SF6-n2 mixed gas comprehensive on-line monitoring device and monitoring method

Abstract

The application discloses a kind of SF6-N2 mixed gas comprehensive on-line monitoring device and monitoring method, device includes gas collection unit, gas circulation unit, detection unit and control unit;Gas circulation unit includes gas storage tank, piston, movable push rod, first switch module, second switch module and third switch module;Piston is located in the internal cavity of gas storage tank and separates internal cavity into first cavity and second cavity;Piston is connected with movable push rod, and under the push of movable push rod, it slides in internal cavity;First cavity is communicated with second cavity by first switch module;First cavity is communicated with detection unit by second switch module;Second cavity is communicated with detection unit by third switch module;Control unit is connected with each switch module and movable push rod respectively, for controlling the on-off of each switch module and the movement of movable push rod.The application has the advantages of simple structure, accurate detection, tail gas recovery and proportional inflation.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of power equipment, and particularly relates to an SF6-N2 mixed gas comprehensive online monitoring device and a monitoring method. BACKGROUND

[0002] In order to comprehensively promote energy saving and emission reduction of power grid equipment and reduce the use and emission of greenhouse gas SF6, the State Grid Corporation of China is currently vigorously promoting the use of 25% SF6 / 75% N2 mixed insulation gas to replace pure SF6. The content mixing ratio and the micro water content of the mixed insulation gas are important indicators for evaluating the state of electrical equipment, and are directly related to the insulation and arc extinguishing performance of the equipment. Among them, due to the new characteristics of SF6 mixed insulation gas, the resolution and selectivity of the original SF6 gas density relay are insufficient, and the concentration ratio of each component in the mixed gas cannot be accurately measured. At the same time, there is a lack of online monitoring method for the density of SF6-N2 mixed insulation gas, and it is urgent to develop an online monitoring device for the density of SF6-N2 mixed insulation gas.

[0003] For the detection method of micro water content, currently, portable offline methods such as electrolytic method, dew point method, and gravimetric method are used. These methods ignore the interference of gas chamber temperature and pressure on the micro water measurement results, and the tail gas generated in the processing process may also pose a threat to the environment, showing obvious limitations. In particular, it is a big problem to perform online monitoring of micro water in the GIS gas chamber. As a sealed system, the water vapor diffusion in the gas chamber is very slow, and the deviation between the sensor temperature and the average temperature of the gas chamber will cause uneven distribution of water and difficulty in reaching a stable state of humidity, thereby seriously restricting the accuracy of the detection results. Therefore, to realize the online monitoring function of micro water detection, breakthroughs are also needed in the detection method and device.

[0004] In addition, at present, the mixed gas is mainly filled in proportion by controlling the two gases in a mixing barrel through a mass flow meter to form a certain proportion, and then the gas is filled into the GIS through a compressor. This method has two defects:

[0005] 1) The operation is extremely complex. When filling gas, multiple filling steps are required, and after each filling, the machine must be stopped to detect the purity with an instrument. After adjusting the relevant parameters manually according to the tested purity, the gas is filled again, and the operation is repeated in turn.

[0006] 2) Poor universality. The variety and proportion of mixed gas are pre-set and cannot be changed at will. SUMMARY

[0007] In view of the technical problems existing in the prior art, the present application provides an SF6-N2 mixed gas comprehensive online monitoring device and a monitoring method, which are simple in structure, accurate in detection, and have tail gas recycling.

[0008] To solve the above technical problems, the technical scheme provided by the present application is:

[0009] A SF6-N2 mixed gas comprehensive online monitoring device, comprising a gas collection unit, a gas circulation unit, a detection unit, a control unit and an intelligent meter unit;

[0010] The gas circulation unit comprises a gas storage tank, a piston, a movable push rod, a first switch module, a second switch module and a third switch module; the piston is located in the internal cavity of the gas storage tank and divides the internal cavity of the gas storage tank into a first cavity and a second cavity; the piston is connected with the movable push rod and slides in the internal cavity of the gas storage tank under the pushing of the movable push rod;

[0011] The first cavity and the second cavity are communicated through the first switch module; the first cavity is communicated with the detection unit through the second switch module; and the second cavity is communicated with the detection unit through the third switch module;

[0012] The control unit is connected with the first switch module, the second switch module, the third switch module and the movable push rod respectively, and is used for controlling the on-off of each switch module and the movement of the movable push rod;

[0013] The intelligent meter unit is in communication connection with the control unit.

