JPH0923562A - Electric field relaxation tube - Google Patents

Abstract

(57) Abstract: To provide an electric field relaxation tube used for a power cable termination connection part capable of reliably suppressing the occurrence of partial discharge. A semiconductive layer 12 is formed or a conductive paint is applied to the inner surface of an electric field relaxation tube 11 made of a high-dielectric material whose diameter can be expanded. Then, the electric field relaxation tube 11 is inserted so that the semiconductive layer 12 or the semiconductive coating material contacts the semiconductive layer 3 of the stripped power cable and the cable insulator 4. Since the semiconductive layer 12 is formed on the inner surface of the electric field relaxation tube 11 or the conductive paint is applied, it is possible to improve the adhesion between the electric field relaxation tube formed of a high dielectric material and the stepped portion of the cable. It is possible to suppress the generation of voids and effectively suppress the generation of partial discharge when a voltage is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field relaxation tube used for a tube-type terminal connection portion of a rubber or plastic power cable.

[0002]

2. Description of the Related Art At the terminal end of a power cable of 6600 V or more, an electric field is concentrated on the tip of the shield layer when the copper tape of the shield layer is cut, which causes dielectric breakdown. Therefore, an electric field relaxation tube made of a high dielectric material is attached to the shielded copper tape cutting portion to distribute the electric field in the longitudinal direction of the tube to relax the electric field.

Therefore, conventionally, the following method has been conventionally adopted. After applying and drying conductive paint on the end of the cable semi-conductive layer of the cable step stripping part consisting of sheath, shielding layer copper tape, cable semi-conductive layer, insulator, conductor,
A heat-shrinkable electric field relaxation tube made only of a high-dielectric material is covered up to the tip of the shielding layer copper tape to shrink it, and the electric field is relaxed at the end of the cable (as a similar technique, see, for example, JP-A-60-501039). (See the official gazette).

The present inventors have examined using a self-shrinking electric field relaxation tube instead of the heat-shrinkable tube in order to improve the workability of the electric field relaxation treatment.
FIG. 4 is a diagram showing a case where electric field relaxation is performed using this method. FIG. 4A shows a state before insertion of the electric field relaxation tube, and FIG. 4B shows a partial cross-sectional view after insertion of the tube. There is.

In the figure, 1 is a cable sheath, 2 is a shield layer, 3 is a cable semi-conductive layer, 4 is a cable insulator, and 5 is an electric field relaxation tube formed of a high dielectric material such as a silicon tube. To alleviate the electric field at the cable terminating portion, first, as shown in FIG. 3A, the cable terminating portion is first provided with a cable sheath 1, a copper tape of a shielding layer 2, a cable semiconductive layer 3, a cable insulator 4, and a conductor. After stripping off (not shown), a conductive paint 6 is applied from the cable semi-conductive layer 3 to the cable insulator 5 and dried. The conductive paint 6 is applied to prevent discharge from the end of the cable semiconductive layer 3.

Next, the electric field relaxation tube 5 is attached to the same figure (b).
Insert the shielding layer 2 up to the tip of the copper tape as shown in FIG.

[0007]

In the case of the method shown in FIG. 4, there is a gap between the tip of the conductive paint 6 on the cable insulator and the electric field relaxation tube as shown by A in FIG. It was found that voids were generated in the inner part, and this deteriorated the partial discharge characteristics. It is considered that this is because the silicon tube itself has a small tightening stress, so that a gap is formed between the end portion of the conductive paint and the electric field relaxation tube, resulting in partial discharge. By the way, by increasing the tightening stress at the end of the conductive paint by winding a tape around the surface of the electric field relaxation tube, the void can be eliminated and the occurrence of partial discharge can be suppressed.

The known example described above (Japanese Patent Laid-Open No. 50103/1985)
In Japanese Patent Laid-Open No. 9), the tube can be shrunk by heat to increase the tightening stress. Therefore, it is considered that the void at the tip of the conductive paint is eliminated and the occurrence of partial discharge is suppressed. However, in the case of using the self-shrinkable tube examined by the present inventors, the void cannot be eliminated even if the tube is shrunk, and the occurrence of partial discharge cannot be completely suppressed.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and does not wind the tape over the tube or shrink the tube by heat.
It is an object of the present invention to provide an electric field relaxation tube used for a power cable termination connection portion that can reliably suppress the occurrence of partial discharge due to the voids described above.

