JP6712990B2 - Termination connection for power cable - Google Patents

Description

The present invention relates to a power cable terminating terminal having an electric insulation layer formed of plastic such as cross-linked polyethylene.

At the terminal connection part of the power cable, there is one in which a stress cone formed of a synthetic elastomer on the power cable and a cylindrical insulating tube are attached and an insulating mixture is injected.

As a specific structure of the terminal connecting portion of the power cable, for example, an FRP cylinder, a polymer coating having a large number of umbrella portions integrally formed on the outer periphery of the FRP cylinder, and a top end of the FRP cylinder are attached. In a polymer porcelain tube for a power cable terminating connection, which comprises an upper metal fitting and a flange fixed to the FRP cylinder, an extension part extending below the flange is provided in the FRP cylinder, and a lower metal fitting is provided at a lower end of the extension part. Is disclosed, and a second polymer coating is formed on the outer periphery of the extension part of the FRP cylinder to electrically insulate the flange and the lower metal fitting, and a power cable terminal connection part is disclosed (Patent Document 1).

In Patent Document 1, a stress cone is attached from the outer semiconductive layer to the cable insulating layer in order to reduce electric field stress. In the stress cone of Patent Document 1, the insulator has a cylindrical shape having a substantially uniform diameter.

On the other hand, the terminal connection portion of the power cable may be required to have impulse withstand voltage characteristics, for example, because it is required to have resistance to lightning strikes. Impulse withstand voltage characteristics are required to have higher performance as power cables become ultra-high voltage. In the stress cone of Patent Document 1 in which the insulator has a cylindrical shape having a substantially uniform diameter, the impulse withstand voltage characteristic can be improved by increasing the size of the stress cone. However, from the viewpoint of cost and handleability, there is a limit to the improvement of the impulse withstand voltage characteristic, so that the stress cone of Patent Document 1 has room for improvement in the impulse withstand voltage characteristic.

JP, 2008-27828, A

In view of the above circumstances, an object of the present invention is to provide a power cable terminal connection part that can improve impulse withstand voltage characteristics in the power cable terminal connection part and can also cope with ultra high voltage of the power cable. To do.

It has been found that the present invention improves impulse withstand voltage characteristics by forming a taper portion having a predetermined angle on the high voltage front end side of the stress cone, and can cope with ultra high voltage of the power cable.

That is, the gist of the present invention is as follows.
[1] A stress cone integrally molded with an insulator part and a semiconductive part,
The insulator portion, between the high voltage side tip portion and the large diameter portion, the angle of the stress cone on the high voltage tip side with respect to the axis of the power cable is greater than the angle of the electric field direction at the high voltage side tip portion of the stress cone. Also has a taper that is smaller,
In connection with the terminal portion of the power cable, the power cone terminal connection portion in which the stress cone is mounted on an insulator of the power cable.
[2] The power cable termination connection part according to [1], wherein the thickness of the high-pressure side tip of the stress cone is 2.0 mm or less.
[3] The power cable terminating connection part according to [1], wherein the high-pressure side tip of the stress cone has a thickness of 1.0 mm or less.
[4] The power cable terminal connecting portion according to any one of [1] to [3], wherein an angle of the taper portion of the stress cone with respect to an axis of the power cable is 65° or less.
[5] The power cable termination connection part according to any one of [1] to [3], wherein an angle of the taper part of the stress cone with respect to the axis of the power cable is 45° or more.
[6] The power cable termination connection part according to any one of [1] to [5], wherein the stress cone is formed of a synthetic elastomer.
[7] The power cable termination connection part according to any one of [1] to [6], wherein the power cable is for AC power transmission.
[8] Relative permittivity of the insulator portion of the stress cone with respect to vacuum at 25° C. (hereinafter, referred to as “relative permittivity” unless otherwise specified): 25 of the insulating medium enclosed in the terminal portion of the power cable. The terminal connection part for power cables according to any one of [1] to [7], which has a relative dielectric constant of 1.0.25 to 1:1.5.

According to the aspect of the present invention, the angle of the stress cone on the high-voltage front end side with respect to the axis of the power cable has a tapered portion that is smaller than the angle of the stress cone on the high-voltage side front end in the electric field direction. In addition, it is possible to improve the impulse withstand voltage characteristic at the terminal connection portion of the power cable, and further to obtain the terminal connection portion for the power cable which can cope with the super high voltage of the power cable.

