JP2003007394A - Method, structure and connector for connecting high voltage cable, and coaxial transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance dielectric strength and compactly connect a high voltage cable. SOLUTION: A high voltage cable connecting connector 6 is provided with an insulated connector 7 for connecting two opposite high voltage cables 1, 1 respectively having at least a conductor 2 and a solid insulator 3 for covering the conductor 2. A connecting part with the solid insulator 3 in the insulated connection 7 is provided with a reverse electric field part 4 that the travelling direction of discharge is the direction having a vector component reverse to the direction of the electric field.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high voltage cable,
The present invention relates to electrical insulation of a high voltage cable connector and a conductor such as a coaxial transmission line through which a high voltage flows. More specifically, the present invention relates to a technique for preventing creeping discharge and dielectric breakdown in a solid insulator covering a conductor.

[0002]

2. Description of the Related Art CV in which a conductor is covered with a solid insulator
When connecting high-voltage cables such as cables, generation of creeping (surface) discharge at the connection point of solid insulators is the greatest weak point in insulation. The direction of electric discharge that accompanies electrical breakdown depends on the direction of the electric field. This also applies to the creeping discharge that occurs along the surface of the solid insulator. Therefore, as a conventional measure for improving the dielectric strength of creeping discharge of a solid insulator, it is common to increase the creeping distance to improve the dielectric strength. For example, as shown in FIG. 6, the solid insulator 103 is shaved so that the conductor 102 is exposed so that the end of each cable 101 to be connected is sharpened.
The conductors 102, 102 are butt-joined to each other, and the conductors 102, 102 and the shaved solid insulator 103 are solidified by a mold 104 made of an insulator such as resin so that the cables 101, 101 are connected to each other. ing. Incidentally, on the connection surface 105, the high voltage side (conductor 10
The distance from 2) to the low voltage side (outside the solid insulator 104) is called the creepage distance L.

By the way, GIS (Gas Insulated Switch)
gear, gas insulated switchgear) and GIL (Gas Insulated tr)
In an ansmission line, a high voltage cable for air transmission in a pipeline), as shown in FIG. 7, the inner conductor 106, SF ₆ (sulfur hexafluoride gas) gas 107 having excellent electrical insulation and the outer conductor 108 are used. Structure of coaxial transmission line 109
Is used. The inner conductor 106 is coated with an insulating paint that prevents adhesion of impurities. Even in such a coaxial transmission line 109, the internal conductors 106 and 106 are connected to each other, but since the insulation property of SF ₆ is sufficiently high, there is no concern about creeping discharge such as the connection of the cable 101. Few.

[0004]

However, in the conventional method of connecting the cable 101, the dielectric strength has been improved by increasing the creepage distance L. However, as the creepage distance L is increased, the dielectric strength is increased. If the dielectric strength is not improved and the dielectric strength is increased, there is a problem that the momentum connection portion becomes large as a whole. On the contrary, when the size of the connecting portion is limited, improvement of the dielectric strength cannot be expected.

On the other hand, even in the coaxial transmission line 109 used in GIS or GIL, although SF ₆ has excellent electric insulation, there is a certain amount of space between the inner and outer conductors in order to ensure insulation. It is necessary, and there is a problem that the pipe diameter of the outer conductor is increased accordingly. The insulation breakdown of this coaxial transmission line is greatly affected by the insulation of SF ₆ . However, SF ₆ has been pointed out as a gas that contributes to global warming, and it is considered to use an alternative gas such as pure nitrogen. However, each of the alternative gases is inferior in insulation property to SF ₆ . Therefore, as a measure against a large decrease in dielectric strength due to the use of the alternative gas 110, a coaxial transmission line 109 'in which the inner conductor 106 is covered with a solid insulator 111 is considered as shown in FIG. However, in this case, the connection point 112 of the solid insulators 111 and 111 becomes a weak point, and there is a concern of creeping discharge and dielectric breakdown from the inner conductor 106 on the high voltage side to the outer conductor 108 on the low voltage side (Fig. 8 middle arrow A). Then, in order to increase the dielectric strength, it is necessary to increase the gap (space) filled with the alternative gas 110, and as a result, the entire coaxial transmission line 109 ′ becomes large. Conversely, the size of the coaxial transmission line 109 ′ is large. In the case where the thickness is limited, a problem similar to that of the CV cable arises in that the improvement of the dielectric strength cannot be expected.

