JP2023078809A

JP2023078809A - Polymer bushing insulator

Info

Publication number: JP2023078809A
Application number: JP2021192097A
Authority: JP
Inventors: 未沙田渡; Misa Tado
Original assignee: SWCC Showa Cable Systems Co Ltd
Current assignee: SWCC Corp
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2023-06-07
Anticipated expiration: 2041-11-26
Also published as: JP7495386B2

Abstract

To a polymer bushing insulator that can improve insulation performance while securing a required surface leakage distance.SOLUTION: A polymer bushing insulator comprises: a polymer-coated body including a rod-like inner conductor arranged at a center, a hard insulation cylinder integrally formed on an outer periphery of the inner conductor, a shield metal fitting embedded in the insulation cylinder concentrically with the inner conductor, a trunk part covering the outer periphery of the insulation cylinder, and a plurality of umbrella-shaped pleat parts formed on the outer periphery of the trunk part so as to be separated from each other in a longitudinal direction; and an electric field relaxation layer that is formed of a zinc oxide layer and a high dielectric constant layer and is arranged along an interface between the insulation cylinder and the polymer coated body, a rear end of the electric field relaxation layer being connected to the shield metal fitting. The plurality of pleat parts include: a small pleat part; a large pleat part with a projection length larger than that of the small pleat part; and an oversized pleat part with a projection length larger than that of the large pleat part. The oversized pleat part includes a first oversized pleat part, which is arranged at any one of positions of first to third pleats toward a tip side with reference to a position corresponding to the tip end of the electric field relaxation layer in the polymer coated body.SELECTED DRAWING: Figure 1

Description

本発明は、ポリマー套管に関する。 The present invention relates to polymeric sleeves.

近年、套管の軽量化、スリム化、縮小化、套管種類の共通化及び作業工程の簡略化などを図る観点から、エポキシ樹脂等からなる絶縁筒の外周面にシリコーンゴム等からなるポリマー被覆体を直接モールド成形した固体絶縁構造（完全乾式）のポリマー套管が実用化されている（例えば特許文献１～４）。このようなポリマー套管は、ダイレクトモールド型と称される。 In recent years, from the viewpoint of reducing the weight, slimming, and miniaturization of sleeves, standardizing the types of sleeves, and simplifying the work process, the outer peripheral surface of an insulating tube made of epoxy resin or the like is coated with a polymer made of silicone rubber or the like. Polymer sleeves with a solid insulating structure (completely dry type) in which the body is directly molded have been put into practical use (for example, Patent Documents 1 to 4). Such polymer sleeves are referred to as direct molded.

ダイレクトモールド型のポリマー套管において、ポリマー被覆体は、通常、絶縁筒の外周を覆う胴部と、胴部の外周に長手方向に離間して形成される傘状の襞部と、を有している。また、耐コロナ特性を向上させるために、絶縁筒とポリマー被覆体との界面には、酸化亜鉛層又は高誘電率層からなる電界緩和層が配置される（特許文献１、３、４参照）。特に、特許文献４に開示のポリマー套管では、電界緩和層の先端部に対応する外周位置において、ポリマー被覆体の胴部を肉厚に形成することにより、耐コロナ特性のさらなる向上が図られている。 In a direct-molded polymer sleeve, the polymer sheath usually has a body that covers the outer periphery of the insulating tube and umbrella-shaped folds that are formed on the outer periphery of the body at intervals in the longitudinal direction. ing. In order to improve the corona resistance, an electric field relaxation layer made of a zinc oxide layer or a high dielectric constant layer is arranged at the interface between the insulating cylinder and the polymer coating (see Patent Documents 1, 3, and 4). . In particular, in the polymer sleeve disclosed in Patent Document 4, the corona resistance is further improved by forming the body portion of the polymer coating thicker at the outer peripheral position corresponding to the tip portion of the electric field relaxation layer. ing.

特開２０１２－７５２６６号公報JP 2012-75266 A 特開２００７－１８８７３５号公報JP 2007-188735 A 特開２００９－５５１４号公報JP 2009-5514 A 特開２０１６－１４０１９５号公報JP 2016-140195 A

ところで、磁器套管においては、表面を流れる電気を確実に絶縁するために必要な表面漏洩距離が規格によって定められている。電圧階級が高電圧になるほど長い表面漏洩距離が要求される。近年、ダイレクトモールド型を含むポリマー套管も汚損設計基準曲線が規格で定められ、表面漏洩距離が新たに制定された（例えば、ＪＥＣ－５２０２）。また、ダイレクトモールド型を含むポリマー套管においては、電圧階級が高電圧になるほど高い絶縁性能が要求される。ここで要求される絶縁性能には、例えば、汚損交流耐電圧特性、乾燥および注水商用周波閃絡特性が含まれる。 By the way, in the porcelain sleeve, the surface leakage distance required to reliably insulate the electricity flowing on the surface is defined by standards. As the voltage class becomes higher, a longer surface leakage distance is required. In recent years, a fouling design criterion curve has been standardized for polymer sleeves including direct molds, and a surface leakage distance has been newly established (eg, JEC-5202). Further, in the polymer sleeve including the direct mold type, the higher the voltage class, the higher the insulation performance is required. The insulation performance required here includes, for example, fouling AC withstand voltage characteristics, dry and flooded commercial frequency flashover characteristics.

本発明の目的は、要求される表面漏洩距離を確保できるとともに、さらに絶縁性能を向上できるポリマー套管を提供することである。 SUMMARY OF THE INVENTION An object of the present invention is to provide a polymer sleeve that can ensure a required surface leakage distance and further improve insulation performance.