According to the aspect of the present invention, the thickness of the high pressure side tip of the stress cone is 2.0 mm or less, so that the impulse withstand voltage characteristics can be further improved.

According to the aspect of the present invention, the angle of the tapered portion of the stress cone with respect to the axis of the power cable is 65° or less, so that the impulse withstand voltage characteristic can be further improved.

According to the aspect of the present invention, since the angle of the tapered portion of the stress cone with respect to the axis of the power cable is 45° or more, the workability of mounting the stress cone can be improved.

It is sectional drawing of the right half which shows the state which attached the termination|terminus connection part for electric power cables which concerns on the example of embodiment of this invention to the electric power cable. It is sectional drawing of the upper half which shows the example of embodiment of the stress cone applied to the terminal connection part for electric power cables which concerns on the example of embodiment of this invention of FIG. It is an equipotential diagram of the stress cone area|region applied to the termination connection part for electric power cables which concerns on the example of embodiment of this invention. It is an equipotential diagram of the stress cone area|region which was applied to the conventional termination connection part for electric power cables.

Hereinafter, a power cable termination connection portion according to an embodiment of the present invention will be described with reference to the drawings.

First, a power cable termination connecting portion 1 according to an embodiment of the present invention will be described with reference to FIG. The power cable terminating connection part 1 includes an insulating porcelain tube 10 having an insulating property, a stress cone 12 arranged on the stepped power cable terminal portion 11, and a lower (low pressure side) opening of the insulating porcelain tube 10. A first sealing member 13 for sealing and a second sealing member 14 for sealing the upper (high pressure side) opening of the insulating porcelain tube 10 are provided. The power cable terminal portion 11 provided with the stress cone 12 is covered with the insulating porcelain tube 10, the first sealing member 13 and the second sealing member 14, and the insulating medium 15 is enclosed inside the insulating porcelain tube 10. It has an insulating structure.

The porcelain insulator 10 includes a porcelain insulator main body 10-1 and a plurality of pleats 10-2, 10-2, 10-2,... Formed at regular intervals on the outer surface of the porcelain insulator main body 10-1. Prepare The material of the insulating porcelain tube 10 is not particularly limited as long as it is an insulating material, and examples thereof include ceramics, rubber, plastics such as fiber reinforced plastics, and the like.

The power cable 16 may be an AC power cable or a DC power cable. In the power cable terminal portion 11, the conductor 16-1, the cable insulator 16-2, the outer semiconductive layer 16-3, and the shielding layer 16-4 are exposed from the cable sheath 16-5 by the step stripping process. Examples of the material of the cable insulator 16-2 include plastics such as cross-linked polyethylene.

Next, with reference to FIG. 2, an exemplary embodiment of the stress cone 12 applied to the power cable terminating connection portion 1 according to the exemplary embodiment of the present invention will be described. The stress cone 12 has an insulator part 21 and a semiconductive part 22 integrally molded with the insulator part 21. The stress cone is arranged so that the insulator part 21 is arranged on the cable insulator 16-2 of the power cable terminal part 11 and the semiconductive part 22 is arranged on the outer semiconductive layer 16-3 of the power cable terminal part 11. 12 is attached to the power cable terminal 11.

The insulator portion 21 has a high pressure side tip portion 23 which is a small diameter portion, a large diameter portion 25 having a diameter larger than that of the high pressure side tip portion 23, and a low pressure side base portion 26. The high voltage side tip portion 23 forms one end of the insulator portion 21, and the low voltage side base portion 26 forms the other end of the insulator portion 21. A large-diameter portion 25 is provided between the high-pressure side tip portion 23 and the low-pressure side base portion 26.

Further, between the high pressure side tip portion 23 and the large diameter portion 25, a taper portion 24 is formed that widens from the high pressure side tip portion 23 toward the large diameter portion 25. The surface of the taper portion 24 has a predetermined angle α with respect to the axial direction X of the power cable 16, that is, the longitudinal direction X of the power cable 16. The angle α corresponds to the angle between the longitudinal direction X of the power cable 16 and the surface of the tapered portion 24 at the high voltage side tip portion 23.

