SF6 gas electrification tendency determination method

Abstract

The invention discloses a method for measuring the electrification tendency of SF6 gas. The method comprises the following steps: measuring the humidity D1 of the SF6 gas in a gas chamber; and establishing a frost layer by adopting uncharged SF6 gas with the humidity of D2. The SF6 gas in the gas chamber and the uncharged SF6 gas with the humidity of D2 are mixed according to a set proportion to obtain first mixed gas, the first mixed gas is led to the frost layer, and the time T required by the first mixed gas for changing the thickness of the frost layer is measured. Leading a second mixed gas obtained by mixing the uncharged SF6 gas with the humidity of D1 and the uncharged SF6 gas with the humidity of D2 according to a set proportion to the frost layer, and measuring the time T1 required by the second mixed gas to change the thickness of the frost layer. And judging whether the SF6 gas in the gas chamber has an electrification tendency or not according to the T and the T1. According to the invention, based on the principle that SF6 <-> and H2O are combined after partial discharge, SF6 gas with certain humidity is taken as reference gas, and by measuring the elimination time for reducing a cold mirror frost layer of the reference gas to a specific thickness, the electrification tendency of the SF6 gas in the gas chamber can be measured.

Description

Technical Field

[0001] The present invention relates to the field of SF6 gas charging tendency measurement, and in particular to a SF6 gas charging tendency measurement method. Background Art

[0002] Partial discharge is the main precursor to insulation failure in electrical equipment. When partial discharge occurs, it is often accompanied by physical characteristics such as pulse current, electromagnetic waves, ultrasound, optical signals, and characteristic gases. Detecting these physical quantities can timely discover and warn of partial discharge defects inside the equipment to ensure equipment safety. However, the above detection methods all have certain limitations. For example, the pulse current method, electromagnetic wave and ultrasonic method are easily affected by environmental interference and have a high probability of false alarms. The optical method has poor sensitivity and requires the sensor to be built into the electrical equipment, which is not easy to operate. The characteristic gas detection method is currently a commonly used means of monitoring the status of electrical equipment, but the relationship between the characteristic gas content and the discharge amount is not clear, and it cannot reflect the intensity of partial discharge inside the equipment. Summary of the invention

[0003] The present invention provides a method for determining the charging tendency of SF6 gas, which can determine whether SF6 gas has a charging tendency.

[0004] An embodiment of the present invention provides a method for determining the charging tendency of SF6 gas, comprising the following steps: measuring the humidity D1 of SF6 gas in a gas chamber. Using non-charged SF6 gas with a humidity of D2 to establish a frost layer. Passing a first mixed gas obtained by mixing the SF6 gas in the gas chamber with non-charged SF6 gas with a humidity of D2 in a set ratio to the frost layer, and measuring the time T required for the first mixed gas to change the thickness of the frost layer. Passing a second mixed gas obtained by mixing non-charged SF6 gas with a humidity of D1 and non-charged SF6 gas with a humidity of D2 in a set ratio to the frost layer, and measuring the time T1 required for the second mixed gas to change the thickness of the frost layer. Judging whether the SF6 gas in the gas chamber has a charging tendency based on T and T1.

[0005] In some embodiments, judging whether the SF6 gas in the gas chamber has a tendency to be charged is performed based on T and T1, including: if T is less than T1, the SF6 gas in the gas chamber has a tendency to be charged. Otherwise, the SF6 gas in the gas chamber has no tendency to be charged.

[0006] In some of the embodiments, measuring the humidity D1 of SF6 gas in the gas chamber includes: passing the SF6 gas in the gas chamber into a dew point meter, and measuring the humidity D1 of SF6 gas in the gas chamber by the dew point meter.

[0007] In some of these embodiments, D2 is greater than D1.

[0008] In some of the embodiments, a frost layer is established using SF6 gas without charge and with a humidity of D2, including: passing the SF6 gas without charge and with a humidity of D2 into a dew point meter, measuring the dew point of the SF6 gas without charge and with a humidity of D2 by the dew point meter, and waiting for the dew point indication of the dew point meter to stabilize, i.e., a frost layer has been established on the mirror surface of the dew point meter.

[0009] In some of the embodiments, after a frost layer is formed on the mirror surface of the dew point meter, the temperature of the mirror surface is controlled to remain constant at the dew point of SF6 gas with no charge and a humidity of D2, so as to maintain a constant thickness of the frost layer.

