JP2008071641A - Rubber or plastic insulated power cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber or a plastic insulated power cable capable of having both water shielding performance and safety in which insulation breakdown hardly occurs even when used inserted in a POF cable pipe, while having a necessary mechanical strength using a water shielding layer having an insulating plastic film. <P>SOLUTION: The power cable 1 has a water shielding layer 20 and a conductive sheath 30 by a conductive plastic film installed in order on its external semi-conductive layer 14, and is inserted in a pipe for POF (pipe-type oil filled) cable. The water shielding layer 20 is composed of a three layer of a conductive plastic film 151, a metal foil 152, and an insulating plastic film 153. The insulating plastic film 153 has a plurality of apertures 22 in which the conductive sheath 30 is inserted. A longitudinal lapping tape 21 is fusion bonded on an overlapping portion of the water shielding layer 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber or plastic insulated power cable such as a CV cable, and in particular, a pipe-type oil-filled (POF) cable pipe (steel pipe) is used as a pipe line, and a water-impervious rubber or plastic drawn into this pipe It relates to an insulated power cable.

  Among rubber or plastic insulated power cables, there is known a power cable with improved water shielding (see, for example, Patent Document 1).

  FIG. 7 shows a conventional water-impervious rubber or plastic insulated power cable. In the figure, (a) is a cross-sectional view, and (b) is a cross-sectional view taken along line BB of (a).

  As shown in FIG. 7 (a), this water-impervious rubber or plastic insulated power cable (hereinafter sometimes simply referred to as “power cable”) 100 is composed of a conductor 11 and an internal semiconducting conductor covering the conductor 11. A cable core comprising a layer 12, an insulator 13 made of rubber or polyethylene covering the inner semiconductive layer 12, and an outer semiconductive layer 14 covering the insulator 13, and further covering the outer semiconductive layer 14 And a sheath 16 made of an insulating plastic that covers the water shielding layer 15.

  As shown in FIG. 7B, the water shielding layer 15 includes a conductive plastic film 151 laminated on the external semiconductive layer 14, and a metal foil made of lead, aluminum, etc. provided on the conductive plastic film 151. 152 and an insulating plastic film 153 laminated on the metal foil 152.

  In this power cable 100, for wrap bonding, further comprising a plastic tape (or a laminate in which a metal is laminated on a plastic tape) having a moisture permeability of ½ or less of the plastic tape used for the laminate tape of the water shielding layer 15. A plastic tape 17 is bonded onto the overlap portion of the water shielding layer 15.

  By adopting such a configuration, it is possible to prevent moisture from entering from the sheath 16 and prevent the electrical characteristics of the power cable 100 from being deteriorated.

  On the other hand, a POF cable is a cable (steel pipe) installed in a power transmission route with a plurality of cables filled with insulating oil in the pipe (steel pipe). However, because of the use of high hydraulic insulation oil, it is expensive to install and maintain the hydraulic compensation circuit, and there is a possibility that it may adversely affect the environment due to oil leakage, etc. There are various problems such as the need for consideration.

In contrast, pipes (steel pipes) that have been laid with POF cables (hereinafter referred to as “POF cable pipes”) are used as they are, and the POF cables are replaced with water-insulated rubber or plastic insulated power cables. By pulling this into the POF cable pipe, the equipment of the hydraulic pressure compensation circuit can be omitted, so that the above problem can be solved.
Japanese Utility Model Publication No. 62-9611 (pages 3-4, Fig. 4)

  However, according to the conventional power cable, when the power cable is laid on the POF cable pipe, there are problems listed below.

(A) When the POF cable is replaced with the rubber or plastic insulated power cable of Patent Document 1, it is difficult to ensure a transmission capacity equivalent to that of the POF cable. A plastic insulated power cable such as a CV cable has a thicker insulator than a POF cable (for example, 275 kV class, 23 mm for a power cable and 16.5 to 19.5 mm for a POF cable). In addition, the POF cable does not have a sheath at the core in the pipe, but the plastic insulated power cable has a thickness because it has a sheath (for example, 275 kV class is 5 mm). Therefore, if the conductor size is not reduced by that amount, it cannot be laid.