The angle α is smaller than the angle in the electric field direction at the high voltage side tip portion 23 of the stress cone 12. The electric field direction at the high voltage side tip portion 23 can be measured by performing analysis by the finite element method using analysis software mechanical APDL manufactured by ANSYS. The results of analysis by the finite element method are shown in FIGS. FIG. 3 is an equipotential diagram in the region of the stress cone 12 according to the embodiment of the present invention, and FIG. 4 is an equipotential diagram in the region of the conventional stress cone. The electric field direction is orthogonal to the equipotential lines. Further, in FIGS. 3 and 4, the ratio of the relative permittivity of the material of the insulator portion 21 of the stress cone 12 at 25° C. to the relative permittivity of the insulating medium 15 sealed at the end portion of the power cable 16 at 25° C. The analysis was performed using a material having a value of about 0.8.

From FIGS. 3 and 4, it was confirmed that the angle of the electric field direction at the high voltage side tip portion 23 (the direction of the red arrow in FIGS. 3 and 4) was about 80° with respect to the longitudinal direction X of the power cable 16. .. Therefore, the angle α at the high voltage side tip portion 23 is smaller than about 80° which is the angle in the electric field direction with respect to the longitudinal direction X of the power cable 16. 3 and 4, the ratio of the relative permittivity at 25° C. of the material of the insulator portion 21 of the stress cone 12 to the relative permittivity at 25° C. of the insulating medium 15 sealed in the end portion of the power cable 16 is: Although a material of about 0.8 was used, the angle of the electric field direction at the high voltage side tip portion is the same as that of the commonly used material of the insulator portion 21 and the insulating medium 15. Is about 80° with respect to the longitudinal direction.

Since the angle α is smaller than the angle in the electric field direction at the high voltage side tip portion 23 of the stress cone 12, the impulse withstand voltage characteristic can be improved at the terminal connection portion of the power cable 16, and It is possible to obtain the power cable terminating connection portion 1 capable of coping with the super high voltage of the power cable 16. One of the reasons for the above effect is that the presence of the stress cone 12 can be avoided in the electric field direction at the high voltage side tip portion 23, which makes it difficult for the electric field vector due to the high potential difference to pass through the stress cone. Presumed to be

The angle α is not particularly limited as long as it is smaller than the angle (about 80°) in the electric field direction at the high voltage side tip portion 23 of the stress cone 12, and the upper limit of the angle α further improves the impulse withstand voltage characteristics. From the point of view, 75° is preferable, 65° is more preferable, and 60° is particularly preferable. Further, the lower limit value of the angle α is preferably 45°, and particularly preferably 50°, from the viewpoint that the traction workability and the mechanical strength at the time of mounting the stress cone 12 are improved while further improving the impulse withstand voltage characteristics.

The thickness t of the high pressure side tip portion 23 of the stress cone 12 is not particularly limited, and its upper limit value is preferably 2.0 mm, more preferably 1.5 mm, from the viewpoint of further improving impulse withstand voltage characteristics. 0.0 mm is particularly preferable. The reason why the impulse withstand voltage characteristic is further improved by reducing the thickness t of the high voltage side tip portion 23 as described above is that the existence of the stress cone 12 is more reliably avoided in the electric field direction at the high voltage side tip portion 23. Therefore, it is presumed that one of the causes is that the electric field vector caused by the high potential difference is more difficult to pass through the stress cone.

On the other hand, the lower limit value of the thickness t of the high pressure side tip portion 23 is preferably 0.5 mm, and particularly preferably 1.0 mm, from the viewpoint of ease of manufacturing the stress cone 12.

The material of the insulator portion 21 is not particularly limited as long as it can be generally used, and examples thereof include synthetic elastomers. Examples of synthetic elastomers include ethylene propylene diene rubber and silicone rubber. Relative permittivity of the material of the insulator 21 of the stress cone 12 at 25° C.: The ratio of the relative permittivity of the insulating medium 15 sealed at the end of the power cable 16 at 25° C. From the point of contributing to making it difficult to pass through the stress cone, 1:0.25 to 1:1.5 are preferable, and 1:0.6 to 1:1.2 are particularly preferable. Examples of the combination of the material of the insulating portion 21 and the insulating medium 15 which satisfy the above ratio include a combination of ethylene propylene diene rubber and silicone oil.

Next, examples of the present invention will be described, but the present invention is not limited to these examples unless the gist thereof is exceeded.