本発明に係るポリマー套管は、
中心に配置される棒状の内部導体と、
前記内部導体の外周に一体的に形成される硬質の絶縁筒と、
前記内部導体と同心状に前記絶縁筒に埋設される遮へい金具と、
前記絶縁筒の外周を覆う胴部と、前記胴部の外周に長手方向に離間して形成される複数の傘状の襞部と、を有するポリマー被覆体と、
酸化亜鉛層又は高誘電率層で構成され、前記絶縁筒と前記ポリマー被覆体との界面に沿って配置され、後端部が前記遮へい金具に接続される電界緩和層と、を備え、
複数の前記襞部は、小襞部と、前記小襞部よりも前記胴部から径方向への突出長が大きい大襞部と、前記大襞部よりも前記胴部から径方向への突出長が大きい特大襞部と、を有し、
前記特大襞部は、前記ポリマー被覆体において前記電界緩和層の先端部に対応する位置を基準として、先端側に向かって１枚目から３枚目のいずれかの位置に配置される第１特大襞部を含む。 The polymer cannula according to the present invention comprises:
a rod-shaped inner conductor arranged at the center;
a hard insulating cylinder integrally formed around the outer periphery of the internal conductor;
a shielding fitting embedded in the insulating cylinder concentrically with the inner conductor;
a polymer covering having a body covering the outer periphery of the insulating tube, and a plurality of umbrella-shaped folds formed on the outer periphery of the body at intervals in the longitudinal direction;
an electric field relaxation layer composed of a zinc oxide layer or a high dielectric constant layer, disposed along the interface between the insulating cylinder and the polymer coating, and having a rear end connected to the shielding metal fitting,
The plurality of folds includes a small fold, a large fold having a longer projection length from the trunk in the radial direction than the small fold, and a radial projection from the trunk that is greater than the large fold. and an oversized fold having a large length;
The extra-large folds are the first extra-large folds arranged at any position from the first sheet to the third sheet toward the tip side with reference to the position corresponding to the tip part of the electric field relaxation layer in the polymer coating. Including folds.

本発明のポリマー套管によれば、要求される表面漏洩距離を確保できるとともに、さらに絶縁性能を向上できる。 According to the polymer cannula of the present invention, the required surface leakage distance can be secured and the insulation performance can be further improved.

図１は、実施の形態に係るポリマー套管の全体構成を示す部分断面図である。FIG. 1 is a partial cross-sectional view showing the overall configuration of a polymer cannula according to an embodiment. 図２は、特大襞部の配置態様の一例を示す図である。FIG. 2 is a diagram showing an example of an arrangement mode of oversized folds. 図３は、変形例に係るポリマー套管の全体構成を示す部分断面図である。FIG. 3 is a partial cross-sectional view showing the overall configuration of a polymer cannula according to a modification.

以下、本発明の実施の形態を図面に基づいて詳細に説明する。
図１は、本発明の実施の形態に係るポリマー套管１の全体構成を示す部分断面図である。以下において、図中、上側を「先端側Ｓ１」、下側を「後端側Ｓ２」と称する。図１に示すポリマー套管１は、後端側Ｓ２に変圧器等の電力機器内に配置されるヘッド部Ｈを有する機器用ブッシングである。 BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional view showing the overall configuration of a polymer cannula 1 according to an embodiment of the invention. Hereinafter, in the drawings, the upper side is referred to as "front end side S1" and the lower side is referred to as "rear end side S2". A polymer bushing 1 shown in FIG. 1 is a device bushing having a head portion H disposed in a power device such as a transformer on the rear end side S2.

図１に示すように、ポリマー套管１は、中心に配置される棒状の内部導体１０、内部導体１０の外周に設けられる絶縁筒２０、絶縁筒２０と一体的に形成される遮へい金具３０、絶縁筒２０の外周に設けられるポリマー被覆体４０、及び絶縁筒２０とポリマー被覆体４０の界面に配置される電界緩和層５０等を備える。 As shown in FIG. 1, the polymer sleeve 1 includes a rod-shaped inner conductor 10 arranged in the center, an insulating tube 20 provided on the outer periphery of the inner conductor 10, a shielding metal fitting 30 integrally formed with the insulating tube 20, It includes a polymer coating 40 provided on the outer periphery of the insulating tube 20, and an electric field relaxation layer 50 disposed at the interface between the insulating tube 20 and the polymer coating 40, and the like.

内部導体１０、絶縁筒２０、遮へい金具３０、ポリマー被覆体４０、及び電界緩和層５０は、モールド成型により一体的に形成される。具体的には、内部導体１０と遮へい金具３０とを金型にセットした状態で絶縁筒２０がモールド成型される。そして、モールド成型した絶縁筒２０が電界緩和層成型用の金型にセットされ、後述するように絶縁筒２０の大径部２３の外周面に電界緩和層５０がモールド成型される。さらに、電界緩和層５０をモールド成型したものがポリマー被覆体成型用の金型にセットされ、絶縁筒２０及び電界緩和層５０の外周面にポリマー被覆体４０がモールド成型される。なお、ポリマー套管１において、課電時の電位は、内部導体１０が高電位、遮へい金具３０が接地電位となる。 The inner conductor 10, the insulating tube 20, the shielding metal fitting 30, the polymer coating 40, and the electric field relaxation layer 50 are integrally formed by molding. Specifically, the insulating cylinder 20 is molded while the inner conductor 10 and the shielding metal fitting 30 are set in a mold. Then, the molded insulating cylinder 20 is set in a mold for molding the electric field relaxation layer, and the electric field relaxation layer 50 is molded on the outer peripheral surface of the large diameter portion 23 of the insulating cylinder 20 as described later. Further, the molded electric field relaxation layer 50 is set in a mold for molding the polymer coating, and the polymer coating 40 is molded on the outer peripheral surfaces of the insulating cylinder 20 and the electric field relaxation layer 50 . In addition, in the polymer sleeve 1, the internal conductor 10 has a high potential and the shielding metal fitting 30 has a ground potential when voltage is applied.

内部導体１０は、例えば銅、アルミニウム、銅合金又はアルミニウム合金等からなる通電に適した導電性材料で構成される。ポリマー套管１では、内部導体１０の両端部（先端部１１及び後端部１２）は、絶縁筒２０から露出した状態とされる。内部導体１０の先端部１１は架空線や引き込み線（図示略）などに接続され、内部導体１０の後端部１２は電力機器内の高電圧導体に接続される。 The internal conductor 10 is made of a conductive material suitable for conducting electricity, such as copper, aluminum, a copper alloy, or an aluminum alloy. In the polymer cannula 1 , both ends (front end 11 and rear end 12 ) of the inner conductor 10 are exposed from the insulating tube 20 . A front end portion 11 of the inner conductor 10 is connected to an overhead line or a lead-in line (not shown), and a rear end portion 12 of the inner conductor 10 is connected to a high voltage conductor in power equipment.

