JPH0130243B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a steel-core aluminum stranded wire that suppresses corona discharge during ultra-high voltage power transmission.

"Prior art and its issues" Ultra-high voltage power transmission lines are required to reduce audible noise and power loss caused by corona discharge, and when power transmission lines are installed near residential areas, Audible noise can become a pollution.

During rainy weather, if raindrops adhere to the surface of a power transmission line, the potential gradient near the raindrops, which are good electrical conductors, increases, making corona discharge more likely to occur.

Conventionally, as a method to suppress corona discharge from high-voltage power transmission lines, a band-shaped body is wound spirally around the surface of steel-core aluminum stranded wires (hereinafter abbreviated as ACSR), and the band-shaped body is placed under the power transmission line. A technique has been considered to reduce the number of locations where the potential gradient is high by concentrating raindrops on a part of the ACSR, but if the surface of the strip as well as the surface of the ACSR changes due to chemical contamination, the raindrops may The effect of concentrating on the lower side may gradually decrease, and even in dry conditions.
Problems such as the band-shaped body protruding from the ACSR increased the potential gradient and caused corona discharge. Another method is to use forced corrosion, for example oxidation, on the surface of ACSR wires to increase its affinity with water and reduce the phenomenon in which raindrops become granular. However, this technique also has the disadvantage that its effectiveness decreases due to chemical contamination of the surface, and its effectiveness diminishes when there is a large amount of precipitation.

This invention was made in consideration of the above background, and its purpose is to provide a semiconducting layer on the outside of the aluminum stranded wire layer on the steel core to smooth the potential gradient on the ACSR surface and reduce the corona discharge energy. can be absorbed by a semiconducting layer to reduce audible noise, etc.
It attempts to provide ACSR.

"Example" Hereinafter, an example of the steel core aluminum stranded wire according to the present invention shown in FIG. 1 will be described.

As shown in the cross-sectional view in Fig. 1, the steel core aluminum stranded wire has an aluminum stranded wire layer 2 that conducts current on the steel core 1, and a carbon fiber-containing synthetic resin, for example, on the aluminum stranded wire layer 2. A semiconductive strand twisted layer 3 made by twisting semiconductive strands of strands such as A metal stranded wire layer 4 made of aluminum, for example, which does not pass current through, that is, is not intended for power transmission, is provided in a non-contact state with respect to the aluminum stranded wire layer 2, and the semiconductive stranded wire layer 3 is set such that its radial thickness dimension ensures the above-mentioned non-contact state.

In ACSR having such a configuration, power is transmitted through the aluminum stranded wire layer 2, and at this time, the aluminum stranded wire layer 2 and the outermost metal stranded wire layer 4 are not at the same potential due to short circuit or the like. , the potential of the outermost metal twisted wire layer 4 is expressed as the product of the potential difference between the aluminum twisted wire layer 2 and the ground and the proportional division ratio of impedance. If no corona discharge occurs, the metal stranded wire layer 4 and the aluminum stranded wire layer 2
The composite impedance of the part where the capacitance between the metal wire layer 4 and the resistance value of the semiconductive wire twisted layer 3 are connected in parallel is compared to the impedance due to the capacitance between the metal twisted wire layer 4 and the ground. Since it is very small, the potential of the metal stranded wire layer 4 is approximately equal to the potential of the aluminum stranded wire layer 2.

On the other hand, if a large number of raindrops adhere to the surface of the twisted metal wire layer 4 and the potential gradient near the raindrops increases, causing corona discharge, this corona discharge energy is transferred to the surface of the twisted metal wire layer 3. Supplied via a composite impedance. If there are many locations where corona discharge occurs and the corona discharge current value increases, the energy consumption due to the resistance value of the semiconductive wire twisted layer 3 will rapidly increase in proportion to the square of the increase in corona discharge current. This acts in the direction of cutting off the supply of corona discharge energy.

In this case, if rainwater enters between the strands of the metal stranded wire layer 4 of the ACSR, depending on the amount of raindrops, it may enter the semiconductive wire stranded layer 3 and then the aluminum stranded layer 2 inside it. Also, the number of raindrops on the surface of the twisted metal wire layer 4 is reduced. On the other hand, there is a phenomenon in which water in the vicinity is evaporated and released upward through the strands due to resistance heat generation caused by a corona discharge current flowing through the semiconductive wire twisted layer 3, Moisture that collects in the strands near the bottom of the twisted semiconductive wire layer 3 due to the action of attraction is a type of resistor that has conductivity, so it lowers the low resistance value of that part. It is expected that a phenomenon will occur where the corona discharge current is concentrated and the amount of heat generated on the lower side becomes relatively large and removed.

It goes without saying that the resistance value in the thickness direction of the twisted semiconductive wire layer 3 is increased so that the voltage drop in this portion is within the range of dielectric strength. In addition, at this time, since the power factor of the corona discharge current is considered to be approximately 1, the potential of the metal stranded wire layer 4 is a voltage drop from the potential of the aluminum stranded wire layer 2 to the voltage of the semiconductive wire stranded layer 3. This is the approximate value after subtracting the minute.

"Effects of the Invention" In this way, in this invention, the aluminum stranded wire layer on the steel core shares the power transmission, and the corona discharge current is transmitted from the aluminum stranded wire layer to the semiconductive strands twisted outside the aluminum stranded wire layer. The energy of corona discharge is proportional to the square of the corona discharge current based on the fact that the semiconducting stranded wire layer is a resistor in order to follow the path flowing from the layer and the twisted metal wire layer into the air. Even if rainwater enters the inside of the ACSR, steam is released from the strands due to the resistance heat generation of the semiconductive stranded wire layer. The amount of rainwater dripping and the number of raindrops can be reduced.

In addition, the above-mentioned semiconductive wire twisted layer is not directly exposed to the high stress of the outermost layer of ACSR, and in other words, the semiconductive wire twisted layer is protected by the outer metal twisted wire layer. Therefore, it will not deteriorate due to sunlight, etc., or cause mechanical damage due to direct external force.

Furthermore, since the entire steel-core aluminum stranded wire is made of wire rod, it can be easily manufactured using a stranding technology that applies a normal stranded wire manufacturing line.

[Brief explanation of drawings]

FIG. 1 is a partially omitted schematic cross-sectional view showing an embodiment of the steel-core aluminum stranded wire according to the present invention. 1... Steel core, 2... Aluminum stranded wire layer, 3... Semiconductive element wire stranded layer, 4... Metal stranded wire layer.

Claims (1)

[Claims] 1 A semiconductive stranded wire layer 3 having an annular shape and a thickness in the radial direction is provided on the outer side of the aluminum stranded wire layer 2 on the steel core 1, and further outside the aluminum stranded wire layer 2. Metal stranded wire layer 4 in a non-contact state
A steel-core aluminum stranded wire characterized by being provided with.