JPS58251B2 - Nanchiyakusetsu Densenno Densen Nejire Kaitenboushiken Gear Lopping Boushihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for preventing twisting of electric wires and gear roping, which are problems when using electric wires that are difficult to accumulate snow.

Conventionally, bare electric wire 1 as shown in Fig. 1 was used as a snow-resistant electric wire.
By attaching rings 2 at regular intervals along the longitudinal direction of the outer circumference of the electric wire, when snow accretes on the electric wire, the snow will rotate and develop while sliding in the direction of the twist of the electric wire, but the rings 2 will serve as a stopper. There are things that encourage snowfall and prevent snow from developing into a tube shape.

However, when the electric wires with difficult snow accumulation are installed in a long span area, the electric wires themselves twist due to the eccentric load of the accumulated snow before the snow on the electric wires rotates. It became clear that it appeared to be rotating around the electric wire, and that it developed into a pipe of snow.

In addition, during strong winds, ice and snow adhering to the wires make the wires aerodynamically unstable, causing gear lopping.

In the present invention, the basic frequency refers to the frequency at which the electric wire installed on the support mass performs one loop motion on the support mass.

The present invention aims to solve these problems, and one embodiment thereof will be described in detail below with reference to the drawings.

FIG. 2 shows a state in which the objects 3 of the present invention are fixed near the center of the span of the snow-resistant electric wire 1 having rings 2 at regular intervals in the longitudinal direction of the outer circumference.

Note that 4 is a steel tower.

Hereinafter, the object 3 of the present invention will be referred to as a damper.

An example of the structure of the damper 3 is shown in FIG. 3.

FIG. 3 is a side view of the damper fixed to the snow-resistant electric wire, which is composed of a wire gripping portion 3A, an upper shaft 3B, a lower shaft 3C, an upper weight 3D, and a lower weight 3E.

In addition, the lengths of the shafts 3B and 3C and the weights of the weights 3D and 3E are appropriately selected so that the center of gravity 3F of the damper is below the wire gripping part 3A, and the twisting rotational frequency of the wire is reduced to vertical vibration. to a non-integer multiple of less than three times the fundamental frequency.

The torsional rotation frequency in this case can be determined by the following formula.

Where, f: Torsion rotation frequency (Hz/Sec) m: Mass of damper (kg) h: Distance between the center of the wire and the center of gravity of the damper (m) I: Coefficient of inertia of the damper (kg-m2) GIP: Torsion of the wire Rigidity (kg-m3/Sec
) K: Installation of the damper is a constant determined by the number of cylinders and the position (for example, 4 when installed at the center of the span) g: Acceleration of gravity (m15ec2) l: Span length (m) The present invention is configured in this way. Therefore, when this is used on an actual line, even if snow accumulates on the wire and the wire is about to twist, the center of gravity of the damper 3F is below the wire gripping part 3A, so a rotation restraining force is generated. This prevents the electric wire from twisting, and brings about the effect of fully demonstrating the original function of the snow-resistant electric wire.

Furthermore, gear roping can be prevented by the principle described below.

Gear lopping of overhead power lines is shown in Figure 4 as one loop of motion C.
Although the motion has 12 loops and the motion E has 3 loops, there are cases where the number of loops is larger than this, and cases where the movement is in the form of a traveling wave.

Furthermore, in Fig. 4, the maximum amplitude when gear lopping occurs is the largest in the amplitude aC of the first loop, followed by the amplitude aD of the second loop, and the amplitude aE of the third loop, and the larger the number of loops, the smaller the maximum amplitude. Become.

The reason for this is that the change in elongation of the wire due to changes in wire tension is small, so if this is ignored, the length of the wire I between the towers 4 is almost constant, so the larger the number of loops, the smaller the maximum amplitude will be limited. It is in.

FIG. 8 is a cross-sectional view of the power transmission line when gearropping occurs, and shows that the smaller the amplitude, the less the wires approach or collide with each other, and the fewer short-circuit accidents occur.

In practical power transmission lines and distribution lines, many accidents occur when gear ropping has a long loop length of three loops or less.

Further, the frequency of the vertical movement of the electric wire I in the case of one loop matches the fundamental frequency of the vertical movement.

The fundamental frequency fC of the vertical movement of the electric wire I is calculated by considering the electric wire I as a string, the weight of the electric wire is WC (kg/m), and the electric wire tension is T (k
g), it is expressed as.

The frequency of the vertical movement of the electric wire I in the case of two loops is twice fc, and in the case of three loops, it is three times.

Since damage caused by gear lopping is most likely to occur when the loop length is long (3 loops or less), reducing the frequency of torsional rotation to a non-integer multiple of less than 3 times the fundamental frequency of vertical motion will prevent gear lopping. This can be expected to prevent accidents.

The reason why a non-integer multiple was selected above is that if it were an integer multiple, the vibration nodes of the torsional rotation and the vibration nodes of the vertical motion would match, creating a resonance state and eliminating the gear roping suppressing effect.

Next, a specific means for obtaining a non-integer multiple of 3 or less loops will be described.

In Figure 3, the mass of the upper weight 3D is mD (kg),
Assuming that the mass of the lower weight 3E is mE (kg), the length of the upper shaft 3B is rB (m), and the length of the lower shaft 3C is rC (m), the inertia factor of the torsional rotation prevention damper is I (kg-m2 ) becomes I=mD・rB2+mErC2.

Also, if m≒mD+mE, then the torsional rotational frequency (Hg/sec) will be, and each mass of the upper weight 3D, lower weight 3E, and upper shaft 3
B. By appropriately changing the length of each axis of the lower axis 3C,
The torsional rotational frequency f can be selected to be a non-integer multiple of less than three times the fundamental frequency fc of vertical motion.

Note that 13 to 1f in the figure indicate loci of gearropping vibrations of the overhead electric wires a to f.

The number of cylinders required for the span of damper 3 depends on the thickness of the electric wire, the span length,
It may be selected depending on the weight and inertia rate of the damper 3.

In addition, the damper 3 should be installed in an asymmetrical position to avoid points F and G in Figure 4, which are the nodes of 3 or less loops, and to prevent standing wave loops from forming. .

Note that the present invention is applicable not only to the case where there is only one electric wire that is difficult to accumulate snow;
Of course, it can also be applied to the case of two articles as shown in Figure 5, or to the case of more articles.

Furthermore, it goes without saying that the same effect can be obtained by changing the shape of the damper 3 to a horizontally mounted shape as shown in FIG.

Furthermore, it goes without saying that the present invention can also be applied to a snow-resistant covered electric wire 6 having protrusions 5 used in the distribution line shown in FIG.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and Fig. 1 is an enlarged view of the main parts of the snow-resistant electric wire, Fig. 2 is a front view showing the state of use, Fig. 3 is an enlarged view of the damper, and Fig. 4. is a front view showing the movement state of gear lopping, Figs. 5, 6, and 7 are enlarged views of the damper installation showing other embodiments, and Fig. 8 is a front view showing the movement state of gear lopping. It is a cross-sectional view of an electric wire. 1... Bare electric wire, 2... Ring, 3... Damper,
4... Steel tower, 5... Projection, 6... Covering.

Claims (1)

[Claims] 1 Attach an object whose center of gravity is located below the wire grip and has a moment of inertia to the wire that is difficult to snow on, to prevent twisting and rotation of the wire, and to adjust the twisting rotational frequency of the wire to the fundamental frequency of vertical vibration. 1. A method for preventing twisting and rotation of electric wires and preventing gear lopping of electric wires that are difficult to accumulate snow.