Therefore, an object of the present invention is to provide a high-voltage cable connecting method and a connecting structure, a high-voltage cable connecting connector, and a coaxial transmission line which can improve the dielectric strength and can be connected in a compact manner.

[0007]

In order to achieve such an object, the invention according to claim 1 is such that a conductor is covered with a solid insulator to prevent a creeping discharge and a dielectric breakdown at a connection point of the solid insulator. In a method of connecting a high-voltage cable which may occur, a reverse electric field portion is provided on the connection surface of the solid insulator with another insulator so that the discharge progressing direction has a vector component opposite to the electric field direction. I have to.

Further, the invention according to claim 2 is a connection structure for a high-voltage cable, which comprises a conductor and a solid insulator surrounding the conductor, which may cause creeping discharge and dielectric breakdown at a connection point of the solid insulator. The reverse electric field portion is provided on the connection surface of the solid insulator with other insulators so that the discharge progressing direction is a direction having a vector component opposite to the electric field direction.

Therefore, the creeping discharge which proceeds along the surface where the solid insulators are connected to each other toward the direction of the electric field, that is, the outside of the solid insulators, penetrates the inside of the solid insulators to the outside of the solid insulators. Since it is easier to electrically move to the outside of the solid insulator along the reverse electric field portion than to appear, the reverse electric field portion provided at the connection portion has a vector component opposite to the electric field direction. Direction, that is, the direction opposite to the direction of the electric field. Therefore, the dielectric strength is improved. Moreover, the existence of the reverse electric field portion makes the total creepage distance longer than the creepage distance when the start point and the end point are connected by a straight line. This also improves the dielectric strength. Therefore, the dielectric strength can be increased without enlarging the connection portion.

According to a third aspect of the invention, in the high-voltage cable connection structure according to the second aspect, the reverse electric field portion is formed of a screw structure. in this case,
Since one slope of the screw thread functions as a reverse electric field portion and is repeatedly formed, the dielectric strength is further improved.
Moreover, the total creepage distance is much longer than the creepage distance when the start point and the end point are connected by a straight line. This also improves the dielectric strength.

According to another aspect of the present invention, there is provided a connector for connecting high voltage cables, wherein conductors are covered with a solid insulator to connect high voltage cables to each other. An insulating connecting portion for mechanically connecting and a conducting portion for electrically connecting a conductor are provided, and a connecting portion between the insulating connecting portion and the solid insulator has a discharge progress direction as an electric field direction. Is provided with a reverse electric field portion having a direction having a reverse vector component.

Also in this case, since the discharge progresses in the direction opposite to the electric field direction in the reverse electric field portion formed at the connection portion between the insulating connection portion of the connector and the solid insulator of the high voltage cable, the dielectric strength is increased. improves. Further, the reverse electric field portion also increases the total creepage distance as compared with the creepage distance when the start point and the end point are connected by a straight line, thereby improving the dielectric strength. Therefore, the dielectric strength can be increased without increasing the size of the connecting portion.

According to a fifth aspect of the present invention, in the high-voltage cable connecting connector according to the fourth aspect, the reverse electric field portion is constituted by a screw structure, and a screw for connecting one high-voltage cable and another The screw for connecting the high voltage cable is configured as a reverse screw.

In this case, the cable can be connected only by rotating the connector in one direction without rotating the high voltage cable itself, and can be disconnected by rotating the connector in the opposite direction.

According to a sixth aspect of the present invention, the coaxial transmission line includes an inner conductor, an outer conductor coaxially arranged with a space provided between the inner conductor, and an insulating gas filled in the space. In the above, the inner electric conductor is covered with a solid insulator, and a reverse electric field portion is provided at a connection portion between the solid insulators so that the discharge progressing direction is a direction having a vector component opposite to the electric field direction. .

In this case, the creeping discharge at the connection point, which is the weakest point in the insulation, is prevented by providing the reverse electric field portion and increasing the dielectric strength, so that the solid insulation between the inner conductor and the outer conductor is prevented. Dielectric strength is improved. Therefore, when SF ₆ is used as usual, the gap between the inner and outer conductors can be reduced.

Furthermore, in the coaxial transmission line according to the seventh aspect of the present invention, SF ₆ alternative gas is used as the insulating gas.

[0018] S in this case, the dielectric strength than SF ₆ inferior
Even when the F ₆ alternative gas is used, the solid insulator compensates for the lack of dielectric strength between the inner conductor and the outer conductor, and creeping discharge, which is a concern at the connection between the solid insulators, also causes the reverse electric field portion. Since it is prevented by the increase of the dielectric strength due to the provision, the same insulation property as that when SF ₆ is used can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described below in detail based on the embodiments shown in the drawings.

