Withstand voltage test device for detecting cable

Abstract

The invention relates to the technical field of cable detection, in particular to a withstand voltage test device for detecting a cable, which comprises a pair of test tubes vertically arranged on an insulating support, the lower ends of the test tubes are provided with plugging rings, the plugging rings are provided with jacks for the cable to pass through, and the test tubes are further internally provided with conductive rubber sleeves and insulating sleeve tightening rings. The conductive rubber sleeve comprises an upper sleeve and a lower sleeve, a pressing face is formed between the inner wall of the upper sleeve and the inner wall of the lower sleeve, the inner diameter of the upper sleeve is matched with the outer diameter of the insulating layer, the inner diameter of the lower sleeve is matched with the outer diameter of the semi-conductive layer, and the insulating sleeve is tightly arranged on the lower sleeve in a surrounding mode. According to the invention, after the pressing surface and the end surface of the semi-conductive layer are tightly pressed, the lower sleeve is tightly sleeved by using the insulating sleeving ring, so that the levelness of a boundary is ensured, the risks of electric field concentration points and breakdown possibly caused by uneven ring cutting are avoided, meanwhile, a conical surface does not need to be processed on the cable terminal, and the manual workload is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable detection, in particular to a kind of detection cable withstand voltage test device. BACKGROUND

[0002] Cable may exist some potential insulation defects in production and manufacturing process, such as bubble, impurity, crack in insulation layer, etc., so it needs to use withstand voltage test device to carry out withstand voltage test on cable, its principle is to test the insulation reliability and resistance of cable under high voltage by applying test voltage higher than its normal operating voltage to cable.

[0003] To ensure uniform electric field distribution and prevent electric field concentration at cable terminal from causing insulation breakdown, cable terminal must be processed before test, that is, a certain length of semiconductive layer is stripped, and its end edge is polished and processed into smooth and continuous conical surface, this processing is mostly operated manually, usually using simple tools such as electrician knife and sandpaper to cut and polish cable terminal, not only the processing quality is unstable, the operation efficiency is low, but also the angle, smoothness and length of conical surface are difficult to control accurately. If the conical surface is too short, the angle is improper or the surface has scratch and step, it will form fatal electric field concentration point in test process, not only may cause innocent breakdown of cable which should be qualified under test voltage, resulting in misjudgment, but also may bury hidden danger of insulation fault in subsequent long-term operation of cable. SUMMARY

[0004] The present application aims to provide a kind of detection cable withstand voltage test device to solve the problems raised in the above background.

[0005] The present application is realized by the following technical scheme: a kind of detection cable withstand voltage test device, including a pair of test tubes vertically arranged on insulating support, the lower end of the test tube is provided with a blocking ring, the blocking ring is provided with a jack for the cable to pass through, the test tube is also provided with a conductive rubber sleeve and an insulating sleeve tight ring, the conductive rubber sleeve includes upper sleeve and lower sleeve which are arranged in upper and lower and connected, the inner wall of the upper sleeve and the inner wall of the lower sleeve form a ring platform-shaped pressure surface, the inner diameter of the upper sleeve is matched with the outer diameter of the insulation layer of the cable, the inner diameter of the lower sleeve is matched with the outer diameter of the semiconductive layer of the cable, and the insulating sleeve tight ring is arranged on the lower sleeve; The test method of the detection cable withstand voltage test device includes the following steps: Step one: stripping the two ends of the cable, so that the end is exposed from top to bottom in turn to expose the insulation layer and the semiconductive layer; Step two: the end of the cable is passed through the jack and the conductive rubber sleeve from bottom to top in turn, and the upper sleeve is sleeved on the insulation layer, and the lower sleeve is sleeved on the semiconductive layer; Step three; reverse pulling the end of the cable with the conductive rubber sleeve, so that the pressing surface is tightly pressed with the end surface of the semi-conductive layer, and then using the insulating sleeve tight ring to tightly wrap the lower sleeve on the semi-conductive layer, so that the pressing surface is kept in a tightly pressed state with the end surface of the semi-conductive layer; Step four; respectively inject water into the two test tubes, so that the water just floods the top surface of the conductive rubber sleeve, and then respectively inject silicon oil into the two test tubes; Step five; connect the core of one end of the cable to electricity, and connect the shielding layer of the other end of the cable to ground, and then test.

