JP2022187103A - Termination structure of power cable, cylinder unit and cylindrical component - Google Patents

Abstract

To provide a termination structure of a power cable which can reduce the electric field stress at the time of applying DC and which is superior in impulse characteristic, a cylinder unit, and a cylindrical component.SOLUTION: A termination structure of a power cable includes a terminal part of the power cable, a stress cone, a resistance part, and an insulation fluid. The terminal part of the power cable includes a first exposure part of an outer semiconductor layer and an exposure part of an insulation layer. The stress cone includes an insulation cylindrical part and a semiconductive part. The resistance part is a cylindrical body composed of a functionally graded material whose resistance rate changes according to a magnitude of an electric field, and it includes a first inner peripheral surface which is brought into contact with an entire outer peripheral surface of the insulation cylindrical part, a second inner peripheral surface which is brought into contact with a portion which is not covered by the insulation cylindrical part in the exposure part of the insulation layer, and a first end part which is brought into contact with the semiconductive part without contacting the first exposure part. The insulation fluid is brought into contact with an outer peripheral surface of the resistance part without contacting the exposure part of the insulation layer and the insulation cylindrical part.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to a power cable termination structure, a tubular unit, and a tubular component.

Patent Literature 1 discloses a structure in which an electric field relaxation adapter and a stress cone are arranged in order on an insulating layer provided in a power cable as a terminal portion of a power cable to which high-voltage direct current is applied. Hereinafter, the structure disclosed in Patent Document 1 will be referred to as the first conventional structure.

The field-relaxing adapter is a cylinder made of linear or non-linear resistive field-relaxing material (FGM, Functionally Graded Material). The electric field mitigation adapter is electrically connected to the power cable so as to take a 0% potential from a 100% potential. Specifically, one end of the two ends of the electric field relaxation adapter is electrically connected to a portion having the same potential as the conductor provided in the power cable. The other end of the two ends is in contact with an outer semi-conductive layer provided on the power cable. The end electrically connected to the conductor is the end at 100% potential, ie, the end on the high potential side. The end contacting the outer semi-conductive layer is the end at 0% potential, that is, the end on the low potential side, which is the ground potential. When a direct current is applied to the electric field relaxation adapter, the resistivity of the electric field relaxation adapter changes linearly or nonlinearly depending on the magnitude of the electric field.

Japanese Patent Publication No. 2017-529815

In the first conventional structure described above, the electric field stress applied to the triple contact portion when a high voltage direct current is applied is reduced compared to the second conventional structure that does not include the electric field relaxation adapter. However, the first conventional structure described above is inferior in impulse characteristics.

The triple contact mentioned above is the part where three different materials are in contact and occurs at the high potential end of the stress cone. In the second conventional structure described above, the triple contact portion is a portion where the insulating layer provided on the power cable, the electrically insulating rubber portion provided on the stress cone, and the insulating oil filled outside the stress cone come into contact. In the first conventional structure described above, the triple contact portion is a portion where the rubber portion, the electric field relaxation adapter, and the insulating oil are in contact.

An object of the present disclosure is to provide a termination structure for a power cable that can reduce electric field stress during direct current application and has excellent impulse characteristics. Another object of the present disclosure is to provide a tubular unit and a tubular component used in a power cable termination structure.

A power cable termination structure according to an aspect of the present disclosure includes a power cable terminal portion having a conductor, an insulating layer, an external semiconductive layer, and a shield layer in order from the inside, and a stress cone arranged outside the insulating layer. , a resistor located outside the insulating layer; and an insulating fluid located outside the stress cone and outside the resistor.
The terminal portion of the power cable has a first exposed portion, which is the outer semi-conductive layer exposed from the shielding layer, and an exposed portion, which is the insulating layer exposed from the outer semi-conductive layer.
The stress cone has an insulating tubular portion in contact with a portion of the exposed portion of the insulating layer, and a semiconductive portion provided at an end portion of the insulating tubular portion so as to come into contact with the first exposed portion.
The resistance part is a cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. The resistance portion has a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating tubular portion, a second inner peripheral surface in contact with a portion of the exposed portion of the insulating layer that is not covered with the insulating tubular portion, and a first end contacting the semiconducting portion without contacting the first exposed portion.
The insulating fluid contacts the outer peripheral surface of the resistance portion without contacting the exposed portion of the insulating layer and the insulating cylindrical portion.

A tube unit according to an aspect of the present disclosure is a tube unit used in a power cable termination structure including a power cable end portion and an insulating fluid, and includes a stress cone and a resistance portion disposed outside the stress cone. and
The stress cone has an insulating tubular portion and a semiconductive portion provided at an end of the insulating tubular portion.
The resistance part is a cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. The resistance portion has a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating tubular portion, a second inner peripheral surface not in contact with the outer peripheral surface of the insulating tubular portion, and a first end in contact with the semiconductive portion. and an outer peripheral surface arranged to be in contact with the insulating fluid.

A tubular component according to an aspect of the present disclosure is a tubular component used in a power cable termination structure including a power cable terminal portion, a stress cone, and an insulating fluid. This tubular part is a molded body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. This cylindrical component has a first inner peripheral surface arranged so as to be in contact with the entire outer peripheral surface of the insulating cylindrical portion provided in the stress cone, and a terminal portion of the power cable that is not in contact with the insulating cylindrical portion. a second inner peripheral surface arranged to contact the insulating layer provided on the stress cone; It has an end portion and an outer peripheral surface positioned in contact with the insulating fluid.

The power cable termination structure of the present disclosure can reduce electric field stress during direct current application and has excellent impulse characteristics. The tubular unit and tubular component of the present disclosure can construct a termination structure of a power cable that can reduce electric field stress when direct current is applied and has excellent impulse characteristics.

FIG. 1 is a partial cross-sectional view schematically showing a termination structure of a power cable according to Embodiment 1. FIG.

