Sulfur hexafluoride gas density and micro-water content on-line monitoring circuit and sulfur hexafluoride gas density and micro-water content on-line monitoring device

Abstract

The invention discloses a sulfur hexafluoride gas density and micro-water content on-line monitoring circuit and device, and relates to the technical field of sulfur hexafluoride gas monitoring, and the circuit comprises a first antenna, a double-parameter sensing module and a single-parameter sensing module; the double-parameter sensing module and the single-parameter sensing module are connected with the first antenna. Compared with a traditional sulfur hexafluoride gas leakage monitoring mode adopting a pressure gauge or a density relay, the sulfur hexafluoride gas leakage monitoring device collects temperature data in real time while collecting the pressure of the sulfur hexafluoride gas, the influence of the temperature on the pressure can be compensated, and the monitoring precision and reliability of the density and the micro-water content of the sulfur hexafluoride gas are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sulfur hexafluoride gas monitoring, and in particular to an online monitoring circuit and device for sulfur hexafluoride gas density and trace water content. Background Art

[0002] The function of sulfur hexafluoride (SF6) gas in high-voltage electrical equipment is arc extinguishing and insulation. A decrease in the density of sulfur hexafluoride gas or an excess of trace water (referred to as micro-water) in high-voltage electrical equipment will seriously affect the safe operation of sulfur hexafluoride high-voltage electrical equipment.

[0003] When sulfur hexafluoride (SF6) electrical equipment is in operation, it's inevitable that SF6 gas will leak out, causing its density to drop. Simultaneously, moisture from outside the equipment can seep into the equipment, increasing the water content within the SF6 gas. Excessive water content can pose a safety hazard to high-voltage electrical equipment. Therefore, it's necessary to monitor the density and water content of SF6 gas within SF6 electrical equipment.

[0004] Traditional SF6 gas leak monitoring relies on pressure gauges or density relays, neither of which fully compensates for the effects of temperature on pressure, and their accuracy and reliability are unsatisfactory. Furthermore, the process and equipment required to monitor the moisture content of SF6 gas are complex, and the measurement results do not objectively reflect the moisture content. Offline testing is generally used. Therefore, achieving high-precision online monitoring of SF6 moisture content and density is crucial for ensuring the normal operation of power equipment. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes an online monitoring circuit and device for sulfur hexafluoride gas density and trace water content.

[0006] The technical solution of the present invention is: an online monitoring circuit for sulfur hexafluoride gas density and trace water content includes a first antenna, a dual-parameter sensing module and a single-parameter sensing module; the dual-parameter sensing module and the single-parameter sensing module are both connected to the first antenna;

[0007] The dual-parameter sensing module is used to sense pressure and temperature; the single-parameter sensing module is used to measure relative humidity.

[0008] Furthermore, the dual-parameter sensing module includes a first matching circuit, a first tuning circuit, a pressure sensing circuit, a temperature sensing circuit, a pressure sensing matching circuit, a second antenna, a temperature sensing matching circuit, and a third antenna;

[0009] The first matching circuit, the pressure sensing circuit, the temperature sensing circuit, the pressure sensing matching circuit and the temperature sensing matching circuit are all connected to the first tuning circuit; the second antenna is connected to the pressure sensing matching circuit; the third antenna is connected to the temperature sensing matching circuit; and the first matching circuit is also connected to the first antenna.

[0010] Furthermore, the single parameter sensing module includes a second matching circuit, a second tuning circuit, a humidity sensing circuit, a band-stop reflection circuit, a temperature sensing matching circuit and a fourth antenna;

[0011] The second matching circuit, the humidity sensing circuit, the band-stop reflection circuit and the temperature sensing matching circuit are all connected to the second tuning circuit; the fourth antenna is connected to the temperature sensing matching circuit; and the second matching circuit is also connected to the first antenna.

[0012] Furthermore, the first tuning circuit includes an inductor L2 and a transistor X1; one end of the inductor L2 is connected to the gate of the transistor X1; the other end of the inductor L2 is connected to the first matching circuit; the drain of the transistor X1 is respectively connected to the pressure sensing circuit and the pressure sensing matching circuit; and the source of the transistor X1 is respectively connected to the temperature sensing circuit and the temperature sensing matching circuit.

