JPH0365094B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for water-shielding a connection portion of a cable by providing a water-shielding layer made of metal and conductive rubber/plastic material on a cable insulator or an external semiconducting layer. Conventionally, for example, in order to waterproof the connection part of a cross-linked polyethylene power cable, a method has been used in which a waterproof rubber or plastic tape is wrapped around the cable connection part. However, this method has the disadvantage that if the waterproof tape is not wrapped sufficiently, water tends to enter the cable connection, and if water enters the cable over a long period of time, the insulation may deteriorate. Recently, power cables have been proposed in which a laminate tape of metal and conductive rubber/plastic is provided as a water-shielding layer on the cable insulator or external semiconductive layer to prevent water from entering the cable in the radial direction. There is a growing need to prevent water from entering the connections of such power cables. Usually, as shown in FIG. 1, the cable parts 1 and 1' and the cable connection part 2 do not have the same diameter, and the connection part 2 has slope parts 3 and 3'.
This provides continuous connection with cable sections 1 and 1'. Therefore, if a single sheet of laminated tape made of metal and conductive rubber/plastic is used as a water-shielding tape and is applied vertically across the cable parts 1 and 1' and the connection part 2, the water-shielding tape will not wrinkle. It is inevitable that it will be generated. If you complete the cable connection with the water-shielding tape still wrinkled,
During the subsequent heating cycle, cracks develop from the metal located in the wrinkles of the waterproof tape, making it impossible to maintain a stable water-blocking function over a long period of time. The purpose of the present invention is to effectively prevent water from seeping in from the connection part of a cable over a long period of time by providing a water-blocking layer made of a laminate of metal and conductive rubber/plastic on the cable insulator or external semiconductive layer. An object of the present invention is to provide a method for water-shielding a cable connection part. The present invention provides water shielding for the connecting portion of a cable in which a water shielding layer made of a laminate of metal and conductive rubber/plastic is provided on a cable insulator or an external semiconductive layer. At least two layers of laminated tape made of metal and conductive rubber/plastic are stacked vertically over the water layer and the connection insulator or external semiconductive layer, and then heat-shrinkable tape is applied on top of that. It is characterized in that it is covered with a conductive synthetic resin tube, and then heated under pressure to tightly integrate the heat-shrinkable tube, the laminate tape, and the overlapping portions of the laminate tape. In the method of the present invention, a laminated tape made of metal and conductive rubber/plastic material is used as a water-shielding tape, and as shown in FIG. A water-shielding tape 4 is produced, and this water-shielding tape 4 is
As shown in FIG.
Attach it to the outer periphery of these. In this case, as shown in FIG. 4, the water-shielding tape 4 is divided so as not to wrinkle the water-shielding tape 4, and the water-shielding tapes 4 are overlapped with each other by at least 5 mm to improve the water-shielding effect. Furthermore, a tube 7 made of heat-shrinkable conductive synthetic resin is placed on top of the tube 7, the tube 7 is shrunk, and then heated under pressure. As a specific pressurizing method, it is common to wrap one or more Teflon tapes with good heat resistance on the shrink tube while overlapping them. If the heat-shrinkable conductive synthetic resin tube 7 is not used and heated under pressure, the water-shielding tape 4 will shift at the slope portions 3 and 3', causing the water-shielding tape 4 to shift.
wrinkles appear on the skin. However, when the tube 7 made of heat-shrinkable conductive synthetic resin is used, the tube 7 is completely integrated with the conductive layer of the water-shielding tape 4 by heating under pressure, so the occurrence of wrinkles in the water-shielding tape 4 is suppressed. Not only is it possible to improve the water-shielding performance and the electrical performance of the cable (by integrating the water-shielding tape 4 and the cable core 8, smoothing the outer semiconducting layer, suppressing the generation of voids, etc.), Ru. After removing the Teflon tape, a metal shielding layer 9 made of copper tape or the like and a corrosion protection layer 10 made of polyvinyl chloride or polyethylene are sequentially provided on the outside of the core 8. The water-shielding tape 4 used in the method of the present invention is used to obtain electrical continuity with water-shielding layers 5 and 5' made of metal and conductive rubber/plastic provided on the cable insulator or external semiconductive layer 6. In addition, it must be a laminated tape with conductive rubber or plastic material bonded to one or both sides of the metal.
Further, the metals used here include copper, aluminum, lead, etc., but lead is particularly excellent in terms of corrosion resistance.
Heat-shrinkable conductive synthetic resin tubes used in the method of the present invention include conductive crosslinked polyethylene tubes, conductive vinyl chloride tubes, conductive polyethylene tubes, and the like. Next, the present invention will be explained with reference to Examples and Reference Examples. Example 1 Water-shielding treatment for the connection part of a 6600V water-shielding power cable with a conductive polyethylene (50μ thick)/lead (50μ thick)/conductive polyethylene (50μ thick) layer provided as a water-shielding layer on the external semiconductive layer. In doing so, straddling the water-shielding layer of the cable and the outer semiconducting layer of the connection part,
Conductive polyethylene (50μ thickness) / Lead (50μ thickness) /
4 waterproof tapes made of conductive polyethylene (50μ thick)
The sheets are stacked with a 10mm wrap and attached vertically, and then a heat-shrinkable conductive tube made of cross-linked polyethylene is placed on top of the tube, the tube is shrunk, and then a Teflon tape with a thickness of 0.3mm is placed around the outer circumference of the tube. Wrap 4 layers in 2 wraps at 160℃ x 30 under pressure of 5Kg/ ^cm2
After heating for several minutes, we completed the waterproofing of the connection. Then,
After removing the Teflon tape, a metal shielding layer made of copper tape and a corrosion protection layer made of vinyl chloride were sequentially formed thereon. Example 2 Water-shielding treatment for the connection part of a 6600V water-shielded power cable with a conductive polyethylene (50μ thick)/copper (10μ thick)/conductive polyethylene (50μ thick) layer provided as a water-shielding layer on the cable insulator. For this purpose, apply 3 layers of conductive polyethylene (50μ thick)/copper (10μ thick)/conductive polyethylene (50μ thick) water-shielding tape across the water-shielding layer of the cable and the insulator at the connection part.
The sheets were stacked vertically with a 6 mm wrap, and then a heat-shrinkable conductive tube made of cross-linked polyethylene was placed on top of the tube, the tube was shrunk, and then a Teflon tape with a thickness of 0.2 mm was placed around the outer circumference of the tube. Wrap 3 layers with 1/2 wrap, 140 under pressure of 2Kg/cm ²
Waterproofing of the joint was completed by heating for 30 minutes at ℃. Next, after removing the Teflon tape, a metal shielding layer made of copper tape and a corrosion protection layer made of vinyl chloride were successively formed thereon. Comparative Example 1 In Example 1, four pieces of water-blocking tape made of conductive polyethylene (50 μ thick)/lead (50 μ thick)/conductive polyethylene (50 μ thick) were placed on the connection part, 10 mm thick.
The same operation as in Example 1 was repeated, except that instead of overlapping the tapes with wraps and attaching them vertically, a waterproof tape made of butyl rubber (Fuko Tape No. 2 manufactured by Furukawa Electric) was wrapped in four layers with 1/2 wraps. Comparative Example 2 In Example 1, a water shield made of conductive polyethylene (50 μ thick)/lead (50 μ thick)/conductive polyethylene (50 μ thick) was placed on the connection part without using the heat-shrinkable conductive cross-linked polyethylene tube. The same operation as in Example 1 was repeated, except that Teflon tape was wrapped on top of the tape. Comparative Example 3 Instead of stacking four waterproof tapes vertically with a 10mm wrap in Example 1, a single piece of conductive polyethylene (50μ thick)/lead (50μ thick) was used.
The procedure of Example 1 was repeated, except that a water-blocking tape made of conductive polyethylene (50 μm thick) was used for vertical splicing and wrapping. In the Examples and Comparative Examples, the conductive polyethylene used was polyethylene mixed with conductive carbon to have a specific resistance of 10 ³ to ^{10 5} Ω・cm, and the heat-shrinkable conductive cross-linked polyethylene tube was A material with a shrinkage rate of 30 to 50% was used. The water-shielded cable connections in the above examples and comparative examples were subjected to one reciprocating bend at a diameter 10 times the outer diameter of the cable, and then heated to a conductive temperature of 105 by applying electrical current.
A heating cycle of 6 hours at room temperature and 6 hours at room temperature was added, followed by immersion in a water bath at 80°C for one month. Thereafter, the cable connection portion was disassembled, the state of the metal of the water-shielding tape used for the water-shielding layer was observed with the naked eye, and the moisture content of the cable insulator was measured using a solid-state moisture meter manufactured by DuPont. The results are shown in Table 1. Note that the moisture content of the original table insulator was <0.01% by weight.

