JP3657890B2

JP3657890B2 - Gas insulated switchgear

Info

Publication number: JP3657890B2
Application number: JP2001157200A
Authority: JP
Inventors: 哲雄吉田; 勝宮川; 信男正木
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2001-05-25
Filing date: 2001-05-25
Publication date: 2005-06-08
Anticipated expiration: 2020-06-08
Also published as: JP2002025372A

Description

【０００１】
【発明の属する技術範囲】
本発明は、スイッチギヤの一例であるガス絶縁開閉装置に関係する。
【０００２】
【従来の技術】
受配電設備であるスイッチギヤの一例として、ガス絶縁開閉装置の構成図を図６に示す。同図において、外周を金属で気密に囲まれた箱体１の内部は、図示左方の前面寄りに縦に設けられた隔壁２で前方の遮断器室１ａと後方の母線室１ｂに仕切られ、各室１ａ，１ｂには例えば六フッ化硫黄ガス（以下、絶縁ガスという）が封入されている。
【０００３】
このうち、遮断器室１ａの内部には遮断器３が収納され、隔壁２には図示していない貫通穴に絶縁スペーサ９が取付けられ、この前面には遮断器３が連結されている。
【０００４】
また母線室１ｂの天井部には、前側の端子部が接続導体８を介して上側の絶縁スペーサ９の後部に接続された断路器４Ａが取付けられ、この断路器４Ａの後部の端子部は、接続導体８を介して後方の碍子６に取付けられた母線５に接続されている。この母線５により隣接盤への接続が行われる。
【０００５】
一方、母線室１ｂの底部には、前側の端子部が接続導体８を介して下側の絶縁スペーサ９の後部に接続された断路器４Ａと略同形の断路器４Ｂが取付けられ、この断路器４Ｂの後部の端子部は、接続導体８を介して底部の後方に取付けられたケーブルヘッド７の上部端子へ接続されている。
【０００６】
さらに、図７に図６の絶縁スペーサ９の横断面図を示す。同図において、中心導体１０を例えばエポキシ樹脂より成る絶縁材料で一体で注形した絶縁層１１の略中央部は、隔壁２に取付けられたフランジ１２に固定されている。また、フランジ１２先端部の電界緩和のため、絶縁層１１側とは略Ｕ字形を横配置したＵ字溝１１ａがフランジ１２と対向して設けられ、さらに導電塗料等より成る接地層１３が施されている。なお、中心導体１０と周囲の絶縁ガスと接する絶縁層端部１１ｂは、例えば実開昭６４−３８７１７に示されているように、絶縁層１１ｂの角度θが約９０度になっている。これは、略中央部の絶縁層１１の絶縁厚さと中心導体１０導出部付近の絶縁厚さを略同様として絶縁層１１の貫通方向の絶縁耐力を均一にすると共に、沿面絶縁距離を伸ばすためである。
【０００７】
一方、絶縁層１１の比誘電率は、エポキシ樹脂の場合においては約５であり、また周囲の絶縁ガスの比誘電率は約１である。つまり、絶縁層の沿面では、比誘電率が異なることになる。
【０００８】
【発明が解決しようとする課題】
このように２つ以上の絶縁媒体が異なる比誘電率であると、この境界の等電位線が屈折し、電界強度が乱れることになる。つまり、絶縁層１１の沿面では電界強度が乱れることになる。この成分をみると、絶縁層１１の角度θが約９０度であるため、中心導体１０近傍の沿面では殆どが接線方向となり、法線方向は小さい。
【０００９】
一般に破壊電圧は電界強度に大きく左右され、その成分として法線方向が破壊電界になり、接線方向は沿面を進展する維持電界となる。このため、破壊電界が小さく破壊電圧が上昇することが考えられるが、接線方向の電界強度が大きいと沿面のストリーマが容易に伸び易い。さらに、沿面にはゴミ等が付着しやすいのでストリーマは更に伸び易くなり、そのため沿面の電界強度を更に乱して結果的に破壊電圧を下げることになる。
【００１０】
なお、絶縁層１１の沿面が十分に長い場合には電界強度の絶対値が許容値に対し低いため、接線方向の成分が多くても破壊電圧を下げることがない。しかし、沿面距離を短くして小形化を図る場合には、沿面の電界強度は許容値を超えることはないが近づくことになる。従って、沿面には容易にゴミ等が付着し、完全に清浄な表面状態を保つことができないので、接線方向の電界強度が大きいと沿面のストリーマが伸び易くなり、破壊電圧を低下させることになる。このため、沿面距離を比較的大きくすることにより、沿面の進展電界強度を許容値に対してある一定の割合以上に抑制しているので、縮小化は困難であった。この様に、一つの収納機器の絶縁距離が大形化すると他の収納機器にも波及し、結果的に装置の全体形状が大形化してしまう。
【００１１】
本発明の目的は、破壊電圧を向上させたモールドブッシングを具備するガス絶縁開閉装置を提供することにある。