FIG. 1 shows an embodiment of a high-voltage cable connecting structure using a high-voltage cable connecting connector for realizing the high-voltage cable connecting method of the present invention. This high-voltage cable connecting connector (hereinafter simply referred to as “connector”) 6 mainly comprises an insulating connecting portion 7 for mechanically connecting the solid insulator 3 portion of the high-voltage cable 1 and an electrical connection of the conductor 2. It is composed of a contact point 11 for connection.

The insulative connection portion 7 constitutes the main body of the connector 6, and is made of a material having sufficient mechanical strength to connect the cables to each other and excellent electrical insulation, such as ceramics or the solid insulator 3. It is molded with an insulating material such as. In the case of the present embodiment, a sleeve for connecting the two high-voltage cables 1 in a straight line is provided, having at both ends mounting portions 8 of a screw structure for respectively fitting with the ends of the solid insulator 3 and mechanically connecting them. It is shaped like a nut. That is,
The insulating connecting portion 7 is formed into a cylindrical shape, and the mounting portions 8 and 8 formed of female threads are formed (hereinafter,
The mounting portion 8 is also called a female screw). Further, a male screw 5 that meshes with the female screw 8 is also provided at the end of the solid insulator 3 of the high-voltage cable 1 to be connected. here,
The female threads 8 on both ends are preferably reverse threads. In this case, the screws 5 and 8 can be tightened or loosened, that is, the cables 1 can be connected or disconnected by simply rotating the connector 6 without rotating the cable 1. Moreover, it is preferable that the insulating connection portion 7 is formed in a cylindrical shape having an outer diameter substantially the same as the outer diameter of the solid insulator 3. In this case, there is no step between the connector 6 and the cable 1 to be connected, and they can be connected in a straight line. Furthermore, in the present embodiment, the case where the mounting portion 8 having a screw structure is used is mainly described, but the present invention is not particularly limited to this, and any connecting means that can engage in the axial direction may be used as necessary. It goes without saying that it can be applied.

A reverse electric field portion 4 is provided at the connection portion of the insulating connection portion 7 with the solid insulator 3 so that the discharge progressing direction is a direction having a vector component opposite to the electric field direction. In order to make the progressing direction of the discharge have a vector component opposite to the electric field direction, for example, the insulating connecting portion 7
The connection surface between the solid insulator 3 and the solid insulator 3 may be formed so as to be folded back toward the conductor 2 at least once. In other words, the connecting surface between the insulative connecting portion 7 and the solid insulator 3 may be formed so as to draw alternate bent lines in the vertical cross section. As a result, the reverse electric field portion 4 is provided in the discharge path from the conductor 2 to the outside of the solid insulator 3 so that the discharge progress direction is a direction having a vector component opposite to the electric field direction. The "direction having a vector component opposite to the direction of the electric field" means that the direction of discharge is the same as the direction opposite to the direction of the electric field, or the direction diagonally advances toward the opposite direction of the electric field. It is meant to include cases.

In this embodiment, the reverse electric field portion 4 is constructed by a screw structure. That is, the insulating connecting portion 7
The reverse electric field portion 4 is formed between the female screw 8 forming the mounting portion of the above and the male screw 5 cut by the solid insulator 3 on the side of the cable 1 which meshes with the female screw 8.
Is configured. One slope of the screw thread turns the connection surface between the insulating connection portion 7 and the solid insulator 3 back to the conductor 2 side, and functions as the reverse electric field portion 4. Moreover,
It is repeatedly formed by the number of threads. Dielectric strength is further improved. Moreover, the total creepage distance is much longer than the creepage distance when the start point and the end point are connected by a straight line.

Further, in this embodiment, the opposing conductors 2,
In order to satisfactorily electrically connect the two, the holes penetrating between the female screws 8 and 8 are provided with contacts 11 made up of a conducting member 9 and contact fingers (elastic contacts) 10. The conductors 2 of the cables 1 to be connected are respectively held by the contact fingers 10 to be surely electrically connected and electrically connected via the conducting member 9. The contact fingers 10 and the intermediate conductor 9 may be integrally molded depending on the case. The contact finger 10 is made of a conductive material such as copper, and is configured to have an elastic contact portion that is deformed by coming into contact with the conductor 2. For example, in the present embodiment, the end of the bottomed cylindrical contact finger 10 is folded back inward to form an elastic contact portion / leaf spring that reliably contacts and deforms the conductor 2. It should be noted that the inner surface of the bottomed cylindrical contact finger 10 may be provided with a convex portion that comes into contact with the conductor 2 and deforms continuously or intermittently. Of course, a contact 11 having a different structure other than the above-mentioned structure may be interposed, or the conductors 2 may be directly abutted without interposing the contact 11 to secure the electrical connection.

