JP3014502B2 - Insulation block for power cable connection and connection method using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in connection technology for a crosslinked polyethylene insulated power cable.

[0002]

2. Description of the Related Art As the application of crosslinked polyethylene insulated power cables to ultrahigh-voltage lines has progressed, reducing the time for connection work has become a major issue in streamlining line construction. In other words, the molding method, which is a technology for connecting crosslinked polyethylene insulated power cables of a voltage class of 154KV or more,
Although stable and high performance can be expected, there is a disadvantage that the time required for the connection work is long.

Recently, a so-called prefabricated joint for assembling insulating parts formed in a factory in advance has been developed and is being put to practical use. However, since the prefabricated joint uses an epoxy resin or rubber, which cannot be used with high electrical stress as crosslinked polyethylene, as a material of the connecting portion insulator, there is a drawback that there is a limit in reducing the size of the connecting portion, For 275KV and 500KV-class tracks, the applicable locations are limited due to space constraints.

[0004] For this reason, as a connection method which combines the high performance of the molding method and the simplicity of the prefabricated joint to a certain extent, a connecting part insulator is manufactured in advance in a factory as a cross-linked insulating block, and it is connected to a cable at the site. A so-called block molding method has been proposed, in which the insulating block and the cable insulator are adhered to each other by applying pressure and heating to the insulating block.

[0005]

PROBLEM TO BE SOLVED: To roughly classify a conventionally proposed cross-linked insulating block into a split-type insulating block 11 shown in FIG. 7 and a tubular insulating block 13 shown in FIG. The split-type insulating block 11 has high electrical stress applied to the bonding interface between the insulating blocks 11 and is therefore difficult to design.In addition, the inner conductive layer of the connection portion flows into the joint of the insulating block 11 and the conductive There was a phenomenon that it became a projection, and it was difficult to take measures to prevent it.

On the other hand, the cylindrical insulating block 13 is inserted through a cable insulator in advance, and the conductor is connected and then pulled back to be set at the cable connection position. The layer must be stripped longer, which increases the overall length of the connection. In addition, since the inner diameter of the insulating block becomes equal to the outer diameter of the cable insulator, the outer diameter of the connecting portion also increases. In order to insert a more rigid tubular insulating block into the cable, it is necessary to provide a clearance between the insulating block and the cable insulator, and this clearance may result in insufficient close contact with the cable insulator. And so on.

[0007]

SUMMARY OF THE INVENTION The present invention provides an insulating block for connecting a crosslinked polyethylene insulated power cable and a connecting method using the same, which have solved the above-mentioned problems.
The insulating block of the present invention is made of a tubular incompletely crosslinked (not reaching a finally reached degree of crosslinking) polyethylene insulator containing an unreacted crosslinking agent, and has an inner diameter connected to the outer diameter of the core of the crosslinked polyethylene insulated power cable. The heat-shrinkability is given by expanding the diameter as described above, and when heat-shrinking, the cross-linked polyethylene insulated power cable is formed into a shape of an insulator at the connection portion. is there.

A method of connecting a crosslinked polyethylene insulated power cable using this insulating block is as follows. First, insert the insulation block into one of the crosslinked polyethylene insulated power cables to be connected. Since the insulating block is enlarged beyond the core outer diameter of the cable (outer semiconductive layer outer diameter), it is not necessary to remove the outer semiconductive layer of the cable for a long time. Therefore, the stripping length of the cable protective layer is longer than before. Shorter.

Next, after the cable conductors are connected, the insulating block is pulled back and set so as to straddle the cables on both sides of the conductor connection portion, and is contracted by heating. The insulation block is heat-shrinkable and is molded to form the insulator shape of the cross-linked polyethylene insulated power cable connection when it shrinks, so the insulation block and the cable insulator, conductor connection And the outer diameter of the connecting portion can be reduced.

Next, the insulating block is cross-linked by heating under pressure. Since the insulating block is made of an incompletely crosslinked polyethylene insulator containing an unreacted crosslinker, when this insulating block is crosslinked, the insulating block softens once and adheres to the cable insulator by pressure, and the progress of the crosslinking proceeds. Adheres firmly to the cable insulator.

The incompletely crosslinked polyethylene insulator containing an unreacted crosslinking agent may be partially crosslinked by chemical crosslinking or may be partially crosslinked by means other than chemical crosslinking such as gamma irradiation. May be used, but it is desirable to use the latter if possible.