[0006] Optionally, the insulating sleeve tight ring is axially slidably sleeved on the lower sleeve, a plurality of clamping petals are uniformly arranged and connected on the lower end of the lower sleeve in the circumferential direction, a split seam is arranged between adjacent two clamping petals, the inner wall of each clamping petal encloses a cylindrical surface, the outer wall of each clamping petal encloses an outer conical surface, the inner wall of the lower end of the insulating sleeve tight ring is an inner conical surface, and the inner conical surface cooperates with the outer conical surface.

[0007] Optionally, it further comprises an insulating positioning sleeve, the insulating positioning sleeve is limited in the test tube through an insulating positioning frame, and the insulating positioning sleeve is movably sleeved outside the insulating sleeve tight ring, the top of the insulating positioning sleeve is connected with an upper limiting ring, a first through hole for the cable to pass through is arranged on the upper limiting ring, the outer wall of the upper sleeve is connected with a lap joint ring, the lap joint ring is lap-jointed on the top surface of the upper limiting ring, an overflow pipe is connected on the side wall of the test tube, the height of the overflow pipe is slightly higher than the top surface of the conductive rubber sleeve, and a sealing plug is arranged on the overflow pipe.

[0008] Optionally, a lap joint surface in the shape of a ring platform is formed between the outer wall of the upper sleeve and the outer wall of the lower sleeve, and a first spring is arranged between the upper limiting ring and the lap joint surface.

[0009] Optionally, a second spring is connected to the bottom surface of the upper limiting ring, the stiffness coefficient of the second spring is greater than the stiffness coefficient of the first spring, and the second spring does not contact the insulating sleeve tight ring.

[0010] Optionally, a lower limiting ring is connected to the bottom of the insulating positioning sleeve, a second through hole for the cable to pass through is arranged on the lower limiting ring, and a third spring is connected to the top surface of the lower limiting ring; in a natural state, the third spring supports the insulating sleeve tight ring without extrusion between the inner conical surface and the outer conical surface.

[0011] Optionally, the height of the insulating positioning frame is lower than the height of the insulating positioning sleeve, the outer end of the insulating positioning frame is fixedly connected with the inner wall of the test tube, and the outer wall of the insulating positioning sleeve is axially fixedly arranged with the inner end of the insulating positioning frame.

[0012] Optionally, the outer wall of the insulating positioning sleeve is circumferentially rotatably and axially fixedly arranged between the inner end of the insulating positioning frame, the side wall of the insulating positioning sleeve is provided with an inverted triangular hole, the outer wall of the insulating sleeve clamping ring is fixedly connected with a short shaft, and the short shaft is arranged in the inverted triangular hole; rotating the insulating positioning sleeve, the inclined side of the inverted triangular hole can push the short shaft to move upward together with the insulating sleeve clamping ring.

[0013] Optionally, the outer wall of the clamping piece is formed with a T-shaped guide groove, and the inner wall of the inner conical surface is provided with a T-shaped guide strip which is slidingly arranged in the T-shaped guide groove.

[0014] Optionally, the outer wall of the conductive rubber sleeve is rounded at each edge, and the radius of the round corner is not less than 2 mm.

