Cable buffer layer radial resistivity testing device and method

Abstract

The invention discloses a cable buffer layer radial resistivity testing device, comprising a DC power supply, an ammeter, a voltmeter, an upper hollow outer electrode, an upper inner electrode, a lower hollow outer electrode, a lower inner electrode, an upper insulating pad, a lower insulating pad and a pressure block. A cable buffer layer sample is placed between the upper hollow outer electrode, the upper inner electrode and the lower hollow outer electrode, the lower inner electrode. The pressure block applies pressure to the sample. The DC power supply, the ammeter, the upper hollow outer electrode, the cable buffer layer sample and the lower hollow outer electrode are connected to form a test current loop. The cable buffer layer sample is connected to the voltmeter, the upper inner electrode and the lower inner electrode to form a test voltage loop. The DC power supply provides a test voltage, the voltmeter is used to test the voltage between the electrodes, the ammeter is used to test the current between the electrodes, the radial resistance is obtained according to Ohm's law, and a more accurate radial resistivity is finally obtained by using the relationship between resistance and resistivity.

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 radial resistivity of a cable buffer layer. Background Art

[0002] High-voltage cross-linked polyethylene 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 shielding surfaces. Analysis of the cause of the failure revealed a change in the resistance of the cable buffer layer. Because national standards have not yet established methods for measuring the resistivity of the cable buffer layer, measurement methods are not standardized in projects, resulting in inaccurate measurement data. The cable buffer layer is a semi-conductive material. Conventional voltammetry does not distinguish between voltage and current loops when measuring the cable buffer layer resistance. The contact resistance causes a large measurement error, which 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 radial resistivity of a cable buffer layer, so as to achieve the purpose of quickly and accurately testing the radial resistivity of a cable buffer layer.

[0004] To achieve this purpose, the cable buffer layer radial resistivity testing device designed by the present invention includes a DC power supply, an ammeter, a voltmeter, an upper hollow outer electrode, an upper inner electrode, a lower hollow outer electrode, a lower inner electrode, an upper insulating pad, a lower insulating pad and a pressure block, wherein one end of the DC power supply is connected to the upper hollow outer electrode, the other end of the DC power supply is connected to one end of the ammeter, the other end of the ammeter is connected to the lower hollow outer electrode, the two ends of the voltmeter are respectively connected to the upper inner electrode and the lower inner electrode, and the cable buffer layer sample is located between the upper hollow outer electrode and the lower hollow outer electrode. The upper inner electrode penetrates into the upper hollow outer electrode and is fixed to the upper hollow outer electrode, and an insulating layer is provided between the upper inner electrode and the upper hollow outer electrode, the bottom end of the upper inner electrode is fitted with the cable buffer layer sample, the lower inner electrode penetrates into the lower hollow outer electrode and is fixed to the lower hollow outer electrode, and an insulating layer is provided between the lower inner electrode and the lower hollow outer electrode, the top end of the lower inner electrode is fitted with the cable buffer layer sample, the bottom end of the lower hollow outer electrode is placed on the lower insulating pad, an upper insulating pad is provided on the upper hollow outer electrode, and a pressure block capable of applying pressure to the upper insulating pad is provided on the top of the upper insulating pad.

[0005] Beneficial effects of the present invention:

[0006] 1. The present invention can quickly achieve accurate alignment of the upper and lower electrodes, flexibly apply pressure, and make testing more convenient.

[0007] 2. The present invention separates the test voltage loop from the current loop, thereby avoiding the test error caused by contact resistance and obtaining the radial resistivity of the cable buffer layer more accurately, which is suitable for promotion and use in this field. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0009] Figure 2 This is a schematic diagram of the cable buffer layer structure of the present invention;

[0010] Figure 3 A top view of the upper hollow outer electrode portion of the present invention;

[0011] Figure 4 It is a top view of the lower hollow outer electrode portion of the present invention.