First, a step of stripping the end portion of the power cable was performed to expose the conductor, the cable insulator, the outer semiconductive layer, and the shielding layer from the cable sheath. Next, a conductor extraction rod was connected to the conductor by compression or the like. Next, a stress cone was attached so that the insulator part was located on the cable insulator exposed from the cable sheath of the power cable terminal part and the semiconductive part was located on the outer semiconductive layer exposed from the cable sheath. .. Ethylene propylene diene rubber was used as the material for the stress cone. Table 1 below shows the thickness t of the high-pressure side tip of the mounted stress cone and the angle α of the tapered portion with respect to the longitudinal direction of the power cable.

Next, the stepped-off power cable end is covered with an insulating porcelain tube, the lower opening of the insulating porcelain tube is sealed with a first sealing member, and the upper opening of the insulating porcelain tube is sealed with a second sealing member. It was stopped and shielded. Silicone oil as an insulating medium was sealed inside the insulating porcelain tube to prepare a power cable termination connection. In addition, as a result of measurement by performing analysis by the finite element method using the analysis software mechanical APDL of ANSYS, the angle of the electric field direction at the high voltage side tip is 80° with respect to the longitudinal direction X of the power cable. there were.

A lightning impulse resistance test was performed on the power cable termination connection part manufactured as described above. The lightning impulse resistance test was carried out in accordance with JEC-0202-1994 (impulse voltage/current test general) which is a standard of the Institute of Electrical Engineers of Japan, Electrical Standards Study Group. The lightning impulse resistance test is shown in Table 1 below. In the lightning impulse resistance test, relative evaluation was performed with the breakdown voltage of Comparative Example 1 in which the thickness t of the insulator portion was 20 mm without providing the tapered portion (that is, the angle α was 0°) was 100%. In addition, the triple point of the broken portion in Table 1 below means a portion where the insulating porcelain tube, the cable insulator, and the stress cone overlap in the radial direction of the power cable termination connection portion.

As shown in Table 1, in Examples 1 to 3 which are the power cable termination connection parts equipped with the stress cone having the taper portion having an angle smaller than 80° in the direction of the electric field, the breakdown voltage is 124% or 130%. It has been found that even if the voltage exceeds 100%, it is not destroyed and excellent lightning impulse immunity is obtained, and it is also possible to cope with ultra high voltage power cables. As described above, in Examples 1 to 3, since the lightning impulse resistance was not destroyed even when the breakdown voltage was 124% or 130% or more, it was found that the impulse withstand voltage characteristics were excellent. Particularly, in Examples 2 and 3 in which the thickness t of the high pressure side tip portion of the stress cone was 1 mm, it was not destroyed even at a voltage of 130% or more, and more excellent lightning impulse resistance was obtained.

On the other hand, in the comparative examples 1 and 2 in which the stress cone without the tapered portion was mounted and in the comparative examples 3 and 4 in which the stress cone having the tapered portion having an angle of 80° in the electric field direction was mounted, Of 100 to 115% was obtained, and high lightning impulse resistance was not obtained.

1 Power Cable Termination Connection Part 12 Stress Cone 21 Insulator Part 23 High Voltage Side Tip Part 24 Tapered Part 25 Large Diameter Part

Claims (6)

A stress cone integrally molded with an insulator part and a semiconductive part,
The insulator portion, between the high voltage side tip portion and the large diameter portion, the angle of the stress cone on the high voltage tip side with respect to the axis of the power cable is greater than the angle of the electric field direction at the high voltage side tip portion of the stress cone. Also has a taper that is smaller,
The angle of the taper portion of the stress cone with respect to the axis of the power cable is 45° or more and 65° or less,
In connection with the terminal portion of the power cable, the power cone terminal connection portion in which the stress cone is mounted on an insulator of the power cable. The power cable termination connection part according to claim 1, wherein a thickness of a high voltage side tip part of the stress cone is 2.0 mm or less. The power cable terminal connection portion according to claim 1, wherein a thickness of a high pressure side tip portion of the stress cone is 1.0 mm or less. The power cable termination connection according to any one of claims 1 to 3 , wherein the stress cone is formed of a synthetic elastomer. Wherein the power cable, power cable sealing end according to any one of claims 1 to 4 is for AC transmission. The dielectric constant of the insulator portion of the stress cone at 25° C.: The dielectric constant of the insulating medium sealed at the end portion of the power cable at 25° C. is 1:0.25 to 1:1.5. Item 9. A power cable termination connection part according to any one of items 1 to 5 .