JP6789648B2 - Support structure of power cable intermediate junction box - Google Patents

Description

The present invention relates to a support structure for a power cable intermediate junction box, especially in a manhole.

Electric power cables laid in underground pipelines and the like are connected and used in manholes arranged at predetermined intervals. Such a power cable may extend due to heat generated by energization or the like. Therefore, in the manhole, an offset portion in which the power cable is bent in an S shape is formed in order to absorb the extension of the power cable (for example, Patent Document 1).

For example, in the case of a CV cable (cross-linked polyethylene insulated vinyl sheath cable), the intermediate junction box of the power cable is fixed in the manhole, and the extension of the power cable is absorbed by the change in curvature of the offset portion described above. By absorbing the extension of the power cable in this way, the thermal stress applied to the power cable can be relaxed.

In such a method, the power cable in the offset portion is reinforced to increase the repulsive force to reduce the extension of the power cable from the pipeline portion, or a spring is provided in the offset portion to provide a spring. A method using the reaction force of the above has been proposed (Patent Document 2).

Japanese Unexamined Patent Publication No. 60-106314 Japanese Unexamined Patent Publication No. 61-9114

However, in the conventional absorption of the extension of the power cable by the offset portion, different axial forces may be received from the left and right of the intermediate junction box due to the difference in the extension conditions of the left and right power cables. For example, when the lengths of the power cables connected to the left and right of the intermediate junction box are different, or when the shape of the offset portion in the manhole is different, the extension amount of the power cable may be different on the left and right.

In this way, when the extension amount of the power cable is different on the left and right, the intermediate junction box is in a state where the axial force corresponding to the difference in the extension amount is applied. That is, a force is applied in the axial direction to the reinforcing insulator of the intermediate junction box.

In particular, as described above, when the repulsive force of the offset portion is increased, the axial force acting on the intermediate junction box also increases as the repulsive force increases. Therefore, an excessive axial force may be applied to the fixed intermediate junction box.

For example, in a rubber block type junction box (RBJ: Rubber Block Joint), the internal conductor connection portion and the external reinforcing insulator are not fixed in the axial direction, so that the reinforcing insulator is fixed. Therefore, if an excessive axial force is applied to the conductor connecting portion from one side, the interface between the reinforcing insulator and the conductor may shift. If such an interface shift occurs, it becomes a problem in terms of electrical performance.

However, it is difficult to completely match the shapes of the left and right offset portions of the intermediate junction box on the left and right sides of the intermediate junction box due to the layout inside the manhole. In addition, it is difficult to completely match the extension amount of the power cable on the left and right sides of the intermediate junction box.

The present invention has been made in view of such a problem, and provides a support structure for a power cable intermediate junction box capable of absorbing the extension of the power cable and reducing the difference in axial force between the left and right sides. With the goal.

In order to achieve the above-mentioned object, the present invention is a support structure of the power cable intermediate junction box, which is connected to both sides of the fixed pedestal to which the power cable intermediate junction box is fixed and the power cable intermediate junction box, respectively. The fixed pedestal is provided with a moving mechanism capable of moving the fixed frame in the axial direction of the power cable when receiving a force from the power cable, and the moving mechanism includes a support member fixed to a wall surface and a support member. A suspension plate that is rotatably attached to the support member and the fixed pedestal and connects the support member and the fixed pedestal is provided, and the fixed pedestal is suspended from the support member by the suspended plate. , The support structure of the power cable intermediate junction box, characterized in that the suspension plate that supports the fixed frame is rotatable.

In this case, it is desirable that the suspension plate is connected to the support member and the fixed pedestal via a shield bearing.

The power cable intermediate junction box may be a rubber block type junction box.

According to the present invention, since the fixed pedestal has a moving mechanism for moving the fixed pedestal in the axial direction of the power cable, the fixed pedestal can be moved to a position where the forces from the respective power cables are balanced. Therefore, it is possible to prevent a difference in axial force from the left and right sides of the intermediate junction box.