[0015] Compared with the prior art, the present application provides a kind of detection cable withstand voltage test device, with the following beneficial effects: 1, the present application is provided with conductive rubber sleeve and insulating sleeve clamping ring in test pipe, conductive rubber sleeve includes the upper sleeve and lower sleeve formed with pressure surface, after the end surface of semiconductive layer is tightly pressed with pressure surface, insulating sleeve clamping ring is used to tighten lower sleeve, can convert the demarcation of semiconductive layer and insulating layer that may occur breakdown into the demarcation of conductive rubber sleeve and insulating layer, guarantee the levelness of demarcation, avoid the risk of electric field concentration point and breakdown that may be caused by uneven ring cutting, at the same time, without processing conical surface to cable terminal, reduce the workload of handwork; 2, the present application is designed into expansion sleeve structure between the bottom of conductive rubber sleeve and the bottom of insulating sleeve clamping ring, insulating positioning sleeve is arranged outside insulating sleeve clamping ring, first spring is arranged between insulating positioning sleeve and conductive rubber sleeve, and upper limiting ring and lap joint ring are respectively arranged on the two, in the process of pulling cable, the end surface of semiconductive layer can be tightly pressed after pressure surface, and then lower sleeve is self-clamped; After releasing hand, conductive rubber sleeve is automatically reset under the action of first spring, and the top surface of conductive rubber sleeve is kept at a fixed height and slightly lower than the height of overflow pipe, so that the water level does not need to be observed and adjusted when water is injected, and the whole operation is simple and efficient; 3, the present application is circumferentially rotatably and axially fixedly arranged, inverted triangular hole and short shaft are respectively arranged on insulating positioning sleeve and insulating sleeve clamping ring, after test, manually rotating insulating positioning sleeve can drive insulating sleeve clamping ring to move upward and separate from clamping piece, which is convenient for releasing the clamping state of insulating sleeve clamping ring, T-shaped guide groove and T-shaped guide strip are respectively arranged between clamping piece and inner conical surface, which can pull clamping piece while insulating sleeve clamping ring moves upward, so as to avoid clamping piece from being adhered to cable, thereby facilitating unwinding. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is the whole schematic view of the present application detection cable withstand voltage test device; Figure 2Assembling view of the conductive rubber sleeve, the insulating sleeve tight ring and the insulating positioning sleeve in the pressure test device for testing the cable of the present application; Figure 3 Assembling view of the conductive rubber sleeve, the insulating sleeve tight ring and the insulating positioning sleeve in the pressure test device for testing the cable of the present application; Figure 2 Axial half-section view; Figure 4 Assembling view of the conductive rubber sleeve, the insulating sleeve tight ring and the insulating positioning sleeve in the pressure test device for testing the cable of the present application;

[0017] In the figure: 1, cable; 101, shielding layer; 102, semi-conductive layer; 103, insulating layer; 104, core; 2, test tube; 201, overflow pipe; 202, water outlet pipe; 203, plugging ring; 3, insulating support; 4, insulating positioning support; 5, conductive rubber sleeve; 501, upper sleeve; 5011, first through hole; 5012, overlapping ring; 502, lower sleeve; 5021, clamping piece; 5022, cutting seam; 5023, outer conical surface; 5024, T-shaped guide groove; 503, pressing surface; 504, overlapping surface; 6, insulating sleeve tight ring; 601, inner conical surface; 602, T-shaped guide strip; 603, short shaft; 7, insulating positioning sleeve; 701, upper limiting ring; 702, lower limiting ring; 7021, second through hole; 703, inverted triangular hole; 8, first spring; 9, second spring; 10, third spring. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0019] Embodiment: Please refer to Figures 1 to 4As shown, a kind of detection cable pressure test device, including a pair of test tube 2 vertically arranged on insulating support 3, the lower end of test tube 2 is provided with the blocking ring 203, the blocking ring 203 is provided with the insertion hole for cable 1 to pass through, test tube 2 is also provided with conductive rubber sleeve 5 and insulating sleeve tight ring 6, conductive rubber sleeve 5 includes upper sleeve 501 and lower sleeve 502 distributed and connected in upper and lower, the inner wall of upper sleeve 501 and the inner wall of lower sleeve 502 form the ring platform-shaped pressing surface 503, the thickness of pressing surface 503 is equivalent to the thickness of semi-conductive layer 102, the inner diameter of upper sleeve 501 is adapted to the outer diameter of the insulating layer 103 of cable 1, the inner diameter of lower sleeve 502 is adapted to the outer diameter of semi-conductive layer 102 of cable 1, insulating sleeve tight ring 6 is arranged on lower sleeve 502, for the pressing surface 503 and semi-conductive layer 102 end face compression after tight fixing to lower sleeve 502, avoid the gap between semi-conductive layer 102 end face and pressing surface 503.Conductive rubber sleeve 5 for different specifications of cable, its inner diameter size and the thickness of pressing surface 503 can be designed and manufactured according to the standard outer diameter of cable and the thickness of semi-conductor layer, form a series of standard components.

