Sulfur hexafluoride gas online monitoring method and system

Abstract

The invention relates to a sulfur hexafluoride gas on-line monitoring method and system, belongs to the technical field of gas monitoring, and aims to solve the problem that due to various reasons such as inconstant gas pressure and temperature, measured gas indexes of an existing on-line monitoring system for gas detection cannot reflect actual indexes of sulfur hexafluoride gas. The method comprises the following steps: controlling to-be-monitored gas at a set temperature and a set pressure intensity, and at least measuring a first gas component index; heating the to-be-monitored gas to a second set temperature, calculating a first pressure value at the second set temperature by using a gas density calculation formula according to a second gas component index measured at the moment, and measuring a second pressure value at the second set temperature through a pressure sensor; the first pressure value and the second pressure value are compared, if the difference value between the first pressure value and the second pressure value is smaller than a preset difference value, the first gas component index serves as the monitoring result of the gas components, it is guaranteed that the index of the measured gas is the actual value of the gas chamber, and real data reference is provided for stable operation of a monitoring system.

Description

Technical Field

[0001] The present invention relates to a method and system for on-line monitoring of sulfur hexafluoride gas, belonging to the technical field of gas monitoring. Background Art

[0002] At present, on-line monitoring systems for sulfur hexafluoride gas at home and abroad basically adopt methods such as installing gas sensors, moisture sensors, etc. at the sampling port position of the gas chamber, and directly measuring various indicators of sulfur hexafluoride gas in the gas chamber by using the sensors. However, due to various reasons such as unstable gas pressure, non-constant temperature, and non-flowing gas in the gas chamber, the measured indicators such as gas moisture value and purity are all the indicators of the measurement points, and cannot actually reflect the actual component indicators of sulfur hexafluoride gas in the gas chamber. If accurate measurement is desired, the sensor needs to be directly inserted into the gas chamber. However, since many gas chambers are retrofitted with sensors later and it is not allowed to insert the sensor into the gas chamber, accurate monitoring of sulfur hexafluoride gas indicators cannot be achieved.

[0003] For the moisture sensor, since the moisture value is the pressure dew point, it has different dew point values under different pressures, and in the state of non-flowing gas, what it measures is the moisture at the measurement point.

[0004] For most gas sensors, they mostly adopt the thermal conductivity principle. The values of each measurement point are not directly measuring physical quantities like pressure and temperature sensors, but calibrating each value with standard gas, and the phenomenon of measurement value drift often occurs. When the on-line monitoring system is used as the basis for the ratio of a sulfur hexafluoride mixed gas system as the reference for gas mixing, if the electronic sensor fails, it is very easy to cause inaccurate gas ratio in the prepared gas. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for on-line monitoring of sulfur hexafluoride gas to solve the problem of how to accurately monitor the actual component indicators of sulfur hexafluoride gas.

[0006] To achieve the above purpose, the solution of the present invention includes:

[0007] An on-line monitoring system for sulfur hexafluoride gas of the present invention includes a buffer tank arranged in a temperature regulating box and a pressure regulating device for regulating the gas pressure in the buffer tank; the buffer tank includes an exhaust branch and an intake branch connected to the gas chamber to be monitored, and valve systems for controlling the on-off of the corresponding gas paths are arranged on both the exhaust branch and the intake branch; it also includes a gas sensor, a moisture sensor, and a pressure sensor for detecting the gas composition, moisture, and pressure in the buffer tank.

[0008] When the present invention is in use, after discharging the gas in the buffer tank through the exhaust branch, the buffer tank is adjusted to the set temperature through the temperature adjustment box. The gas to be monitored in the gas chamber is discharged into the buffer tank through the intake branch and adjusted to the set pressure through the pressure regulating device. Among them, the gas sensor, the moisture sensor and the pressure sensor can detect the gas purity, moisture and pressure in the buffer tank. After heating up the buffer tank, the pressure value of the gas to be monitored is measured and compared with the calculated theoretical pressure value, so as to compare the accuracy of the sensor measurement value. If the difference between the two is less than the set value, the sensor error meets the set requirements, and the index of the gas to be monitored is based on the sensor measurement value.

