A megavolt-level high-voltage vacuum insulation stack capable of achieving reliable insulation

Abstract

The present invention provides a megavolt-level high-voltage vacuum insulation stack capable of achieving reliable insulation, which is used to solve the technical problem that air bubbles are likely to accumulate near the three-phase point electric field shielding structure of the existing high-voltage insulation stack, resulting in surface flashover or breakdown on the side of the liquid insulation medium of the high-voltage insulation stack. In the present invention, an annular exhaust groove is coaxially provided at a position on the second annular semi-circular protrusion of the three-phase point electric field shielding structure close to the insulating ring and connecting the first support electrode; the exhaust groove is obliquely opened from bottom to top, and the groove width thereof is smaller than the cross-sectional radius of the second annular semi-circular protrusion; a plurality of exhaust holes communicating with the exhaust groove are circumferentially provided at a position on the upper end surface of the first support electrode corresponding to the outside of the first annular semi-circular protrusion; the arrangement of the exhaust groove and the exhaust holes can discharge as many air bubbles as possible on the basis that the arrangement of the exhaust groove does not affect the electric field shielding effect.

Description

Technical Field

[0001] The present invention relates to an insulation stack, and in particular to a megavolt-level high-voltage vacuum insulation stack that can achieve reliable insulation. Background Art

[0002] The high-voltage vacuum insulation stack is an important component of a large pulsed power device, mainly playing important roles of mechanical support and physical isolation of different types of insulating media. The high-voltage vacuum insulation stack is usually one of the weakest insulation parts of the whole pulsed power device. The medium on its inner side is vacuum, and the medium on its outer side is a liquid insulating medium (usually deionized water). Based on the need of electric field shielding, a triple-point electric field shielding structure is usually designed on the liquid insulating medium side of the insulation stack. However, due to the special electric field distribution near the high-voltage insulation stack, air bubbles are particularly likely to accumulate near the triple-point electric field shielding structure of the insulation stack. Experiments have found that the air bubbles accumulated in these positions are an important cause of surface flashover or breakdown on the liquid insulating medium side of the insulation stack, seriously affecting the insulation reliability of the insulation stack. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problem that air bubbles are likely to accumulate near the triple-point electric field shielding structure of the existing high-voltage insulation stack, resulting in surface flashover or breakdown on the liquid insulating medium side of the high-voltage insulation stack, and to provide a megavolt-level high-voltage vacuum insulation stack that can achieve reliable insulation.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] A megavolt-level high-voltage vacuum insulation stack capable of achieving reliable insulation, comprising M layers of stacked high-voltage vacuum insulation stacks. The inner side of the M-layer high-voltage vacuum insulation stack is a vacuum medium, and the outer side is a liquid insulation medium; each layer of the high-voltage vacuum insulation stack includes a plurality of insulating rings stacked coaxially, and a metal grading ring is coaxially arranged between every two insulating rings, and the inner and outer sides of the metal grading ring respectively extend out of the inner and outer side walls of the insulating ring; a ring-shaped first support electrode is coaxially and hermetically arranged between adjacent two layers of high-voltage vacuum insulation stacks and at the upper end of the M-layer high-voltage vacuum insulation stack respectively, and a ring-shaped second support electrode is coaxially and hermetically arranged at the lower end of the first layer of high-voltage vacuum insulation stack. The inner side walls of the first support electrode and the second support electrode both extend out of the inner side wall of the insulating ring and are immersed in the vacuum medium, and their outer side walls both extend out of the outer side wall of the insulating ring and are immersed in the liquid insulation medium; a ring-shaped triple-point electric field shielding structure is coaxially arranged at the position where the first support electrode is located in the liquid insulation medium and in contact with the corresponding insulating ring; the triple-point electric field shielding structure includes a first ring-shaped semi-circular protrusion arranged on the upper end face of the first support electrode and second ring-shaped semi-circular protrusions symmetrically arranged on the lower end face of the first support electrode; M is an even number greater than or equal to 2; the special feature is that a ring-shaped exhaust groove is coaxially opened at the position on the second ring-shaped semi-circular protrusion close to the insulating ring and connecting the first support electrode.