絶縁筒２０は、例えばエポキシ樹脂やＦＲＰ（Fiber Reinforced Plastics）など、機械的強度の高い硬質プラスチック樹脂材料で構成される。絶縁筒２０は、先端側Ｓ１に直胴状に形成された小径部２１、小径部２１から後端側Ｓ２に向けて緩やかに拡径するテーパー部２２、テーパー部２２の後端側Ｓ２に直胴状に形成された大径部２３を有する。また、絶縁筒２０の後端部は、電力機器内に配置されるヘッド部Ｈを構成する。ここで、絶縁筒２０の後端部とは、大径部２３の後端側Ｓ２、すなわち遮へい金具３０のフランジ部３２より後端側Ｓ２に大径部２３と連設される部分を意味する。 The insulating cylinder 20 is made of a rigid plastic resin material having high mechanical strength, such as epoxy resin or FRP (Fiber Reinforced Plastics). The insulating cylinder 20 has a small-diameter portion 21 formed in a straight body shape on the front end side S1, a tapered portion 22 that gradually expands in diameter from the small-diameter portion 21 toward the rear end side S2, and a tapered portion 22 that extends directly to the rear end side S2. It has a large-diameter portion 23 formed in a trunk shape. Further, the rear end portion of the insulating cylinder 20 constitutes a head portion H arranged inside the power equipment. Here, the rear end portion of the insulating tube 20 means the rear end side S2 of the large diameter portion 23, that is, the portion connected to the large diameter portion 23 from the flange portion 32 of the shielding metal fitting 30 to the rear end side S2. .

絶縁筒２０を全体的に大径化すると、ポリマー套管１の表面電位を容易に下げることができるが、ポリマー套管１に要求される耐震性、耐曲げ荷重性が低下する。絶縁筒２０を小径部２１、テーパー部２２、大径部２３からなる構造とすることで、電気的性能と、耐震性、曲げ荷重性の両立を図ることができる。 If the diameter of the insulating tube 20 is increased as a whole, the surface potential of the polymer sleeve 1 can be easily lowered, but the earthquake resistance and bending load resistance required of the polymer sleeve 1 are lowered. By configuring the insulating tube 20 to have a structure including the small diameter portion 21, the tapered portion 22, and the large diameter portion 23, it is possible to achieve both electrical performance, earthquake resistance, and bending load resistance.

遮へい金具３０は、絶縁筒２０の大径部２３に内部導体１０と同心状に埋設される円筒部３１と、円筒部３１の後端から径方向外側に延出するフランジ部３２とを有する。円筒部３１は電界緩和機能を有し、ポリマー套管１の電界を緩和する。フランジ部３２をＯリング等のシール部材（図示略）を介して電力機器のケースＣに載置した状態でボルト等の接続部材（図示略）で接続することにより、ポリマー套管１は電力機器に気密・水密に固定される。 The shielding metal fitting 30 has a cylindrical portion 31 embedded concentrically with the inner conductor 10 in the large diameter portion 23 of the insulating tube 20 and a flange portion 32 extending radially outward from the rear end of the cylindrical portion 31 . The cylindrical portion 31 has an electric field relaxation function and relaxes the electric field of the polymer sleeve 1 . By connecting the flange portion 32 to the case C of the electric power device via a sealing member (not shown) such as an O-ring and connecting it with a connection member (not shown) such as a bolt, the polymer sleeve 1 can be connected to the electric power device. is airtight and watertight.

ポリマー被覆体４０は、電気絶縁性能に優れる材料（例えばシリコーンポリマーなどの高分子材料）で構成される。ポリマー被覆体４０は、絶縁筒２０のヘッド部Ｈを除く部分の外周を覆うように形成される。すなわち、ポリマー被覆体４０は、遮へい金具３０のフランジ部３２より先端側Ｓ１の絶縁筒２０の外周を覆うように形成される。ポリマー被覆体４０は、絶縁筒２０の外周を覆う胴部４１と、胴部４１の外周に長手方向に離間して形成される複数の傘状の襞部４２とを有する。 The polymer coating 40 is made of a material with excellent electrical insulation performance (for example, a polymeric material such as silicone polymer). The polymer covering 40 is formed so as to cover the outer periphery of the insulating cylinder 20 excluding the head portion H. As shown in FIG. That is, the polymer coating 40 is formed so as to cover the outer periphery of the insulating tube 20 on the tip side S1 from the flange portion 32 of the shielding metal fitting 30 . The polymer covering 40 has a trunk portion 41 that covers the outer circumference of the insulating tube 20 and a plurality of umbrella-shaped folds 42 that are formed on the outer circumference of the trunk portion 41 at intervals in the longitudinal direction.

本実施の形態では、襞部４２として、小襞部４３と、小襞部４３よりも胴部４１から径方向外側への突出長が大きい大襞部４４と、大襞部４４よりも胴部４１から径方向外側への突出長が大きい特大襞部４５と、が設けられている。具体的には、長手方向にわたって、小襞部４３と大襞部４４が交互に形成されており、長手方向における特定部位において大襞部４４に代えて特大襞部４５が形成されている。
大襞部４４の突出長は、例えば、小襞部４３の１．０５～１．２５倍に設定される。特大襞部４５の突出長は、例えば、大襞部４４の１．０５～１．２５倍に設定される。好ましくは、特大襞部４５の突出長は、特大襞部４５の外径が遮へい金具３０のフランジ部３２の外径以下となるよう設定される。特大襞部４５の数及び突出長は、ポリマー套管１に要求される表面漏洩距離に応じて設定される。特大襞部４５の位置については、後述する。 In the present embodiment, as the folds 42, the small folds 43, the large folds 44 having a larger projection length radially outward from the body 41 than the small folds 43, and the body larger than the large folds 44 An extra-large fold 45 having a large projection length radially outward from 41 is provided. Specifically, small pleats 43 and large pleats 44 are alternately formed along the longitudinal direction, and oversized pleats 45 are formed instead of the large pleats 44 at specific locations in the longitudinal direction.
The protruding length of the large folds 44 is set to 1.05 to 1.25 times that of the small folds 43, for example. The protruding length of the extra-large folds 45 is set to 1.05 to 1.25 times that of the large folds 44, for example. Preferably, the projection length of the oversized folds 45 is set so that the outer diameter of the oversized folds 45 is equal to or less than the outer diameter of the flange portion 32 of the shielding metal fitting 30 . The number and protrusion length of the oversized folds 45 are set according to the surface leakage distance required for the polymer cannula 1 . The position of the oversized folds 45 will be described later.

