Electrode breakdown testing device and method for easily-rolled girdling insulation test piece

Abstract

The invention discloses an electrode breakdown test device and method for an easy-to-roll girdling insulation test piece. The device comprises an insulation frame, a metal bearing platform, an insulation pressing plate and a ball electrode. The metal bearing platform is mounted on the insulating frame; and the girdling insulating test piece is arranged on the metal bearing platform. And the insulating pressing plate is provided with an open hole and is pressed on the girdling insulating test piece on the metal bearing platform. The ball electrode is mounted on the insulating frame, penetrates through the open hole and is pressed on the girdling insulating test piece on the metal bearing platform, so that the metal bearing platform is grounded and voltage is applied to the ball electrode, and the girdling insulating test piece is subjected to a breakdown test. According to the device disclosed by the invention, the girdling insulation test piece is pressed among the metal bearing platform, the insulation pressing plate and the ball electrode while a breakdown test is performed on the girdling insulation test piece, so that curling deformation caused by residual stress of the girdling insulation test piece is prevented.

Description

Technical Field

[0001] The invention relates to the field of solid insulation electrical performance testing, and in particular to an electrode breakdown testing device and method for an easy-to-roll ring-cut insulation test piece. Background Art

[0002] Under the background of the demand for localization and diversification of power cable insulation materials, the performance of insulation materials for power cables represented by cross-linked polyethylene and polypropylene needs to be improved. With the continuous iteration and upgrading of material performance, its electrical performance still needs to be further studied. At present, the basic electrical performance tests of insulation materials such as cross-linked polyethylene and polypropylene, such as electrical breakdown strength, mainly rely on the method of ball-to-ball electrode discharge in insulating oil. The performance test and verification of power cable insulation materials usually requires the insulation materials to be processed into cable samples. Due to the high cost of cable manufacturing in cable manufacturers and limited funding, the current performance test and verification method for power cable insulation materials is to process the insulation materials into low-voltage model cables, such as 10kV and 35kV. The insulation layer of low-voltage model cables is relatively thin, and it is impossible to obtain a large area of ​​test specimens by flat cutting and cross cutting. The electrical breakdown strength test of the insulation layer usually requires a large area of ​​insulation samples.

[0003] The solution is to perform ring cutting on the insulation layer of the model cable to obtain a larger insulating test piece. The ring slices are easily curled due to residual stress, which causes inconvenience and unnecessary measurement errors in the electrical breakdown strength test. At the same time, when the electrical breakdown strength test of the insulating ring slices is performed under high temperature conditions (for example, 90°C), the high-temperature insulating oil causes the insulating test piece to deform, and the test piece becomes softer and thinner. When the test position is changed after a single breakdown, the thickness of the test piece at the test position is unknown, and there is a risk of burns to the operator when changing the test position, which seriously affects the test accuracy, work efficiency and safety. Summary of the invention

[0004] The present invention provides an electrode breakdown test device and method for an easy-to-roll ring-cut insulating test piece, which can prevent the curling deformation caused by the residual stress of the ring-cut insulating test piece.

[0005] An embodiment of the present invention provides an electrode breakdown test device for an easy-to-roll ring-cut insulating test piece, comprising an insulating frame, a metal support, an insulating pressure plate and a ball electrode. The metal support is mounted on the insulating frame, and a ring-cut insulating test piece is arranged on the metal support. The insulating pressure plate has an opening, and the insulating pressure plate is pressed on the ring-cut insulating test piece on the metal support. The ball electrode is mounted on the insulating frame, and the ball electrode is pressed on the ring-cut insulating test piece on the metal support through the opening, so as to realize a breakdown test on the ring-cut insulating test piece by grounding the metal support and applying a voltage to the ball electrode.

[0006] In some embodiments, the number of openings is multiple, the number of ball electrodes is less than or equal to the number of openings, and each ball electrode passes through an opening.

[0007] In some of the embodiments, the ball electrode can be mounted on the insulating frame so as to be elastically movable in a direction perpendicular to the metal support, so that the ball electrode is pressed onto the ring-cut insulating test piece on the metal support under the action of elasticity.