[Table] As is clear from the above examples, according to the method of the present invention, (1) wrinkles do not occur in the water-shielding laminate tape used for water-shielding the joints, and (2) the water-shielding laminate tape can be used for a long period of time. A connection part with excellent water-blocking performance is obtained, and is extremely useful in practice.

[Brief explanation of drawings]

Figure 1 is a schematic side view of the cable connection section before water shielding.
Figure 2 is a schematic side view, partially in section, showing a state in which a piece of water-shielding tape is attached vertically to the cable connection part in Figure 1;
Fig. 3 shows one of the cable connection sections subjected to the method of the present invention.
FIG. 4 is a schematic cross-sectional view of the cable connection portion of FIG. 3 taken along the line A-A'. 1, 1'... Cable part, 2... Cable connection part, 3, 3'... Slope part of cable connection part,
4... Waterproof tape (laminate tape), 5,
5'...water-shielding layer, 6...connecting portion insulator or outer semiconducting layer, 7...conductive heat-shrinkable tube, 8...
... Cable core, 9 ... Metal shielding layer, 10 ... Corrosion protection layer.

Claims (1)

[Scope of Claims] 1. When water-shielding a connecting portion of a cable in which a water-shielding layer made of metal and conductive rubber/plastic material is provided on a cable insulator or an external semiconductive layer, At least two layers of laminated tape made of metal and conductive rubber/plastic are stacked vertically over the water layer and the connection insulator or external semiconductive layer, and then heat-shrinkable tape is applied on top of that. The heat-shrinkable conductive synthetic resin tube is covered with a conductive synthetic resin tube, and then heated under pressure to tightly integrate the heat-shrinkable conductive synthetic resin tube, the laminate tape, and the overlapping portion of the laminate tape. Water-shielding method for cable connections.