SF6 switch mixed gas volume ratio automatic adjusting device and control method

Abstract

The invention relates to an SF6 switch mixed gas volume ratio automatic adjusting device and a control method.The adjusting device comprises a chromatographic measurement unit and a main inflation pipeline, the main inflation pipeline is communicated between an SF6 mixed gas switch gas chamber and the chromatographic measurement unit, and an electromagnetic switching valve and a third flow controller are arranged on the main inflation pipeline; a pressure transmitter is arranged at one end, close to the SF6 gas mixing switch gas chamber, of the main gas filling pipeline; the first branch pipe is communicated with the sulfur hexafluoride inflation tank, the second branch pipe is communicated with the nitrogen tank, the other end of the first branch pipe is communicated with the other end of the second branch pipe and then is connected to one port of the electromagnetic switching valve, and the first branch pipe and the second branch pipe are respectively and sequentially provided with a pressure reducing valve, a flow controller and an electromagnetic valve; the system further comprises an industrial personal computer capable of collecting measurement data of the pressure transmitter, the flow controllers and the chromatographic measurement units and controlling on-off of the electromagnetic valves. And the volume ratio of the mixed gas in the SF6 mixed gas switch can be quickly and accurately adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical equipment, and in particular to a portable SF6 switch mixed gas volume ratio precision automatic adjustment device and a control method. Background Art

[0002] SF6 mixed gas switches are widely used in power systems. In actual practice, the mixed gas is mostly mixed and injected using pure gas on site, which leads to deviations in the volume ratio of the mixed gas. This does not meet the SF6 mixed gas volume ratio accuracy requirement of 1% stipulated in DL / T 1986-2019 (Technical Specifications for Gas Detection of Sulfur Hexafluoride Mixed Gas Insulation Equipment). A special adjustment device is required to accurately adjust the mixed gas volume ratio of the SF6 mixed gas.

[0003] At the same time, the SF6 mixed gas switch has gas leakage in actual operation. After the gas is replenished by the gas replenisher, a special adjustment device is also required to accurately adjust the mixed gas volume ratio of the SF6 mixed gas switch.

[0004] Most existing technologies directly use pure gas for on-site mixing. There is no equipment monitoring to effectively measure the gas mixing ratio. The gas mixing devices used on-site often fail to meet the requirements of accurate gas mixing ratio adjustment, and the mixing error is large. In addition, SF6 purity probes are mostly used for feedback measurement, which has a large measurement error. To meet the requirements and specifications of DL / T 1986-2019, chromatographic analysis should be used to accurately analyze the gas mixing ratio.

[0005] The prior art has no volume ratio adjustment device for the injected mixed gas. If a deviation is detected, the mixed gas can only be put back in and refilled. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the above-mentioned prior art, thereby providing an SF6 switch mixed gas volume ratio automatic adjustment device and control method, which can quickly and accurately adjust the mixed gas volume ratio in the SF6 mixed gas switch.

[0007] An automatic regulating device for the volume ratio of mixed gas in a SF6 switch, comprising:

[0008] A chromatographic measuring unit, which is used to measure the proportion of each component of the mixed gas;

[0009] A main gas-filling pipeline, the main gas-filling pipeline is connected between the SF6 gas-mixing switch air chamber and the chromatographic measurement unit, the main gas-filling pipeline is provided with an electromagnetic switching valve and a flow controller for controlling the flow rate, and a pressure transmitter is provided at one end of the main gas-filling pipeline close to the SF6 gas-mixing switch air chamber, and the pressure transmitter is used to measure the pressure change in the SF6 gas-mixing switch air chamber before and after deflation;

[0010] A first branch pipe connected to a sulfur hexafluoride gas filling tank for filling sulfur hexafluoride and a second branch pipe connected to a nitrogen gas tank for filling nitrogen. The other ends of the first branch pipe and the second branch pipe are connected and then connected to one port of an electromagnetic switching valve. A pressure reducing valve, a flow controller, and a solenoid valve are sequentially arranged on both the first branch pipe and the second branch pipe;

[0011] It also includes an industrial control computer that can collect the measurement data of the pressure transmitter, each flow controller, and the chromatographic measurement unit, and control the opening and closing of each solenoid valve.

