JPH059777Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to an improvement of a water-shielding rubber-plastic insulated power cable. [Prior Art] It is well known that rubber-plastic insulated power cables suffer from water absorption deterioration phenomena such as water tree and boat tree due to water intrusion into the cable. This water absorption deterioration phenomenon occurs through the plastic anti-corrosion layer provided on the outermost layer of the cable, or
Water entering the cable from the cable end causes tree-like defects on the cable insulation, causing
This leads to dielectric breakdown. In order to prevent such water absorption and deterioration phenomenon, a laminate tape made by laminating conductive layer plastic tape on both sides of lead foil is placed vertically on the cable core to cover it.
We developed a water-shielding rubber-plastic insulated power cable in which a water-shielding layer was provided by heat-sealing the overlapping parts of the laminate tape and closely integrating the laminate tape with the cable core (Japanese Patent Publication No. 60-23854). [Problems to be solved by the invention] However, such water-shielding rubber-plastic insulated power cables also have the following problems. When repeated heat cycles are applied at high temperatures (90° to 130°C), 0 to 5% strain occurs in the radial direction due to expansion and contraction of the insulator due to the heat cycles. Since the lead laminate tape is tightly integrated and installed directly above the cable core, the lead is repeatedly subjected to 0 to 5% strain during heat cycles.
In the end, the deal ends. In order to avoid such problems, it is necessary to improve the fatigue rupture characteristics of the lead foil of the water-shielding layer of water-shielding rubber-plastic insulated power cables. [Means for Solving the Problems] The present invention was developed as a result of intensive studies to solve the above problems, and in FIGS. 1 and 2, an inner conductive layer 7 and a rubber Water-shielding tape made of a lead laminated tape made by laminating a conductive plastic film 9 on both sides of lead foil on the outer conductive layer 5 of a rubber-plastic insulated power cable, which has a plastic insulating layer 6 and an outer conductive layer 5 sequentially provided. A water-shielding rubber-plastic insulated power cable provided with a layer 4, characterized in that a lead foil 10 made by overlapping two or more sheets of lead foil is used as the lead foil of the lead laminate tape constituting the water-shielding layer. It is something. Laminated lead foil 1 constituting lead laminate tape
The total thickness of the conductive plastic film 9 is preferably in the range of 0.03 to 0.10 mm, and the thickness of the conductive plastic film 9 is in the range of 0.05 to 0.2 mm. The total thickness of lead foil was specified as 0.03 to 0.10mm.
If the thickness is less than mm, it is difficult to laminate conductive plastic film on both sides of the stacked lead foil.
Therefore, long waterproof tape cannot be manufactured.
Moreover, if the thickness exceeds 0.10 mm, the effect of the present invention will be reduced, so it is not suitable. The improvement in fatigue properties due to the stress relaxation of the lead foil of this invention is achieved on both sides of the stacked lead foil with a total thickness of 0.03 to 0.10 mm.
