Unshielded cable partial discharge testing device
By designing a shieldless cable partial discharge test device, using dielectric troughs and conductive dielectrics such as steel balls, copper particles or graphite particles, the problems of cumbersome sample preparation and poor encapsulation of conductive dielectrics are solved, and more accurate detection of insulation defects and reducing test errors are achieved.
Patent Information
- Application Number
- CN202420977181.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-07
- Publication Date
- 2025-03-04
- Estimated Expiration
- 2034-05-07
AI Technical Summary
The existing local discharge test methods for unshielded cables are cumbersome to prepare samples, and the conductive dielectric is poorly wrapped, which cannot accurately reflect the level of cable insulation defects, resulting in large test errors.
A partial discharge test device for unshielded cables is designed, using a granular conductive dielectric in the dielectric material trough, and the shielded cable is buried in the conductive dielectric, and connected to the conductive dielectric and cable through the test line, stripping the insulating layer for connection, and using conductive dielectrics such as steel balls, copper particles or graphite particles to improve conductivity and covering properties.
The sample production is simplified, and the conductive dielectric has better cladding properties on the insulating layer, which can more accurately reflect the insulation defect level of the cable, reducing the test error.
Smart Images
Figure CN222561723U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of cable performance detection, and in particular relates to a partial discharge test device for an unshielded cable. Background Art
[0002] Partial discharge is a phenomenon in which voltage breaks down or passes through an insulator. Unlike complete insulation breakdown, the insulation layer of the cable remains basically intact during partial discharge and still exists as a resistor, but may be slightly damaged. Partial discharge may occur at the interface between the conductor and the insulator, or inside the insulator, or along the outer surface of the insulator. There are four main types of cable partial discharge: (1) between the conductor and the insulation, (2) within the insulation gap, (3) between the insulation layers, and (4) between the insulation and the shield.
[0003] Industry specifications such as GJB973B and ASTMD 3032-2010 have provisions for shielded specimens, which are more applicable to coaxial cables or shielded cables. ASTMD 3032-2010 stipulates the sample preparation requirements for unshielded cables, and stipulates that the partial discharge level of 5pC is used as the basis for the determination of PDIV / PDEV. Specifically, the sample needs to be prepared first. There are two ways. The first is to wrap the wire around the iron core rod with ten times the outer diameter of the insulation ten times, and use tape to stick the wire to the iron core. The two ends of the wire should extend out of the iron core so that the two ends of the conductor can be connected together and connected to the high-voltage end of the test equipment (wire-core rod); the second is to stick the wire on a flat metal plate with tape, bend the two ends of the wire to keep it away from the plate and can be connected together and connected to the high-voltage end of the equipment (wire-metal plate).
[0004] During the test, the first step is to immerse the end of the sample in the insulating oil until the connection is at least 6.4mm deep. The measurement should be carried out after no bubbles are generated in the insulating oil. The second step is that the power supply of the test equipment should be between 48-62Hz. The third step is that when PDEV is less than or equal to 3kV, the maximum voltage increase rate shall not exceed 50V / S; when PDEV is greater than 3kV, the maximum voltage increase rate shall not exceed 100V / S. The fourth step is to increase the voltage according to the above-mentioned voltage increase method until a discharge of more than 5pC occurs, and the voltage at this time is recorded as PDIV. The voltage is reduced at the same rate until the discharge disappears, and the voltage at this time is recorded as PDEV. The fifth step is that when necessary, measurements can be carried out at different discharge amounts in a vacuum chamber simulating low pressure or at a temperature higher than room temperature.
[0005] The above-mentioned wire-metal plate or wire-core rod testing method not only requires cumbersome sample preparation, but also has poor wrapping properties of the conductive medium for the insulation layer, and cannot accurately reflect the insulation defect level of the unshielded cable itself, resulting in large test errors. Utility Model Content
[0006] The utility model aims to provide a non-shielded cable partial discharge test device to solve the problem of large error in the test result.