【００１２】
【課題を解決するための手段】
上記目的を達成するために第１の発明は、中心導体を絶縁物で注形し、中心導体と接する絶縁層端部と中心導体の軸とのなす角度を５０度以下とし、中心導体が導出される絶縁層端部の沿面における法線方向の電界強度と接線方向の電界強度とが平衡するようにしたモールドブッシングを具備し、絶縁層の周囲には絶縁ガスがあるガス絶縁開閉装置である。
【００１３】
また第２の発明では、第１の発明のガス絶縁開閉装置において、絶縁層の比誘電率を５、周囲の絶縁ガスの比誘電率を１とし、絶縁ガスは、六フッ化硫黄ガス、Ｎ ₂ ガス、空気のいずれかであることを特徴とするガス絶縁開閉装置である。
【００１５】
これらの構成において、中心導体と接する絶縁層端部と中心導体の軸とのなす角度を５０度以下とし、中心導体が導出される絶縁層端部の沿面における法線方向の電界強度と接線方向の電界強度とが平衡するようにしたので、破壊電圧を向上させることができる。
【００１６】
すなわち、中心導体に対し絶縁層の角度が９０度であれば、等電位線がほぼ直角に交差するので絶縁層沿面では接線方向の成分が大きくなる。逆に絶縁層の角度がほぼ０度であれば、法線方向の成分が大きくなる。この角度を全角において電界強度の成分をみると、ある角度において互いの成分が交わる点が生じる。この点においては、電界強度の絶対値が抑えられると共に、互いの成分が最小値になる点であり、破壊電圧の向上が図れる。
【００１７】
【発明の実施の形態】
以下、本発明の一実施例を図面を用いて説明する。
【００１８】
図１は、図６における絶縁スペーサ９の横断面図である。中心導体１０の周囲にはエポキシ樹脂等より成る絶縁材料が注形された絶縁層１４が形成され、絶縁層１４の略中央部はフランジ１２に固定されている。また、接地側の絶縁層１４にはＵ字溝１４ａがフランジ１２に対向して設けられ、Ｕ字溝１４ａには導電塗料より成る接地層１３が施こされ接地側の電界緩和がされていることは従来と同様である。ここで、中心導体１０と接する絶縁層端部１４ｂの角度θは５０度以下としている。なお、絶縁層１４の比誘電率は約５であり、周囲の絶縁ガスは比誘電率１である。
【００１９】
このような構成における絶縁層１４の沿面の電界強度分布を図２、図３に示す。図２は絶縁層１４の角度を変化させたときの電界強度の特性図であり、図３は電界強度の成分を説明するための電界強度のベクトル図である。図３では、電界強度の絶対値Ｅ_Ｏに対し、法線方向の電界強度をＥ_H、接線方向の電界強度をＥ_Sとしている。また、θは中心導体１０と接する絶縁層１４の角度である。
【００２０】
これらの図において、絶縁層１４の角度により電界強度が変化することがわかる。すなわち、角度θが大きくなると絶対値Ｅ₀が略５０度以上より急激に上昇し、これに伴いＥ_Sも同様に上昇する。逆に、Ｅ_Hは角度θが大きくなると小さくなり、Ｅ_SとＥ_Hは角度θが５０度で交差する。また、θが５０度以上ではＥ_S＞Ｅ_Hとなり、θ＝５０度以下ではＥ_S＜Ｅ_Hとなる。
【００２１】
これにより、沿面の放電進展電界であるＥ_Sを抑えるには、角度θを５０度以下にする必要があり、この場合、破壊電圧はＥ_Hで左右されることになる。このため、沿面が若干のゴミや凹凸による表面状態でもストリーマが伸展することを防げ、沿面の電界強度を乱すことがなくなる。そして、破壊電圧は、Ｅ_Hで左右され、電界強度と破壊電圧を一致させることができる。ここで、逆に角度θを５０度以上にすると、Ｅ_Hは下がって見かけ上破壊電圧が上昇するように思われるが、沿面では放電が進展して電界強度を乱し、結果的に破壊電圧が低下することになる。
【００２２】
これらのことにより、角度θ＝５０度以下においては沿面の放電の進展が防げるので、許容電界強度付近まで電界強度を上昇させることができる。つまり、絶縁耐力を良好に維持できるので、沿面の絶縁距離を短くでき、絶縁スペーサ９の小形化が図れる。なお、中心導体１０の直径と接地層１３の外径および電界緩和のＵ字溝１４ｂの最適形状を求めれば、沿面の電界強度を中心導体１０から接地層１３まで略同等値にできて大幅な縮小化が図れるが、一般的には、中心導体１０の電界強度が接地層１３より高くなるので、高電圧側の電界強度の成分の平衡を図れば効果的な縮小化が図れる。
【００２３】
次に、接地側に二次巻線を装着した貫通形ブッシングを図４に示すが、中心導体１５と二次巻線１６を一体で注形する絶縁層１７において、中心導体１５が導出する絶縁層１７ａの角度を５０度以下にすることにより、沿面の電界強度の法線方向の成分と接線方向の成分の電界強度を抑制する。なお、１８は接触子であり、また、１９は他の機器へ接続する接続導体である。このようなブッシングにおいては、埋込み金属が大きいので絶縁層１７はゴム状等のやわらかい材料を用いることがある。この場合、比誘電率は例えばシリコーンゴムで２〜３であるが、絶縁層１７と周囲の絶縁媒体の比誘電率が異なっているので、沿面では等電位線が屈折して電界強度が乱れる。このような低い方の比誘電率の沿面では、電界強度の成分の平衡を図ることにより、沿面の放電進展を防ぐことができる。また、接地側に二次巻線１６があり、中心導体１５との電界強度分布が一般のモールドブッシングと異なる場合においても、沿面のうちの電界強度の高い高電圧側の電界強度を抑制して成分を平衡させれば、絶縁耐力の向上が図れる。
