JPH0347216Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Technical Field of the Invention) The present invention relates to the improvement of overhead ground wires, which prevents wire breakage of overhead ground wires due to direct lightning strikes, reduces wind noise,
This invention relates to lightning-resistant electric wires that are useful in cases where it is possible to prevent snow from accreting. (Technical background of the idea and its problems) Generally, in overhead power transmission lines, an overhead ground wire is installed at the top of the support to prevent direct lightning strikes to the power source. It is designed to catch direct lightning strikes and send lightning current to the ground via supports. Conventionally, as an overhead ground wire, for example, a steel core aluminum stranded wire formed by twisting aluminum wires on a steel core is known. Incidentally, wire breaks have recently occurred in overhead ground wires, and it has recently become clear that the cause of the breakage is arc fusing caused by direct lightning strikes. Therefore, if a wire breakage occurs in the aluminum wire of an overhead ground wire due to a direct lightning strike, the functional and electrical characteristics of the overhead ground wire may be affected.
This may lead to a decrease in mechanical properties, and in some cases, a very large lightning current may cause arc-fusion of the entire wire, which could lead to a serious accident. For this reason, on the outer periphery of an overhead wire made of a steel-core aluminum stranded wire whose entire length is divided into multiple sections, a melting body made of a metal body formed in advance in a spiral shape is attached to the entire outer periphery of the overhead wire for each section. Lightning-resistant electric wires are provided in which the wires are wrapped closely together so as to cover the wires. Here, the structure and effects of the above-mentioned lightning-resistant electric wire will be explained. In Figure 1, this lightning-proof wire is the overhead ground wire 1.
The wire is mainly composed of an overhead wire made of wires, etc., and a erosion layer 2 provided on the outer periphery of the wire. The overhead ground wire 1 is composed of a steel core 3 made of twisted steel wires, and an aluminum conductive layer 5 made of a plurality of twisted aluminum wires 4 having a trapezoidal cross section twisted around the outer periphery of the steel core 3 into a cylindrical shape. . Next, the reason for providing the erosion layer 2 will be described. According to the lightning simulation arc test carried out by the present inventors, it has been found that strand breakage due to fusing does not occur due to impulse waveform current alone, but occurs due to direct current following the impulse current. The table below shows aluminum wire and steel wire samples (3.5
This shows the results of a test to see if there would be fusing when an impulse current and direct current simulating a direct lightning strike were applied to a single wire (with a tension of 20% of the tensile load applied to the wire), and the effect of this test was according to,
With only impulse current, only traces of melting were observed on the surface of all the samples, indicating that direct current was responsible for the melting. On the other hand, only aluminum wire systems can be fused with direct current, and the samples differ (aluminum, aluminum alloy,
There is no difference depending on the presence or absence of plating, and all of them are fused. On the other hand, steel wires are subject to melting loss, but do not break out. This seems to be due to the fact that the aluminum wire system melts due to its low melting point, based on the results of investigations into melting damage energy and the like.