[0010] In some of the embodiments, after a frost layer is formed on the mirror surface of the dew point meter, the light energy L0 displayed by the dew point meter representing the current frost layer thickness is recorded.

[0011] In some of the embodiments, a first mixed gas obtained by mixing SF6 gas in an air chamber with non-charged SF6 gas with a humidity of D2 in a set ratio is passed to a frost layer, and the time T required for the first mixed gas to change the thickness of the frost layer is measured, including: mixing SF6 gas in an air chamber with a set flow rate and SF6 gas with a set flow rate and a humidity of D2 to obtain the first mixed gas, and then passing the first mixed gas into a dew point meter, starting timing, and when the light energy displayed by the dew point meter reaches L1 representing a specific frost layer thickness, and L1 is set to be greater than L0, stopping timing to obtain time T.

[0012] In some of the embodiments, L1 is further set to be smaller than the light energy L2 corresponding to the dew point of SF6 gas with a humidity of D1.

[0013] In some of the embodiments, a second mixed gas obtained by mixing uncharged SF6 gas with a humidity of D1 and uncharged SF6 gas with a humidity of D2 in a set ratio is passed to the frost layer, and the time T1 required for the second mixed gas to change the thickness of the frost layer is measured, including: mixing a set flow rate of uncharged SF6 gas with a humidity of D1 and a set flow rate of uncharged SF6 gas with a humidity of D2 to obtain the second mixed gas, and then passing it into a dew point meter, starting timing, and stopping timing when the light energy displayed by the dew point meter reaches L1, thereby obtaining time T1.

[0014] According to an embodiment of the present invention, a method for determining the charging tendency of SF6 gas is provided, comprising the following steps: measuring the humidity D1 of SF6 gas in the gas chamber. Using non-charged SF6 gas with a humidity of D2 to establish a frost layer. Passing a first mixed gas obtained by mixing the SF6 gas in the gas chamber with non-charged SF6 gas with a humidity of D2 in a set ratio to the frost layer, and measuring the time T required for the first mixed gas to change the thickness of the frost layer. Passing a second mixed gas obtained by mixing non-charged SF6 gas with a humidity of D1 and non-charged SF6 gas with a humidity of D2 in a set ratio to the frost layer, and measuring the time T1 required for the second mixed gas to change the thickness of the frost layer. Judging whether the SF6 gas in the gas chamber has a charging tendency based on T and T1. The present invention utilizes SF6 after partial discharge to obtain a second mixed gas. - Combining the principle with H2O, using SF6 gas with a certain humidity as the reference gas, by measuring the time it takes for the frost layer on the reference gas cold mirror to disappear to a specific thickness, the charge tendency of SF6 gas in the gas chamber can be measured, providing technical support for the determination of the degree of partial discharge based on the humidity of SF6 gas. The present invention measures the dew disappearance time instead of measuring the humidity value, without waiting for the frost layer thickness to drop to the frost layer thickness corresponding to the dew point temperature, thereby solving the problem of time-consuming measurement of the dew point humidity of gases, especially low-humidity gases, and shortening the measurement time of the charge tendency of SF6. The present invention uses a conventional dew point meter to perform charge tendency testing while detecting the humidity value during daily operation and maintenance, without the need for additional instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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.

[0016] Figure 1 Schematic diagram of a device for measuring the charging tendency of SF6 gas in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] 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.

[0018] See also Figure 1 An embodiment of the present invention provides a device for measuring the charging tendency of SF6 gas, including a gas chamber 1, a reference gas cylinder 2, a first solenoid valve 3, a second solenoid valve 4, a first flow regulating valve 5, a second flow regulating valve 6 and a dew point meter 7.

[0019] The gas chamber 1 contains SF6 gas.

[0020] The reference gas cylinder 2 contains a reference gas. Since the SF6 gas in the electrical equipment is usually less than 500 ppm, the SF6 gas with a humidity content of 500 ppm can be selected as the reference gas.

[0021] The first solenoid valve 3 is connected to the gas outlet of the gas chamber 1 .

[0022] The second solenoid valve 4 is connected to the gas outlet of the reference gas cylinder 2 .

[0023] The first flow regulating valve 5 is connected to the first solenoid valve 4 .