[0020] The test method of the above-mentioned pressure test device for detecting cable, comprising the following steps: Step one: stripping the two ends of cable 1, so that the end is exposed from top to bottom in turn insulating layer 103 and semi-conductive layer 102, while the core 104 of the left end of cable 1 is exposed, and the shielding layer 101 of the right end of cable 1 is exposed; Step two: the end of cable 1 is inserted into the insertion hole and conductive rubber sleeve 5 from bottom to top in turn, and the upper sleeve 501 is sleeved on the insulating layer 103, and the lower sleeve 502 is sleeved on the semi-conductive layer 102; Step three: the end of cable 1 is pulled reversely with conductive rubber sleeve 5, so that the pressing surface 503 is tightly pressed with the end face of semi-conductive layer 102, and then the lower sleeve 502 is tightly sleeved on the semi-conductive layer 102 by using the insulating sleeve tight ring 6, so that the pressing surface 503 and the end face of semi-conductive layer 102 remain in the state of tight pressing; Step four: water is injected into the two test tubes 2 respectively, so that the water just covers the top surface of conductive rubber sleeve 5, and then silicon oil is injected into the two test tubes 2 respectively; Step five: the core 104 of the left end of cable 1 is connected to electricity, the shielding layer 101 of the right end of cable 1 is pulled to the lower side of blocking ring 203 and grounded, and then pressure test is carried out.

[0021] The embodiment does not need to process a conical surface at the terminal of the cable 1, and can directly use the above-mentioned test voltage test device of the detection cable to test after the semiconductive layer 102 is ring-cut. The end surface of the semiconductive layer 102 does not need to be kept accurate horizontal degree during the ring-cutting, and the quality of the end surface of the semiconductive layer 102 ring-cut by different proficiency of the operators does not affect the test result. The embodiment can convert the junction between the semiconductor layer and the insulating layer 103, which may have been broken down originally, into the junction between the conductive rubber sleeve 5 and the insulating layer 103. Since the top surface of the conductive rubber sleeve 5 is a fixed horizontal surface, the junction surface between the water and the silicone oil can be guaranteed to be just submerged in the top surface of the conductive rubber sleeve 5. Therefore, the embodiment can avoid the risk of electric field concentration point and breakdown caused by uneven ring-cutting, and the operation of the test voltage test device is more simple and efficient.

[0022] On the basis of the above-mentioned embodiment, the insulating sleeve ring 6 is sleeved on the lower sleeve 502 in the axial direction, the lower end of the lower sleeve 502 is uniformly provided and connected with a plurality of clamping petals 5021 in the circumferential direction, a split seam 5022 is arranged between adjacent two clamping petals 5021, the inner wall of each clamping petal 5021 is enclosed into a cylindrical surface, the outer wall of each clamping petal 5021 is enclosed into an outer conical surface 5023, the inner wall of the lower end of the insulating sleeve ring 6 is an inner conical surface 601, and the inner conical surface 601 cooperates with the outer conical surface 5023. An expansion sleeve structure is formed between the lower end of the insulating sleeve ring 6 and the lower end of the lower sleeve 502, and the expansion sleeve structure can realize the clamping action on the cable 1, that is, when the lower sleeve 502 moves upward relative to the insulating sleeve ring 6, the clamping petals 5021 are gathered and clamped on the outer wall of the cable 1 under the guidance of the inner conical surface 601, and the split seam 5022 is also extruded and sealed by the end surface between the two clamping petals 5021 gathered inward, so as to avoid the possible electric field concentration point at the edge of the split seam 5022.