[0008] In some of the embodiments, the ball electrode has an electrode rod, which passes through the electrode rod through-hole of the insulating frame in a direction perpendicular to the metal base, and the side of the electrode rod has a boss. The outer part of the electrode rod is provided with a compression spring, which is compressed between the insulating frame and the boss, so that the ball electrode can be elastically mounted on the insulating frame in a direction perpendicular to the metal base.

[0009] In some of the embodiments, the insulating pressing plate has ridges on all sides, the ridges protrude toward the metal support, and the ridges are arranged around the top of the metal support so as to enclose the annular insulating test piece on the metal support through the ridges.

[0010] In some embodiments, the easy-to-roll ring-cut insulating test piece electrode breakdown test device further includes an L-shaped clamp and a clamp fixing nut. The short rod section of the L-shaped clamp is inserted into the pressure plate through hole of the insulating pressure plate, and the long rod section of the L-shaped clamp passes through the clamp through hole of the insulating frame. The clamp fixing nut is threadedly installed on the long rod section of the L-shaped clamp passing through the insulating frame, so as to fix the insulating pressure plate to the insulating frame through the L-shaped clamp and the clamp fixing nut.

[0011] In some embodiments, the easy-to-roll ring-cut insulating test piece electrode breakdown test device further includes a base fixing bolt. The screw of the base fixing bolt passes through the bolt through-hole of the insulating frame and is threadedly installed in the blind hole of the metal base, so that the metal base is fixedly installed on the insulating frame through the base fixing bolt.

[0012] In some embodiments, the metal cap comprises a cap plate and a cap column, the cap column is supported below the cap plate, and a grounding connection hole is provided on a side of the cap column, so as to ground the metal cap through the grounding connection hole.

[0013] The embodiment of the present invention provides an electrode breakdown test method for an easy-to-roll ring-cut insulating test piece, comprising the following steps: placing the ring-cut insulating test piece on a metal support, pressing an insulating pressing plate on the ring-cut insulating test piece on the metal support, and passing a ball electrode through an opening of the insulating pressing plate and pressing it on the ring-cut insulating test piece on the metal support. The metal support is grounded. A voltage is applied to the ball electrode on the ring-cut insulating test piece to perform a breakdown test.

[0014] In some embodiments, the ball electrode is passed through the opening of the insulating pressure plate and pressed onto the ring-cut insulating test piece on the metal support, including: a plurality of ball electrodes are passed through the plurality of openings of the insulating pressure plate one by one, and pressed onto the ring-cut insulating test piece on the metal support. A voltage is applied to the ball electrodes on the ring-cut insulating test piece to perform a breakdown test, including: a voltage is applied to one ball electrode on the ring-cut insulating test piece to perform multiple breakdown tests, and the remaining ball electrodes on the ring-cut insulating test piece are grounded.

[0015] According to an embodiment of the present invention, a device for electrode breakdown testing of an easy-to-roll ring-cut insulating test piece is provided, comprising an insulating frame, a metal support, an insulating pressure plate and a ball electrode. The metal support is installed on the insulating frame, and a ring-cut insulating test piece is arranged on the metal support. The insulating pressure plate has an opening, and the insulating pressure plate is pressed on the ring-cut insulating test piece on the metal support. The ball electrode is installed on the insulating frame, and the ball electrode is pressed on the ring-cut insulating test piece on the metal support through the opening, so as to realize a breakdown test on the ring-cut insulating test piece by grounding the metal support and applying a voltage to the ball electrode. The device of the present invention not only realizes the breakdown test on the ring-cut insulating test piece, but also enables the ring-cut insulating test piece to be pressed between the metal support, the insulating pressure plate and the ball electrode, thereby preventing the curling deformation caused by the residual stress of the ring-cut insulating test piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a schematic diagram of the structure of the device in the embodiment of the present invention;

[0018] Figure 2 It is a structural schematic diagram of an insulating frame in an embodiment of the present invention;

[0019] Figure 3 It is a structural schematic diagram of a metal support in an embodiment of the present invention;

[0020] Figure 4 It is a structural schematic diagram of the fixing bolts of the platform in the embodiment of the present invention;