[0009] Further, an air extraction device for extracting the gas in the buffer tank before measurement is also arranged on the exhaust branch.

[0010] Through the air extraction device, the gas in the buffer tank can be further emptied, making the data measured by the sensor more accurate.

[0011] Further, the valve system on the exhaust branch includes electromagnetic valves arranged on both sides of the air extraction device.

[0012] The electromagnetic valves on both sides of the air extraction prevent the gas from flowing randomly in the buffer tank and the gas path, affecting the accuracy of the measurement data.

[0013] Further, the pressure regulating device is a pressure reducing valve arranged on the intake branch.

[0014] Further, the valve system on the intake branch includes electromagnetic valves arranged on both sides of the pressure reducing valve.

[0015] The electromagnetic valves on both sides of the pressure reducing valve prevent the gas from flowing randomly in the buffer tank and the gas path, affecting the accuracy of the measurement data.

[0016] Further, a thermometer is also included in the buffer tank.

[0017] An on-line monitoring method for sulfur hexafluoride gas of the present invention is characterized in that the gas to be monitored is controlled at a set temperature and a set pressure, and at least the first gas component index is measured; the gas to be monitored is heated to a second set temperature, and according to the second gas component index measured at this time, the first pressure value at the second set temperature is calculated by using the ideal gas state equation, and the second pressure value at the second set temperature is also measured through a pressure sensor; the first pressure value and the second pressure value are compared. If the difference between the two is less than the preset difference, the first gas component index is used as the monitoring result of the gas component.

[0018] By heating the gas to be monitored to the second set temperature and comparing the calculated first pressure value with the second pressure value measured by the pressure sensor, if the difference between the two values is less than the preset difference, the first component index measured by the sensor at the set temperature is relatively accurate and can be used as the monitoring result of the gas component.

[0019] Furthermore, if the difference between the first pressure value and the second pressure value is greater than the preset difference, the result measured by the physical measurement method at the set temperature is used as the monitoring result.

[0020] If the difference between the first pressure value and the second pressure value is greater than the preset difference, there is a certain error between the first component index measured by the sensor at the set temperature and the actual value, and it cannot be used as the monitoring result of the gas component. The actual monitoring result is based on the physical measurement result.

[0021] Furthermore, the gas to be monitored is controlled at the set temperature through the following steps: empty the buffer tank, adjust the temperature control box where it is located to the set temperature, and introduce the gas to be monitored into the buffer tank for detection.

[0022] By emptying the gas in the buffer tank, the data measured by the sensor is further made more accurate.

[0023] Furthermore, the corresponding gas density is obtained according to the second gas component index, and the density is substituted into the gas density equation obtained from the ideal gas state equation to calculate the first pressure value. Description of the Drawings

[0024] Figure 1 It is the schematic diagram of an on-line monitoring system for sulfur hexafluoride gas in this embodiment. Detailed Implementation Modes

[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0026] An embodiment of an on-line monitoring system for sulfur hexafluoride gas:

[0027] Such as Figure 1An online monitoring system for sulfur hexafluoride gas is shown. The system includes a buffer tank S, a solenoid valve DV3, a compressor comp, a solenoid valve DV4, a gas chamber, a pressure reducing valve REV, a solenoid valve DV1, and a solenoid valve DV2. The buffer tank S is arranged in a temperature regulating box, and there are also a gas sensor M for measuring the gas in the buffer tank (which can measure multiple indicators such as gas purity and decomposition products according to functional requirements), a moisture sensor Dp, a thermometer T, and a pressure sensor PT. The buffer tank S also includes an exhaust branch and an intake branch for connecting to the gas chamber. The exhaust branch includes the solenoid valve DV3, the compressor comp, and the solenoid valve DV4 connected in sequence, and the intake branch includes the solenoid valve DV1, the pressure reducing valve REV, and the solenoid valve DV2 connected in sequence.