電界緩和層５０は、酸化亜鉛（ＺｎＯ）層又は高誘電率層で形成される。具体的には、例えば、電界緩和層５０は、樹脂材料に酸化亜鉛粉末を充填した酸化亜鉛層、又は、カーボンブラック等の導電性フィラーを充填したゴム等の比誘電率が１０以上の高誘電率層で構成される。電界緩和層５０は、絶縁筒２０の大径部２３の外周面にモールド成型により絶縁筒２０と一体的に形成される。すなわち、電界緩和層５０は、ポリマー套管１において、絶縁筒２０の大径部２３とポリマー被覆体４０との界面に沿って設けられる。 The electric field relaxation layer 50 is formed of a zinc oxide (ZnO) layer or a high dielectric constant layer. Specifically, for example, the electric field relaxation layer 50 is a zinc oxide layer in which zinc oxide powder is filled in a resin material, or a high dielectric layer such as a rubber layer filled with a conductive filler such as carbon black having a dielectric constant of 10 or more. It consists of rate layers. The electric field relaxation layer 50 is integrally formed with the insulating tube 20 by molding on the outer peripheral surface of the large diameter portion 23 of the insulating tube 20 . That is, the electric field relaxation layer 50 is provided along the interface between the large diameter portion 23 of the insulating tube 20 and the polymer coating 40 in the polymer sleeve 1 .

絶縁筒２０の大径部２３とポリマー被覆体４０との界面に電界緩和層５０を設ける方法として、電界緩和層５０が径方向外側に出っ張らないように電界緩和層５０の外径が絶縁筒２０の大径部２３の外径と同一になるように形成する方法、または電界緩和層５０の内径が絶縁筒２０の大径部２３の外径と同一になるように形成する方法が考えられる。 As a method of providing the electric field relaxation layer 50 at the interface between the large-diameter portion 23 of the insulating cylinder 20 and the polymer coating 40, the outer diameter of the electric field relaxation layer 50 is adjusted to the insulating cylinder 20 so that the electric field relaxation layer 50 does not protrude radially outward. A method of forming the electric field relaxation layer 50 so as to have the same outer diameter as the large diameter portion 23 of the insulating tube 20 or a method of forming the electric field relaxation layer 50 so as to have the same outer diameter as the large diameter portion 23 of the insulating cylinder 20 can be considered.

本実施の形態では、電界緩和層５０の成型の容易性から、電界緩和層５０は、図１に示すように、絶縁筒２０の大径部２３の外周に、電界緩和層５０の内径が絶縁筒２０の大径部２３の外径と同一になるように形成される。すなわち、電界緩和層５０がある部分と電界緩和層５０のない部分とで、ポリマー被覆体４０の胴部４１の厚さが異なる。具体的には、電界緩和層５０がある部分のポリマー被覆体４０の胴部４１の厚さが、電界緩和層５０がない部分の胴部４１の厚さよりも薄い。これにより、ポリマー套管１の高電圧化（例えば１１０ｋＶ級以上）への適用を考えた場合、電界緩和層５０の先端部５１に対応する位置の胴部４１の厚さが薄いため、電界緩和層５０の先端部５１近傍のポリマー被覆体４０においては気中放電が生じやすくなる。しかし、ポリマー套管１は、電界緩和層５０の先端部５１の近傍に特大襞部４５を有するので、気中放電が生じるのを抑えることができる。 In this embodiment, due to the ease of molding the electric field relaxation layer 50, as shown in FIG. It is formed to have the same outer diameter as the large diameter portion 23 of the cylinder 20 . That is, the thickness of the body portion 41 of the polymer coating 40 differs between the portion with the electric field relaxation layer 50 and the portion without the electric field relaxation layer 50 . Specifically, the thickness of the body portion 41 of the polymer coating 40 where the electric field relaxation layer 50 is present is thinner than the thickness of the body portion 41 where the electric field relaxation layer 50 is absent. As a result, when considering the application of the polymer sleeve 1 to higher voltages (for example, 110 kV class or higher), the thickness of the body portion 41 at the position corresponding to the tip portion 51 of the electric field relaxation layer 50 is thin, so that the electric field relaxation Air discharge is likely to occur in the polymer coating 40 near the tip 51 of the layer 50 . However, since the polymer sleeve 1 has the extra-large folds 45 in the vicinity of the tip 51 of the electric field relaxation layer 50, it is possible to suppress the occurrence of air discharge.

絶縁筒２０の大径部２３の長手方向の長さは、電界緩和層５０の長手方向の長さよりも長くなっている。すなわち、電界緩和層５０は、絶縁筒２０の大径部２３に位置する。また、電界緩和層５０の後端は、遮へい金具３０に電気的に接続される。電界緩和層５０は、絶縁筒２０の大径部２３の外周面に形成されるので、全体が同一径となる。大径部２３に電界緩和層５０を形成することにより電界分布が最適化されるので、ポリマー套管１の電気的性能が向上する。 The longitudinal length of the large-diameter portion 23 of the insulating cylinder 20 is longer than the longitudinal length of the electric field relaxation layer 50 . That is, the electric field relaxation layer 50 is located in the large diameter portion 23 of the insulating cylinder 20 . Also, the rear end of the electric field relaxation layer 50 is electrically connected to the shield metal fitting 30 . Since the electric field relaxation layer 50 is formed on the outer peripheral surface of the large-diameter portion 23 of the insulating cylinder 20, the diameter of the whole is the same. Since the electric field distribution is optimized by forming the electric field relaxation layer 50 in the large diameter portion 23, the electrical performance of the polymer cannula 1 is improved.

図２は、特大襞部４５の配置態様の一例を示す図である。図２では、ポリマー套管１における電界緩和層５０の先端部の近傍及び遮へい金具３０のフランジ部３２の近傍を拡大して示している。 FIG. 2 is a diagram showing an example of an arrangement mode of the oversized folds 45. As shown in FIG. FIG. 2 shows an enlarged view of the vicinity of the tip portion of the electric field relaxation layer 50 in the polymer sleeve 1 and the vicinity of the flange portion 32 of the shielding metal fitting 30 .