If the incompletely crosslinked polyethylene insulator is cut from a power cable which has been subjected to an insulation test using an incompletely crosslinked polyethylene containing an unreacted crosslinking agent as an insulator, the insulation block for connection may be used. The reliability of the insulation performance becomes more reliable.

Further, as the incompletely crosslinked polyethylene insulator, at least one of the inner peripheral surface and the outer peripheral surface thereof has a semiconductive layer cut together with an incompletely crosslinked polyethylene insulator from a power cable having incompletely crosslinked polyethylene as an insulator. It is preferable to use one having By doing so, the operation of forming the inner semiconductive layer or the outer semiconductive layer can be omitted or simplified during the connection operation, and a defect occurs at the interface between the incompletely crosslinked polyethylene insulator and the inner or outer semiconductive layer. Can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In this embodiment, in order to manufacture an insulating block, first, 275 KV, 1400 mm ² (insulation thickness 27 mm, insulator outer diameter 103 mm, outer semi-conductive layer outer diameter 105 mm, inner semi-conductive layer outer diameter
49mm) imperfectly crosslinked polyethylene insulated power cable was manufactured. The degree of incomplete cross-linking was determined by controlling the heating temperature in the cross-linking step to set the average degree of cross-linking to about 65%.

In this state, a predetermined electrical insulation test was performed to confirm that the cable insulator had no internal defects. Then, the cable was cut into a length of 450 mm, and the cable conductor was pulled out to obtain a tubular incompletely crosslinked polyethylene insulator containing an unreacted crosslinker.

This imperfectly crosslinked polyethylene insulator is shown in FIG.
Forming into the shape shown in That is, the inner surface of the incompletely cross-linked polyethylene insulator 21, the inner semiconductive layer 23 of the cable is left at a predetermined length in the center, and cylindrical inner surfaces 25a and 25b are formed at both ends of the inner semiconductive layer 23. Inner surface tapered portions 27a and 27b are formed at both ends.

The inner tapered portions 27a and 27b have the same size as or slightly smaller than the tapered portion formed on the insulator of the cable to be connected. The outer surface of the tubular incompletely cross-linked polyethylene insulator 21 is the outer semiconductive layer of the cable.
29 at a predetermined length, and cylindrical outer surface portions 31a, 31b at both ends thereof.
To form

Next, a cylindrical incompletely cross-linked polyethylene insulator 21 formed and processed as shown in FIG.
Heat to about ° C and expand the diameter by pushing a mandrel with an outer diameter of 110 mm into it. After cooling, pull out the mandrel. Then, an insulating block 33 as shown in FIG. 2 is obtained.

If the heating temperature at the time of expanding the diameter is too high, foaming is caused by the residual methane gas in the insulator, and if the temperature is too low, the insulator is forced to expand when the diameter is expanded by the mandrel and cracks are generated. Is determined in consideration of this point. As described above, the insulating block for connecting a power cable of the present example was manufactured. In this insulating block, the insulator 21 is incompletely crosslinked and has heat shrinkability.

Next, an embodiment of a method for connecting a crosslinked polyethylene insulated power cable using the insulating block 33 will be described with reference to FIG. The used cable is 275KV,
1400mm ² (insulation thickness 27mm, insulator outer diameter 103mm, outer semiconductive layer outer diameter 105mm, inner semiconductive layer outer diameter 49mm) crosslinked polyethylene insulated power cable.

In this connection, first, an end portion of a cable to be connected is stripped to a predetermined length and shape, and necessary components such as an insulating block 33 and a gas barrier layer for cross-linking are inserted through the cable. Next, the cable conductors 41a and 41b are connected by welding to form a welded connection portion 43. After that, the insulating block 33 previously inserted into the cable is pulled back to the center of the connecting portion, and set so as to straddle the cable insulator on both sides of the conductor connecting portion. Next, a heating and shrinking device (not shown)
Is arranged on the outer periphery of the insulating block 33 to be heated and contracted.

Since the inner semiconductive layer 23 is provided integrally with the incompletely cross-linked polyethylene insulator 21 in the insulating block 33, when the insulating block 33 contracts, the inner semiconductive layer 23 is directly used as the inner conductive layer of the connection portion. And the incompletely crosslinked polyethylene insulator 21 becomes an insulating layer of the connection portion. Insulation block
If 33 shrinks, return the semiconductive heat-shrinkable tubes 49a and 49b previously inserted through the cable, and replace the outer semiconductive layer.
It is set so as to cover the space between 29 and the external semiconductive layers 51a and 51b of the cable.