[0021] Figure 5 It is a schematic structural diagram of an insulating pressing plate in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the structure of an L-shaped card member in an embodiment of the present invention;

[0023] Figure 7This is a schematic diagram of the structure of a clamp fixing nut in an embodiment of the present invention;

[0024] Figure 8 It is a schematic diagram of the structure of the ball electrode and the compression spring in the embodiment of the present invention;

[0025] Fig. 9 It is a structural schematic diagram of the device in the first embodiment of the present invention;

[0026] Fig.10 It is a structural schematic diagram of the device in the second embodiment of the present invention;

[0027] Fig.11 It is a schematic diagram of the structure of the device in the third embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] See also Figure 1-11 The embodiment of the present invention provides an electrode breakdown test device for an easily rolled ring-cut insulation test piece, specifically a device for performing a multi-electrode electrical breakdown strength test on an easily rolled cable insulation ring-cut insulation test piece. The device includes an insulation frame 1, a metal base 2, a base fixing bolt 3, an insulation pressure plate 4, an L-shaped clamp 5, a clamp fixing nut 6, a ball electrode 7 and a compression spring 8.

[0030] The insulating frame 1 is used as an insulating base. The insulating frame 1 is a box structure with openings on the front and back sides, and the side panels extend below the bottom plate. A pair of bolt through holes 101 are drilled on the bottom plate of the insulating frame 1, which can be round holes for the base fixing bolts 3 to pass through, so as to fix the metal base 2 and the insulating frame 1 through the base fixing bolts 3. A pair of clamp through holes 102 are drilled on the bottom plate of the insulating frame 1, which can be round holes for the L-shaped clamp 5 to pass through, so as to fix the insulating pressure plate 4 and the insulating frame 1 through the L-shaped clamp 5. A plurality of electrode rod through holes 103 are drilled on the top plate of the insulating frame 1, which can be five, for the ball electrode 7 to pass through, so as to install the ball electrode 7 on the insulating frame 1. The arrangement of the five electrode rod through holes 103 is as follows: four electrode rod through holes 103 are respectively arranged at the four corners of the square structure, and the remaining electrode rod through hole 103 is arranged at the center of the square structure. The thickness of the top plate of the insulating frame 1 is greater than that of the side plate and the bottom plate, so as to improve the stability of the ball electrode 7 inserted into the top plate.

[0031] The metal support 2 is used to place the ring-cut insulating test piece and serve as a ground electrode. The metal support 2 has a support plate 201 and a support column 202. The support plate 201 is a horizontally arranged square thin plate. The ring-cut insulating test piece is set on the support plate 201. The support column 202 is a vertically arranged cylinder. The support column 202 is supported under the support plate 201. The bottom surface of the support column 202 has two blind holes 203 for threaded installation of the support fixing bolts 3, so that the support column 202 is fixedly installed on the bottom plate of the insulating frame 1 through the support fixing bolts 3. The side of the support column 202 has a ground wire connection hole 204, which can be a round hole for the ground wire to be passed through and connected, so as to ground the metal support 2 through the ground wire connection hole 204.

[0032] The cap fixing bolt 3 is used to fix the metal cap 2 on the insulating frame 1. The screw of the cap fixing bolt 3 passes through the bolt through hole 101 on the bottom plate of the insulating frame 1 and is threadedly installed in the blind hole 203 on the bottom surface of the cap column 202, so that the metal cap 2 is fixedly installed on the bottom plate of the insulating frame 1 through the cap fixing bolt 3.

[0033] The insulating pressing plate 4 is used to fix the ring-cut insulating test piece on the metal support 2. The insulating pressing plate 4 is arranged horizontally. The insulating pressing plate 4 is pressed on the ring-cut insulating test piece on the metal support 2. The above arrangement prevents the curling deformation caused by the residual stress of the ring-cut insulating test piece at a lower temperature through the pressing effect of the insulating pressing plate 4.