[0012] Among them, 1—DC power supply, 2—ammeter, 3—voltmeter, 4—guide column, 5—upper hollow outer electrode, 6—upper inner electrode, 7—lower hollow outer electrode, 8—lower inner electrode, 9—upper insulating pad, 10—lower insulating pad, 11—pressure block, 12—hanging buckle, 13—conductor rod, 14—cable buffer layer sample, 15—insulating layer, 16—fluffy cotton, 17—water-blocking powder, 18—semi-conductive non-woven fabric. 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 radial resistivity test device designed by the present invention is as follows: Figure 1 、 3As shown in Figure 4, it includes a DC power supply 1, an ammeter 2, a voltmeter 3, an upper hollow outer electrode 5, an upper inner electrode 6, a lower hollow outer electrode 7, a lower inner electrode 8, an upper insulating spacer 9, a lower insulating spacer 10 and a pressure block 11, wherein one end of the DC power supply 1 is connected to the upper hollow outer electrode 5, the other end of the DC power supply 1 is connected to one end of the ammeter 2, the other end of the ammeter 2 is connected to the lower hollow outer electrode 7, the two ends of the voltmeter 3 are respectively connected to the upper inner electrode 6 and the lower inner electrode 8, and the cable buffer layer sample 14 is located between the upper hollow outer electrode 5 and the lower hollow outer electrode 7. The upper inner electrode 6 penetrates into the upper hollow outer electrode 5, and there is an insulating layer 15 between the upper inner electrode 6 and the upper hollow outer electrode 5, the bottom end of the upper inner electrode 6 is in contact with the cable buffer layer sample 14, the lower inner electrode 8 penetrates into the lower hollow outer electrode 7, and there is an insulating layer 15 between the lower inner electrode 8 and the lower hollow outer electrode 7, the top end of the lower inner electrode 8 is in contact with the cable buffer layer sample 14, the bottom end of the lower hollow outer electrode 7 is placed on the lower insulating pad 10, and an upper insulating pad 9 is arranged on the upper hollow outer electrode 5, and a pressure block 11 that can apply pressure to the upper insulating pad 9 is arranged on the top of the upper insulating pad 9.

[0015] In the above technical solution, it further includes a guide column 4 , which passes through the upper insulating spacer 9 and the lower insulating spacer 10 , and the upper insulating spacer 9 can slide up and down on the guide column 4 .

[0016] In the above technical solution, it also includes a conductor rod 13, which is vertically fixed on the top of the upper insulating pad 9. The conductor rod 13 vertically passes through the pressure block 11, and the pressure block 11 can slide up and down on the conductor rod 13. A hanging buckle 12 is provided on the top of the pressure block 11.

[0017] In the above technical solution, the material of the upper hollow outer electrode 5 , the upper inner electrode 6 , the lower hollow outer electrode 7 and the lower inner electrode 8 is preferably copper.

[0018] The top of the upper inner electrode 6 passes through the pressure block 11 and is connected to the corresponding end of the voltmeter 3. The upper hollow outer electrode 5 and the lower hollow outer electrode 7 are both hollow cylindrical electrodes, and the upper hollow outer electrode 5 and the lower hollow outer electrode 7 are coaxially arranged.

[0019] In the above technical solution, the pressure block 11 includes multiple sub-pressure blocks, each of which is independent of each other. The applied pressure is determined according to the number of sub-pressure blocks. Each sub-pressure block can apply a pressure of 1 kg. The number of sub-pressure blocks is determined according to experimental requirements.

[0020] In the above technical solution, the cable buffer layer sample 14 can be in the shape of a disc, and is composed of a three-layer structure of fluffy cotton 16, water-blocking powder 17, and semi-conductive non-woven fabric 18, with a typical diameter of 25 mm. The semi-conductive non-woven fabric 18 is located on one side of the upper hollow outer electrode 5 and the upper inner electrode 6, as shown in FIG. Figure 2 shown.

[0021] A method for testing radial resistivity of a cable buffer layer comprises the following steps:

[0022] Step 1: Place the cable buffer layer sample 14 between the upper hollow outer electrode 5 and the lower hollow outer electrode 7;

[0023] Step 2: The pressure block 11 applies a preset pressure to the cable buffer layer sample 14 through the upper insulating spacer 9. The DC power supply 1, the ammeter 2, the upper hollow outer electrode 5, the cable buffer layer sample 14 and the lower hollow outer electrode 7 are connected to form a test current circuit. The cable buffer layer sample 14, the upper inner electrode 6, the lower inner electrode 8 and the voltmeter 3 are connected to form a test voltage circuit.

[0024] Step 3: Provide a test voltage through a DC power supply 1, use a voltmeter 3 to test the inter-electrode voltage between the upper inner electrode 6 and the lower inner electrode 8, use an ammeter 2 to test the electrode current flowing through the upper hollow outer electrode 5 and the lower hollow outer electrode 7, obtain the radial resistance value of the cable buffer layer sample 14 according to Ohm's law, and obtain the radial resistivity using the relationship between the radial resistance value and the resistivity.

[0025] In the above technical solution, the pressure block 11 slides downward along the conductor rod 13 and applies pressure to the upper insulating spacer 9 .

[0026] In the above technical solution, the upper insulating spacer 9 slides downward along the guide column 4 under the pressure of the pressure block 11 , thereby applying pressure to the upper hollow outer electrode 5 and further applying a preset pressure to the cable buffer layer sample 14 .

[0027] In the above technical solution, the radial resistance of the cable buffer layer sample 14 is obtained according to Ohm's law. That is, the radial resistance R of the cable buffer layer sample 14 is the voltage U detected by the voltmeter 3 divided by the current I detected by the ammeter 2. Then, the radial resistivity ρ of the cable buffer layer sample 14 is:

[0028]

[0029] Where L is the thickness of the sample, and S is the surface area of the sample between the upper inner electrode and the lower inner electrode.