Depending supporting lifting member hanging fixed frame, in parallel to turn relative to each other each suspension plate for supporting the fixed frame, by a movable fixing frame, as compared with the case of using such rail, There is no accumulation of foreign matter on the rail, and problems such as derailment from the rail do not occur.

At this time, if the suspension plate is connected to the support member and the fixed frame via the shield bearing, foreign matter can be prevented from entering the bearing and stable operation can be performed for a long period of time.

By doing so, the left and right axial forces are averaged, and excessive axial forces can be reduced, and even when a rubber block type junction box is used, the interface between the reinforcing insulator and the conductor is displaced. It can be suppressed.

According to the present invention, it is possible to provide a support structure for a power cable intermediate junction box that can absorb the extension of the power cable and reduce the difference in axial force between the left and right sides.

The schematic diagram which shows the power cable intermediate junction box support structure 1. The side view of the power cable intermediate junction box support structure 1. Front view of power cable intermediate junction box support structure 1 (cross-sectional view of power cable 19). The side view of the power cable intermediate junction box support structure 1 in the operating state. Front view of the power cable intermediate junction box support structure 1a (cross-sectional view of the power cable 19). Front view of the power cable intermediate junction box support structure 1b (cross-sectional view of the power cable 19). FIG. 6 is a cross-sectional view taken along the line AA of FIG. 6, which is a bottom view of the junction box fixing frame 15. The bottom view of the junction box fixed mount 15 in the operating state of the power cable intermediate junction box support structure 1b.

Hereinafter, the first embodiment will be described with reference to the drawings. FIG. 1 is a view showing the entire power cable intermediate junction box support structure 1, FIG. 2 is a side view showing the power cable intermediate junction box support structure 1, and FIG. 3 is a front view of the power cable intermediate junction box support structure 1. (Cross-sectional view of the power cable 19). Actually, a plurality of power cable intermediate junction box support structures 1 are installed inside one manhole, but for the sake of simplicity, only one power cable intermediate junction box support structure 1 is shown.

The power cable intermediate junction box support structure 1 is installed, for example, in a manhole. Inside the manhole, power cables 19 led out from the left and right pipelines 4 in the figure are connected to each other. A junction box 3, which is an intermediate junction box of the power cable, is used for connecting the power cable 19.

Inside the junction box 3, the power cables 19 are connected to each other. A reinforcing insulator or the like is formed on the outer periphery of the connection portion between the power cables.

An offset portion in which the power cable 19 is bent in an S shape is formed between the pipeline 4 and the junction box 3. The shape of the offset portion is not limited to the illustrated example. Further, the shape of the left and right offset portions of the junction box 3 and the length from the pipeline 4 to the junction box 3 may be the same on the left and right, or may be different forms.

For example, the offset portion can be not only S-shaped when viewed from the horizontal direction, but also S-shaped when viewed in a plan view, and these can be combined. The shape and size of the offset portion are determined in consideration of the expected extension amount of the power cable 19 and the layout with other configurations.

A standing hardware 5 is installed on the manhole wall surface 7. Although a pair of standing metal fittings 5 is shown in FIG. 1, a plurality of standing metal fittings 5 are installed on the manhole wall surface 7 at predetermined intervals. The standing hardware 5 is formed in the height direction of the manhole wall surface 7.

As shown in FIGS. 2 and 3, a pair of support members 9 are joined to the standing metal fitting 5 at predetermined intervals. That is, the support member 9 is fixed to the manhole wall surface 7. The vicinity of the upper end portion of the pair of suspension plates 11 is connected to each support member 9. The support member 9 and the suspension plate 11 are rotatably connected via a shield bearing 13.

A junction box fixing base 15 is rotatably connected to the vicinity of the lower end portion of the suspension plate 11 via a shield bearing 13 and a shaft 17. That is, the junction box fixing pedestal 15 is suspended from the support member 9 by the suspension plate 11, and the suspension plate 11 is rotatably attached to the support member 9 and the junction box fixing pedestal 15 and connected to the support member 9. The box fixing stand 15 is connected.