[0014] Preferably, the detection unit comprises an SF6-N2 gas density detection module and a micro-water detection module; the SF6-N2 gas density detection module and the micro-water detection module are connected in parallel and located between the second switch module and the third switch module.

[0015] Preferably, the SF6-N2 gas density detection module comprises a gas chamber, and a temperature sensor and a micro-flow thermal conductivity sensor are arranged in the gas chamber.

[0016] Preferably, the first switch module, the second switch module and the third switch module are all electromagnetic valves.

[0017] Preferably, the intelligent meter unit comprises a monitoring module; the monitoring module comprises a power management unit, a sensor access unit, a safety unit, a storage unit and a communication unit; the power management unit is connected with the sensor access unit, the safety unit, the storage unit and the communication unit respectively.

[0018] Preferably, the communication unit comprises a wireless communication unit and a wired communication unit; the wired communication unit is RS485, and the wireless communication unit is a lora antenna.

[0019] Preferably, the gas collection unit comprises a gas collection pipeline, two ends of the gas collection pipeline are respectively communicated with a GIS gas chamber and the first cavity, and an air inlet valve is arranged on the gas collection pipeline.

[0020] Preferably, the first cavity is provided with a first inflation port, and the second cavity is provided with a second inflation port.

[0021] The application also discloses a monitoring method based on the SF6-N2 mixed gas comprehensive online monitoring device.

[0022] S1, the first switch module is opened, the second switch module and the third switch module are closed, the mixed gas in the GIS gas chamber is collected into the first cavity through the gas collection unit, and then enters the second cavity through the first switch module until the gas pressure in the first cavity and the second cavity is the same as that in the GIS gas chamber;

[0023] S2, the gas collection unit and the first switch module are closed, the second switch module and the third switch module are opened, and the control unit controls the movable push rod to push the piston to move from the second cavity to the first cavity, so that the mixed gas in the first cavity enters the detection unit for detection through the second switch module; the detected gas enters the second cavity through the third switch module;

[0024] S3, after the detection unit finishes detection, the second switch module and the third switch module are closed, the first switch module is opened, the control unit controls the movable push rod to push the piston to the end of the second cavity away from the first cavity, and then the first switch module is closed;

[0025] S4, the gas collection unit is opened, the control unit controls the movable push rod to push the piston to move from the second cavity to the first cavity, so that the mixed gas returns to the GIS gas chamber, and finally the gas collection unit is closed to realize gas circulation.

[0026] Preferably, the method further comprises a gas inflation method for proportionally mixing the mixed gas, and specifically comprises:

[0027] 1) the gas collection unit is closed, and the first switch module, the second switch module and the third switch module are closed;

[0028] 2) the control unit controls the movable push rod to push the piston to move to a preset position, so that the volume ratio of the first cavity to the second cavity is the volume ratio of SF6 to N2;

[0029] 3) SF6 and N2 are respectively filled into the first cavity and the second cavity, and the gas pressure in the first cavity and the second cavity is ensured to be consistent;

[0030] 4) the first switch module is opened, the control unit controls the movable push rod to push the piston to the end of the second cavity away from the first cavity, so that SF6 and N2 are fully mixed, and then the first switch module is closed;

[0031] 5) Open the gas collection unit. The control unit controls the movable push rod to push the piston from the second chamber to the first chamber, so that all the mixed gas is squeezed into the GIS gas chamber. Close the gas collection unit and the inflation is complete.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] The SF6-N2 mixed gas integrated online monitoring device and method of the present invention connects to multiple GIS gas chambers through a gas acquisition unit, enabling the sequential monitoring of multiple GIS gas chambers, thereby reducing the number of detection instruments. The gas circulation unit ensures that the gas measured by the detection module is flowing in real-time within the GIS gas chambers, improving the accuracy of the detection results. The gas circulation unit also enables the recovery of exhaust gas from the detected gas, reducing SF6 emissions. The detection module can simultaneously perform online monitoring of the mixed gas density and trace moisture content, eliminating the need for on-site maintenance personnel and reducing maintenance costs. Furthermore, the gas circulation unit enables proportional gas filling of the mixed gas, solving the problem of proportional filling of SF6-N2 mixed gas in actual on-site production. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the integrated online monitoring device of the present invention in an embodiment.

