Air pressure gripping cable test terminal

Abstract

The application discloses a kind of air pressure holds tightly formula cable test terminal, including outer tube body and rubber tube nested in outer tube body;The outer tube body two ends are respectively fixed with the rubber tube two ends, and the gap between rubber tube outer side wall and outer tube body inner side wall is provided, so that the closed chamber capable of accommodating insulating gas is formed between rubber tube and outer tube body;Ventilation port is provided on the outer tube body and is communicated with the closed chamber, and ventilation valve is connected on the ventilation port;Stress cone or stress tube is embedded in rubber tube.The application uses gas as insulating medium to realize cable test, without transformer oil, avoid test site pollution, reduce the test cost caused by cable end waste, and can simplify the operation of cable test process.

Description

Technical Field

[0001] This invention relates to the field of cable performance testing technology, and in particular to a pneumatic clamping cable testing terminal. Background Technology

[0002] The national standard "GB / T 12706.3—2008 Extruded Insulated Power Cables and Accessories with Rated Voltages from 1kV (Um=1.2kV) to 35kV (Um=40.5kV) Part 3: Cables with Rated Voltages of 35kV (Um=40.5kV)" stipulates that routine tests for cables should include partial discharge tests at 3.5 U0 for 5 minutes, 2.5U0 for 30 minutes, and 1.73 U0. Due to material discontinuities at the cable ends, the electric field distribution is more complex than within the cable body, particularly at the edge of the insulation shield where the electric field strength is significantly enhanced. Increased voltage can lead to corona discharge, flashover, or cable breakdown. To address these issues, medium-voltage cables undergo withstand voltage and partial discharge tests using an oil cup. Before the test, a certain length of the cable insulation shield is stripped, and the cable end is immersed in an oil cup filled with transformer oil, ensuring the oil covers the break in the cable insulation shield. The withstand voltage and partial discharge tests are then conducted.

[0003] However, the above testing methods still have some drawbacks. First, transformer oil is easily contaminated and susceptible to moisture during testing, causing the withstand voltage and partial discharge tests to fail. Therefore, frequent replacement of the transformer oil is necessary, or the oil needs to be purified and dried. The former results in waste of transformer oil, while the latter causes inconvenience to the testing process. Second, the use of transformer oil during the replacement of test samples can easily cause oil stains on the ground, making the test site inconsistent with the requirements of the environmental management system. Third, after routine cable testing, the cable ends need to be removed from the finished cable, and excessively long cable ends result in economic losses. Summary of the Invention

[0004] The purpose of this invention is to provide a pneumatic clamping cable testing terminal that simplifies the cable testing process, eliminates the need for transformer oil, avoids contamination of the test site, and reduces testing costs caused by cable end waste.

[0005] The technical solution adopted in this invention is: a pneumatic clamping cable testing terminal, comprising an outer tube and a rubber tube nested inside the outer tube;

[0006] The outer tube body is fixedly connected to the two ends of the rubber tube, and there is a gap between the outer wall of the rubber tube and the inner wall of the outer tube body, so that a closed chamber capable of accommodating insulating gas is formed between the rubber tube and the outer tube body.

[0007] The outer tube is provided with a vent that connects to the closed chamber, and a vent valve is connected to the vent.

[0008] The rubber tube is embedded with a stress cone or stress tube.

[0009] In application, this invention involves placing the end of the test cable (without its insulation shield) into a rubber tube. Insulating gas is then introduced into the sealed chamber, causing the rubber tube, along with a stress cone or stress tube, to grip the test cable. Once testing begins, the stress tube or stress cone will control the electric field distribution, ensuring that the electric field at the cable terminal is within an acceptable range.

[0010] Optionally, the pneumatic clamping cable test terminal may also include an equalizing ring for electrical connection with the conductor at the end of the cable under test. The equalizing ring can be used to prevent the influence of discharge at the cable end on the test, and its specific installation method can be found in existing technology.

[0011] Optionally, during the test, the sealed chamber is filled with an insulating gas; the insulating gas is nitrogen or dry air.

[0012] Optionally, the pneumatic clamping cable test terminal also includes a metal base and a top cover, which are fixedly installed at both ends of the outer tube and the rubber tube, respectively; cable holes are provided at the center of the base and the top cover.

[0013] Optionally, the diameter of the cable hole and the inner diameter of the rubber tube are both slightly larger than the outer diameter of the insulation layer of the cable under test. This facilitates installation and disassembly during testing.

[0014] Optionally, the outer tube body includes an insulating tube and a metal tube that are coaxially connected and have the same inner diameter, and the length of the insulating tube is much greater than the length of the metal tube; the lower end of the metal tube is fixedly connected to a base, and the upper end of the insulating tube is fixedly connected to a top cover.

[0015] The lower end of the stress tube or stress cone is higher than the upper end of the metal tube;

[0016] The vent is located on the wall of the metal pipe.