Next, a gas barrier layer for cross-linking, which has been inserted in the cable in advance, is attached to the outer periphery of the connection portion, and the entire connection portion is pressurized and heated using a pressurizing tube to cross-link. Since the insulating block is made of an incompletely crosslinked polyethylene insulator containing an unreacted crosslinker, when this insulating block is crosslinked, the insulating block softens once and adheres to the cable insulator by pressure, and the progress of the crosslinking proceeds. Adheres firmly to the cable insulator. Thereafter, a shielding layer is formed on the outer periphery of the outer semiconductive layer to complete the connection portion of the crosslinked polyethylene insulated power cable.

Next, another embodiment of the present invention will be described. In this example, in order to manufacture an insulating block for connecting a crosslinked polyethylene insulated power cable having an insulation thickness of 27 mm, a power cable having an insulation thickness of 32 mm and containing an unreacted crosslinker as an insulator was manufactured. did. An insulation test was performed on this cable to confirm that the cable insulator had no internal defects. The cable was cut and the cable conductor was pulled out to obtain a tubular uncrosslinked polyethylene insulator containing an unreacted crosslinking agent.

The uncrosslinked polyethylene insulator is formed into a shape as shown in FIG. That is, the inner surface of the uncrosslinked polyethylene insulator 35 is formed by removing the inner semiconductive layer of the cable and fitting the connecting portion inner semiconductive layer formed on the connecting portion of the cable conductor at the center. An inner surface processed portion 36 having an inner diameter slightly smaller than the outer diameter of the inner semiconductive layer is formed.

Next, the inner surface taper portions 27a and 27
Then, cylindrical inner surface portions 37a and 37b having an inner diameter of the insulator outer diameter (103 mm in this case) of the cable connected to both ends thereof are formed. The inner surface taper portion 27
The dimensions a and 27b are the same as or slightly smaller than the tapered portion formed on the insulator of the cable to be connected. Further, the outer surface of the uncrosslinked polyethylene insulator 35 has a predetermined length of the outer semiconductive layer 29 of the cable, and has an outer surface tapered portion at both ends.
38a and 38b are formed.

Thereafter, the uncrosslinked polyethylene insulator 35 is
Incompletely crosslinked by γ-ray irradiation to form an incompletely crosslinked polyethylene insulator 39. At this time, if the dose of γ-rays is excessive, or if the dose rate is too high, the unreacted crosslinking agent in the insulating block is decomposed by γ-rays, while if the dose is too small, the required degree of crosslinking is not obtained, Since the expected shrinkage force cannot be obtained even if the diameter is increased, appropriate conditions need to be selected. For example, crosslinking is performed to a gel fraction of about 60%. Then, the diameter is increased to, for example, 110 mm in inner diameter in the same manner as in the above embodiment, and an insulating block 40 as shown in FIG. 5 is obtained.

Next, another embodiment of a method of connecting a crosslinked polyethylene insulated power cable using the insulating block 40 will be described with reference to FIG. The cable used for the connection is a cross-linked polyethylene insulated power cable of the same size (insulation thickness 27 mm) as in the previous embodiment.

In this connection, first, the end of the cable to be connected is stripped to a predetermined length and shape, and then necessary components such as the insulating block 40 and the gas barrier layer for cross-linking are inserted into the cable. Next, the cable conductors 41a and 41b are connected by welding, and a connection portion inner semiconductive layer 42 is formed on the outer periphery thereof.

Thereafter, the insulating block 40 previously inserted into the cable is pulled back to the center of the connecting portion, and is set so as to straddle the cable insulator on both sides of the conductor connecting portion. Next, a heating and shrinking device (not shown) is disposed on the outer periphery of the device and the insulating block 40 is shrunk by heating. When the insulating block 40 contracts, the incompletely cross-linked polyethylene insulator 39 becomes an insulating layer of a connection portion. At this time, the outer diameter of the connection insulating layer becomes larger than the outer diameter of the cable insulator as shown in the figure. The subsequent connection step and the operation and effect are the same as those in the above embodiment.

In the embodiment described above, the incompletely crosslinked polyethylene insulator 21 containing an unreacted crosslinker or the uncrosslinked polyethylene insulator 35 containing an unreacted crosslinker contains an unreacted crosslinker. Although cut off from power cables with polyethylene as the insulator, these insulators can also be made, for example, by molding. In this case, the polyethylene insulators 21 and 35 containing the unreacted crosslinking agent are incompletely crosslinked by either a crosslinking method by chemical crosslinking or a crosslinking method other than chemical crosslinking by γ-ray irradiation or the like.