[0013] Furthermore, the pressure sensing circuit includes a grounding inductor L3 and a grounding capacitor C3; the grounding inductor L3 and the grounding capacitor C3 are both connected to the drain of the transistor X1;

[0014] The pressure sensing matching circuit includes an inductor L4 and a grounded capacitor C4; one end of the inductor L4 is connected to the drain of the transistor X1; the other end of the inductor L4 and the grounded capacitor C4 are both connected to the second antenna A2.

[0015] Furthermore, the temperature sensing circuit includes a grounding inductor L6 and a grounding capacitor C6; the grounding inductor L6 and the grounding capacitor C6 are both connected to the source of the transistor X1;

[0016] The temperature sensing matching circuit includes an inductor L5 and a grounded capacitor C5 ; one end of the inductor L5 is connected to the source of the transistor X1 ; the other end of the inductor L5 and the grounded capacitor C5 are both connected to the third antenna A3 .

[0017] Furthermore, the second tuning circuit includes an inductor L8 and a transistor X2; one end of the inductor L8 is connected to the gate of the transistor X2; the other end of the inductor L8 is connected to the second matching circuit; and the drain of the transistor X2 is respectively connected to the humidity sensing circuit and the humidity sensing matching circuit.

[0018] Furthermore, the humidity sensing circuit includes a grounding inductor L9 and a grounding capacitor C9; the grounding inductor L9 and the grounding capacitor C9 are both connected to the drain of the transistor X2;

[0019] The humidity sensor matching circuit includes an inductor L10 and a grounded capacitor C10; one end of the inductor L10 is connected to the drain of the transistor X2; the other end of the inductor L10 and the grounded capacitor C10 are both connected to the fourth antenna A4.

[0020] Furthermore, the band-stop reflection circuit adopts a radio frequency open line.

[0021] Based on the above circuit, the present invention further proposes an online monitoring device for sulfur hexafluoride gas density and trace water content, which includes the online monitoring circuit for sulfur hexafluoride gas density and trace water content as described above.

[0022] The beneficial effects of the present invention are:

[0023] (1) Compared with the traditional SF6 gas leakage monitoring method using a pressure gauge or density relay, the present invention collects temperature data in real time while collecting SF6 gas pressure, which can compensate for the effect of temperature on pressure and improve the monitoring accuracy and reliability of SF6 gas density and trace water content;

[0024] (2) Compared with the traditional method of monitoring the micro-water content of sulfur hexafluoride gas in an offline manner, the present invention has a simple structure design, and humidity, temperature and pressure are collected simultaneously. The obtained micro-water content value can be corrected in real time to ensure the accuracy of online monitoring;

[0025] (3) The present invention uses passive wireless communication to perform online monitoring of the density and water content of sulfur hexafluoride gas in high-voltage electrical equipment. It is inherently safe and does not require battery replacement or wiring. It does not require complex wiring and sealed interface design, is simple and convenient to use, and has low subsequent maintenance costs.

[0026] (4) The present invention adopts a different frequency transmission system for uplink and downlink signals (i.e., the mixed signal carrying pressure, temperature, and humidity sensing information has a different frequency from the downlink carrier signal), which can reduce the same-frequency blocking problem of the remote transceiver, thereby indirectly improving the sensitivity of the transceiver in receiving uplink signals and extending the wireless working distance;

[0027] (5) The present invention does not require complex wiring and sealing interface design, is simple and convenient to use, and has low subsequent maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of the online monitoring circuit for sulfur hexafluoride gas density and trace water content;

[0029] Figure 2 This is a circuit diagram of an online monitoring circuit for sulfur hexafluoride gas density and trace water content;

[0030] Figure 3A schematic structural diagram of a first multiplexing design for a first matching circuit and a second matching circuit;

[0031] Figure 4 A schematic structural diagram of a second multiplexing design for the first matching circuit and the second matching circuit;

[0032] Figure 5 A schematic structural diagram of a third multiplexing design for the first matching circuit and the second matching circuit; DETAILED DESCRIPTION

[0033] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the present invention provides an online monitoring circuit for sulfur hexafluoride gas density and trace water content, comprising a first antenna, a dual-parameter sensing module and a single-parameter sensing module; the dual-parameter sensing module and the single-parameter sensing module are both connected to the first antenna;

[0035] The dual-parameter sensing module is used to sense pressure and temperature; the single-parameter sensing module is used to measure relative humidity.