[0012] Both ends of the main gas filling pipeline are provided with conversion joints for docking with the SF6 mixed gas switch gas chamber and the chromatographic measurement unit.

[0013] A filter is provided at one end of the main gas filling pipeline close to the SF6 mixed gas switch gas chamber.

[0014] The industrial control computer is connected to the pressure transmitter and each flow controller through a 485 communication network, and the industrial control computer is connected to the chromatographic measurement unit through a 232 communication network.

[0015] The chromatographic measurement unit includes a thermal conductivity detector and a chromatographic workstation.

[0016] The chromatographic measurement unit, the main gas filling pipeline, the sulfur hexafluoride gas filling tank, the nitrogen gas tank, the first branch pipe, and the second branch pipe are arranged on a workbench with wheels at the bottom of the same work.

[0017] It also includes a temperature sensor for collecting the current gas temperature.

[0018] A control method for an SF6 switch mixed gas volume ratio automatic adjustment device, characterized by comprising the following steps:

[0019] The industrial control computer controls the pressure transmitter to measure the pressure P of the SF6 mixed gas switch gas chamber before deflation 前 ;

[0020] The industrial control computer controls the electromagnetic switching valve to conduct the main gas filling pipeline, close the solenoid valves on the first branch pipe and the second branch pipe. The mixed gas in the SF6 mixed gas switch gas chamber enters the chromatographic measurement unit through the main gas filling pipeline. At the same time, the industrial control computer collects the gas flow Q measured by the flow controller three;

[0021] After t time, the industrial control computer controls the electromagnetic switching valve to close, and the pressure transmitter measures the pressure P of the SF6 mixed gas switch gas chamber after deflation 后 ;

[0022] Measure the mixing ratio concentration N of the mixed gas entering the chromatographic measurement unit. After measurement, the mixed gas is emptied through the exhaust port of the chromatographic measurement unit;

[0023] Calculate the volume ΔV flowing out of the gas chamber of the SF6 mixed gas switch: ΔV = Q * t; calculate the volume of the gas chamber of the SF6 mixed gas switch According to the volume V of the gas chamber and the results measured by the chromatographic measurement unit, calculate the volume of gas to be filled

[0024] The calculation formula for the volume of gas to be filled is as follows:

[0025] When N > N0, V1 = K1V(N - N0);

[0026] When N < N0, V2 = K2V(N0 - N);

[0027] Where V1 is the volume of nitrogen gas to be filled when N > N0, V2 is the volume of pure SF6 gas to be filled when N < N0, K1 and K2 are calibration constants, and N0 is the mixed gas ratio concentration specified in the DL / T1986 - 2019Z standard

[0028] The present invention only uses a chromatographic unit to analyze the volume ratio of the mixed gas, and relies on three groups of solenoid valves and intelligent flow controllers to achieve precise adjustment of the volume ratio of the mixed gas. The present invention does not need to adopt power devices such as air pumps, and relies on the body pressure of the switch gas chamber and the gas filling cylinder to realize gas flow. The overall weight of the device can be controlled below twenty-five kilograms, achieving portability and facilitating on-site use by technicians

[0029] The advantages of the present invention compared with the prior art are as follows:

[0030] 1. Mobility: Equipped with a workbench with wheels, place the adapter, gas cylinder, etc. on the workbench together, and move it conveniently to the switch where the volume ratio of the mixed gas needs to be adjusted, improving work efficiency

[0031] 2. Intelligent control: Automatically controlled by a control system, the adjustment process is fully automated, reducing human operation errors

[0032] 3. High adjustment accuracy: Use a chromatographic measurement unit to measure the volume ratio of the SF6 mixed gas switch

[0033] 3. High-efficiency filtration: The filter can effectively remove impurities in the gas, ensuring quality

[0034] 4. Safe and reliable: The pressure sensor monitors the gas pressure in real time to ensure the safety and reliability of the adjustment process

[0035] 5. Display and alarm: The device is equipped with a display screen, which can display parameters such as gas pressure and flow rate in real time, and give an alarm in case of abnormality Brief Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the adjustment device of the present invention