[0006] The exhaust groove is obliquely opened from bottom to top, and its groove width is smaller than the cross-sectional radius of the second ring-shaped semi-circular protrusion, and the cross-sectional radius of the second ring-shaped semi-circular protrusion is the longitudinal cross-sectional radius; the groove width of the exhaust groove is smaller than the cross-sectional radius of the second ring-shaped semi-circular protrusion, which is used to ensure that the setting of the exhaust groove does not affect the electric field shielding effect of the triple-point electric field shielding structure.

[0007] A plurality of exhaust holes communicating with the exhaust groove are circumferentially opened at the position on the upper end face of the first support electrode corresponding to the outside of the first ring-shaped semi-circular protrusion.

[0008] Furthermore, the aperture diameter of the exhaust hole is equal to the groove width of the exhaust groove, which is convenient for the integral processing of the exhaust groove and the exhaust hole on the basis of ensuring as many bubbles as possible are discharged.

[0009] Furthermore, a hydrophilic layer is arranged at the position where the surface of the first support electrode contacts the liquid insulation medium, which is used to further enhance the exhaust effect of the exhaust groove and the exhaust hole.

[0010] The present invention also provides another megavolt-level high-voltage vacuum insulation stack that can achieve reliable insulation, including M layers of stacked high-voltage vacuum insulation stacks. The inner side of the M-layer high-voltage vacuum insulation stack is a vacuum medium, and the outer side is a liquid insulation medium; each layer of the high-voltage vacuum insulation stack includes a hollow cylindrical integrated insulation cylinder and a plurality of metal grading rings; the plurality of metal grading rings are coaxially arranged on the outer wall of the integrated insulation cylinder in sequence along the axial direction, and the outer side wall of the metal grading ring is suspended outside the integrated insulation cylinder, and its inner side wall is embedded in the side wall of the integrated insulation cylinder; a ring-shaped first support electrode is coaxially and hermetically arranged between adjacent two layers of high-voltage vacuum insulation stacks and at the upper end of the Mth layer of high-voltage vacuum insulation stack respectively, and a ring-shaped second support electrode is coaxially and hermetically arranged at the lower end of the first layer of high-voltage vacuum insulation stack. The inner side walls of the first support electrode and the second support electrode are both immersed in the vacuum medium, and their outer side walls are both immersed in the liquid insulation medium; a ring-shaped triple-point electric field shielding structure is coaxially arranged at the position where the first support electrode is in contact with the integrated insulation cylinder in the liquid insulation medium; the triple-point electric field shielding structure includes a first annular semi-circular protrusion arranged on the upper end surface of the first support electrode and a second annular semi-circular protrusion symmetrically arranged on the lower end surface of the first support electrode; M is an even number greater than or equal to 2; the special feature is that a ring-shaped exhaust groove is coaxially opened at the position on the second annular semi-circular protrusion close to the insulation ring and connecting the first support electrode;

[0011] The exhaust groove is obliquely opened from bottom to top, and its groove width is smaller than the cross-sectional radius of the second annular semi-circular protrusion. The cross-sectional radius of the second annular semi-circular protrusion is the longitudinal cross-sectional radius; the groove width of the exhaust groove is smaller than the cross-sectional radius of the second annular semi-circular protrusion, so that the setting of the exhaust groove does not affect the electric field shielding effect of the triple-point electric field shielding structure;

[0012] A plurality of exhaust holes communicating with the exhaust groove are circumferentially opened at the position on the upper end surface of the first support electrode corresponding to the outside of the first annular semi-circular protrusion.