[0036] After the high-voltage equipment chamber is filled with SF6 gas, the density of SF6 gas is often used to determine whether it has met the insulation requirements. Direct density monitoring is difficult to achieve, and is usually converted into pressure monitoring. However, the pressure of SF6 gas will change with temperature. Therefore, in order to accurately reflect whether the pressure change is caused by leakage or temperature change, a temperature compensation correction method is required. Regardless of the external temperature, the standard pressure corresponding to 20°C can always be calculated. Therefore, the SF6 gas density online monitoring system needs to collect two characteristic quantities, temperature and pressure, and process the two characteristic quantities. Furthermore, in Figure 1 In this embodiment, the pressure and temperature sensing circuits are electrically connected to the first tuning circuit at the same time, thereby further reducing the test error caused by the system. In other words, the dual-parameter sensing module is used to sense pressure and temperature and shares the same first tuning circuit.

[0037] In the embodiment of the present invention, Figure 1 As shown, the dual-parameter sensing module includes a first matching circuit, a first tuning circuit, a pressure sensing circuit, a temperature sensing circuit, a pressure sensing matching circuit, a second antenna, a temperature sensing matching circuit and a third antenna;

[0038] The first matching circuit, the pressure sensing circuit, the temperature sensing circuit, the pressure sensing matching circuit and the temperature sensing matching circuit are all connected to the first tuning circuit; the second antenna is connected to the pressure sensing matching circuit; the third antenna is connected to the temperature sensing matching circuit; and the first matching circuit is also connected to the first antenna.

[0039] In the embodiment of the present invention, Figure 1 As shown, the single parameter sensing module includes a second matching circuit, a second tuning circuit, a humidity sensing circuit, a band-stop reflection circuit, a temperature sensing matching circuit and a fourth antenna;

[0040] The second matching circuit, the humidity sensing circuit, the band-stop reflection circuit and the temperature sensing matching circuit are all connected to the second tuning circuit; the fourth antenna is connected to the temperature sensing matching circuit; and the second matching circuit is also connected to the first antenna.

[0041] In the embodiment of the present invention, Figure 2 As shown, the first tuning circuit includes an inductor L2 and a transistor X1; one end of the inductor L2 is connected to the gate of the transistor X1; the other end of the inductor L2 is connected to the first matching circuit; the drain of the transistor X1 is respectively connected to the pressure sensing circuit and the pressure sensing matching circuit; and the source of the transistor X1 is respectively connected to the temperature sensing circuit and the temperature sensing matching circuit.

[0042] The first antenna A1 is used to receive the downlink carrier signal transmitted from the remote end. The downlink carrier signal reaches the first tuning circuit through the first matching circuit (inductor L1 and capacitor C1). By utilizing the characteristic that the capacitance of the internal junction capacitance of transistor X1 changes with the voltage applied across it, combined with inductor L2, two time-varying tuning signals are generated at the source and drain of transistor X1. These signals contain a rich spectrum. The resonant frequency of the pressure sensing circuit electrically connected to the source is f D1 , the resonant frequency of the temperature sensing circuit electrically connected to the drain is f S1 In the time-varying tuned signal, the high-frequency signal will go from the capacitor to the ground, and the low-frequency signal will go from the inductor to the ground, which is consistent with the resonant frequency f D1 and f S1 Signals within a certain bandwidth will be retained in the circuit. D1 Take this as an example, the resonant frequency is f D1 The signal will return to transistor X1. According to the nonlinear characteristics of the transistor, gain amplification and the Menley-Lowe formula, the resonant frequency is f D1 The signal will be mixed with the downlink carrier signal with a frequency of f0 and amplified to generate a mixing frequency signal f pre =f0±n*f D1 , where n is a positive integer representing the harmonic order, usually the first order, that is, n=1. Similarly, for a resonant frequency of f S1 , can generate the mixing frequency signal f temp =f0±n*f S1 .