[0023] Further, the above-mentioned test device for testing the pressure resistance of the cable further comprises an insulating positioning sleeve 7, which is defined in the test tube 2 by the insulating positioning frame 4 so as to keep the height and radial direction of the insulating positioning sleeve 7 unchanged, and which is movably sleeved outside the insulating sleeve clamping ring 6. The top of the insulating positioning sleeve 7 is connected with an upper limiting ring 701, and the upper limiting ring 701 is provided with a first through hole 5011 for the cable 1 to pass through. The outer wall of the upper sleeve 501 is connected with a lap joint ring 5012, and the lap joint ring 5012 is arranged on the top surface of the upper limiting ring 701. The side wall of the test tube 2 is connected with an overflow pipe 201, and the height of the overflow pipe 201 is slightly higher than the top surface of the conductive rubber sleeve 5. The overflow pipe 201 is provided with a sealing plug. Before water injection, the lap joint ring 5012 of the upper sleeve 501 is fixed at the height of the upper limiting ring 701. After water injection, the water surface can just submerge the top surface of the upper sleeve 501, and the sealing plug is inserted and then the silicone oil is injected. Since the density of the silicone oil is less than that of water and the silicone oil is not soluble in water, the injected silicone oil will naturally float on the water surface to form a stable oil-water layered interface.

[0024] In order to enable the lap joint ring 5012 to automatically adhere to the upper end surface of the upper limiting ring 701, a lap joint surface 504 in the shape of a ring platform is formed between the outer wall of the upper sleeve 501 and the outer wall of the lower sleeve 502, and the first spring 8 is arranged between the upper limiting ring 701 and the lap joint surface 504. The first spring 8 not only has the function of resetting the upper sleeve 501 to adhere the lap joint ring 5012 to the upper limiting ring 701, but also provides an elastic and variable pre-tightening force for upwardly pulling the cable 1 to tightly press the end surface of the semi-conductive layer 102 against the pressing surface 503. Compared with the direct contact between the upper limiting ring 701 and the lap joint surface 504, the problem of excessive deformation of the semi-conductive layer 102 and separation from the pressing surface 503 caused by excessive pulling can be avoided.

[0025] Further, the bottom surface of the upper limiting ring 701 is connected with a second spring 9, the stiffness coefficient of the second spring 9 is greater than the stiffness coefficient of the first spring 8, and the second spring 9 does not contact the insulating sleeve tight ring 6. The bottom of the insulating positioning sleeve 7 is connected with a lower limiting ring 702, the lower limiting ring 702 is provided with a second through hole 7021 for the cable 1 to pass through, and the top surface of the lower limiting ring 702 is connected with a third spring 10, the stiffness coefficient of the third spring 10 is less than the stiffness coefficient of the first spring 8. In the natural state, the inner conical surface 601 does not have extrusion effect on the outer conical surface 5023 when the third spring 10 supports the insulating sleeve tight ring 6. By arranging the second spring 9 which does not contact the insulating sleeve tight ring 6, it can be ensured that the pressing surface 503 is tightly pressed with the end surface of the semi-conductive layer 102 and then the lower sleeve 502 is clamped by itself when the cable 1 is pulled. When the lower sleeve 502 is clamped, the lower sleeve 502 and the insulating sleeve tight ring 6 move relatively in the axial direction, the third spring 10 supports the insulating sleeve tight ring 6 to a certain height, which can enable the first spring 8 to reset to the lap joint ring 5012 to adhere to the upper limiting ring 701, and then the insulating sleeve tight ring 6 can continue to move downward by a certain distance, so as to keep the insulating sleeve tight ring 6 always tightly sleeving the lower sleeve 502. On the basis of the above embodiment, the height of the insulating positioning frame 4 is lower than the height of the insulating positioning sleeve 7, the outer end of the insulating positioning frame 4 is fixedly connected with the inner wall of the test pipe 2, the outer wall of the insulating positioning sleeve 7 is fixedly arranged in the axial direction with the inner end of the insulating positioning frame 4, specifically, the outer wall of the insulating positioning sleeve 7 is circumferentially rotatably fixedly arranged in the axial direction, the side wall of the insulating positioning sleeve 7 is provided with a reverse triangular hole 703, the outer wall of the insulating sleeve tight ring 6 is fixedly connected with a short shaft 603, and the short shaft 603 is arranged in the reverse triangular hole 703; rotating the insulating positioning sleeve 7, the hypotenuse of the reverse triangular hole 703 can push the short shaft 603 together with the insulating sleeve tight ring 6 to move upward. After the pressure test is completed, manually rotating the insulating positioning sleeve 7 can drive the insulating sleeve tight ring 6 to move upward and separate from the clamping petals 5021, so as to conveniently release the clamping state of the insulating sleeve tight ring 6. The outer wall of the clamping petals 5021 is formed with a T-shaped guide groove 5024, and the inner wall of the inner conical surface 601 is provided with a T-shaped guide strip 602, and the T-shaped guide strip 602 is slidingly arranged in the T-shaped guide groove 5024. According to the above arrangement, the clamping petals 5021 can be pulled upward while the insulating sleeve tight ring 6 moves upward, so as to avoid the clamping petals 5021 from being adhered to the cable 1, thereby facilitating the disconnection. It should be noted that the outer wall of the conductive rubber sleeve 5 is rounded at each edge, and the radius of the rounding is not less than 2 mm. The conductive rubber sleeve 5 is rounded, which can avoid the generation of electric field concentration points and improve the safety of the test. A plurality of communication holes can be arranged on the insulating positioning sleeve 7 to communicate with the inner cavity of the insulating positioning sleeve 7, so as to facilitate water to enter and completely fill the inner cavity of the insulating positioning sleeve 7, and then the water is used to homogenize the electric charge on the conductive rubber sleeve 5 and the semi-conductive layer 102.

[0026] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A withstand voltage testing device for cables, characterized in that: The test tube (2) is vertically mounted on an insulating support (3). The lower end of the test tube (2) is provided with a sealing ring (203). The sealing ring (203) is provided with a hole for the cable (1) to pass through. The test tube (2) is also provided with a conductive rubber sleeve (5) and an insulating sleeve tightening ring (6). The conductive rubber sleeve (5) includes an upper sleeve (501) and a lower sleeve (502) that are distributed and connected vertically. A truncated ring-shaped pressing surface (503) is formed between the inner wall of the upper sleeve (501) and the inner wall of the lower sleeve (502). The inner diameter of the upper sleeve (501) is adapted to the outer diameter of the insulation layer (103) of the cable (1). The inner diameter of the lower sleeve (502) is adapted to the outer diameter of the semi-conductive layer (102) of the cable (1). The insulating sleeve tightening ring (6) is located on the lower sleeve (502). The test method of the withstand voltage test device for the test cable includes the following steps: Step 1: Strip the wires from both ends of the cable (1) so that the insulation layer (103) and the semiconductive layer (102) are exposed from top to bottom; Step 2: Pass the end of the cable (1) through the socket and the conductive rubber sleeve (5) from bottom to top, and put the upper sleeve (501) on the insulating layer (103) and the lower sleeve (502) on the semi-conductive layer (102). Step 3: Pull the end of the cable (1) and the conductive rubber sleeve (5) in opposite directions to make the pressing surface (503) and the end face of the semi-conductive layer (102) press tightly together. Then use the insulating sleeve tightening ring (6) to tighten the lower sleeve (502) onto the semi-conductive layer (102) so that the pressing surface (503) and the end face of the semi-conductive layer (102) remain in a tight pressing state. Step 4: Fill the two test tubes (2) with water until the water just submerges the top surface of the conductive rubber sleeve (5), and then fill the two test tubes (2) with silicone oil. Step 5: Connect the conductor (104) at one end of the cable (1) to power, and ground the shield (101) at the other end of the cable (1) to perform a test.