[0013] Furthermore, the aperture of the exhaust hole is equal to the groove width of the exhaust groove, which is convenient for the integrated processing of the exhaust groove and the exhaust hole on the basis of ensuring the discharge of as many bubbles as possible.

[0014] Furthermore, a hydrophilic layer is arranged at the position where the surface of the first support electrode is in contact with the liquid insulation medium, which is used to further enhance the exhaust effect of the exhaust groove and the exhaust hole.

[0015] The beneficial effects of the present invention compared with the prior art are as follows:

[0016] 1. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation provided by the present invention, compared with the high-voltage insulation stacks commonly used in current pulse power devices, has exhaust grooves and corresponding exhaust holes opened in the triple-point electric field shielding structure, enabling the gas and bubbles in the gap between the insulation stack and the triple-point electric field shielding structure to be conveniently discharged, reducing the number of bubbles staying and accumulating near the triple-point electric field shielding structure of the insulation stack, and thus reducing the factors causing surface flashover along the water side of the insulation stack, greatly improving the insulation reliability of the water side along the surface of the insulation stack with deionized water, and having great application prospects in pulse power devices.

[0017] 2. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation provided by the present invention, by reasonably setting the width of the exhaust groove and the aperture of the exhaust hole, can ensure the electric field shielding effect of the triple-point electric field shielding structure when discharging the gas and bubbles in the water in the gap between the insulation stack and the triple-point electric field shielding structure.

[0018] 3. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation provided by the present invention, a hydrophilic layer is provided at the position where the surface of the first support electrode contacts the liquid insulating medium, which can further enhance the exhaust effect of the exhaust groove and the exhaust hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a partial longitudinal cross-sectional structure schematic diagram of the first embodiment of a MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation provided by the present invention;

[0020] Figure 2 is Figure 1 a partial enlarged view of B in

[0021] Figure 3 It is a longitudinal sectional view of the exhaust groove on the first support electrode of the present invention;

[0022] Figure 4 It is a longitudinal sectional view of the exhaust groove and the exhaust hole on the first support electrode of the present invention;

[0023] Figure 5 It is an electric field distribution diagram along the surface of the deionized water side of the existing high-voltage vacuum insulation stack without an exhaust structure and the high-voltage vacuum insulation stack of the first embodiment of the present invention, where (a) is the electric field distribution diagram along the surface of the deionized water side of the existing high-voltage vacuum insulation stack without an exhaust structure, and (b) is the electric field distribution diagram along the surface of the deionized water side of the high-voltage vacuum insulation stack of the first embodiment of the present invention;

[0024] Figure 6 It is a curve diagram of the electric field strength distribution along the surface of the deionized water side of the existing high-voltage vacuum insulation stack without an exhaust structure and the high-voltage vacuum insulation stack of the first embodiment of the present invention;

[0025] Figure 7This is a schematic diagram comparing the buoyancy and viscous force curves of different - diameter bubbles in exhaust holes with different apertures in the first embodiment of the present invention.

[0026] The specific reference numerals are as follows:

[0027] 1 - insulating ring; 2 - metal grading ring; 3 - first support electrode; 4 - second support electrode;

[0028] 5 - triple - point electric - field shielding structure, 51 - first annular semi - circular protrusion, 52 - second annular semi - circular protrusion;

[0029] 6 - exhaust groove; 7 - exhaust hole; 8 - insulating pull rod. Detailed implementation manners

[0030] To make the advantages and features of the present invention clearer, the following further describes the present invention in detail with reference to the drawings and specific embodiments.

