JP2007097376A - Insulated plug structure of bushing for electric power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress partial discharge generated in an air (gap) portion of the triple junction of an insulated plug. <P>SOLUTION: The open terminal port 24 of a bushing comprises a tapered insulation part 25 provided to a bushing body 21 and a large diameter insertion part 26 and a small diameter insertion part 27 each provided to the tapered insertion part 25. The insulated plug 4 comprises an insulating rubber 41, a high voltage side metal fixture 42 buried on the small diameter side of the insulating rubber 41, and a low voltage side metal fixture 43 buried on the large diameter side of the insulating rubber 41. A shield electrode 22d has a substantially cylindrical structure surrounding the tapered insertion part 25 and the end part 22f of the shield electrode 22d extends toward the lower voltage side metal fixture rather than the position of the top 42c of the protruding part 42a which constitutes the high voltage side metal fixture 42, allowing the vicinity of the outer peripheral part of the insulating rubber 41 which contacts the high voltage side metal fixture 42 to be electrically shielded with the shield electrode 22d in the state having the insulated plug 4 mounted on the open terminal port 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an insulating plug structure for a power bushing, and more particularly, to an insulating plug structure for a power bushing that is attached to a vacant electrical outlet of a bushing such as a direct connection type terminal connection portion or a branch connection portion of a power cable.

  Conventionally, an insulating plug structure of this type of power bushing is shown in FIG. 7 (for example, Patent Document 1).

  In the figure, a T-type bushing 200 is hermetically attached to a side plate of a sealed-type device case 100 that houses electrical devices such as a switch and a transformer, and is provided in a vertical portion of the bushing 200. A power cable 300 is connected to the first charging port 210, and a second charging port (hereinafter referred to as “vacant charging port”) 220 provided at the right end of the horizontal portion is connected to the empty charging port. An insulating plug 400 is attached to electrically insulate the port 220.

  As shown in FIG. 8, the insulating plug 400 is provided with a cone-shaped insulating rubber 410 to be attached to the empty charging port 220 of the bushing 200 and a small diameter portion (high pressure side) of the insulating rubber 410. The high voltage side metal fitting 420 electrically connected to the high voltage electrode 230 embedded therein, and the low voltage side provided on the large diameter portion side (low pressure side) of the insulating rubber 410 and arranged to face the high voltage side metal fitting 420. And a metal fitting 430. The high-pressure metal fitting 420 has a convex portion 420 a that bulges toward the low-pressure side at the boundary surface with the insulating rubber 410, and the low-voltage metal fitting 430 bulges toward the high-pressure side at the interface with the insulating rubber 410. have.

  In the insulating plug 400 having such a configuration, the spring 440 is disposed on the back surface side of the low-voltage side metal fitting 430, and the spring 440 is compressed in the axial direction by the fixed lid 450 disposed in the opening portion of the empty power application port 220. As a result, the insulating rubber 410 of the insulating plug 400 is pressed against the inner wall surface of the empty power application port 220 of the bushing 200, thereby ensuring the insulation performance at the interface between the inner wall surface of the empty power application port 220 and the insulating rubber 410. Will be.

Japanese Patent No. 3192727 (paragraphs “0011” to “0015”, see FIG. 1)

  By the way, in such an insulating plug structure of a power bushing, a triple junction where a conductor (high-voltage side metal fitting 420), air (a gap between the high-voltage side metal fitting 420 and the insulating rubber 410) and a dielectric (insulating rubber 410) are in contact. Since the point (hereinafter referred to as “triple junction”) P exists on the high voltage side of the insulating plug 400 and the triple junction P is not sufficiently shielded by the high voltage electrode 230, it is shown in FIGS. 9A and 9B. As described above, the electric field wraps around the triple junction P during the withstand voltage test, and there is a problem that partial discharge occurs in the air (gap) portion of the triple junction P. For example, in a 66/77 kV device direct connection type terminal connection, there is a possibility that partial discharge may occur at about 70 kV with respect to a withstand voltage value of 160 kV.

  The present invention has been made to solve the above-mentioned problems, and provides an insulating plug structure for a power bushing that can suppress the occurrence of partial discharge in the air (gap) portion of the triple junction of the insulating plug. It is an object.

