JP2785740B2 - Multi-conductor power line spacer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a multiconductor spacer used for an overhead transmission line.

[0002]

2. Description of the Related Art Conventionally, as a frame member of a spacer for a multi-conductor power transmission line, a circular rod (a rod having a circular cross section), a circular pipe, a spring (a coil spring), and a U-shaped steel (an open cross section having a U-shaped cross section) have been used. Steel materials). However, in recent years, as the number of conductors has been increased with the aim of increasing the power transmission capacity, transmission lines with increased conductor spacing have been constructed, and multi-conductor spacers having a longer frame portion than before (hereinafter referred to as large bundle diameter spacers). Is needed. In this large bundle diameter spacer, a large external load tends to be applied, and therefore, the above-described members used in the frame of the spacer are often not always optimal in design. FIG. 4 shows an example of a conventional multiconductor spacer. As shown in the figure, a U-shaped steel section is used for the frame section 12, an annular hexagonal spacer frame having a single cross-sectional shape is formed, and a clamp section 13 is formed to protrude outward at each joint point. Bracket for conductor clamp 14
Are attached integrally. This shape shows excellent performance against the torsion load of the frame moving load in the track direction, but is not optimal for bending load and buckling load.

[0003]

The dominant external loads that determine the design of the spacer frame member are subspan load, line direction moving load, and short-circuit electromagnetic force load.
The details are as follows. (1) The subspan load is a bending load applied to the frame 10 when horizontal vibrations (vibrations having substantially opposite phases) are generated in the electric wires 11, 11 supported between the spacer frames as shown in FIG. (2) The line direction moving load is such that when the overhead metal fittings move, the central wires 11, 11 are moved in the line direction as shown in FIG. 6 (in FIG. 6, in the direction perpendicular to the plane of the paper). This is a load that causes the spacer frame 10 to bend while being bent due to movement. (3) The short-circuit electromagnetic force load is, as shown in FIG.
When a short-circuit current flows through the wires, the centripetal force acts evenly between the wires 11. Therefore, it is a load for compressing the spacer frame 10 in the axial direction of the member.

As described above, in the present situation where a large bundle diameter spacer having a longer frame portion than before is required, if the frame portion, which accounts for a large proportion of the spacer weight, is not properly designed, the spacer weight becomes excessively heavy, and the product weight increases. Not only does the cost increase, but also the transportation and installation work during construction become difficult, leading to an increase in construction costs. Therefore,
For the strength design of the spacer frame member, it is necessary to select an optimal one in response to the above-mentioned load.

[0005]

As described above, the design considers that various external forces are applied to the spacer when mounting it on a power transmission line. For a bending load at the time of a subspan load, a thin pipe-shaped member having the same sectional area and a large sectional modulus is advantageous in design. In addition, a member having a flat plate-shaped cross section or a U-shaped, H-shaped, L-shaped open cross-section or the like in which torsional deformation is likely to occur with respect to the torsional load at the time of the line-direction moving load of (2) is advantageous in design. In addition, with respect to the buckling load at the time of the short-circuit load of (3), the buckling phenomenon sharply reduces the buckling resistance when the member starts to be deformed. On the other hand, it is desirable to have point symmetry in which deformation is unlikely to occur, and even if it is not point symmetry, it is desirable to have line symmetry with respect to two or more axes orthogonal to a vertical axis passing through the cross-sectional center of the member. Therefore, it can be seen that the shape of the frame portion of the large bundle diameter spacer is better for members having a plurality of cross-sectional shapes than for a single member in terms of strength design. In view of the above, the multi-conductor power transmission line spacer of the present invention is an overhead transmission line spacer having two or more conductors, wherein the frame member of the frame portion to which the clamp portion for gripping the electric wire is attached is (1)
(2) having an open cross section in the middle of the frame portion between the clamp portion and the clamp portion; and (3) having a portion in contact with the clamp portion of the frame portion and the clamp portion. Both the intermediate portion and the clamp portion have a structure in which the cross-sectional shape is symmetric at least in two axes perpendicular to the cross-sectional center of the closed frame portion.