[0010]

In order to solve the above-mentioned problems, in the invention of claim 1 of the present invention, in the electric field relaxation tube attached to the terminal connection portion of the stripped power cable, the electric field relaxation tube is The inner surface of the tube body is formed of a high-dielectric material that can expand its diameter, and at the same time, the inner surface of the tube is formed with a semi-conductive layer at least in the range from the part that contacts the cable semi-conductive layer of the power cable to the part that contacts the insulator And the inner surface of the portion where the semiconductive layer is formed are substantially flush with each other.

According to a second aspect of the present invention, in the electric field relaxation tube attached to the terminal connection portion of the stripped power cable, the electric field relaxation tube is made of a high-dielectric material capable of expanding its diameter, and the inner surface of the tube is formed. Of the electric power cable, the conductive paint is applied at least in the range from the portion in contact with the cable semi-conductive layer to the portion in contact with the insulator.

[0012]

FIG. 1 is a view showing a case where the electric field relaxation tube of the present invention is used to alleviate an electric field at a cable end connection portion,
The figure (a) shows the state before the electric field relaxation tube is attached,
(B) shows a partial cross-sectional view after the tube is attached. In FIG. 1, the same parts as those shown in FIG. 4 are designated by the same reference numerals, 1 is a cable sheath, 2 is a copper tape of a shielding layer, 3 is a semiconductive layer of the cable, and 4 is a cable insulation. It is the body. Reference numeral 11 denotes an electric field relaxation tube according to the present invention, and a semiconductive layer 12 is formed (or a conductive paint is applied) on the inner surface of the electric field relaxation tube 11 as shown in FIG.

As shown in FIG. 2B, when the electric field relaxation tube 11 of the present invention is inserted into the cable end portion, the end of the semiconductive layer 12 is the cable insulator 4 as shown in FIG.
It does not cause voids even if the tube tightening force is small. Therefore, as described above, it is possible to suppress the occurrence of partial discharge when a voltage is applied, without increasing the tightening stress such as winding the tape over the tube. Even if voids occur in the portions C and D in the same figure, the electric field is relieved by the semiconductive layer 12, so there is no problem in performance.

Further, when conductive paint is applied to the inner surface of the electric field relaxation tube, it is considered that a slight void is generated in the B portion in the B portion of FIG. 1 (b) by the thickness of the conductive paint. Since the end of the conductive paint is formed smoothly and the conductive paint is in close contact with the electric field relaxation tube, the conductive paint also expands and contracts according to the expansion and contraction of the electric field relaxation tube, and the cable insulation at the above-mentioned part B It is thought that it has good adhesion to the body and is less likely to cause voids.

In order to confirm the above effect of the present invention, a partial discharge test was carried out by inserting an electric field relaxation tube having an inner surface of the present invention coated with a conductive paint at the end of the cable. In this test, conductive paint was applied to the inner surface of a high-dielectric expansion tube made of silicon rubber to a thickness of about 30 mm, and inserted into a 6600 V class cable stripped off as shown in FIG. The partial discharge characteristics were investigated. In addition, the partial discharge characteristics were examined also in the case where the conductive paint was applied to the cable side as shown in FIG.

As a result, the partial discharge characteristic when the electric field relaxation tube of the present invention was inserted was 6.9 kV / 10 pc, whereas the partial discharge characteristic in the case of FIG. 4 was 14 kV /
It was 5 pc, and the electric field relaxation tube effect of the present invention was confirmed. Since the adhesion between the cable insulator and the electric field relaxation tube is higher when the semiconductive layer is provided than when the conductive paint is applied to the inner surface of the tube, the same applies when the semiconductive layer is provided. It is considered that the above effects can be obtained. Further, the thickness of the semi-conductive layer may be the same as the thickness of the conductive paint applied.

As described above, according to the first and second aspects of the present invention, the electric field relaxation tube is formed of a high-dielectric material capable of expanding the diameter, and contacts the semiconductive layer and the insulator of the power cable. Since a semi-conductive layer is formed on the inner surface of the tube body or conductive paint is applied, it is possible to improve the adhesion between the electric field relaxation tube made of a high dielectric material and the stepped part of the cable, and the occurrence of voids. It is possible to effectively suppress the occurrence of partial discharge when a voltage is applied.