The junction box 3 is fixed to the junction box fixing stand 15. Therefore, the junction box 3 does not move or rotate with respect to the junction box fixing frame 15.

Next, the operation of the power cable intermediate junction box support structure 1 will be described. When the power cables 19 are energized from the state shown in FIG. 1, each power cable 19 is stretched due to heat generation. At this time, if the lengths of the power cables 19 on both sides of the junction box 3 are different, or if the form of the offset portion is different, the extension amount of the power cables 19 may be different on both sides of the junction box 3. is there.

When the extension amount of the power cable 19 is different between the left and right sides of the junction box 3, a difference in thermal stress caused by the extension amount occurs with respect to the junction box 3. In this case, an axial force corresponding to the difference in thermal stress is applied to the conductor connection portion inside the junction box 3. As a result, the power cable 19 and the conductor connection portion may cause an interface shift with respect to the reinforcing insulator on the outer periphery.

On the other hand, in the present embodiment, as shown in FIG. 4, the suspension plates 11 rotate in parallel with each other according to the amount of extension (thermal stress) on the left and right, and the junction box fixing base 15 swings on the left and right. It is possible. Therefore, the junction box fixing base 15 moves to a position where the forces from the left and right power cables 19 are balanced. As a result, the thermal stress applied to the junction box 3 becomes uniform on the left and right.

Further, at this time, the junction box fixing base 15 moves in the axial direction of the power cable 19 (in the direction of arrow X in the drawing) while maintaining the horizontal position. That is, when the power cable intermediate junction box support structure 1 receives a force from each of the power cables 19 connected to both sides of the junction box 3, the junction box 3 is maintained horizontally from each power cable 19. The junction box fixing base 15 moves to a position where the forces of the above are balanced. The structure for moving the junction box fixing base 15 in the axial direction of the power cable 19 in this way is referred to as a moving mechanism.

Since the junction box 3 is fixed to the junction box fixing pedestal 15, when the junction box fixing pedestal 15 is moved, it is maintained horizontal and does not rotate around the axis of the power cable 19. If the junction box 3 is tilted or rotated, the power cable 19 connected to the junction box 3 may be subjected to an excessive bending force or a kink.

On the other hand, in the power cable intermediate junction box support structure 1 according to the present embodiment, the junction box 3 does not tilt with respect to the axial direction of the power cable 19 and does not rotate. Therefore, it is possible to prevent excessive bending force and kink from being generated in the power cable 19.

The movable range of the junction box fixing frame 15 may be restricted. For example, when the length of the suspension plate 11 is 300 mm, the rotation range of the shield bearing 13 is restricted to ± 30 °, so that the junction box fixing base 15 can be restricted to a movable range of about ± 150 mm. .. If the movable range of this degree is set, it becomes a sufficiently practical range as a measure for reducing the axial force.

When restricting the movable range of the junction box fixing pedestal 15, the junction box 3 is set in the movable range of the junction box fixing pedestal 15 within a range that does not interfere with the upper support member 9. By doing so, it is possible to prevent the support member 9 and the junction box 3 from coming into contact with each other when the junction box fixing frame 15 moves.

As described above, according to the first embodiment, the junction box 3 can be moved in the axial direction by the moving mechanism. Therefore, when the axial forces from the left and right of the junction box 3 are different, the junction box 3 moves. Then, it can be held at a position where the axial force is balanced. Therefore, it is possible to prevent the axial force from being applied to the conductor connecting portion inside the junction box 3 due to the imbalance of the axial force from the left and right.

In particular, even when the junction box 3 is a rubber block type junction box that does not have a mechanism for preventing the conductor and the reinforcing insulator from slipping, the conductor and the reinforcing insulator are unlikely to be misaligned, so that the position of the conductor portion is Deterioration of electrical performance due to deviation can be suppressed.

