Cable buffer layer axial resistivity test device and test method

Abstract

The present invention discloses a device for testing the axial resistivity of a cable buffer layer. The device comprises a first voltage test electrode, a second voltage test electrode, a first current test electrode, and a second current test electrode, which are embedded in and fixed to a lower insulating pressing block. The first current test electrode is located outside the first voltage test electrode, and the second current test electrode is located outside the second voltage test electrode. A cable buffer layer sample is located between the upper insulating pressing block and the lower insulating pressing block. The first voltage test electrode, the second voltage test electrode, the first current test electrode, and the second current test electrode can contact the semi-conductive non-woven fabric layer of the cable buffer layer sample. One end of a DC power supply is connected to the first current test electrode via an ammeter, and the other end of the DC power supply is connected to the second current test electrode. One end of a voltmeter is connected to the first voltage test electrode, and the other end of the voltmeter is connected to the second voltage test electrode. The present invention can quickly and accurately test the axial resistivity of a cable buffer layer.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical testing, and in particular to a device and method for testing the axial resistivity of a cable buffer layer. Background Art

[0002] High-voltage XLPE cables have been used in my country for over 30 years and are now largely domestically produced. Over 10,000 kilometers of high-voltage cables are buried underground each year. Over the past decade, during the migration, rewiring, and autopsy of high-voltage cables, a large number of "burning" and "white spots" have been found on the buffer layer and insulation shield surfaces. Analysis of the cause of the failures revealed a change in the resistance of the cable buffer layer. Because national standards have yet to define a method for measuring the resistivity of the cable buffer layer, measurement methods are inconsistent across projects, resulting in inaccurate data. The cable buffer layer is a semi-conductive material. Conventional voltammetry, when measuring the resistance of the cable buffer layer, does not distinguish between voltage and current loops. The contact resistance causes significant measurement errors and cannot reflect the true resistivity of the cable buffer layer. Summary of the Invention

[0003] The purpose of the present invention is to provide a device and method for testing the axial resistivity of a cable buffer layer, which can quickly and accurately test the axial resistivity of a cable buffer layer.

[0004] To achieve this purpose, the cable buffer layer axial resistivity testing device designed by the present invention is characterized in that it includes an upper insulating compact, a lower insulating compact, a first voltage testing electrode, a second voltage testing electrode, a first current testing electrode, a second current testing electrode, an ammeter, a voltmeter and a DC power supply, wherein the first voltage testing electrode, the second voltage testing electrode, the first current testing electrode and the second current testing electrode are embedded in and fixed in the lower insulating compact, the first current testing electrode is located outside the first voltage testing electrode, and the second current testing electrode is located outside the second voltage testing electrode;

[0005] The cable buffer layer sample is located between the upper insulating block and the lower insulating block. The first voltage test electrode, the second voltage test electrode, the first current test electrode, and the second current test electrode can contact the semi-conductive non-woven fabric layer of the cable buffer layer sample. One end of the DC power supply is connected to the first current test electrode through an ammeter, and the other end of the DC power supply is connected to the second current test electrode. One end of the voltmeter is connected to the first voltage test electrode, and the other end of the voltmeter is connected to the second voltage test electrode.

[0006] Beneficial effects of the present invention:

[0007] The present invention separates a test voltage loop from a current loop through an upper insulating pressing block, a lower insulating pressing block, a first voltage test electrode, a second voltage test electrode, a first current test electrode, and a second current test electrode, thereby avoiding test errors caused by contact resistance and rapidly and accurately measuring the axial resistivity of the cable buffer layer. Furthermore, the pressure applied to the cable buffer layer during the test is adjustable, and an axial resistivity parameter that is closer to the usage state of the cable buffer layer can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a structural schematic diagram of the present invention;

[0009] Figure 2 Schematic diagram of the structure of the upper insulating pressing block when viewed from above;

[0010] Figure 3 Schematic diagram of the top view of the lower insulating pressing block;

[0011] Figure 4 Schematic diagram of the cable buffer layer sample.