[0024] The second flow regulating valve 6 is connected to the second solenoid valve 4 .

[0025] The dew point meter 7 is connected to the first flow rate regulating valve 5 and the second flow rate regulating valve 6. The dew point meter 7 has an exhaust port 8.

[0026] The embodiment of the present invention provides a method for measuring the charging tendency of SF6 gas, which can adopt the above-mentioned SF6 gas charging tendency measuring device. The method for measuring the charging tendency of SF6 gas comprises the following steps:

[0027] (1) Measure the SF6 gas humidity D1 in the gas chamber 1.

[0028] The above steps can be specifically as follows: open the first solenoid valve 3, adjust the flow rate of the first flow control valve 5 to Q1 (such as 200 mL / min), pass the SF6 gas in the gas chamber 1 into the dew point meter, measure the SF6 gas humidity D1 in the gas chamber 1 through the dew point meter 7, and close the first solenoid valve 3.

[0029] (2) Use SF6 gas with no charge and humidity D2 to establish the frost layer.

[0030] In the above steps, D2 is greater than D1. The above steps may be specifically as follows: open the second solenoid valve 4, adjust the flow rate of the second flow regulating valve 6 to Q2 (such as 200 mL / min), pass the SF6 gas without electricity and with a humidity of D2 as a reference gas into the dew point meter 7, measure the dew point of the reference gas by the dew point meter 7, and wait for the dew point indication of the dew point meter 7 to be stable, that is, a frost layer of a certain thickness has been established on the mirror surface of the dew point meter 7.

[0031] After a frost layer of a certain thickness is formed on the mirror surface of the dew point meter 7, the dew point meter 7 controls the temperature of the mirror surface to be kept constant at the dew point of the reference gas, thereby maintaining the thickness of the frost layer constant.

[0032] After a frost layer of a certain thickness is formed on the mirror surface of the dew point meter 7, the light energy L0 displayed by the dew point meter 7 is recorded, which represents the thickness of the frost layer at this time.

[0033] (3) The SF6 gas in the gas chamber is mixed with the non-charged SF6 gas with a humidity of D2 in a set ratio to obtain a first mixed gas which is passed to the frost layer, and the time T required for the first mixed gas to change the thickness of the frost layer is measured.

[0034] In the above steps, the thickness change of the frost layer can be a decrease in the thickness of the frost layer. At this time, the time is the dew elimination time. Dew elimination reduces the thickness of the frost layer, which can also be called defrosting. The above steps can be specifically as follows: keep the second solenoid valve 4 open and the flow rate of the second flow regulating valve at Q2, open the first solenoid valve 3, adjust the flow rate of the first flow regulating valve 5 to Q2 (such as 200mL / min), mix the SF6 gas and the reference gas in the air chamber 1 to obtain a first mixed gas, and then introduce the dew point meter 7 to start timing. Since the humidity D1 of the SF6 gas in the air chamber 1 is lower than the humidity D2 of the reference gas, that is, lower than the refrigeration humidity of the dew point meter 7, the humidity of the first mixed gas is lower than the refrigeration humidity of the dew point meter 7, and the thickness of the frost layer condensed on the mirror surface The temperature starts to decrease, the light energy increases, and the change of the light energy displayed by the dew point meter is observed. When the light energy displayed by the dew point meter 7 reaches L1 representing a specific frost layer thickness, L1 is set to be greater than L0 and less than the light energy L2 corresponding to the dew point of SF6 gas with a humidity of D1 (that is, the light energy displayed by the dew point meter after the dew point of SF6 gas with a humidity of D1 is stabilized), that is, L2>L1>L0 (at this time, the dew point frost layer of the gas with a humidity ≤D1 can reach a specific thickness. It should be noted that the lower the humidity, the greater the light energy), stop timing and obtain the time T. The above process only measures the time when the frost layer thickness drops to the light energy of L1, and the frost layer thickness has not yet dropped to the frost layer thickness corresponding to the dew point, so that the measured dew-free time is less than the time required to measure the humidity, thereby shortening the measurement time.

[0035] (4) A second mixed gas obtained by mixing uncharged SF6 gas with a humidity of D1 and uncharged SF6 gas with a humidity of D2 in a set ratio is passed to the frost layer, and the time T1 required for the second mixed gas to change the thickness of the frost layer is measured.

