Conductivity characteristic determination method, determination device, measurement method and measurement equipment

Abstract

The present application discloses a determination method, a determination device, a measurement method and a measurement device for conductivity characteristics. The determination method comprises: obtaining the potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from the central hole position of the sample to be tested; and determining the conductivity distribution of the sample to be tested according to the potential distribution. In the determination method, the conductivity distribution of the sample to be tested can be obtained by measuring the surface potential distribution of the sample to be tested under the action of an externally applied voltage, thereby not only improving the accuracy of the conductivity distribution measurement, but also effectively simplifying the measurement process to improve the measurement efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of measuring the electrical conductivity of dielectric materials, and in particular to a method for determining electrical conductivity characteristics, a determination device, a measurement method and a measurement device. Background Art

[0002] Gas-insulated pipeline transmission (GIL) and gas-insulated switchgear (GIS) are becoming increasingly important in DC transmission systems. However, the insulators cast with epoxy resin inside the equipment are always facing the problem of charge accumulation at the gas-solid interface. Under the influence of the accumulated surface charge, the electric field on the insulation surface is distorted, which can easily cause surface flashover accidents in severe cases. Therefore, it is urgent to solve the problem of electric field distortion on the insulation surface, improve the electrical resistance of the gas-solid interface inside the DC GIS / GIL equipment, and help promote the development of high-voltage DC electrical equipment.

[0003] At present, there are three types of gradient conductivity construction methods involved in related research: 1). Active construction, that is, combining the simulation calculation of the material's surface electric field, artificially and actively constructing a conductivity gradient distribution that matches a certain electric field distribution; 2). Passive construction, that is, using the properties of the nonlinear conductive material itself, so that it exhibits different conductivity sizes in different areas according to the actual electric field distribution along the surface during operation, thereby forming a conductivity gradient distribution; 3). Combining active construction with passive construction, that is, actively constructing the gradient distribution of the material's nonlinear conductivity characteristics, so that the material's nonlinear conductivity characteristics (nonlinear conductivity coefficient) have gradient distribution characteristics. By constructing the material's gradient conductivity, the local electric field distortion on the insulation surface can be effectively alleviated, and the surface DC tolerance can be improved.

[0004] In the related technologies, all three types of construction methods have the problem of being unable to effectively measure the gradient conductivity characteristics of the composite coating, and the ideal simulation calculation method is often inconsistent with the actual situation, resulting in difficulty in making breakthroughs in improving the insulation surface electrical resistance of the gradient conductivity coating.

[0005] In summary, it is necessary to propose a testing method for the nonlinear conductivity characteristics of functionally gradient materials to improve the accuracy of functionally gradient coating construction, thereby helping the further development of DC electrical equipment. Summary of the invention

[0006] In view of this, the present application provides a method for determining conductivity characteristics, a determination device, a measurement method and a measurement device, which can accurately obtain the conductivity distribution of the surface of the functional gradient material.

[0007] In a first aspect, the present application provides a method for determining the electrical conductivity characteristics of a functionally gradient material, comprising:

[0008] Acquiring a potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from a central hole position of the sample to be tested;

[0009] According to the potential distribution, the conductivity distribution of the sample to be tested is determined.

[0010] Optionally, the conductivity distribution of the sample to be tested is determined according to the potential distribution, which is performed in a manner represented by the following formula:

[0011]

[0012] J = σE;

[0013] In the above formula, J is the current density inside the sample to be tested, E is the electric field strength, σ is the DC conductivity, φ is the potential distribution, ρ is the distance from the center of the cross section of the sample to be tested, a1 is the inner diameter of the cross section, a2 is the outer diameter of the cross section, is the potential value at radius a1, is the potential value at radius a2.

[0014] In a second aspect, the present application provides a device for determining the conductivity characteristics of a functionally gradient material, comprising:

[0015] An acquisition module, used for acquiring the potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from the central hole position of the sample to be tested;

[0016] The determination module is used to determine the conductivity distribution of the sample to be tested according to the potential distribution.

[0017] In a third aspect, the present application provides a method for measuring the electrical conductivity characteristics of a functionally gradient material, comprising:

[0018] Apply a DC voltage to the central hole of the sample to be tested;

[0019] The potential distribution on the surface of the sample to be tested after the DC voltage is applied is collected to obtain the conductivity distribution of the sample to be tested according to the potential distribution.

[0020] Optionally, the measuring method further includes:

[0021] Collect loop current.

[0022] Optionally, collecting the potential distribution on the surface of the sample to be tested after the DC voltage is applied occurs after the relaxation current of the loop current is stabilized.

[0023] Optionally, the loop current flows from a power electrode for applying a DC voltage to a ground electrode.

[0024] Optionally, collecting the potential distribution on the surface of the sample to be tested after applying the DC voltage includes:

[0025] Changing the level of DC voltage;

[0026] collecting multiple surface potentials of the sample to be tested before and after changing the DC voltage level, and obtaining multiple conductivity distributions from the multiple surface potentials of the sample to be tested;

[0027] The conductivity distributions of different times are fitted to obtain the nonlinear conductivity distribution of the sample to be tested.

[0028] Optionally, the conductivity distribution of the sample to be tested is obtained according to the potential distribution, which is expressed by the following formula:

[0029]

[0030] In the above formula, J is the current density inside the sample to be tested, E is the electric field strength, σ is the DC conductivity, φ is the potential distribution, ρ is the distance from the center of the cross section of the sample to be tested, a1 is the inner diameter of the cross section, a2 is the outer diameter of the cross section, is the potential value at radius a1, is the potential value at radius a2.

[0031] In a fourth aspect, the present application provides a device for measuring the electrical conductivity characteristics of a functional gradient material, wherein the device is used to implement the above-mentioned measurement method.

[0032] In the method disclosed in the present application, the conductivity distribution of the test sample can be obtained by measuring the potential distribution of the test sample under the action of an externally applied voltage, thereby not only improving the accuracy of the conductivity distribution measurement, but also effectively simplifying the measurement process to improve the measurement efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0034] Figure 1 An operational flow chart of a method for determining electrical conductivity characteristics of a functionally gradient material provided by an exemplary embodiment is shown.

[0035] Figure 2 A diagram showing the arrangement of SiC in a test sample provided by an exemplary embodiment.

[0036] Figure 3 A block diagram showing a structure of a device for determining the electrical conductivity characteristics of a functionally gradient material provided by an exemplary embodiment.

[0037] Figure 4A flow chart of a method for measuring the electrical conductivity characteristics of a functional gradient material with a relatively wide application scenario provided by an exemplary embodiment is shown.

[0038] Figure 5 A schematic diagram of the structure of a device for measuring the electrical conductivity characteristics of a functional gradient material provided by an exemplary embodiment is shown. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0040] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described here can be implemented in an order other than that illustrated or described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products or devices. The naming or numbering of steps in this application does not mean that the steps in the method flow must be executed in the time / logical sequence indicated by the naming or numbering. The process steps that have been named or numbered can change the execution order according to the technical purpose to be achieved, as long as the same or similar technical effects can be achieved. The division of units in this application is a logical division. There may be other division methods when it is implemented in actual applications. For example, multiple units can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection between units can be electrical or other similar forms, which are not limited in this application. In addition, the units or sub-units described as separate components may or may not be physically separated, may or may not be physical units, or may be distributed in multiple circuit units, and some or all of the units may be selected according to actual needs to achieve the purpose of the present application.

[0041] Please refer to Figure 1 ,in Figure 1 The flowchart shows a method for determining the electrical conductivity characteristics of a functionally graded material provided by an exemplary embodiment. This method is implemented through steps 102-104.

[0042] In step 102, the potential distribution on the surface of the specimen to be tested is obtained under the trigger of a DC voltage, where the DC voltage originates from the central hole position of the specimen to be tested.

[0043] It should be understood that "originates from" in "the DC voltage originates from the central hole position of the specimen to be tested" refers to the position where the source of the DC voltage applied to the specimen to be tested is located.

[0044] From the expression "the central hole position of the specimen to be tested" here, it can be seen that the specimen to be tested is a columnar structure with a cross-section of a ring-shaped material, such as Figure 2 As shown, a hole is opened at the central position of the specimen to be tested, and this hole is used to accommodate or place a power electrode for applying a DC voltage. For example, the power electrode is inserted into this hole.

[0045] In step 104, according to the potential distribution, the conductivity distribution of the specimen to be tested is determined.

[0046] As a preferred exemplary example, the specific process of determining the conductivity distribution of the specimen to be tested according to the potential distribution is as follows:

[0047] Step 1041: According to the basic equation of the constant electric field, under the action of this DC voltage, the relationship between the potential and conductivity of the material satisfies the equation:

[0048]

[0049] where J is the current density inside the specimen, E is the electric field strength, σ is the DC conductivity, and is the electric potential.

[0050] Step 1042: If the conductivity gradient distribution of the specimen to be tested is continuous, then:

[0051] Since the gradient conductivity of the specimen to be tested is distributed in a gradient along the radial direction, the conductivity should be the same at the same radius r, and the conductivity values of the specimen within the range of radius (r-k, r+k) have a small difference (k << r). The conductivity of the specimen to be tested is discretized along the radial direction, that is, several rings with inner and outer radii of (a, a+i), (a+i, a+2i),..., (a+ni, b) are taken along the radial direction (i << b);

[0052] If the conductivity gradient distribution of the specimen to be tested is discrete, then:

[0053] Taking the radius lengths (a1, a2,..., a at the positions where the conductivity of the specimen changes i,b) as the boundary, take several inner and outer radii along the radial direction, respectively (a1,a2),(a2,a3),…,(a i ,b) ring;

[0054] In summary, based on the above operations, the conductivity along the radial direction in each cross section of the sample to be tested (taking the cross section as a circular ring as an example) is the same and not zero, so the relationship between the potential and the conductivity of each cross section satisfies the equation:

[0055]

[0056] Step 1043, expand the above formula in a cylindrical coordinate system (a coordinate system established with the central axis of the sample to be tested as the Z axis and the center of the cross section of the sample to be tested as the origin). Since the thickness of the sample to be tested is extremely thin (for example, less than 1 mm), it is necessary to pay attention to the fact that the potential distribution of the sample is independent of the Z coordinate and the potential equipotential line distribution is independent of the θ coordinate during the expansion process.

[0057] Step 1044: Obtain the boundary potential condition of each ring according to the surface potential distribution data of the sample to be tested, that is:

[0058] When ρ=a1,

[0059] When ρ=a2,

[0060] In (3) above, ρ is the distance from the center of the cross section of the sample to be tested, a1 is the inner diameter of the cross section, a2 is the outer diameter of the cross section, is the potential value at radius a1, is the potential value at radius a2.

[0061] Step 1045: Substitute the boundary conditions into equation (2) to obtain the surface potential distribution calculation equation for each ring, namely:

[0062] Then the relationship between the potential, electric field and current density under a constant electric field is:

[0063]

[0064] J = σE (4);

[0065] Substituting the surface potential distribution calculation equation into the equation, we can obtain the relationship between the conductivity of each ring, the loop current, and the potential distribution. Substituting the loop current obtained by online measurement into the equation, we can calculate the conductivity gradient distribution of the sample along the radial direction.

[0066] Please refer to Figure 3, which shows a block diagram of a device for determining the conductivity characteristics of a functional gradient material provided by the present application. The device 200 includes:

[0067] An acquisition module 202 is used to acquire the potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from the central hole position of the sample to be tested;

[0068] The determination module 204 is used to determine the conductivity distribution of the sample to be tested according to the potential distribution.

[0069] Since the above methods have been discussed in detail, the specific implementation of the above modules will not be repeated here.

[0070] Please refer to Figure 4 , which shows a flow chart of a method for measuring the electrical conductivity characteristics of a functionally gradient material with a relatively wide range of application scenarios.

[0071] The method for measuring the electrical conductivity characteristics of the functional gradient material comprises:

[0072] Step 302: Apply a DC voltage to the central hole of the sample to be tested.

[0073] As mentioned above, during the actual operation of applying a DC voltage, the power electrode is inserted into the central hole of the sample to be tested.

[0074] Step 304 : collecting the potential distribution on the surface of the sample to be tested after the DC voltage is applied, so as to obtain the conductivity distribution of the sample to be tested according to the potential distribution.

[0075] It should be conceivable that the potential distribution on the surface of the sample to be tested after the DC voltage is applied can be collected by an electrostatic probe.

[0076] As a preferred embodiment, the measuring method further includes:

[0077] Collect loop current.

[0078] Here, when collecting the loop current, a high-precision ammeter can be connected in series to the loop.

[0079] As a preferred embodiment, the potential distribution on the surface of the sample to be tested after the DC voltage is applied is collected after the relaxation current of the loop current is stabilized.

[0080] Optionally, the loop current flows from a power electrode for applying a DC voltage to a ground electrode.

[0081] Reference again Figure 4 , for the measurement of nonlinear conductivity distribution, the specific process includes:

[0082] Changing the level of DC voltage;

[0083] collecting multiple surface potentials of the sample to be tested before and after changing the DC voltage level, and obtaining multiple conductivity distributions from the multiple surface potentials of the sample to be tested;

[0084] The conductivity distributions of different times are fitted to obtain the nonlinear conductivity distribution of the sample to be tested.

[0085] It can be understood that for the measurement of linear conductance distribution, there is no need to change the DC voltage.

[0086] refer to Figure 5 , which shows a schematic diagram of the structure of a device for measuring the electrical conductivity characteristics of a functional gradient material. The measuring device is suitable for implementing the above-mentioned measuring method.

[0087] In view of the fact that the specific principle or operation process of the above-mentioned measuring method has been detailed, the relevant field can easily imagine the specific structure of the measuring device from the specific principle or operation process.

[0088] However, as a more common demonstration, the inventors have noticed that this measurement method requires online scanning measurement of the surface voltage distribution of the test sample under the action of a DC voltage, which is limited by the measurement conditions of the electrostatic probe, that is, the probe should be within 2-4 mm from the sample surface. The metal high-voltage electrode installed in the center of the sample cannot pass through the sample and is higher than the plane to be measured. Otherwise, the high-voltage end and the electrostatic probe are too close, which will affect the accuracy of the measurement data and endanger the safe operation of the equipment. In addition, the thickness of the test sample is relatively thin, and it is difficult to use a ring-shaped ground electrode to press it and fix it. Based on the above considerations, the following measuring equipment is specifically proposed:

[0089] The measuring device comprises a base 401, a stage 402, a power electrode 403, and a ground electrode 404. The inner and outer diameters of a sample to be tested 400 (taking a ring shape as an example) are d and D respectively, and the thickness is h.

[0090] The power electrode 403 can be a long cylindrical structure with a smooth top cylindrical surface, a smooth area length of h, a bottom diameter of d, a threaded structure at the upper middle portion of the electrode, and a nut at the bottom, which can be connected to the output end of a high-voltage power supply.

[0091] The carrier 402 is a through cylindrical structure made of insulating material with inner and outer diameters d and D respectively and a height H. There is a thread in the through hole in the middle of the carrier 402.

[0092] The carrier 402 is used to place the sample to be tested 400, and is constrained by the outer ground electrode 404 together with the carrier 402, so as to achieve the purpose of fixing the thin layer of the sample to be tested 400;

[0093] The power electrode 403 is inserted from the bottom of the carrier 402, and is fastened to the carrier 402 through the middle thread structure, and is rotated until the smooth section on the top of the power electrode 403 completely protrudes from the surface of the carrier 402, and is inserted into the center of the sample 400 to be tested.

[0094] The main body of the grounding electrode 404 can be a ring-shaped structure with a ring width of a and a thickness of H+h. It is connected by two semicircular rings through two screws. The grounding ring is tightly fitted to the sample and the carrier by adjusting the tightening degree of the screws. A long metal connecting rod with a bottom diameter of 1 mm is welded on the side of the grounding electrode 404 for connecting to the ground wire.

[0095] The base 401 may be a cylindrical base made of insulating material, with a cylindrical groove with a depth of H+h and a diameter of D+2a on the top for placing the carrier 402, the sample to be tested 400 and the ground electrode 404;

[0096] The top surface of the base 401 has a first groove (not shown in the figure) with a width of 1 mm, which is used to place the connecting rod 405 on the grounding electrode 404. The connecting rod 405 is made of conductive metal material.

[0097] The base 401 has a second groove at the bottom (not shown in the figure), and a through hole 401a is provided at the bottom of the second groove to connect to the second groove. The power electrode 403 passes through the through hole 401a, that is, the connection point between the power electrode 403 and the high-voltage power supply output end is located in the second groove of the base 401.

[0098] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A method for determining the electrical conductivity characteristics of a functionally gradient material, characterized in that: include: Acquiring a potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from a central hole position of the sample to be tested; Determining the conductivity distribution of the sample to be tested according to the potential distribution; The conductivity distribution of the sample to be tested is determined according to the potential distribution, which is performed in the manner represented by the following formula: ； ； ； ； In the above formula, is the current density inside the test sample, is the electric field strength, is the DC conductivity, is the potential distribution, is the distance from the point on the cross section of the sample to be tested to the center, is the inner diameter of the cross section, is the outer diameter of the cross section, The radius is The potential value at The radius is The potential value at .

2. A device for determining the electrical conductivity characteristics of a functionally gradient material, characterized in that: include: An acquisition module, used for acquiring the potential distribution on the surface of the sample to be tested under the triggering of a DC voltage, wherein the DC voltage originates from the central hole position of the sample to be tested; A determination module, used to determine the conductivity distribution of the sample to be tested according to the potential distribution; The conductivity distribution of the sample to be tested is determined according to the potential distribution, which is performed in the manner represented by the following formula: ； ； ； ； In the above formula, is the current density inside the test sample, is the electric field strength, is the DC conductivity, is the potential distribution, is the distance from the point on the cross section of the sample to be tested to the center, is the inner diameter of the cross section, is the outer diameter of the cross section, The radius is The potential value at The radius is The potential value at .

3. A method for measuring the electrical conductivity characteristics of a functionally gradient material, characterized in that: include: Apply a DC voltage to the central hole of the sample to be tested; Collecting the potential distribution on the surface of the sample to be tested after applying the DC voltage, so as to obtain the conductivity distribution of the sample to be tested according to the potential distribution; According to the potential distribution, the conductivity distribution of the sample to be tested is obtained by the following formula: ； ； ； ； In the above formula, is the current density inside the test sample, is the electric field strength, is the DC conductivity, is the potential distribution, is the distance from the point on the cross section of the sample to be tested to the center, is the inner diameter of the cross section, is the outer diameter of the cross section, The radius is The potential value at The radius is The potential value at .

4. The method according to claim 3, characterized in that The measuring method further comprises: Collect loop current.

5. The method according to claim 4, characterized in that The potential distribution on the surface of the test sample after applying the DC voltage is collected after the relaxation current of the loop current is stabilized.

6. The method according to claim 4, characterized in that The loop current flows in a direction from a power supply electrode for applying a DC voltage to a ground electrode.

7. The method according to claim 3, characterized in that Collect the potential distribution on the surface of the sample to be tested after applying DC voltage, including: Changing the level of DC voltage; collecting multiple surface potentials of the sample to be tested before and after changing the DC voltage level, and obtaining multiple conductivity distributions from the multiple surface potentials of the sample to be tested; The conductivity distributions of different times are fitted to obtain the nonlinear conductivity distribution of the sample to be tested.

8. A device for measuring the electrical conductivity of a functionally gradient material, characterized in that: The measuring device is used to implement the measuring method as claimed in claim 3.

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