[0035] Figure 2 This is a diagram illustrating a specific application of the mixed gas density detection unit in the integrated online monitoring device of the present invention.

[0036] Figure 3 This is a schematic diagram illustrating the principle and structure of the digital smart meter in the integrated online monitoring device of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1 As shown, the SF6-N2 mixed gas integrated online monitoring device provided in this embodiment of the invention includes a gas acquisition unit, a gas circulation unit, a detection unit, a core control unit, and a digital intelligent metering unit;

[0039] The gas acquisition unit includes a gas acquisition pipeline, with both ends of the gas acquisition pipeline connected to multiple GIS gas chambers and the first cavity, respectively. Each gas acquisition pipeline is equipped with an inlet valve, which corresponds to each GIS gas chamber.

[0040] The gas circulation unit includes a gas tank, a piston, a movable push rod, and a first switch module. Figure 1 Solenoid valve #1 and second switch module (in the middle) Figure 1 Solenoid valve #2 and the third switch module (in the middle)Figure 1 The solenoid valve #3 in the middle; the piston is located in the internal cavity of the gas tank and divides the internal cavity of the gas tank into the first cavity ( Figure 1 The gas storage tank A) and the second chamber ( Figure 1 In the gas storage tank B), the piston and the cavity are sealed by a sealing ring; the piston is connected to a movable push rod and slides inside the gas storage tank under the push of the movable push rod; the first cavity and the second cavity are connected by a first switch module; the first cavity is connected to the detection unit through a second switch module; the second cavity is connected to the detection unit through a third switch module.

[0041] The detection unit includes an SF6-N2 gas density detection module and a trace moisture detection module; the SF6-N2 gas density detection module and the trace moisture detection module are connected in parallel and located between the second switch module and the third switch module;

[0042] The core control unit is connected to the intake valve, the first switch module, the second switch module, the third switch module and the movable push rod respectively, and is used to control the on and off of the intake valve and each switch module as well as the movement of the movable push rod;

[0043] The digital smart meter unit includes a monitoring module and an intelligent compensation algorithm module, which are responsible for realizing wired / wireless dual-mode communication and intelligent algorithm compensation.

[0044] like Figure 2 As shown, the detection unit includes an SF6-N2 gas density detection module and a trace moisture detection module; the SF6-N2 gas density detection module and the trace moisture detection module are connected in parallel and located between the second switch module and the third switch module. The SF6-N2 gas density detection module includes a miniature gas chamber for providing a gas diffusion area; the miniature gas chamber has a detection gas cavity for mounting a temperature sensor (such as PT100) and a micro-flow thermal conductivity sensor; a flow meter is installed between the gas chamber and the second switch module for calculating the gas flow rate. Of course, in other embodiments, different detection modules can be set according to specific detection requirements.

[0045] Specifically, due to piston compression, the gas to be tested enters the micro gas chamber from the gas storage tank A through solenoid valve 2# and the flow meter. The gas then diffuses into the detection chamber (where the temperature sensor and micro-flow thermal conductivity sensor are located) for temperature and gas ratio detection. After detection, the exhaust gas returns to the gas storage tank B through solenoid valve 3. This process can be repeated, enabling cyclic detection of the gas and exhaust gas recycling.

[0046] The micro-moisture detection module includes the MDT242J series transmitter, which includes a humidity sensor and a temperature sensor. It has strong anti-condensation capabilities and is suitable for built-in environments.