(B) In order to maintain the conductor size, it is conceivable to reduce the thickness of the sheath. However, when the sheath is thinned, the insulation strength of the sheath decreases. That is, when a lightning surge or an open / close surge enters the conductor, a high voltage appears between the metal foil of the water shielding layer and the POF cable pipe. If holes are opened in the sheath and the water shielding layer due to the insulation breakdown of the sheath, moisture may enter the insulator and may deteriorate over time.

(C) As a means for preventing dielectric breakdown due to an abnormal voltage when the sheath is thinned, it is conceivable to make the sheath the same potential as the POF cable pipe by using a conductive plastic. However, since the insulating layer between the metal foil of the water shielding layer and the POF cable pipe is only the insulating plastic film on the metal foil, a voltage is applied to the insulating plastic film, and the dielectric breakdown is possible. There is sex. For this reason, it is necessary to make this insulating plastic film conductive, and to make all of the insulating plastic film between the metal foil of the water shielding layer and the POF cable pipe have the same potential.

(D) However, if the plastic films on both sides of the metal foil are both made of conductive plastic, the rigidity of the water shielding layer itself is lowered and wrinkles are likely to occur in the water shielding layer. If soot is generated in the water-impervious layer, when the insulator is repeatedly expanded / contracted due to temperature changes when the cable is energized, it will break and tear starting from the soot, leading to a decrease in water-insulating performance. . Therefore, in order to attach the laminate tape of the water shielding layer vertically to the cable core so as not to cause wrinkles smoothly, a certain degree of rigidity is required, but a material having both necessary mechanical strength and conductivity is required. Difficult to get.

  Accordingly, an object of the present invention is to provide a water shielding layer having an insulating plastic film so as to have a necessary mechanical strength and to prevent insulation breakdown even when used by being pulled into a POF cable pipe. It is an object of the present invention to provide a rubber or plastic insulated power cable that can achieve both water performance and safety.

  In order to achieve the above object, the present invention provides a cable core and a longitudinally covering coating provided so as to have an overlap portion on the outer peripheral surface of the cable core, and at least a first metal foil and an outer periphery thereof. In a rubber or plastic insulated power cable comprising a water shielding layer having an insulating plastic film and a sheath provided on the outer peripheral surface of the water shielding layer, the first insulating plastic film is disposed on the surface of the metal foil. It has a plurality of apertures communicating with each other in the cable length direction, and the sheath has conductivity and is formed so as to enter the aperture and contact the metal foil. Provide rubber or plastic insulated power cable.

  According to the present invention, the water-insulating performance, which provides the necessary mechanical strength using the water-insulating layer having an insulating plastic film and is less likely to cause dielectric breakdown even when used by being pulled into a POF cable pipe. It is possible to provide a rubber or plastic insulated power cable that can achieve both safety and safety.

  FIG. 1 shows a water-impervious rubber or plastic insulated power cable according to an embodiment of the present invention. In the figure, (a) is a cross-sectional view, and (b) is a cross-sectional view taken along line AA of (a). FIG. 2 is a perspective view with stripped steps for explaining the structure of the water-impervious rubber or plastic insulated power cable according to the embodiment of the present invention.

  As shown in FIG. 1A, the power cable 1 includes a cable core including a conductor 11, an internal semiconductive layer 12, an insulator 13, and an external semiconductive layer 14, and further includes an external semiconductive layer. A water shielding layer 20 that covers the conductive layer 14 and a conductive sheath 30 made of conductive plastic provided on the water shielding layer 20 are provided. For the adhesion of the overlap portion of the water shielding layer 20, it is desirable to use an adhesive having a high adhesive strength in a high temperature region. For example, an adhesive made of polyester polyurethane and aromatic polyisocyanate is preferable.

