SF6 gas electrification tendency determination method based on resistance-capacitance circuit

Abstract

The invention discloses an SF6 gas electrification tendency measuring method based on a resistance-capacitance circuit. The SF6 gas electrification tendency measuring method comprises the following steps that SF6 gas in a gas chamber is blown between two flat plates of a capacitor; aC voltage is applied to the resistance-capacitance circuit where the capacitor is located. And detecting the output voltage of a rectifying circuit connected in parallel with a resistor in the resistance-capacitance circuit. And judging whether the SF6 gas has an electrification tendency or not according to the output voltage. According to the condition that SF6 <-> ions which are positively correlated with severity can be generated by electrical equipment discharge, SF6 gas electrification tendency detection is realized by measuring the resistance voltage on the resistance-capacitance circuit consisting of the parallel plate capacitor containing the SF6 gas and the resistor, so that discharge defect identification is realized, the method is simple and easy to implement, and the detection efficiency is improved. The problem that various decomposition product detectors need to be configured when SF6 gas discharge defects are detected through gas taking in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the field of SF6 gas charging tendency measurement, and in particular to a SF6 gas charging tendency measurement method based on a resistor-capacitor circuit. Background Art

[0002] Sulfur hexafluoride (SF6) is widely used in various high and medium voltage electrical equipment due to its excellent insulation performance and arc extinguishing ability. Discharge defects may occur during the operation of electrical equipment, generating a series of acidic and corrosive decomposition products, damaging internal insulation materials and threatening the normal operation of electrical equipment. Therefore, discharge detection of SF6 gas electrical equipment is a key content of power operation and maintenance work.

[0003] The most widely used method for identifying discharge defects is to detect the decomposition products of SF6 gas discharge by sampling gas. However, different types of discharges produce different types of decomposition products. Standard DL / T 1359-2014 stipulates that on-site analysis needs to detect decomposition products such as SO2, HF, H2S, and CF4 to accurately identify discharge defects. Therefore, a variety of different decomposition product detectors need to be configured on site, which has high instrument procurement costs and complex operation and maintenance. Summary of the invention

[0004] The present invention provides a method for determining the charging tendency of SF6 gas based on a resistor-capacitor circuit, which can solve the problem that a plurality of decomposition product detectors need to be configured for the existing gas sampling detection of SF6 gas discharge defects.

[0005] The embodiment of the present invention provides a method for determining the charging tendency of SF6 gas based on a resistor-capacitor circuit, comprising the following steps: blowing the SF6 gas in the gas chamber into between two plates of the capacitor. Applying an AC voltage U to the resistor-capacitor circuit where the capacitor is located AC . Detect the output voltage U of the rectifier circuit connected in parallel with the resistor in the RC circuit d According to U d Determine whether SF6 gas has a tendency to be charged.

[0006] In some of these embodiments, according to U d Determine whether SF6 gas has a tendency to be charged, including: d Calculate the dielectric constant ε of SF6 gas r According to ε r Determine whether SF6 gas has a tendency to be charged.

[0007] In some of these embodiments, according to ε r Determine whether SF6 gas has a tendency to be charged, including: if ε r If the dielectric constant is greater than the dielectric constant of SF6 gas in the uncharged state, the SF6 gas has a tendency to be charged; otherwise, the SF6 gas has no tendency to be charged.

[0008] In some of these embodiments, the rectifier circuit includes a full-wave rectifier circuit.

[0009] In some of these embodiments, according to U d Calculate the dielectric constant ε of SF6 gas r , including: ε is calculated using the following formula r : Where k is the electrostatic force constant; d is the distance between the plates; S is the area of ​​the plates; f is the frequency of the AC voltage; and R is the resistance.

[0010] In some of the embodiments, blowing SF6 gas in the gas chamber into between two plates of the capacitor includes: blowing SF6 gas into between the two plates from one side of the two plates and flowing out from the other opposite side.

[0011] In some of the embodiments, SF6 gas is blown between the two plates from a middle position between the two plates.

[0012] In some of these embodiments, according to U d Determine whether SF6 gas has a tendency to be charged, including: calculating the output voltage U of the rectifier circuit when SF6 gas is not charged, and according to U d and U to determine whether SF6 gas has a tendency to be charged.

[0013] In some of these embodiments, according to U d and U to determine whether SF6 gas has a tendency to be charged, including: if U d If it is greater than U, the SF6 gas has a tendency to be charged; otherwise, the SF6 gas has no tendency to be charged.

[0014] In some embodiments, after determining that the SF6 gas has a tendency to be charged, according to U d The difference between U and U is used to evaluate the severity of the discharge defect.