[0037] Figure 2 It is a block diagram of an adjustment device module assembly;

[0038] Figure 3 It is a schematic structural diagram of a chromatographic measurement unit. Specific implementation manners

[0039] As Figures 1-3 , this device includes a main charging pipeline 2, and the main charging pipeline 2 is connected between the SF6 gas mixture switch chamber 3 and the chromatographic measurement unit 1. The chromatographic measurement unit 1 is used to measure the proportion of each component in the gas mixture; conversion joints 13 for docking with the SF6 gas mixture switch chamber 3 and the chromatographic measurement unit 1 are provided at both ends of the main charging pipeline 2. A filter 4 is provided at one end of the main charging pipeline 2 close to the SF6 gas mixture switch chamber 3. An electromagnetic switching valve 6 and a flow controller III 7 for controlling the flow rate are provided on the main charging pipeline 2. The electromagnetic switching valve 6 is a two-position three-way solenoid valve. The electromagnetic switching valve 6 has three ports, two of which are connected in series on the main charging pipeline 2, and the pipeline led out from the other port is divided into two paths, namely the first branch pipe 8 and the second branch pipe 9, and then connected to the sulfur hexafluoride charging tank 11 and the nitrogen tank 12. A pressure reducing valve I 14, a flow controller I 15 and a solenoid valve I 16 are arranged in sequence on the first branch pipe 8. A pressure reducing valve II 17, a flow controller II 18 and a solenoid valve II 19 are arranged in sequence on the second branch pipe 9. A pressure transmitter 5 is provided at one end of the main charging pipeline 2 close to the SF6 gas mixture switch chamber 3. The pressure transmitter 5 is used to measure the pressure change in the SF6 gas mixture switch chamber 3 before and after deflation. A temperature sensor 20 for collecting the current gas temperature is provided in the pressure transmitter 5. The chromatographic measurement unit 1, the main charging pipeline 2, the sulfur hexafluoride charging tank 11, the nitrogen tank 12, the first branch pipe 8 and the second branch pipe 9 are arranged on a workbench with wheels at the bottom of the same work area.

[0040] As Figure 2 , it further includes an industrial control computer 10 that can collect the measurement data of the pressure transmitter 5, each flow controller and the chromatographic measurement unit 1, and control the opening and closing of each solenoid valve. The industrial control computer 10 is connected to the pressure transmitter 5 and each flow controller through a 485 communication network, and the industrial control computer 10 is connected to the chromatographic measurement unit 1 through a 232 communication network.

[0041] As Figure 3 , the chromatographic measurement unit 1 includes a thermal conductivity detector 101 and a chromatographic workstation 102.

[0042] The present invention also provides a control method for an automatic adjustment device for the volume ratio of SF6 switch mixed gas, including the following steps:

[0043] The industrial control computer controls the pressure transmitter 5 to measure the pressure P of the SF6 gas mixture switch chamber 3 before deflation 前 ;

[0044] The industrial control computer controls the opening of solenoid valve III 6, closes the solenoid valves on the first branch pipe 8 and the second branch pipe 9, so that the mixed gas in the SF6 gas mixing switch chamber 3 enters the chromatographic measurement unit 1 through the main charging pipeline 2. At the same time, the industrial control computer collects the gas flow rate Q measured by the flow controller III 7;

[0045] After t time, the industrial control computer controls the closing of solenoid valve III 6, and the pressure transmitter 5 measures the pressure P of the SF6 gas mixing switch chamber 3 after deflation 后 ;

[0046] Measure the mixing ratio concentration N of the mixed gas entering the chromatographic measurement unit 1. After measurement, the mixed gas is emptied through the exhaust port of the chromatographic measurement unit 1;

[0047] Calculate the volume ΔV flowing out of the SF6 gas mixing switch = Q * t; calculate the gas chamber volume of the SF6 gas mixing switch ΔP = P 后 -P 前 , according to the gas chamber volume V and the results measured by the chromatographic measurement unit 1, calculate the volume of gas to be filled. The calculation formula is:

[0048] When N > N0, V1 = K1V(N - N0);

[0049] When N < N0, V2 = K2V(N0 - N);

[0050] Where V1 is the volume of nitrogen gas to be filled when N > N0, V2 is the volume of pure SF6 gas to be filled when N < N0, K1 and K2 are calibration constants, and N0 is the mixing ratio concentration specified in the DL / T1986 - 2019Z standard.

