JPH0135447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to an overhead power line intended to largely suppress vibrations caused by wind pressure in an overhead power transmission line, an overhead ground wire, an overhead power distribution line, or the like.

Electric wires used as overhead lines for steel towers or telephone poles are constantly exposed to wind pressure, and as a result of this, the electric wires themselves constantly generate so-called slight wind vibrations. For this reason, electric wires undergo vibration fatigue over many years, which not only causes strand breakage but also, in the worst case, even leads to disconnection of the electric wire itself due to fatigue breakage.

In order to prevent such situations from occurring, the strength of the wires is strengthened and vibration isolators (so-called dampers) are installed separately, but copper and aluminum used as conductors are inherently too strong. However, if you try to increase this strength, the conductivity will drop drastically, and there is a limit to the strength improvement measures you can take.Although it is effective to install the damper described above, the damper may be the first to fail due to fatigue. In addition, the shape of the damper does not necessarily absorb all vibrations because the vibrations it absorbs have unique frequency characteristics.

Therefore, in order to enhance the vibration absorption effect of the electric wire itself, a gap type electric wire has been proposed in which a gap _W3 is formed between a steel core _W2 and an aluminum stranded wire _W1 as shown in FIG.

This is due to the vibration damping effect that depends on the Coulomb friction between the strands of the electric wire, as well as the difference in natural vibration between the steel core W ₂ and the aluminum strands W ₁ , which cancel each other's vibrations and dampen the vibration. However, as can be understood from the structural point of view, it is difficult to twist the wires together with such gaps, and furthermore, the overhead wiring work for such electric wires is special and extremely complicated and difficult. There are many problems, such as the twisted wires are easily damaged and rainwater accumulates in the gaps, making them vulnerable to corrosion.

Furthermore, overhead distribution lines are coated with insulators, so rainwater easily enters from the tie-down parts, etc., and once it does, there is no escape, and if slight wind vibrations are applied in this state, it can rapidly It is also known that stress corrosion progresses and the wire becomes fragmented and disconnected. Moreover, an effective vibration isolator for such overhead power distribution lines has not yet been developed.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an epoch-making electric wire that can significantly reduce the slight wind vibration of the electric wire.

[Summary of the Invention] The reason why the electric wire causes slight wind vibration is that the input energy due to the wind is greater than the absorbed energy of the electric wire.

The damper described above is based on the idea that adding an additional object increases the absorbed energy and increases the overall vibration absorption power to prevent vibrations, but the present invention This is based on the opposite idea, and by making the outermost layer of the wire a special shape and changing the flow of air fluid around the wire, it is possible to significantly reduce the power lift coefficient due to wind. This is a device that prevents the generation of vibration itself by significantly reducing the input energy that is converted into vibration.The gist of this is to extend the outermost shape of the wire in the longitudinal direction. Do 1
When formed to have a pair or two pairs of protruding parts and non-protruding parts, the outer diameter of the protruding part is D, its central angle is θ, the outer diameter of the non-protruding part is d, and its central angle is ψ. In addition, the structure is such that 15°≦θ≦45° D/d≧1.05.

[Example] FIGS. 2 and 3 are cross-sectional views showing two examples of the anti-vibration electric wire 10 according to the present invention.
The figure shows the case of a fan-shaped segment element steel core aluminum stranded wire, and FIG. 3 shows the case of an overhead distribution line.

In FIG. 2, the strands of the outermost layer strands are mixed and twisted into a thicker strand 3a and a thinner strand 3b in the radial direction of the electric wire 10.
Two pairs of protruding portions 1 and non-protruding portions 2 extending in the longitudinal direction of the electric wire are formed on the outermost periphery of the electric wire. In addition, FIG. 3 shows that when applying insulation coating 4 to electric wires, by making the inner surface shape of the die a special shape,
A protruding portion 1 and a non-protruding portion 2 are formed on the outermost periphery of an electric wire 10.

The formation of such protruding portions 1 and non-protruding portions 2 causes a change in the air fluid flowing on the outer surface of the electric wire 10, and as a result, uniform separation of the air fluid from the electric wire surface is inhibited, and as a result, wind pressure causes a change in the air fluid flowing on the outer surface of the electric wire 10. As a result, the lift force generated on the wire is greatly reduced, and the energy input to the wire is significantly reduced.