[0018]

2 is a view showing an electric field relaxation tube according to an embodiment of the present invention, 11 is an electric field relaxation tube, 1
Reference numeral 2 denotes a semiconductive layer provided on the inner surface of the electric field relaxation tube 11 or a conductive paint applied. The electric field relaxation tube 11 is made of high dielectric silicon rubber or the like having a conductivity ρ of 10 ⁹ to 10 ^{10 and has} an inner surface on one side (semiconductor layer of cable,
A semiconductive layer having a conductivity ρ of 10 ⁵ or less is formed in the longitudinal direction of the (shielding layer side).

FIG. 3 is a view showing the structure of the power cable termination portion in which the electric field relaxation tube of this embodiment is inserted. In FIG. 3, 1 is a cable sheath, 2 is a shielding layer, 3 is a cable semiconductive layer, 4 is a cable insulator and 7 is a cable conductor. Further, 11 is an electric field relaxation tube according to this embodiment shown in FIG. 2, 13 is a ground wire, 20 is a terminal body,
Reference numeral 21 is a terminal, 22 is a rain cover, and 23 is a grounding spring.

The power cable termination shown in FIG. 3 is formed as follows. First, the end portion of the power cable is stripped off to an arbitrary size from the cable sheath 1, the shield layer 2, the cable semiconductive layer 3, the insulator 4, and the cable conductor 7, and the ground wire 13 is placed along the shield layer 2 and grounded. Spring 2
At 3, the ground wire 13 is attached to the copper tape of the shield layer 2.

Then, after applying a lubricant on the cable insulator 4, the electric field relaxation tube 11 of this embodiment is inserted up to the tip of the shielding layer. Next, connect the cable conductor 7 to the terminal 2
1 is inserted, pressure-bonded or compression-connected, and the terminal body (tube-shaped end portion) 20 is inserted. Then, the rain cover 22 is inserted at an arbitrary position to complete the process.

[0022]

As described above, according to the present invention, in the electric field relaxation tube attached to the termination connection portion of the stripped power cable, the electric field relaxation tube is formed of a high dielectric material capable of expanding the diameter. Since the semiconductive layer is formed on the inner surface of the tube body which is in contact with the semiconductive layer of the power cable and the insulator, or the conductive paint is applied, the following effects can be obtained. (1) It is possible to improve the adhesion between the electric field relaxation tube formed of a high dielectric material and the stepped portion of the cable, and to suppress the generation of voids that cause partial discharge and prevent the occurrence of partial discharge when a voltage is applied. It can be effectively suppressed. Therefore, it is possible to maintain the electrical performance of the cable itself and the terminal end. (2) Since a semi-conductive layer is formed on the electric field relaxation tube or conductive paint is applied, it is not necessary to apply and dry conductive paint on the stripped portion of the cable as in the conventional case, and the power cable terminal end can be easily and quickly Can be assembled.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which an electric field relaxation tube of the present invention is attached to a cable end portion.

FIG. 2 is a diagram showing a configuration of an electric field relaxation tube according to an example of the present invention.

FIG. 3 is a diagram showing a configuration of a cable terminal portion using the electric field relaxation tube of FIG.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 cable sheath 2 shield layer 3 cable semi-conductive layer 4 cable insulator 5 electric field relaxation tube 6 conductive paint 11 electric field relaxation tube 12 semiconductive layer 13 ground wire 20 terminal body 21 terminal 22 rain cover 23 ground spring 23

Claims (2)

[Claims] 1. An electric field relaxation tube attached to a terminal connection portion of a stripped power cable, wherein the field relaxation tube is formed of a high-dielectric material capable of expanding the diameter, and at least the cable half of the power cable on the inner surface of the tube. A semi-conductive layer is formed in the range from the part in contact with the conductive layer to the part in contact with the insulator, and the inner surface of the tube body and the inner surface of the part where the semi-conductive layer is formed are substantially flush with each other. And electric field relaxation tube. 2. An electric field relaxation tube attached to a terminal connection portion of a stripped power cable, wherein the electric field relaxation tube is formed of a high-dielectric material capable of expanding the diameter, and at least the cable half of the power cable on the inner surface of the tube. An electric field relaxation tube characterized in that a conductive paint is applied in a range from a portion in contact with a conductive layer to a portion in contact with an insulator.