  An insulating plug structure for a power bushing according to the first aspect of the present invention includes a bushing made of a hard insulating resin and having a tapered insertion portion connected to a high voltage electrode, and an insulating plug mounted on the tapered insertion portion. The bushing is provided with a shielding electrode from the high voltage electrode to the tapered insertion portion, and the insulating plug has a high voltage side fitting that is at the same potential as the high voltage electrode, a low voltage side fitting that faces the high voltage side fitting, and a high voltage An insulating rubber located between the side metal fitting and the low-voltage metal fitting is provided, and the vicinity of the outer peripheral end portion of the insulating rubber contacting the high-voltage side metal fitting is electrically shielded by the shielding electrode.

  According to a second aspect of the present invention, in the insulating plug structure for a power bushing according to the first aspect, the high-voltage side metal fitting has a convex portion swelled toward the insulating rubber side, and the shielding electrode surrounds the tapered insertion portion. It has a substantially cylindrical structure that surrounds, and its end portion extends to a position on the low-pressure side of the convex portion of the high-pressure side metal fitting.

  According to a third aspect of the present invention, in the insulating bushing structure for a power bushing according to the first aspect or the second aspect, the shielding electrode has a substantially cylindrical structure surrounding the tapered insertion portion. The end portion extends to the periphery of the central portion in the axial direction of the insulating plug.

  According to the insulating bushing structure of the power bushing of the first to third aspects of the present invention, the insulating plug is electrically shielded by the shielding electrode in the vicinity of the outer peripheral end portion in contact with the high-voltage side metal fitting of the insulating rubber. The triple junction that exists on the high-voltage side moves away from the electric field that wraps around the inside of the shield electrode. As a result, the occurrence of partial discharge in the air (gap) part of the triple junction can be suppressed, improving the reliability of the product. At the same time, it is possible to prevent the defect rate from decreasing.

Hereinafter, preferred embodiments to which the insulating plug structure of the power bushing of the present invention is applied will be described with reference to the drawings.
[Example 1]
FIG. 1 is a longitudinal sectional view showing an embodiment in which an insulating plug structure of a power bushing according to the present invention is applied to an apparatus direct connection type cable terminal connection portion, and FIG. 2 is a longitudinal section of an insulating plug attached to a vacant charging port of the bushing. FIG. In FIG. 2, the same reference numerals are given to portions common to FIG. 1.

  In FIG. 1, electrical devices (not shown) such as switches and transformers are accommodated in a sealed device case 1, and a T-type bushing 2 is attached to the side plate of the device case 1 in an airtight manner. Yes.

  The bushing 2 includes a T-shaped bushing body 21 made of a hard insulating resin such as an epoxy resin, and a high voltage electrode 22 having a shape substantially similar to the bushing body 21 is concentrically formed with the bushing body 21. Buried. In addition, the vertical portion of the bushing body 21 is provided with a first electrical outlet 23 for connecting, for example, a 66/77 kV CV cable (cross-linked polyethylene insulated vinyl sheath cable) 3. 2 (for example, the right end in the figure) is a second charging port (hereinafter referred to as “empty charging port”) 24 for mounting an insulating plug 4 as shown in FIG. Is provided.

  The high-voltage electrode 22 includes a first conductor insertion portion 22a provided in a vertical portion of the bushing main body 21 so as to be concentric with the first power application port 23 and communicated with the first power application port 23, and the bushing main body. A second conductor insertion hole 22b provided concentrically with the empty power application port 24 at the right end of the horizontal portion 21 and in communication with the empty power application port 24; and a second conductor insertion hole 22b provided at the left end of the horizontal portion. The conductor lead-out rod 22c concentrically connected to the conductor insertion hole 22b, and the second conductor insertion hole 22b and concentric with the second conductor insertion hole 22b and to a tapered insertion part 25 described later. And a substantially cylindrical shielding electrode 22d.

  As shown in FIG. 2, the empty charging port 24 has a tapered inner surface that is conically reduced in diameter from the right end to the second conductor insertion hole 22b on the right end of the horizontal portion of the bushing body 21. And a circular insertion portion (hereinafter referred to as “large diameter insertion portion”) provided to communicate with the taper insertion portion 25 on the large diameter portion side (low pressure side) of the taper insertion portion 25. ) 26 and a circular insertion portion (hereinafter referred to as “small-diameter insertion portion”) 27 provided on the small-diameter portion side (high-pressure side) of the tapered insertion portion 25 so as to communicate with the tapered insertion portion 25. Yes. Here, the tapered insertion portion 25, the large-diameter insertion portion 26, and the small-diameter insertion portion 27 are provided concentrically with the second conductor insertion portion 22b, and the diameter of the small-diameter insertion portion 27 is the second diameter. The diameter of the conductor insertion portion 22b is larger than the diameter on the large diameter portion side.

