JP2012075266A - Polymer bushing insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer bushing insulator which suppresses generation of corona discharge, and can obtain higher operation voltage, as compared with the conventional one.SOLUTION: A polymer bushing insulator 10 comprises: an inner conductor 20; an insulator 30 which covers an outer periphery of the inner conductor 20; a polymer coated body 40 which covers the outer periphery of the insulator 30 and has a plurality of pleat portions 41 formed at the outer periphery in a longitudinal direction so as to be apart from each other; a shielding metal fitting 50 which is embedded in the insulator 30 in a concentric manner to the inner conductor 20 at a base end side of the polymer coated body 40; and an electric field relaxing layer 60 which is arranged on the interface of the insulator 30 and the polymer coated body 40, and in which the base end is connected to the shielding metal fitting 50. The electric field relaxing layer 60 has a uniform part 61, an end part 62 having an arc face formed thereon, and a taper part 63 that is formed at a position at which the uniform part 61 and the end part 62 are continuously provided, and has a taper face formed to be inclined so that the inner diameter becomes small toward the end side.

Description

  The present invention relates to a polymer cannula, and more particularly to a polymer cannula provided with an electric field relaxation layer at the interface between an insulator such as an epoxy bushing and a polymer covering such as silicone rubber.

  Recently, from the viewpoint of reducing the weight of the cannula, slimming, reducing the size of the cannula, standardizing the cannula type and simplifying the work process, a polymer covering such as silicone rubber has been applied to the surface of an insulator such as an epoxy bushing. A directly molded solid insulating structure (fully dry) polymer sleeve is used.

  However, in the polymer sleeve having such a configuration, when the electric field is high, a corona discharge is generated on the outer surface of the polymer sleeve, and when the corona discharge is generated over a long period of time, the polymer coating is not chemically treated. There is a risk of degradation (erosion) due to erosion.

  As a technique for preventing the generation of corona, there is a method of providing an electric field relaxation layer at the interface between the insulator and the polymer coating (for example, see Patent Document 1), and heat generation of the electric field relaxation layer while reducing the electric field strength on the air surface. As a technique that can be suppressed, a method is known in which a large-diameter portion is provided in the vicinity of the lower end portion of the insulator and an electric field relaxation layer is provided at the interface between the large-diameter portion and the polymer coating (see, for example, Patent Document 2). ing.

JP 2005-117806 A JP 2009-005514 A JP 2007-188735 A

  In such a conventional polymer sleeve, in order to further improve the characteristics of corona discharge or to further increase the operating voltage, as described above, the insulator and the polymer coating are used. By providing an electric field relaxation layer at the interface, the diameter of the polymer cannula can be prevented to some extent. However, when further improvement in performance is required, it is necessary to increase the outer diameter of the polymer coating, and as a result, the weight of the polymer sleeve increases. Further, when the polymer sleeve becomes thick, the projected cross-sectional area of the polymer sleeve increases, and there is a problem that a long polymer sleeve must be used in order to improve the fouling withstand voltage characteristics.

  An object of the present invention is to provide a polymer cannula that can further suppress the generation of corona discharge as compared with the prior art and can further increase the operating voltage.

  One aspect of the polymer sleeve of the present invention includes an inner conductor, a hard insulator that covers the outer periphery of the inner conductor, and an outer periphery of the insulator, and a plurality of flanges are spaced apart in the longitudinal direction on the outer periphery. The formed polymer covering, and on the base end side of the polymer covering, are disposed at the interface between the insulating body and the polymer covering, and a shielding fitting embedded in the insulator concentrically with the inner conductor. An electric field relaxation layer having a base end connected to the shielding metal fitting, and the electric field relaxation layer is formed from the connection position with the shielding metal fitting toward the distal end side, and has a uniform portion having a substantially uniform thickness. , A tip portion where an arc surface is formed, and a tapered portion formed at a position where the uniform portion and the tip portion are connected to each other, and a tapered surface inclined so that the inner diameter decreases toward the tip side And.

  According to the present invention, the electric field relaxation layer is formed at a position where the uniform portion, the tip portion where the circular arc surface is formed, and the uniform portion and the tip portion are continuously provided, and the inner diameter becomes smaller toward the tip side. Since the taper portion is formed with a tapered surface, the electric field in the vicinity of the tip portion of the electric field relaxation layer can be reduced. As a result, corona discharge in the vicinity of the tip portion of the electric field relaxation layer can be suppressed.

The fragmentary sectional view which shows the structure of the polymer cannula of embodiment Sectional drawing which expanded and showed the vicinity of the front-end | tip part of the electric field relaxation layer of the polymer sleeve of embodiment Sectional view showing a comparative example near the tip of the electric field relaxation layer Sectional drawing which expanded and showed the vicinity of the front-end | tip part of the electric field relaxation layer of the polymer sleeve of other embodiment

  First, the process that led to the present invention will be described.

  The inventors of the present invention examined at which position corona discharge is likely to occur in a polymer sleeve having an electric field relaxation layer. As a result of investigation, it was found that when the electric field is concentrated near the tip of the electric field relaxation layer and the operating voltage is high, air discharge is likely to occur on the surface of the buttocks of the polymer coating near the tip of the electric field relaxation layer. It was. In other words, it has been found that lowering the electric field on the buttock surface leads to suppressing the generation of corona discharge. Then, the inventors considered that the shape and arrangement of the tip of the electric field relaxation layer is very important in suppressing corona discharge, and reached the present invention.

  One feature of the present invention is that the electric field relaxation layer includes (i) a uniform portion having a substantially uniform thickness formed from the connection position with the shielding metal fitting toward the tip side, and (ii) a tip portion having an arcuate surface formed. And (iii) a tapered portion that is formed at a position where the uniform portion and the tip portion are connected to each other, and has a tapered surface that is inclined so that the inner diameter decreases toward the tip. It is that. Thereby, the electric field in the vicinity of the tip of the electric field relaxation layer can be reduced, and as a result, the electric field on the surface of the buttocks of the polymer covering near the tip can be reduced, and corona discharge in the polymer cannula can be suppressed. As a result, it is possible to increase the radius of the arc surface of the tip portion of the electric field relaxation layer while suppressing an increase in the volume of the electric field relaxation layer as a whole. Corona discharge in the vicinity of the portion can be further reduced.

  One feature of the present invention is that the polymer cover has a thick part where a collar part is formed and a thin part where a collar part is not formed, and the tip of the electric field relaxation layer is connected to the polymer cover. It is arrange | positioning adjacent to the thick part of. Thereby, since the electric field relaxation layer front end portion where the electric field concentrates can be insulated and reinforced by the thick portion of the flange portion, corona discharge near the front end portion of the electric field relaxation layer can be further reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[1] Overall Configuration of Polymer Cannula FIG. 1 shows an overall configuration of a polymer cannula according to an embodiment of the present invention. FIG. 1 is a partial cross-sectional view showing the vicinity of the central portion in cross section. The polymer sleeve 10 of FIG. 1 is used as a device bushing. Here, the polymer sleeve 10 is fixed to a case of a device such as a transformer on the lower side in the drawing. Specifically, in the polymer cannula 10 of FIG. 1, a proximal end surface of a flange portion 51 of a shielding metal fitting 50 described later is airtightly fixed to a distal end surface of a case (not shown) such as a device. The lower side in the figure is called the base end side, and the upper side in the figure is called the front end side.

  The polymer sleeve 10 includes an inner conductor 20, an insulator 30, a polymer cover 40, a shielding fitting 50, and an electric field relaxation layer 60. In the polymer sleeve 10, the potential at the time of voltage application is that the inner conductor 20 is on the high voltage side and the shielding fitting 50 is on the ground side.

  The inner conductor 20 is formed of a metal rod suitable for energization such as copper. The inner conductor 20 is disposed at the center of the polymer sleeve 10. Further, in the polymer sleeve 10 of FIG. 1 used as a device bushing, both end portions (the distal end portion 21 and the proximal end portion 22) of the inner conductor 20 are formed in a state of being exposed from the insulator 30. The internal conductor 20 is connected to a high-voltage conductor in the device (not shown) at the exposed base end 22. The internal conductor 20 is connected to an overhead wire or a lead-in wire (not shown) at the exposed tip 21.