[0047] The specific detection process of the micro-flow thermal conductivity sensor (such as TCS208F) is as follows:

[0048] The hot wire resistance of the micro-flow thermal conductivity sensor is connected to an electric current for heating and maintaining a constant temperature. When the gas to be measured enters the detection chamber by diffusion, the gas will take away part of the heat due to heat conduction, causing the temperature of the hot wire resistance to drop, and the resistance value will also change. In this process, the micro-flow thermal conductivity sensor outputs a voltage signal, and since the output voltage value is proportional to the temperature change, quantitative calculation of the gas to be measured can be realized, and the calculation process is as follows:

[0049] The heat generated by the hot wire resistance P:

[0050] P = I 2 R m = I 2 R t (1 + aAT) (1)

[0051] In the formula, I is the current value flowing through the hot wire resistance; a is the thermal temperature coefficient of the hot wire resistance; R m is the resistance value of the hot wire resistance during detection; R t is the resistance value of the hot wire resistance at the initial ambient temperature; and AT is the difference between the equilibrium temperature and the initial ambient temperature.

[0052] Total heat loss energy Q:

[0053] Q = ASAT (2)

[0054] In the formula, A is the thermal conductivity of the mixed gas; and S is the contact area of the sensor and the gas.

[0055] According to the heat balance principle, since the sensor has good thermal insulation material, only the heat transfer process caused by heat convection is considered, and the heat generated by the heating wire through the external power supply is equal to the total heat loss energy, that is, P = Q.

[0056] According to formulas (1)-(2), the thermal conductivity A of the mixed gas can be obtained:

[0057]

[0058] It is known that the thermal conductivity of a multi-component mixed gas is equal to the weighted average value of the thermal conductivity of each component, as shown in formula (4):

[0059]

[0060] In the formula, A1 and A2 are the thermal conductivities of SF6 and N2, respectively, and e1 and e2 are the volume fractions of SF6 and N2, respectively.

[0061]

[0062] The thermal conductivities of SF6 and N2 at different temperatures are known, and the volume fractions of SF6 and N2 in the mixed gas are finally calculated according to formula (3) and formula (5), respectively.

[0063] As shown in Figure 3 The digital intelligent meter unit includes a general monitoring module and an intelligent compensation algorithm module. The general monitoring module includes a sensor access unit, a power management unit, a safety unit, a storage unit, an RTC clock unit and a communication unit; the power management unit is connected with the sensor access unit, the safety unit and the storage unit respectively. The communication unit includes a wireless communication unit and a wired communication unit, the wired communication selects RS485 communication, and the wireless communication selects lora antenna communication.

[0064] The intelligent compensation algorithm module sets a meter type identification code, identifies the digital meter compensation algorithm (conventional algorithm, such as temperature compensation algorithm, etc.) through the identification code, and sets a compatible hardware interface in the general module. Among them, the sensor interface for digital transmission through I2C, SPI and RS485 can be directly connected to the reserved I2C and SPI interfaces, and directly communicates with the MCU. Secondly, the corresponding compensation algorithm is packaged into a unified algorithm library, and finally the related compensation algorithm is called through the identification code in the unified packaged algorithm library.

[0065] In specific application, the implementation process of the above-mentioned digital intelligent meter unit is as follows:

[0066] Firstly, the meter device sends an identification code to the monitoring module, the monitoring module accesses the intelligent compensation function library through the identification code, the function sends a compensation value to the meter device, and the intelligent compensation is completed;

[0067] Secondly, the monitoring module encapsulates the sensing data obtained;

[0068] Finally, the monitoring module identifies the passing mode, uniformly encapsulates the data and the protocol, and then sends to the monitoring terminal.

[0069] The application further discloses a monitoring method based on the SF6-N2 mixed gas comprehensive online monitoring device.