  As shown in FIG. 2, the insulating plug 4 includes an insulating rubber 41 made of ethylene propylene rubber (EP rubber) having a tapered outer surface corresponding to the tapered inner surface of the tapered insertion portion 25, and a small diameter portion side of the insulating rubber 41. A hemispherical high voltage side metal fitting 42 embedded in the high voltage side and having the same potential as the high voltage electrode 22, and a high voltage across the central portion of the insulating rubber 41 embedded in the large diameter portion side (low pressure side) of the insulating rubber 41. A side metal fitting 42 and a hemispherical low-pressure metal fitting 43 arranged opposite to each other are provided.

  The high-voltage side metal fitting 42 is provided with a convex portion 42 a swelled toward the insulating rubber 41 and an outer wall surface exposed to the small diameter portion side of the insulating rubber 41, and the outer wall surface contacts the step wall 22 e of the high-voltage electrode 22. The low-pressure side metal fitting 43 has a convex portion 43a swelled on the insulating rubber 41 side, and an outer wall surface exposed on the large-diameter portion side of the insulating rubber 41. And a large-diameter disk portion 43b that is in contact with a front surface side of a fixed plate 45 described later. Here, the outer diameter of the small-diameter disk portion 42 b is substantially the same as the diameter of the small-diameter insertion portion 27, and the outer diameter of the large-diameter disk portion 43 b is slightly smaller than the diameter of the large-diameter insertion portion 26. Further, a plurality of spring housing holes 43 c are provided in the vicinity of the outer peripheral edge on the back side of the low-pressure side metal fitting 43 so as to be equally distributed along the circumferential direction.

  The insulating plug 4 having such a configuration is attached to the empty power distribution port 24 of the bushing 2 as follows.

  First, the coil-shaped springs 44 are respectively mounted in the respective spring housing holes 43c, and in this state, the high-voltage side metal fitting 42 of the insulating plug 4 is mounted toward the empty power application port 24 side. Then, a disk-shaped fixing plate 45 is disposed on the back side of the low-pressure side metal fitting 43, and the bushing main body is utilized using a fixing bolt 46 in which the fixing plate 45 is equally distributed in the vicinity of the outer peripheral edge along the circumferential direction. 21 is fastened to the right end of the horizontal portion.

  As a result, a spring force toward the second conductor insertion portion 22b is urged against the spring 44, and the taper outer surface of the insulating rubber 41 is pressed against the taper inner surface of the taper insertion portion 25, and consequently the taper of the taper insertion portion 25. The insulation performance of the interface between the inner surface and the tapered outer surface of the insulating rubber 41 is ensured. In the figure, reference numeral 28 denotes an embedded screw embedded in the vicinity of the outer peripheral edge of the right end portion of the horizontal portion of the bushing body 21 so as to be equally distributed along the circumferential direction, and 29 denotes an O-ring.

According to the insulating bushing structure of the power bushing having such a configuration, the shielding electrode 22d has a substantially cylindrical structure surrounding the tapered insertion portion 25 as described above, and the end of the shielding electrode 22d The portion 22f extends toward the low pressure side (the right end side of the horizontal portion of the bushing body 21) from the position of the top portion 42c of the convex portion 42a constituting the high pressure side metal fitting 42. In a state of being attached to the charging port 24, the insulating rubber 41 is in the vicinity of the outer peripheral end in contact with the high-voltage side metal fitting 42, that is, the high-voltage side metal fitting 42, the gap (air) between the high-voltage metal fitting 42 and the insulation rubber 41, The triple junction P as a triple junction where the two are in contact with each other is electrically shielded by the shielding electrode 22d. Therefore, according to the insulating plug structure of the power bushing of the present invention, the triple junction P of the insulating plug 4 is positioned inside the shielding electrode 22d and closer to the high-voltage electrode 22 than the end 22f, that is, triple. By causing the junction P to be away from the electric field that wraps around the inner side of the shield electrode 22d when performing a withstand voltage test, the occurrence of partial discharge in the gap (air) portion of the triple junction P can be suppressed. The reliability of the product can be improved, and the failure rate can be prevented from decreasing.
[Example 2]
FIG. 3 is a longitudinal sectional view showing an example in which the insulating bushing structure of the power bushing according to the present invention is applied to a bushing of a sealed power device or the like.

  In the figure, a bushing 5 according to the present invention includes a bushing body 6 made of a hard insulating resin such as an epoxy resin, and a high voltage electrode 7 embedded concentrically with the bushing body 6 at the top (high voltage side) center of the bushing body 6. And a substantially cylindrical shielding electrode 8 concentrically embedded with the bushing body 6 at the distal end (high voltage side) of the bushing body 6 and connected to the high voltage electrode 7.

  The bushing main body 6 includes a tapered insertion portion 61 having a tapered inner surface that has a tapered inner diameter that decreases in a conical shape toward the high-voltage electrode 7 side of the bushing main body 6, and a large size of the tapered insertion portion 61. A circular insertion portion (hereinafter referred to as “large diameter insertion portion”) 62 provided to communicate with the tapered insertion portion 61 on the radial side, and a tapered insertion portion 61 on the small diameter side of the tapered insertion portion 61. A circular insertion portion (hereinafter referred to as “small-diameter insertion portion”) 63 provided so as to communicate with the annular portion, and an annular mounting flange 64 protruding radially on the outer periphery of the lower half portion of the bushing body 6. Are connected. Here, the tapered insertion portion 61, the large diameter insertion portion 62, and the small diameter insertion portion 63 are provided concentrically with the bushing body 6, and the diameter of the small diameter insertion portion 63 is a conductor insertion hole 71a described later. The diameter is larger than the diameter.

  The high-voltage electrode 7 is connected to the cylindrical conductor insertion portion 71 having a conductor insertion hole 71a concentrically with the small-diameter insertion portion 63 and communicating with the small-diameter insertion portion 63, and to the distal end portion of the conductor insertion portion 71. The upper half part of the conductor insertion part 71 of such a structure protrudes upwards from the center part of the top part of the bushing main body 6. As shown in FIG.

  The shield electrode 8 is connected to the outer peripheral edge of the rear end portion of the conductor insertion portion 71 constituting the high-voltage electrode 7 and the outer peripheral edge of the horizontal portion 81 concentrically with the bushing body 6. A bell-shaped shield electrode main body 82 having a conical diameter increasing from the top of the bushing main body 6 toward the rear end side is provided. Here, the inner surface of the horizontal portion 81 is exposed to the small diameter insertion portion 63 side, and the end portion 82a of the shielding electrode main body 82 is on the low pressure side (of the bushing main body 21) than the position of the top portion 911c of the convex portion 911a constituting the high voltage side metal fitting 911. It extends toward the rear end side).

The bushing 5 having such a configuration is hermetically sealed such that the tip portion (high-pressure side) of the device case 10 that houses an electrical device (not shown) in an airtight manner is positioned in the device case 10. It is attached to. The equipment case 10 is filled with an insulating gas such as SF ₆ gas.

  The insulating plug 9 includes an insulating plug main body 91 mounted in the tapered insertion portion 61 of the bushing main body 6, and a small diameter insertion portion 63 located at the distal end of the insulating plug main body 91 and in the small diameter insertion portion 63 of the bushing main body 6. And a cylindrical contact member 92 concentrically mounted on the rear end of the insulating plug body 91 and concentrically with the large diameter insert 62 in the large diameter insert 62 of the bushing body 6. A cylindrical pressing member 93 is provided.

  The insulating plug body 91 is embedded in an insulating rubber 910 made of ethylene propylene rubber (EP rubber) or the like having a tapered outer surface corresponding to the tapered inner surface of the tapered insertion portion 61, and the small diameter portion side (high pressure side) of the insulating rubber 910. The hemispherical high-pressure metal fitting 911 having the same potential as the contact member 92 and the large-diameter portion side (low-pressure side) of the insulating rubber 910 are placed opposite to each other with the high-voltage metal fitting 911 and the central portion of the insulating rubber 910 sandwiched therebetween. Hemispherical low-pressure side metal fitting 912.

  The high-voltage side metal fitting 911 is provided so that a convex portion 911 a swelled toward the insulating rubber 910 side and an outer wall surface thereof are exposed on the small diameter portion side of the insulating rubber 910, and the outer wall surface contacts the rear end portion of the contact member 92. The low-pressure side metal fitting 912 has a convex portion 912a swelled on the insulating rubber 910 side and an outer wall surface exposed on the large-diameter portion side of the insulating rubber 910. And a large-diameter disk portion 912b that is in contact with the front surface side of the closing portion 932 of the pressing member 93 described by the outer wall surface. Here, the outer diameter of the small-diameter disc portion 911 b is substantially the same as the aperture of the small-diameter insertion portion 63, and the outer diameter of the large-diameter disc portion 912 b is slightly smaller than the aperture of the large-diameter insertion portion 62. Further, a plurality of spring housing holes 913 and screw holes 914 are provided in the vicinity of the outer peripheral edge on the back side of the low-pressure side metal fitting 912 so as to be equally distributed along the circumferential direction.

  The contact member 92 is formed of a metal fitting such as an aluminum alloy, the outer diameter thereof is slightly smaller than the diameter of the small diameter insertion portion 63 of the bushing body 6, and the axial length thereof is the axial direction of the small diameter insertion portion 63. It is slightly shorter than the length. Specifically, the length of the contact member 92 in the axial direction is such that the distal end portion (high voltage side) of the contact member 92 forms the high voltage electrode 7 in a state where the insulating plug 9 is mounted in the bushing 5 at the normal position. The conductor insertion portion 71 is in electrical contact with the rear end portion (or the inner surface of the horizontal portion 81 of the shield electrode 8), and the rear end portion is in electrical contact with a small-diameter circular portion 911b of a high-voltage side metal fitting 911 described later. It is said to be long.

  The pressing member 93 includes a cylindrical portion 931 that is concentrically mounted on the large-diameter insertion portion 62, and a closing portion 932 that is provided at the distal end portion of the cylindrical portion 931 so as to close the opening. A thick portion 931a is provided in a part of 931 along the axial direction, and a plurality of bolt insertion holes 932a are provided in the vicinity of the outer peripheral edge of the closing portion 932 so as to be evenly arranged along the circumferential direction. . The pressing member 93 is formed of a metal fitting such as an aluminum alloy, and has an outer diameter slightly smaller than the diameter of the large-diameter insertion portion 62 of the bushing body 6.

  The insulating plug 9 configured as described above is detachably attached to the insertion portion (the large diameter insertion portion 62, the tapered insertion portion 61, and the small diameter insertion portion 63) of the bushing body 6 as follows.

  First, the spring 95 is disposed in the spring housing hole 913 of the low-pressure metal fitting 912 so that the lower half of the spring 95 protrudes from the spring housing hole 913, and then is disposed from the back side of the closing portion 932 constituting the pressing member 93. The provided bolt 96 is inserted into the bolt insertion hole 932a and the tip thereof is attached to the screw hole 914 of the low-pressure side metal fitting 912. As a result, the pressing member 93 is attached to the low-pressure metal fitting 912 through the shaft portion of the bolt 96 so as to advance and retract. Then, in a state where the spring force is not biased by the spring 95, the contact member 92, the insulating plug main body 91, and the pressing member 93 are inserted into the insertion portion of the bushing main body 6, and the distal end portion of the contact member 92 attaches the high-voltage electrode 7 to the spring 95. It pushes in until it contact | abuts the rear-end part (or inner surface of the horizontal part 81 of the shielding electrode 8) of the conductor insertion part 71 to comprise. Thereby, the tapered outer surface of the insulating rubber 910 of the insulating plug main body 91 abuts on the tapered inner surface of the tapered insertion portion 61.

  Next, a fixing plate (not shown) is brought into contact with and tightened to the lower surface of the rear end portion (low pressure side) of the bushing body 6. As a result, the front side of the closing portion 932 constituting the pressing member 93 is pushed to a position where it contacts the rear end surface of the low-voltage side metal fitting 912 via the shaft portion of the bolt 96, and at the same time, the spring 95 is pressed in the axial direction. An axial spring force is biased against the spring 95.

  When the spring force in the axial direction is urged against the spring 95, the pressing member 93 constituting the insulating plug 9 is pressed toward the distal end portion of the bushing main body 6, thereby insulating the insulating plug main body 91. A predetermined surface pressure is applied to the fitting portion between the tapered outer surface of the rubber 910 and the tapered inner surface of the tapered insertion portion 61. As a result, a predetermined surface pressure is applied to the fitting portion between the tapered outer surface of the insulating rubber 910 and the tapered inner surface of the tapered insertion portion 61, thereby the interface between the tapered inner surface of the tapered insertion portion 61 and the insulating rubber 910. Insulation performance is ensured.

In such an insulating plug structure for a power bushing, the shield electrode body 82 constituting the shield electrode 8 has a substantially cylindrical structure surrounding the tapered insertion portion 61 as described above, The end portion 82a of the shield electrode main body 82 extends toward the low pressure side (the rear end portion side of the bushing main body 21) from the position of the top portion 911c of the convex portion 911a constituting the high-voltage side metal fitting 911 of the insulating plug 9. Thus, in a state where the insulating plug 9 is attached to the tapered insertion portion 61, the vicinity of the outer peripheral end portion of the insulating rubber 910 that contacts the high-pressure side metal fitting 911, that is, between the high-pressure side metal fitting 911 and the high-pressure side metal fitting 911 and the insulating rubber 910 Triple junction P as a triple junction where the gap (air) and insulating rubber 910 are in contact with each other is electrically shielded by shield electrode body 82. Therefore, in the insulating plug structure of the power bushing configured as described above, the triple junction P of the insulating plug 9 is arranged inside the shielding electrode main body 82 and its end 82a, as in the first embodiment. When the triple junction P is located at a position away from the electric field that wraps around the inside of the shield electrode body 82 when performing a withstand voltage test, the gap (air ) Part discharge can be suppressed, and as a result, the reliability of the product can be improved, and the failure rate can be prevented from lowering.
[Example 3]
FIG. 4 is a longitudinal sectional view showing an example in which the insulating bushing structure of the power bushing according to the present invention is applied to another bushing such as a 66/77 kV class closed type switch. In the figure, parts common to those in FIG. 3 are denoted by the same reference numerals and detailed description thereof is omitted.

  In this embodiment, the taper length is longer than that of the tapered insertion portion 61 shown in FIG. 3 in place of the small diameter insertion portion 63 for mounting the contact member 92 shown in FIG. A tapered insertion portion (hereinafter referred to as “long taper insertion portion”) 61 ′ is provided. Specifically, a high-voltage side metal fitting 911 described later is provided at the back of the insertion portion of the bushing main body 6, that is, in the vicinity of the distal end portion of the small-diameter insertion portion 63 shown in FIG. A circular insertion portion (hereinafter referred to as a “short small-diameter insertion portion”) 63 ′ for mounting a small-diameter disk portion 911b ′ is provided, and from the rear end position T1 of the short small-diameter insertion portion 63 ′. By forming a gentle taper up to the tip end position T2 of the large-diameter insertion portion 62 shown in FIG. 3, a tapered insertion portion 61 ′ having a long taper length is formed. Further, in this embodiment, instead of the insulating plug 9 shown in FIG. 3, an insulating rubber having a tapered outer surface corresponding to the tapered inner surface of the long tapered insertion portion 61 ′ (hereinafter referred to as “long insulating rubber”). An insulating plug 9 ′ having 910 ′ is used, and a high pressure side metal fitting 911 ′ having a longer axial length than the second embodiment is provided on the small diameter side (high pressure side) of the long insulating rubber 910 ′. Is buried. Here, the high-voltage side metal fitting 911 ′ is provided such that a convex portion 911 a ′ swelled on the long insulating rubber 910 ′ side and an outer wall surface thereof are exposed on the small diameter portion side of the long insulating rubber 910 ′. And a small-diameter disk portion 911b ′ whose wall surface is in contact with the inner surface of the horizontal portion 81 constituting the shielding electrode 8. The high-voltage side metal fitting 911 ′ having such a configuration includes the small-diameter disk portion 911b ′. It is electrically connected to the high voltage electrode 7 by being attached to the short small diameter insertion portion 63 ′.

  In such a power bushing insulating plug structure, the shielding electrode body 82 constituting the shielding electrode 8 has a substantially cylindrical structure surrounding the tapered insertion portion 61 'as described above, and Since the end portion 82a of the shielding electrode main body 82 constituting the shielding electrode 8 extends to a position covering the periphery of the central portion in the axial direction of the insulating plug 9 ′, that is, the high-voltage side metal fitting 911 of the insulating rubber 910 ′. Since the vicinity of the outer peripheral end in contact with ′ is closer to the back side (tip side) of the insertion portion of the bushing body 6 than in the second embodiment, the insulating plug 9 ′ is formed into the long tapered insertion portion 61 ′. In the mounted state, as shown in FIGS. 5 and 6, the high-voltage side metal fitting 911 ′, the gap (air) between the high-voltage side metal fitting 911 ′ and the insulating rubber 910 ′, and the triple junction where the insulating rubber 910 ′ contacts Triple junction P as It will be electrically completely shielded by the shield electrode body 82. Accordingly, in the insulating plug structure of the power bushing configured as described above, as in the second embodiment, the triple junction P is far from the electric field that wraps around the inside of the shield electrode body 82 when performing the withstand voltage test. Therefore, it is possible to suppress the occurrence of partial discharge in the gap (air) portion of the triple junction P, thereby improving the reliability of the product and preventing the failure rate from being lowered. .

  Further, in the insulating plug structure of the power bushing in this embodiment, since the small diameter insertion portion 63 shown in FIG. 3 does not exist, it is not necessary to use a contact fitting, and the power bushing in the second embodiment is insulated. The insulation plug can be reduced in weight and cost compared to the plug structure.

  The present invention can be changed and modified as follows within the scope of the claims.

  First, in the above-described embodiment, the structure of the insulating plug for 66/77 kV is described, but the insulating plug structure of the power bushing whose system voltage is less than 66 kV or the insulating plug of the power bushing exceeding 77 kV Even if applied to the structure, the same effect is obtained.

  Secondly, in the above-mentioned embodiment, the device direct connection type terminal connection portion of the CV cable is described. However, the present invention is not limited to this, but a bushing having a vacant electrical outlet, for example, a T branch of the CV cable. In addition, the bushing having a vacant charging port is not limited to the one attached to the side wall of the equipment case, and may be attached to the bottom plate or the top of the equipment case.

The longitudinal cross-sectional view which shows the insulation stopper structure of the bushing for electric power in 1st Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of an insulating plug that is attached to an empty power outlet of a power bushing according to a first embodiment of the present invention. The longitudinal cross-sectional view which shows the insulating stopper structure of the bushing for electric power in the 2nd Example of this invention. The longitudinal cross-sectional view which shows the insulating stopper structure of the bushing for electric power in the 3rd Example of this invention. FIG. 5 is an equipotential distribution diagram in which the equipotential line interval at the upper portion of the insulating plug shown in FIG. 4 is 5 kV / mm. FIG. 5 is an equipotential distribution diagram in which the equipotential line interval at the upper portion of the insulating plug shown in FIG. 4 is 1 kV / mm. The longitudinal cross-sectional view which shows the insulating plug structure of the conventional bushing for electric power. The longitudinal cross-sectional view of the conventional insulation stopper. In the conventional equipotential distribution diagram of the insulation plug, the distribution diagram (a) is an equipotential distribution diagram with an equipotential line interval of 5 kV / mm at the upper portion of the insulation plug, and the distribution diagram (b) is the equipotential line at the upper portion of the insulation plug. An equipotential distribution diagram with an interval of 1 kV / mm.

Explanation of symbols

2 ... Bushing 22 ... High-voltage electrode 22d ... Shielding electrode 25 ... Tapered insertion part 4 ... Insulation plug 41 ... Insulating rubber 42 ... High-voltage side metal fitting 42a ... Convex part 43 ... Low-pressure bracket

Claims (3)

A bushing made of a hard insulating resin and having a tapered insertion portion connected to the high-voltage electrode, and an insulating plug attached to the tapered insertion portion,
The bushing is provided with a shielding electrode from the high-voltage electrode to the tapered insertion portion,
The insulating plug includes a high voltage side metal fitting that has the same potential as the high voltage electrode, a low voltage side metal fitting that faces the high voltage side metal fitting, and an insulating rubber that is positioned between the high voltage side metal fitting and the low voltage side metal fitting. And
An insulating plug structure for a power bushing, wherein the insulating rubber is electrically shielded by the shielding electrode in the vicinity of an outer peripheral end portion in contact with the high-voltage metal fitting.   The high-voltage side metal fitting has a convex portion that swells toward the insulating rubber side, the shielding electrode has a substantially cylindrical structure surrounding the tapered insertion portion, and an end portion of the high-voltage side metal fitting has a convex shape. 2. The insulating bushing structure for a power bushing according to claim 1, wherein the insulating plug structure extends to a position on the low pressure side of the portion. 2. The shield electrode has a substantially cylindrical structure surrounding the tapered insertion portion, and an end thereof extends to a periphery of an axially central portion of the insulating plug. Or the insulating plug structure of the bushing for electric power of Claim 2.

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