In other words, the input energy Pw to the wire due to wind
is theoretically expressed by equation (1).

Pw=f ³・D ⁴・η・CL・Q ...(1) Where f: Vibration frequency D: Outer diameter of electric wire η: B/D (B: Vibration amplitude) CL: Dynamic lift coefficient Q: Constant Therefore, as is clear from the above equation, it can be seen that in order to reduce Pw, it is sufficient to reduce the dynamic lift coefficient CL. Therefore, the dynamic lift coefficient CL can be expressed by equation (2).

CL(r・m・s)=(Wsinωt)/1/2(ρ・v ²・
A) ...(2) where ρ: density v: wind speed A: cross-sectional area W: load ω: angular velocity (=2πf f: frequency) t: time The inventors used a large wind tunnel with an opening of 500 mm x
The test wire is supported by a spring system at the central horizontal position 30 cm in front of the 500 mm air outlet, and a load cell is attached to the end of the test wire outside the air path to measure the load W on the test wire caused by wind pressure. The dynamic lift coefficient CL was determined from this measurement.

Regarding the dimensions and shape of the electric wire 10 according to the present invention,
As the outline is schematically shown in FIG. 4, the following conditions were selected: the outer diameter D of the protrusion 1, the central angle θ, the outer diameter d of the non-protrusion 2, and the central angle ψ.

Figure 9 shows a projected cross-section approximately equivalent to 150mm ² ACSR using a conventional 150mm ² ACSR (steel core aluminum stranded wire) and a segmented wire ACSR as shown in Figure 2 as the electric wire of the present invention. This figure shows the results of a tunnel experiment with electric wires made of

A very remarkable reduction in the lift coefficient was observed in the electric wire according to the present invention, and it can be clearly seen that the input energy, which is a source of vibration to the electric wire, is greatly reduced.

Figure 10 shows the wind speed 19 for the same test material as in Figure 9.
This is the result of measuring vibration acceleration in m/S. In the case of the electric wire according to the present invention, the vibration acceleration is greatly reduced to about one-fifth of that of the conventional type, and it can be seen that the amplitude level during vibration is significantly reduced.

As mentioned above, by forming protruding parts and non-protruding parts in the longitudinal direction of the electric wire (either parallel or spiral), the input energy based on wind pressure to the electric wire itself is extremely reduced, and the occurrence of vibration can be greatly suppressed. However, the conditions for forming the protruding portions and non-protruding portions are not limited to any conditions.

Figure 7 shows the results of measuring the lift coefficients CL of electric wires according to the present invention configured as D = 21 mm, d = 19 mm, and ψ = 30°, with various θ selected. The ratio C to the lift coefficient CL of 150mm ² ACSR was determined and prepared.

As is clear from FIG. 7, the vibration prevention effect decreases whether θ is small or large. This is θ
This is thought to be due to the fact that the effect of changing the flow of air fluid exerted by the step surface of the electric wire becomes smaller whether it becomes smaller or larger. We conducted various experiments using various test materials, and the trends were similar to those shown in Figure 7.Even when ψ is larger than 30°, the optimal range of θ is approximately 15°≦θ. It was found that ≦45°.

Furthermore, regarding ψ, if ψ becomes too small, the step effect disappears, and when θ and ψ are calculated as a ratio, it has been found that various experiments show the tendency shown in Figure 8. did.

That is, for θ, there is an appropriate range of 15°≦θ≦45°, but for ψ, the experimental results show that there is almost no difference in effectiveness except for very small angles.

Furthermore, the size of the level difference between the protruding portion and the non-protruding portion is, of course, a factor that directly acts to change the flow of the air flow.

FIG. 11 shows the degree of the level difference by the ratio of D/d, and plots the relationship between D/d and the lift coefficient CL. The figure shows the case where D = 20 mm and D = 30 mm are set, but the tendency is the same under other conditions, and the lift coefficient is determined when the level difference exceeds a certain value, that is, D/d≧1.05. It became clear that CL decreased significantly.