As described above, the present invention is particularly effective when the junction box 3 is a rubber block type junction box, but is also applicable to other types such as a prefabricated joint (PJ). Further, the present invention can be applied not only to a CV cable but also to an OF cable (Oil Filled Cable).

Further, in the present embodiment, when the junction box 3 moves in the axial direction, the junction box 3 is maintained horizontal. Therefore, it is possible to suppress the generation of excessive bending stress and kink of the power cable 19 with respect to the junction box 3.

In particular, if the shield bearing 13 is used, it is possible to prevent dust and the like from entering the bearing, and even when the manhole is submerged, stable operation can be performed. Therefore, maintenance is not required, and stable functioning can be performed for a long period of time.

Further, the power cable intermediate junction box support structure 1 has a simple structure, and the installation space can be reduced. For this reason, the junction box 3 usually supports three phases vertically on the manhole wall surface 7, but at this time, the distance between the junction boxes is about 450 mm (example of a 275 kV line). The power cable intermediate junction box support structure 1 of the present embodiment can be stored in the conventional storage space, and can be supported by the conventional manhole design.

The present embodiment is not limited to the shapes shown in FIGS. 1 to 4. For example, as shown in FIG. 5, a power cable intermediate junction box support structure 1a using a plate-shaped support member 9a may be used instead of the rod-shaped support member 9.

The support member 9a has a substantially trapezoidal shape, has a wide width on the joint side with the standing metal fitting 5, and becomes diagonally narrower from the manhole wall surface 7 toward the tip side. The support member 9a is formed with a notch for avoiding interference with the suspension plate 11, and the suspension plate 11 is connected to the notch via a shield bearing 13. According to the support member 9a, higher rigidity can be ensured.

As described above, in the present embodiment, the shape and the number of each part are not particularly limited, and can be appropriately changed depending on the required strength and the occasion. For example, if the manhole is dustproof and waterproof, a general-purpose bearing may be used instead of the shield bearing 13.

Next, the second embodiment will be described. FIG. 6 is a front view (cross-sectional view of the power cable 19) of the power cable intermediate junction box support structure 1b, and FIG. 7 is a sectional view taken along the line AA of FIG. 6, which is a bottom view of the junction box fixing frame 15. It is a figure. In the following description, the configurations that perform the same functions as those in the first embodiment are designated by the same reference numerals as those in FIGS. 1 to 5, and duplicate description will be omitted.

The power cable intermediate junction box support structure 1b has almost the same structure as the power cable intermediate junction box support structure 1 and the like, but the support method of the junction box fixing frame 15 is different. The fixing member 21 is fixed to the standing hardware 5 of the manhole wall surface 7. A pair of fixing members 21 are provided, for example, at predetermined intervals.

A support member 23 is attached to each of the fixing members 21. The support member 23 and the fixing member 21 are rotatably connected via a shield bearing 13. That is, the support member 23 is rotatably attached to the fixing member 21 with the fixing member 21 as a fulcrum.

A junction box fixing base 15 is rotatably connected to the vicinity of the tips of the pair of support members 23 via a shield bearing 13. That is, the junction box fixing pedestal 15 is supported from below by the support member 9, and the support member 23 is rotatably attached to the fixing member 21 and the junction box fixing pedestal 15, and the fixing member 21 and the junction box fixing pedestal are rotatably attached. 15 is connected.

Next, the operation of the power cable intermediate junction box support structure 1b will be described. In the present embodiment, as shown in FIG. 8, the pair of support members 23 rotate in parallel with each other according to the left and right extension amounts (thermal stress) of the power cable 19, and the junction box fixing base 15 moves left and right. It can swing. Therefore, the junction box fixing base 15 moves to the equilibrium position by the forces from the left and right power cables 19. As a result, the thermal stress applied to the junction box 3 becomes uniform on the left and right.