[0006]

[Action]

(1) Since the cross-sectional shape of the portion in contact with the clamp portion is a closed cross-section, if a bending load is applied to the spacer due to a subspan load or the like, the weakest point in the design is the joint portion between the clamp portion and the frame portion. Often it is. The generated bending stress σ _B of the frame portion with respect to the bending load is basically expressed by the following equation (1).

[0007]

(Equation 1)

Therefore, to reduce the generated bending stress σ _B , it is sufficient to increase the section modulus Z _F. If the sectional area is the same, the use of a large-diameter pipe material or a large gap in the bending moment direction is required. A parallel arrangement of flat plates with openings is effective. However, since the bending load direction is not necessarily limited, those having an open cross section such as a parallel arrangement of flat plates are not preferable because stress concentration occurs in the members depending on the load direction, and the clamp portion to be joined has a limited size with a clamp portion. For this reason, a pipe-shaped one having a large diameter cannot be adopted without limitation, and in some cases, a rod-shaped rod having a solid cross section may be used instead of the pipe-shaped one. Therefore, in the present invention, the cross-sectional shape of the frame member desirably in contact with the clamp portion is a closed cross-sectional shape. Next (2)
The fact that the frame member has an open cross section at the center or middle of the frame portion between the clamp portions will be described. When a line direction moving load is applied to the spacer, a torsional load is applied to the frame portion of the spacer, and it is necessary to absorb this load by torsional deformation. At this time, according to the member having a closed cross-sectional shape, there is no room for deformation of the cross-sectional shape with respect to the torsional load, so it is necessary to absorb all the torsional load by torsional stress deformation, which is larger in design than a member having an open cross-section. Disadvantageous. The comparison of the stress generated between the closed section member and the open section member with respect to this torsional load cannot be generally compared because there is no appropriate stress calculation formula for the various cross section members. In the experiment where the same torsional load was applied to the U-shaped steel and the steel pipe of the closed section member, the U-shaped steel generated stress was 3.5 kgf / mm ² , and the steel pipe generated stress was 18.3 kgf / mm ²
And about 5 to 6 times the stress was generated in the pipe having the closed section. Therefore, in the present invention, it is extremely preferable that the intermediate portion of the frame portion be a frame member having an open cross section. Further, for the buckling strength due to the short-circuit electromagnetic force load of (3), various calculation formulas have been proposed, and there is no unified formula.
In steel structure design, the allowable buckling stress is defined by equation (2).

[0009]

(Equation 2)

The equation (2) is not shown for either the open section or the closed section, but the design equation is generalized in consideration of the fact that the member having the open section involves a large cross-sectional deformation when buckled. It is presumed that equation (2) is probably for a rod or pipe with a closed cross-section because it is difficult to do so. Therefore, a steel pipe of the cross-sectional area 263 mm ² of U-shaped steel and 310 mm ^2, 60 to the length
A buckling test was performed on a 110 mm member and compared with the allowable buckling stress calculated by the above equation (2). As a result, the experimental value / calculated value of the steel pipe agreed well with 1.00 to 1.07. For steel, it was confirmed that the strength was 0.74 to 0.80, which is 70 to 80% of that of steel pipe. When examining the cause of the inferior buckling strength of this U-shaped steel pipe by experiments, etc., the U-shaped steel does not have a point-symmetrical cross section. It has been found that stress is generated and the cross-sectional shape is deformed in a direction that is easy to buckle due to the open cross section, thereby facilitating buckling. Therefore, for the buckling load, it is most preferable that the cross-sectional shape of the frame is point-symmetric with respect to the centroid, but if the cross-section is line-symmetric with respect to two axes orthogonal to the centroid, Since it has a practically equivalent meaning to being point-symmetric with respect to the center, the requirement (3) is that at least two axes perpendicular to the axis passing through the centroid at the end and center of the frame What is necessary is that the cross-sectional shape is symmetric.

