JPS6148201B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to composite stranded wires such as steel-core aluminum stranded wires used in high-voltage power transmission lines. Composite stranded wires have traditionally been used as electric wires for overhead power transmission lines, and among them, steel-core aluminum stranded wires (hereinafter abbreviated as ACSR) are often used as a typical stranded wire, and play a major role in power transportation. has been achieved. However, in recent years, due to the need for large-capacity power transmission, the power transmission voltage has tended to be increased, and corona discharge has become a problem. For example, the transmission voltage
It has been pointed out that when the voltage reaches 1000KV, corona noise occurs due to corona discharge, especially immediately after rain. As a result of studying the above-mentioned problems, the present inventor found that the corona noise immediately after rain in composite stranded wires used as overhead power transmission lines is caused by the increase in surface potential gradient around the raindrops due to protrusions caused by raindrops on the surface of the stranded wires. As a result, corona discharge is generated, so if we improve the water leakage and drainage properties of the stranded wire surface as a solution, we can eliminate the water beads on the surface and thereby reduce the corona discharge. It was discovered that the occurrence of discharge can be prevented, leading to the present invention. The present invention will be described below as a representative example of composite stranded wires.
This will be explained using ACSR as an example. That is, the present invention has investigated various treatments for the surface of ACSR for the purpose of improving its water leakage and drainage properties, and (1) among the aluminum strands or aluminum alloy strands constituting at least the outermost layer of ACSR, 30% or more of the outer circumference of the strand is formed with three or more grooves continuously in the longitudinal direction of the strand, and (2) a hydroxide film is formed on the surface including the grooves of the strand that has these continuous grooves. ACSR that can reduce corona noise can be obtained by (3) forming a hydroxide film after roughening the surface of the wire. It was done. When three or more grooves are continuously formed on the outer periphery of an aluminum wire or an aluminum alloy wire in the longitudinal direction of the wire, the number, size, and shape of the grooves greatly affect the formation of water droplets. At the same time, it causes a large change in the tensile strength and vibration fatigue strength of the wire or ACSR. In the present invention, the number of grooves formed continuously in the longitudinal direction of the aluminum wire or aluminum alloy wire constituting at least the outermost layer of the ACSR on the outer periphery of the wire is defined as three or more.
In order to reduce corona noise, it is necessary to eliminate the hemispherical water droplets formed on the outer surface of the ACSR, but for this purpose, if three or more grooves are formed on the surface of the outermost wire, it is necessary to At least one groove appears on the outer surface of the wire surface exposed to the atmosphere, and its geometrical shape traps raindrops inside the groove, reducing the number of hemispherical raindrops on the ACSR surface and forming the groove. This is because moisture flows through the fibers and has excellent drainage properties. Further, the reason why the grooves provided in the wires of the outermost layer are formed in at least 30% of the number of wires constituting the outermost layer is that if the number is less than that, the above-mentioned effect cannot be fully expected. Next, the reason why the width of the opening of such a groove is set in the range of 0.1 to 2 mm is because if the width exceeds 2 mm, the water drainage becomes poor and the effect of reducing corona noise is lost. The same is true. Also, the depth of the groove is 2 to 25 times the thickness of the wire that forms the groove.
% range because if the depth is less than 2%, the shape of the groove will not appear, and if it is deeper than 25%, the vibration fatigue strength will decrease, causing practical problems. As for the shape of the groove, in addition to the U-shape 1 or the arc-shape 2 shown in the cross-sectional views of the wire S in Figures 1 and 2, a V-shape may also be used. The condition is appropriate. As described above, the present invention provides a stranded wire in which three or more grooves are continuous in the longitudinal direction of at least 30% or more of the number of aluminum strands or aluminum alloy strands constituting the outermost layer of the stranded wire. The first feature is that it is formed by A second feature of the present invention is that a hydroxide film is formed on the outer surface of the aluminum wire or aluminum alloy wire in which the grooves are formed. This hydroxide film is formed by steam treatment at 120°C or higher, or after roughening the outer surface, in water or steam at 90°C or higher. The reason why the steam treatment is specified at 120°C or higher is that it is possible to form a film in a shorter time, and because the treatment is performed at a high temperature, it produces a more stable film with more crystallinity than a film formed at a low temperature. This is because water leakage and drainage properties are improved, and corona noise is reduced. In addition, to form a hydroxide film by roughening the outer surface and then treating it in water or steam at a temperature of 90°C or higher, first roughening the surface by sandblasting, shotblasting, chemical conversion treatment, etc. Since the surface irregularities are increased and then a hydroxide film is generated, the surface area becomes larger due to the irregularities, and even if the hydroxide film formation conditions are the same as on a smooth surface, the amount of film formed is larger, and moreover, on a rough surface. The surface roughness after treatment is approximately doubled after the film is formed, and due to the synergistic effect of improving water leakage due to the hydroxide film and making the surface even rougher, the water leakage is extremely excellent. This is because it has excellent drainage properties and can reduce corona noise immediately after rain in a short period of time. Then, this hydroxide film can be applied to the surface including the grooves of the strands that should be the outermost layer, or it can be applied to the outer surface of the strands that have the grooves in the outermost layer of the stranded wires after the strands are twisted. No matter which one is adopted, the same effect can be obtained. In the present invention, 30% or more of the wires constituting at least the outermost layer of the composite stranded wire are aluminum wires or aluminum alloy wires having three or more grooves formed on the outer periphery. By forming the grooves, it is possible to reduce corona noise, which is the objective of the present invention. This also includes forming three or more grooves in the same way in all of the strands, thereby making it possible to make the composite stranded wire, such as ACSR, even lighter. In the present invention, the wire used in the center of the stranded wire is referred to as a core wire, but this includes all wires made of a single wire or a plurality of steel wires, aluminum wires, etc. As detailed above, the composite stranded wire of the present invention has at least three or more grooves continuous in the longitudinal direction of the strands formed on the outer periphery of 30% or more of the number of strands as the strands to be at least the outermost layer. The water leakage and drainage properties of the composite stranded wire can be improved by using a stranded wire, or a hydroxide film formed after surface roughening, or a hydroxide film formed after surface roughening.
Corona noise immediately after rain can be reduced in a short time. Furthermore, by using such grooved strands, thick wires are required due to corona characteristics when used for ultra-high voltage power transmission lines, but ACSR is optimal for cases where a large aluminum cross-sectional area is not required due to power transmission capacity. It is possible. Further, by providing such a groove, surface damage caused by the passing of the fishing wheel does not reach the inside of the groove, and the degree of deterioration of water leakage is extremely small, which is an excellent effect. The present invention will be explained in detail below with reference to Examples. Example 1 A heat-resistant aluminum alloy wire with an outer diameter of 4.8 mmφ was provided with U-shaped grooves at various depths as shown in Figure 1, and the vibration fatigue strength of this wire was examined, and the results shown in Table 1 were obtained.