2. The withstand voltage testing device for cables according to claim 1, characterized in that: The insulating sleeve (6) is slidably mounted on the lower sleeve (502) along the axial direction. The lower end of the lower sleeve (502) is uniformly provided with multiple clips (5021) along the circumferential direction. A slit (5022) is provided between two adjacent clips (5021). The inner walls of each clip (5021) form a cylindrical surface, and the outer walls of each clip (5021) form an outer conical surface (5023). The inner wall of the lower end of the insulating sleeve (6) is an inner conical surface (601), and the inner conical surface (601) and the outer conical surface (5023) cooperate with each other.

3. The withstand voltage testing device for cables according to claim 2, characterized in that: It also includes an insulating positioning sleeve (7), which is confined inside the test tube (2) by an insulating positioning frame (4), and the insulating positioning sleeve (7) is movably fitted outside the insulating sleeve tight ring (6). An upper limit ring (701) is connected to the top of the insulating positioning sleeve (7), and the upper limit ring (701) is provided with a first through hole (5011) for the cable (1) to pass through. An overlapping ring (5012) is connected to the top of the outer wall of the upper sleeve (501), and the overlapping ring (5012) overlaps the top surface of the upper limit ring (701). An overflow pipe (201) is connected to the side wall of the test tube (2), and the height of the overflow pipe (201) is slightly higher than the top surface of the conductive rubber sleeve (5). A sealing plug is provided on the overflow pipe (201).

4. The withstand voltage testing device for cables according to claim 3, characterized in that: An overlapping surface (504) in the shape of a truncated ring is formed between the outer wall of the upper sleeve (501) and the outer wall of the lower sleeve (502), and a first spring (8) is pressed between the upper limit ring (701) and the overlapping surface (504).

5. The withstand voltage testing device for cables according to claim 4, characterized in that: The bottom surface of the upper limit ring (701) is connected to a second spring (9), the spring constant of the second spring (9) is greater than that of the first spring (8), and the second spring (9) does not contact the insulating sleeve ring (6).

6. The withstand voltage testing device for cables according to claim 3, characterized in that: The bottom of the insulating positioning sleeve (7) is connected to a lower limiting ring (702), and the lower limiting ring (702) is provided with a second through hole (7021) for the cable (1) to pass through. The top surface of the lower limiting ring (702) is connected to a third spring (10). In the natural state, when the third spring (10) supports the insulating sleeve tight ring (6), there is no squeezing effect between the inner conical surface (601) and the outer conical surface (5023).

7. The withstand voltage testing device for cables according to claim 3, characterized in that: The height of the insulating positioning frame (4) is lower than the height of the insulating positioning sleeve (7). The outer end of the insulating positioning frame (4) is fixedly connected to the inner wall of the test tube (2). The outer wall of the insulating positioning sleeve (7) and the inner end of the insulating positioning frame (4) are axially fixed together.

8. The withstand voltage testing device for cables according to claim 7, characterized in that: The outer wall of the insulating positioning sleeve (7) and the inner end of the insulating positioning frame (4) are circumferentially rotatable and axially fixed. The side wall of the insulating positioning sleeve (7) is provided with an inverted triangular hole (703). The outer wall of the insulating sleeve tight ring (6) is fixedly connected with a short shaft (603). The short shaft (603) is disposed in the inverted triangular hole (703). When the insulating positioning sleeve (7) is rotated, the hypotenuse of the inverted triangular hole (703) can push the short shaft (603) and the insulating sleeve tight ring (6) to move upward.

9. The withstand voltage testing device for cables according to claim 2, characterized in that: The outer wall of the clamping petal (5021) is formed with a T-shaped guide groove (5024), and the inner wall of the inner conical surface (601) is provided with a T-shaped guide strip (602), which is slidably disposed in the T-shaped guide groove (5024).

10. A withstand voltage testing device for cables according to any one of claims 1-9, characterized in that: The outer wall of the conductive rubber sleeve (5) is rounded at all edges, and the radius of the rounded corner is not less than 2mm.

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