit breaker fault detection is likely to be mainly formed by the plasma decomposition reaction of SF6-PTFE. In addition, oxygen-containing substances such as CO2 and CO were also detected, which should be obtained by the oxidation reaction of the carbon chain cracking products of PTFE.
Claims
1. A method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere, characterized in that: Weigh polytetrafluoroethylene material in a crucible, and place the crucible on a sample tray in the furnace of a comprehensive thermal analyzer; introduce SF6 gas into the furnace, and after the furnace is filled with SF6 gas, start program-controlled heating and continue to introduce SF6 gas, and control the heating rate β to 5, 10, 15, 20, 25, and 30°C / min, respectively. The measurement temperature range is 25 to 800°C, and 6 groups of experiments are carried out. The mass, energy, and kinetic information of SF6 thermal corrosion of polytetrafluoroethylene are collected through a comprehensive thermal analysis system to obtain a TG-DTG-DSC curve; the gas in the furnace is discharged through a pipeline, cooled by a gas cooling tube, and then introduced into a gas chromatograph, and the types and contents of trace gas products produced by SF6 gas thermal corrosion of polytetrafluoroethylene are detected by gas chromatography with changes in temperature and time; The detection system of the gas chromatograph includes a first pulse discharge helium ion detector channel and a second pulse discharge helium ion detector channel; the first helium ion detector channel is used to detect trace gas products H2, O2, N2, CO, CO2, C2F6, and CH4 produced by thermal corrosion of polytetrafluoroethylene by SF6 gas, and the second helium ion detector channel is used to detect trace gas products SO2, CF4, C3F8, CS2, COS, H2S, SOF2, cyclo-C4F8, and C4F produced by thermal corrosion of polytetrafluoroethylene by SF6 gas. 10 ; As the heating rate gradually increases, the starting temperature of SF6 thermal corrosion of PTFE increases, but the temperature is below 500℃; the DSC curves at 5 and 10℃ / min show that the weight loss process is an exothermic reaction, and the other heating rates show an endothermic effect. Increasing the heating rate will accelerate the thermal cracking process of PTFE, while the fluorination decomposition process is inhibited; online chromatographic analysis shows that the main decomposition products of SF6-PTFE are perfluorocarbon small molecules tetrafluoromethane CF4, hexafluoroethane C2F6 and octafluoropropane C3F8; under the heating condition of 10℃ / min, SF6-PTFE decomposes to produce a large amount of C2F6 and C3F8; while at a heating rate of 30℃ / min, the decomposition products of C2F6 and C3F8 are significantly reduced; During the slow heating process, high-temperature activation of SF6 can selectively cut the carbon chain of PTFE, and the thermal decomposition process is mainly fluorination decomposition reaction; while rapid heating will cause the cracking of PTFE carbon-carbon chain, and the thermal decomposition process is mainly cracking reaction; no large amount of CF4 was found to be formed in the entire decomposition process, which also means that the CF4 that appeared in the circuit breaker fault detection is likely to be mainly formed by the plasma decomposition reaction of SF6-PTFE; in addition, CO2 and CO oxygen-containing substances were also detected, which should be obtained by the oxidation reaction of the carbon chain cracking products of PTFE.
2. The method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere according to claim 1, characterized in that: The measuring range of the comprehensive thermal analysis system is 1 to 300 mg.
3. The method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere according to claim 1, characterized in that: The gas control system in the comprehensive thermal analysis system adopts a mass flow controller.
4. The method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere according to claim 1, characterized in that: The crucible is any one of an aluminum crucible, a graphite crucible, a quartz crucible, a platinum crucible, a copper crucible, and a ceramic crucible.
5. The method for evaluating thermal corrosion of polytetrafluoroethylene in SF6 atmosphere according to claim 1, characterized in that: The gas cooling pipe is a metal pipe.