[0070] S1, open the first switch module (electromagnetic valve 1#), close the second switch module (electromagnetic valve 2#) and the third switch module (electromagnetic valve 3#), open the inlet valve, collect the mixed gas in the GIS gas chamber into the first cavity, and enter into the second cavity through the electromagnetic valve 1#, until the gas pressures in the first cavity and the second cavity are the same as that in the GIS gas chamber;

[0071] S2, close the intake valve and the electromagnetic valve 1#, open the electromagnetic valve 2# and the electromagnetic valve 3#; the control unit controls the movable push rod to push the piston to move from the second cavity to the first cavity, so that the mixed gas in the first cavity enters the detection unit through the electromagnetic valve 2# for detection; the detected gas enters the second cavity through the electromagnetic valve 3#;

[0072] S3, after the detection unit finishes detection, close the electromagnetic valve 2# and the electromagnetic valve 3#, open the electromagnetic valve 1#, the control unit controls the movable push rod to push the piston to the end of the second cavity away from the first cavity, and then close the electromagnetic valve 1#;

[0073] S4, open the intake valve, the control unit controls the movable push rod to push the piston to move from the second cavity to the first cavity, so that the mixed gas returns to the GIS gas chamber, and finally close the intake valve, realizing gas circulation and ensuring no tail gas emission.

[0074] In addition, the SF6-N2 mixed gas comprehensive online monitoring device can also realize the proportional charging function of the mixed gas, solve the problem of proportional charging of the GIS gas chamber of the mixed gas on site, and the specific principle is:

[0075] According to the Clapearon equation:

[0076] PV = nRT (6)

[0077] When SF6 and N2 are respectively filled in the two cavities of the gas storage tank A and B, the pressure of the two gas chambers is ensured to be consistent through the pressure gauge, and the following can be obtained:

[0078]

[0079] In the formula, V1 and V2 are the volume ratio of the gas storage tank A and B respectively, and n1 and n2 are the amount of substance ratio of SF6 and N2 respectively.

[0080] Therefore, by moving the piston push rod to control the volume of the gas storage tank A and B, the mixed gas of the required proportion can be obtained.

[0081] The specific operation steps of the above-mentioned method for realizing the proportional charging of the mixed gas are as follows:

[0082] 1) Close the GIS gas chamber intake valve, close the electromagnetic valve 1#, 2# and 3#, and close the detection function of the detection unit;

[0083] 2) The control unit controls the movable push rod to push the piston to move to the preset position, so that the volume ratio of the gas storage tank A and B is the volume ratio of SF6 and N2;

[0084] 3) Charge through the first charging port (the charging port A in the first charging port) and the second charging port (the charging port B in the second charging port) Figure 1 Figure 1 ​The gas inlet B) in the gas tank A, B respectively fills SF6 and N2, and the pressure gauges are used to ensure that the gas pressure on both sides is consistent.

[0085] 4) After the gas filling is completed, the gas inlet A, B on both sides of the gas tank A, B is closed, the electromagnetic valve 1# is opened, the piston push rod is moved to the tail end of the gas tank B, and SF6 and N2 are fully mixed;

[0086] 5) The electromagnetic valve 1# is closed, the GIS gas chamber gas inlet valve is opened, the piston push rod is moved to the head end of the gas tank A, the gas is extruded into the GIS gas chamber, the gas inlet valve is closed, and the gas filling is completed.

[0087] The SF6-N2 mixed gas comprehensive online monitoring device and the monitoring method can realize the detection of multiple GIS gas chambers one by one, so that the number of detection instruments is reduced; the gas circulation unit is used to ensure that the gas detected by the detection module is the real-time flow in the GIS gas chamber, so that the accuracy of the detection result is improved; the gas circulation unit realizes the tail gas recovery of the detection gas, so that the emission of SF6 is reduced; the detection module can realize the online monitoring of the mixed gas density and the micro water content at the same time, so that the operation and maintenance personnel do not need to go to the scene, and the operation and maintenance cost is reduced; in addition, the gas circulation unit can realize the proportional gas filling function of the mixed gas, and solves the problem of proportional gas filling of SF6-N2 mixed gas in the actual production on site.