The tendency shown in FIG. 11 can be expressed as an experimental formula by the following equation (3) shown in the figure: 1.8exp{-(D/d)} . . . (3). In this case, the value of 1.8 may change slightly due to changing conditions, but it is essentially expressed in the above exponential relationship.

Therefore, one critical condition can be found at D/d≧1.05.

As described above, the overhead electric wire according to the present invention exhibits a remarkable anti-vibration effect depending on its own shape, so its anti-vibration behavior is fundamentally different from that of the conventional example. Of course, various modifications can be made to the shape, and although the effect can be achieved even with the configuration shown in Figures 5 and 6, considering the actual cross-sectional surface, the protrusion is Preferably, there are one or two pairs.

Furthermore, in the case of the above embodiment, the case where all the protrusions forming the stepped surface are constant, or the central angles θ and ψ are constant for one electric wire, these are the critical values in the configuration of the present invention. It goes without saying that a single wire may have a mixture of various values within the range. Furthermore, as long as most of the conditions are within the range of the critical conditions, it goes without saying that even if there are some deviations from the critical conditions, they are still within the scope of the technical idea of the present invention.

Further, the number of wires forming the protrusion does not need to be one.

[Relationship with Prior Application] The present inventors conducted similar experiments for the purpose of reducing the noise generated by electric wires, and published Japanese Patent Application No. 57-205846 (Japanese Patent Application Laid-Open No. 59-96603) regarding the optimal structure. issue)
A patent has been applied for.

This time, we proposed an optimal structure from the perspective of vibration prevention, but the range that achieves sufficient effects for both purposes is 40゜≦θ≦45゜ D/d≧1.05 D-d/2≧1mm I understand.

However, depending on the application, such as when you want to emphasize low noise effect or vibration prevention effect,
It goes without saying that configurations within the scope of each invention can be selected and implemented even if they deviate from the above ranges.

[Effects of the Invention] As described above, the electric wire according to the present invention has the following advantages: (1) Since the shape of the outermost periphery only needs to be configured to have a predetermined step, an insulated wire can be easily manufactured during sheath extrusion, and a stranded wire can be easily manufactured. Even if there is a problem, twisting is easy by choosing the strand configuration, so
It is easier to manufacture than conventional gap-type electric wires, and there are no special restrictions on overhead wiring work, and it can be easily installed using normal construction methods.

(2) Under the current overhead wire tension (20% of the breaking load), the value is much smaller than the current vibration isolation standard, so it is not necessary to install the damper (or the width can be significantly reduced). This eliminates the need for damper installation and subsequent maintenance work, resulting in extremely large labor-saving effects.

(3) Under the current vibration isolation standards, the overhead wire tension is increased by the amount of input energy that reduces fatigue strength, which makes it possible to use high-tension overhead wires, which reduces sag and allows the tower to be lowered. The cost of constructing steel towers can be drastically reduced.

The benefits it brings to industry are extremely large.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional gap type electric wire, Figure 2
3 is a cross-sectional view of the electric wire according to the present invention, FIG. 4 is a schematic diagram showing the outline of the electric wire according to the present invention, FIGS. 5 and 6 are explanatory diagrams showing experimental examples leading to the present invention, and FIG. Figure 8 is a diagram showing the effect of the central angle of a protruding part on the lift coefficient. Figure 9 is a diagram showing the difference between the conventional wire and the wire of the present invention in terms of lift coefficient, Figure 10 is a diagram showing the difference between the conventional wire and the wire of the present invention with respect to vibration acceleration, and Figure 11 is a diagram showing D/d and lift force. FIG. 3 is a diagram showing the relationship with coefficients. 1: protruding portion, 2: non-protruding portion.

Claims (1)

[Claims] 1. Extending the shape of the outermost periphery of the electric wire in the longitudinal direction 1.
When formed to have a pair or two pairs of protruding parts and non-protruding parts, the outer diameter of the protruding part is D, its central angle is θ, the outer diameter of the non-protruding part is d, and its central angle is ψ. An overhead electric wire configured such that 15°≦θ≦45° D/d≧1.05.