[0036] In the above steps, the change in the thickness of the frost layer can be a decrease in the thickness of the frost layer. In this case, the time is the dew-removal time. Dew-removal reduces the thickness of the frost layer, which can also be called defrosting. The above steps can be specifically as follows: in the preliminary test process, a non-charged SF6 gas with a flow rate of Q2 (such as 200 mL / min) and a humidity of D1 and a non-charged SF6 gas with a flow rate of Q2 (such as 200 mL / min) and a humidity of D2 are mixed to obtain a second mixed gas, which is then introduced into the dew point meter 7 and timing is started. Since the humidity of the second mixed gas is also lower than the refrigeration humidity of the dew point meter 7, the thickness of the frost layer condensed on the mirror surface begins to decrease, and the light energy increases. When the light energy displayed by the dew point meter 7 reaches L1, the timing is stopped to obtain the time T1.

[0037] (5) Based on T and T1, determine whether the SF6 gas in gas chamber 1 has a tendency to be charged.

[0038] The above steps may be: if the SF6 gas in the gas chamber 1 has a tendency to be charged, then the SF6 gas in the SF6 gas - It combines with water molecules to form SF6 - ·H2O polymer accelerates the dew removal speed of the frost layer and shortens the dew removal time. Therefore, if T is less than T1, the SF6 gas in the gas chamber 1 has a tendency to be charged, that is, partial discharge occurs in the gas chamber 1. Otherwise, the SF6 gas in the gas chamber 1 does not have a tendency to be charged. The greater the difference between T and T1, the more obvious the tendency of the SF6 gas in the gas chamber 1 to be charged, that is, the more severe the discharge.

[0039] Insulating gas humidity is an important detection index for daily operation and maintenance of electrical equipment. Currently, there is no research on the relationship between gas humidity and discharge failure and discharge amount. When partial discharge occurs in electrical equipment, negative ions SF6 will be generated. - The degree of discharge failure will affect the generation of negative ion SF6 - Quantity, SF6 - It combines with H2O to form SF6 - H2O polymerizes, causing the gas humidity to decrease, so the H2O concentration can be used as a fulcrum to determine the SF6 charging tendency. The stronger the SF6 gas charging tendency in chamber 1, the more SF6 it carries. - The more, the stronger the ability to combine with water, the stronger the ability to eliminate the frost layer formed during the reference gas measurement, and the shorter the time it takes for the frost layer to reach a specific thickness. Therefore, the dew removal time can reflect whether SF6 has a tendency to be charged and the strength of the charging tendency, thereby diagnosing the severity of partial discharge faults. Since conventional gas dew point humidity measurement requires the moisture in the gas to condense into a frost layer of a specific thickness on the surface of the cold mirror, it takes a long time for low-humidity gas. Moreover, when measuring high-humidity gas and then low-humidity gas, due to the residual gas moisture in the pipeline, it takes a long time to obtain an accurate low-humidity dew point value (longer than the time of measuring low-humidity gas first and then high-humidity gas).

[0040] The method of the present invention uses the H2O content in the insulating gas as the fulcrum, and uses SF6 gas with a certain humidity as the reference gas. The method further analyzes the discharge failure of the electrical equipment by measuring the elimination time of the frost layer of the reference gas caused by the SF6 gas of the electrical equipment to be reduced to a specific thickness during the dew point measurement. The present invention can determine whether the SF6 gas has a tendency to be charged only through daily operation and maintenance humidity detection, further analyze the amount of local discharge, and measure the dew elimination time instead of measuring humidity, thereby solving the problem of time-consuming gas, especially low-humidity gas dew point humidity detection, shortening the SF6 charging tendency determination time, and greatly reducing the technical complexity and cost of conventional electrical equipment status monitoring methods.

[0041] In summary, the present invention utilizes SF6 after partial discharge - Combining the principle with H2O, using SF6 gas with a certain humidity as the reference gas, by measuring the time it takes for the frost layer on the reference gas cold mirror to disappear to a specific thickness, the SF6 gas charge tendency can be measured, providing technical support for the determination of the degree of partial discharge based on the humidity of SF6 gas. The present invention measures the dew disappearance time instead of measuring the humidity value, without waiting for the frost layer thickness to drop to the frost layer thickness corresponding to the dew point temperature, thereby solving the problem of time-consuming dew point humidity measurement of gases, especially low-humidity gases, and shortening the SF6 charge tendency measurement time. The present invention uses a conventional dew point meter to perform charge tendency testing while detecting humidity values ​​during daily operation and maintenance, without the need for additional instruments.

