Sulfur hexafluoride and nitrogen mixed gas decomposition product detection system and detection method thereofTechnical Field
The invention belongs to the technical field of high-voltage electrical equipment insulation, and particularly relates to a system and a method for detecting decomposition products of sulfur hexafluoride and nitrogen mixed gas.
Background
China started to process sulfur hexafluoride (SF) in the 70 s of the 20 th century6) When the mixed gas is used as an insulating medium, the mixed gas is considered to replace high-purity SF6the main reason for the gas is SF6The gas has many disadvantages, such as high price, sensitivity to electric field uniformity, easy liquefaction at low temperature, and is not suitable for northern severe cold areas. But SF of the same gas pressure in a uniform field6The dielectric strength of the mixed gas is not high-purity SF6The insulation strength of the gas is high, the field use requirement is not easy to meet, and most of high-voltage insulation equipment in China still adopts high-purity SF6as a gas-insulating medium.
With the development of economy, environmental protection, energy conservation and emission reduction are more and more emphasized in the international society, and under the background, SF (sulfur hexafluoride)6the greenhouse benefit of the gas is gradually being emphasized. Kyoto protocol passed in 1997F is prepared from6Listed as one of 6 greenhouse gases worldwide. Scientists and electric power departments in various countries have developed a great deal of mixed gas research, expecting to use SF6/N2Mixed gas replacing pure SF6gas as insulating gas for switchgear to reduce SF6The amount of SF is reduced from the source6greenhouse effect of emissions.
From the current research and application point of view, SF6/N2the mixed gas has good application prospect. Various experimental researches carried out at the present stage in China show that SF6/N2No new poison is generated in the discharge of the mixed gas, and the sensitivity to the surface defects of the electrode is low; from the application point of view, SF is adopted6/N2The mixed gas is used as an arc extinguishing and insulating medium of a circuit breaker and is already applied to foreign electric companies such as ABB, Siemens and the like.
With SF6/N2The mixed gas gradually replaces SF6Pure gas as insulation gas of switch equipment, SF in mixed gas6Analysis of gas decomposition product concentration, SF6gas purity detection, SF6Studies on problems such as detection of trace amounts of water have been proposed.
Although SF6/N2Physical and chemical properties of mixed gas and high-purity SF6Similarly, there are great differences in the decomposition product gas analysis algorithm if high purity SF is still used6SF under gas6The result of the decomposition product detection equipment and algorithm can cause larger measurement error, and the related national standard measurement requirements cannot be met. If such a device is mounted to the SF6/N2On the high-voltage equipment of mixed gas, the measurement of each parameter of the mixed gas of light persons is inaccurate, the conditions of equipment misoperation, false alarm and the like can be seriously caused, and SF is seriously threatened6Safe operation of the switchgear.
disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a system and a method for detecting decomposition products of sulfur hexafluoride and nitrogen mixed gas, wherein the system can realize SF6/N2The content of the decomposition products of the mixed gas is accurately measured, the monitoring and inspection requirements under similar application environments are met, and the running state of the switch equipment is monitored.
In order to solve the technical problems, the invention adopts the following technical scheme: the sulfur hexafluoride and nitrogen mixed gas decomposition product detection system comprises a main control unit, a display unit, an air inlet pipeline, an air outlet pipeline, a first detection air channel and a second detection air channel, wherein the first detection air channel and the second detection air channel are arranged in parallel;
The main control unit is respectively connected with the display unit, the decomposition product and temperature sensing unit, the purity sensing unit, the flow sensing unit and the pressure sensing unit through cables.
