SF6-N2 mixed gas comprehensive online monitoring device and monitoring method

Abstract

The invention discloses a comprehensive online monitoring device and method for SF6-N2 mixed gas. The device comprises a gas collection unit, a gas circulation unit, a detection unit and a control unit, 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 an inner cavity of the air storage tank and divides the inner cavity into a first cavity and a second cavity. The piston is connected with the movable push rod and slides in the inner cavity under the pushing of the movable push rod; the first cavity and the second cavity are communicated through a first switch module; the first cavity is communicated with the detection unit through the second switch module; the second cavity is communicated with the detection unit through the third switch module; the control unit is connected with the switch modules and the movable push rod and used for controlling on-off of the switch modules and movement of the movable push rod. The device has the advantages of simple structure, accurate detection, tail gas recovery, proportional inflation and the like.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of power equipment, and in particular to a comprehensive online monitoring device and a monitoring method for SF6-N2 mixed gas. Background Art

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

[0003] As for the detection method of trace water content, currently, portable offline methods such as electrolysis method, dew point method, and weight method are mostly used. These methods ignore the interference of air chamber temperature and pressure on the micro-water measurement results. At the same time, the tail gas generated during the treatment process may also pose a threat to the environment, showing obvious limitations. In particular, online monitoring of micro-water inside the GIS air chamber faces a great difficulty. As a sealed system, the GIS air chamber has very slow water vapor diffusion inside the air chamber. In addition, the deviation between the sensor temperature and the average temperature of the air chamber will lead to uneven moisture distribution, and the humidity is difficult to reach a stable state, which seriously restricts the accuracy of the test results. Therefore, to realize the online monitoring function of micro-water detection, it is also necessary to achieve breakthroughs in detection methods and devices.

[0004] In addition, the current method of mixed gas charging in proportion is to control the two gases in a mixing barrel to form a certain ratio through a mass flow meter, and then charge the gas into the GIS through a compressor. This method has two defects:

[0005] 1) The operation is extremely complicated. Multiple steps are required for inflation. After each inflation, the machine must be stopped to test the purity with an instrument. The relevant parameters must be manually adjusted according to the tested purity before inflation. The operation must be repeated in sequence.

[0006] 2) Poor versatility, the types and proportions of mixed gases are preset and cannot be changed at will. Summary of the invention

[0007] In view of the technical problems existing in the prior art, the present invention provides a comprehensive online monitoring device and a monitoring method for SF6-N2 mixed gas with simple structure, accurate detection and tail gas recovery.

[0008] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0009] A comprehensive online monitoring device for SF6-N2 mixed gas, 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 inner cavity of the gas storage tank and divides the inner 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 in the inner cavity of the gas storage tank under the push of the movable push rod;

[0011] The first cavity is connected to the second cavity through the first switch module; the first cavity is connected to the detection unit through the second switch module; the second cavity is connected to the detection unit through the third switch module;

[0012] 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;

[0013] The smart meter unit is communicatively connected with the control unit.

[0014] Preferably, the detection unit comprises a SF6-N2 gas density detection module and a trace water detection module; the SF6-N2 gas density detection module and the trace water detection module are connected in parallel and are 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 inside the gas chamber.

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

[0017] Preferably, 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.

[0018] Preferably, 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.

[0019] Preferably, the gas collection unit comprises a gas collection pipeline, both ends of which are respectively connected to the GIS air chamber and the first cavity, and an air inlet valve is provided 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 present invention also discloses a monitoring method based on the above-mentioned SF6-N2 mixed gas comprehensive online monitoring device, comprising the steps of:

[0022] S1, turn on the first switch module, turn off the second switch module and the third switch module, collect the mixed gas in the GIS air chamber into the first cavity through the gas collection unit, and enter the second cavity through the first switch module until the air pressure in the first cavity and the second cavity is the same as the air pressure in the GIS air chamber;