[Description of Embodiments of the Present Disclosure]
One of the reasons why the first conventional structure described above is inferior in impulse characteristics is considered as follows. When an impulse is applied to the end of the power cable, the electric field concentrates in and around the portion of the outer semi-conductive layer of the power cable exposed from the shield layer. Since the low potential side end of the electric field relaxation adapter is in contact with the exposed portion of the outer semi-conductive layer, the electric field concentrates on the low potential side end. Concentration of the electric field may cause dielectric breakdown at the end on the low potential side. Therefore, the present disclosure proposes a structure in which the arrangement of the ends on the low potential side is different from the first conventional structure. First, the contents of the embodiments of the present disclosure will be listed and described.

(1) A power cable termination structure according to one aspect of the present disclosure includes a power cable terminal portion having a conductor, an insulating layer, an external semiconductive layer, and a shield layer in order from the inside, and a power cable disposed outside the insulating layer. A stress cone, a resistor located outside the insulating layer, and an insulating fluid located outside the stress cone and outside the resistor.
The terminal portion of the power cable has a first exposed portion, which is the outer semi-conductive layer exposed from the shielding layer, and an exposed portion, which is the insulating layer exposed from the outer semi-conductive layer.
The stress cone has an insulating tubular portion in contact with a portion of the exposed portion of the insulating layer, and a semiconductive portion provided at an end portion of the insulating tubular portion so as to come into contact with the first exposed portion.
The resistance part is a cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. The resistance portion has a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating tubular portion, a second inner peripheral surface in contact with a portion of the exposed portion of the insulating layer that is not covered with the insulating tubular portion, and a first end contacting the semiconducting portion without contacting the first exposed portion.
The insulating fluid contacts the outer peripheral surface of the resistance portion without contacting the exposed portion of the insulating layer and the insulating cylindrical portion.

The resistive portion prevents the exposed portion of the insulating layer from contacting the insulating fluid. A resistance part contacts with an insulating fluid. Therefore, in the power cable termination structure of the present disclosure, the triple contact portion is a portion where the exposed portion of the insulating layer, the insulating tubular portion of the stress cone, and the resistance portion are in contact. Such a power cable termination structure of the present disclosure can reduce the electric field stress applied to the triple contact portion by the resistance portion.

The first end of the resistive portion is electrically connected to the first exposed portion of the outer semiconductive layer by contacting the semiconductive portion of the stress cone. Since the outer semiconducting layer is grounded, this connection brings the first end of the resistor to ground potential. That is, the first end of the resistance portion is the end on the low potential side. However, the first end of the resistance portion does not directly contact the first exposed portion where the electric field concentrates when the impulse is applied. Such a power cable termination structure of the present disclosure is superior in impulse characteristics as compared with the first conventional structure described above.

(2) As an example of the power cable termination structure of the present disclosure, the terminal portion of the power cable has a second exposed portion that is the external semiconductive layer exposed from the shielding layer, and the insulating layer is exposed. is disposed between the first exposed portion and the second exposed portion, and the second exposed portion is electrically connected to the end portion of the conductor exposed from the insulating layer. , the resistive portion has a second end electrically connected to the second exposed portion;

The above configuration can shorten the length of the resistance part compared to the case where the second end is directly connected to the conductor of the power cable.

(3) As an example of the power cable termination structure of the present disclosure, the resistance portion is a molded body.

In the above configuration, the termination structure of the power cable can be constructed by fitting the resistance portion to the exposed portion of the insulating layer and the outer circumference of the stress cone.

(4) As an example of the power cable terminating structure of (3) above, the insulating tubular portion and the resistance portion are integrated.

In the above configuration, the stress cone and the resistance portion can be fitted together on the outer periphery of the exposed portion of the insulating layer.

(5) As an example of the power cable termination structure of the present disclosure, the resistance portion is formed by winding a tape material made of the functionally gradient material around the outer periphery of the insulating tubular portion in a tubular shape.

With the above configuration, the resistance portion can be formed regardless of the size of the exposed portion of the insulating layer and the size of the stress cone.

(6) As an example of the power cable termination structure of the present disclosure, the constituent material of the insulating layer contains an inorganic filler.

The above configuration can reduce deterioration in characteristics when a direct current is applied.

(7) As an example of the power cable termination structure of the present disclosure, the constituent material of the insulating layer does not contain an inorganic filler.

The above-mentioned form can reduce manufacturing costs in that no inorganic filler is required.

(8) A cylinder unit according to an aspect of the present disclosure is a cylinder unit used in a power cable termination structure including a power cable end portion and an insulating fluid, and is arranged outside the stress cone and the stress cone. and a resistor.
The stress cone has an insulating tubular portion and a semiconductive portion provided at an end of the insulating tubular portion.
The resistance part is a cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. The resistance portion has a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating tubular portion, a second inner peripheral surface not in contact with the outer peripheral surface of the insulating tubular portion, and a first end in contact with the semiconductive portion. and an outer peripheral surface arranged to be in contact with the insulating fluid.

The tubular unit of the present disclosure is arranged to cover the portion of the insulating layer of the power cable that is exposed from the outer semi-conductive layer. In the power cable termination structure including the tubular unit of the present disclosure, the triple contact portion is a portion where the exposed portion of the insulating layer, the insulating tubular portion of the stress cone, and the resistance portion are in contact. Such a tube unit of the present disclosure can construct a power cable termination structure that can reduce the electric field stress applied to the triple contact.

In the power cable termination structure including the tube unit of the present disclosure, the semi-conductive portion of the stress cone is arranged to contact the portion of the outer semi-conductive layer of the power cable that is exposed from the shield layer. A first end of the resistive portion is electrically connected to the exposed portion of the outer semiconductive layer by contacting the semiconductive portion. Since the outer semiconducting layer is grounded, this connection brings the first end of the resistor to ground potential. That is, the first end of the resistance portion is the end on the low potential side. However, the first end of the resistor section does not directly contact the exposed portion of the outer semiconducting layer where the electric field concentrates when the impulse is applied. Such a tube unit of the present disclosure can construct a termination structure for a power cable that has superior impulse characteristics compared to the first conventional structure described above.

(9) A tubular component according to an aspect of the present disclosure is a tubular component used in a power cable termination structure including a power cable terminal portion, a stress cone, and an insulating fluid. This tubular part is a molded body made of a functionally graded material whose resistivity changes according to the magnitude of the electric field. This cylindrical component has a first inner peripheral surface arranged so as to be in contact with the entire outer peripheral surface of the insulating cylindrical portion provided in the stress cone, and a terminal portion of the power cable that is not in contact with the insulating cylindrical portion. a second inner peripheral surface arranged to contact the insulating layer provided on the stress cone; It has an end portion and an outer peripheral surface positioned in contact with the insulating fluid.

The tubular component of the present disclosure is arranged to cover the portion of the insulating layer of the power cable that is exposed from the outer semi-conductive layer and the insulating tubular portion of the stress cone. In the power cable termination structure including the tubular component of the present disclosure, the triple contact portion is a portion where the exposed portion of the insulating layer, the insulating tubular portion of the stress cone, and the tubular component of the present disclosure are in contact. Such tubular part of the present disclosure can construct a power cable termination structure capable of reducing the electric field stress applied to the triple contact.

In the power cable termination structure including the tubular component of the present disclosure, the semi-conductive portion of the stress cone is arranged to contact the portion of the outer semi-conductive layer of the power cable that is exposed from the shield layer. The first end of the tubular component is electrically connected to the exposed portion of the outer semi-conductive layer by contacting the semi-conductive portion. Since the outer semiconducting layer is grounded, this connection brings the first end of the tubular part of the present disclosure to ground potential. That is, the first end of the tubular component of the present disclosure is the end on the low potential side. However, the first end of the tubular part of the present disclosure does not directly contact the exposed portion of the outer semi-conductive layer where the electric field concentrates when the impulse is applied. Such a cylindrical component of the present disclosure can construct a power cable termination structure that is superior in impulse characteristics compared to the above-described first conventional structure.

[Details of the embodiment of the present disclosure]
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the figure, the same reference numerals denote the same name. The present invention is not limited to these exemplifications, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

[Embodiment 1]
(overview)
A power cable termination structure according to the first embodiment will be described with reference to FIG.
FIG. 1 is a cross section of the power cable termination structure of Embodiment 1 taken along a plane parallel to the longitudinal direction of the power cable. However, the power cable shows the appearance, not the cross section. Moreover, FIG. 1 shows only the portion where the stress cone is arranged and its peripheral portion in the power cable termination structure of the first embodiment. It should be noted that FIG. 1 shows only the right half of the termination structure and omits the left half of the termination structure. The structure of the left half is similar to that of the right half. The upper side of FIG. 1 corresponds to the tip side of the power cable. The lower side of FIG. 1 corresponds to the rear end side of the power cable. The tip side of the power cable is the side on which the end portion of the conductor exposed from the insulating layer, which will be described later, is arranged. Also, in FIG. 1, for convenience of explanation, the size and size ratio of each component may differ from the actual size. Note that the longitudinal direction of the power cable corresponds to the vertical direction in FIG.

A power cable termination structure 1 of Embodiment 1 is provided at a terminal portion 2 of a power cable for connecting the power cable to an external connection target (not shown). The external connection target is, for example, a power device, an overhead transmission line, or the like.

The power cable termination structure 1 of Embodiment 1 is a structure in which insulating oil 5 is filled around a terminal portion 2 of the power cable, which is an air termination connection portion. For the basic configuration of the power cable termination structure 1 of the first embodiment, reference can be made to a known air termination connection portion of a power cable. First, the basic configuration will be described below. The power cable termination structure 1 of Embodiment 1 includes a power cable terminal portion 2 , a stress cone 3 , a resistance portion 4 and an insulating oil 5 . The power cable terminal portion 2 includes a first exposed portion 221 that is the outer semi-conductive layer 22 exposed from the shielding layer 23 and an exposed portion 210 that is the insulating layer 21 exposed from the outer semi-conductive layer 22 . A stress cone 3 is arranged outside the exposed portion 210 of the insulating layer 21 . Further, the resistor portion 4 is also arranged outside the exposed portion 210 of the insulating layer 21 . The resistance part 4 is a cylindrical body and is made of a functionally graded material (FGM) whose resistivity changes depending on the magnitude of the electric field. A first end 41 of the resistor portion 4 contacts a semi-conductive portion 36 provided on the stress cone 3 . Insulating oil 5 is arranged outside the stress cone 3 and outside the resistance portion 4 .

In the first conventional structure described above, the electric field relaxation adapter described above is arranged inside the stress cone. Also, the low-potential end of the electric field relaxation adapter is in contact with the exposed portion of the outer semi-conductive layer of the power cable. On the other hand, in the power cable termination structure 1 of Embodiment 1, one of the features is that the resistance portion 4 is arranged outside the stress cone 3 instead of inside the stress cone 3 . Another feature is that the first end portion 41 , which is the end portion of the resistance portion 4 on the low potential side, is not in contact with the first exposed portion 221 of the external semiconductive layer 22 .

First, the constituent members will be described below. Next, a specific structure of the power cable termination structure 1 will be described.

(Constituent member)
<Power cable>
The power cable has a conductor 20, an insulating layer 21, an outer semi-conductive layer 22 and a shielding layer 23 in order from the inside. Furthermore, the power cable comprises an inner semi-conductive layer (not shown) inside the insulating layer 21 and a sheath (not shown) outside the shielding layer 23 . A typical example of such a power cable is a cross-linked polyethylene insulated vinyl sheath cable (CV cable).

The constituent material of the insulating layer 21 is an electrical insulating material. A specific example of the electrical insulating material is a resin composition such as the crosslinked polyethylene described above. The constituent material may be a resin composition containing one or more fillers. The constituent material of the insulating layer 21 in this example is crosslinked polyethylene containing an inorganic filler. Inorganic fillers are, for example, silicon oxide, magnesium oxide and the like. The inorganic filler has the effect of reducing the deterioration of the DC characteristics of the insulating layer 21 due to the generation of space charges in the insulating layer 21 when DC is applied. The DC characteristics include volume resistivity, DC breakdown electric field intensity, space charge characteristics, and the like. If the inorganic filler is a fine particle having a nano-order particle size, it is easily dispersed uniformly in the base resin. As a result, the deterioration of the DC characteristics is likely to be reduced.

Known materials can be used for the conductor 20, the inner and outer semiconductive layers 22, the shielding layer 23, and the sheath.

The power cable termination structure 1 of Embodiment 1 is used for high-voltage power transmission, such as power cable power transmission voltages of 250 kV or higher, 400 kV or higher, and further 500 kV or higher. The cross-sectional area of the conductor, the thickness of the insulating layer 21, and the like are set according to the transmission voltage.

<Stress Cone>
The stress cone 3 has an insulating tubular portion 30 and a semiconductive portion 36 . The stress cone 3 of this example is a molded body in which the insulating tubular portion 30 and the semiconductive portion 36 are integrated.

The insulating tubular portion 30 typically has a spindle-shaped outer shape. Specifically, the first end portion 31 side portion and the second end portion 32 side portion of the insulating tubular portion 30 are tapered. The thickness of the intermediate portion of the insulating tubular portion 30 is thicker than the minimum thickness of the portions on the both end portions 31 and 32 side. The insulating tube portion 30 includes the two ends 31 and 32 described above, a cylindrical hole, an inner peripheral surface 301 and an outer peripheral surface 300 . The hole extends from the first end 31 to the second end 32 . The inner peripheral surface 301 forms this hole.

A constituent material of the insulating cylindrical portion 30 is, for example, an electrically insulating rubber. A specific example of the rubber is ethylene propylene diene rubber (EPDM). If the constituent material is rubber, the inner peripheral surface 301 of the insulating tubular portion 30 is in close contact with the exposed portion 210 of the insulating layer 21 due to the elastic force of the rubber. Known materials can be used for the constituent material of the insulating cylindrical portion 30 and the constituent material of the semi-conductive portion 36, which will be described later. A known molding method or the like can be used to manufacture the stress cone 3 .

A semiconductive portion 36 is provided on the first end portion 31 side of the insulating tubular portion 30 . Specifically, the semiconductive portion 36 is provided on the inner peripheral side on the first end portion 31 side. A portion of the semiconducting portion 36 is covered with the insulating cylinder portion 30 . The rest of the semiconductive portion 36 is exposed from the insulating tube portion 30 . A portion of the semiconducting portion 36 exposed from the insulating tubular portion 30 constitutes the inner peripheral surface of the stress cone 3 together with the inner peripheral surface 301 of the insulating tubular portion 30 .

The constituent material of the semiconducting portion 36 is a semiconducting material. Specific examples of semiconducting materials are the following rubber compositions. This rubber composition contains electrically insulating rubber such as EPDM and a conductive material such as carbon. Since the constituent material contains rubber, a portion of the exposed portion of the semiconductive portion 36 can be brought into close contact with the first exposed portion 221 of the external semiconductive layer 22 due to the elastic force of the rubber.

<Resistor part>
The resistance part 4 is a tubular body as described above. The resistance part 4 of this example is a molded body. Moreover, the resistance portion 4 of this example is integrated with the stress cone 3 as described later.

The resistance portion 4 has a first end portion 41 , a second end portion 42 , a cylindrical hole, an inner peripheral surface, and an outer peripheral surface 400 . The hole extends from the first end 41 to the second end 42 . The inner peripheral surface forms this hole. In addition, the inner peripheral surface has a first inner peripheral surface 401 arranged on the first end portion 41 side and a second inner peripheral surface 402 arranged on the second end portion 42 side. The outer peripheral surface 400 is arranged on the side opposite to the inner peripheral surface.

The thickness of the resistor portion 4 can be selected as appropriate. Although the resistor portion 4 in this example has a uniform thickness over the entire length of the resistor portion 4, the resistor portion 4 may have locally thicker portions or locally thinner portions. The thickness here is the distance between the inner peripheral surface of the resistance portion 4 and the outer peripheral surface 400 . The length of the resistor portion 4 is adjusted according to the length of the exposed portion 210 of the insulating layer 21 . The length of the resistance portion 4 is longer than the length of the insulating cylinder portion 30 . The length here is the size along the longitudinal direction of the power cable.

A specific example of the functionally gradient material, which is a constituent material of the resistance portion 4, is the following rubber composition. The rubber composition includes electrically insulating rubber such as EPDM, a conductive material such as carbon, and one or more electrically insulating ceramics. Specific examples of the ceramics are silicon carbide, zinc oxide, zirconium oxide and the like. A known material can be used for the functionally gradient material. A known molding method or the like can be used to manufacture the resistance portion 4 made of the molded body of this example. In addition to the molded body of this example, the cylindrical body forming the resistance portion 4 includes a cylindrically wound tape material as shown in Modification 1 described later.

The resistor part 4 is electrically connected to the terminal part 2 of the power cable so that the second end part 42 has a 100% potential and the first end part 41 has a 0% potential when a voltage is applied. Due to this connection, when an electric field is applied to the resistance section 4 when a voltage is applied, the resistivity of the resistance section 4 changes linearly or nonlinearly. In particular, it is preferable to adjust the composition of the functionally graded material so that the resistivity of the resistor portion 4 is greatly reduced when a relatively large electric field is applied. The power cable termination structure 1 having such a resistance portion 4 can effectively reduce the electric field applied to the triple contact portion 9 when a high voltage direct current is applied.