[0011]

FIG. 1 partially shows an embodiment of the present invention. The overall structure is such that the frame portion 2 has the same structure between a plurality of adjacent clamp portions 1. Take it. FIG. 2A is a cross-sectional view taken along the line AA ′ in FIG. 1 and FIG. 2B is a cross-sectional view taken along the line BB ′ in FIG.
It is just the middle or middle part. On the other hand, the AA ′ section is that of the frame portion 2 at a position close to the clamp portion 1. The frame shown in FIG. 1 forms a circular pipe shape 3 at the position of the frame portion 2 in contact with the clamp portion 1 as shown in FIGS.
The middle part has a slit 4 in which a vertical pipe-shaped surface of the circular pipe-shaped surface is removed symmetrically by attaching a spacer to a transmission line. FIG.
As shown in (a) and (b), the frame portion 2 has a cross-sectional shape of a rectangular tube 5 at a position close to the clamp portion 1, and has a pipe-shaped surface of the rectangular tube at an intermediate portion, which is vertically moved by attaching a transmission line spacer. It has a slit 6 in which two directions are removed symmetrically.

[0012]

When the present invention is applied to a spacer frame, it is possible to carry out a design which can withstand the various loads described above, and it is possible to greatly reduce the number of members of the frame portion as compared with the prior art. Costs can be reduced, transportation and mounting work during construction can be facilitated, leading to a reduction in construction work costs and a good effect on construction safety. This effect is more pronounced as the number of conductors in the overhead transmission line increases.
The effect becomes more remarkable as the conductor interval becomes larger, and it is particularly effective when used for a multiconductor large bundle diameter spacer.

[Brief description of the drawings]

FIG. 1 shows the configuration of the spacer of the present invention.

FIG. 2 shows an AA ′ section and a BB ′ section of an embodiment of the spacer of FIG. 1;

FIG. 3 shows another embodiment of the spacer shown in FIG.
The cross section and the BB 'cross section are shown.

FIG. 4 shows an example of the shape of a multiconductor spacer conventionally used.

FIG. 5 is an explanatory diagram of a subspan load.

FIG. 6 is an explanatory diagram of a line direction moving load.

FIG. 7 shows an explanatory diagram of a short-circuit electromagnetic force load.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Clamp part 2 Frame part 3 Cylinder (cross section) 4 Slit 5 Square tube (cross section) 6 Slit

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H02G 7/00-7/22

Claims (3)

(57) [Claims] 1. A cross section of a frame portion connecting a clamp portion of a portion for holding an electric wire in an overhead transmission line spacer having two or more conductors has a closed cross section in a portion in contact with the clamp portion, and has an open cross section in an intermediate portion of the frame portion. A spacer for a multi-conductor transmission line, wherein a cross-sectional shape is symmetrical in at least two axes orthogonal to an axis passing through the center of gravity of both a portion which is in contact with a clamp portion of a frame portion and an intermediate portion. 2. A cross section of a frame connecting a clamp portion of a portion for gripping an electric wire at a portion in contact with the clamp portion,
2. A pipe having a circular cross-sectional shape, wherein the intermediate portion has a circular pipe-shaped surface and a slit provided symmetrically on a surface which is vertically arranged by attaching a spacer to a transmission line. For multi-conductor transmission line spacers. 3. A cross section of a frame portion connecting a clamp portion of a portion for gripping an electric wire has a rectangular tube shape in a portion in contact with the clamp portion, and a rectangular tube-shaped pipe-shaped surface in an intermediate portion connects to a transmission line. 2. The multi-conductor power transmission line spacer according to claim 1, wherein the spacer has a shape having slits symmetrically on two surfaces which are vertically arranged by mounting the spacer.