[0028] When this embodiment is used, first open the solenoid valves DV4 and DV3, and use the compressor comp to evacuate the gas in the buffer tank S into the gas chamber, and then close the solenoid valves DV4, DV3, and the compressor comp. Adjust the buffer tank S to a constant temperature of 20 °C through the temperature regulating box, open DV1, DV2, and the pressure reducing valve REV, so that the gas to be monitored in the gas chamber enters the buffer tank S after the pressure is increased to the set value P1 through the pressure reducing valve REV. At this time, the buffer tank S is a small constant-volume gas chamber with a temperature of 20 °C and a pressure of P1. Subsequently, close DV1, DV2, and the pressure reducing valve REV.

[0029] Use the gas sensor M and the moisture sensor Dp to measure the composition index and moisture index of the gas to be monitored. After the sensor measurement is completed, the temperature regulating box raises the gas to be monitored in the buffer tank S to the set temperature t1. At this time, according to the purity index of the measured gas, the corresponding gas density is obtained, and the density is substituted into the gas density equation obtained from the ideal gas state equation to calculate its calculated pressure value P2 at t1. The pressure value P3 read by the pressure sensor for the gas to be monitored in the buffer tank at the temperature of t1 is compared with the difference between P3 and P2. If the difference between the pressure value P3 and the pressure value P2 is less than the set value, the detection result of the gas to be monitored is the index measured by the sensor when the set temperature in the buffer tank is 20 °C. If the difference between the two is greater than the set value, the detection result of the gas to be monitored is the index measured by the physical measurement method when the set temperature in the buffer tank is 20 °C. The physical measurement method can obtain its density by pumping out the gas to be monitored and then using an experimental method or obtaining its density through the pressure value measured by the pressure sensor, and then obtaining the gas purity index. It can also obtain the gas density through other means. Through this system, the accuracy of the measurement value of the gas sensor can be compared. If the purity index does not meet the temperature and pressure change curve, the system gives an alarm prompt.

[0030] Among them, the ideal gas state equation is

[0031] PV = nRT

[0032] Where P is the pressure, V is the volume, n is the number of moles, R is a constant, and T is the temperature; where n = M÷Mmol, where M is the mass and Mmol is the molar mass; then we can get

[0033] PV = MRT÷Mmol

[0034] And the density ρ = M÷V, so P = ρRT÷Mmol. Therefore, the pressure P2 at temperature t1 can be calculated by the density obtained by measuring the purity index of the gas.

[0035] It should be noted that this system is applicable not only to sulfur hexafluoride gas, but also to SF6 / N2 mixed gas and other gases for which the density formula can be calculated.

[0036] It should also be noted that the selection of pressure reducing valve, compressor, etc. in this embodiment is only one implementation method, and it is not limited to using other specific implementation methods to process the gas.

[0037] An embodiment of an on-line monitoring method for sulfur hexafluoride gas:

[0038] This embodiment is based on an on-line monitoring system for sulfur hexafluoride gas. An on-line monitoring system for sulfur hexafluoride gas has been introduced in detail in the above-mentioned embodiment of the on-line monitoring system for sulfur hexafluoride gas, and will not be elaborated here. In this method embodiment, first, the gas in the buffer tank S is emptied, and then the temperature in the buffer tank S is set to 20°C by using a temperature regulating box; the pressure of the gas to be monitored in the gas chamber is increased to P1 by a pressure reducing valve REV and discharged into the buffer tank S at a temperature of 20°C, and the component index and moisture index of the gas to be monitored at a temperature of 20°C and a pressure of P1 are measured by using a gas sensor M and a moisture sensor Dp.