[0043] In the embodiment of the present invention, Figure 2As shown, the pressure sensing circuit includes a grounded inductor L3 and a grounded capacitor C3; both the grounded inductor L3 and the grounded capacitor C3 are connected to the drain of the transistor X1; the present invention adopts a capacitive pressure-sensitive element as the sulfur hexafluoride gas pressure sensing element, represented by the capacitor C3.

[0044] The pressure sensing matching circuit includes an inductor L4 and a grounded capacitor C4; one end of the inductor L4 is connected to the drain of the transistor X1; the other end of the inductor L4 and the grounded capacitor C4 are both connected to the second antenna A2.

[0045] In the embodiment of the present invention, Figure 2 As shown, the temperature sensing circuit includes a grounded inductor L6 and a grounded capacitor C6; both the grounded inductor L6 and the grounded capacitor C6 are connected to the source of the transistor X1; the temperature sensing circuit adopts an LC parallel resonant network and a capacitive temperature sensitive element as the sulfur hexafluoride gas temperature sensing element, represented by capacitor C6.

[0046] The temperature sensing matching circuit includes an inductor L5 and a grounded capacitor C5 ; one end of the inductor L5 is connected to the source of the transistor X1 ; the other end of the inductor L5 and the grounded capacitor C5 are both connected to the third antenna A3 .

[0047] The pressure sensor matching circuit is used to match the mixing frequency signal f pre Impedance matching, other RF signals in the circuit (such as downlink carrier signal f0, resonant frequency signal f D1 , resonant frequency signal f S1 and the mixing frequency signal f temp ) are both in high impedance state, that is, the mixing frequency signal f pre The temperature sensor matching circuit is used to output the mixed frequency signal f temp Impedance matching, other RF signals in the circuit (such as downlink carrier signal f0, resonant frequency signal f D1 , resonant frequency signal f S1 and the mixing frequency signal f pre ) are both in high impedance state, that is, the mixing frequency signal f temp The temperature sensing matching circuit will output the signal from the third antenna.

[0048] In the embodiment of the present invention, Figure 2 As shown, the second tuning circuit includes an inductor L8 and a transistor X2; one end of the inductor L8 is connected to the gate of the transistor X2; the other end of the inductor L8 is connected to the second matching circuit; and the drain of the transistor X2 is connected to the humidity sensing circuit and the humidity sensing matching circuit respectively.

[0049] In the embodiment of the present invention, Figure 2As shown, the humidity sensing circuit includes a grounding inductor L9 and a grounding capacitor C9; both the grounding inductor L9 and the grounding capacitor C9 are connected to the drain of the transistor X2; the present invention adopts a capacitive humidity sensor as the sulfur hexafluoride gas humidity sensing element, represented by the capacitor C9.

[0050] The humidity sensor matching circuit includes an inductor L10 and a grounded capacitor C10; one end of the inductor L10 is connected to the drain of the transistor X2; the other end of the inductor L10 and the grounded capacitor C10 are both connected to the fourth antenna A4.

[0051] The resonant frequency of the humidity sensing circuit electrically connected to the drain is f D2 In the time-varying tuned signal, the high-frequency signal will go from the capacitor to the ground, and the low-frequency signal will go from the inductor to the ground, which is consistent with the resonant frequency f D2 Signals within a certain bandwidth will remain in the circuit. The resonant frequency is f D2 The signal will return to transistor X2. According to the nonlinear characteristics of the transistor, gain amplification and the Menley-Lowe formula, the resonant frequency is f D2 The signal will be mixed with the downlink carrier signal with a frequency of f0 and amplified to generate a mixing frequency signal f hum =f0±n*f D2 , where n is a positive integer, representing the harmonic order, usually the first order, that is, n=1. The humidity sensor matching circuit is used to adjust the mixing frequency signal f hum Impedance matching is used to match other RF signals in the circuit (such as the downlink carrier signal f0 and the resonant frequency signal f D2 ) are both in high impedance state, that is, the mixing frequency signal f hum The humidity sensor matching circuit will be output from the fourth antenna.