【００２４】
図５は、計器用変成器の場合である。一次巻線２０と二次巻線２１、および一次巻線２０を導出する主回路リード線２２を一括して注形し、絶縁層２３を形成する場合においても、主回路リード線２２の口出し部の絶縁層端部２３ａの角度を５０度以下にすることにより、沿面の電界強度を抑制することができる。主回路リード線２２は、一般的に通電容量が少ないことにより、より線を用いた被覆電線であり、被覆２４が設けられているが、この様な被合絶縁構造においても絶縁層端部２３ａの電界強度の成分を平衡させ抑制することができる。絶縁ガスの比誘電率約１に比べて絶縁層２３および被覆２４の比誘電率が大きく、絶縁層２３の沿面での等電位線の屈折が大きくなって電界強度を乱すが、各絶縁媒体の絶縁耐力は絶縁耐力は絶縁層２３や被覆２４が数１０kV/mmと高いのに比べて、絶縁ガスでは大気圧のガス圧力で８．９kV/mmと低いため、沿面の絶縁破壊が絶縁ガスで決まり、この絶縁層端部２３ａの電界強度で破壊電圧が左右される。なお、２５は、二次巻線より電圧を検出する二次端子である。
【００２５】
他の実施例として、空気やＮ₂ガスなどを用いた絶縁媒体中においても、絶縁物に対して比誘電率が小さく、また絶縁耐力が小さいので、主回路導体の口出し部にあたる絶縁物の角度を５０度以下にすれば、法線方向と接線方向の電界強度を抑制して破壊電圧の向上が図れ、効果的に縮小化を図ることができる。
【００２６】
【発明の効果】
以上のように第１の発明、第２の発明によれば、中心導体と接する絶縁層端部と中心導体の軸とのなす角度を５０度以下とし、中心導体が導出される絶縁層端部の沿面における法線方向の電界強度と接線方向の電界強度とが平衡する。
【００２７】
これにより、法線方向と接線方向の電界強度が平衡され、電界強度を抑制して破壊電圧の向上が図れ、効果的に縮小化を図ることができる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す絶縁スペーサの横断面図。
【図２】 [図１]の特性を説明するための図。
【図３】 [図１]の特性を説明するための図。
【図４】本発明の他の実施例を示す貫通形ブッシングの要部拡大断面図。
【図５】本発明の他の実施例を示す計器用変成器の縦断面図。
【図６】代表的なスイッチギヤの側面図。
【図７】 [図６]の絶縁スペーサ９の横断面図。
【符号の説明】
１…絶縁スペーサ
１０…中心導体
１４…絶縁層[0001]
[Technical scope to which the invention belongs]
The present invention relates to a gas insulated switchgear as an example of a switchgear.
[0002]
[Prior art]
FIG. 6 shows a configuration diagram of a gas-insulated switchgear as an example of a switchgear that is a power distribution facility. In this figure, the inside of the box 1 whose outer periphery is hermetically surrounded by metal is partitioned into a front breaker chamber 1a and a rear busbar chamber 1b by a partition wall 2 provided vertically near the front side on the left side of the figure. Each chamber 1a, 1b is filled with, for example, sulfur hexafluoride gas (hereinafter referred to as insulating gas).
[0003]
Among these, the circuit breaker 3 is accommodated in the circuit breaker chamber 1a, the insulating spacer 9 is attached to the partition wall 2 in a through hole (not shown), and the circuit breaker 3 is connected to the front surface.
[0004]
Further, a disconnector 4A in which a front terminal portion is connected to a rear portion of the upper insulating spacer 9 via a connection conductor 8 is attached to the ceiling portion of the bus bar 1b. A terminal portion of the rear portion of the disconnector 4A is It is connected to a bus bar 5 attached to a rear insulator 6 through a connecting conductor 8. This bus 5 connects to the adjacent board.
[0005]
On the other hand, a disconnector 4B having substantially the same shape as the disconnector 4A in which the front terminal portion is connected to the rear portion of the lower insulating spacer 9 via the connecting conductor 8 is attached to the bottom of the bus bar chamber 1b. The terminal portion at the rear of 4B is connected to the upper terminal of the cable head 7 attached to the rear of the bottom via a connection conductor 8.
[0006]
FIG. 7 is a cross-sectional view of the insulating spacer 9 of FIG. In the figure, a substantially central portion of an insulating layer 11 in which a central conductor 10 is integrally cast with an insulating material made of, for example, an epoxy resin is fixed to a flange 12 attached to a partition wall 2. Further, in order to alleviate the electric field at the front end of the flange 12, a U-shaped groove 11a having a substantially U-shape arranged laterally from the insulating layer 11 side is provided facing the flange 12, and a grounding layer 13 made of conductive paint or the like is further applied. Has been. Note that the insulating layer end 11b in contact with the central conductor 10 and the surrounding insulating gas has an insulating layer 11b angle θ of about 90 degrees as shown in, for example, Japanese Utility Model Laid-Open No. 64-38717. This is because the insulating thickness of the insulating layer 11 in the substantially central portion and the insulating thickness in the vicinity of the lead-out portion of the central conductor 10 are substantially the same so that the insulation strength in the penetration direction of the insulating layer 11 is uniform and the creeping insulation distance is extended. is there.
[0007]
On the other hand, the dielectric constant of the insulating layer 11 is about 5 in the case of epoxy resin, and the relative dielectric constant of the surrounding insulating gas is about 1. That is, the relative permittivity varies along the creeping surface of the insulating layer.
[0008]
[Problems to be solved by the invention]
Thus, when two or more insulating media have different relative dielectric constants, the equipotential lines at the boundary are refracted, and the electric field strength is disturbed. That is, the electric field strength is disturbed along the creeping surface of the insulating layer 11. Looking at this component, since the angle θ of the insulating layer 11 is about 90 degrees, most of the creeping surface near the central conductor 10 is a tangential direction, and the normal direction is small.
[0009]
In general, the breakdown voltage greatly depends on the electric field strength, and as a component thereof, the normal direction is a breakdown electric field, and the tangential direction is a sustaining electric field that progresses along the creeping surface. For this reason, it is conceivable that the breakdown electric field is small and the breakdown voltage is increased. However, if the electric field strength in the tangential direction is large, the creeping streamer is easily extended. In addition, since the dust and the like are likely to adhere to the creepage, the streamer is more likely to extend, which further disturbs the electric field strength on the creepage and consequently lowers the breakdown voltage.
[0010]
When the creeping surface of the insulating layer 11 is sufficiently long, the absolute value of the electric field strength is lower than the allowable value, so that the breakdown voltage is not lowered even if there are many components in the tangential direction. However, when the creepage distance is shortened to reduce the size, the electric field strength on the creepage does not exceed the allowable value but approaches. Therefore, dust or the like easily adheres to the creepage surface, and a completely clean surface state cannot be maintained. Therefore, if the electric field strength in the tangential direction is large, the streamer along the creepage surface tends to extend and the breakdown voltage is reduced. . For this reason, since the creeping electric field intensity is suppressed to a certain ratio or more with respect to the allowable value by relatively increasing the creeping distance, it is difficult to reduce the creeping distance. Thus, when the insulation distance of one storage device increases, it spreads to other storage devices, and as a result, the overall shape of the device increases.
[0011]
An object of the present invention is to provide a gas insulated switchgear having a mold bushing with improved breakdown voltage.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the first invention, the center conductor is cast with an insulator, the angle formed between the end of the insulating layer in contact with the center conductor and the axis of the center conductor is 50 degrees or less, and the center conductor is derived. A gas-insulated switchgear comprising a mold bushing in which the electric field strength in the normal direction and the electric field strength in the tangential direction are balanced on the creeping surface of the insulating layer end portion, and an insulating gas is present around the insulating layer .
[0013]
According to the second invention, in the gas insulated switchgear according to the first invention, the dielectric constant of the insulating layer is 5, the relative dielectric constant of the surrounding insulating gas is 1, and the insulating gas is sulfur hexafluoride gas, N ₂ gas is a gas insulated switchgear, characterized in that either the air.
[0015]
In these configurations, the angle between the end of the insulating layer in contact with the center conductor and the axis of the center conductor is 50 degrees or less, and the electric field strength and tangential direction in the normal direction along the creeping surface of the end of the insulating layer from which the center conductor is derived since the electric field intensity so as to equilibrium, it is possible to improve the breakdown voltage.
[0016]
That is, if the angle of the insulating layer is 90 degrees with respect to the central conductor, the equipotential lines intersect almost at right angles, so that the tangential component increases along the insulating layer. Conversely, if the angle of the insulating layer is approximately 0 degrees, the component in the normal direction becomes large. When the components of the electric field intensity are observed at all angles, a point where the components intersect at a certain angle is generated. In this respect, the absolute value of the electric field strength is suppressed and the mutual components are minimum values, so that the breakdown voltage can be improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a cross-sectional view of the insulating spacer 9 in FIG. An insulating layer 14 in which an insulating material made of epoxy resin or the like is cast is formed around the center conductor 10, and a substantially central portion of the insulating layer 14 is fixed to the flange 12. Further, a U-shaped groove 14a is provided in the ground-side insulating layer 14 so as to face the flange 12, and a ground layer 13 made of a conductive paint is applied to the U-shaped groove 14a to reduce the electric field on the ground side. This is the same as before. Here, the angle θ of the insulating layer end 14b in contact with the center conductor 10 is set to 50 degrees or less. The dielectric layer 14 has a relative dielectric constant of about 5, and the surrounding insulating gas has a relative dielectric constant of 1.
[0019]
The electric field strength distribution along the creeping surface of the insulating layer 14 in such a configuration is shown in FIGS. FIG. 2 is a characteristic diagram of the electric field strength when the angle of the insulating layer 14 is changed, and FIG. 3 is a vector diagram of the electric field strength for explaining the component of the electric field strength. In FIG. 3, the electric field strength in the normal direction is E _H and the electric field strength in the tangential direction is E _S with respect to the absolute value E _O of the electric field strength. Θ is the angle of the insulating layer 14 in contact with the central conductor 10.
[0020]
In these figures, it can be seen that the electric field strength varies depending on the angle of the insulating layer 14. That is, as the angle θ increases, the absolute value E ₀ rises more rapidly than about 50 degrees or more, and accordingly, E _S also rises. Conversely, E _H decreases as the angle θ increases, and E _S and E _H intersect at an angle θ of 50 degrees. When θ is 50 degrees or more, E _S > E _H is satisfied, and when θ = 50 degrees or less, E _S <E _H is satisfied.
[0021]
Thus, in order to suppress the E _S is a discharge progress field of creeping, it is necessary to angle θ below 50 degrees, in this case, the breakdown voltage will be left in E _H. For this reason, the streamer can be prevented from extending even if the creeping surface is a surface state caused by some dust or unevenness, and the electric field strength on the creeping surface is not disturbed. The breakdown voltage depends on E _H , and the electric field strength can be matched with the breakdown voltage. Here, conversely, when the angle θ is set to 50 degrees or more, it seems that E _H is lowered and the breakdown voltage is apparently increased. However, along the creepage, the electric discharge is developed and the electric field strength is disturbed, resulting in the breakdown voltage. Will drop.
[0022]
As a result, the progress of creeping discharge can be prevented at an angle θ = 50 degrees or less, and the electric field strength can be increased to the vicinity of the allowable electric field strength. That is, since the dielectric strength can be maintained well, the creeping insulation distance can be shortened, and the insulating spacer 9 can be miniaturized. If the optimum diameter of the central conductor 10, the outer diameter of the ground layer 13, and the U-shaped groove 14 b for electric field relaxation is obtained, the electric field strength along the creepage can be made substantially equal from the central conductor 10 to the ground layer 13. In general, the electric field strength of the center conductor 10 is higher than that of the ground layer 13, so that effective reduction can be achieved by balancing the components of the electric field strength on the high voltage side.
[0023]
Next, a through-type bushing in which a secondary winding is mounted on the ground side is shown in FIG. 4, but in an insulating layer 17 in which the center conductor 15 and the secondary winding 16 are cast integrally, the insulation derived from the center conductor 15 is shown. By setting the angle of the layer 17a to 50 degrees or less, the electric field strengths of the normal direction component and the tangential direction component of the creeping electric field strength are suppressed . In addition, 18 is a contact, and 19 is a connection conductor for connecting to other devices. In such a bushing, since the embedded metal is large, the insulating layer 17 may be made of a soft material such as rubber. In this case, the relative dielectric constant is, for example, 2 to 3 for silicone rubber. However, since the relative dielectric constants of the insulating layer 17 and the surrounding insulating medium are different, equipotential lines are refracted along the creepage surface, and the electric field strength is disturbed. In such creepage with a lower relative dielectric constant, the progress of creeping discharge can be prevented by balancing the electric field strength components. Further, even when the secondary winding 16 is on the ground side and the electric field strength distribution with the central conductor 15 is different from that of a general mold bushing, the electric field strength on the high voltage side where the electric field strength is high on the creeping surface is suppressed. If the components are balanced, the dielectric strength can be improved.