<Tube unit>
The power cable termination structure 1 of Embodiment 1 includes a tube unit 6 . The tube unit 6 includes a stress cone 3 and a resistance portion 4. - 特許庁The tube unit 6 is an integrated body in which the insulating tube portion 30 and the resistance portion 4 are integrated.

A resistance portion 4 is arranged so as to cover the insulating cylinder portion 30 . That is, the insulating tubular portion 30 is arranged inside the resistance portion 4 . Moreover, the stress cone 3 and the resistor portion 4 are integrated so that the first end portion 31 of the insulating tube portion 30, the semiconductive portion 36, and the first end portion 41 of the resistor portion 4 are in contact with each other. Therefore, the first end portion of the tube unit 6 includes the first end portion 31 of the insulating tube portion 30 , the semiconductive portion 36 and the first end portion 41 of the resistance portion 4 . Further, the length of the insulating cylinder portion 30 is shorter than the length of the resistance portion 4 as described above. Therefore, the second end portion 32 of the insulating tube portion 30 and the second end portion 42 of the resistance portion 4 are shifted in the longitudinal direction of the tube unit 6 . A second end portion of the cylinder unit 6 corresponds to the second end portion 42 of the resistance portion 4 .

Since the length of the insulating tubular portion 30 is shorter than the length of the resistor portion 4 as described above, the insulating tubular portion 30 is covered with the resistor portion 4 over the entire length of the insulating tubular portion 30 . A first inner peripheral surface 401 of the resistance portion 4 is in contact with the entire outer peripheral surface 300 of the insulating tubular portion 30 . The second inner peripheral surface 402 of the resistance portion 4 does not contact the outer peripheral surface 300 of the insulating tubular portion 30 . The inner peripheral surface of the cylinder unit 6 is mainly composed of the insulating cylinder part 30 and the resistance part 4 because the insulating cylinder part 30 is shifted toward the first end part 41 side of the resistance part 4 . The inner peripheral surface of the tubular unit 6 on the side of the first ends 31 and 41 is mainly the inner peripheral surface 301 of the insulating tubular portion 30 . The inner peripheral surface of the cylinder unit 6 on the second end portion 42 side is the second inner peripheral surface 402 of the resistance portion 4 . In addition, since the entire surface of the outer peripheral surface 300 of the insulating tubular portion 30 is covered with the resistor portion 4 , the outer peripheral surface of the tubular unit 6 is mainly the outer peripheral surface 400 of the resistor portion 4 .

The tube unit 6 is manufactured, for example, as follows. After molding the stress cone 3, the constituent material of the resistance portion 4 is molded on the outer peripheral surface 300 of the stress cone 3 by injection molding or the like.

<Insulating oil>
Insulating oil 5 is an example of an insulating fluid. A specific example of the insulating oil 5 is silicone oil or the like. As the insulating oil 5, one having a known composition can be used.

The insulator 8 is filled with the insulating oil 5 . The porcelain tube 8 is used as a container for housing the terminal portion 2 of the power cable. The insulating tube 8 is made of an electrical insulating material such as resin. In addition, FIG. 1 virtually shows the porcelain pipe 8 by a two-dot chain line. Moreover, although FIG. 1 illustrates the case where the porcelain pipe 8 has a two-layer structure, it may have a single-layer structure.

(specific structure)
<End of power cable>
The end portion 2 of the power cable is step-stripped. Therefore, the ends of the above-described members that make up the power cable are exposed. Specifically, the terminal portion 2 of the power cable includes the exposed portion 210 of the insulating layer 21, the first exposed portion 221 of the outer semi-conductive layer 22, and the end portion of the conductor 20 exposed from the insulating layer 21. . Further, the terminal portion 2 of the power cable includes a portion of the shielding layer 23 exposed from the sheath and the like. The terminal portion 2 of the power cable of this example comprises a second exposed portion 222 which is the outer semi-conductive layer 22 exposed from the shielding layer 23 . The first exposed portion 221 and the second exposed portion 222 are spaced apart in the longitudinal direction of the power cable. A first exposed portion 221 is arranged on the rear end side of the power cable. A second exposed portion 222 is disposed on the distal end side of the power cable. Therefore, the exposed portion 210 of the insulating layer 21 is arranged between the first exposed portion 221 and the second exposed portion 222 .

The second exposed portion 222 is used as a conducting portion for electrically connecting the resistance portion 4 and the end portion of the conductor 20 . Therefore, the second exposed portion 222 is electrically connected to the end of the conductor 20 . The illustration of the end of the conductor 20 is omitted.

The exposed portion 210 of the insulating layer 21 is covered with the stress cone 3 and the resistor portion 4 . In this example, the exposed portion 210 of the insulating layer 21 is covered with the cylinder unit 6 . Specifically, the portion of the exposed portion 210 of the insulating layer 21 on the distal end side of the power cable is covered with the resistor portion 4 . The portion of the exposed portion 210 of the insulating layer 21 on the rear end side of the power cable is covered with the insulating cylindrical portion 30 .

The first exposed portion 221 of the external semi-conductive layer 22 is used as a conducting portion for grounding the semi-conductive portion 36 of the stress cone 3 and the first end portion 41 of the resistor portion 4 .

<Tube unit>
An inner peripheral surface 301 of the insulating cylindrical portion 30 is arranged so as to be in contact with a part of the exposed portion 210 of the insulating layer 21 on the rear end side. A portion of the semiconductive portion 36 exposed from the insulating tube portion 30 is arranged so as to be in contact with the first exposed portion 221 of the external semiconductive layer 22 . Since the external semi-conductive layer 22 is grounded, the semi-conductive portion 36 is grounded by contact with the first exposed portion 221 .