[0015] According to an embodiment of the present invention, a method for determining the charging tendency of SF6 gas based on a resistor-capacitor circuit is provided, comprising the following steps: blowing SF6 gas in a gas chamber into between two plates of a capacitor. Applying an AC voltage U to the resistor-capacitor circuit where the capacitor is located AC . Detect the output voltage U of the rectifier circuit connected in parallel with the resistor in the RC circuit d According to U d Determine whether SF6 gas has a tendency to be charged. The present invention is based on the fact that discharge of electrical equipment will produce SF6 gas which is positively correlated with the severity. -Ions, by measuring the resistance voltage on the RC circuit composed of the parallel plate capacitor and resistor containing SF6 gas, the SF6 gas charging tendency detection is realized, thereby realizing the discharge defect identification, which is simple and easy, and solves the problem that the existing gas extraction detection of SF6 gas discharge defects requires the configuration of multiple decomposition product detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the structure of the SF6 gas charging tendency measuring device in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] See also Figure 1 The embodiment of the present invention provides a device for measuring the charging tendency of SF6 gas based on a resistor-capacitor circuit, wherein a simulated discharge chamber 1 is connected to a capacitor 5 via a pressure reducing valve 2, a flow meter 3, and a needle valve 4, so that the SF6 gas in the simulated discharge chamber 1 flows through the pressure reducing valve 2, the flow meter 3, and the needle valve 4, and flows into the space between two parallel metal plates of the capacitor 5. The capacitor 5 and the resistor 6 are connected in series to form a resistor-capacitor circuit, and an AC voltage is applied to the resistor-capacitor circuit. The resistor 6 is connected in parallel with a rectifier circuit 7. The rectifier circuit 7 can be a full-wave rectifier circuit.

[0020] The embodiment of the present invention provides a method for measuring the charging tendency of SF6 gas based on a resistor-capacitor circuit, which can adopt the above-mentioned SF6 gas charging tendency measuring device. The method for measuring the charging tendency of SF6 gas includes the following steps:

[0021] 1) Blow the SF6 gas in the gas chamber into between the two plates of capacitor 5.

[0022] The above steps may include: a) setting the pressure reducing valve 2 to 0.2MPa, allowing the SF6 gas in the gas chamber to enter the flow meter 3, and adjusting the needle valve 4 to control the flow rate at 200ml / min. b) blowing the SF6 gas from the middle position of one side of the two parallel metal plates into between the two parallel metal plates, and flowing out from the other opposite side.

[0023] In the above steps, the capacitance is determined by:

[0024]

[0025] In the formula, k is the electrostatic force constant, which is a constant; d is the distance between the plates; and S is the area of ​​the plates.

[0026] 2) Apply an AC voltage U to the RC circuit where capacitor 5 is located. AC .

[0027] In the above steps, the voltage U across the resistor 6 R The calculation formula is:

[0028]

[0029] Where f is the frequency of the AC voltage; R is the resistance; and C is the capacitance.

[0030] According to the capacitance determination formula, the voltage U across the resistor 6 R The calculation formula can be transformed into:

[0031]

[0032] 3) Detect the output voltage U of the rectifier circuit 7 connected in parallel with the resistor in the RC circuit d .

[0033] In the above steps, the rectifier circuit 7 can be a full-wave rectifier circuit. AC The voltage is divided into two positive and negative half cycles, so U R It is also divided into positive and negative half cycles. A full-wave rectifier circuit is designed to convert the output voltage U d Modulated to have only forward voltage.

[0034] In the above steps, according to the voltage U across the resistor 6 R The output voltage U of the rectifier circuit 7 is calculated by d The calculation formula is:

[0035]

[0036] When the AC voltage source U AC , resistance R, spacing d, area S remain unchanged, the output voltage U d With ε r There is a positive proportional relationship. Since the dielectric constant of SF6 gas is proportional to the SF6 - The number of ions is positively correlated, and SF6 - The number of ions is positively correlated with the degree of discharge defects, so the output voltage U d It can reflect the severity of discharge defects and realize their quantitative detection.

[0037] 4) According to U d Determine whether SF6 gas has a tendency to be charged.

[0038] The above steps may include:

[0039] a1) According to U d Calculate the dielectric constant ε of SF6 gas r . The following formula is used to calculate ε r :

[0040]

[0041] b1) According to ε r Determine whether SF6 gas has a tendency to be charged. r If the dielectric constant is greater than the dielectric constant of SF6 gas in the uncharged state, the SF6 gas has a tendency to be charged; otherwise, the SF6 gas has no tendency to be charged.