The monitoring method of the sulfur hexafluoride and nitrogen mixed gas decomposition product detection system comprises the following steps:
1) The air inlet pipe joint is connected to high-voltage switch equipment to ensure tight sealing;
2) The decomposition product and temperature sensing unit, the purity sensing unit, the flow sensing unit and the pressure sensing unit respectively obtain the gas temperature, the original signal quantity of the decomposition product, the concentration change of the mixed gas, the flow of the mixed gas and the internal pressure signal quantity of the gas circuit, then the data are uploaded to the main control unit through digital signals or analog signals, and the main control unit calculates SF (sulfur hexafluoride) through a multivariate composite algorithm6/N2The content of each component of the decomposition product in the mixed gas;
3) Then the display unit displays the SF of the mixed gas in real time6Concentration, decomposition product content, temperature value, and storing SF6/N2SF of mixed gas6Purity, content of decomposition products, etc., for future historythe inquiry function is used for rechecking and researching, and simultaneously provides a state prompt function according to the corresponding standard file to remind a user of the current running state of the high-voltage equipment.
The specific calculation process of the multivariate composite algorithm in the step 2) is as follows:
Theoretically pure SF6Gas and pure N2the content of each component of the decomposition product in the gas is calculated by adopting a formula (1),
（1）
Wherein:
Pure SF6Background, response value of purity sensing unit with certain concentration
SF in the gas mixture6Volume content (v/v)%
Pure N2background, response value of purity sensing unit with certain concentration
In the mixed gas N2Volume content (v/v)%
Temperature, flow compensation coefficient, whereinfor distinguishing between different gas types, such as: SO (SO)2、H2S、CO，pas temperature, flow rate parameters
from pure SF6gas and pure N2Starting from the state equation of the gas, the actual gas is carefully analyzedThe difference between the gas and the ideal gas is analyzed according to the Graham's law, the basic diffusion rule of each component of the decomposition product in the mixed gas is analyzed, and the cross-over removal operation and dynamic compensation are carried out through different weight ratios, and finally the content of each component of the decomposition product of the calculated mixed gas is obtained;
According to the Graham's law, N is observed under the same temperature and pressure2The diffusion rate of the gas as the intermediate decomposition product is SF62.28 times of the gas diffusion rate of the medium decomposition product, thereby leading to N under the same conditions2Decomposition product sensor response and SF in (1)6Similar relations also exist among sensor response quantities of medium decomposition products, but the proportional relations of the medium decomposition products are different for different components;
After a large number of high and low temperature experiments and different SF6Gas experiment of decomposition product of specific component, a certain concentration of SF6Gas experiment of decomposition products with different components with the volume content of 30 percent, data integration analysis, comprehensive consideration of all factors and obtaining SF with any proportion according to the formula (1)6/N2The multielement compound formula of the content of the decomposition products in the mixed gas is as follows:
（2）
Wherein:
Compensating the coefficients for the raw sensor signal
Response of different sensors of the decomposition product sensing unit
Compensation coefficient for temperature and flow
Generation, generationTable for different decomposition product gases, for example: SO (SO)2、H2S、CO
pThe parameters are temperature and flow parameters.
By adopting the technical scheme, a set of practical SF is explored through a large number of tests and data statistical calculation6Method for measuring concentration analysis of decomposition products in mixed gas, and SF is developed according to the method6/N2Mixed gas decomposition product detecting system. The invention aims to detect the content of each component of decomposition product gas in mixed gas, and the system purity sensing unit detects SF in the mixed gas6And finally, sending each signal to a main control unit, and obtaining the content of each component of the decomposition product gas in the mixed gas through an embedded algorithm (including de-crossing, flow compensation, temperature compensation and the like). The invention is based on a large amount of experimental data analysis and a specific multivariate composite compensation algorithm from the point of physical significance, and a specific SF is calibrated once6the function of measuring decomposition products under concentration can be used for detecting SF with any proportion6And N2The content of decomposition products in the gas mixture is particularly suitable for SF in a ratio of 3:76/N2Measurement function of the decomposition product of the mixed gas.
drawings
Fig. 1 is a schematic structural view of the present invention.