The first inner peripheral surface 401 of the resistance portion 4 is in contact with the outer peripheral surface 300 of the insulating tubular portion 30 as described above. The second inner peripheral surface 402 of the resistor portion 4 is arranged so as to be in contact with the distal end portion of the exposed portion 210 of the insulating layer 21 that is not covered with the insulating cylindrical portion 30 . With this arrangement, the second end portion 32 of the insulating tubular portion 30 does not have a triple contact portion where the exposed portion 210 of the insulating layer 21 , the insulating tubular portion 30 of the stress cone 3 , and the insulating oil 5 contact each other. In addition, the triple contact portion composed of the insulating tubular portion 30, the resistance portion 4, and the insulating oil 5 does not occur at the second end portion 32 of the insulating tubular portion 30 either.

A first end portion 41 of the resistance portion 4 is arranged on the rear end side of the power cable. Specifically, the first end portion 41 is arranged so as to contact the semiconducting portion 36 without contacting the first exposed portion 221 of the external semiconducting layer 22 . As described above, the first end portion 41 of the resistor portion 4 is also at the ground potential by being in contact with the semi-conducting portion 36 at the ground potential. Therefore, the first end portion 41 of the resistor portion 4 is the end portion of the resistor portion 4 on the low potential side.

A second end portion 42 of the resistance portion 4 is arranged on the distal end side of the power cable. Specifically, the second end 42 is electrically connected to the second exposed portion 222 of the outer semi-conductive layer 22 . In this example, the second end portion 42 and the second exposed portion 222 are connected by a joint portion 49 . The joint 49 is made of a conductive material. The second end portion 42 of the resistor portion 4 is electrically connected to the end portion of the conductor 20 by the second exposed portion 222 and the joint portion 49 . With this connection, the second end portion 42 of the resistor portion 4 is the end portion on the high potential side of the resistor portion 4 by taking a 100% potential.

The tube unit 6 covers the exposed portion 210 of the insulating layer 21 . Moreover, as described above, in the cylinder unit 6 , the resistance part 4 covers the insulating cylinder part 30 . Therefore, the outer peripheral surface 400 of the resistance portion 4 , which is the outer peripheral surface of the cylinder unit 6 , is arranged so as to be in contact with the insulating oil 5 . The exposed portion 210 of the insulating layer 21 and the insulating tubular portion 30 of the stress cone 3 do not come into contact with the insulating oil 5 .

(Method for manufacturing power cable termination structure)
The power cable termination structure 1 of Embodiment 1 is constructed, for example, as follows.
(1) Terminal processing such as step stripping of the end of the power cable is performed.
(2) The tube unit 6 is fitted from the end portion side of the conductor 20 to the end portion 2 of the step-stripped power cable. If the tube unit 6 is previously expanded in diameter, the end portion 2 of the power cable can be easily inserted through the hole of the tube unit 6 . The fitting operation is performed until the semiconductive portion 36 of the cylindrical unit 6 contacts the first exposed portion 221 of the external semiconductive layer 22 .
(3) After the tube unit 6 is placed on the exposed portion 210 of the insulating layer 21, the second end portion 42 and the second exposed portion 222 are connected.
Other processes can refer to known procedures.

(Effect)
The triple contact portion 9 generated on the second end portion 32 side on the high potential side of the insulating cylinder portion 30 of the stress cone 3 is composed of the exposed portion 210 of the insulating layer 21 , the insulating cylinder portion 30 and the resistance portion 4 . The power cable termination structure 1 of Embodiment 1 does not have a triple contact portion configured by the exposed portion 210 of the insulating layer 21 , the insulating cylinder portion 30 and the insulating oil 5 . In the power cable termination structure 1 of Embodiment 1, the insulating oil 5 contacts the resistance portion 4 but does not contact the insulating layer 21 and the insulating cylindrical portion 30 . When a high voltage direct current is applied to the power cable termination structure 1 of the first embodiment, the electric field stress applied to the triple contact portion 9 is reduced by the resistance portion 4 .

The first end portion 41 of the resistor portion 4 on the low potential side does not directly contact the first exposed portion 221 of the external semiconductive layer 22 , but contacts the semiconductive portion 36 of the stress cone 3 . When an impulse is applied to the power cable termination structure 1 of Embodiment 1, concentration of the electric field on the first end 41 on the low potential side is reduced compared to the first conventional structure described above. be done. Therefore, dielectric breakdown of the first end portion 41 is less likely to occur. Therefore, the power cable termination structure 1 of Embodiment 1 is also superior in impulse characteristics as compared with the above-described first conventional structure.

The power cable termination structure 1 of this example also has the following effects.
(A) In this example, the second end portion 42 of the resistor portion 4 is connected to the second exposed portion 222 of the external semi-conductive layer 22 . This structure can shorten the length of the resistor portion 4 compared to a structure in which the second end 42 is directly connected to the end of the conductor 20 . The length of the resistance portion 4 can be set to 1 m or less, for example, depending on the operating voltage of the power cable. The resistance portion 4 having a short length is easy to mold. Such a resistor portion 4 is excellent in manufacturability.

(B) In this example, the molded body in which the stress cone 3 and the resistance portion 4 are integrated, that is, the cylinder unit 6 . Therefore, the stress cone 3 and the resistance portion 4 can be fitted into the exposed portion 210 of the insulating layer 21 at the same time. Such a structure of this example can shorten the construction time of the termination structure as compared with the case where the stress cone 3 and the resistance portion 4 are independent moldings. Also, the construction work is simple.

(C) In this example, the insulating layer 21 contains an inorganic filler. Such a structure of this example can reduce deterioration of DC characteristics such as volume resistivity, DC breakdown electric field strength, space charge characteristics, etc. when DC is applied.

[Test example]
We investigated how the electric field stress distribution changes depending on the presence or absence of the FGM member and the difference in the arrangement of the FGM member in the termination structure of the power cable. The FGM member is a cylindrical body made of a functionally graded material whose resistivity changes depending on the magnitude of the electric field.

