JPH0254008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in overhead power transmission and distribution lines used in cold regions, and particularly to a snow melting system for overhead power lines capable of melting accumulated snow and ice.

In cold regions such as Northern Japan and Ura Japan, snow and ice accumulate on overhead transmission and distribution lines during the winter, and this grows to a considerable size, leading to an increase in the weight of the wires and wind pressure loads between the tower spans. This often leads to accidents such as increased slack in the wires, breakage of the wires due to excessive tension, and even the collapse of the steel tower. In addition, if ice and snow fall in the form of blocks, it not only poses a danger to people passing under the overhead wires, but even if the area under the overhead wires is agricultural land, it may cause damage to crops, vinyl houses, etc., causing a major social problem. Therefore, a solution to this problem is desired.

For this reason, the methods known to date to prevent snow buildup are methods such as temporarily transmitting large currents to melt the snow by the heat of the conductor, and attaching ring-shaped objects to power transmission lines to allow snow to fall off. However, the former method is subject to restrictions on power system operation and cannot be implemented freely.
The effectiveness of the latter method differs depending on the type of ice and snow that adheres to power lines, and furthermore, if a grown block of ice and snow is simply dropped, there is no possibility of a secondary disaster depending on where it falls. I don't.

For this reason, it is possible to wrap a sleeve made of magnetic material, a linear body processed into a spiral shape, tape, or a rod around the AC power transmission line, so that the AC magnetic field caused by the power transmission current passes through the sleeve, etc. A method of melting the magnetic material using heat loss due to hysteresis loss and eddy current loss has been proposed, but heat generation from the magnetic material at a temperature where freezing and snow does not occur will increase power transmission loss. Therefore, it is desirable to use a material with a low Curie point, which reduces its magnetic properties and does not generate heat at high temperatures.

However, even when a magnetic material with such a low Curie temperature is used, unnecessary heat generation cannot be reduced sufficiently at room temperature if it is constantly wound around the surface of the wire.

As a result of various studies, the present inventor has provided a snow melting system for overhead power transmission and distribution lines that solves the above-mentioned difficulties by using a filament made of a shape memory alloy in combination with a magnetic material.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an example of a magnetic element used in the present invention, which includes a hollow cylindrical magnetic layer 1 made of a low-Kyrie material, and a hollow cylindrical conductive layer 1 of low conductivity such as aluminum closely adhered to the outside of the magnetic layer 1. This is a magnetic element 3 consisting of 2. FIG. 2 shows that a magnetic element-attached shape-memory alloy filament 5 is constructed by continuously inserting such magnetic elements 3 into a shape-memory alloy filament 4 in the form of beads. ing.

3 and 4 are front views illustrating the snow melting system for overhead electric wires of the present invention. Note that the magnetic element-attached shape memory alloy filament is shown by a line in these figures, but it is specifically as shown in FIG. 2.

First, FIG. 3 shows a state in which a magnetic element-attached shape memory alloy wire body 5 is spirally wound around an overhead electric wire 6 at a temperature of around 0° C. with a pitch P ₀ .

The radius of the helix is ρ ₀ .

When snow or ice accretes on such electric wires, naturally the snow melting action occurs quickly due to the heat generated by the magnetic elements that are in close contact with the overhead electric wires 6, and the temperature of the overhead electric wires rises. However, in FIG. 3, the magnetic element 3 is inserted into a shape memory alloy wire body 4 that relaxes and deforms when it reaches room temperature. As a result, the close contact between the magnetic element 3 and the overhead electric wire 6 may be broken, the winding pitch may become larger, or a combination thereof may occur.

The state is as shown in FIGS. 4a, b and c. First, in FIG. 4, the shape memory alloy filament 5 with the magnetic element attached thereto is heated to room temperature,
It shows a state in which the winding pitch or the winding radius changes due to relaxation, and in Fig. 4a, compared to Fig. 3, when the pitch of the helix due to winding is P ₁ and the radius of the winding helix is ρ ₁ . , ρ ₁ ≫ ρ ₀ , ρ ₁ > ρ ₀ , and in Fig. 4b, the winding radius of the spiral has not changed compared to Fig. 3, and only the pitch P ₁ has become very large. A partial front view showing the case where ρ ₁ = ρ ₀ and ρ ₁ ≫ ρ ₀ , and also the pitch of the helix in Fig. 4c.
Both P ₁ and the radius ρ ₁ of the winding spiral are much larger than in FIG. 3, and this is a partial front view showing the case where ρ ₁ ≫ρ ₀ and ρ ₁ >>ρ ₀ .

If the deformation as shown in FIG. 4 occurs, the magnetic element 3 attached to the shape memory alloy filament 4 will be less likely to be in close contact with the overhead wire 6, thereby preventing unnecessary temperature rise of the overhead wire 6. It turns out.

Next, FIG. 5 is an explanatory diagram of the initial winding helical radius ρ ₀ , the radius ρ due to subsequent relaxation, the winding angle θ, and the pitch P of the magnetic element-attached shape memory alloy filament 5.

In such a case, the calorific value H per unit length of the magnetic element is approximately H=
It is expressed as cosθ/ρ. (θ: wrapping angle) where θ=tan ^-1 (P/2πρ) Therefore, if either ρ, θ or both ρ and θ increase, cosθ/ρ decreases, so ρ and θ at room temperature If the shape is memorized so that ρ and θ are larger than those around 0°C, that is, the shape memory alloy strands are ideally in a straight state at room temperature, the low Curie property of the magnetic material can be reduced. Combined with this, the amount of heat generated at room temperature can be significantly reduced compared to that at around 0°C.

In carrying out the present invention, the magnetic element 3 attached to the shape memory alloy filament can be moved even more smoothly by opening the outlet of the central hole at both ends, as shown in FIG. It will be.

In addition, by fixing one end or the center of the shape memory alloy wire to the overhead wire and leaving the rest free, the shape memory alloy wire becomes more likely to deform. There is an advantage that the relative movement distance between the spirally wound magnetic element-attached shape-memory filament and the overhead electric wire is smaller.

The shape memory alloy used in the present invention must of course have reversible shape memory properties, but in order to maximize the amount of heat generated at low temperatures (around 0°C), it is necessary to It is desirable to have magnetism with low Curie temperature characteristics and/or low conductivity.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a magnetic element used in the present invention, FIG. 2 is a perspective view showing an example of a shape memory alloy wire body equipped with such a magnetic element, and FIG.
The figure is a front view showing a state in which a shape memory alloy wire body equipped with a magnetic element is spirally wound around an overhead electric wire at around 0°C. Figure 5 is a front view showing three examples of structures when the temperature is increased; Figure 5 is an explanatory diagram of the winding angle, pitch, and radius of the shape memory alloy filament attached to the magnetic element; Figure 6 is another structure of the magnetic element. It is a longitudinal cross-sectional view showing an example. 1: Magnetic layer, 2: Low conductive conductor layer, 3: Magnetic element, 4: Shape memory alloy wire, 5: Shape memory alloy wire with magnetic element attached, 6: Overhead electric wire.

Claims (1)

[Scope of Claims] 1. A shape memory alloy wire body having the following characteristics, in which magnetic elements are attached in the form of beads on the surface of an overhead power transmission/distribution line, is wound with one end or the center thereof being fixed and the other end or both ends being free ends. A snow melting system for overhead power lines that is characterized by rotating. (1) The property that it maintains its shape when wound around an overhead wire at a predetermined pitch at a temperature around 0°C, and deforms into a relaxed state at room temperature.