[0088] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the technical field, some improvements and decorations without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A comprehensive online monitoring device for SF6-N2 mixed gas, characterized in that, It includes a gas acquisition unit, a gas circulation unit, a detection unit, a control unit, and a smart meter unit; The gas circulation unit includes a gas storage tank, a piston, a movable push rod, a first switch module, a second switch module, and a third switch module; the piston is located inside the internal cavity of the gas storage tank and divides the internal cavity of the gas storage tank into a first cavity and a second cavity; the piston is connected to the movable push rod and slides inside the internal cavity of the gas storage tank under the push of the movable push rod. The first cavity and the second cavity are connected through a first switch module; the first cavity is connected to the detection unit through a second switch module; the second cavity is connected to the detection unit through a third switch module. The control unit is connected to the first switch module, the second switch module, the third switch module and the movable push rod respectively, and is used to control the on and off of each switch module and the movement of the movable push rod; The smart meter unit is communicatively connected to the control unit; The gas collection unit includes a gas collection pipeline, the two ends of which are connected to the GIS gas chamber and the first cavity, respectively, and an inlet valve is provided on the gas collection pipeline. The first cavity is provided with a first air inlet, and the second cavity is provided with a second air inlet.

2. The SF6-N2 mixed gas integrated online monitoring device according to claim 1, characterized in that, The detection unit includes an SF6-N2 gas density detection module and a trace moisture detection module; the SF6-N2 gas density detection module and the trace moisture detection module are connected in parallel and located between the second switch module and the third switch module.

3. The SF6-N2 mixed gas integrated online monitoring device according to claim 2, characterized in that, The SF6-N2 gas density detection module includes a gas chamber, inside which a temperature sensor and a micro-flow thermal conductivity sensor are installed.

4. The SF6-N2 mixed gas integrated online monitoring device according to claim 2 or 3, characterized in that, The first switch module, the second switch module, and the third switch module are all solenoid valves.

5. The SF6-N2 mixed gas integrated online monitoring device according to claim 1, 2, or 3, characterized in that, The smart meter unit includes a monitoring module; the monitoring module includes a power management unit, a sensor access unit, a security unit, a storage unit, and a communication unit; the power management unit is connected to the sensor access unit, the security unit, the storage unit, and the communication unit respectively.

6. The SF6-N2 mixed gas integrated online monitoring device according to claim 5, characterized in that, The communication unit includes a wireless communication unit and a wired communication unit; the wired communication unit is RS485, and the wireless communication unit is a LoRa antenna.

7. A monitoring method based on the SF6-N2 mixed gas integrated online monitoring device according to any one of claims 1-6, characterized in that, Including the following steps: S1. Open the first switch module, close the second and third switch modules, collect the mixed gas in the GIS gas chamber into the first cavity through the gas collection unit, and enter the second cavity through the first switch module until the gas pressure in the first and second cavities is the same as the gas pressure in the GIS gas chamber. S2. Close the gas collection unit and the first switch module, and open the second switch module and the third switch module; the control unit controls the movable push rod to push the piston from the second chamber to the first chamber, so that the mixed gas in the first chamber enters the detection unit for detection through the second switch module; the detected gas then enters the second chamber through the third switch module. S3. After the detection unit has completed the detection, close the second switch module and the third switch module, open the first switch module, and the control unit controls the movable push rod to push the piston to the end of the second cavity away from the first cavity, and then close the first switch module. S4. Open the gas collection unit. The control unit controls the movable push rod to push the piston from the second chamber to the first chamber, so that all the mixed gas returns to the GIS gas chamber. Finally, close the gas collection unit to realize gas circulation.

8. The monitoring method of the SF6-N2 mixed gas integrated online monitoring device according to claim 7, characterized in that, It also includes a method for mixing gases in a specific ratio during inflation, specifically: 1) Turn off the gas acquisition unit, and turn off the first switch module, the second switch module, and the third switch module; 2) The control unit controls the movable push rod to push the piston to a preset position, so that the volume ratio of the first chamber to the second chamber is the volume ratio of SF6 to N2; 3) Fill the first chamber and the second chamber with SF6 and N2 respectively, and ensure that the gas pressure in the first chamber and the second chamber is the same; 4) Open the first switch module, and the control unit controls the movable push rod to push the piston to the end of the second chamber away from the first chamber, so that SF6 and N2 are fully mixed, and then close the first switch module; 5) Open the gas collection unit. The control unit controls the movable push rod to push the piston from the second chamber to the first chamber, so that all the mixed gas is squeezed into the GIS gas chamber. Close the gas collection unit and the inflation is complete.

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