Claims

1. A method for testing the radial resistivity of a cable buffer layer based on a cable buffer layer radial resistivity testing device, characterized in that: The cable buffer layer radial resistivity testing device comprises a DC power supply (1), an ammeter (2), a voltmeter (3), an upper hollow outer electrode (5), an upper inner electrode (6), a lower hollow outer electrode (7), a lower inner electrode (8), an upper insulating pad (9), a lower insulating pad (10) and a pressure block (11), wherein one end of the DC power supply (1) is connected to the upper hollow outer electrode (5), the other end of the DC power supply (1) is connected to one end of the ammeter (2), the other end of the ammeter (2) is connected to the lower hollow outer electrode (7), the two ends of the voltmeter (3) are respectively connected to the upper inner electrode (6) and the lower inner electrode (8), the cable buffer layer sample (14) is located between the upper hollow outer electrode (5) and the lower hollow outer electrode (7), the upper inner electrode (6) penetrates into the upper hollow outer electrode (5) and is fixed to the upper hollow outer electrode (5), and the upper inner electrode (6) is fixed to the upper hollow outer electrode There is an insulating layer (15) between the electrodes (5), the bottom end of the upper inner electrode (6) is in contact with the cable buffer layer sample (14), the lower inner electrode (8) penetrates the lower hollow outer electrode (7) and is fixed to the lower hollow outer electrode (7), and there is an insulating layer (15) between the lower inner electrode (8) and the lower hollow outer electrode (7), the top end of the lower inner electrode (8) is in contact with the cable buffer layer sample (14), and the bottom end of the lower hollow outer electrode (7) is placed on the lower insulating layer. An upper insulating pad (9) is arranged on the upper hollow outer electrode (5) and a pressure block (11) is arranged on the top of the upper insulating pad (9) to apply pressure to the upper insulating pad (9); the cable buffer layer sample (14) is in the shape of a disc and is composed of a three-layer structure of fluffy cotton (16), water-blocking powder (17), and semi-conductive non-woven fabric (18), and the semi-conductive non-woven fabric (18) is located on one side of the upper hollow outer electrode (5) and the upper inner electrode (6); It is characterized by comprising the following steps: Step 1: placing a cable buffer layer sample (14) between an upper hollow outer electrode (5) and a lower hollow outer electrode (7); Step 2: The pressure block (11) applies a preset pressure to the cable buffer layer sample (14) through the upper insulating spacer (9); the DC power supply (1), the ammeter (2), the upper hollow outer electrode (5), the cable buffer layer sample (14) and the lower hollow outer electrode (7) are connected to form a test current loop; the cable buffer layer sample (14), the upper inner electrode (6), the lower inner electrode (8) and the voltmeter (3) are connected to form a test voltage loop; Step 3: Providing a test voltage through a DC power supply (1), using a voltmeter (3) to measure the inter-electrode voltage between the upper inner electrode (6) and the lower inner electrode (8), using an ammeter (2) to measure the electrode current flowing through the upper hollow outer electrode (5) and the lower hollow outer electrode (7), obtaining the radial resistance value of the cable buffer layer sample (14) according to Ohm's law, and obtaining the radial resistivity using the relationship between the radial resistance value and the resistivity; In step 2, the pressure block (11) slides downward along the conductor rod (13) and applies pressure to the upper insulating spacer (9); In step 2, the upper insulating spacer (9) slides downward along the guide column (4) under the pressure of the pressure block (11), thereby applying pressure to the upper hollow outer electrode (5), and then applying a preset pressure to the cable buffer layer sample (14).

2. The cable buffer layer radial resistivity testing method according to claim 1, characterized in that: It also includes a guide column (4), which passes through an upper insulating spacer (9) and a lower insulating spacer (10), and the upper insulating spacer (9) can slide up and down on the guide column (4).

3. The cable buffer layer radial resistivity testing method according to claim 1, characterized in that: It also includes a conductor rod (13), which is vertically fixed on the top of the upper insulating pad (9), and the conductor rod (13) vertically penetrates the pressure block (11), and the pressure block (11) can slide up and down on the conductor rod (13).

4. The cable buffer layer radial resistivity testing method according to claim 3, characterized in that: A hanging buckle (12) is provided on the top of the pressure block (11).

5. The cable buffer layer radial resistivity testing method according to claim 1, characterized in that: The top of the upper inner electrode (6) passes through the pressure block (11) and is connected to the corresponding end of the voltmeter (3).

6. The cable buffer layer radial resistivity testing method according to claim 1, characterized in that: The upper hollow outer electrode (5) and the lower hollow outer electrode (7) are both hollow cylindrical electrodes, and the upper hollow outer electrode (5) and the lower hollow outer electrode (7) are coaxially arranged.

7. The cable buffer layer radial resistivity testing method according to claim 1, characterized in that: The pressure block (11) comprises a plurality of sub-pressure blocks, each of which is independent of the others.

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