The high voltage cable 1 of this embodiment is generally C
It is called a V cable, and is composed of a conductor 2 and a solid insulator 3 covering the periphery of the conductor 2 and made of a resin insulating material such as cross-linked polyethylene or polyvinyl chloride. Further, at the end of the solid insulator 3, a male screw 5 that is screwed with a female screw that is a mounting portion 8 of the connector 6 is provided.
Since this male screw 5 effectively forms the reverse electric field portion 4,
It is preferable to cut the pitch to be short (short lead) and the thread height to be high. Further, in the present embodiment, the end portion of the conductor 2 is provided so as to be slightly projected from the end portion of the solid insulator 3 and exposed so as to be reliably electrically connected to the contact 11 of the connector 6.

According to the connector 6 and the high voltage cable 1 configured as described above, the high voltage cables 1 and 1 to be connected are butted against each other via the connector 6, and the connector 6 is rotated in the direction of tightening the screw. For example, the male screws 5 and 5 of both high-voltage cables 1 and 1 and the female screw 8 of the connector 6 mesh at the same time, the male screws 5 and 5 simultaneously advance inside the connector 6, and eventually the conductors 2 and 2 contact the contact fingers 1.
By connecting to 0, both high voltage cables 1 and 1 are connected well electrically and mechanically.

Then, the reverse electric field portion 4 for folding back the connection surface between the insulative connection portion 7 and the solid insulator 3 to the conductor 2 side between the engaged screws 5 and 8 is repeatedly formed by the number of threads. Therefore, when a creeping discharge is about to occur, the discharge progresses from the conductor 2 along the boundary surface / connecting surface between the solid insulator 3 and the insulative connecting portion 7 of the connector 6, but alternates in the longitudinal section. To draw a bent line (Fig. 2
See the arrow inside). Therefore, the dielectric strength is improved. Furthermore, the total creepage distance by the zigzag route is longer than the creepage distance when the start point and the end point are connected by a straight line. This also improves the dielectric strength.

Therefore, according to the connector connection structure of this embodiment, sufficient dielectric strength can be obtained to prevent creeping discharge without increasing the size of the connection between the high voltage cables 1 and 1. In addition, the connection by screw has an advantage that it is superior in mechanical strength against pulling as compared with the connection by the conventional mold.

FIG. 3 shows an embodiment for realizing the method of the present invention without using the connector 6. In the cable connection structure of this embodiment, a male screw 5 is formed at one end of the solid insulator 3 of each high-voltage cable 1 and a female screw 5 ′ is formed at the other end thereof by threading or the like, so that the cable 1 and the cable 1 And are directly connected by screwing screws 5 and 5 '. Also in this case, the reverse electric field portion 4 is formed by the male and female screws 5 and 5 ′ at the connection point of the solid insulator 3. In the case of the cable connection structure of the present embodiment, the conductors 2 may be simply abutted against each other, but it is preferable to interpose an adjusting member for preventing conduction failure due to thermal expansion of the conductors 2 or the like. . For example,
As shown in FIG. 3, the conductor 2 of one cable 1 is slightly projected from the solid insulator 3, and the other cable 12 is
2 is slightly retracted from the solid insulator 3, the conductor 2 of one cable 1 is fitted into the solid insulator 3 of the other cable 1, and the conductor 2 is deformed by contacting the conductor 2. It is preferable to interpose the contact fingers 12 provided with. This contact finger 12 and the solid insulator 3 on the side of the cable 1 in which it is housed
Is fixed to the conductor 2 which is retracted from the end face of the one end of the cable 1 which is fitted into the contact finger 12.
The conductor 2 side is provided so as to be in sliding contact.