[0031] As Figure 1 shown, a megavolt - level high - voltage vacuum insulation stack capable of achieving reliable insulation. In this embodiment, it includes 2 layers of stacked high - voltage insulation stacks. The inner side of the high - voltage insulation stack is a vacuum medium, and its outer side is a liquid insulation medium. In this embodiment, the liquid insulation medium is deionized water. In this embodiment, each layer of the high - voltage insulation stack includes 5 coaxially stacked insulating rings 1, and a metal grading ring 2 is coaxially arranged between every two insulating rings 1. A total of 4 metal grading rings 2 are arranged in this embodiment; the inner and outer sides of the metal grading ring 2 respectively extend out of the inner and outer side walls of the insulating ring 1, so that the part of the metal grading ring 2 extending out of the inner side wall of the insulating ring 1 is immersed in the vacuum medium, and the part extending out of the outer side wall of the insulating ring 1 is immersed in the deionized water. Annular first support electrodes 3 are coaxially and hermetically arranged between adjacent two layers of high - voltage insulation stacks and at the upper end of the second - layer high - voltage insulation stack respectively, and an annular second support electrode 4 is coaxially and hermetically arranged at the lower end of the first - layer high - voltage insulation stack. Among them, the inner side walls of the first support electrode 3 and the second support electrode 4 both extend out of the inner side wall of the insulating ring 1 and are immersed in the vacuum medium, and the outer side walls of the first support electrode 3 and the second support electrode 4 both extend out of the outer side wall of the insulating ring 1 and are immersed in the deionized water. A plurality of insulating pull rods 8 are circumferentially and evenly distributed on the outer sides of the first support electrode 3 and the second support electrode 4 to ensure the stability of the first support electrode 3 and the second support electrode 4. Based on the need for electric - field shielding, a ring - shaped triple - point electric - field shielding structure 5 is coaxially arranged at the position where the first support electrode 3 is in contact with the corresponding insulating ring 1 in the liquid insulation medium. The triple - point electric - field shielding structure 5 includes a first annular semi - circular protrusion 51 arranged on the upper end face of the first support electrode 3 and a second annular semi - circular protrusion 52 symmetrically arranged on the lower end face of the first support electrode 3. However, since there are many bubbles accumulated near the triple - point electric - field shielding structure 5 of the insulation stack, it seriously affects the insulation reliability of the insulation stack.

[0032] To reduce these bubbles, as Figures 2 - 4 shown, the present invention coaxially provides an annular exhaust groove 6 at a position on the second annular semi-cylindrical protrusion 52 close to one side of the insulating ring 1 and connected to the first support electrode 3; the exhaust groove 6 is obliquely provided from bottom to top. In order to prevent the exhaust groove 6 from affecting the electric field shielding effect of the triple-point electric field shielding structure 5, the groove width of the exhaust groove 6 should be smaller than the longitudinal cross-sectional radius of the triple-point electric field shielding structure 5. At the same time, a plurality of exhaust holes 7 communicating with the exhaust groove 6 are circumferentially provided at a position on the upper end face of the first support electrode 3 corresponding to the outside of the first annular semi-cylindrical protrusion 51; among them, the aperture diameter of the exhaust hole 7 is usually equal to the groove width of the exhaust groove 6. If the space at the corresponding position on the first support electrode 3 permits, the aperture diameter of the exhaust hole 7 can also be set larger than the groove width of the exhaust groove 6. Preferably, in order to allow as many bubbles as possible to be discharged, when designing the exhaust groove 6 and the exhaust holes 7, it is necessary to perform a simulation experiment on the basis of determining that the groove width of the exhaust groove 6 is smaller than the longitudinal cross-sectional radius of the triple-point electric field shielding structure 5, so as to test the buoyancy and viscous forces received by bubbles of different diameters in the exhaust holes 7 with different aperture diameters. On the premise of not affecting the shielding effect of the triple-point electric field shielding structure 5, the final groove width of the exhaust groove 6 and the aperture diameter of the exhaust hole 7 are determined according to the test results.

[0033] Through the exhaust groove 6 and the plurality of exhaust holes 7 communicating therewith, the bubbles accumulated near the triple-point electric field shielding structure 5 will be accumulated in the exhaust groove 6. When the device is filled with deionized water, it is convenient for the gas and bubbles to be discharged, thereby reducing the bubbles accumulated near the triple-point electric field shielding structure 5 of the insulation stack and the gas in the deionized water, and effectively improving the insulation reliability inside the insulation stack. Before the equipment is used, a hydrophilic coating is applied or grown on the position where the surface of the first support electrode 3 contacts the liquid insulating medium to form a hydrophilic layer, which can further enhance the exhaust effect of the exhaust groove 6 and the exhaust holes 7.

[0034] A megavolt-level high-voltage vacuum insulation stack capable of achieving reliable insulation provided by the present invention, compared with the high-voltage insulation stacks commonly used in current pulsed power devices, provides an exhaust groove 6 and corresponding exhaust holes 7 on the triple-point electric field shielding structure 5. On the premise of not affecting the electric field shielding effect, the gas and bubbles in the gap between the insulation stack and the triple-point electric field shielding structure 5 are conveniently discharged, reducing the number of bubbles staying and accumulating near the triple-point electric field shielding structure 5 of the insulation stack, and further reducing the factors causing surface flashover along the water side of the insulation stack, greatly improving the insulation reliability of the surface along the deionized water side of the insulation stack, and having great application prospects in pulsed power devices.

[0035] To prove the effect of the present invention, the following is further described through specific test experiments.

[0036] Select the high-voltage vacuum insulation stack of the first embodiment of the present invention with a withstand voltage of 1.2 MV and the high-voltage vacuum insulation stack of the existing non-exhaust structure with a withstand voltage of 1.2 MV respectively. As Figure 5 shown, it is the deionized water side surface electric field distribution diagram of the high-voltage vacuum insulation stack of the existing non-exhaust structure and the high-voltage vacuum insulation stack of the first embodiment of the present invention; among them, Figure 5 (a) in is the deionized water side surface electric field distribution diagram of the high-voltage vacuum insulation stack of the existing non-exhaust structure, Figure 5 (b) in is the deionized water side electric field distribution diagram of the high-voltage vacuum insulation stack of the first embodiment of the present invention. It can be seen that when the voltage is 1.2 MV, the electric field distributions of the high-voltage vacuum insulation stacks of the two structures are very different, and the exhaust groove 6 and the exhaust hole 7 in the present invention do not affect the electric field shielding effect of the triple-point electric field shielding structure 5. This effect can also be clearly obtained from Figure 6 as shown in Figure 6 shown, it is the electric field strength distribution curve diagram of the deionized water side surface of the high-voltage vacuum insulation stack of the existing non-exhaust structure and the high-voltage vacuum insulation stack of the first embodiment of the present invention; among them, the dotted line represents the electric field strength distribution curve diagram of the deionized water side surface of the high-voltage vacuum insulation stack of the existing non-exhaust structure, and the solid line represents the electric field strength distribution curve diagram of the deionized water side surface of the high-voltage vacuum insulation stack of the first embodiment of the present invention; it can be seen that the electric field strength distributions of the high-voltage vacuum insulation stacks of the two structures along the deionized water side surface are almost the same. Although the electric field strength near the triple-point electric field shielding structure 5 of the present invention is about 40 kV / cm, the electric field near the triple-point electric field shielding structure 5 is still effectively shielded and is not affected by the exhaust groove 6 and the exhaust hole 7.

[0037] As Figure 7 shown, it is the comparison diagram of the buoyancy and viscous force curves of bubbles with different diameters in the exhaust hole 7 with different apertures when the radius of the triple-point electric field shielding structure 5 in the first embodiment of the present invention is 7 mm; it can be seen that the buoyancy and viscous forces of bubbles with different diameters in the exhaust hole 7 with different apertures are also completely different. The aperture of the exhaust hole 7 is 4 mm and 6 mm. In theory, bubbles with a diameter greater than 4 mm can be discharged, but through simulation experiments, when the aperture of the exhaust hole 7 is 6 mm, it will affect the shielding effect of the triple-point electric field shielding structure 5; therefore, when the radius of the triple-point electric field shielding structure 5 is 7 mm, the aperture of the exhaust hole 7 is 4 mm, which can discharge gas and bubbles as much as possible without affecting the shielding effect of the triple-point electric field shielding structure 5.

[0038] Embodiment 2

[0039] The difference between the second embodiment and the first embodiment is that the two layers of high-voltage insulation stacks in the second embodiment are both integrated insulation stacks. Similarly, the inner side of the high-voltage insulation stack is a vacuum medium, and the outer side is a liquid insulation medium. In this embodiment, the liquid insulation medium is deionized water. Specifically, each insulation stack in this embodiment includes a hollow cylindrical integrated insulation cylinder and four metal grading rings 2; the four metal grading rings 2 are coaxially arranged on the outer wall of the integrated insulation cylinder in sequence along the axis, and the outer side walls of the metal grading rings 2 are suspended outside the integrated insulation cylinder, so that the metal grading rings 2 suspended outside the integrated insulation cylinder are immersed in deionized water, and their inner side walls are embedded in the side walls of the integrated insulation cylinder and do not contact the vacuum inside the integrated insulation cylinder. A ring-shaped first support electrode 3 is coaxially and hermetically arranged between adjacent two layers of high-voltage insulation stacks and at the upper end of the second layer of high-voltage insulation stack respectively, and a ring-shaped second support electrode 4 is coaxially and hermetically arranged at the lower end of the first layer of high-voltage insulation stack. Among them, the inner side walls of the first support electrode 3 and the second support electrode 4 extend out of the inner side wall of the insulation ring 1 and are immersed in the vacuum medium, and the outer side walls of the first support electrode 3 and the second support electrode 4 extend out of the outer side wall of the insulation ring 1 and are immersed in deionized water. Based on the need for electric field shielding, a ring-shaped triple-point electric field shielding structure 5 is coaxially arranged at the position where the first support electrode 3 is in contact with the integrated insulation cylinder in deionized water. The triple-point electric field shielding structure 5 includes a first ring-shaped semi-circular protrusion 51 integrally arranged with the upper end face of the first support electrode 3 and a second ring-shaped semi-circular protrusion 52 integrally arranged with the lower end face of the first support electrode 3. The arrangement positions and functions of the exhaust grooves 6 and exhaust holes 7 in the second embodiment are the same as those in the first embodiment. The above test methods are also applicable to the second embodiment.

[0040] As described above, it is only used to illustrate the technical solution of the present invention and is not intended to limit it. For those of ordinary professional skills in the art, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features can be equivalently replaced. These modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation, comprising M layers of stacked high-voltage vacuum insulation stacks. The inner side of the M-layer high-voltage vacuum insulation stack is a vacuum medium, and the outer side is a liquid insulation medium; each layer of the high-voltage vacuum insulation stack includes a plurality of insulating rings (1) stacked coaxially. A metal grading ring (2) is coaxially arranged between every two insulating rings (1), and the inner and outer sides of the metal grading ring (2) respectively extend out of the inner and outer side walls of the insulating ring (1); between adjacent two layers of high-voltage vacuum insulation stacks and at the upper end of the Mth layer of high-voltage vacuum insulation stack, annular first support electrodes (3) are coaxially and hermetically arranged respectively. At the lower end of the first layer of high-voltage vacuum insulation stack, an annular second support electrode (4) is coaxially and hermetically arranged. The inner side walls of the first support electrode (3) and the second support electrode (4) both extend out of the inner side wall of the insulating ring (1) and are immersed in the vacuum medium, and their outer side walls both extend out of the outer side wall of the insulating ring (1) and are immersed in the liquid insulation medium; at the position where the first support electrode (3) is located in the liquid insulation medium and in contact with the corresponding insulating ring (1), an annular triple-point electric field shielding structure (5) is coaxially arranged; the triple-point electric field shielding structure (5) includes a first annular semi-circular protrusion (51) arranged on the upper end face of the first support electrode (3), and a second annular semi-circular protrusion (52) symmetrically arranged on the lower end face of the first support electrode (3); M is an even number greater than or equal to 2; characterized in that: An annular exhaust groove (6) is coaxially opened at a position on the second annular semi-circular protrusion (52) close to the insulating ring (1) and connecting the first support electrode (3); The exhaust groove (6) is obliquely opened from bottom to top, and its groove width is smaller than the cross-sectional radius of the second annular semi-circular protrusion (52); A plurality of exhaust holes (7) communicating with the exhaust groove (6) are circumferentially opened at a position on the upper end face of the first support electrode (3) corresponding to the outside of the first annular semi-circular protrusion (51).

2. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation according to claim 1, characterized in that: The aperture of the exhaust hole (7) is equal to the groove width of the exhaust groove (6).

3. A MV-class high-voltage vacuum insulation stack capable of achieving reliable insulation according to claim 1 or 2, characterized in that: A hydrophilic layer is arranged at the position where the surface of the first support electrode (3) contacts the liquid insulation medium.

4. A megavolt - level high - voltage vacuum insulation stack capable of achieving reliable insulation, comprising M layers of stacked high - voltage vacuum insulation stacks. The inner side of the M - layer high - voltage vacuum insulation stack is a vacuum medium, and the outer side is a liquid insulation medium; each layer of the high - voltage vacuum insulation stack includes a hollow cylindrical integrated insulation cylinder and a plurality of metal grading rings (2); the plurality of metal grading rings (2) are coaxially arranged along the axial direction on the outer wall of the integrated insulation cylinder in sequence, and the outer side wall of the metal grading ring (2) floats outside the integrated insulation cylinder, and its inner side wall is embedded in the side wall of the integrated insulation cylinder; a ring - shaped first support electrode (3) is coaxially and hermetically arranged between adjacent two layers of high - voltage vacuum insulation stacks and at the upper end of the M - layer high - voltage vacuum insulation stack respectively, and a ring - shaped second support electrode (4) is coaxially and hermetically arranged at the lower end of the first - layer high - voltage vacuum insulation stack. The inner side walls of the first support electrode (3) and the second support electrode (4) are both immersed in the vacuum medium, and their outer side walls are both immersed in the liquid insulation medium; a ring - shaped triple - point electric - field shielding structure (5) is coaxially arranged at the position where the first support electrode (3) is in contact with the integrated insulation cylinder in the liquid insulation medium; the triple - point electric - field shielding structure (5) includes a first annular semi - circular protrusion (51) arranged on the upper end face of the first support electrode (3) and a second annular semi - circular protrusion (52) symmetrically arranged on the lower end face of the first support electrode (3); M is an even number greater than or equal to 2; it is characterized in that: An annular exhaust groove (6) is coaxially opened at the position on the second annular semi - circular protrusion (52) close to the insulating ring (1) and connecting the first support electrode (3). The exhaust groove (6) is obliquely opened from bottom to top, and its groove width is smaller than the cross - sectional radius of the second annular semi - circular protrusion (52). A plurality of exhaust holes (7) communicating with the exhaust groove (6) are circumferentially opened at the position on the upper end face of the first support electrode (3) corresponding to the outside of the first annular semi - circular protrusion (51).

5. A megavolt - level high - voltage vacuum insulation stack capable of achieving reliable insulation according to claim 4, characterized in that: The aperture of the exhaust hole (7) is equal to the groove width of the exhaust groove (6).

6. A megavolt - level high - voltage vacuum insulation stack capable of achieving reliable insulation according to claim 4 or 5, characterized in that: A hydrophilic layer is arranged at the position where the surface of the first support electrode (3) contacts the liquid insulation medium.

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