JPH0591635A - Power cable line - Google Patents

Abstract

PURPOSE:To provide a power cable line which can prevent application of an excess stress to a connector at an offset even if a corrugated stainless sheath power cable is laid in a non-snake manner in a trough. CONSTITUTION:A corrugated stainless sheath power cable 2 is linearly laid in a trough in a duct 1. The cables 2 in the trough are provided longitudinally at a predetermined interval via a slide guide 3. The cables 2 are so guided by the guide 3 that the frictional force between the surfaces of the guide and the cable per unit length of the cable 2 becomes smaller than that between a sheath and a core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power cable line using a corrugated stainless sheath power cable having a corrugated stainless sheath.

[0002]

2. Description of the Related Art Ultra high voltage power cables are usually snaked in disaster prevention troughs in underground caverns. In a 77 KV class power cable that does not require a metal sheath, offsets are set on both sides of the connection part in the manhole, and the thermal expansion and contraction of the power cable is absorbed by this offset part. For ultra-high voltage power cables of 275KV or more, an aluminum sheath is used to secure the ground fault capacity, and due to its bending fatigue characteristics, it was impossible to absorb thermal expansion and contraction only with the offset part.

Therefore, a method of giving a snake over almost the entire length of the power cable in the trough to disperse the absorption of thermal expansion and contraction is almost universally adopted.

[0004]

However, in the snake laying, there is a problem that the space in the cave must be increased, and the personnel cost, the equipment cost, and the construction period associated with the snake removing work increase. There is a problem.

Recently, as a metal sheath of a power cable,
The corrugated stainless steel sheath is drawing attention. The corrugated stainless steel sheath has attracted attention because it has better bending fatigue characteristics than the aluminum sheath and also reduces stretching strain.

The corrugated stainless sheath electric power cable using the corrugated stainless sheath as described above can be installed in a non-snake straight line in the trough, and the offset portion can absorb thermal expansion and contraction. In that case, the corrugated stainless sheath power cable in the trough needs to be slide-guided at a predetermined interval so as not to buckle due to thermal stress.

At this time, the frictional resistance in the axial direction between the slide guide and the cable surface (that is, the frictional resistance between the slide guide and the cable surface) is the frictional resistance between the sheath and the core (that is, the frictional resistance between the sheath and the core).
Friction coefficient between sheath and core), only the core inside the cable projects to the offset side of the manhole,
There is a risk of applying excessive stress to the connection and destroying it.

An object of the present invention is to provide a power cable line which can prevent the offset portion from exerting excessive stress on the connection portion even when the corrugated stainless steel sheath power cable is non-snaked.

[0009]

The structure of the present invention for achieving the above object will be described. In the present invention, a corrugated stainless sheath power cable is laid straight, and the corrugated stainless sheath power cable in the trough is slid. In the power cable line, which is guided slidably in the longitudinal direction by the guide, and the corrugated stainless sheath power cable is offset in the vicinity of the connection portion,
The corrugated stainless sheathed power cable is guided by the slide guide so that the frictional force between the slide guide and the cable surface per unit length of the corrugated stainless steel sheathed power cable is smaller than the sheath-core frictional force. Is characterized by.

[0010]

[Function] As described above, the corrugated stainless sheath power cable is guided by the slide guide so that the friction force between the slide guide and the cable surface per unit length of the corrugated stainless sheath power cable is smaller than the sheath-core friction force. Then, it is possible to prevent only the core inside the cable from protruding toward the offset portion side of the manhole at the time of thermal expansion and contraction. Therefore, it is possible to prevent the connecting portion from being destroyed due to excessive stress being applied to the connecting portion due to the protrusion of the core.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a power cable line according to the present invention. In the power cable line of this embodiment, a corrugated stainless steel sheath power cable 2 is laid straight in a trough (not shown) in the cave 1. The corrugated stainless steel sheath power cable 2 has a cable core 2a.
A corrugated stainless steel sheath 2b is coated on the outer periphery of the above, and a semi-hard vinyl anticorrosive layer (not shown) is provided on the outer periphery thereof. That is, the cable sheath has a two-layer structure.

The corrugated stainless steel sheath power cable 2 in the trough is guided by a slide guide 3 so as to be slidable in the longitudinal direction. The slide guides 3 are provided at intervals of, for example, 1 to 2 m so that the corrugated stainless steel sheath power cable 2 does not buckle during thermal expansion and contraction in the trough. In this case, the corrugated stainless steel sheath power cable 2 is guided by the slide guide 3 so that the frictional force between the slide guide and the cable surface per unit length of the corrugated stainless steel sheathed power cable 2 becomes smaller than the sheath-core frictional force. Has been done.

In the manhole 4, the corrugated stainless steel sheath power cable 2 is offset on both sides of the connecting portion 5, and an offset portion 2X is provided.