(Description of sample)
Sample no. 1, No. The termination structure at 101 comprises the FGM members described above.
Sample no. 1 corresponds to the power cable termination structure 1 of the first embodiment described above. That is, sample no. One termination structure has an FGM member outside the stress cone. The low potential end of the FGM member is not in contact with the outer semi-conductive layer of the power cable, but is in contact with the semi-conductive portion of the stress cone.
Sample no. The termination structure at 101 corresponds to the first conventional structure described above. That is, sample no. The termination structure at 101 has an FGM member inside the stress cone. The low potential end of the FGM member contacts the outer semiconducting layer of the power cable and contacts the semiconducting portion of the stress cone. That is, the low potential end of the FGM member is sandwiched between the outer semi-conductive layer of the power cable and the semi-conductive portion of the stress cone.
Sample no. The termination structure at 102 does not have an FGM member and corresponds to the second conventional structure described above. Therefore, sample no. In the termination structure at 102, the triple contact is composed of the insulation layer of the power cable, the insulation sleeve of the stress cone, and the insulation oil.

(Measuring method)
In this test, the electric field stress distribution was determined by performing an electric field analysis. Known electric field analysis software using the finite element method (FEM) was used for the electric field analysis. Sample No. with FGM member. 1, No. In the termination structure of 101, analysis was performed assuming a power cable with a working voltage of 525 kV. Sample No. without the FGM member. In the termination structure of 102, the analysis was performed assuming a power cable with a working voltage of 400 kV class or less.

(Analysis result)
<When direct current is applied>
For the termination structure of each sample, the absolute value (kV/mm) of the electric field stress applied to the triple contact portion when direct current was applied was obtained. Sample no. Relative values are compared with the electric field stress applied to the triple contact portion of the termination structure 102 as a reference. Sample no. Assuming that the electric field stress of sample No. 102 is 1, sample No. 1, No. The electric field stress applied to the triple contact of the termination structure at 101 is less than 0.65. Sample no. The electric field stress of sample No. 1 was 0.46. It was even lower than the above electric field stress of 101. From this, it can be seen that the provision of the FGM member reduces the electric field stress applied to the triple contact portion when direct current is applied.

<When AC impulse is applied>
For the termination structure of each sample, the sharing ratio (%/mm) of the electric field stress applied to the end of the FGM member on the low potential side when an AC impulse was applied was determined. Sample no. Relative values are compared with the sharing ratio of the electric field stress applied to the end portion of the termination structure 101 as a reference. Sample no. Assuming that the electric field stress sharing ratio of sample No. 101 is 1, sample No. The sharing ratio of the electric field stress of 1 is 0.15. For this reason, by arranging the FGM member outside the stress cone and preventing the low-potential-side end of the FGM member from contacting the external semi-conductive layer of the power cable, the low-potential-side end of the FGM member is It can be seen that the electric field stress applied to the

From the above, it was quantitatively shown that the power cable termination structure 1 of Embodiment 1 can reduce the electric field stress at the time of direct current application and also has excellent impulse characteristics.

[Modification]
At least one of the following modifications can be made to the power cable termination structure 1 of the first embodiment.
(Modification 1)
The resistance part 4 is not a molded body. For example, the resistor portion 4 is formed by winding a tape material made of the above-described functionally gradient material around the outer periphery of the insulating tubular portion 30 of the stress cone 3 in a tubular shape. Illustration of the tape material is omitted.

In Modification 1, it is not necessary to shape the resistance portion 4 so as to have a size that matches the size of the exposed portion 210 of the insulating layer 21 and the size of the stress cone 3 . It is easy to change the area around which the tape material is wound, the width and thickness of the tape material, the number of times the tape material is wound, and the like. Therefore, the resistance portion 4 can be formed regardless of the size of the exposed portion 210 and the size of the stress cone 3 . Such modification 1 can be applied to power cables of any size, and therefore has a high degree of freedom in design.

(Modification 2)
The resistance portion 4 and the stress cone 3 are independent moldings. For example, the resistance part 4 is the cylindrical part 40 described below. The tubular component 40 has a first end portion 41 , a second end portion 42 , a first inner peripheral surface 401 , a second inner peripheral surface 402 and an outer peripheral surface 400 . Further, the tubular component 40 has a tubular hole penetrating from the first end 41 to the second end 42 . A first inner peripheral surface 401 and a second inner peripheral surface 402 form this hole.

The first end 41 is arranged in contact with the semi-conducting portion 36 provided on the stress cone 3 without contacting the external semi-conducting layer 22 provided on the power cable. The second end 42 is electrically connected to the end of the conductor 20 provided in the power cable. The first inner peripheral surface 401 is arranged so as to be in contact with the entire outer peripheral surface 300 of the insulating tubular portion 30 provided in the stress cone 3 . The second inner peripheral surface 402 is arranged so as not to come into contact with the insulating tubular portion 30 . Further, the second inner peripheral surface 402 is arranged so as to be in contact with the exposed portion 210 of the insulating layer 21 provided in the power cable and not covered with the insulating cylindrical portion 30 . The outer peripheral surface 400 is arranged so as to be in contact with the insulating oil 5 .

An example of such a cylindrical component 40 is a cylindrical molded body having uniform inner and outer diameters in the longitudinal direction of the cylindrical component 40, and is capable of contracting and deforming by heating. If the inner diameter of the cylindrical part 40 before heat shrinkage is larger than the maximum outer diameter of the insulating cylindrical part 30 , the insulating cylindrical part 30 arranged in the exposed part 210 of the insulating layer 21 can be easily inserted through the hole of the cylindrical part 40 . After the cylindrical component 40 is placed outside the insulating cylindrical portion 30 and the exposed portion 210 of the insulating layer 21, the cylindrical component 40 is heated. The thermal contraction of the tubular part 40 allows it to adhere to the insulating tubular portion 30 and the exposed portion 210 of the insulating layer 21 . As another example, the tubular part 40 may be formed into a tubular shape by combining two split parts. Further, as another example, the cylindrical component 40 may be configured by arranging a plurality of band-shaped members in a cylindrical shape around the outer periphery of the insulating cylindrical portion 30 . For example, the plurality of belt-shaped members are arranged in a cylindrical shape by being wound around the outer periphery of the insulating tubular portion 30 or vertically attached so as to surround the outer periphery of the insulating tubular portion 30 . Adjacent strips may partially overlap each other so that there is no gap between adjacent strips. Another strip-shaped material may be laminated so as to cover the seams of adjacent strip-shaped materials. Adjacent belt-like materials or laminated belt-like materials may be joined with an adhesive. The strip of material can cover insulating sleeves 30 of various sizes and shapes.