[0042] Studies have shown that SF6 gas will generate SF6 when it is discharged. - Ions have a tendency to be charged. Compared with SF6 gas molecules, SF6 - Because the ion has an additional electron on the basis of the original electrical neutrality, the charge distribution is uneven and the polarity increases significantly. Since the dielectric constant of the gas is positively correlated with the polarity, when SF6 gas is doped with SF6 - After ionization, its dielectric constant will increase, and the increase is similar to that of SF6 - In the present invention, a parallel plate capacitor 5 and a resistor 6 are connected in series and an AC power supply is applied. The dielectric constant of the SF6 gas flowing in the middle of the parallel plate is calculated by measuring the voltage of the resistor 6, thereby indirectly measuring the charging tendency of the SF6 gas.

[0043] The above steps may also include:

[0044] a2) Calculate the output voltage U of the rectifier circuit 7 when the SF6 gas is not charged.

[0045] b2) According to U d and U determine whether SF6 gas has a tendency to be charged. d If it is greater than U, the SF6 gas has a tendency to be charged, otherwise, the SF6 gas does not have a tendency to be charged. d The difference between U and U is used to evaluate the severity of the discharge defect.

[0046] In summary, the present invention can generate SF6 which is positively correlated with the severity according to the discharge of electrical equipment. -Ions, by measuring the voltage of resistor 6 on the resistor-capacitor circuit composed of parallel plate capacitor 5 and resistor 6 containing SF6 gas, the SF6 gas charging tendency detection is realized, thereby realizing the discharge defect identification, which is simple and easy, and solves the problem that the existing gas extraction detection of SF6 gas discharge defects requires the configuration of multiple decomposition product detectors.

[0047] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the charging tendency of SF6 gas based on a resistor-capacitor circuit, characterized in that: The following steps are involved: Blow the SF6 gas in the gas chamber into between the two plates of the capacitor; Apply an AC voltage U to the resistor-capacitor circuit where the capacitor is located. AC ; Detect the output voltage U of the rectifier circuit connected in parallel with the resistor in the RC circuit d ; According to U d Determine whether the SF6 gas has a tendency to be charged.

2. The method for measuring the charging tendency of SF6 gas according to claim 1, characterized in that: According to U d Determining whether the SF6 gas has a tendency to be charged includes: According to U d Calculate the dielectric constant ε of the SF6 gas r ; According to ε r Determine whether the SF6 gas has a tendency to be charged.

3. The method for measuring the charging tendency of SF6 gas according to claim 2, characterized in that: According to ε r Determining whether the SF6 gas has a tendency to be charged includes: If ε r If the dielectric constant of the SF6 gas is greater than the dielectric constant of the SF6 gas in the uncharged state, the SF6 gas has a charging tendency; otherwise, the SF6 gas has no charging tendency.

4. The method for measuring the charging tendency of SF6 gas according to claim 2, characterized in that: The rectifier circuit includes a full-wave rectifier circuit.

5. The method for measuring the charging tendency of SF6 gas according to claim 4, characterized in that: According to U d Calculate the dielectric constant ε of the SF6 gas r ,include: Calculate ε using the following formula r : Where k is the electrostatic force constant; d is the distance between the plates; S is the area of ​​the plates; f is the frequency of the AC voltage; and R is the resistance.

6. The method for measuring the charging tendency of SF6 gas according to claim 1, characterized in that: Blow the SF6 gas in the gas chamber into between the two plates of the capacitor, including: The SF6 gas is blown into between the two plates from one side thereof and flows out from the other opposite side.

7. The method for measuring the charging tendency of SF6 gas according to claim 6, characterized in that: The SF6 gas is blown into between the two flat plates from the middle position of the two flat plates.

8. The method for measuring the charging tendency of SF6 gas according to claim 1, characterized in that: According to U d Determining whether the SF6 gas has a tendency to be charged includes: Calculate the output voltage U of the rectifier circuit when the SF6 gas is not charged, according to U d and U to determine whether the SF6 gas has a tendency to be charged.

9. The method for measuring the charging tendency of SF6 gas according to claim 8, characterized in that: According to U d and U to determine whether the SF6 gas has a tendency to be charged, including: If U d If it is greater than U, the SF6 gas has a charging tendency; otherwise, the SF6 gas has no charging tendency.

10. The method for measuring the charging tendency of SF6 gas according to claim 9, characterized in that: After determining that the SF6 gas has a tendency to be charged, according to U d The difference between U and U is used to evaluate the severity of the discharge defect.

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