[0052] In this embodiment of the present invention, the peripheral connection circuits for the drain and source of the transistors are interchangeable. For example, for a dual-parameter sensing module, the pressure sensing circuit and pressure sensing matching circuit are electrically connected to the source of transistor one X1, and the temperature sensing circuit and temperature sensing matching circuit are electrically connected to the drain of transistor one X1. For a single-parameter sensing module, the humidity sensing circuit and humidity sensing matching circuit are electrically connected to the source of transistor two X2, and the band-stop reflection circuit is electrically connected to the drain of transistor two X2.

[0053] In the embodiment of the present invention, the band-stop reflection circuit adopts a radio frequency open line.

[0054] Based on the above circuit, the present invention further proposes an online monitoring device for sulfur hexafluoride gas density and trace water content, which includes the online monitoring circuit for sulfur hexafluoride gas density and trace water content as described above.

[0055] In the embodiment of the present invention, a method for calculating the water content of sulfur hexafluoride gas is introduced:

[0056] Online monitoring of the moisture content of sulfur hexafluoride gas requires the use of three characteristic quantities: relative humidity, temperature, and pressure. Therefore, in addition to the aforementioned dual-parameter sensor module, a single-parameter sensor module for measuring relative humidity is also required. Typically, industrial sites use the temperature value of SF6 gas at 20°C as a reference standard. Therefore, in order to make the measurement results comparable, a correction formula is needed to correct the measured relative humidity value so that it can be compared with the reference value. The correction calculation process includes the following steps:

[0057] S1. Calculate real-time trace water saturation pressure ;

[0058] S2. Calculate the real-time water content of sulfur hexafluoride gas based on the real-time trace water saturation pressure;

[0059] S3. Correct the real-time water content of the sulfur hexafluoride gas to obtain the trace water content at 20°C.

[0060] In S1, the real-time trace water saturation pressure of the pure horizontal liquid surface The calculation formula is:

[0061] ;

[0062] Where, represents the logarithmic function, It represents the thermodynamic temperature of air in K.

[0063] Real-time trace water saturation pressure of pure horizontal ice surface in S1 The calculation formula is:

[0064] ;

[0065] S2, real-time water content of sulfur hexafluoride gas The calculation formula is:

[0066] ;

[0067] Where, The unit is μL / L, Indicates the real-time pressure of sulfur hexafluoride gas.

[0068] In S3, the trace water content at 20℃ The calculation formula is:

[0069] ;

[0070] Where, Indicates the sulfur hexafluoride gas pressure at 20°C, Indicates the trace water saturation pressure at 20°C, in MPa.

[0071] exist Figure 1 and Figure 2 In the embodiment, the three mixed frequency signals representing pressure, temperature, and humidity are coupled and output from the drain and source of the transistor respectively, so there are four antennas. The advantage of such a configuration is that the design requirements for the first matching circuit and the second matching circuit are relatively low, and through the independent pressure sensing matching circuit, temperature sensing matching circuit, and humidity sensing matching circuit, the frequency purity of the output signal can be significantly improved, the spectrum distortion caused by nonlinear effects can be reduced, and the stability and consistency of the mixed signal can be ensured. The disadvantage is that the number of antennas and matching circuits is large and the material cost is high. In fact, the number of antennas and matching circuits can be reduced by multiplexing the first matching circuit and the second matching circuit.

[0072] like Figure 3 As shown, Figure 1 The difference is that the mixed frequency signal representing humidity is output through the second matching circuit and the first antenna. Figure 3 In the embodiment, the second matching circuit has high-efficiency and low-loss matching transmission for at least the downlink carrier signal and the humidity mixing signal.

[0073] like Figure 4 As shown, Figure 3 The difference is that the mixed frequency signal representing the temperature is output through the first matching circuit and the first antenna. Figure 4 In the embodiment, the first matching circuit has high-efficiency and low-loss matching transmission for at least the downlink carrier signal and the temperature mixing signal, and is in a high-impedance state for at least the pressure mixing signal.

[0074] like Figure 5 As shown, Figure 3 The difference is that the mixed frequency signal representing the pressure is output through the first matching circuit and the first antenna. Figure 5 In the embodiment, the first matching circuit has high-efficiency and low-loss matching transmission for at least the downlink carrier signal and the pressure mixing signal, and is in a high-impedance state for at least the temperature mixing signal.