The cylindrical component of Modification 2 is provided in the termination structure 1 of the power cable, and thus has the same effect as the resistance portion 4 described in the first embodiment. That is, by using the cylindrical component of Modification 2, it is possible to construct the power cable termination structure 1 capable of reducing the electric field stress applied to the triple contact portion 9 . Further, by using the cylindrical component of Modification 2, it is possible to construct the power cable termination structure 1 that is superior in impulse characteristics as compared with the above-described first conventional structure. When the cylindrical part 40 is provided in the power cable termination structure 1 , the outer shape of the cylindrical part 40 follows the outer shape formed by the exposed portion 210 of the insulating layer 21 and the stress cone 3 .

(Modification 3)
The constituent material of the insulating layer 21 does not contain an inorganic filler. Modification 3 can reduce the manufacturing cost because it does not require an inorganic filler.

(Modification 4)
The insulating fluid is an insulating gas. Since the insulating gas is lighter than the insulating oil, the modified example 4 can reduce the weight of the termination structure of the power cable.

1 power cable termination structure 2 power cable terminal portion 3 stress cone 4 resistance portion 5 insulating oil 6 cylinder unit 8 porcelain tube 9 triple contact portion 20 conductor, 21 insulating layer, 22 external semiconductive layer, 23 shielding layer 30 insulating cylinder , 31 first end portion 32 second end portion 36 semiconductive portion 40 cylindrical component 41 first end portion 42 second end portion 49 joint portion 210 exposed portion 221 first exposed portion 222 second exposed portion Part 300 outer peripheral surface, 301 inner peripheral surface,
400 outer peripheral surface, 401 first inner peripheral surface, 402 second inner peripheral surface

Claims (9)

a terminal portion of a power cable having a conductor, an insulating layer, an outer semiconductive layer and a shielding layer in order from the inside;
a stress cone positioned outside the insulating layer;
a resistance portion arranged outside the insulating layer;
an insulating fluid arranged outside the stress cone and outside the resistor,
The terminal part of the power cable is
a first exposed portion, which is the outer semi-conductive layer exposed from the shielding layer;
and an exposed portion which is the insulating layer exposed from the outer semi-conductive layer,
The stress cone is
an insulating cylindrical portion in contact with a portion of the exposed portion of the insulating layer;
a semiconductive portion provided at an end portion of the insulating cylindrical portion so as to be in contact with the first exposed portion;
The resistance part is
a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating cylindrical portion;
a second inner peripheral surface in contact with a portion of the exposed portion of the insulating layer that is not covered with the insulating cylindrical portion;
a first end contacting the semiconducting portion without contacting the first exposed portion;
A cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of an electric field,
The insulating fluid is in contact with the outer peripheral surface of the resistance portion without contacting the exposed portion of the insulating layer and the insulating cylindrical portion,
Power cable termination structure. the terminal portion of the power cable has a second exposed portion which is the outer semiconductive layer exposed from the shielding layer;
The exposed portion of the insulating layer is arranged between the first exposed portion and the second exposed portion,
The second exposed portion is electrically connected to an end portion of the conductor exposed from the insulating layer,
2. The power cable termination structure according to claim 1, wherein said resistive portion has a second end electrically connected to said second exposed portion. 3. The power cable termination structure according to claim 1, wherein said resistance portion is a molded body. 4. The power cable termination structure according to claim 3, wherein said insulating tubular portion and said resistance portion are integrated. 3. The power cable termination structure according to claim 1, wherein said resistance portion is formed by winding a tape material made of said functionally gradient material around said insulating tubular portion in a tubular shape. The power cable termination structure according to any one of claims 1 to 5, wherein a constituent material of the insulating layer contains an inorganic filler. 6. The power cable termination structure according to any one of claims 1 to 5, wherein a constituent material of said insulating layer does not contain an inorganic filler. A tube unit used in a power cable termination structure comprising a power cable end portion and an insulating fluid,
A stress cone and a resistance portion arranged outside the stress cone,
The stress cone has an insulating tubular portion and a semiconductive portion provided at an end of the insulating tubular portion,
The resistance part is
a first inner peripheral surface in contact with the entire outer peripheral surface of the insulating cylindrical portion;
a second inner peripheral surface that is not in contact with the outer peripheral surface of the insulating cylinder;
a first end in contact with the semiconducting portion;
an outer peripheral surface arranged to be in contact with the insulating fluid;
A cylindrical unit, which is a cylindrical body made of a functionally graded material whose resistivity changes according to the magnitude of an electric field. A tubular part used in a power cable termination structure comprising a power cable end portion, a stress cone, and an insulating fluid,
a first inner peripheral surface arranged so as to be in contact with the entire outer peripheral surface of the insulating cylindrical portion provided in the stress cone;
a second inner peripheral surface arranged so as to be in contact with an insulating layer provided at a terminal portion of the power cable without being in contact with the insulating cylindrical portion;
a first end disposed in contact with a semi-conducting portion provided on the stress cone without contacting an external semi-conducting layer provided on the power cable;
an outer peripheral surface arranged to be in contact with the insulating fluid;
A molded body composed of a functionally graded material whose resistivity changes depending on the magnitude of the electric field,
barrel parts.

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