図２に示すように、特大襞部４５の一例である第１特大襞部４５１は、電界緩和層５０の先端部５１の先端側Ｓ１の近傍に配置されている。ポリマー套管１において、電界緩和層５０の先端部５１は、電界が集中しやすく、放電を生じやすい。そのため、ポリマー套管１の後端側Ｓ２の低電位部で生じた放電は、電界緩和層５０の先端部５１に対応する表面を中継して、先端側Ｓ１の高電位部と後端側Ｓ２の低電位部との間で繋がろうとする。ここで、ポリマー套管１０の後端側Ｓ２の低電位部とは、例えば、遮へい金具３０の取付用のボルト（図示略）を意味する。また、ポリマー套管１０の先端側Ｓ１の高電位部とは、例えば、内部導体１０の先端部１１に取り付けられる端子等の金具（図示略）を意味する。本実施の形態では、電界緩和層５０の先端部５１の先端側Ｓ１の近傍に第１特大襞部４５１を配置することにより、低電位部と高電位部との間で生じる放電が繋がるのを抑制する、いわゆるバリア効果が得られる。ここで、バリア効果により抑制される放電には、低電位部から高電位部に向かうもの、および高電位部から低電位部に向かうものの、いずれの場合も含まれる。 As shown in FIG. 2 , the first oversized fold 451 , which is an example of the oversized fold 45 , is arranged in the vicinity of the front end side S 1 of the front end 51 of the electric field relaxation layer 50 . In the polymer cannula 1, the electric field tends to concentrate at the tip 51 of the electric field relaxation layer 50, and discharge tends to occur. Therefore, the discharge generated at the low potential portion on the rear end side S2 of the polymer cannula 1 is relayed through the surface corresponding to the front end portion 51 of the electric field relaxation layer 50, and the high potential portion on the front end side S1 and the rear end side S2 are discharged. try to connect with the low potential part of Here, the low potential portion on the rear end side S2 of the polymer sleeve 10 means, for example, a bolt (not shown) for mounting the shielding metal fitting 30 . Further, the high potential portion on the distal end side S1 of the polymer cannula 10 means, for example, a metal fitting (not shown) such as a terminal attached to the distal end portion 11 of the inner conductor 10 . In the present embodiment, by arranging the first extra-large fold portion 451 near the tip side S1 of the tip portion 51 of the electric field relaxation layer 50, the discharge generated between the low potential portion and the high potential portion is prevented from being connected. A so-called barrier effect is obtained. Here, the discharge suppressed by the barrier effect includes both discharge from a low potential portion to a high potential portion and discharge from a high potential portion to a low potential portion.

ここで、「先端側Ｓ１の近傍」とは、ポリマー被覆体４０において電界緩和層５０の先端部５１に対応する位置を基準として、先端側Ｓ１に向かって１枚目から３枚目のいずれかの位置、すなわち、第１特大襞部４５１によってバリア効果が得られる位置であればよく、好ましくは、電界緩和層５０の先端部５１に対応する外周位置を基準Ｐ０として、先端側Ｓ１に向かって１枚目の襞の位置Ｐ１又は２枚目の襞の位置Ｐ２である。図２では、第１特大襞部４５１は、１枚目の襞の位置Ｐ１に配置されている。 Here, "the vicinity of the tip side S1" refers to any one of the first to third sheets toward the tip side S1 with the position corresponding to the tip portion 51 of the electric field relaxation layer 50 in the polymer coating 40 as a reference. , that is, the position where the barrier effect can be obtained by the first oversized fold 451. Preferably, the outer peripheral position corresponding to the tip 51 of the electric field relaxation layer 50 is used as the reference P0, and toward the tip side S1 The fold position P1 of the first sheet or the fold position P2 of the second sheet. In FIG. 2, the first extra-large fold portion 451 is arranged at the fold position P1 of the first sheet.

また、特大襞部４５の他の一例である第２特大襞部４５２は、電界が集中する遮へい金具３０の円筒部３１の先端より後端側Ｓ２に配置される。実施の形態では、第２特大襞部４５２は、ポリマー套管１における遮へい金具３０のフランジ部３２の近傍に配置されている。図２では、第２特大襞部４５２は、フランジ部３２から２枚目の襞の位置に配置されている。フランジ部３２の近傍に第２特大襞部４５２を配置することにより、ポリマー套管１における後端側Ｓ２の低電位部で生じる放電が、電界緩和層５０の先端部５１の近傍で生じる放電と繋がりにくくなる。 A second extra-large fold 452, which is another example of the extra-large fold 45, is arranged on the rear end side S2 from the tip of the cylindrical portion 31 of the shielding metal fitting 30 where the electric field concentrates. In an embodiment, the second oversized fold 452 is located near the flange portion 32 of the shielding fitting 30 in the polymer sleeve 1 . In FIG. 2 , the second oversized fold portion 452 is arranged at the second fold position from the flange portion 32 . By arranging the second extra-large fold portion 452 near the flange portion 32, the discharge generated in the low-potential portion on the rear end side S2 of the polymer sleeve 1 is different from the discharge generated near the tip portion 51 of the electric field relaxation layer 50. It becomes difficult to connect.

また、ポリマー套管１は、特大襞部４５として、第１特大襞部４５１及び第２特大襞部４５２とは異なる位置に配置される第３特大襞部４５３を有する。第３特大襞部４５３は、例えば、第１特大襞部４５１よりも先端側Ｓ１に、所定の間隔を空けて配置される。本実施の形態では、ポリマー套管１の先端部と、第１特大襞部４５１の間に、２つの第３特大襞部４５３が配置されている。具体的には、ポリマー套管１の小径部２１の先端側Ｓ１と後端側Ｓ２に、それぞれ第３特大襞部４５３が配置されている。第３特大襞部４５３を設けることにより、絶縁有効長を長くすることなく、ポリマー套管１に要求される表面漏洩距離を確保しやすくなる。ここで、絶縁有効長とは、ポリマー套管１の襞部４２が形成されている部分の長手方向の長さを意味する。また、ポリマー套管１の先端側Ｓ１の高電位部の近傍に第３特大襞部４５３を配置した場合、高電位部からの放電の進展が抑制されるので、表面閃絡を防止するのに効果的である。 Moreover, the polymer cannula 1 has a third oversized fold 453 as the oversized fold 45 , which is arranged at a different position from the first oversized fold 451 and the second oversized fold 452 . The third extra-large folds 453 are arranged, for example, at the distal end side S1 from the first extra-large folds 451 with a predetermined spacing. In this embodiment, two third oversized folds 453 are arranged between the distal end of the polymer cannula 1 and the first oversized folds 451 . Specifically, the third oversized folds 453 are arranged on the front end side S1 and the rear end side S2 of the small diameter portion 21 of the polymer cannula 1, respectively. By providing the third extra-large fold portion 453, it becomes easier to secure the surface leakage distance required for the polymer sleeve 1 without lengthening the effective insulation length. Here, the effective insulation length means the length in the longitudinal direction of the portion of the polymer sleeve 1 where the folds 42 are formed. Further, when the third extra-large fold portion 453 is arranged near the high potential portion on the tip side S1 of the polymer sleeve 1, the development of the discharge from the high potential portion is suppressed, so that surface flashover can be prevented. Effective.

