JPH0541342U - Electrical stress relief device for power cable - Google Patents

Abstract

(57) [Abstract] [Purpose] A stress cone used at the terminal or connection of a power cable can be brought into contact with a reinforced insulator with a large surface pressure by a small spring pressing force. [Structure] The stress cone 34 includes a reinforcing insulator 36 and an insulating layer 18 of the power cable 12 by a compression force of a spring 66.
It is pressed between the inner peripheral taper surface 40a and the inner peripheral taper surface 40a. The stress cone 34 is the inner peripheral tapered surface 40a of the reinforcing insulator 36.
A plurality of grooves 76 extending in parallel to the axial direction are provided on the surface contacting with each other at intervals in the circumferential direction. Therefore, the stress cone 34 comes into contact with the inner peripheral tapered surface of the reinforcing insulator 36 with a small contact area, and even with a small spring pressing force, the contact surface pressure between the two becomes large. Further, since the ends of these grooves 76 are open and the insulating fluid flows in, the electrical insulating performance does not deteriorate due to the formation of voids.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement in an electrical stress relieving device for a power cable used in, for example, a terminal portion or a connecting portion of a power cable.

[0002]

[Prior Art]

 Generally, as shown in FIG. 7, this type of electrical stress relieving device includes a stress cone 34 mounted between the insulating layer 18 of the power cable 12 and the reinforcing insulator 36, and an external inclination of the stress cone 34. 7 has a stress cone pressure contact member 62 to be joined to the surface and presses the stress cone 34 in the right direction (arrow direction) in FIG. 7 between the insulating layer 18 of the power cable 12 and the inner peripheral tapered surface 40a of the reinforcing insulator 36. And a spring pressing means (not shown) that compresses and supports between the insulating layer 18 of the electric power cable 12 and the reinforcing insulating body 36. In FIG. 7, the end portion 20 of the power cable 12 is shown. In FIG. 7, reference numeral 14 is a sheath of the power cable 12, 16 is an outer conductor of the power cable 12, 22 is an insulator, and 24 is this. A support insulator for supporting the porcelain insulator 22, 30 is a stress cone electrode, 30A is an electrode body of the stress cone electrode 30, and 30B is an electric field suppressing section.

In the conventional electrical stress mitigation device, the stress cone 34 has an interface 35 a that contacts the insulating layer 18 of the power cable 12 and an interface 35 b that contacts the tapered surface 40 a of the reinforcing insulator 36. If there are voids in 35a and 35b, the dielectric strength of these voids will be small, resulting in dielectric breakdown. Therefore, the entire surface will be contacted so that voids will not be formed, and the spring pressing means will have a close contact between these interfaces. The stress is applied to the stress cone 34 so as to do so.

[0004]

[Problems to be solved by the device]

 In the electrical stress relieving device for a power cable of this prior art, comparing the electrical stresses of the interfaces 35a and 35b of the stress cone 34 with the reinforcing insulator 36 and the insulating layer 18 of the power cable 12, the electrical stress of the interface 35b is compared. Stress is greater and the tendency to cause dielectric breakdown is higher. Therefore, the outer diameter of the stress cone 34, the shape and performance of the reinforcing insulator 36 are set so that the contact surface pressure at the interface 35b becomes larger than that at the interface 35a by the spring pressing means.

However, the contact surface pressure necessary for the interfaces 35a and 35b may be insufficient due to the low dimensional accuracy of these parts and insufficient adjustment of the pressure of the spring pressing means, and therefore the pressure of the spring pressing means is insufficient. However, if this pressure is increased, the outer shape of the spring pressing means becomes larger than necessary, the diameter of the terminal portion or the connection portion becomes large, and the stress cone and the reinforcing insulator may be damaged. .

An object of the present invention is to avoid the above-mentioned drawbacks and to prevent the dielectric breakdown by increasing the contact surface pressure at the interface between the stress cone and the power cable and the reinforcing insulator without increasing the spring pressing force. The purpose is to provide an electrical stress relieving device for a power cable.

[0007]

[Means for Solving the Problems]

 SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a stress cone mounted between an insulating layer of a power cable and a reinforcing insulator, and a stress cone, which is used as an insulating layer of the power cable and a tapered inner peripheral surface of the reinforcing insulator. In an electrical stress relieving device for a power cable, which comprises a spring pressing means which is pressed between the insulating layer of the power cable and a reinforced insulator to compress and support the stress cone and the insulating layer of the power cable. Electrical stress of power cable characterized by having a groove that opens at the tip so that the insulating fluid can flow into at least one of the contact surface of the stress cone or the inner surface of the reinforcing insulator To provide a device.

[0008]

[Action]

 In this way, a groove that opens at the tip is provided so that the insulating fluid can flow into at least one of the contact surface between the stress cone and the insulating layer of the power cable or the contact surface between the stress cone and the tapered inner peripheral surface of the reinforcing insulator. Therefore, even if the pressing force of the spring pressing means is not increased, the surface pressure at which these surfaces come into contact with the reinforced insulator is increased, so the electrical insulation performance at these interfaces is improved, and the grooves are filled with insulating oil or Since an insulating fluid such as an insulating gas flows in, the electrical insulation does not deteriorate in the gap formed by the groove.