This is noticeable when using a lead laminate tape laminated with a 0.03 to 0.10 mm thick conductive plastic film. The laminated lead foil may be produced by rolling a plurality of lead foils at once during lead foil rolling, or by stacking a plurality of lead foils during production of a laminate tape and laminating conductive plastic films on both sides. [Operation] The reason why the water-shielding rubber-plastic insulated power cable having the above structure has excellent fatigue rupture characteristics is as follows. In other words, in a cable in which a lead laminated tape, which is made by laminating a conductive plastic film on both sides of a piece of lead foil, is closely integrated with the cable core to form a water-shielding layer, the strain caused by the heat cycle of the cable is The lead foil is used as is (Fig. 3a), but when the lead foil 10 made by stacking two or more lead foils is used as the lead foil for the lead laminate tape of the water-blocking layer, distortion occurs between the stacked lead foils. As a result, in a cable whose water-shielding layer is made by closely integrating a laminated tape made of two layers of lead foil with conductive plastic film 9 laminated on both sides of the cable core, the strain during cable heat cycles is reduced. However, since the lower lead foil absorbs the strain, almost no strain occurs in the upper lead foil (Fig. 3b). Therefore, even if fatigue cracks occur in the lower lead foil, no cracks will occur in the upper lead foil, and the function as a water barrier layer will not be impaired, and the fatigue life of the water barrier layer due to cable heat cycles will be reduced. This is a significant improvement. In addition, since we use laminated lead foil, even if there are pinholes or cracks in one sheet of lead foil, water or chemicals will not enter through them, and the water-blocking performance will be significantly improved. be. [Example] Next, an example of the present invention will be described with reference to FIGS. 1 and 4. 69KV water-shielded CV cable (aluminum conductor 1200mm ² )
When manufacturing the cable, a lead laminate tape shown in Table 1 is vertically wrapped on the cable external conductive layer 5 to form a water-blocking layer 4, and then a conductive cloth tape is wrapped around it to form a conductive tape layer 3. After closely integrating the laminate tape with the cable's external conductive layer, 50 annealed copper wires of 1.6 mmφ were spirally wound on the outside as a metal shielding layer 2, and then a PVC anticorrosion layer 1 was provided to complete the cable. Insert the above cable into the conduit pipe, seal both ends of the conduit pipe, and turn on the conductor at a temperature of 130°C for 8 hours by energizing the conductor.
A heat cycle of 16 hours off was performed. The cable was disassembled after 50, 100, and 150 heat cycles, and it was evaluated whether or not there were any cracks in the water-blocking layer 4. The obtained results are also listed in Table 1, and the cable of this invention shows that even after 150 heat cycles,
Although no cracks were found in the water shielding layer (out of the two lead foils, there was a crack in the lead foil on the cable core side).
In Comparative Example 1, cracks were observed in the water-blocking layer after 100 heat cycles. Using the cable after 100 heat cycles,
After leaving the water-blocking layer but removing other outer coverings, the product was immersed in a water tank as shown in Figure 4, and 0.5Kg/cm ² was absorbed.
Loaded for 24 hours. The water barrier layer was then removed and the moisture content of the outer conductive layer was measured using a Dupont solid state moisture meter. As a result, in the cable of the present invention, the moisture content in the outer conductive layer was almost the same or less than that of the original cable, whereas in the cable of the comparative example, a significant increase in moisture was observed and cracks in the water-shielding layer were observed. It became clear that water had entered through the pipe.

[Effect of idea]

As shown in the above embodiment, the present invention provides cable heat by using a lead laminated tape made by laminating conductive plastic tape on both sides of lead foil overlaid on the water-shielding layer of a water-shielding rubber-plastic insulated power cable. A remarkable improvement in fatigue life due to cycles and a remarkable improvement in water-blocking performance by using two or more stacked lead foils as the lead foil of the lead laminate tape are extremely useful in practice.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the water-shielding rubber-plastic insulated power cable of the present invention, Figure 2 is an enlarged sectional view of the water-shielding layer, and Figure 3 is a schematic diagram showing the degree of stress applied inside and outside the water-shielding layer. , FIG. 4 is a schematic diagram of the water immersion test apparatus. 4... Water-blocking layer, 9... Conductive plastic film, 10... Laminated lead foil.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) On the outer conductive layer of a rubber-plastic insulated power cable, which has an inner conductive layer, an insulator layer, and an outer conductive layer sequentially provided on the outside of the conductor, conductive material is applied to both sides of the lead foil. In a water-shielding rubber-plastic insulated power cable having a water-shielding layer made of a lead-laminated tape formed by laminating a plastic film, two or more pieces of lead foil are used as the lead foil of the lead-laminated tape forming the water-shielding layer. A water-shielding rubber-plastic insulated power cable characterized by the use of overlapping lead foil. (2) The total thickness of the overlapping lead foils that make up the water-blocking layer is 0.03
The water-shielding rubber-plastic insulated power cable according to claim 1, characterized in that the conductive plastic film has a heat resistance of 0.05-0.2 mm.