JPS6016683B2 - Method for manufacturing overhead insulated wires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing overhead insulated wires that reduces residual stress on the surface of stranded wires that occurs during conductor manufacturing and adds compressive stress in order to prevent stress corrosion cracking of overhead insulated wires. be.

In general, overhead insulated wires have high tensile strength and stranded wires such as hard copper wires or hard aluminum wires as conductors. In this case, tensile stress and bending stress remain.

When installing overhead insulated wires, the terminals are treated to prevent corrosion, but at present it is difficult to prevent rainwater from entering from the terminals, and the current Corrosion is accelerated by air pollution due to sulfur dioxide gas and other harmful components in the atmosphere.
On the other hand, if residual stress remains in the conductor as described above, the synergistic effect of the two causes problems such as abnormal disconnection of the flaming conductor. In particular, when copper wire is used as the bare wire, it is much more troublesome than when using aluminum wire on the surface. In many cases, the tensile strength eventually decreases from the calculated value and the wire breaks.

Therefore, in the past, European copper wire or semi-hard copper wire was used for the outermost millet wire of a stranded conductor to reduce residual stress.
Due to these structures, it is difficult to control the temperature at which the semi-hard copper wire becomes dull, and the manufacturing cost increases considerably.

It is also possible to seal the end of the cable with a watertight compound to prevent corrosive atmosphere and rainwater from entering.
This method also poses difficulties in terminal processing.

In view of the current situation, the present invention has conducted extensive research to improve the situation, and as a result, has discovered a method for manufacturing overhead insulated wires that has significantly high resistance to stress corrosion cracking.

That is, in the method of the present invention, an aerial conductor in which a desired number of conductors are twisted around the outer periphery of a central conductor is forged by a cold forging machine that rotates in the opposite direction to the direction in which the conductors are twisted, without heating the metal rods. This is introduced into a hammering machine that causes compression plastic deformation, and compression molded into a circular shape while applying stress in the opposite direction to the twisting direction, and then an insulating coating layer is applied to the outside.

In the method of the present invention, when hard copper wire is used as the wire in the wire twisting step, a compression step is performed to apply stress in a direction that offsets the residual stress due to manipulation on the surface of the hard copper wire. In this process, the surface stress of the hard copper wire is significantly reduced, and in this process, the strands are processed to impart compressive residual stress to the surface of the stranded wire, thereby significantly increasing stress corrosion cracking resistance.

Furthermore, by repeating this process several times, not only will the above characteristics be further improved, but the conductor will become more steel-tight due to the circular compression, making it possible to suppress the intrusion of rainwater etc. from the terminals of the insulated wire. It is something to be boiled. In addition, in the above compression process, the processing rate using a cold forging machine is preferably about 2 to 5%.
The number of passes is preferably three.

As described above, in the method of the present invention, it is sufficient to introduce the twisted conductor into a cold forging machine that rotates in the opposite direction at least once and perform untwisting and compression processing at the same time. It does not necessarily have to be the first time; it may be passed first through a forward-rotating cold forging machine and then subsequently through a reverse-rotating cold forging machine.

That is, in the method of the present invention, a plurality of forward-rotating cold forging machines and a plurality of reverse-rotating cold forging machines can be used in tandem, and there is no particular restriction on their order. In short, at least one counter-rotating forging machine may be used. Next, examples of the method of the present invention will be described.

Example 1 7 strands of 2.60 hard steel wires were twisted together and the 38-grade hard copper wire (7/2.6) (outer diameter 7.8? The outermost layer was twisted to the right) was passed through a right-handed rotating cold forging machine. The outer diameter was set to 7.60, and then passed through a left-rotation cold forging machine to have an outer diameter of 7.40.
After passing through a right-rotating cold forging machine to form a 7.20 overhead stranded conductor, an insulating layer of polyvinyl chloride (
Thickness 2. An overhead insulated wire of the present invention was obtained by covering the wire with a wire.
Example 2 19 2.30 hard copper wires are lacquered together to make 80 hard copper wire (19/
2.3) (outer diameter 11.50 outermost layer right-handed twist) was passed through a left-rotating cold forging machine to reduce the outer diameter to 11.2? Then, it was made to pass through a right-handed rotating cold forging machine to have an outer diameter of 11.00 mm, and then passed through a left-handed rotating cold forging machine to have an outer diameter of 10.80 mm, and an insulating layer of cross-linked polyethylene ( thickness 2
．． 1 side) to obtain an overhead insulated wire of the present invention.

Example 3 19 3.20 hard steel wires are twisted together to make a 150 fence hard copper wire (1
9/3.2) (outer diameter 16.0, outermost layer right-twist) was passed through a right-handed rotating cold forging machine to give a diameter of 15.80, and then passed through a left-handed rotating forging machine to reduce the outer diameter. 15.6◇, and then passed through a right-handed cold forging machine to have an outer diameter of 15.40, and then a hollow polyethylene insulation layer (thickness 2.5
The overhead insulated wire of the present invention was obtained by applying the above-mentioned ribs.

In addition, in order to compare with the overhead insulated wire of the present invention, an overhead insulated wire was prepared using the secondary method, that is, in the case of a conductor size 38 fence, after twisting seven 2.60 hard copper wires using a wire twisting machine, The outside is coated with a polyvinyl chloride insulating layer (thickness: 2.0cm), and in the case of a conductor size of 80, 19 hard copper wires are twisted using a stranding machine. The outside is covered with an insulating layer of polyvinyl chloride (thickness 2.1 mm),
In the case of a conductor size of 150 squares, 19 3.2◇ hard copper wires are twisted using a wire twisting machine, and then the outer periphery is covered with an aerial polyethylene insulation layer (thickness 2.5 side).

In order to conduct a stress corrosion cracking test on the overhead insulated wires obtained by the method of the present invention and the overhead insulated wires obtained by the conventional method, they were wrapped around PVC pipes 20 times the diameter of various conductors, and the cracks in the Iso copper wires were measured. The time was measured.

The results are shown in Table 1. The test method was to wrap each PVC pipe with a diameter 20 times the diameter of the conductor for 5 evenings each day.
9), a heat cycle of 80 and 20 qo (1 cycle twice) is performed, and the time taken until the hard copper wire breaks is shown.

Table 1: In the overhead insulated wires manufactured by the method of the present invention, no cracks occurred in the conductor even after 2000 hours.

Claims (1)

[Claims] 1. An aerial conductor with a desired number of conductors twisted around the outer periphery of the center conductor is introduced into a cold forging machine that rotates in the opposite direction to the direction in which the conductors are twisted, and while applying stress in the direction opposite to the direction in which the conductors are twisted, A method for producing an overhead insulated wire, which is characterized by compression molding into a circular shape and then providing an insulating coating layer on the outside thereof.