[0012] Among them, 1—upper insulating pressure block, 2—lower insulating pressure block, 3—first voltage test electrode, 3.1—first voltage test spare electrode, 4—second voltage test electrode, 4.1—second voltage test spare electrode, 5—first current test electrode, 5.1—first current test spare electrode, 6—second current test electrode, 6.1—second current test spare electrode, 7—insulating pressure block, 8—fixing rod, 9—hanging buckle, 10—guide column, 11—ammeter, 12—voltmeter, 13—DC power supply, 14—pressure test module, 15—cable buffer layer sample, 16—fluffy cotton layer, 17—water-blocking powder, 18—semi-conductive non-woven fabric layer. DETAILED DESCRIPTION

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0014] The cable buffer layer axial resistivity test device designed by the present invention is as follows: Figures 1 to 4 As shown, it includes an upper insulating pressing block 1, a lower insulating pressing block 2, a first voltage test electrode 3, a second voltage test electrode 4, a first current test electrode 5, a second current test electrode 6, an ammeter 11, a voltmeter 12 and a DC power supply 13, wherein the first voltage test electrode 3, the second voltage test electrode 4, the first current test electrode 5, and the second current test electrode 6 are embedded in and fixed in the lower insulating pressing block 2, the first current test electrode 5 is located on the outside of the first voltage test electrode 3, and the second current test electrode 6 is located on the outside of the second voltage test electrode 4;

[0015] The cable buffer layer sample 15 is located between the upper insulating block 1 and the lower insulating block 2. The first voltage test electrode 3, the second voltage test electrode 4, the first current test electrode 5, and the second current test electrode 6 can contact the semi-conductive non-woven fabric layer 18 of the cable buffer layer sample 15. One end of the DC power supply 13 is connected to the first current test electrode 5 through the ammeter 11, and the other end of the DC power supply 13 is connected to the second current test electrode 6. One end of the voltmeter 12 is connected to the first voltage test electrode 3, and the other end of the voltmeter 12 is connected to the second voltage test electrode 4.

[0016] In the above technical solution, the upper insulating block 1 and the lower insulating block 2 are both cylindrical, and the cable buffer layer sample 15 is a cable buffer layer disc with a typical diameter of 25 mm. It is composed of a three-layer structure of a fluffy cotton layer 16, a water-blocking powder 17, and a semi-conductive non-woven fabric layer 18.

[0017] In the above technical solution, an insulating pressure block 7 is installed at the top of the upper insulating pressure block 1. This insulating pressure block 7 is fixedly connected to the top of the upper insulating pressure block 1 via a fixing rod 8. The insulating pressure block 7 can be composed of multiple submodules, each of which is independent and can be flexibly installed and removed. Typically, each submodule can apply a pressure of 1 kg.

[0018] In the above technical solution, a hanging buckle 9 is fixed to the top of the insulating pressure block 7. The hanging buckle 9 is used to quickly load or remove the upper insulating pressure block 1 and the insulating pressure block 7 during testing.

[0019] The above technical solution also includes a guide post 10, which passes through the lower insulating block 2 and the upper insulating block 1, and the upper insulating block 1 can slide up and down on the guide post 10. There are two guide posts 10 on the left and right, and the two guide posts 10 are used to ensure that the first voltage test electrode 3, the second voltage test electrode 4, the first current test electrode 5, and the second current test electrode 6 quickly and accurately contact the corresponding test areas of the cable buffer layer specimen 15.

[0020] In the above technical solution, a pressure test module 14 is provided between the lower insulating block 2 and the cable buffer layer sample 15. The pressure test module 14 is used to measure the pressure on the cable buffer layer sample 15 and can be an optical fiber sensor or a piezoresistive sheet sensor.

[0021] In the above technical solution, the upper insulating pressing block 1 and the lower insulating pressing block 2 are both cylindrical electrodes.