The insulator 30 is provided so as to cover the outer periphery of the inner conductor 20. The insulator 30 is formed of a material having high mechanical strength, for example, a hard plastic resin such as an epoxy resin or FRP. The insulator 30 is integrally formed with the inner conductor 20 and the shielding metal fitting 50 by molding in a state where the distal end portion 21 and the proximal end portion 22 of the inner conductor 20 are exposed. The vicinity of the distal end side of the shielding metal fitting 50 of the insulator 30 is formed with a larger diameter than the vicinity of the distal end portion of the insulator 30 (the portion corresponding to the small diameter portion 12 described later) (corresponding to the large diameter portion 11 described later). Part to do). The base end portion of the insulator 30 forms a lower bushing 31 on the base end side from the shielding metal fitting 50 in the structure of the device bushing of FIG. The lower bushing 31 is disposed inside the device when the polymer sleeve 10 is installed in the device case. The lower bushing 31 is integrally formed of the same material as the insulator 30. When the polymer sleeve 10 of FIG. 1 is fixed to the case of the device, the lower bushing 31 is disposed in the device. In the embodiment of FIG. 1, the outer periphery of the lower bushing 31 in the device (not shown) is covered with an insulating gas such as SF ₆ (sulfur hexafluoride) gas.

  The polymer covering 40 covers the outer periphery of the insulator 30 from the base end portion to the tip end portion of the insulator 30 on the distal end side of the portion (flange portion 51 in FIG. 1) exposed from the insulator 30 in the shielding metal fitting 50, and A plurality of flange portions 41 are formed on the outer periphery of the heel portion 41 so as to be spaced apart in the longitudinal direction. The polymer covering 40 is formed of a material having excellent electrical insulation performance, for example, a polymer insulating material such as a silicone polymer.

  The shielding metal fitting 50 is embedded in the insulator 30 concentrically with the internal conductor 20 on the proximal end side of the polymer coating 40. The shielding metal fitting 50 includes a flange portion 51 projecting radially outward on the proximal end side of the polymer covering body 40 and an electric field embedded in the insulator 30 in order to fix the polymer cannula 10 at a predetermined attachment location. And a cylindrical portion 52 for relaxation. Therefore, the shielding metal fitting 50 has a function of electric field relaxation here. As a predetermined attachment location, the polymer sleeve 10 shown in FIG. 1 is a device case (not shown). The cylindrical portion 52 is raised at a right angle from the flange portion 51 so that the outer surface faces the electric field relaxation layer 60. The cylindrical portion 52 need not be limited to a structure that rises at a right angle, as long as it has a function of electric field relaxation, and the shielding metal fitting 50 may have any shape as long as it has the effect of the present invention.

  The electric field relaxation layer 60 is disposed at the interface between the insulator 30 and the polymer cover 40. The base end of the electric field relaxation layer 60 is electrically connected to the shielding metal fitting 50. The electric field relaxation layer 60 is formed of a zinc oxide (ZnO) layer or a high dielectric constant layer. For example, the electric field relaxation layer 60 is a zinc oxide layer in which an elastomer material is filled with zinc oxide powder. Further, for example, the electric field relaxation layer 60 may be a high dielectric constant layer having a relative dielectric constant of 10 or more, such as rubber filled with a conductive filler such as carbon black. The electric field relaxation layer 60 is manufactured in the order of electric field relaxation so that the outer periphery of the insulator 30 integrally formed by molding together with the inner conductor 20 and the shielding metal fitting 50 is in electrical contact with the shielding metal fitting 50 on the base end side. The layer 60 is integrally formed by molding, and then the polymer covering 40 is integrally formed by molding on the outer periphery of the electric field relaxation layer 60 and the outer periphery of the insulator 30 where the electric field relaxation layer 60 is not formed on the outer periphery. Form.

  Incidentally, in the case of the present embodiment, the polymer cannula 10 is constituted by the large-diameter portion 11 in the vicinity of the distal end side of the shielding metal fitting 50 and the small-diameter portion 12 on the distal end side with respect to the large-diameter portion 11, and at least large. An electric field relaxation layer 60 is formed at the interface between the insulator 30 and the polymer coating 40 in the diameter portion 11. Thereby, the electric field intensity of the air surface of the polymer sleeve 10 can be lowered, and the heat generation of the electric field relaxation layer 60 can be suppressed.

  The insulator 30, the polymer coating 40, and the electric field relaxation layer 60 are integrally formed by molding.

[2] Electric field relaxation layer Next, the electric field relaxation layer 60 will be described in detail.

  As shown in FIG. 2 in which the vicinity of the distal end of the electric field relaxation layer 60 is enlarged, the electric field relaxation layer 60 is formed on the outer periphery of the insulator 30 from the connection position with the shielding metal fitting 50 toward the distal end side, and has a substantially uniform thickness. The uniform part 61, the tip part 62 formed with the circular arc surface 62a, and the tapered surface formed at a position where the uniform part 61 and the tip part 62 are connected to each other and inclined so that the inner diameter decreases toward the tip side. And a tapered portion 63 in which 63a is formed. Here, as the shape of the tip portion 62 where the arc surface 62a is formed, the tip portion 62 as a whole is arcuate as shown in FIG. The portion 62 includes a case where the portion 62 is flat (perpendicular to the axial direction) and a case where the inside and outside of the tip end portion 62 are arc-shaped and the center of thickness is flat (perpendicular to the axial direction).

  Here, assuming that the thickness of the uniform portion 61 is d and the radius of the arc of the arc surface 62a of the tip 62 having a circular arc shape (that is, an arc surface) is r, the radius r is r> d. Is more preferable. As a result of the electric field analysis of the polymer cannula with this configuration, the electric field strength on the surface of the collar portion 41 of the polymer covering 40 in the vicinity of the tip of the electric field relaxation layer 60 in FIG. It turned out that it becomes low compared with the electric field strength of the collar part 41 surface of the polymer coating 40. From this, by setting r> d, the radius of the arc surface 62a of the tip 62 of the electric field relaxation layer 60 can be increased while suppressing an increase in the volume of the electric field relaxation layer 60 as a whole. Compared to the case where the electric field relaxation layer 60 is formed thick, corona discharge in the vicinity of the tip 62 of the electric field relaxation layer 60 can be reduced without consuming unnecessary materials. That is, since the electric field relaxation layer 60 is formed of a zinc oxide (ZnO) layer or a high dielectric constant layer, the material cost for forming the electric field relaxation layer 60 is expensive, so it is desired to suppress an increase in the volume of the electric field relaxation layer 60. . Therefore, according to the present embodiment, the corona discharge in the vicinity of the front end portion 62 of the electric field relaxation layer 60 can be reduced without forming the thickness d thick in the entire length of the electric field relaxation layer 60. For example, the thickness d is 5 [mm] and the radius r is 6 [mm].

  In addition, it was found that the electric field strength on the heel surface of the polymer coating was higher in the polymer sleeve in which r ≦ d than in the polymer sleeve in which r> d. In the polymer sleeve in which r ≦ d, even when the tapered portion 63 is provided on the distal end side of the uniform portion 61 so that the thickness of the distal end side of the electric field relaxation layer 60 is larger than that of the uniform portion 61, the radius r of the arc Therefore, the electric field is concentrated on the tip of the electric field relaxation layer 60, and as a result, the effect of reducing the electric field on the surface of the flange 41 of the polymer coating 40 is small. As a result, the electric field strength of the surface of the collar portion 41 of the polymer covering 40 is higher than that of the polymer sleeve having the uniform thickness of the electric field relaxation layer 60 and the arc surface 62a formed at the tip as in the comparative example of FIG. It didn't change.