Detailed Description
As shown in fig. 1, the system for detecting decomposition products of a sulfur hexafluoride and nitrogen mixed gas comprises a main control unit 1, a display unit 2, an air inlet pipeline 3, an air outlet pipeline 4, a first detection air channel 5 and a second detection air channel 6, wherein the first detection air channel 5 and the second detection air channel 6 are arranged in parallel, an air inlet pipe joint 8 with a flow regulating valve 7 is arranged at an air inlet of the air inlet pipeline 3, air inlets of the first detection air channel 5 and the second detection air channel 6 are connected with an air outlet of the air inlet pipeline 3, and air outlets of the first detection air channel 5 and the second detection air channel 6 are connected with an air inlet of the air outlet pipeline 4;
the first detection gas circuit 5 is provided with a decomposition product and temperature sensing unit 9 and a flow sensing unit 10, the second detection gas circuit 6 is provided with a purity sensing unit 11 and a pressure sensing unit 12, and the main control unit 1 is respectively connected with the display unit 2, the decomposition product and temperature sensing unit 9, the purity sensing unit 11, the flow sensing unit 10 and the pressure sensing unit 12 through cables.
The monitoring method of the sulfur hexafluoride and nitrogen mixed gas decomposition product detection system comprises the following steps:
1) The air inlet pipe joint 8 is connected to high-voltage switch equipment to ensure tight sealing;
2) The decomposition product and temperature sensing unit 9, the purity sensing unit 11, the flow sensing unit 10 and the pressure sensing unit 12 respectively obtain the gas temperature, the original semaphore of the decomposition product, the concentration change of the mixed gas, the flow of the mixed gas and the internal pressure semaphore of the gas circuit, then the data are uploaded to the main control unit 1 through digital signals or analog signals, and the main control unit 1 calculates SF through a multi-element composite algorithm6/N2the content of each component of the decomposition product in the mixed gas;
3) Then the display unit 2 displays the SF of the mixed gas in real time6Concentration, decomposition product content, temperature value, and storing SF6/N2SF of mixed gas6The purity, the content of the decomposition products and other parameters are checked and researched through a history inquiry function in the future, and a state prompt function is provided according to a corresponding standard file to remind a user of the current running state of the high-voltage equipment.
The specific calculation process of the multivariate composite algorithm in the step 2) is as follows:
Theoretically pure SF6Gas and pure N2the content of each component of the decomposition product in the gas is calculated by adopting a formula (1),
（1）
Wherein:
Is all ofSF6Background, response value of purity sensing unit with certain concentration
SF in the gas mixture6Volume content (v/v)%
Pure N2Background, response value of purity sensing unit with certain concentration
in the mixed gas N2Volume content (v/v)%
Temperature, flow compensation coefficient, whereinFor distinguishing between different gas types, such as: SO (SO)2、H2S、CO，pAs temperature, flow rate parameters
From pure SF6Gas and pure N2Starting from a state equation of the gas, carefully analyzing the difference between the actual gas and the ideal gas, analyzing the basic diffusion rule of each component of the decomposition product in the mixed gas according to the Graham's law, and performing cross-over removal operation and dynamic compensation through different weight ratios to finally obtain the content of each component of the decomposition product of the calculated mixed gas;
According to the Graham's law, N is observed under the same temperature and pressure2the diffusion rate of the gas as the intermediate decomposition product is SF62.28 times of the gas diffusion rate of the medium decomposition product, thereby leading to N under the same conditions2Decomposition product sensor response and SF in (1)6Similar relations also exist among sensor response quantities of medium decomposition products, but the proportional relations of the medium decomposition products are different for different components;
After a large number of high and low temperature experiments and different SF6Gas of decomposition product of the following specific componentTesting and determining a certain concentration of SF6gas experiment of decomposition products with different components with the volume content of 30 percent, data integration analysis, comprehensive consideration of all factors and obtaining SF with any proportion according to the formula (1)6/N2The multielement compound formula of the content of the decomposition products in the mixed gas is as follows:
（2）
Wherein:
compensating the coefficients for the raw sensor signal
Response of different sensors of the decomposition product sensing unit
Compensation coefficient for temperature and flow
Representing different decomposition product gases, for example: SO (SO)2、H2S、CO
pthe parameters are temperature and flow parameters.
The present embodiment is not intended to limit the shape, material, structure, etc. of the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.