このように、ポリマー套管１は、中心に配置される棒状の内部導体１０と、内部導体１０の外周に一体的に形成される硬質の絶縁筒２０と、内部導体１０と同心状に絶縁筒２０に埋設される遮へい金具３０と、絶縁筒２０の外周を覆う胴部４１及び胴部４１の外周に長手方向に離間して形成される複数の傘状の襞部４２を有するポリマー被覆体４０と、酸化亜鉛層又は高誘電率層で構成され絶縁筒２０とポリマー被覆体４０との界面に沿って配置され後端部が遮へい金具３０に接続される電界緩和層５０と、を備える。複数の襞部４２は、小襞部４３と、小襞部４３よりも胴部４１から径方向への突出長が大きい大襞部４４と、大襞部４４よりも胴部４１から径方向への突出長が大きい特大襞部４５と、を有し、特大襞部４５は、ポリマー被覆体４０において電界緩和層５０の先端部５１に対応する位置Ｐ０を基準として、先端側Ｓ１に向かって１枚目から３枚目のいずれかの位置に配置される第１特大襞部４５１を含む。 In this manner, the polymer sleeve 1 includes a rod-shaped inner conductor 10 arranged in the center, a hard insulating tube 20 integrally formed on the outer periphery of the inner conductor 10, and an insulating tube concentrically with the inner conductor 10. 20, a body portion 41 covering the outer periphery of the insulating tube 20 and a plurality of umbrella-shaped folds 42 formed on the outer periphery of the body portion 41 with a gap in the longitudinal direction. and an electric field relaxation layer 50 composed of a zinc oxide layer or a high dielectric constant layer, arranged along the interface between the insulating cylinder 20 and the polymer coating 40 and having a rear end connected to the shielding metal fitting 30 . The plurality of folds 42 are composed of small folds 43, large folds 44 having a longer projection length in the radial direction from the body 41 than the small folds 43, and radially from the body 41 than the large folds 44. The extra-large folds 45 have a large projection length, and the extra-large folds 45 are 1 It includes a first extra-large fold 451 that is positioned anywhere from the first to third sheets.

第１特大襞部４５１のバリア効果により、ポリマー套管１の低電位部と高電位部との間で生じる気中放電の進展が抑制され、表面閃絡が生じにくくなるので、絶縁特性が向上する。ここで、絶縁特性とは、例えば、乾燥ＡＣ閃絡特性、注水ＡＣ閃絡特性及び人工汚損ＡＣ耐電圧特性である。また、第１特大襞部４５１を設けることにより、小襞部４３及び大襞部４４のみを配置した場合に比較して、容易に表面漏洩距離を長くすることができる。したがって、さらなる高電圧化を図ることができ、例えば、１１０ｋＶ以上の電圧階級にも対応することができる。また、従来のポリマー套管の設計を大幅に変更することなく、近年改定されたＪＥＣ－５２０２の規格に適合させることができる。 Due to the barrier effect of the first oversized folds 451, the development of aerial discharge generated between the low potential portion and the high potential portion of the polymer sleeve 1 is suppressed, and surface flashover is less likely to occur, thereby improving insulation characteristics. do. Here, the insulating properties are, for example, dry AC flash-over properties, water-filled AC flash-over properties, and artificial fouling AC withstand voltage properties. In addition, by providing the first extra-large folds 451, the surface leakage distance can be easily increased as compared with the case where only the small folds 43 and the large folds 44 are arranged. Therefore, it is possible to further increase the voltage, and for example, it is possible to cope with a voltage class of 110 kV or more. Also, the recently revised JEC-5202 standard can be met without significant changes to the design of conventional polymer sleeves.

また、ポリマー套管１において、第１特大襞部４５１は、電界緩和層５０の先端部５１に対応する位置Ｐ０を基準として、先端側Ｓ１に向かって１枚目の位置Ｐ１又は２枚目の位置Ｐ２に配置されるのがより好ましい。
これにより、第１特大襞部４５１によるバリア効果を確実に得ることができる。 In addition, in the polymer cannula 1, the first extra-large fold portion 451 is located at the first position P1 or the second position toward the tip side S1 with the position P0 corresponding to the tip portion 51 of the electric field relaxation layer 50 as a reference. More preferably, it is located at position P2.
As a result, the barrier effect of the first oversized folds 451 can be reliably obtained.

また、ポリマー套管１において、特大襞部４５は、さらに、遮へい金具３０の近傍に配置される第２特大襞部４５２を含む。
これにより、ポリマー套管１における後端側Ｓ２の低電位部で生じた放電が、電界緩和層５０の先端部５１の近傍で生じる放電と繋がりにくくなるので、さらに絶縁性能が向上する。 Also, in the polymer sleeve 1 , the oversized fold 45 further includes a second oversized fold 452 located near the shield 30 .
As a result, the discharge generated at the low potential portion on the rear end side S2 of the polymer sleeve 1 is less likely to be connected to the discharge generated near the tip portion 51 of the electric field relaxation layer 50, thereby further improving the insulation performance.

また、ポリマー套管１において、特大襞部４５は、さらに、第１特大襞部４５１及び第２特大襞部４５２とは異なる位置に配置される第３特大襞部４５３を含む。
これにより、特大襞部４５の突出長を極端に大きくすることなく、要求される表面漏洩距離を確保することができる。 Also, in the polymer cannula 1 , the oversized fold 45 further comprises a third oversized fold 453 arranged at a different position than the first oversized fold 451 and the second oversized fold 452 .
As a result, the required surface leakage distance can be ensured without excessively increasing the projection length of the oversized folds 45 .