[0009]

【Example】

 1 and 2 show a terminal portion 20 of a power cable 12 equipped with a power cable electrical stress relieving device 10 according to the present invention. However, the present invention can be applied to not only the terminal portion of the power cable but also the connection portion as well.

At the end of the power cable 12, the sheath 14, the outer conductor 16 and the insulating layer 18 are sequentially stripped off to expose the conductor, the outer conductor 16 and the insulating layer 18 which are not shown in order. The conductor is compression-connected to a terminal conductor of an electric device to form a terminal portion 20, and the terminal portion 20 includes a porcelain insulator 22. 1 and 2, reference numeral 24 is a support insulator that insulates and supports the porcelain insulator 22, and reference numeral 26 is a protective metal fitting that is attached across the power cable 12 and the terminal portion 20. The end portion of the protective metal fitting 26 on the electric power cable side is fixed to the sheath 14 of the electric power cable by an appropriate means, and a waterproof tape or the like is wound over the end portion of the protective metal fitting 26 and the sheath 14 to form the waterproof layer 28. Is formed.

As shown in detail in FIG. 2, the electrical stress relieving device 10 has a stress cone electrode 30 that is in close contact with the outer conductor 16 of the power cable 12, and the insulating layer 18 of the power cable 12 and the reinforcing insulator 36. And a spring pressing means 60 for pressing the stress cone 34 between the insulating layer 18 of the power cable 12 and the tapered portion 40a behind the reinforcing insulator 36. ing.

As shown in FIG. 2, the reinforcing insulator 36 includes a metal reinforcing portion 38 having a tubular portion 38 B extending in parallel to the axial direction from the inner edge of a donut-shaped annular metal plate 38 A, and the metal reinforcing portion 38. It is composed of a tubular resin reinforcing portion 40 molded from epoxy resin so as to fill the tubular portion 38B, and the inner end of the resin reinforcing portion 40 has a taper portion 40a whose inner circumference gradually becomes smaller.

The stress cone electrode 30 is provided on the surface of the stress cone 34 and is in close contact with the outer conductor 16 of the power cable 12, and the electrode cone 30 is embedded in the stress cone 34 and extends integrally from the electrode body 30 A. It is composed of an electric field suppressing unit 30B. The electric field suppressing unit 30B has a function of closely adhering to the outer conductor 16 of the power cable 12 and guiding the electric field of the outer conductor 16 to the right in FIG. 2 to moderate the electric field strength appropriately.

The reinforcing insulator 36 has an auxiliary electrode 42 extending from the metal reinforcing portion 38 and embedded in the resin reinforcing portion 40 so as to cooperate with the electric field suppressing portion 30B. The metal reinforcing portion 38 is fixed to the support insulator 24 by a set screw 46 so that the metal plate is closely attached to the insulator tube 22 via the seal packing 44. As shown in FIG. 1, the brim-shaped end portion 26a of the protective metal fitting 26 on the porcelain tube 22 side is fixed to the metal reinforcing portion 38 by a set screw 50 so as to be in close contact with the metal reinforcing portion 38 via a seal packing 48. Has been done.

The spring pressing means 60 includes a stress cone pressing member 62 that engages with the front inclined surface 34 a of the stress cone 34 and a spring rod 64 that is fixed by being screwed into the rear end flange portion 62 a of the stress cone pressing member 62. The coil spring 66 is wound around the coil spring 66, and the coil spring 66 is compressed by a spring pressing plate 70 attached to a support rod 68. The spring pressing plate 70 is engaged with a nut 72 screwed to the front end of the supporting rod 68, and the supporting rod 68 is screwed into the metal reinforcing portion 38 of the reinforcing insulator 36 to move the spring pressing plate 70 to the right. It is pressing. Therefore, the stress cone pressing member 62 pushes the stress cone 34 to the right by the pressing force applied to the coil spring 66 by the spring pressing plate 70 by screwing in the nut 72.

An insulating fluid such as insulating oil or insulating gas is filled in the space 56 surrounded by the porcelain insulator 22, the reinforcing insulator 36, the stress cone 34, and the like. Therefore, the electrical insulation performance of the terminal portion 20 of the power cable 12 can be sufficiently maintained.

As shown in FIGS. 2 and 3, the stress cone 34 is circumferentially spaced from the surface of the power cable 12 that contacts the insulating layer 18 and the surface of the reinforcing insulator 36 that contacts the tapered portion 40 a. It has a plurality of grooves 74, 76 provided in the direction parallel to the axial direction and provided at the tip end so that the insulating fluid can flow in. In the illustrated embodiment, eight grooves 74 and 76 are provided at intervals of 45 ° in the circumferential direction, and these grooves 74 and 76 are continuous by a turnback groove 78 at the tip. In FIG. 3, reference numeral 34b indicates a portion where the stress cone 34 comes into contact with the insulating layer 18 and the reinforcing insulating member 36 of the power cable 12.