[0023] 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 cavity to the first cavity, so that the mixed gas in the first cavity enters the detection unit through the second switch module for detection; the detected gas enters the second cavity through the third switch module;

[0024] S3, after the detection unit is detected, 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 closes the first switch module;

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

[0026] Preferably, the method of charging the mixed gas in proportion is also included, specifically:

[0027] 1) Turn off the gas collection unit, and turn off the first switch module, the second switch module, and the third switch module;

[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) Fill the first cavity and the second cavity with SF6 and N2 respectively, and ensure that the gas pressures in the first cavity and the second cavity are consistent;

[0030] 4) Open the first switch module, 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 close the first switch module;

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

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

[0033] The SF6-N2 mixed gas comprehensive online monitoring device and monitoring method of the present invention are connected with multiple GIS gas chambers through a gas collection unit, and can detect multiple GIS gas chambers one by one, 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 inside the GIS gas chamber, thereby improving the accuracy of the detection result; the gas circulation unit realizes the tail gas recovery of the detection gas, thereby reducing the emission of SF6; the detection module can simultaneously realize online monitoring of the density and trace water content of the mixed gas, and the operation and maintenance personnel do not need to go to the site, thereby reducing the operation and maintenance cost; in addition, the gas circulation unit can realize the function of proportional inflation of the mixed gas, thereby solving the problem of proportional inflation of the SF6-N2 mixed gas in actual on-site production. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0036] Figure 3 It is a schematic diagram of the principle structure of the digital intelligent meter in the comprehensive online monitoring device of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

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

[0039] The gas collection unit includes a gas collection pipeline, both ends of which are connected to a plurality of GIS air chambers and the first cavity, and each gas collection pipeline is provided with an air inlet valve corresponding to each GIS air chamber.

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

[0041] The detection unit includes a 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 are located between the second switch module and the third switch module;

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

[0043] The digital intelligent 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 a 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 are located between the second switch module and the third switch module. The SF6-N2 gas density detection module includes a micro gas chamber for providing a gas diffusion site; a detection gas cavity is provided inside the micro gas chamber for installing a temperature sensor (such as PT100) and a micro-flow thermal conductivity sensor, and a flow meter is provided between the gas chamber and the second switch module for calculating the gas flow. Of course, in other embodiments, different detection modules can also be provided according to specific detection requirements.

[0045] Specifically, due to piston squeezing, the gas to be tested enters the micro gas chamber from the gas tank A through the solenoid valve 2# and the flowmeter, and the gas enters the detection gas cavity of the micro gas chamber due to diffusion (the temperature sensor and the micro flow thermal conductivity sensor are located inside the detection gas cavity) to detect the temperature and gas ratio; after the detection is completed, the tail gas returns to the gas tank B through the solenoid valve 3. This process can be cyclically detected to achieve cyclic detection of gas and recycling of tail gas.

[0046] The micro-water detection module includes the MDT242J series transmitter, including humidity sensor and temperature sensor, which has strong anti-condensation ability and is suitable for built-in environment.

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

[0048] The hot wire resistor of the micro-flow thermal conductivity sensor is heated by passing current to maintain a constant temperature. When the gas to be measured enters the detection chamber by diffusion, the gas will take away some heat due to heat conduction, causing the temperature of the hot wire resistor to drop, and its resistance value will also change. In this process, the micro-flow thermal conductivity sensor will output a voltage signal. Since the output voltage value is in a certain proportional relationship with the temperature change, quantitative calculation of the gas to be measured can be achieved. The calculation process is as follows:

[0049] Heat generated by the hot wire resistor P:

[0050] P=I 2 R m =I 2 R t (1+αΔT) (1)

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

[0052] Total heat loss energy Q:

[0053] Q=λSΔT (2)

[0054] Where λ is the thermal conductivity of the mixed gas; S is the contact area between the sensor and the gas.

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

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

[0057]

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

[0059]

[0060] In the formula, λ 1 and λ 2 are the thermal conductivity of SF6 and N2 respectively, ε 1 and ε 2are the volume fractions of SF6 and N2 respectively.

[0061]

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

[0063] like Figure 3 As shown, 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 security unit, a storage unit, an RTC clock unit and a communication unit; the power management unit is connected to the sensor access unit, the security unit and the storage unit respectively. The communication unit includes a wireless communication unit and a wired communication unit. The wired communication uses RS485 communication, and the wireless communication uses lora antenna communication.

[0064] The intelligent compensation algorithm module sets the meter type identification code, corresponds to 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 that uses I2C, SPI, and RS485 for digital transmission can be directly connected to the reserved I2C and SPI interfaces to communicate directly with the MCU. Secondly, the corresponding compensation algorithm is encapsulated into a unified algorithm library, and finally the relevant compensation algorithm is called through the identification code in the unified encapsulated algorithm library.

[0065] In specific applications, the process of realizing the integrated sensing and transmission of the above-mentioned digital intelligent meter unit is as follows:

[0066] First, 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 the compensation value to the meter device to complete the intelligent compensation.

[0067] Secondly, the monitoring module encapsulates the acquired perception data;

[0068] Finally, the monitoring module identifies the traffic mode, encapsulates the data and protocol in a unified manner, and then sends them to the monitoring terminal.

[0069] The present invention also discloses a monitoring method based on the above-mentioned SF6-N2 mixed gas comprehensive online monitoring device, comprising the steps of:

[0070] S1, open the first switch module (solenoid valve 1#), close the second switch module (solenoid valve 2#) and the third switch module (solenoid valve 3#), open the air inlet valve to collect the mixed gas in the GIS air chamber into the first cavity, and then enter the second cavity through the solenoid valve 1# until the air pressure in the first cavity and the second cavity is the same as the air pressure in the GIS air chamber;

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

[0072] S3, after the detection of the unit to be detected is completed, the solenoid valve 2# and the solenoid valve 3# are closed, the solenoid valve 1# is opened, 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 closes the solenoid valve 1#;

[0073] S4, open the intake valve, the control unit controls the movable push rod to push the piston from the second cavity to the first cavity, so that all the mixed gas returns to the GIS air chamber, and finally closes the intake valve to realize gas circulation and ensure no exhaust emission.

[0074] In addition, the SF6-N2 mixed gas comprehensive online monitoring device of the present invention can also realize the proportional inflation function of the mixed gas, solving the problem of proportional inflation of the GIS gas chamber of the mixed gas on site. The specific principle is:

[0075] According to the Clapeyron equation:

[0076] PV=nRT (6)

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

[0078]

[0079] Where V 1 and V 2 are the volume ratios of gas tanks A and B, n 1 and n 2 are the molar ratios of SF6 and N2 respectively.

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

[0081] The specific operation steps of the above method for implementing proportional inflation of mixed gas are as follows:

[0082] 1) Close the GIS air chamber inlet valve, close the solenoid valves 1#, 2#, and 3#, and turn off the detection function of the detection unit;

[0083] 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 gas storage tanks A and B is the volume ratio of SF6 to N2;

[0084] 3) Through the first inflation port ( Figure 1 Inlet A) and the second inlet ( Figure 1 Fill SF6 and N2 into gas storage tanks A and B respectively, and use a pressure gauge to ensure that the pressure of the gas on both sides is consistent;

[0085] 4) After the gas is filled, close the gas filling ports A and B on both sides of the gas tanks A and B, open the solenoid valve 1#, and move the piston push rod to the end of the gas tank B to fully mix SF6 and N2;

[0086] 5) Close solenoid valve 1#, open the air inlet valve of the GIS air chamber that needs to be inflated, move the piston push rod to the front end of gas tank A, squeeze the gas into the GIS air chamber, close the air inlet valve, and the inflation is completed.

[0087] The SF6-N2 mixed gas comprehensive online monitoring device and monitoring method of the present invention are connected with multiple GIS gas chambers through a gas collection unit, and can detect multiple GIS gas chambers one by one, 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 inside the GIS gas chamber, thereby improving the accuracy of the detection result; the gas circulation unit realizes the tail gas recovery of the detection gas, thereby reducing the emission of SF6; the detection module can simultaneously realize online monitoring of the density and trace water content of the mixed gas, and the operation and maintenance personnel do not need to go to the site, thereby reducing the operation and maintenance cost; in addition, the gas circulation unit can realize the function of proportional inflation of the mixed gas, thereby solving the problem of proportional inflation of the SF6-N2 mixed gas in actual on-site production.

[0088] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A comprehensive online monitoring device for SF6-N2 mixed gas, characterized in that: It includes a gas collection unit, a gas circulation unit, a detection unit, a control unit and an intelligent meter unit; 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 inner cavity of the gas storage tank and divides the inner 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 in the inner cavity of the gas storage tank under the push of the movable push rod; The first cavity is connected to the second cavity through the first switch module; the first cavity is connected to the detection unit through the second switch module; the second cavity is connected to the detection unit through the 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 with the control unit.

2. The SF6-N2 mixed gas comprehensive online monitoring device according to claim 1 is characterized in that: The detection unit comprises a SF6-N2 gas density detection module and a trace water detection module; the SF6-N2 gas density detection module and the trace water detection module are connected in parallel and are located between the second switch module and the third switch module.

3. The SF6-N2 mixed gas comprehensive online monitoring device according to claim 2 is characterized in that: The SF6-N2 gas density detection module comprises a gas chamber, and a temperature sensor and a micro-flow thermal conductivity sensor are arranged inside the gas chamber.

4. The SF6-N2 mixed gas comprehensive 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 comprehensive 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 safety unit, a storage unit and a communication unit; the power management unit is connected to the sensor access unit, the safety unit, the storage unit and the communication unit respectively.

6. The SF6-N2 mixed gas comprehensive online monitoring device according to claim 5 is 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. The SF6-N2 mixed gas comprehensive online monitoring device according to claim 1, 2 or 3, characterized in that: The gas collection unit comprises a gas collection pipeline, both ends of which are respectively connected to the GIS air chamber and the first cavity, and an air inlet valve is arranged on the gas collection pipeline.

8. The SF6-N2 mixed gas comprehensive online monitoring device according to claim 1, 2 or 3, characterized in that: The first cavity is provided with a first inflation port, and the second cavity is provided with a second inflation port.

9. A monitoring method based on the SF6-N2 mixed gas comprehensive online monitoring device according to any one of claims 1 to 8, characterized in that: Includes steps: S1, turn on the first switch module, turn off the second switch module and the third switch module, collect the mixed gas in the GIS air chamber into the first cavity through the gas collection unit, and enter the second cavity through the first switch module until the air pressure in the first cavity and the second cavity is the same as the air pressure in the GIS air 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 cavity to the first cavity, so that the mixed gas in the first cavity enters the detection unit through the second switch module for detection; the detected gas enters the second cavity through the third switch module; S3, after the detection unit is detected, 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 closes the first switch module; S4. Open the gas collection unit, and the control unit controls the movable push rod to push the piston from the second cavity to the first cavity, so that all the mixed gas returns to the GIS gas chamber, and finally close the gas collection unit to realize gas circulation.

10. The monitoring method of the SF6-N2 mixed gas comprehensive online monitoring device according to claim 9 is characterized in that: It also includes a method for charging the mixed gas in proportion, specifically: 1) Turn off the gas collection 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 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; 3) Fill the first cavity and the second cavity with SF6 and N2 respectively, and ensure that the gas pressures in the first cavity and the second cavity are consistent; 4) Open the first switch module, 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 close the first switch module; 5) Open the gas collection unit, and the control unit controls the movable push rod to push the piston from the second cavity to the first cavity, so that all the mixed gas is squeezed into the GIS air chamber, and the gas collection unit is closed, and the inflation is completed.

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