The insulating blocks described in the embodiments each have a semiconductive layer on the outer peripheral surface, but the semiconductive layer on the outer peripheral surface can be omitted. In the case of omitting, after the insulating block is thermally contracted, a semiconductive heat-shrinkable tube or the like is put on the outer periphery thereof to form a connection part external semiconductive layer.

[0033]

As is apparent from the above description, the present invention has the following effects. Since the insulating block is made of an incompletely crosslinked polyethylene insulator containing an unreacted crosslinker, when the insulating block is crosslinked, the insulating block softens once and adheres to the cable insulator by pressure, and the crosslink progresses. Adheres tightly to cable insulation. Therefore, it is possible to obtain a stable connection part without quality defects. The insulation block has an inner diameter that is larger than the cable core diameter and is heat-shrinkable, so it can be inserted over the cable core, thus shortening the stripping length of the cable protection layer and reducing the overall length of the connection. The outer diameter of the connection portion can be reduced because the length can be shortened, and heat contraction occurs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state before diameter expansion in a process of manufacturing an insulating block according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an insulating block according to an embodiment of the present invention in which the diameter of the insulating block of FIG. 1 is enlarged.

FIG. 3 is a cross-sectional view showing one embodiment of the connection method of the present invention in which a cross-linked polyethylene insulated power cable is connected using the insulating block of FIG. 2;

FIG. 4 is a cross-sectional view showing a state before diameter expansion in a process of manufacturing an insulating block according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating an insulating block according to another embodiment of the present invention in which the diameter of the insulating block of FIG. 4 is enlarged.

6 is a cross-sectional view showing another embodiment of the connection method of the present invention in which a crosslinked polyethylene insulated power cable is connected using the insulating block of FIG.

FIG. 7 is a perspective view showing a conventional split type power cable connecting insulating block.

FIG. 8 is a perspective view showing a conventional cylindrical power cable connection insulating block.

[Explanation of symbols]

21, 39: Incompletely crosslinked polyethylene insulator 23: Internal semiconductive layer 25a, 25b: Cylindrical inner surface 27a, 27b: Internal taper 29: External semiconductive layer 31a, 31b: Cylindrical outer surface 33, 40: Insulated Block 35: Uncrosslinked polyethylene insulator 36: Inner surface processed part 37a, 37b: Cylindrical inner surface part 38a, 38b: External tapered part 41a, 41b: Cable conductor 42: Connection part semiconductive layer 43: Cable conductor welding connection part 45a , 45b: semiconductive layer 47a, 47b inside the cable
Cable insulator 49a, 49b: semi-conductive heat-shrinkable tube 51a, 51b: outer semi-conductive layer of cable

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Naotaka Ichiyanagi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Kazu Noda 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Inside Electric Industry Co., Ltd. (72) Inventor Nobuyuki Shinagawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) H02G 1/14 H02G 15/08

Claims (5)

(57) [Claims] 1. A tubular incompletely crosslinked polyethylene insulator containing an unreacted crosslinking agent, which is expanded so that its inner diameter is equal to or larger than the outer diameter of the core of the crosslinked polyethylene insulated power cable to be connected. An insulating block for connecting a crosslinked polyethylene insulated power cable, wherein the insulating block is formed so as to have an insulator shape of a crosslinked polyethylene insulated power cable connecting portion when thermally contracted. 2. The insulating block according to claim 1, wherein:
Incompletely crosslinked polyethylene insulator characterized in that it is crosslinked by gamma irradiation. 3. The insulation block according to claim 1, wherein the incompletely crosslinked polyethylene insulator is cut from an insulation-tested power cable using incompletely crosslinked polyethylene containing an unreacted crosslinking agent as an insulator. Characterized by the following. 4. The insulating block according to claim 1, wherein the insulating block has a semiconductive layer on at least one of an inner peripheral surface and an outer peripheral surface thereof, and the semiconductive layer is an incompletely crosslinked polyethylene. Characterized in that it has been cut out from a power cable having an insulative as well as an incompletely crosslinked polyethylene insulator. 5. An insulating block according to claim 1, which is inserted into one of the cross-linked polyethylene insulated power cables connecting the insulating block, and then a cable conductor is connected. Pull back the insulating block and set it so as to straddle the cable insulator on both sides of the conductor connection part. After heating and shrinking the insulating block, pressurize and heat and crosslink to make it adhere to the cable insulator. A method for connecting a crosslinked polyethylene insulated power cable, characterized in that: