JP2000164046A - Power cable and its laying method - Google Patents

Abstract

(57) [Summary] To provide a power cable suitable for long-distance power transmission with high capacity. SOLUTION: Using a power cable composed of a cross-linked cable section 1 in which an insulating layer and a semiconductive layer are cross-linked, and a non-cross-linked cable section 2 which is not cross-linked, the entire non-cross-linked cable section 2 is made of water. It is laid on the seabed etc. so that it touches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power cable,
In particular, the present invention relates to a DC cable suitable for a submarine cable and the like and a method for laying the DC cable.

[0002]

2. Description of the Related Art As an insulation layer of a DC cable, an oil-immersion paper insulation type and a plastic insulation type are known, and typical insulation layers used for the plastic insulation type cable are shown. As the resin, there is polyethylene. Cables using polyethylene as the insulating layer include those in which the insulating layer is not crosslinked and those in which the heat resistance is improved by crosslinking the insulating layer.

[0003] However, at the time of producing this cross-linked type cable, there is a problem of scorch due to stagnation of the material used for the insulating layer and the like in the extruder, so that it is difficult to lengthen the cross-linked type cable. Generally, since the laying distance of a DC cable extends over several tens of kilometers,
Very long ones are desired. Therefore, at present, it is difficult to manufacture a bridge type cable for a long distance DC cable.

On the other hand, with conventional non-crosslinked type cables, there is no particular problem in manufacturing long cables,
Since the heat resistance is slightly inferior to the crosslinked product, there is a disadvantage that it cannot be used for high capacity power transmission.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power cable for long-distance, high-capacity power transmission, particularly a DC cable suitable for a submarine cable, and a method of laying the same.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power cable comprising a crosslinked cable portion in which an insulating layer and a semiconductive layer are crosslinked, and a non-crosslinked cable portion in which the insulating layer and the semiconductive layer are not crosslinked. The problem can be solved by laying all of the non-bridged cable portion and at least a part of the bridged cable portion in water. Further, the power cable of the present invention preferably has a bridged cable portion at both ends of the non-bridged cable portion.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A submarine DC cable according to an embodiment of the present invention and a method of laying the same will be described as an example, and will be described in detail below with reference to the drawings. However, the present invention is not limited to these. Absent. Accordingly, the following description is generally applicable to power cables unless otherwise noted.

FIG. 1 shows an example of the configuration of a power cable according to the present invention. Both ends of this cable are a cross-linked cable 1 using a cross-linked resin as a material of the insulating layer and the semiconductive layer, while an intermediate portion sandwiched between the cross-linked cables 1 And a non-crosslinked cable portion 2 using a non-crosslinked resin as a material of the semiconductive layer.

FIG. 2 shows a cross section of the cable of FIG. In this cable, reference numeral 3 is a conductor, and reference numeral 4,
Reference numerals 5 and 6 denote an inner semiconductive layer, an insulating layer, and an outer semiconductive layer which are sequentially disposed on the outer periphery of the conductor 3, and these are covered with a shielding layer 7. This shielding layer 7 is covered with a sheath 8 on the outer peripheral surface.

FIG. 3 shows another embodiment of the cable according to the present invention. In this cable, the intermediate portion of the non-crosslinked cable portion 2 of the cable illustrated in FIG.
In the form linked by The joint has a prefabricated connection (PJ), a tape-wound connection (TJ), and a molded connection (TMJ, EM) of the same diameter and quasi-same diameter.
J) can be used.

FIG. 4 is a diagram showing an example of a laying state of a power cable according to the laying method of the present invention. In this example, both end portions of the cable are bridged cable portions 1;
In each of the bridged cable portions 1 at both ends of the cable, at least a part of the bridged cable portion is laid below the water surface. On the other hand, the non-cross-linked cable portion 2 sandwiched between the two cross-linked cable portions 1 is entirely under water,
It is laid so that its surface is always in contact with water.
Therefore, in the non-crosslinked cable section 2, the cable section is always cooled by water. According to such laying of the power cable, high-capacity long-distance power transmission using a cable having a non-bridged cable portion is possible.

As a material used for the insulating layer of the power cable, various resins used conventionally can be used. For example, there are polyvinyl chloride, polyethylene, ethylene-propylene copolymer, silicone rubber, fluororesin, etc. Among them, polyethylene is typical, and polyethylene is a preferred resin used for the cable.

There are low density and high density polyethylenes, but any of them may be used for the cable of the present invention. For a DC cable, polyethylene grafted with maleic anhydride or polyethylene blended with carbon or an oxide such as magnesium oxide or calcium oxide can be used.

Various cross-linking agents can be used for cross-linking the insulation layer of the power cable. It is preferable to select in consideration of the influence. Examples of crosslinking agents that can be used to crosslink the insulating layer of the cable of the present invention include DCP (dicumyl peroxide), APO (2,5 dimethyl-2,5-di (t-butylperoxy) hexane) , YPO (2,5-dimethyl-2,5-di- (t-
Butylperoxy) hexyne-3).

The crosslinking may be silane crosslinking. In a thick cable, the degree of cross-linking due to moisture penetration is unlikely to increase. In this case, it is preferable to use a silane-grafted resin rather than a resin grafted during extrusion. Alternatively, a resin to which a silane coupling agent and a small amount of an organic peroxide (such as DCP) are added may be used.

As the silane coupling agent, vinyl trimethoxy silane, vinyl triethoxy silane, or the like can be used.

The resin used for the semiconductive layer of the power cable is not particularly limited, but examples thereof include ethylene-vinyl acetate copolymer (EVA), ethylene ethyl acrylate (EEA), Ethylene butyl acrylate (EBA), polyethylene, and mixtures thereof
Examples thereof include compounds containing a conductive powder such as Bon Black or an inorganic filler. In addition, TAC, TAI
A crosslinking aid such as C may be added.

The cross-linking agent used for cross-linking the semiconductive layer is basically the same as the above-mentioned cross-linking for the insulating layer.
It is preferable to select the cable according to the purpose of use and the manufacturing method.

The layers other than the insulating layer and the semiconductive layer described above are not particularly limited, but may be any according to the purpose of use. When heat resistance is required in layers other than the insulating layer and the semi-motorized layer, a cross-linking treatment may be performed as in the case of the insulating layer or the like to improve the heat resistance or the like.

Next, a method of manufacturing the cable shown in FIG. 1 will be described. For this production method, an extrusion coating method is preferably used. In this manufacturing method, the inner semiconductive layer 4, the insulating layer 5, and the outer semiconductive layer 6 are sequentially coated around the conductor 3. In order to maintain the adhesion between the semiconductive layer and the insulating layer, the extruder corresponding to each layer is arranged in tandem to perform continuous extrusion coating, or simultaneously extrude each layer onto the conductor 3 using a crosshead die. Is preferred.

First, a portion corresponding to the crosslinked cable portion 1 requiring heat resistance is prepared. The above-mentioned cross-linking agent is appropriately blended with a material such as a resin used for the insulating layer and the semiconductive layer of the portion corresponding to the cross-linked cable portion 1 and supplied to an extruder. Is adjusted by coating. At this stage, since the cross-linking step has not been obtained, the portion of the insulating layer and the like corresponding to the cross-linked cable portion 1 is not cross-linked. When a cable having a desired length is obtained, the blending of the crosslinking agent into the materials for the insulating layer and the semiconductive layer is stopped, and then the non-crosslinked cable portion 2 is formed. In preparing the non-crosslinked cable portion 2, except that the crosslinking agent is not blended,
May be performed in the same manner as the creation of the portion corresponding to. When a non-crosslinked cable portion 2 having a desired length is obtained, a crosslinking agent is blended again with a material such as a resin used for the insulating layer and the semiconductive layer, and a portion corresponding to the crosslinked cable portion 1 as described above. Create The cable thus produced has two cable portions containing a cross-linking agent in an insulating layer or the like (a portion to be a cross-linked cable portion 1 after a cross-linking step) and a non-cross-linked cable portion sandwiched between the two. It consists of two.

After a cable having a desired length is obtained, a cable crosslinking reaction is subsequently performed by heating or the like to complete the crosslinking of the insulating layer and the like of the bridged cable portion 1. In the crosslinking step, the cable is continuously crosslinked while the cable is usually moved into a crosslinking tube maintained at a high temperature and a high pressure. The setting of the conditions of the crosslinking reaction in the crosslinking step may be performed according to a normal method known in the art, depending on the production environment, the properties of the produced cable, and the like. Therefore, the temperature in the crosslinking tube used in the crosslinking step is
The determination is made in consideration of the size of the cable to be manufactured, the pressure in the cross-linking tube, the linear speed of the cable in the cross-linking tube, the half-life of the cross-linking agent to be used, and the like. For example, the half-lives of the crosslinking agents DCP, APO, and YPO at 130 ° C. are about 1.8 hours, about 5.6 hours, and about 8.6 hours, respectively. The pressure, the linear speed of the cable, and the like are adjusted so that the crosslinking reaction is sufficiently performed.
Alternatively, it is also possible to select a crosslinking agent according to the reaction conditions in crosslinking and the like. Also, substances generated in the cross-linking reaction may affect the space charge of the power cable.Therefore, when a cross-linking agent that reduces such an effect is selected, or when a specific cross-linking agent is used, the It is preferable to set reaction conditions according to the crosslinking agent. For example, when DCP is used as a cross-linking agent, water is generated by secondary decomposition, so that it is necessary to perform drying as appropriate. Thus, the bridged cable portion 1 shown in FIG.
And the non-crosslinked cable portion 2 are seamlessly and continuously obtained.

The cable shown in FIG. 3 which is a modification of the cable shown in FIG. 1 can be manufactured as follows. First,
A cable having a desired length consisting of a portion corresponding to the cross-linked cable portion 1 (a portion containing a cross-linking agent in an insulating layer, but not yet cross-linked) and a non-cross-linked cable portion 2 is provided.
It is prepared by an extrusion coating method or the like in the same manner as in the production of the cable shown in FIG. After the cross-linking step, a cable including one non-cross-linked cable portion 2 and one cross-linked cable portion 1 is manufactured. Two such cables are manufactured, and then the non-crosslinked cable portions 2 of each cable are connected with a joint 9. Alternatively, the respective cables connected by the joints are prepared by first forming the non-cross-linked cable section 2 and then forming a portion corresponding to the cross-linked cable section 1 and performing a cross-linking step. They may be manufactured by connecting them with a joint 9.

In the manufacture of the cables shown in FIGS. 1 and 3, the lengths of the bridged cable portion 1 and the non-bridged cable portion 2 are not particularly limited, and may be made according to the purpose of use. However, in the production of the crosslinked cable portion 1, depending on the setting of the temperature in the extruder, a scorch due to stagnation occurs, and thus the length that can be adjusted may be limited. The length that can be adjusted varies depending on the cable structure (conductor size, insulation thickness).
It is difficult to manufacture those having a length of m or more. Therefore, in preparing the cross-linked cable portion, when preparing a longer cable, the conditions of the cross-linking reaction are appropriately set, such as setting the reaction temperature low, or the cross-linking is performed using the above-described joint. The cable section may be extended. On the other hand, the length of the non-crosslinked cable portion is not particularly limited as in the case of the crosslinked cable, and may be adjusted according to the situation in which the cable is used. Creating is not a particular problem. If a longer cable is required, it can be dealt with by using a cable of the form shown in FIG. 3. However, if necessary, only the non-crosslinked cable is used when jointing the non-crosslinked cable portions 2. It is also possible to make a cable for a longer distance by interposing a cable consisting of

The power cable of the present invention is most suitable for laying in places such as the sea floor. In the laying method of the present invention, the entire non-crosslinked cable portion 2 is laid on the seabed or the like so as to be always in contact with water. Therefore, since the non-crosslinked cable portion 2 is always cooled by seawater or the like, it is possible to transmit power at a higher capacity such that the cable itself becomes too hot and cannot be used in a normal environment on the ground. Although the power cable of the present invention is suitable for use on the seabed or the like,
The use environment is not limited to the seabed as long as the non-crosslinked cable section 2 is always in an environment where it is cooled.