[Table] From the table above, it was found that when the depth of the groove is 30% of the wire diameter, the vibration fatigue strength decreases, which is not practical when used as a stranded wire. Example 2 As shown in Fig. 1, the cross-sectional shape is U-shaped, the width of the opening is 1 mm, and the depth is 20% of the wire diameter4.
Outer diameter with grooves continuously formed in the longitudinal direction of the strand
810mm ² using 4.8mmφ aluminum wire for the outer layer
An ACSR with the same configuration as the ACSR was manufactured. This ACSR was subjected to various surface treatments as shown in Table 2, and then an audible corona noise test was conducted. Corona noise test is 1.6 assuming immediately after rain.
After water injection for 1 minute at a rainfall intensity of mm/hr, the maximum surface potential gradient was measured at 14.0 KV/cm. For comparison, we also measured a normal 810mm ² ACSR (No. 10). The measurement results were as shown in Table 2. The surface roughening was done by sandblasting.

[Table] From the above table, it was found that the ACSR according to the present invention has a 4 to 14 dB reduction in corona noise level compared to the conventionally used ACSR, and is highly effective.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an aluminum wire in which grooves are formed in the longitudinal direction for use in the present invention, and FIGS. 2A to D are cross-sectional views showing other examples of the number and shape of grooves formed in the aluminum wire. It is a diagram.

Claims (1)

[Scope of Claims] 1. In a composite stranded wire having a structure in which aluminum strands or aluminum alloy strands are twisted on a core wire, at least 30% or more of the number of aluminum strands or aluminum alloy strands constituting the outermost layer thereof. A composite stranded wire characterized in that three or more grooves are continuously formed in the longitudinal direction of the wire on the outer periphery of the wire. 2. Claim 1, characterized in that a hydroxide film is provided on the groove-containing surface of an aluminum strand or aluminum alloy strand, which has three or more grooves continuously formed in its longitudinal direction on its outer periphery. Composite stranded wire as described in section. 3. A patent claim characterized in that a hydroxide film is provided on the groove-containing surface of an aluminum strand or aluminum alloy strand, which has three or more grooves continuously formed on its outer periphery in its longitudinal direction. range 1
Composite stranded wire as described in section. 4. The composite stranded wire according to any one of claims 1 to 3, wherein the width of the opening of the groove is 0.1 to 2 mm. 5. The composite stranded wire according to any one of claims 1 to 3, wherein the depth of the groove is 2 to 25% of the thickness of the strand.