また、ポリマー套管１において、特大襞部４５は、隣り合う小襞部４３の間に配置されている。すなわち、ポリマー套管１の長手方向において、小襞部４３、特大襞部４５、小襞部４３の順に配置されている。
これにより、長手方向において、特大襞部４５と小襞部４３とが隣接し、降雨時又は注水時に、落下する水滴による橋絡が生じにくくなるので、注水ＡＣ閃絡特性がさらに向上する。 Also, in the polymer cannula 1 , the oversized folds 45 are arranged between adjacent small folds 43 . That is, in the longitudinal direction of the polymer cannula 1, the small folds 43, the extra-large folds 45, and the small folds 43 are arranged in this order.
As a result, the extra-large folds 45 and the small folds 43 are adjacent to each other in the longitudinal direction, and bridging due to falling water droplets is less likely to occur during rainfall or water injection, thereby further improving water injection AC flashover characteristics.

また、ポリマー套管１及び後述するポリマー套管３は、完全乾式の固体絶縁構造である。すなわち、従来の磁器套管のように套管本体の内部に絶縁油あるいはＳＦ_６ガスなどを使用しない環境に配慮した技術である。また、磁器套管に比較して耐震性に優れ災害に強い。よって、持続可能な開発目標（ＳＤＧｓ）の目標９「強靭（レジリエント）なインフラ構築、包摂的かつ持続可能な産業化の促進及びイノベーションの推進を図る」及び目標１１「包摂的で安全かつ強靭（レジリエント）で持続可能な都市及び人間居住を実現する」に貢献することが可能となる。ここで、持続可能な開発目標（ＳＤＧｓ）は、２０１５年９月の国連サミットで採択された「持続可能な開発のための２０３０アジェンダ」にて記載された、２０３０年までに持続可能でよりよい世界を目指す国際目標である。 Further, the polymer sleeve 1 and the polymer sleeve 3, which will be described later, are completely dry solid insulating structures. In other words, it is an environmentally friendly technology that does not use insulating oil or _SF6 gas inside the main body of the cannula unlike the conventional porcelain cannula. In addition, compared to porcelain sleeves, they are more earthquake-resistant and more resistant to disasters. Therefore, the Sustainable Development Goals (SDGs) 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation" and 11 "Inclusive, safe and resilient." It will be possible to contribute to the realization of resilient and sustainable cities and human settlements. Here, the Sustainable Development Goals (SDGs) are sustainable and better It is an international goal aimed at the world.

以上、本発明者によってなされた発明を実施の形態に基づいて具体的に説明したが、本発明は上記実施の形態に限定されるものではなく、その要旨を逸脱しない範囲で変更可能である。 Although the invention made by the inventor of the present invention has been specifically described above based on the embodiments, the present invention is not limited to the above embodiments, and can be changed without departing from the scope of the invention.

例えば、実施の形態では、本発明のポリマー套管を機器用ブッシングに適用した場合について説明したが、本発明のポリマー套管は、壁貫通ブッシング（特許文献２参照）や、絶縁筒２０の後端側Ｓ２にケーブル端末が装着されるケーブル終端接続部（図３参照）に適用することもできる。ここで、ケーブル端末は、電力ケーブル６１の他、ストレスコーン６２及び圧縮装置６３等の接続部品を含む。 For example, in the embodiments, a case where the polymer sleeve of the present invention is applied to a bushing for equipment has been described, but the polymer sleeve of the present invention can be applied to a wall-penetrating bushing (see Patent Document 2) or a rear insulating tube 20. It can also be applied to a cable terminal connector (see FIG. 3) in which a cable terminal is attached to the end side S2. Here, the cable terminal includes connection parts such as the stress cone 62 and the compression device 63 in addition to the power cable 61 .

図３は、本発明をケーブル終端接続部に適用したポリマー套管３の全体構成を示す部分断面図である。すなわち、図３に示すポリマー套管３は、いわゆる気中終端接続部である。図３に示すポリマー套管３における気中側の構造、すなわちポリマー被覆体４０を有する部分の構造は、実施の形態のポリマー套管１における気中側の構造、すなわちポリマー被覆体４０を有する部分の構造と同じであるため、詳細な説明を省略する。また、ケーブル終端接続部としては、ストレスコーン６２を絶縁筒２０内に収容するいわゆるインナーコーンタイプ（図３参照）と、ＲＢＪ（Rubber Block Joint;ゴムブロックジョイント）の絶縁方式のようにゴムブロックで絶縁ユニットの外周を覆うことによりポリマー套管とケーブル端末とを接続するいわゆるアウターコーンタイプ（図示略）とがあるが、本発明はいずれにも適用できる。 FIG. 3 is a partial cross-sectional view showing the overall construction of a polymer cannula 3 to which the present invention is applied to a cable terminating portion. That is, the polymer cannula 3 shown in FIG. 3 is a so-called aerial termination. The structure of the air side of the polymer cannula 3 shown in FIG. , detailed description is omitted. In addition, as the cable termination connection part, there is a so-called inner cone type (see FIG. 3) in which the stress cone 62 is accommodated in the insulating cylinder 20, and a rubber block like an RBJ (Rubber Block Joint) insulation method. There is a so-called outer cone type (not shown) in which a polymer tube and a cable end are connected by covering the outer circumference of an insulating unit, but the present invention can be applied to any of them.

また例えば、実施の形態では、特大襞部４５を４枚設けた場合について説明したが、特大襞部４５の数はこれに限定されず、例えば、ポリマー套管１に要求される表面漏洩距離に応じて設定されればよい。ただし、特大襞部４５の数を増やし過ぎると、長手方向における特大襞部４５同士の間隔が近くなり、閃絡しやすくなる。具体的には、特大襞部４５同士の間隔が近くなった場合には、特大襞部４５の先端同士の距離が近くなり、雨水が先端を伝いやすくなるため、閃絡が起こりやすくなる。このため、実施の形態のように、長手方向にわたって、小襞部４３と大襞部４４が交互に形成されるポリマー套管１において、長手方向における特定部位において大襞部４４に代えて特大襞部４５を形成する方が望ましい。 Further, for example, in the embodiment, a case where four oversized folds 45 are provided has been described, but the number of oversized folds 45 is not limited to this. It may be set accordingly. However, if the number of oversized pleats 45 is increased too much, the distance between the oversized pleats 45 in the longitudinal direction becomes close, and flashover is likely to occur. Specifically, when the distance between the oversized folds 45 is shortened, the distance between the tips of the oversize folds 45 is shortened, and rainwater tends to run along the tips, so flashover is likely to occur. Therefore, as in the embodiment, in the polymer cannula 1 in which the small folds 43 and the large folds 44 are alternately formed along the longitudinal direction, the oversized folds are formed instead of the large folds 44 at specific locations in the longitudinal direction. It is preferable to form the portion 45 .