[0034] The insulating platen 4 is drilled with an opening 401, which may be a large diameter circular hole for the ball electrode 7 to pass through. The above arrangement enables the breakdown test point for obtaining thickness data to be located at the center of the opening 401 of the insulating platen 4. The center line of the opening 401 extends vertically. The number of the openings 401 is multiple, such as five, and the five openings 401 are concentrically arranged with the electrode rod through-hole 103 on the top plate of the insulating frame 1. The arrangement of the five openings 401 is as follows: four openings 401 are respectively arranged at the four corners of the square structure, and the remaining opening 401 is arranged at the center of the square structure.

[0035] The insulating pressing plate 4 has ridges 402 on all sides, the ridges 402 protrude toward the metal base 2, and the ridges 402 are arranged around the base plate 201 on the top of the metal base 2, so as to enclose the ring-cut insulating test piece on the metal base 2 through the ridges 402. Two of the ridges 402 arranged opposite to each other have connecting ears 403, which can be semicircular structures, and the connecting ears 403 are drilled with pressing plate through holes 404, which can be round holes, for L-shaped clamps 5 to pass through, so as to fix the insulating pressing plate 4 to the insulating frame 1 through the L-shaped clamps 5.

[0036] The L-shaped clamp 5 is used to fix the insulating platen 4 to the insulating frame 1. There are two L-shaped clamps 5, and each L-shaped clamp 5 is arranged in a one-to-one correspondence with each platen through-hole 404. The short rod section 501 of the L-shaped clamp 5 is arranged horizontally, and the long rod section 502 is arranged vertically, and the long rod section 502 is arranged below the short rod section 501. The short rod section 501 of the L-shaped clamp 5 is inserted into the platen through-hole 404 on the connecting ear 403 of the insulating platen 4. The long rod section 502 of the L-shaped clamp 5 passes through the clamp through-hole 102 on the bottom plate of the insulating frame 1.

[0037] The clamp fixing nut 6 is used to fasten the L-shaped clamp 5 so as to fix the insulating plate 4 to the insulating frame 1. There are two clamp fixing nuts 6, and each clamp fixing nut 6 is provided in a one-to-one correspondence with each L-shaped clamp 5. The center line of the clamp fixing nut 6 extends vertically. The clamp fixing nut 6 is threadedly installed on the long rod section 502 of the L-shaped clamp 5 passing through the insulating frame 1, so as to fix the insulating plate 4 to the insulating frame 1 through the L-shaped clamp 5 and the clamp fixing nut 6.

[0038] The ball electrode 7 is used to be pressed onto the ring-cut insulating test piece on the metal support 2 and serve as a test voltage application electrode. The ball electrode 7 is arranged vertically. The ball electrode 7 passes through the electrode rod through-hole 103 on the top plate of the insulating frame 1. The ball electrode 7 passes through the opening 401 and is pressed onto the ring-cut insulating test piece on the metal support 2. The number of ball electrodes 7 is less than or equal to the number of openings 401. The number of ball electrodes 7 can be one. The number of ball electrodes 7 can also be multiple, such as two, three, four, or five. Each ball electrode 7 passes through an opening 401, that is, one ball electrode 7 is arranged corresponding to one opening 401. The above arrangement realizes a breakdown test on the ring-cut insulating test piece by grounding the metal support 2 and applying voltage to the ball electrode 7.

[0039] The ball electrode 7 has a metal ball 701 and an electrode rod 702. The metal ball 701 is arranged at the lower end of the electrode rod 702. The metal ball 701 is fixed to the electrode rod 702 by a thread. The electrode rod 702 passes through the electrode rod through hole 103 on the top plate of the insulating frame 1 in the vertical direction. The lower end side of the electrode rod 702 has a boss 703.

[0040] The compression spring 8 is used to press the ball electrode 7 onto the ring-cut insulating test piece on the metal support 2 under the action of elasticity. The compression spring 8 is sleeved on the outside of the electrode rod 702, and the compression spring 8 is pressed between the top plate of the insulating frame 1 and the boss 703, so that the ball electrode 7 can be installed on the top plate of the insulating frame 1 in a vertically elastic manner, so that the ball electrode 7 is pressed onto the ring-cut insulating test piece on the metal support 2 under the action of elasticity. The above-mentioned setting applies pressure toward the metal support 2 to the ball electrode 7 through the compression spring 8 installed between the boss 703 of the electrode rod 702 and the top plate of the insulating frame 1, so as to increase the static friction force of the ring-cut insulating test piece placed on the metal support 2. When the insulating test piece is deformed and thinned under high temperature conditions, the elastic force of the compression spring 8 and the self-weight of the ball electrode 7 continuously compress it to ensure the accuracy of the breakdown test data.