[0039] After the sensor measurement is completed, the temperature of the buffer tank is raised again to the set temperature t1 by using the temperature regulating box. According to the gas purity index measured by the gas sensor, the density of the gas to be monitored can be obtained, and the density is substituted into the gas density equation obtained from the ideal gas state equation to calculate the pressure value at the set temperature t1; read the measured value P3 of the pressure sensor at temperature t1, and judge the difference between the theoretically calculated pressure value P2 and the measured value P3 of the sensor. When the difference is less than the set value, the detection result of the gas to be monitored is the index measured by the sensor at a temperature of 20°C in the buffer tank. If the difference between the theoretically calculated pressure value P2 and the measured value P3 of the sensor is greater than the set value, the detection result of the gas to be monitored is the index measured by the physical measurement method at a temperature of 20°C. The physical measurement method can obtain its density by pumping out the gas to be monitored and then using an experiment or obtaining its density from the pressure value measured by the pressure sensor, and then obtaining the gas purity index, or it can also obtain the gas density by other means.

[0040] Among them, the ideal gas state equation is

[0041] PV = nRT

[0042] In the formula, P is the pressure, V is the volume, n is the number of moles, R is a constant, and T is the temperature; among them, n = M÷Mmol, where M is the mass and Mmol is the molar mass; then we can get

[0043] PV = MRT÷Mmol

[0044] And the density ρ = M÷V, so P = ρRT÷Mmol. Therefore, the pressure P2 at temperature t1 can be deduced from the density obtained by measuring the purity index of the gas.

[0045] It should be noted that this method is applicable to all gases for which the density formula can be calculated.

Claims

1. An on-line monitoring system for sulfur hexafluoride gas, characterized in that, It includes a buffer tank disposed inside a temperature control box and a pressure regulating device for regulating the gas pressure inside the buffer tank; the buffer tank includes an exhaust branch and an intake branch connected to the gas chamber to be monitored, and valve systems for controlling the on / off of the corresponding gas paths are provided on both the exhaust branch and the intake branch; it also includes a gas sensor, a moisture sensor, and a pressure sensor for detecting the gas composition, moisture, and pressure inside the buffer tank.

2. The sulfur hexafluoride gas on-line monitoring system according to claim 1, wherein An air extraction device for extracting the gas inside the buffer tank before measurement is further provided on the exhaust branch.

3. The sulfur hexafluoride gas on-line monitoring system according to claim 2, characterized in that, The valve system on the exhaust branch includes solenoid valves provided on both sides of the air extraction device.

4. The sulfur hexafluoride gas on-line monitoring system according to claim 1, wherein The pressure regulating device is a pressure reducing valve provided on the intake branch.

5. The sulfur hexafluoride gas on-line monitoring system according to claim 4, characterized in that, The valve system on the intake branch includes solenoid valves provided on both sides of the pressure reducing valve.

6. The sulfur hexafluoride gas on-line monitoring system according to claim 1, wherein, A thermometer is further included inside the buffer tank.

7. An on-line monitoring method for sulfur hexafluoride gas, characterized in that, The gas to be monitored is controlled at a set temperature and a set pressure, and at least the first gas composition index is measured; the gas to be monitored is heated to a second set temperature, and according to the second gas composition index measured at this time, the first pressure value at the second set temperature is calculated using the ideal gas state equation, and the second pressure value at the second set temperature is also measured by the pressure sensor; the first pressure value and the second pressure value are compared, and if the difference between the two is less than a preset difference, the first gas composition index is used as the monitoring result of the gas composition.

8. The on-line monitoring method for sulfur hexafluoride gas according to claim 7, characterized in that, If the difference between the first pressure value and the second pressure value is greater than the preset difference, the result measured by the physical measurement method at the set temperature is used as the monitoring result.

9. The online monitoring method for sulfur hexafluoride gas according to claim 7, characterized in that The gas to be monitored is controlled at the set temperature through the following steps: the buffer tank is emptied, the temperature control box where it is located is adjusted to the set temperature, and the gas to be monitored is introduced into the buffer tank for detection.

10. The on-line monitoring method for sulfur hexafluoride gas according to claim 7, characterized in that, The corresponding gas density is obtained according to the second gas composition index, and the density is substituted into the gas density equation obtained from the ideal gas state equation to calculate the first pressure value.

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