[0007] The utility model is a non-shielded cable partial discharge test device implemented as follows:
[0008] A partial discharge test device for unshielded cables, comprising:
[0009] A dielectric material tank, in which a granular conductive medium is placed, and an unshielded cable is buried in the conductive medium;
[0010] A partial discharge tester, wherein one test line of the partial discharge tester is connected to the conductive medium, and another test line is connected to one end of the unshielded cable.
[0011] Furthermore,
[0012] The insulation layer of one end of the unshielded cable connected to the corresponding test line is stripped, and the stripping length b is in the range of 5-10 mm.
[0013] Furthermore, the conductive medium is a steel ball.
[0014] Furthermore, the diameter d of the steel ball is less than 1 mm.
[0015] Furthermore, the conductive medium is copper particles or graphite particles.
[0016] Furthermore, the conductivity of the conductive medium is σ≥1.45×10 7 S / m.
[0017] Furthermore, two ends of the unshielded cable extend out from the conductive medium, and the extending length l is ≥ 100 mm.
[0018] Furthermore, the length L of the medium trough ranges from 650 to 2000 mm.
[0019] Furthermore, the depth h of the conductive medium is ≥ 60 mm.
[0020] Furthermore, the depth of the medium trough is H≥h+200mm.
[0021] After adopting the above technical solution, the utility model has the following beneficial effects:
[0022] The utility model has a simple overall structure, and the adapted sample is easy to prepare. The conductive medium has better coverage of the outer insulation layer of the unshielded cable, and can more comprehensively and accurately reflect the insulation defect level of the cable itself, with small test errors. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The utility model is further described below in conjunction with the accompanying drawings and embodiments.
[0024] Figure 1 It is a schematic diagram of a partial discharge test device for unshielded cables according to Embodiment 1 of the present utility model;
[0025] In the figure: dielectric material tank 1, partial discharge tester 2, conductive medium 3, test line 4, unshielded cable 5. DETAILED DESCRIPTION
[0026] In order to make the purpose, technical solution and advantages of the implementation of the utility model clearer, the technical solution in the implementation of the utility model will be clearly and completely described below in conjunction with the drawings in the implementation of the utility model. Obviously, the described implementation is a part of the implementation of the utility model, not all of the implementations. Based on the implementation of the utility model, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.
[0028] Example 1
[0029] like Figure 1 As shown, a partial discharge test device for an unshielded cable includes a dielectric material trough 1 and a partial discharge tester 2. A granular conductive medium 3 is placed inside the dielectric material trough 1, and an unshielded cable 5 is buried in the conductive medium 3; one of the test lines 4 of the partial discharge tester 2 is connected to the conductive medium 3, and the other test line 4 is connected to one end of the unshielded cable 5.
[0030] In this embodiment, the unshielded cable 5 is the sample to be tested.
[0031] In order to ensure that the unshielded cable 5 , ie the conductor of the sample to be tested, is connected to the test line 4 , the insulation layer of one end of the unshielded cable 5 connected to the corresponding test line 4 is stripped, and the stripping length b is in the range of 5-10 mm.
[0032] Specifically, the test line 4 corresponding to the high voltage end of the partial discharge tester 2 is connected to the end of the unshielded cable 5 , and the test line 4 corresponding to the ground end is connected to the conductive medium 3 .
[0033] In order to ensure the conductivity of the conductive medium 3, the conductive medium 3 is a steel ball.
[0034] The diameter d of the steel ball is less than 1 mm, so that the conductive medium 3 can fully contact with the unshielded cable 5, that is, the sample to be measured, to ensure the accuracy of the measurement result.
[0035] The conductivity of the conductive medium 3 is σ≥1.45×10 7 S / m. The higher the conductivity of the conductive medium 3, the more accurate the test result. In this embodiment, steel balls are selected because they have excellent conductivity and high cost performance.
[0036] In order to ensure that the sample to be tested will not have creepage with the conductive medium 3 during the voltage boost process, both ends of the unshielded cable 5 extend out of the conductive medium 3, and the extended length l is ≥ 100 mm.
[0037] In order to meet the length requirement of the sample to be tested, the length L of the medium trough 1 is in the range of 650-2000 mm.
[0038] Specifically, the difference between the length L of the medium trough 1 and the length of the sample to be tested is at least 200 mm.