[0041] The device of the present invention fixes the ring-cut insulation test piece on the metal support 2 through multiple electrodes and an insulation pressure plate 4, and by applying voltage to different electrodes in turn, multiple breakdown strength tests can be performed after a single fixation, and the test is highly accurate. The device of the present invention is suitable for overcoming the curling deformation of the ring-cut test piece of the cable insulation layer and improving the test efficiency under high temperature test conditions.

[0042] An embodiment of the present invention provides a method for testing the electrode breakdown of an easy-to-roll ring-cut insulating test piece, comprising the following steps:

[0043] (1) The ring-cut insulating test piece to be subjected to the electrical breakdown test is placed on the metal support 2, the insulating pressing plate 4 is pressed onto the ring-cut insulating test piece on the metal support 2, and the ball electrode 7 is passed through the opening 401 of the insulating pressing plate 4 and pressed onto the ring-cut insulating test piece on the metal support 2.

[0044] In the above steps, the plurality of ball electrodes 7 can be passed through the plurality of openings 401 of the insulating pressing plate 4 in a one-to-one correspondence, and pressed onto the ring-cut insulating test piece on the metal support 2 .

[0045] (2) The metal support 2 is grounded. A voltage is applied to the ball electrode 7 on the ring-cut insulation test piece to perform a breakdown test.

[0046] In the above steps, voltage may be applied to one ball electrode 7 on the ring-cut insulating test piece to perform multiple breakdown tests, and the remaining ball electrodes 7 on the ring-cut insulating test piece are grounded.

[0047] In the present invention, after the ring-cut insulating test piece is placed on the metal base 2, the test piece is fixed by the insulating pressure plate 4, the ball electrode 7 and the compression spring 8. At relatively low temperatures, the pressing action of the insulating pressure plate 4 can prevent the curling deformation caused by the residual stress of the ring-cut insulating test piece. When the insulating test piece is deformed under high temperature conditions, the elastic force of the compression spring 8 and the deadweight of the ball electrode 7 continue to press the test piece to ensure the accuracy of the breakdown test data. In the present invention, a plurality of ball electrodes 7 are installed on the test piece at the same time. After the ring-cut insulating test piece is installed once, multiple breakdown tests can be quickly performed by applying voltage to a single ball electrode 7 rod (the remaining ball electrodes 7 are grounded). The test work efficiency is high, and the thickness change caused by the change of the breakdown point of the test piece due to frequent replacement of the breakdown test point in conventional single breakdown devices is reduced, resulting in inaccurate breakdown test data. Under high temperature conditions, the number of times the test operator contacts the high-temperature insulating oil is reduced to avoid the risk of burns. The following is an illustration in conjunction with an embodiment:

[0048] See also Fig. 9 In the first embodiment, the number of the ball electrode 7 is one, and the ball electrode 7 passes through the electrode rod through-hole 103 at the center of the square structure, and passes through the corresponding opening 401 to be pressed onto the ring-cut insulating test piece on the metal support 2.

[0049] See also Fig.10 In the second embodiment, the number of the ball electrodes 7 is two, and the two ball electrodes 7 respectively pass through the two electrode rod through-holes 103 at the two corners of the square structure, and respectively pass through the two corresponding openings 401 to be pressed onto the ring-cut insulating test piece on the metal support 2.

[0050] See also Fig.11 In the third embodiment, the number of the ball electrodes 7 is four, and the four ball electrodes 7 respectively pass through the four electrode rod through-holes 103 at the four corners of the square structure, and respectively pass through the four corresponding openings 401 to be pressed onto the ring-cut insulating test piece on the metal support 2.

[0051] See also Figure 1 In the fourth embodiment, the number of the ball electrodes 7 is five, and the five ball electrodes 7 respectively pass through the five electrode rod through-holes 103 and the five openings 401 and are pressed onto the ring-cut insulating test piece on the metal support 2.

[0052] Table 1 Comparison of Examples

[0053]

[0054]

[0055] It can be seen from Table 1 that: according to the comparison of different embodiments, the smaller the number of ball electrodes 7 installed simultaneously on the device of the present invention, the thicker the insulating test piece that can be used for electrical breakdown testing; conversely, after the ring-cut insulating test piece is installed once, the more breakdown tests can be performed continuously, and the higher the work efficiency.

[0056] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An easy-to-roll ring-cut insulating test piece electrode breakdown test device, characterized in that: include: Insulation frame; A metal support, mounted on the insulating frame, with a ring-cut insulating test piece arranged on the metal support; An insulating pressing plate having an opening, wherein the insulating pressing plate is pressed on the ring-cut insulating test piece on the metal support platform; A ball electrode is mounted on the insulating frame. The ball electrode passes through the opening and is pressed onto the ring-cut insulating test piece on the metal support. By grounding the metal support and applying voltage to the ball electrode, a breakdown test is performed on the ring-cut insulating test piece.

2. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: The number of the openings is multiple; the number of the ball electrodes is less than or equal to the number of the openings, and each of the ball electrodes passes through one of the openings.

3. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: The ball electrode can be installed on the insulating frame in an elastic manner along the direction perpendicular to the metal support, so that the ball electrode is pressed on the ring-cut insulating test piece on the metal support under the action of elasticity.

4. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 3, characterized in that: The ball electrode has an electrode rod, which passes through the electrode rod through-hole of the insulating frame along the direction perpendicular to the metal base. The side of the electrode rod has a boss, and the outer part of the electrode rod is provided with a compression spring, which is compressed between the insulating frame and the boss, so that the ball electrode can be elastically mounted on the insulating frame along the direction perpendicular to the metal base.

5. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: The insulating pressing plate has ridges on all sides, the ridges protrude toward the metal support platform, and the ridges are arranged around the top of the metal support platform so as to enclose the annularly cut insulating test piece on the metal support platform through the ridges.

6. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: Also includes: An L-shaped clamp, whose short rod section is inserted into the clamping plate through-hole of the insulating clamp, and whose long rod section passes through the clamping plate through-hole of the insulating frame; A clamp fixing nut is threadedly mounted on the long rod section of the L-shaped clamp passing through the insulating frame, so that the insulating pressing plate is fixedly connected to the insulating frame through the L-shaped clamp and the clamp fixing nut.

7. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: Also includes: The base fixing bolt has a screw rod which passes through the bolt through-hole of the insulating frame and is threadedly installed in the blind hole of the metal base, so that the metal base can be fixedly installed on the insulating frame through the base fixing bolt.

8. The electrode breakdown test device for easy-to-roll ring-cut insulating test pieces according to claim 1, characterized in that: The metal cap has a cap plate and a cap column, the cap column is supported below the cap plate, and a side portion of the cap column has a grounding connection hole so as to ground the metal cap through the grounding connection hole.

9. A method for testing the electrode breakdown of an easy-to-roll ring-cut insulating test piece, characterized in that: The following steps are involved: Placing the ring-cut insulating test piece on a metal support, pressing an insulating pressing plate on the ring-cut insulating test piece on the metal support, and passing a ball electrode through an opening of the insulating pressing plate and pressing it on the ring-cut insulating test piece on the metal support; The metal support is grounded; and a voltage is applied to the ball electrode on the ring-cut insulating test piece to perform a breakdown test.

10. The method for testing the electrode breakdown of an easy-to-roll ring-cut insulating test piece according to claim 9, characterized in that: The ball electrode is passed through the opening of the insulating pressing plate and is pressed onto the ring-cut insulating test piece on the metal support, comprising: Passing a plurality of ball electrodes through the plurality of openings of the insulating pressing plate one by one in correspondence, and pressing them onto the ring-cut insulating test piece on the metal support; Applying voltage to the ball electrode on the ring-cut insulating test piece to perform a breakdown test includes: A voltage is applied to one of the ball electrodes on the ring-cut insulating test piece to perform multiple breakdown tests, and the remaining ball electrodes on the ring-cut insulating test piece are grounded.

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