今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

１、３ポリマー套管
１０内部導体
２０絶縁筒
２１小径部
２２テーパー部
２３大径部
３０遮へい金具
３１円筒部
３２フランジ部
４０ポリマー被覆体
４１胴部
４２襞部
４３小襞部
４４大襞部
４５特大襞部
４５１第１特大襞部
４５２第２特大襞部
４５３第３特大襞部
５０電界緩和層
６１電力ケーブル
６２ストレスコーン
６３圧縮装置
Ｃケース
Ｈヘッド部
Ｐ０ポリマー套管の電界緩和層の先端部に対応する位置
Ｐ１ポリマー套管の１枚目の襞部の位置
Ｐ２ポリマー套管の２枚目の襞部の位置
Ｓ１ポリマー套管の先端側
Ｓ２ポリマー套管の後端側 Reference Signs List 1, 3 polymer cannula 10 inner conductor 20 insulating tube 21 small diameter portion 22 tapered portion 23 large diameter portion 30 shielding fitting 31 cylindrical portion 32 flange portion 40 polymer coating 41 trunk portion 42 fold portion 43 small fold portion 44 large fold portion 45 Extra-large fold 451 First extra-large fold 452 Second extra-large fold 453 Third extra-large fold 50 Electric field relaxation layer 61 Power cable 62 Stress cone 63 Compressor C Case H Head P0 Tip of electric field relaxation layer of polymer sleeve P1 position of the first fold of the polymer cannula P2 position of the second fold of the polymer cannula S1 distal side of the polymer cannula S2 rear end side of the polymer cannula

Claims

中心に配置される棒状の内部導体と、
前記内部導体の外周に一体的に形成される硬質の絶縁筒と、
前記内部導体と同心状に前記絶縁筒に埋設される遮へい金具と、
前記絶縁筒の外周を覆う胴部と、前記胴部の外周に長手方向に離間して形成される複数の傘状の襞部と、を有するポリマー被覆体と、
酸化亜鉛層又は高誘電率層で構成され、前記絶縁筒と前記ポリマー被覆体との界面に沿って配置され、後端部が前記遮へい金具に接続される電界緩和層と、を備え、
複数の前記襞部は、小襞部と、前記小襞部よりも前記胴部から径方向への突出長が大きい大襞部と、前記大襞部よりも前記胴部から径方向への突出長が大きい特大襞部と、を有し、
前記特大襞部は、前記ポリマー被覆体において前記電界緩和層の先端部に対応する位置を基準として、先端側に向かって１枚目から３枚目のいずれかの位置に配置される第１特大襞部を含む、
ポリマー套管。 a rod-shaped inner conductor arranged at the center;
a hard insulating cylinder integrally formed around the outer periphery of the internal conductor;
a shielding fitting embedded in the insulating cylinder concentrically with the inner conductor;
a polymer covering having a body covering the outer periphery of the insulating tube, and a plurality of umbrella-shaped folds formed on the outer periphery of the body at intervals in the longitudinal direction;
an electric field relaxation layer composed of a zinc oxide layer or a high dielectric constant layer, arranged along the interface between the insulating cylinder and the polymer coating, and having a rear end connected to the shielding metal fitting,
The plurality of folds includes a small fold, a large fold having a longer radial projection length from the body than the small folds, and a radial projection from the body greater than the large folds. and an oversized fold having a large length;
The extra-large folds are the first extra-large folds arranged at any position from the first sheet to the third sheet toward the tip side with reference to the position corresponding to the tip part of the electric field relaxation layer in the polymer covering. including folds,
Polymer cannula.

前記第１特大襞部は、前記電界緩和層の前記先端部に対応する位置を基準として、先端側に向かって１枚目又は２枚目のいずれかの位置に配置される、
請求項１に記載のポリマー套管。 The first extra-large fold portion is arranged at either the first or second position toward the tip side, with the position corresponding to the tip portion of the electric field relaxation layer as a reference,
2. The polymeric cannula of claim 1.

前記特大襞部は、隣り合う前記小襞部の間に配置される、
請求項１又は２に記載のポリマー套管。 the oversized folds are positioned between adjacent small folds;
3. A polymeric cannula according to claim 1 or 2.

前記特大襞部は、さらに、前記遮へい金具の先端部より後端側に配置される第２特大襞部を含む、
請求項１から３のいずれか一項に記載のポリマー套管。 The extra-large folds further include a second extra-large fold arranged on the rear end side of the front end of the shielding metal fitting,
4. The polymeric cannula according to any one of claims 1-3.

前記特大襞部は、さらに、前記第１特大襞部及び前記第２特大襞部とは異なる位置に配置される第３特大襞部を含む、
請求項４に記載のポリマー套管。 The oversized folds further include a third oversized fold positioned at a different position than the first oversized fold and the second oversized fold.
5. The polymeric cannula of claim 4.

前記絶縁筒は、直胴状に形成された小径部と、前記小径部から後端側に向けて緩やかに拡径するテーパー部と、前記テーパー部の後端側に直胴状に形成された大径部と、を有し、
前記電界緩和層の前記先端部は、前記大径部に位置し、
前記第１特大襞部及び前記第２特大襞部は前記大径部に配置され、前記第３特大襞部は前記小径部に配置される、
請求項５に記載のポリマー套管。 The insulating cylinder includes a small diameter portion formed in a straight body shape, a tapered portion gradually expanding in diameter from the small diameter portion toward the rear end side, and a straight body shape formed in the rear end side of the tapered portion. having a large diameter portion;
the tip portion of the electric field relaxation layer is located in the large diameter portion,
The first oversized fold and the second oversized fold are located at the large diameter portion, and the third oversized fold is located at the small diameter portion,
6. The polymeric cannula of claim 5.