[0017] The above scheme allows for convenient installation of the vent valve via the metal tube, and minimizing the length of the metal tube ensures the insulation of the rubber tube's outer perimeter. Simultaneously, positioning the stress tube or stress cone higher than the top of the metal tube—that is, placing the stress cone or stress tube inside the insulating tube rather than the metal tube—prevents the cable end from discharging into the metal tube first, while also ensuring the electric field distribution control performance of the stress cone.

[0018] Optionally, the insulating tube is made of glass fiber impregnated with epoxy resin and coated with insulating varnish; the rubber tube is made of EPDM rubber or silicone rubber; and the high dielectric constant rubber material is made of EPDM rubber or silicone rubber.

[0019] Optionally, the periphery of each end of the rubber tube is provided with a first extension portion in an L-shape between the circumference of the rubber tube and the axial tube portion of the rubber tube. The outer end of the first extension portion is fixedly clamped between the base and the outer tube wall, or between the top cover and the outer tube wall. This ensures the sealing of the closed air chamber.

[0020] Optionally, the peripheral portions at both ends of the outer tube are respectively provided with a second extension portion in an L-shape between the outer tube body and the axial tube portion of the outer tube body, and the second extension portion is fixedly connected to the upper cover or the base.

[0021] The outer end of the first extension extends to the space between the second extension and the top cover or base. The fixed connection can be a bolted connection, such as threaded through the base / top cover, the first extension, and the second extension simultaneously, simplifying the structure.

[0022] Beneficial effects

[0023] The pneumatic clamping cable testing terminal of the present invention uses gas as the insulating medium to test the cable, avoiding the use of transformer oil, eliminating the need for transformer oil treatment, and preventing pollution of the test site; moreover, the test operation is simple and convenient, without occupying too much space at the cable end, saving the test cost incurred by removing the cable end after the test. Attached Figure Description

[0024] Figure 1 The diagram shown is a structural schematic of one embodiment of the pneumatic clamping cable test terminal of the present invention;

[0025] Figure 2 The diagram shown is a structural schematic of a second embodiment of the pneumatic clamping cable test terminal of the present invention;

[0026] In the figure, 01-Conductor of the cable under test, 02-Insulation shielding layer of the cable under test, 1-Base, 2-Top cover, 3-Insulating tube, 31-Second extension, 4-Metal tube, 41-Vent valve, 5-Rubber tube, 51-Stress cone, 52-Stress tube, 53-First extension, 6-Insulating gas, 7-Equalizing ring. Detailed Implementation

[0027] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details.

[0028] The technical concept of this invention is to use gas instead of transformer oil as the insulating medium to test cables, and at the same time, combine high dielectric constant rubber materials, stress cones or stress tubes to control the electric field distribution during the cable test.

[0029] refer to Figure 1 and Figure 2The main technical solution of the present invention is designed as follows: a pneumatic clamping cable test terminal, including an outer tube and a rubber tube 5 nested inside the outer tube;

[0030] The outer tube body is fixedly connected to the two ends of the rubber tube, and there is a gap between the outer wall of the rubber tube and the inner wall of the outer tube body, so that a closed chamber capable of accommodating insulating gas is formed between the rubber tube and the outer tube body.

[0031] The outer tube is provided with a vent that connects to the closed chamber, and a vent valve 41 is connected to the vent.

[0032] A stress cone 51 or a stress tube 52 is embedded inside the rubber tube 5. The stress cone or stress tube is coaxially arranged with the rubber tube.

[0033] In application, the end of the cable under test, with its insulation shield removed, is placed inside a rubber tube. Insulating gas is then introduced into the sealed chamber, causing the rubber tube, along with its internal stress cone or stress tube, to grip the cable under test. Once testing begins, the stress tube or stress cone will control the electric field distribution, ensuring that the electric field at the cable terminal is within an acceptable range.

[0034] Example 1

[0035] Figure 1 In the embodiment shown, the pneumatic clamping cable test terminal includes an outer tube, a rubber tube, a base 1, an upper cover 2, and an equalizing ring 7. A stress cone 51 is embedded in the rubber tube to control the electric field distribution during the test.

[0036] The base 1 and the top cover 2 are fixedly installed at the upper and lower ends of the outer tube and the rubber tube 5, respectively; cable holes are provided at the center of the base and the top cover. The diameter of the cable hole and the inner diameter of the rubber tube are slightly larger than the outer diameter of the insulation layer of the cable under test. This facilitates installation and disassembly during testing.

[0037] The outer tube body comprises an insulating tube 3 and a metal tube 4, which are coaxially connected and have the same inner diameter, with the length of the insulating tube being much greater than the length of the metal tube. The lower end of the metal tube 4 is fixed to a base 1, and the upper end of the insulating tube 3 is fixed to a top cover 2. The lower end of the stress tube or stress cone is higher than the upper end of the metal tube. A vent is located on the wall of the metal tube.

[0038] The two ends of the rubber tube are respectively provided with a first extension 51 in an L-shape between the periphery of the rubber tube and the axial tube of the rubber tube. The outer end of the first extension is fixedly clamped between the base 1 and the wall of the metal tube 4, or between the top cover 2 and the wall of the insulating tube 3. A gap is provided between the outer wall of the rubber tube and the inner wall of the outer tube, so that a closed chamber capable of accommodating the insulating gas 6 is formed between the rubber tube and the outer tube, and the sealing of the closed gas chamber is guaranteed.