[0022] In the above technical solution, the upper insulating pressing block 1 is embedded with and fixed with a first voltage test standby electrode 3.1, a second voltage test standby electrode 4.1, a first current test standby electrode 5.1, and a second current test standby electrode 6.1. The first voltage test standby electrode 3.1 is coaxial with the first voltage test electrode 3, the second voltage test standby electrode 4.1 is coaxial with the second voltage test electrode 4, the first current test electrode 5 is coaxial with the first current test standby electrode 5.1, and the second current test electrode 6 is coaxial with the second current test standby electrode 6.1. When a fault occurs in the electrodes in the lower insulating pressing block 2, the positions of the upper insulating pressing block 1 and the lower insulating pressing block 2 can be swapped, and the wiring method of the lower insulating pressing block 2 can be used to connect the first voltage test standby electrode 3.1, the second voltage test standby electrode 4.1, the first current test standby electrode 5.1, and the second current test standby electrode 6.1 to the ammeter 11, the voltmeter 12, and the DC power supply 13.

[0023] A method for testing the axial resistivity of a cable buffer layer using the above device comprises the following steps:

[0024] Step 1: Place the cable buffer layer sample 15 between the upper insulating block 1 and the lower insulating block 2;

[0025] Step 2: The insulating pressure block 7 applies a preset pressure to the cable buffer layer sample 15 through the upper insulating pressure block 1. The DC power supply 13, the ammeter 11, the first current test electrode 5, the cable buffer layer sample 15, and the second current test electrode 6 form a test current loop;

[0026] The voltmeter 12, the first voltage test electrode 3, the cable buffer layer sample 15, and the second voltage test electrode 4 constitute a test voltage circuit;

[0027] Step 3: A test voltage is provided by a DC power supply 13. According to Ohm's law, the axial resistance R of the cable buffer layer sample 15 is obtained using the voltage U detected by the voltmeter 12, the current I detected by the ammeter 11, and the distance S between the electrodes, thereby obtaining the axial resistivity ρ of the cable buffer layer sample 15.

[0028] In the present technical solution, the first current testing electrode 5 , the first voltage testing electrode 3 , the second voltage testing electrode 4 and the second current testing electrode 6 are on the same horizontal line in the same plane, and the intervals S therebetween are S1 , S2 , S3 and S4 respectively.

[0029] Axial resistivity ρ:

[0030]

[0031] If S1=S2=S3=S4=S, then the axial resistivity ρ is:

[0032] ρ=2πSU / I

[0033] In step 2 of the above technical solution, the upper insulating pressing block 1 slides downward along the guide column 10 under the pressure of the insulating pressure applying block 7 , thereby applying a preset pressure to the cable buffer layer sample 15 .