The reverse electric field portion 4 is not limited to the one having the screw structure as long as it has a direction in which the discharge progresses has a vector component opposite to the electric field direction. Alternatively, the connection may be made by using an insulating resin mold without using a detachable connecting means such as the connector 6. Such an embodiment is shown in FIG. The cable connection structure of this embodiment has a solid insulator 3
Each of the conductors 2 is formed by connecting the cables 1 in which at least one annular groove 14 is formed at the end of the
Are abutted against each other so as to be in direct contact with each other, and these are solidified with a resin mold 13 and joined. The cable 1 is connected in a straight line by engagement of the groove 15 with the flange 15 portion formed in the groove 14 of the solid insulator 3 in which the abutting portion of the conductor 2 is fixed by the resin mold 13. The number, size (depth, width), gradient, etc. of the grooves 14 are not limited to particular ones as long as the reverse electric field portion 4 is effectively configured. For example, in the example of FIG. 4, three annular grooves are provided side by side in the axial direction in the circumferential direction of the solid insulator 3. Also in this case, the reverse electric field portion 4 is formed on the connection surface between the solid insulator 3 and the mold 13, and the dielectric strength is improved. Further, in this case, since the three grooves 14 of the solid insulator 3 and the flange portion 15 of the mold 13 fitted therein are axially engaged, a connection structure having high mechanical strength against pulling can be obtained.

The present invention is not limited to the CV cable described above, but can be widely applied to high voltage cables having at least a conductor and a solid insulator covering the conductor. For example, it can be applied to a coaxial transmission line used in GIS or GIL. This coaxial transmission line 20 uses an insulating gas 23 and covers the inner conductor 22 with a solid insulator 25. That is, as shown in FIG. 5, the inner conductor 22, the solid insulator 25 such as cross-linked polyethylene covering the inner conductor 22, and the inner conductor 22.
And an external conductor 24 which is arranged coaxially with the solid insulator 25 and forms a space for insulation between the solid insulator 25 and the SF.
₆ or its substitute gas, for example, high pressure pure nitrogen gas 23. At the connection point 21 of the solid insulator 25 of the coaxial transmission line, there is provided the reverse electric field portion 4 which makes the traveling direction of the discharge have a vector component opposite to the electric field direction. For example, as shown in the enlarged view of FIG. 5, a flange 27 with an overhang having a hook-shaped cross section and a flange 26 that meshes with the flange 27 are provided at the ends of the opposing solid insulators 25. And the reverse electric field section 4 is configured. This coaxial transmission line 2
In the case of 0, the dielectric strength of the solid insulator 25 is added to the dielectric strength of the insulating gas, and the creeping discharge at the connection point 21, which is the greatest weakness of insulation with the solid insulator 25, is reduced to the reverse electric field portion 4. Since we are trying to eliminate it by providing it,
The necessary dielectric strength can be secured without increasing the space for insulation filled with the alternative gas 23, that is, without increasing the coaxial transmission line 20 itself. Therefore, the outer conductor 2 has a higher dielectric strength than the conventional coaxial transmission line using only SF ₆ as the insulating gas.
The size of the transmission line can be reduced by reducing the tube diameter of No. 4. Also when than SF ₆ using an alternative gas 23 is inferior in dielectric strength, since a reduction in the dielectric strength caused by adopting the alternative gas 23 supplement in the solid insulator 25, conventional coaxial transmission using SF ₆ Insulation similar to the line, that is, without increasing the size of the coaxial transmission line 20 itself,
The necessary dielectric strength can be secured.

The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, the connector 6 side may be a male screw and the high voltage cable 1 side may be a female screw. Further, the reverse electric field section 4 may be formed at the connection point of the solid insulator 3, and the reverse electric field section 4 and the connection structure do not necessarily have to be formed by the same thing.

[0033]

As is apparent from the above description, the method for connecting a high voltage cable according to claim 1, the structure for connecting a high voltage cable according to claim 2, and the connector for connecting a high voltage cable according to claim 4 are provided. According to this, by providing a reverse electric field part at the connection part of the solid insulator, the discharge must be advanced against the direction of the electric field, and the creepage distance also increases without changing the size of the connection part / connection part. Therefore, the dielectric strength is dramatically improved. Moreover, since the dielectric strength can be increased without enlarging the connecting portion, the high voltage cable can be connected in a compact manner.

Further, according to the connection structure of the high voltage cable of the third aspect, since the reverse electric field portion is constituted by the screw structure, one of the slopes forming the screw thread is a so-called reverse electric field portion. Since it is repeatedly formed, the dielectric strength can be further increased in combination with the dramatic increase in creepage distance. In addition, the screw connection has an advantage that it is superior in mechanical strength against pulling as compared with the conventional connection by molding.

Further, according to the high-voltage cable connecting connector of the fifth aspect, since the screws for connecting the high-voltage cable at both ends which also serve as the reverse electric field portion are constituted by the reverse screws, the long high-voltage cable itself. Without rotating
High voltage cables can be easily connected or disconnected by simply rotating the connector in one direction.