[0039] Both ends of the outer tube, namely the upper end of the insulating tube 3 and the lower end of the metal tube 4, have a second extension 31 arranged in an L-shape between their peripheries and the axial tube portion of the outer tube. The second extension 31 is fixedly connected to the upper cover 2 or the base 1. The outer end of the first extension 53 extends to the space between the second extension 31 and the upper cover 2 or the base 1. The fixed connection here can be a bolt connection, or the threads can pass through the base / upper cover, the first extension, and the second extension simultaneously, simplifying the structure.

[0040] In this embodiment, the insulating tube is made of glass fiber impregnated with epoxy resin and coated with insulating varnish; the rubber tube is made of EPDM rubber or silicone rubber.

[0041] The stress cone can be achieved using existing technology. The basic principle of using a stress cone to control the electric field distribution in this embodiment is to control the electric field distribution by using geometric shape. A rubber tube embedded with a stress cone is pressed against the insulation surface of the cable end by high-pressure gas to control the electric field distribution at the cable test terminal within an acceptable range.

[0042] The test procedure using this embodiment is as follows: First, remove a certain length of the insulating shielding layer from the cable end 01 and polish it smooth. Then, place the test terminal of this embodiment onto the cable end, connect the equalizing ring to the conductor at the cable end 01, and then inflate the rubber tube by using the vent valve to tightly grip the cable. After the test, release the high-pressure gas to allow the rubber tube to retract, at which point the test terminal can be removed from the cable. The test process is convenient, simple, pollution-free, and low-cost.

[0043] Example 2

[0044] refer to Figure 2 As shown, this embodiment is based on the same inventive concept as Embodiment 1. The difference from Embodiment 1 is that a stress tube 52 is embedded in the rubber tube in this embodiment to control the electric field distribution during the test.

[0045] The stress tube can be made using existing technology. The basic principle of using a stress tube to control the electric field distribution in this embodiment is as follows: the electric field distribution is controlled by material parameters, and a rubber tube with a high dielectric constant stress tube is pressed onto the insulation surface of the cable end by high-pressure insulating gas to control the electric field distribution of the cable test terminal within an acceptable range.

[0046] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A gas pressure grip type cable test terminal, characterized by, Includes an outer tube and a rubber tube nested inside the outer tube; The outer tube body is fixed to the two ends of the rubber tube, and there is a gap between the outer wall of the rubber tube and the inner wall of the outer tube body, so that a closed chamber capable of accommodating insulating gas is formed between the rubber tube and the outer tube body. The outer tube is provided with a vent that connects to the closed chamber, and a vent valve is connected to the vent. The rubber tube is embedded with a stress cone or stress tube; the inner diameter of the rubber tube is larger than the outer diameter of the insulation layer of the cable under test. By introducing insulating gas into the closed chamber, the rubber tube, along with the stress cone or stress tube, can be tightly wrapped around the cable under test. The outer tube body includes an insulating tube and a metal tube that are coaxially connected and have the same inner diameter, and the length of the insulating tube is greater than the length of the metal tube; the metal tube is connected to the lower end of the insulating tube; the lower end of the stress tube or stress cone is higher than the upper end of the metal tube; the vent is provided on the wall of the metal tube.

2. The gas pressure grip-type cable test terminal according to claim 1, characterized by, It also includes an equalizing ring for electrical connection with the conductor at the end of the cable under test.

3. The gas pressure grip-type cable test terminal according to claim 1, characterized by, During testing, the sealed chamber is filled with an insulating gas; the insulating gas is nitrogen or dry air.

4. The gas pressure grip-type cable test terminal according to claim 1, characterized by, It also includes a metal base and a top cover, which are fixedly installed at both ends of the outer tube and the rubber tube, respectively; cable holes are provided at the center of the base and the top cover.

5. The gas pressure grip-type cable test terminal according to claim 4, characterized by The diameter of the cable hole is larger than the outer diameter of the insulation layer of the cable under test.

6. The gas pressure gripper cable test terminal according to claim 4 or 5, characterized in that The two ends of the rubber tube are respectively provided with a first extension in an L-shape between the peripheral portion and the axial tube portion of the rubber tube. The outer end of the first extension is fixedly clamped between the base and the outer tube wall, or between the top cover and the outer tube wall.

7. The gas pressure grip-type cable test terminal according to claim 6, characterized by The outer tube body has a second extension portion in an L-shape between the peripheral portions at both ends and the axial tube portion of the outer tube body, and the second extension portion is fixedly connected to the top cover or the base. The outer end of the first extension extends to the space between the second extension and the top cover or base.

8. The gas pressure cable grip termination of claim 1 wherein, The insulating tube is made of glass fiber impregnated with epoxy resin and coated with insulating varnish; the rubber tube is made of EPDM rubber or silicone rubber.

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