In such a power cable line, the cable core 2a and the corrugated stainless steel sheath 2b tend to extend toward the manhole 4 side due to heat generated by energization, but the cable core 2a is larger than the corrugated stainless steel sheath 2b. Since the temperature change and the expansion coefficient are larger in the case of, the corrugated stainless steel sheath 2b is pulled by the cable core 2a in the direction indicated by the arrow by the frictional force of f _c = μ _c · w _c .

The corrugated stainless steel sheath 2b receives a frictional force of f _s = μ _s · W per unit length from the slide guide 3 in the direction opposite to the pulling direction by the cable core 2a.

Here, each symbol has the following meaning.

F _c : Sheath-core frictional force μ _c : Sheath-core friction coefficient w _c : Weight per core unit length f _s : Sliding guide-cable surface frictional force μ _s : Slide guide-cable surface friction Coefficient W: Weight per unit length of cable Sliding guide · The frictional force f _s between the cable surfaces is the sheath ·
If greater than the inter-core frictional force f _c, since only the cable core 2a is to extend out into the manhole 4, needs to be slide guide cables inter-surface frictional force f _s <sheath-core between the frictional force f _c is there.

That is, it is necessary to set μ _s <(μ _c · w _c ) / W from μ _s · W <μ _c · w _c .

The coefficient of friction between the sheath and the core of the corrugated stainless steel sheathed power cable 2 μ _c varies slightly depending on the cable temperature, but the lowest value at room temperature is less than that of many measured examples.
It will be about 4.

The weight ratio w _c / W between the cable core 2a and the entire cable varies slightly depending on the cable conductor size.
It is about 0.6 to 0.8 for a 5KV class cable.

Therefore, the friction coefficient μ _s between the slide guide and the cable surface may be 0.4 × 0.6 = 0.24 or less, which is a numerically sufficiently realizable value.

FIG. 2 shows an embodiment of a slide guide 3 used in the present invention, which slidably guides three corrugated stainless sheathed power cables 2 stacked in a bale. The slide guide 3 has a structure in which three corrugated stainless steel sheath power cables 2 are slidably held by guide members 7a and 7b having tetrafluoroethylene resin plates (trade name: Teflon) 6a and 6b on the inner surface. ing. Reference numeral 8 is a bolt that connects the guide members 7a and 7b.

In this way, the three-corrugated stainless-sheathed electric power cable 2 has a tetrafluoroethylene resin plate 6 on its inner surface.
When gripped by the guide members 7a and 7b having a and 6b, the friction coefficient μ _s between the slide guide and the cable surface is 0.
It can be about 2. Further, when the surface pressure is applied to the tetrafluoroethylene resin, the friction coefficient can be reduced to about 0.05, and the required surface pressure can be obtained by increasing the tightening torque of the bolt 8 in FIG.

FIG. 3 shows an embodiment of a slide guide 3 used in the present invention for slidably guiding a single corrugated stainless steel sheath electric power cable 2.
The slide guide 3 has a structure in which the corrugated stainless sheath electric power cable 2 is held by paired guide rollers 11a and 11b which are erected on the substrate 9 via shafts 10a and 10b. In this case, the surface of the cable anticorrosion layer of the corrugated stainless steel sheath power cable 2 with which the guide rollers 11a and 11b are in contact must be filled up with a valley filling material 12 such as epoxy putty to eliminate surface irregularities.

[0025]

As described above, in the power cable line according to the present invention, the friction force between the slide guide and the cable surface per unit length of the corrugated stainless sheath power cable is smaller than the friction force between the sheath and the core. Since the corrugated stainless steel sheathed power cable is guided by the slide guide, it is possible to prevent only the core inside the cable from protruding to the offset side of the manhole during thermal expansion and contraction. It is possible to prevent the connection portion from being destroyed due to the addition of Therefore, according to the present invention, the corrugated stainless sheathed power cable can be installed without any snake.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a line configuration of a power cable line according to the present invention.

FIG. 2 is a cross-sectional view showing a usage state of an example of a slide guide used in the present invention.

3A and 3B are a lateral cross-sectional view and a side view showing a usage state of another example of the slide guide used in the present invention.

[Explanation of symbols]

1 ... Cave, 2 ... corrugated stainless steel sheath power cable,
2X ... Offset part, 2a ... Cable core, 2b ... Corrugated stainless steel sheath, 3 ... Slide guide, 4 ... Manhole, 5 ... Connection part, 6a, 6b ... Tetrafluoroethylene resin plate, 7a, 7b ... Guide member, 8 ... bolts, 9 ... boards,
10a, 10b ... Shafts, 11a, 11b ... Guide rollers,
12 ... Valley filling material.

Claims (1)

[Claims] 1. A corrugated stainless sheath power cable is laid straight, and the corrugated stainless sheath power cable in the trough is slidably guided in a longitudinal direction by a slide guide, and the corrugated stainless sheath power cable is connected thereto. In the power cable line where an offset is taken in the vicinity of the section, the corrugated stainless sheath power cable is constructed so that the friction force between the slide guide and the cable surface per unit length of the corrugated stainless sheath power cable is smaller than the friction force between the sheath and the core. A power cable line, wherein the attached stainless sheath power cable is guided by the slide guide.