[Table] From the above experimental results, an overhead ground wire made of steel-core aluminum stranded wire is likely to melt if a long-duration direct lightning strike hits it, but the melting point of the aluminum itself is higher than that of steel wire. Because of its relatively low melting point, it is almost impossible to make aluminum itself arc resistant with a high melting point. Therefore, in this lightning-resistant electric wire, a frayed layer is formed on the outer surface of the overhead ground wire, and when a direct lightning strike occurs, only the frayed layer is fused, and the overhead ground wire inside the main body is protected from the initial electrical damage. The properties and mechanical properties are intended to be maintained permanently. As shown in FIG. 2, the erosion layer 2 includes a erosion body 6 made of a metal body such as an aluminum alloy wire preformed on the outer periphery of the overhead ground wire 1 whose entire length is divided into multiple sections 7. It is formed by tightly wrapping the material so as to cover the entire outer peripheral surface of the material. Note that the cross section of the melted body 6 is trapezoidal like the aluminum wire. This is because, compared to a normal overhead ground wire, the lightning protection wire has an extra erosion layer due to its structure, so it is necessary to reduce its external size accordingly. In other words, as the external shape increases, the overhead ground wire becomes heavier, and the mechanical strength of the support must be increased in proportion to this.
Therefore, the existing support cannot be used as it is. The erosion layer 2 is formed, for example, by connecting an overhead ground wire and then winding and attaching an erosion body 6 having a unit length of about 3 to 5 m in each section using a self-propelled spacecraft. Note that this erosion layer may be formed in advance on the outer periphery of the overhead ground wire in a factory. The reason why the melting layer 2 is provided in each section is to make it easy to replace the melted body 6 when several melted bodies 6 are cut off during arc melting. This is to prevent layer 2 from sharing the tension during the overhead wire. In other words, if several of the melted bodies 6 are broken due to arc melting caused by a direct lightning strike while the tension is shared in the melted layer 2, all the tension on the overhead wires will be transferred to the overhead ground wire, and finally This is because the overhead ground wire is disconnected. The inner peripheral surface of the melted body 6, that is, the surface in contact with the overhead ground wire 1, is formed with a radius of curvature corresponding to the outer shape of the overhead ground wire in order to be electrically connected to the overhead ground wire 1. (Disadvantages of conventional lightning-resistant wires) By the way, in lightning-resistant wires with this configuration,
The erosion layer 2 can be formed, for example, by installing an overhead ground wire and winding the erosion body 6 with a unit length of about 3 to 5 m in each section using a self-propelled spacecraft, or in a factory. It is formed by winding it around the outer circumference of the overhead ground wire in advance. However, in the former method, there are difficulties in forming the wire due to the overhead wire construction method, and in the latter method, there is a concern that the welded body may peel off during the passage of the wire rolling car or metal wheel during the overhead wire construction. In addition, in order to provide such electric wire with functions such as low wind noise and resistance to snow accumulation, a spiral rod or a ring is attached to the outer circumferential surface of the lightning-proof electric wire. However, there has been a problem in that it is complicated to attach such accessories after the lightning-resistant electric wire has been installed. (Purpose of the invention) The present invention was made with attention to these points, and aims to provide a lightning-resistant electric wire that is advantageous in manufacturing and overhead wiring construction methods and does not require the attachment of the above-mentioned accessories after the wiring is completed. It is. (Summary of the invention) In the invention, a melting body made of conductive metal wire is placed on the outer periphery of the overhead wire so as to cover the entire outer periphery of the overhead wire and in the twist direction of the outermost layer of aluminum wire constituting the overhead wire. The above object is achieved by winding the melting body closely in substantially the same direction as the melting body, and by forming protrusions on a part of the outer surface of the melted body. (Embodiment of the invention) Hereinafter, the invention will be explained based on the drawings of one embodiment. The same numbers are given to the same parts as in Figures 1 and 3, and in Figure 4, a melting layer 2' is attached to the outer periphery of the overhead wire consisting of the overhead ground wire 1 etc. so as to cover the entire outer peripheral surface of the overhead wire. The point that the winding is tightly wound is the same as that of the conventional lightning-resistant electric wire. In the present invention, the fusing layer 2' is provided without being divided into multiple sections, the twisting direction of the fusing body 6' is approximately the same as the twisting direction of the outermost aluminum wire 4 constituting the overhead wire, It is different from the conventional lightning-proof electric wire in that a single protrusion 8 having a protrusion of about 4 to 5 mm is formed on a part of the outer surface of the melted body 6'. That is, in the lightning-resistant electric wire according to the present invention,
The erosion layer 2' covers the entire outer periphery of the overhead wire and twists the erosion body 6' made of a continuous conductive metal wire in substantially the same direction as the twisting direction of the outermost aluminum wire 4 constituting the overhead wire. It is formed by winding it tightly. The cross-sectional shape of the melting body 6' formed of the same material as the aluminum wire 4 is trapezoidal with the aluminum wire 4, as shown in FIG. The surface in contact with is electrically connected to the overhead ground wire 1, so it is formed with a radius of curvature corresponding to the outer shape of the overhead ground wire. In the present invention, the twisting direction of the melting body 6' is made to be the same as that of the outermost aluminum wire constituting the overhead wire in order to increase the electrical contact area between the overhead wire and the melting body. This is because if the twisting direction of the outermost layer aluminum wire is opposite to the twisting direction of the melted body, the contact between the two will be a line contact, and the electrical connection between the two will be incomplete. In addition, in the overhead wire of the lightning-resistant electric wire according to the present invention, the tension is shared only with the overhead wire, and the tension is not applied to the erosion layer. In addition, the ability to reduce wind noise and prevent snow accretion to the lightning-resistant wire with the above structure is achieved by adding a part of the melting body 6′.
A protrusion 8 is formed in advance on the outer surface of the welding body 8, and this is simultaneously wound and tightly attached together with other fusing bodies 6 in a factory. Therefore, the presence of the protrusions prevents the occurrence of Karman vortices, and furthermore, it is possible to rotate the snow adhering to the lightning protection wire in the circumferential direction, thereby preventing the accumulation of snow from increasing. (Effects of the invention) As described above, in the invention, a conductive metal wire is tightly wound around the outer periphery of the overhead wire, covering the entire periphery of the overhead wire and in the same direction as the twisting direction of the outermost layer of aluminum wire. Therefore, it is easier to manufacture than conventional lightning-proof electric wires, and the wire can be easily installed without dropping the melted body. In addition, a protrusion is formed on a part of the outer surface of the erosion layer that makes up the lightning-resistant wire, which prevents the wires of the overhead ground wire from breaking due to direct lightning strikes, and also reduces wind noise and prevents snow buildup. It is possible to provide a lightning-resistant electric wire with the following functions. In addition, in the above-mentioned embodiment, only the case where the erosion layer is provided on the outer periphery of the overhead ground wire is described, but the present invention is not limited to this, and for example, even if the erosion layer is provided on the outer periphery of the power line. good.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional lightning-proof wire, Fig. 2 is a side view of the same, Fig. 3 is an end view of a melted body, and Fig. 4 is a cross-sectional view of a conventional lightning-proof wire.
The figure is a cross-sectional view of the lightning-resistant electric wire of the present invention, and FIG. 5 is a side view of the same. 1... Overhead ground wire, 2, 2'... Erosion layer, 6,
6'...Erosion body, 7...Section, 8...Protrusion.

Claims (1)

[Claims for Utility Model Registration] 1. A welding body made of conductive metal wire is placed on the outer periphery of the overhead wire so as to cover the entire outer periphery of the overhead wire and in the twist direction of the outermost layer of aluminum wire constituting the overhead wire. A lightning-proof electric wire, characterized in that the wires are tightly wound in substantially the same direction, and a protrusion is formed on a part of the outer surface of the melted body. 2. The lightning-resistant electric wire according to claim 1, wherein the cross-sectional shape of the outermost layer of aluminum wire constituting the melting body and the overhead wire is trapezoidal.