[0039] In order to allow the sample to be completely and adequately buried in the conductive medium 3 and ensure good contact, the depth h of the conductive medium 3 is ≥ 60 mm.
[0040] In order to meet the test requirements, the depth of the medium trough 1 is H≥h+50mm.
[0041] Preferably, the dielectric tank 1 is made of insulating material, such as resin with insulating properties.
[0042] During the test, the prepared sample to be tested is placed in a low pressure box, and one test line 4 of the partial discharge tester 2, i.e., its high voltage end, is connected to the end of the sample to be tested, and the other test line 4, i.e., the ground end, is inserted into the conductive medium 3. At this time, the partial discharge test can be performed. The specific test process and precautions can be referred to the records in GJB973B and ASTMD3032-2010.
[0043] The test device recorded in the utility model has a simple structure, and the sample to be tested is easy to prepare. The conductive medium 3 has good wrapping property for the insulating layer, and can more comprehensively and accurately reflect the insulation defect level of the unshielded cable 5 itself. The test result has higher accuracy and smaller error.
[0044] The test was conducted using the wire-metal plate, wire-mandrel and the test device of this embodiment, i.e., the steel ball groove, in ASTM D3032-2010. The measured PDEV value (in V) is the partial discharge extinction voltage. The specific test data are shown in the following table:
[0045]
[0046] In this table, the data in the same row are the test results of the same unshielded cable under the same test conditions and measured by three test methods. The smaller the PDEV value, the higher the detection level of insulation defects. Then, from the data in the above table, it can be seen that the test device described in this application has a smaller test error and more accurate test results.
[0047] Example 2
[0048] On the basis of Example 1, this embodiment further provides a partial discharge test device for an unshielded cable, the structure of which is substantially the same as that of Example 1, except that the conductive medium 3 is copper particles or graphite particles.
[0049] Compared with steel beads, copper particles and graphite particles have better conductivity and more accurate test results.
[0050] The conductive medium 3 is not limited to the three disclosed in Embodiment 1 and Embodiment 2, and satisfies the conductivity σ≥1.45×10 7 Any conductive material of S / m can be used.
[0051] Based on the above ideal embodiments of the utility model, the relevant staff can make various changes and modifications without deviating from the technical concept of the utility model through the above description. The technical scope of the utility model is not limited to the content of the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A partial discharge test device for unshielded cables, characterized in that: include A dielectric material tank (1), wherein a granular conductive medium (3) is placed in the dielectric material tank (1), and an unshielded cable (5) is buried in the conductive medium (3); A partial discharge tester (2), wherein one test line (4) of the partial discharge tester (2) is connected to the conductive medium (3), and another test line (4) is connected to one end of the unshielded cable (5).
2. The unshielded cable partial discharge test device according to claim 1, characterized in that: The insulation layer of one end of the unshielded cable (5) connected to the corresponding test line (4) is stripped, and the stripping length b is in the range of 5-10 mm.
3. The unshielded cable partial discharge test device according to claim 1, characterized in that: The conductive medium (3) is a steel ball.
4. The unshielded cable partial discharge test device according to claim 3, characterized in that: The diameter d of the steel ball is less than 1 mm.
5. The unshielded cable partial discharge test device according to claim 1, characterized in that: The conductive medium (3) is copper particles or graphite particles.
6. The unshielded cable partial discharge test device according to claim 1, characterized in that: The conductivity of the conductive medium (3) is σ≥1.45×10 7 S / m.
7. The unshielded cable partial discharge test device according to claim 1, characterized in that: Both ends of the unshielded cable (5) extend out from the conductive medium (3), and the extending length l is ≥ 100 mm.
8. The unshielded cable partial discharge test device according to claim 1, characterized in that: The length L of the medium trough (1) is in the range of 650-2000 mm.
9. The unshielded cable partial discharge test device according to claim 1, characterized in that: The depth h of the conductive medium (3) is ≥ 60 mm.
10. The unshielded cable partial discharge testing device according to claim 9, characterized in that: The depth of the medium trough (1) is H≥h+200mm.