As described above, when the grooves 74 and 76 are provided on the surface where the stress cone 34 contacts the insulating layer 18 of the power cable 12 and the surface where the stress cone 34 contacts the reinforcing insulator 36, the pressing force of the spring pressing means 60 is increased. Even if it does not exist, since the area of the contact portion 34b of the stress cone 34 becomes small, it is understood that the contact pressure between the contact portion 34b and the insulating layer 18 and the reinforcing insulator 36 of the power cable 12 becomes large. , 35b, the electric insulation performance is improved. Further, since the insulating fluid such as insulating oil or insulating gas flows into the grooves 74 and 76, the electrical insulation does not decrease in the gap between the grooves 74 and 76.

In the above embodiment, the grooves 74 and 76 are provided on both the surface of the stress cone 34 that contacts the insulating layer 18 of the power cable 12 and the surface of the reinforcing insulator 36 that contacts the inner peripheral tapered surface 40a. However, as already mentioned, the contact interface between the stress cone 34 and the tapered inner peripheral surface of the reinforcing insulator 36 has a higher possibility of dielectric breakdown than the contact interface between the stress cone 34 and the power cable 12. The groove 76 may be provided only on the surface of the stress cone 34 that comes into contact with the reinforcing insulator 36.

FIGS. 4 to 6 show another embodiment of the present invention. In this embodiment, in order to increase the contact surface pressure at the contact interface between the stress cone 34 and the tapered inner peripheral surface of the reinforcing insulator 36, The stress cone 34 is substantially the same as the embodiment shown in FIGS. 1 to 3 except that the grooves 74 and 76 are not provided and the plurality of grooves 80 are provided on the reinforcing insulator 36 side. 4 to 6, the same parts are designated by the same reference numerals. These grooves 80 are provided on the inner peripheral surface of the inner peripheral taper surface 40a of the reinforcing insulator 36 so as to extend in parallel with each other in the axial direction at intervals in the radial direction, and the tips are opened so that the insulating fluid flows in. is doing . 5 and 6, reference numeral 36a indicates a surface that contacts the stress cone 34, and reference numeral 36b indicates the bottom of the groove 80. The insulating fluid stops at the bottom 36b of the groove 80 and the stress cone 34 and the reinforcing insulator 36 are stopped. It is sealed so that it does not leak to the outside from between.

Also in this embodiment, the groove 80 provided on the inner peripheral taper surface of the reinforcing insulator 36 with which the stress cone 34 comes into contact with the stress cone 34 does not increase the pressing force of the spring pressing means 60. Since the area of the contact portion becomes small, it is understood that the surface pressure at which the contact portion contacts the stress cone 34 becomes large, and the electrical insulation performance at the interface 35b is improved. Further, since insulating fluid such as insulating oil or insulating gas flows into the groove 80, the electrical insulation performance is not deteriorated by the gap formed by the groove 80.

[0022]

[Effect of the device]

 According to the present invention, as described above, the contact pressure at the contact interface between the stress cone and the tapered inner peripheral surface of the reinforcing insulator can be increased without increasing the spring pressing force. The insulating fluid such as insulating oil or insulating gas flows into the groove to improve the electrical insulation performance and to increase the surface pressure. Even if the spring pressing means is used, there is a practical advantage that excellent electrical insulation performance of the terminal portion and the connection portion of the power cable can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an upper half of a terminal portion of a power cable including an electrical stress relieving device according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the electrical stress relieving device of the present invention.

FIG. 3 is a rear view of a stress cone used in the present invention.

FIG. 4 is an enlarged cross-sectional view of an essential part of another embodiment of the present invention.

5 is a rear view of the reinforced insulator used in the embodiment of FIG.

6 is a sectional view taken along line 6-6 of FIG.

FIG. 7 is a cross-sectional view showing, in an enlarged manner, a portion of a conventional electrical stress relieving device for a power cable.

[Explanation of symbols]

 10 Electrical Stress Relief Device for Power Cable 12 Power Cable 14 Sheath 16 Outer Conductor 18 Insulating Layer 20 Terminal Part 22 Insulator Tube 24 Support Insulator 30 Stress Cone Electrode 34 Stress Cone 36 Reinforced Insulator 38 Metal Reinforced Part 40 Resin Reinforced Part 40a Inner Circumference Taper portion 60 Spring pressing means 62 Stress cone pressure contact member 66 Coil spring 74 Groove 76 Groove 80 Groove

Claims (1)

[Scope of utility model registration request] 1. A stress cone mounted between an insulating layer of a power cable and a reinforcing insulator, and a stress cone pressed between the insulating layer of the power cable and an inner peripheral tapered surface of the reinforcing insulator. In an electrical stress mitigation device for a power cable, comprising: a spring pressing means that compresses and supports between an insulating layer of the power cable and the reinforcing insulator, the stress cone contacts the insulating layer of the power cable. Surface or a contact surface between the stress cone and the tapered inner peripheral surface of the reinforcing insulator, and a groove having an opening at its tip so that an insulating fluid flows thereinto. Mitigation device.