Further, according to the coaxial transmission line described in claims 6 and 7, the solid dielectric covering the inner conductor and the reverse electric field portion increase the dielectric strength at the connecting portion of the solid insulator to increase the creeping discharge. Since the creepage distance can be extended without increasing the size of the connecting portion, it is possible to increase the creeping distance without enlarging the insulating space, that is, without increasing the size of the coaxial transmission line itself. Dielectric strength can be obtained. Therefore, when SF ₆ having excellent dielectric strength is used, the dielectric strength is improved as compared with the conventional coaxial transmission line, and the outer conductor tube can be made smaller in diameter, that is, can be made smaller. Also, when using alternate gases dielectric strength of the insulating gas is inferior SF ₆ also, since the dielectric strength decreases by adopting the alternative gas can be compensated by the solid insulator, similar to the case of using the SF ₆ Insulation can be secured.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of a high-voltage cable and a connector for connecting a high-voltage cable, which realizes a method of connecting a high-voltage cable according to the present invention.

FIG. 2 is an enlarged cross-sectional view near the reverse electric field portion of FIG.

FIG. 3 is a schematic vertical cross-sectional view showing another example of a high-voltage cable that realizes the high-voltage cable connection method of the present invention.

FIG. 4 is a schematic vertical cross-sectional view showing an example of another connection structure of the high-voltage cable that realizes the method of connecting the high-voltage cable of the present invention.

FIG. 5 is a schematic vertical sectional view showing one embodiment of the coaxial transmission line of the present invention.

FIG. 6 is a schematic vertical sectional view showing a conventional method of connecting a high-voltage cable.

FIG. 7 is a schematic vertical sectional view of a coaxial transmission line used in conventional GIS and GIL.

FIG. 8 is a schematic side sectional view showing a conventional coaxial transmission line.

[Explanation of symbols]

1 High voltage cable 2 Cable conductor 3,15 Solid insulator 4 Reverse electric field section 5 Male screw (mounting part) 6 High voltage cable connector 7 Insulating connection 8 Female thread (mounting part) 12 inner conductor 24 outer conductor

Continued front page    (72) Inventor Koji Goto             2-11-1 Iwatokita, Komae City, Tokyo Foundation             Central Research Institute of Electric Power Komae Research Center F term (reference) 5E087 EE02 EE08 EE10 FF07 FF12                       HH01 JJ04 RR04 RR18 RR34

Claims (7)

[Claims] 1. A method of connecting a high-voltage cable, comprising a conductor covered with a solid insulator, which may cause a creeping discharge and a dielectric breakdown at a connection point of the solid insulator. A method for connecting a high-voltage cable, characterized in that a reverse electric field portion is provided at a location, the reverse electric field portion having a direction in which a discharge progresses has a vector component opposite to an electric field direction. 2. A connection structure for a high voltage cable, comprising a conductor covered with a solid insulator, which may cause a creeping discharge and a dielectric breakdown at a connection point of the solid insulator. A connection structure for a high-voltage cable, characterized in that a reverse electric field portion is provided at a location, the reverse electric field portion having a vector component opposite to the electric field direction. 3. The connection structure for a high voltage cable according to claim 2, wherein the reverse electric field portion has a screw structure. 4. A connector for connecting high voltage cables each having a conductor covered with a solid insulator, and an insulating connection portion for mechanically connecting the solid insulators of the opposing high voltage cables. And a conducting portion for electrically connecting the conductor, and a direction having a vector component in which a discharge progress direction is opposite to an electric field direction at a connection portion between the insulating connection portion and the solid insulator. A connector for connecting a high-voltage cable, characterized in that a reverse electric field section is provided. 5. The reverse electric field portion has a screw structure, and a screw for connecting one high-voltage cable and a screw for connecting the other high-voltage cable are reverse screws. The connector for connecting a high voltage cable according to claim 4. 6. A coaxial transmission line comprising an inner conductor, an outer conductor coaxially arranged with a space provided between the inner conductor, and an insulating gas filled in the space, wherein the inner conductor is surrounded by the inner conductor. Is covered with a solid insulator, and a reverse electric field portion is provided at a connection point between the solid insulators, the reverse electric field portion having a vector component having a vector component opposite to an electric field direction in a discharge direction. line. 7. The coaxial transmission line according to claim 6, wherein the insulating gas is a substitute gas for sulfur hexafluoride gas.