[0051] This device is used to calibrate the mixing ratio in the SF6 gas mixing switch. The device measures the accurate mixing ratio of the SF6 gas mixture through the chromatographic unit 1; measures the volume of gas flowing out of the gas mixing switch through the flow controller III 7; measures the storage gas volume of the gas mixing switch by measuring the pressure change of the gas mixing switch through the pressure transmitter 5; and then fine-tunes the volume ratio of the mixed gas in the SF6 gas mixing switch by controlling the amount of gas filled into the SF6 gas mixing switch.

[0052] This device is used to adjust the volume ratio of the mixed gas in the SF6 gas mixing switch. It is automatically controlled by an industrial control computer to automatically adjust the volume ratio of the mixed gas. The device uses a special chromatographic measurement unit for the mixed gas. The chromatographic measurement unit uses a thermal conductivity detector to detect the gas separated by the chromatographic column and transmits it to the industrial control computer through a chromatographic workstation.

[0053] After measuring the exact volume ratio of the mixed gas, the industrial control computer determines the types of gases that need to be proportioned. For example, if the SF6 is low, the SF6 gas solenoid valve is opened and the N2 (or CF4) gas valve is closed. If the SF6 is high, the SF6 gas solenoid valve is closed and the N2 (or CF4) gas valve is opened.

[0054] To accurately adjust the mixed gas ratio, it is also necessary to know the volume of the SF6 mixed gas switch of the mixed gas. Therefore, a flow controller and a precision pressure transmitter are required. The flow controller controls the flow rate of the SF6 mixed gas switch to exhaust gas. During the process of flushing the device, the pressure change of the SF6 mixed gas switch and the volume of the gas flowing out of the SF6 mixed gas switch are detected within a certain period of time, and thus the pure gas volume of the gas to be filled can be calculated. The specific process is as follows:

[0055] 1. Connect the device to the gas chamber 3 of the SF6 mixed gas switch, lead out the gas of the SF6 mixed gas switch to the device through an adapter, and connect a filter 4 in series in the gas path to prevent dust.

[0056] 2. Turn on the power of the device and measure the pressure P of the SF6 mixed gas switch before gas replenishment 前 , through the 485 control network, set the opening duration and the flow rate of the flow controller. At this time, the solenoid valve 16 and the solenoid valve 19 are closed, start the measurement, the industrial control computer controls the electromagnetic switching valve 6 to open, and uses the gas pressure in the mixed gas switch to realize gas flow. The gas flow flows into the chromatographic measurement unit 1 through the electromagnetic switching valve 6 and the flow controller and is exhausted to realize the flushing of the main gas filling pipeline 2.

[0057] 3. After the flushing is completed, the electromagnetic switching valve 6 is closed, and the exact volume ratio of the mixed gas in the SF6 mixed gas switch is measured through the chromatographic measurement unit 1.

[0058] 4. After the chromatographic measurement is completed, the flow controller in series in the gas path during the process detects the gas flow in real time. After the solenoid valve is opened for a fixed duration, the flow rate is multiplied by the duration to calculate the volume ΔV flowing out of the SF6 mixed gas switch. The electromagnetic switching valve 6 is closed, and the pressure P of the SF6 mixed gas switch is measured 后 , so as to estimate the gas chamber volume of the SF6 mixed gas switch. The estimation formula for the gas chamber volume of the SF6 mixed gas switch is: P is the pressure of the mixed gas switch gas chamber after exhaust, V is the gas chamber volume of the SF6 mixed gas switch, ΔV is the volume of the gas flowing out, and ΔP is the pressure difference of the mixed gas switch gas chamber before and after gas release.

[0059] The derivation of the V calculation formula is as follows:

[0060] Let the volume of the mixed gas chamber to be calibrated be V, the volume of the gas flowing out during exhaust be ΔV, and the flow controller 3 controls the flow rate and duration of the flowing gas. It can be obtained that ΔV = Qt, where Q is the flow rate of the flowing gas and t is the flowing duration;

[0061] Let P be the pressure in the air chamber after exhaust, ΔP be the pressure drop in the air chamber after exhaust, n1 be the number of gas molecules before exhaust, n2 be the number of discharged gas fraction, R be the Boltzmann constant, and T be the absolute temperature of the gas.