The advantages of the power cable of the present invention become more apparent by comparison with conventional cables. That is, when a conventional non-crosslinked type cable is laid on the land and the sea bottom, the cable is harder to cool on the land than on the sea floor, so that a certain amount of current cannot flow. Therefore, the amount of current that can flow through the entire cable is determined by the allowable current amount of the cable on land. This means that power is transmitted at a lower amount than the current that can be passed through the submarine cable section,
At the seafloor, the transmission capacity of the cable is below the limit. Comparing the lengths of the cable at the seabed and the land, the length of the cable at the land is usually much shorter than that at the seafloor for long-distance power transmission. Determining the amount of power transmission according to the inferior performance of the cable means that the longer cable does not fully perform. On the other hand, in the power cable of the present invention, the cable section on the land is designed so that there is no problem even if the power is transmitted according to the transmission capacity of the cable on the seabed, so the performance of each cable section is reduced. This means that the production cost is kept low while making full use. That is, in the power cable of the present invention,
Since the land part is a bridge type cable, the problem of heat resistance does not occur in the transmission capacity of the submarine cable. Further, there is no need to make the conductor size extremely large as compared with that at the sea bottom, which is excellent in terms of cable manufacturing cost. In terms of length, the length of the cable required on land is about several kilometers, and a cable of this length can be handled with a single cable without using a joint. If the land part is made non-crosslinked, not only the conductor size but also the usage fee for various materials used for the insulating layer etc. will increase, so the manufacturing cost of the entire cable will increase,
Not preferred.

[0027]

As described above, the power cable of the present invention has a cross-linked cable portion in which the insulating layer and the semi-conductive layer are cross-linked, and a non-cross-linked cable portion in which the insulating layer and the semi-conductive layer are not cross-linked. Since the power cable is composed of a non-crosslinked cable portion, it can be used for long-distance power transmission by making the non-crosslinked cable portion longer. In addition, when the entire non-crosslinked cable portion and at least a part of the crosslinked cable portion of this cable are laid in water, power transmission with a higher capacity than before can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a power cable according to the present invention.

FIG. 2 is a sectional view of the power cable shown in FIG. 1;

FIG. 3 is a diagram showing one configuration example of a power cable of the present invention in which non-crosslinked cable portions are connected to each other by a joint.

FIG. 4 is a diagram showing one embodiment of a power cable laying state laid by the power cable laying method of the present invention.

[Explanation of symbols]

1 ... bridged cable part, 2 ... non-bridged cable part,
3 ... conductor, 4 ... inner semiconductive layer, 5 ... insulating layer, 6 ... outer semiconductive layer, 7 ... shielding layer, 8 ...
Sheath, 9 ... joint

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyuki Miyata 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. (72) Inventor Takashi Takahashi 1-1-5-1 Kiba, Koto-ku, Tokyo Stock Company F-term in Fujikura (reference) 5G311 FA01 5G325 GD06

Claims (3)

[Claims] 1. A power cable comprising a cross-linked cable portion in which an insulating layer and a semi-conductive layer are cross-linked, and a non-cross-linked cable portion in which the insulating layer and the semi-conductive layer are not cross-linked. 2. The power cable according to claim 1, wherein the non-crosslinked cable section has the crosslinked cable sections at both ends. 3. A method for laying a power cable, wherein the entirety of the non-bridged cable part and at least a part of the bridged cable part of the power cable are laid underwater.