[0075] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. An online monitoring circuit for sulfur hexafluoride gas density and trace water content, characterized in that: It includes a first antenna, a dual-parameter sensing module and a single-parameter sensing module; the dual-parameter sensing module and the single-parameter sensing module are both connected to the first antenna; The dual-parameter sensing module is used to sense pressure and temperature; the single-parameter sensing module is used to measure relative humidity.

2. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 1, characterized in that: The dual-parameter sensing module includes a first matching circuit, a first tuning circuit, a pressure sensing circuit, a temperature sensing circuit, a pressure sensing matching circuit, a second antenna, a temperature sensing matching circuit and a third antenna; The first matching circuit, pressure sensing circuit, temperature sensing circuit, pressure sensing matching circuit and temperature sensing matching circuit are all connected to the first tuning circuit; the second antenna is connected to the pressure sensing matching circuit; the third antenna is connected to the temperature sensing matching circuit; and the first matching circuit is also connected to the first antenna.

3. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 1, characterized in that: The single parameter sensing module includes a second matching circuit, a second tuning circuit, a humidity sensing circuit, a band-stop reflection circuit, a temperature sensing matching circuit and a fourth antenna; The second matching circuit, humidity sensing circuit, band-stop reflection circuit and temperature sensing matching circuit are all connected to the second tuning circuit; the fourth antenna is connected to the temperature sensing matching circuit; and the second matching circuit is also connected to the first antenna.

4. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 2, characterized in that: The first tuning circuit includes an inductor L2 and a transistor X1; one end of the inductor L2 is connected to the gate of the transistor X1; the other end of the inductor L2 is connected to the first matching circuit; the drain of the transistor X1 is respectively connected to the pressure sensing circuit and the pressure sensing matching circuit; and the source of the transistor X1 is respectively connected to the temperature sensing circuit and the temperature sensing matching circuit.

5. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 4, characterized in that: The pressure sensing circuit includes a grounding inductor L3 and a grounding capacitor C3; the grounding inductor L3 and the grounding capacitor C3 are both connected to the drain of the transistor X1; The pressure sensing matching circuit includes an inductor L4 and a grounded capacitor C4; one end of the inductor L4 is connected to the drain of the transistor X1; the other end of the inductor L4 and the grounded capacitor C4 are both connected to the second antenna A2.

6. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 4, characterized in that: The temperature sensing circuit includes a grounding inductor L6 and a grounding capacitor C6; the grounding inductor L6 and the grounding capacitor C6 are both connected to the source of the transistor X1; The temperature sensing matching circuit includes an inductor L5 and a grounded capacitor C5; one end of the inductor L5 is connected to the source of the transistor X1; the other end of the inductor L5 and the grounded capacitor C5 are both connected to the third antenna A3.

7. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 3, characterized in that: The second tuning circuit includes an inductor L8 and a transistor X2; one end of the inductor L8 is connected to the gate of the transistor X2; the other end of the inductor L8 is connected to the second matching circuit; the drain of the transistor X2 is respectively connected to the humidity sensing circuit and the humidity sensing matching circuit.

8. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 7, characterized in that: The humidity sensing circuit includes a grounding inductor L9 and a grounding capacitor C9; the grounding inductor L9 and the grounding capacitor C9 are both connected to the drain of the transistor X2; The humidity sensor matching circuit includes an inductor L10 and a grounded capacitor C10; one end of the inductor L10 is connected to the drain of the transistor X2; the other end of the inductor L10 and the grounded capacitor C10 are both connected to the fourth antenna A4.

9. The on-line monitoring circuit for sulfur hexafluoride gas density and trace water content according to claim 3, characterized in that: The band-stop reflection circuit adopts a radio frequency open line.

10. An online monitoring device for sulfur hexafluoride gas density and trace water content, characterized in that: The device for online monitoring of sulfur hexafluoride gas density and trace water content comprises the online monitoring circuit for sulfur hexafluoride gas density and trace water content according to any one of claims 1 to 9.

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