[0062] According to the ideal gas law:

[0063] Before exhaust:

[0064] (P + ΔP)(V + ΔV) = n1RT (1)

[0065] After exhaust:

[0066] PV = (n1 - n2)RT (2)

[0067] Expanding equation (1), we get

[0068] (P + ΔP)(V + ΔV) = PV + PΔV + ΔPV + ΔPΔV = n1RT

[0069] PV = n1RT - n2RT

[0070] Therefore, we have

[0071] PΔV + ΔPV + ΔPΔV = n2RT (3)

[0072] For the discharged gas, according to the ideal gas law, we have

[0073] ΔPΔV = n2RT (4)

[0074] Combining equations (3) and (4), we get

[0075] PΔV + ΔPV = 0

[0076] Considering that ΔP represents the pressure drop, taking the negative sign, the calculation formula is: V = PΔV / ΔP.

[0077] 5. Determine the gas to be filled by chromatographic measurement and calculate the volume of the gas to be filled. The calculation formula is as follows:

[0078] V1 = K1V(N - N0) (fill pure N2 gas when N > N0)

[0079] V2 = K2V(N0 - N) (fill pure SF6 gas when N < N0)

[0080] Among them, V1 is the dilution gas to be filled when the SF6 concentration exceeds the specified value, and V2 is the volume of pure SF6 gas to be filled when the SF6 concentration is lower than the specified value. K1 and K2 are calibration constants, N is the gas mixing ratio concentration measured by chromatography in the gas chamber, and N0 is the gas mixing ratio concentration specified in the DL / T1986-2019Z standard.

[0081] The amount of gas to be filled for calibrating the purity is proportional to the volume of the gas chamber and the purity difference.

[0082] Then, set the flow rates of flow controller one or two according to the calculation results, and turn on solenoid valve one or two. By setting the required filling duration, fill the gas into the SF6 gas mixing switch.

[0083] The adjustment range of the flow controllers on the first branch pipe 8 and the second branch pipe 9 is selected as a precision flow controller with 0-10 L / min (pressure-bearing flow), and the working pressure is about 0.6 Mpa.

[0084] Considering that the air pump will affect the control accuracy during the process, an air pump is not used in the device. The flow rate is controlled by solenoid valves, and the gas flow in the gas path is realized through the pressure of the SF6 gas mixing switch and the gas cylinders. When purging the device and measuring the purity, solenoid valve one and solenoid valve two are closed, electromagnetic switching valve 6 is opened, and the gas in the gas mixing switch flows through flow controller three 7 and then is discharged. Through the pressure in the gas mixing switch and the flow rate control of the flow controller, quantitative gas flow can be achieved.

[0085] When adjusting the gas mixing ratio, electromagnetic switching valve 6 is closed, and solenoid valve one or solenoid valve two is opened. Since the gas pressure in the steel cylinder is greater than the pressure of the SF6 gas mixing switch, through the pressure difference, a calculated quantity of pure SF6 gas (when the SF6 purity in the gas mixing switch is low) or pure N2 (when the SF6 purity in the gas mixing switch is high) can be filled into the gas mixing switch through flow controller one or solenoid valve two.

Claims

1. An automatic adjusting device for the volume ratio of the mixed gas of SF6 switch, characterized in that: Comprising: A chromatographic measurement unit (1) for measuring the proportion of each component in the mixed gas; A main charging pipeline (2) connected between the SF6 mixed gas switch gas chamber (3) and the chromatographic measurement unit (1). An electromagnetic switching valve (6) and a flow controller III (7) for controlling the flow rate are provided on the main charging pipeline (2). A pressure transmitter (5) is provided at one end of the main charging pipeline (2) close to the SF6 mixed gas switch gas chamber (3), and the pressure transmitter (5) is used to measure the pressure change in the SF6 mixed gas switch gas chamber (3) before and after deflation; A first branch pipe (8) connected to the sulfur hexafluoride filling tank (11) for filling sulfur hexafluoride and a second branch pipe (9) connected to the nitrogen tank (12) for filling nitrogen. The other ends of the first branch pipe (8) and the second branch pipe (9) are connected and then connected to one port of the electromagnetic switching valve (6). Pressure reducing valves, flow controllers and solenoid valves are sequentially provided on the first branch pipe (8) and the second branch pipe (9); It further includes an industrial control computer (10) that can collect the measurement data of the pressure transmitter (5), each flow controller and the chromatographic measurement unit (1), and control the opening and closing of each solenoid valve.