  As shown in FIG. 1B, the water shielding layer 20 includes a conductive plastic film 151, a metal foil 152, and an insulating plastic film 153, as in FIG. As the insulating plastic film 153, a film having an appropriate rigidity capable of obtaining necessary mechanical strength so as not to cause wrinkles in the water shielding layer during production is used.

  The insulating plastic film 153 has a plurality of apertures 22 at predetermined positions. The opening 22 is provided only in the insulating plastic film 153 and the surface of the metal foil 152 is exposed. When the conductive sheath 30 enters the opening 22 and the lower surface thereof directly contacts the metal foil 152, the conductive sheath 30 and the metal foil 152 are electrically at the same potential. Further, the same potential is applied to the conductive plastic film 151 and the outer semiconductive layer 14.

  The apertures 22 are formed in one or more rows at predetermined intervals in the cable length direction. Further, a plurality of apertures may be formed at predetermined intervals in the circumferential direction.

  From the viewpoint of ensuring electrical continuity, it is advantageous to increase the diameter of the aperture 22 and reduce the distance between the adjacent apertures 22. If the mechanical strength of the water layer 20 is lowered, the manufacturability and water impermeability are hindered. Therefore, it is preferable that the diameter of the opening 22 is made as small as possible and the interval is made large. At this time, it is desirable that the total area of the plurality of apertures 22 is 0.1% or more of the area ratio with respect to the insulating plastic film 153. On the other hand, the upper limit is preferably 10% or less from the viewpoint of securing mechanical strength.

  In the electric power cable 1, a vertical tape 21 provided with an adhesive layer made of a general adhesive on both surfaces of a metal foil such as aluminum is further bonded onto the overlap portion of the water shielding layer 20. For example, with the end portion of the water-impervious layer 20 on the upper side of the overlap portion (width of about 20 mm) as a reference (centered), the vertical tape 21 is attached so as to have a width of about 20 to 40 mm in both circumferential directions. Provide.

In the above embodiment, the insulating plastic film 153 is used for laminating the metal foil 152, and as other means for ensuring conduction to both the outer semiconductive layer 14 and the conductive sheath 30, the following is described. There is a way.
(A) The insulating plastic film 153 is laminated on both surfaces of the metal foil 152, and the opening 22 is provided on the both surfaces of the plastic film.
(B) An insulating plastic film 153 is laminated on one surface of the metal foil 152, and the opening 22 is provided in this film. Do not laminate anything on the other side.

(Production method)
Next, a method for manufacturing a water-impervious rubber or plastic insulated power cable according to an embodiment of the present invention will be described. FIG. 3 is a production line layout for forming a water shielding layer, and FIG. 4 is a detailed view of the water shielding layer forming portion in FIG. 3. FIG. 5 is a detailed view of the vicinity of the fusion-bonding process of the water shielding layer wrap portion in FIG. 4 as viewed from above.

  First, the cable core 120 wound around the delivery drum 110 is pulled out, a water shielding layer is formed at the water shielding layer forming portion 130, and wound around the winding drum 140.

  In the water-impervious layer forming unit 130, in order to form a water-impervious layer around the cable core 120, the water-impervious tape 220 sent from the water-impervious tape roll 210 is vertically attached to the cable core 120 and guide rollers 230 a to 230 d. It is formed so as to be wrapped using.

  Next, the water shielding tape wrap part 310 is heated with the heater 250a, and the water shielding tape wrap part 310 is welded. The temperature at that time is preferably equal to or higher than the melting temperature of the adhesive applied to the water shielding tape 220. The heating method is any method as long as it does not adversely affect the materials used (cable core 120, water shielding tape 220, adhesive, etc.) and can be heated to a predetermined temperature in a short time. But it ’s okay.

  FIG. 6 is a detailed view of the vicinity of the welding process of the vertical reinforcing tape in FIG. 4 as viewed obliquely from above. First, the vertically attached reinforcing tape 270 fed from the vertically attached reinforcing tape roll 260 is vertically attached immediately above the welded water shielding layer wrap portion 410. Thereafter, the vertically attached reinforcing tape 270 is heated by the heater 250b and heated to a temperature equal to or higher than the melting temperature of the adhesive applied to the reinforcing tape 270, and the reinforcing tape 270 vertically attached is welded to the water shielding layer wrap portion 410. . The heating temperature at this time is also preferably equal to or higher than the melting temperature of the adhesive applied to the water shielding tape 220.

(Effect of embodiment)
According to the present embodiment, the following effects are obtained.
(A) Since the insulating plastic film 153 of the water shielding layer 20 is provided with a plurality of apertures 22 communicating with the lower metal foil 152, the conductive sheath 30 made of conductive plastic enters the apertures 22. As a result of having the same electrical potential from the outer semiconductive layer 14 of the cable to the POF cable pipe, insulation breakdown does not occur, water shielding is improved, deterioration is prevented, and lightning surges and switching surge intrusions are prevented. Safety can be improved.

(B) Since the insulating plastic film 153 of the water shielding layer 20 does not need to consider conductivity, a material having a large rigidity can be used. It is possible to prevent deterioration of the water shielding performance due to tearing.

(C) Since the metal foil 152 has no opening, the water shielding performance of the water shielding layer 20 can be maintained.

(D) Since the vertical tape 21 is adhered on the overlap portion of the water shielding layer 20, peeling at the overlap portion due to thermal expansion can be prevented, and moisture can be prevented from entering. Thereby, generation | occurrence | production of a water tree and generation | occurrence | production of a cable dielectric breakdown can be prevented.

(E) Since the vertically attached tape 21 is adhered on the overlap portion of the water shielding layer 20, the water shielding layer 20 can be prevented from being stretched in the circumferential direction due to thermal expansion, and the conductive sheath 30 can be cracked. Occurrence can be prevented.

Next, examples of the present invention will be described. In this example, a power cable with a water shielding layer of 275 kVCV1 × 2000 mm ² was used as the power cable 1.

  The configuration of the power cable 1 is as shown in FIGS. 1 and 2. The diameter of the apertures 22 in the water shielding layer 20 is 5.5 mm, the interval between the apertures 22 adjacent in the cable length direction is about 100 mm, and two rows are provided in the cable length direction. And the ratio (area ratio) which the area of the opening part 22 occupies for the area of the water shielding layer 20 (insulating plastic film 153) is 0.15%.

  Conductive PVC was used as the conductive plastic film 151, aluminum foil was used as the metal foil 152, and PET + transparent PVC was used as the insulating plastic film 153. The material of the conductive sheath 30 provided on the outer peripheral surface of the water shielding layer 20 is conductive PVC.

  Using this manufactured power cable 1, a test line simulating the laying situation in the manhole is constructed, and 30 heat cycle tests (conductor temperature is room temperature to 90 ° C.) and a stretching test equivalent to 30 years are performed. Carried out. As a result of disassembling the cable after the test was completed, no abnormality such as wrinkles or tears was observed in the water shielding layer 20, and it was confirmed that there was no problem.

Next, the optimum conditions for the water shielding layer 20 will be described.
First, four sheets of laminate tape, in which the metal foil 152 and the insulating plastic film 153 were sequentially formed on the conductive plastic film 151 using the same material as in the above-described example, were prepared as the water shielding layer 20. Each laminate tape has a different number of apertures 22 (0, 1, 2, 4). Also, four types of conductive PVC sheets (140 mm square, 1 mm thickness) were prepared as the conductive sheath 30, and the laminate tape was fused to each. Table 1 shows the results of measuring the volume resistance value for each of the obtained samples.

  As is clear from Table 1, the measured value when the aperture 22 is not provided is 6,800 Ω · cm, whereas the measured value when the aperture is provided is greatly increased to 98 to 130 Ω · cm. The volume resistance value of the conductive PVC is close to 22 Ω · cm.

  In addition, since there is almost no difference in volume resistance value depending on the number of apertures 22, it is considered that there is no electrical problem if the apertures 22 are larger than about 0.1% in area ratio.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from or changing the technical idea of the present invention. For example, a conductive plastic film other than conductive PVC can be used as the conductive sheath. Further, the rubber or plastic insulated power cable of the present invention is not limited to being drawn into a pipe for a pipe-type oil-filled (POF) cable, and can be used for general purposes.

1 shows a water-impervious rubber or plastic insulated power cable according to an embodiment of the present invention, wherein (a) is a cross-sectional view and (b) is a cross-sectional view taken along line AA of (a). It is the perspective view which peeled off the step for demonstrating the structure of the water-impervious rubber | gum or plastic insulated power cable which concerns on embodiment of this invention. It is a manufacturing line layout for water shielding layer formation. FIG. 4 is a detailed view of a water shielding layer forming portion in FIG. 3. FIG. 5 is a detailed view of the vicinity of the fusion process of the water shielding layer wrap portion in FIG. 4 as viewed from above. FIG. 5 is a detailed view of the vicinity of the welding process of the longitudinal reinforcing tape in FIG. 4 as viewed obliquely from above. The conventional water shielding type rubber | gum or plastic insulated power cable is shown, (a) is sectional drawing, (b) is sectional drawing of the BB line of (a).

Explanation of symbols

1: Power cable 11: Conductor 12: Inner semiconductive layer 13: Insulator 14: Outer semiconductive layer 15: Water shielding layer 151: Conductive plastic film 152: Metal foil 153: Insulating plastic film 16: Sheath 17: Wrap Adhesive plastic tape 20: Water shielding layer 21: Vertical tape 22: Opening portion 30: Conductive sheath 100: Power cable 110: Feeding drum 120: Cable core 130: Water shielding layer forming portion 140: Winding drum 210: Water shielding tape roll 220: Water shielding tape 230a to 230d: Guide rollers 250a to 250b: Heater 260: Vertically attached reinforcing tape roll 270: Vertically attached reinforcing tape 310: Water shielding layer wrap portion 410: Sealed water shielding layer wrap Part

Claims (7)

A water shielding layer having a cable core and at least a metal foil and a first insulating plastic film disposed on the outer periphery of the cable core; In a rubber or plastic insulated power cable comprising a sheath provided on the outer peripheral surface of the water shielding layer,
The first insulating plastic film has a plurality of openings in the cable length direction communicating with the surface of the metal foil,
The rubber or plastic insulated power cable according to claim 1, wherein the sheath has conductivity and is formed so as to enter the aperture and come into contact with the metal foil.   The rubber or plastic insulated power cable according to claim 1, wherein the water shielding layer has a conductive plastic film on the cable core side of the metal foil.   The water shielding layer has a second insulating plastic film on the cable core side of the metal foil, and the second insulating plastic film has a plurality of apertures communicating with the surface of the metal foil. The rubber or plastic insulated power cable according to claim 1, wherein the cable is provided in a cable length direction.   The said 1st or 2nd insulating plastic film has the several opening part connected in the circumferential direction to the surface of the said metal foil in any one of Claims 1 thru | or 3 characterized by the above-mentioned. Rubber or plastic insulated power cable as described.   The area ratio with respect to the first or second insulating plastic film of each of the plurality of apertures is 0.1% or more, respectively. Rubber or plastic insulated power cable.   The rubber or plastic insulated power cable according to any one of claims 1 to 5, wherein the water shielding layer is provided with a vertical tape on the overlap portion.   The rubber or plastic insulated power cable according to any one of claims 1 to 6, which is drawn into a pipe for a pipe-type oil-filled (POF) cable.