  As shown in FIG. 4, it is more preferable that the tip of the electric field relaxation layer 60 of the polymer cannula 10 is disposed adjacent to the thick part where the flange 41 of the polymer coating 40 is formed. That is, in the example of FIG. 2, the case where the tip of the electric field relaxation layer 60 is disposed adjacent to the thin portion where the flange portion 41 of the polymer coating 40 is not formed is illustrated, but the arrangement illustrated in FIG. As compared with the arrangement shown in FIG. 2, the distal end portion 62 of the electric field relaxation layer 60 where the electric field is concentrated can be insulated and reinforced by the thick portion of the flange portion 41. When the electric field analysis was performed under the same condition of r> d, it was found that the electric field strength on the surface of the collar portion 41 of the polymer covering 40 was lower in the case of FIG. 4 than in the case of FIG. Therefore, corona discharge in the polymer sleeve 10 can be further reduced.

  In particular, when r> d in the configuration of FIG. 4, both the effect of r> d and the effect of being disposed adjacent to the thick portion can be obtained, which is very useful for reducing corona discharge. It is.

[3] Other Embodiments In the above-described embodiments, the case where the present invention is applied to the polymer sleeve 10 having the large diameter portion 11 and the small diameter portion 12 has been described. However, the present invention is not limited to this. The same effect can be obtained when applied to a straight type polymer sleeve having the same outer diameter in the longitudinal direction.

  In the above-described embodiment, the case where the polymer cannula 10 is used as a device bushing has been described. However, a structure of a polymer cannula used as a through-wall bushing (see Patent Document 3) or an insulator 30 may be used. The structure of the polymer sleeve used for the cable terminal connection part which has a connection part of a cable terminal in the base end side of this may be sufficient. Further, as the polymer sleeve used for the cable terminal connection portion, a so-called inner cone type for receiving a stress cone in the insulator 30 and an insulation system of RBJ (rubber block joint), both known to those skilled in the art. As described above, there is a so-called outer cone type in which the rubber sleeve is covered on the outer periphery of the insulator to connect the polymer sleeve and the cable, but the present invention can be applied to any of them, and these structures are not particularly limited. In other words, the polymer sleeve of the present invention may be applied to a bushing for equipment connected to equipment (such as a GIS (gas insulated switchgear) or a transformer) as shown in FIG. Alternatively, the present invention may be applied to a cable terminal connection portion connected to a cable.

  The polymer sleeve of the present invention has an effect of suppressing the generation of corona discharge from the polymer coating, and is useful as, for example, a cable terminal connection portion or a bushing (such as a device bushing or a wall penetration bushing).

DESCRIPTION OF SYMBOLS 10 Polymer sleeve 11 Large diameter part 12 Small diameter part 20 Inner conductor 30 Insulator 40 Polymer coating body 41 Gutter part 50 Shielding metal fitting 51 Flange part 52 Cylindrical part 60 Electric field relaxation layer 61 Uniform part 62 Tip part 62a Arc surface 63 Tapered part 63a Tapered surface

Claims (5)

An inner conductor,
A hard insulator covering the outer periphery of the inner conductor;
Covering the outer periphery of the insulator, and a polymer covering formed with a plurality of flanges spaced apart in the longitudinal direction on the outer periphery;
On the base end side of the polymer covering, a shielding fitting embedded in the insulator concentrically with the inner conductor;
An electric field relaxation layer disposed at an interface between the insulator and the polymer covering, and having a base end connected to the shielding fitting;
Comprising
The electric field relaxation layer is
A uniform part that is formed from the connection position with the shielding metal fitting toward the front end side, and has a substantially uniform thickness,
A tip where an arc surface is formed;
A taper part formed at a position where the uniform part and the tip part are continuously provided, and a tapered surface inclined so that the inner diameter decreases toward the tip side;
Comprising
Polymer sleeve. When the thickness of the uniform portion is d and the radius of the circular arc surface is r, the electric field relaxation layer has r> d.
The polymer sleeve according to claim 1. The shielding metal fitting is
A flange portion projecting radially outward from the polymer covering,
A cylindrical portion for electric field relaxation embedded in the insulator;
Having
The polymer cannula according to claim 1 or claim 2. The polymer covering has a thick part where the collar part is formed, and a thin part where the collar part is not formed,
The electric field relaxation layer has a tip adjacent to the thick part of the polymer covering,
The polymer cannula according to any one of claims 1 to 3. The electric field relaxation layer is composed of a zinc oxide layer or a high dielectric constant layer.
The polymer cannula according to any one of claims 1 to 4.

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