2. The automatic adjusting device for the volume ratio of the SF6 switch hybrid gas according to claim 1, characterized in that: Conversion joints for docking with the SF6 mixed gas switch gas chamber (3) and the chromatographic measurement unit (1) are provided at both ends of the main charging pipeline (2).

3. An automatic adjusting device for the volume ratio of the SF6 switch hybrid gas according to claim 1, characterized in that: A filter (4) is provided at one end of the main charging pipeline (2) close to the SF6 mixed gas switch gas chamber (3).

4. The automatic adjustment device for the volume ratio of the SF6 switch hybrid gas according to claim 1, characterized in that: The industrial control computer (10) is connected to the pressure transmitter (5) and each flow controller through a 458 communication network, and the industrial control computer (10) is connected to the chromatographic measurement unit (1) through a 232 communication network.

5. An automatic adjustment device for the volume ratio of the SF6 switch hybrid gas according to claim 1, characterized in that: The chromatographic measurement unit (1) includes a thermal conductivity detector (101) and a chromatographic workstation (102).

6. The automatic adjustment device for the volume ratio accuracy of the mixed gas of a portable SF6 switch according to claim 1, characterized in that: The chromatographic measurement unit (1), the main charging pipeline (2), the sulfur hexafluoride filling tank (11), the nitrogen tank (12), the first branch pipe (8) and the second branch pipe (9) are arranged on a workbench with wheels at the bottom of the same work area.

7. The automatic adjustment device for the volume ratio accuracy of the mixed gas of the portable SF6 switch according to claim 1, characterized in that: It further includes a temperature sensor (20) for collecting the current gas temperature.

8. The control method of the SF6 switch hybrid gas volume ratio automatic adjustment device according to any one of claims 1-7, characterized in that: Including the following steps: An industrial control computer controls a pressure transmitter (5) to measure the pressure P of the SF6 gas mixing switch gas chamber (3) before gas release 前 ; The industrial control computer controls the electromagnetic switching valve (6) to conduct the main charging pipeline (2), and closes the solenoid valves on the first branch pipe (8) and the second branch pipe (9). The mixed gas in the SF6 mixed gas switch gas chamber (3) enters the chromatographic measurement unit (1) through the main charging pipeline (2). At the same time, the industrial control computer collects the gas flow rate Q measured by the flow controller III (7); After time t, the industrial control computer controls the electromagnetic switching valve (6) to close, and the pressure transmitter (5) measures the pressure P of the SF6 gas mixture switch gas chamber (3) after gas release. 后 ; Measure the mixed gas ratio concentration N of the mixed gas entering the chromatographic measurement unit (1), and the measured mixed gas is emptied through the exhaust port of the chromatographic measurement unit (1); Calculate the volume ΔV flowing out of the gas chamber of the SF6 gas mixture switch: ΔV = Q * t; calculate the volume of the gas chamber of the SF6 gas mixture switch According to the volume V of the gas chamber and the results measured by the chromatographic measurement unit (1), calculate the volume of gas to be filled 9. The control method of the SF6 switch hybrid gas volume ratio automatic adjustment device according to claim 8, characterized in that: The calculation formula for the volume of gas to be filled is: When N > N0, V1 = K1V(N - N0); When N < N0, V2 = K2V(N0 - N); Where V1 is the volume of nitrogen gas to be filled when N > N0, V2 is the volume of pure SF6 gas to be filled when N < N0, K1 and K2 are calibration constants, and N0 is the mixed gas ratio concentration specified in the DL / T1986 - 2019Z standard.

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