[0042] 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.

[0043] 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, characterized in that: The following steps are involved: Measure the SF6 gas humidity D1 in the gas chamber; Use SF6 gas without charge and with humidity of D2 to establish the frost layer; Passing a first mixed gas obtained by mixing the SF6 gas in the gas chamber with the non-charged SF6 gas with a humidity of D2 according to a set ratio to the frost layer, and measuring the time T required for the first mixed gas to change the thickness of the frost layer; Passing a second mixed gas obtained by mixing the non-charged SF6 gas with a humidity of D1 and the non-charged SF6 gas with a humidity of D2 according to the set ratio to the frost layer, and measuring the time T1 required for the second mixed gas to change the thickness of the frost layer; It is determined based on T and T1 whether the SF6 gas in the gas chamber 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 T and T1, judging whether the SF6 gas in the gas chamber has a tendency to be charged includes: If T is less than T1, the SF6 gas in the gas chamber has a tendency to be charged; otherwise, the SF6 gas in the gas chamber has no tendency to be charged.

3. The method for measuring the charging tendency of SF6 gas according to claim 1, characterized in that: Measuring SF6 gas humidity D1 in the gas chamber, including: The SF6 gas in the gas chamber is introduced into a dew point meter, and the humidity D1 of the SF6 gas in the gas chamber is measured by the dew point meter.

4. The method for measuring the charging tendency of SF6 gas according to claim 1, characterized in that: D2 is greater than D1.

5. The method for measuring the charging tendency of SF6 gas according to claim 4, characterized in that: The frost layer is established by using the non-charged SF6 gas with a humidity of D2, including: The non-charged SF6 gas with a humidity of D2 is passed into a dew point meter, and the dew point of the non-charged SF6 gas with a humidity of D2 is measured by the dew point meter. When the dew point reading of the dew point meter is stable, the frost layer is formed on the mirror surface of the dew point meter.

6. The method for measuring the charging tendency of SF6 gas according to claim 5, characterized in that: After the frost layer is formed on the mirror surface of the dew point meter, the temperature of the mirror surface is controlled to remain constant at the dew point of the non-charged SF6 gas with a humidity of D2, so as to maintain the thickness of the frost layer constant.

7. The method for measuring the charging tendency of SF6 gas according to claim 5, characterized in that: After the frost layer is formed on the mirror surface of the dew point meter, the light energy L0 displayed by the dew point meter representing the current frost layer thickness is recorded.

8. The method for measuring the charging tendency of SF6 gas according to claim 7, characterized in that: The first mixed gas obtained by mixing the SF6 gas in the gas chamber with the non-charged SF6 gas with a humidity of D2 according to a set ratio is passed to the frost layer, and the time T required for the first mixed gas to change the thickness of the frost layer comprises: The SF6 gas in the gas chamber at a set flow rate and the non-charged SF6 gas at the set flow rate with a humidity of D2 are mixed to obtain a first mixed gas, which is then introduced into the dew point meter and timing is started. When the light energy displayed by the dew point meter reaches L1 representing a specific frost layer thickness and L1 is set to be greater than L0, timing is stopped to obtain time T.

9. The method for measuring the charging tendency of SF6 gas according to claim 8, characterized in that: L1 is also set to be smaller than the light energy L2 corresponding to the dew point of SF6 gas having a humidity of D1.

10. The method for measuring the charging tendency of SF6 gas according to claim 8, characterized in that: Passing a second mixed gas obtained by mixing non-charged SF6 gas with a humidity of D1 and non-charged SF6 gas with a humidity of D2 according to the set ratio to the frost layer, and measuring the time T1 required for the second mixed gas to change the thickness of the frost layer, comprising: The non-charged SF6 gas with a set flow rate and a humidity of D1 and the non-charged SF6 gas with a set flow rate and a humidity of D2 are mixed to obtain a second mixed gas, which is then introduced into the dew point meter and timing is started. When the light energy displayed by the dew point meter reaches L1, timing is stopped to obtain time T1.

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