[0034] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A method for testing the axial resistivity of a cable buffer layer using a cable buffer layer axial resistivity testing device, characterized in that: The cable buffer layer axial resistivity testing device comprises an upper insulating pressing block (1), a lower insulating pressing block (2), a first voltage testing electrode (3), a second voltage testing electrode (4), a first current testing electrode (5), a second current testing electrode (6), an ammeter (11), a voltmeter (12) and a DC power supply (13), wherein the first voltage testing electrode (3), the second voltage testing electrode (4), the first current testing electrode (5) and the second current testing electrode (6) are embedded in and fixed in the lower insulating pressing block (2), the first current testing electrode (5) is located outside the first voltage testing electrode (3), and the second current testing electrode (6) is located outside the second voltage testing electrode (4); The cable buffer layer sample (15) is located between the upper insulating pressing block (1) and the lower insulating pressing block (2); the first voltage test electrode (3), the second voltage test electrode (4), the first current test electrode (5), and the second current test electrode (6) can contact the semi-conductive non-woven fabric layer (18) of the cable buffer layer sample (15); one end of the DC power supply (13) is connected to the first current test electrode (5) through the ammeter (11); the other end of the DC power supply (13) is connected to the second current test electrode (6); one end of the voltmeter (12) is connected to the first voltage test electrode (3); and the other end of the voltmeter (12) is connected to the second voltage test electrode (4); An insulating pressure block (7) is provided at the top of the upper insulating pressure block (1), and the insulating pressure block (7) is fixedly connected to the top of the upper insulating pressure block (1) via a fixing rod (8). The insulating pressure block (7) is composed of a plurality of submodules, each of which is independent of each other. A pressure test module (14) is provided between the lower insulating pressure block (2) and the cable buffer layer sample (15); A first voltage test standby electrode (3.1), a second voltage test standby electrode (4.1), a first current test standby electrode (5.1), and a second current test standby electrode (6.1) are embedded and fixed in the upper insulating pressing block (1); the first voltage test standby electrode (3.1) is coaxial with the first voltage test electrode (3), the second voltage test standby electrode (4.1) is coaxial with the second voltage test electrode (4), the first current test electrode (5) is coaxial with the first current test standby electrode (5.1), and the second current test electrode (6) is coaxial with the second current test standby electrode (6.1); when a fault occurs in the electrode in the lower insulating pressing block (2), the positions of the upper insulating pressing block (1) and the lower insulating pressing block (2) are swapped, and the first voltage test standby electrode (3.1), the second voltage test standby electrode (4.1), the first current test standby electrode (5.1), and the second current test standby electrode (6.1) are connected to the ammeter (11), the voltmeter (12), and the DC power supply (13) according to the wiring method of the lower insulating pressing block (2); The cable buffer layer sample (15) is a cable buffer layer disc, which is composed of a three-layer structure of a fluffy cotton layer (16), a water-blocking powder (17), and a semi-conductive non-woven fabric layer (18); The invention also includes a guide post (10), wherein the guide post (10) passes through the lower insulating pressing block (2) and the upper insulating pressing block (1), and the upper insulating pressing block (1) can slide up and down on the guide post (10). The guide post (10) has two left and right guide posts. The two guide posts (10) are used to ensure that the first voltage test electrode (3), the second voltage test electrode (4), the first current test electrode (5), and the second current test electrode (6) accurately contact corresponding test areas of the cable buffer layer sample (15); The steps include: Step 1: placing a cable buffer layer sample (15) between an upper insulating pressing block (1) and a lower insulating pressing block (2); Step 2: The insulating pressure block (7) applies a preset pressure to the cable buffer layer sample (15) through the upper insulating pressure block (1), and the DC power supply (13), the ammeter (11), the first current test electrode (5), the cable buffer layer sample (15), and the second current test electrode (6) form a test current loop; The voltmeter (12), the first voltage test electrode (3), the cable buffer layer sample (15), and the second voltage test electrode (4) constitute a test voltage circuit; Step 3: A test voltage is provided by a DC power supply (13), and the axial resistance R of the cable buffer layer sample (15) is obtained according to Ohm's law using the voltage U detected by the voltmeter (12), the current I detected by the ammeter (11), and the distance S between the electrodes, thereby obtaining the axial resistivity ρ of the cable buffer layer sample (15); The first current test electrode (5), the first voltage test electrode (3), the second voltage test electrode (4) and the second current test electrode (6) are on the same horizontal line in the same plane, and the spacings S therebetween are S1, S2, S3 and S4 respectively; Axial resistivity ρ: If S1=S2=S3=S4=S, then the axial resistivity ρ is: ρ=2πSU / I.

2. The method for testing the axial resistivity of a cable buffer layer using the cable buffer layer axial resistivity testing device according to claim 1, characterized in that: A hanging buckle (9) is fixed to the top of the insulating pressure block (7).

3. The method for testing the axial resistivity of a cable buffer layer using the cable buffer layer axial resistivity testing device according to claim 1, characterized in that: The upper insulating pressing block (1) and the lower insulating pressing block (2) are both cylindrical electrodes.

4. The method for testing the axial resistivity of a cable buffer layer using the cable buffer layer axial resistivity testing device according to claim 1, characterized in that: In step 2, the upper insulating pressing block (1) slides downward along the guide column (10) under the pressure of the insulating pressure applying block (7), thereby applying a preset pressure to the cable buffer layer sample (15).

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