Further, at this time, the junction box fixing base 15 moves in the axial direction of the power cable 19 (in the direction of arrow X in the drawing) while maintaining the horizontal position. That is, when the power cable intermediate junction box support structure 1 receives a force from each of the power cables 19 connected to both sides of the junction box 3, the junction box 3 is maintained horizontally from each power cable 19. The junction box fixing base 15 moves to a position where the forces of the above are balanced. The structure for moving the junction box fixing base 15 in the axial direction of the power cable 19 in this way is referred to as a moving mechanism.

Since the junction box 3 is fixed to the junction box fixing pedestal 15, when the junction box fixing pedestal 15 is moved, it is maintained horizontal and does not rotate around the axis of the power cable 19. Therefore, it is possible to prevent excessive bending force and kink from being generated in the power cable 19.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained. That is, it is possible to prevent the axial force from being applied to the conductor connecting portion inside the junction box 3 due to the imbalance of the axial force from the left and right.

Further, the length of the support member 23 can be increased if the storage space is the same as that of the power cable intermediate junction box support structure 1 and the like. By lengthening the support member 23, the width of movement perpendicular to the axial direction of the power cable 19 can be reduced, which is effective in limiting the movement in the axial direction.

As described above, the moving mechanism for moving the junction box in the axial direction does not have to be based on the first embodiment or the second embodiment. For example, a rail may be laid in the axial direction of the power cable 19, and the junction box fixing base 15 may be movably installed on the rail. Even in this way, the moving mechanism can move the junction box fixing pedestal 15 in the axial direction of the power cable 19 while maintaining the junction box fixing pedestal 15 horizontally.

However, such a method using rails has a problem of long-term stability, such as foreign matter accumulating on the rails and hindering the movement of the junction box. Further, as described above, when the bending force is applied to the junction box 3, the junction box fixing base 15 may be derailed from the rail. Therefore, as in the present embodiment, there is a suspension support method in which the junction box fixing base 15 is suspended from above without using rails, or a method in which the junction box fixing base 15 is supported from below by a support member 23 extending from the side. It is desirable to have.

Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention does not depend on the above-described embodiment. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical ideas described in the claims, and these are naturally included in the technical scope of the present invention. It is understood that it belongs.

For example, an example in which a pair of suspension plates 11 and support members 23 are provided has been shown, but the number of suspension plates 11 or support members 23 may be any number as long as they can rotate in parallel with each other.

Further, the moving mechanism of the present invention is not limited to the one in which the junction box fixing pedestal is moved in the axial direction of the power cable while maintaining the horizontal direction, and the junction box fixing pedestal is tilted or rotated to adjust the angle. It may be formed and moved in the axial direction of the power cable.

1, 1a, 1b ………… Power cable intermediate junction box support structure 3 ………… Junction box 4 ………… Pipeline 5 ………… Standing hardware 7 ………… Manhole wall surface 9, 9a ………… Support member 11 ………… … Suspension plate 13 ……… Shield bearing 15 ………… Junction box fixing stand 17 ………… Shaft 19 ………… Power cable 21 ………… Fixing member 23 ………… Supporting member

Claims (3)

It is a support structure for the intermediate junction box of the power cable.
A fixed mount to which the power cable intermediate junction box is fixed, and
A moving mechanism capable of moving the fixed frame in the axial direction of the power cable when receiving a force from each power cable connected to both sides of the power cable intermediate junction box.
Equipped with
The moving mechanism
Support members fixed to the wall and
A suspension plate that is rotatably attached to the support member and the fixed pedestal and connects the support member and the fixed pedestal.
Equipped with
The fixed pedestal is suspended from the support member by the suspension plate.
A support structure for a power cable intermediate junction box, wherein the suspension plate that supports the fixed mount is rotatable. The support structure for a power cable intermediate junction box according to claim 1, wherein the suspension plate is connected to the support member and the fixed pedestal via a shield bearing. The support structure for the power cable intermediate junction box according to claim 1 or 2, wherein the power cable intermediate junction box is a rubber block type junction box.

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