[0024]
FIG. 5 shows a case of an instrument transformer. Even when the primary winding 20, the secondary winding 21, and the main circuit lead wire 22 that leads out the primary winding 20 are cast together to form the insulating layer 23, the lead portion of the main circuit lead wire 22 is formed. By setting the angle of the insulating layer end 23a to 50 degrees or less, the electric field strength on the creeping surface can be suppressed. The main circuit lead wire 22 is generally a covered electric wire using a stranded wire due to a small current carrying capacity, and is provided with a covering 24. In such a to-be-insulated structure, the insulating layer end portion 23a is also provided. The components of the electric field strength can be balanced and suppressed. The relative dielectric constant of the insulating layer 23 and the coating 24 is larger than the relative dielectric constant of the insulating gas 1, and the refraction of equipotential lines along the creeping surface of the insulating layer 23 increases to disturb the electric field strength. Dielectric strength is as low as 8.9 kV / mm at the gas pressure of atmospheric pressure compared to the insulation layer 23 and the coating 24 being as high as several tens of kV / mm. The breakdown voltage depends on the electric field strength of the insulating layer end 23a. Reference numeral 25 denotes a secondary terminal for detecting a voltage from the secondary winding.
[0025]
As another example, even in an insulating medium using air, N ₂ gas, or the like, the relative dielectric constant is small relative to the insulator and the dielectric strength is small, so the angle of the insulator corresponding to the lead portion of the main circuit conductor If the angle is 50 degrees or less, the electric field strength in the normal direction and the tangential direction can be suppressed, the breakdown voltage can be improved, and the reduction can be effectively achieved.
[0026]
【The invention's effect】
As described above, according to the first and second inventions, the angle between the end of the insulating layer in contact with the center conductor and the axis of the center conductor is 50 degrees or less, and the end of the insulating layer from which the center conductor is derived The electric field strength in the normal direction and the electric field strength in the tangential direction at the creeping surface are balanced.
[0027]
Thereby, the electric field strengths in the normal direction and the tangential direction are balanced, the electric field strength is suppressed, the breakdown voltage can be improved, and the reduction can be effectively achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an insulating spacer showing one embodiment of the present invention.
FIG. 2 is a diagram for explaining the characteristics of FIG. 1;
FIG. 3 is a diagram for explaining the characteristics of FIG. 1;
FIG. 4 is an enlarged cross-sectional view of a main part of a through-type bushing showing another embodiment of the present invention.
FIG. 5 is a longitudinal sectional view of an instrument transformer showing another embodiment of the present invention.
FIG. 6 is a side view of a typical switch gear.
FIG. 7 is a cross-sectional view of the insulating spacer 9 of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Insulating spacer 10 ... Center conductor 14 ... Insulating layer

Claims

The center conductor is cast with an insulator, the angle formed between the end of the insulating layer in contact with the center conductor and the axis of the center conductor is 50 degrees or less, and the creeping surface of the end of the insulating layer from which the center conductor is derived It has a mold bushing that balances the electric field strength in the normal direction and the electric field strength in the tangential direction,
A gas insulated switchgear comprising an insulating gas around the insulating layer .

The gas insulated switchgear according to claim 1,
The insulating layer has a relative dielectric constant of 5, a surrounding dielectric gas has a relative dielectric constant of 1, and the insulating gas is sulfur hexafluoride gas, N ₂ gas, or air. Insulated switchgear.