JPH04149912A - Self-desforming thermal stress absorbing power cable - Google Patents

Abstract

PURPOSE:To enable the easy absorption of thermal of a cable caused by heat generation by forming a stress sheath of a power cable, which sheath has nearly streamline with bump-like protrusions spaced at a certain interval. CONSTITUTION:A sheath 2 of a power cable 1 is formed so as to have nearly streamline bump-like protrusions 3 spaced at a certain interval. In this way, sections between the bump-like protrusions 3 deform simply and naturally so as to absorb thermal expansion easily as the cable 1 rises in temperature. And it is possible to obtain a self-deforming stress power cable which can easily absorb the thermal expansion of the cable 1 caused by heat generation. The streamline with bump-like protrusion 3 of the sheath part 2 changes an extrusion amount of the sheath 2 when extruding sheath 2. The cable 1 is supported by the protrusion 3 parts floatingly in the air, and deflects by its selfweight as shown in dotted lines so as to absorb an extruded amount.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a self-deforming thermal expansion and contraction absorption power cable.

[Conventional technology] When a cable is energized, it generates heat due to the heat generated in the conductor.
A stretch occurs. In order to absorb the elongation caused by this heat generation, in the case of a power cable installed in a conduit, it is common to absorb it by deforming an offset section installed in a cable connection manhole.

Furthermore, in recent years, cables have been developed in which protrusions are attached to the cable in a spiral manner so that the extension is absorbed by the deformation of the cable within the conduit.

Furthermore, fix the cable offset part in some way,
It is also possible to prevent the cable from stretching by increasing the offset reaction force.

In addition, although the purpose is to reduce the axial force,
There is also a method as shown in Japanese Patent No. 41609.

[The problem that the invention aims to solve WA] When constructing a new power transmission line, a manhole of a size suitable for the line conditions can be constructed, but when laying a new cable on an existing line, etc. There are cases where the required offset length cannot be obtained due to limited exclusive space. In this case, even if offset space can be secured by taking measures such as expanding the manhole, a large amount of construction costs will be required.

As a countermeasure against expansion and contraction, there is also a method of fixing the cable at the outlet of the conduit and absorbing the expansion by buckling the cable within the conduit. However, the fixing portion must have a gripping force sufficient to cause the cable to buckle within the conduit, and such a large gripping force may cause mechanical and electrical damage to the cable.

In the case of attaching a spiral protrusion to a cable, the cable production line, especially the extrusion die, must be modified and changed to be rotatable, which requires a large investment in equipment.

In the method disclosed in Japanese Patent Application Laid-Open No. 2-41609, the cable and spacer are separated, so the spacer easily slips, and if it gets caught in a step (joint) in the conduit, there is a risk of twisting the spacer. There is a risk of force acting and causing damage to the cable.

The present invention was made in view of the above points, and it is an object of the present invention to provide a self-deforming heat-expandable membrane power-accumulating cable that can easily absorb the thermal expansion and contraction of the cable due to heat generation. .

[Means for Solving the Problems] The above objects are achieved by forming the sheath of the power cable with substantially streamlined knobs at certain intervals.

``Operation: Since the above-mentioned means is provided, as the temperature of the cable rises, the areas between the knobs easily deform, and thermal expansion and contraction can be easily absorbed.

In addition, since the knob-like protrusion is integrated into the sheath itself and has a streamlined shape, the protrusion applies frictional force to the inner surface of the conduit when it is pulled into the conduit or when it undergoes thermal expansion and contraction in the laid state after being pulled in. It can be made small and slippery, and thermal expansion and contraction due to self-deformation is smooth. In addition, by forming the protrusions in a particularly streamlined shape, local stress concentration during buckling deformation can be alleviated.

[Example] The present invention will be described below based on the illustrated example. An embodiment of the present invention is shown in FIGS. 1-4.

In this embodiment, the sheath 2 of the power cable 1 is formed with substantially streamlined knob-like protrusions 3 at certain intervals. By doing this, as the temperature of the cable 1 rises, the knob-like protrusions 3 deform easily and effortlessly to easily absorb thermal expansion and contraction, making it easier to absorb thermal expansion and contraction of the cable 1 due to heat generation. It is possible to obtain a self-deforming heat-stretchable membrane power-accumulating cable that is capable of absorbing energy.

That is, FIG. 1 shows the external appearance of the cable, and FIG. 2 shows a cross section of the cable. The substantially streamlined knob-like protrusion 3 of the sheath portion 2 changes the amount of extrusion of the sheath 2 when extruding the sheath 2. FIG. 3 shows the state in which the power cable 1 of this embodiment is installed. The cable 1 is supported by the knob-like protrusion 3 and becomes suspended in the air, and bends somewhat due to its own weight as indicated by the dotted line in the figure. Figure 4 shows the state in which the elongation has been absorbed. The elongation caused by the rise in temperature is absorbed by the downward deformation of the cable 1. In addition, in these figures, 4 is a conduit, and 5 is a core.

As described above, according to this embodiment, the following effects can be achieved.

(1) Manhole size can be reduced and it is economical.

Furthermore, since there is no need to expand manholes, cables can be laid on existing railway lines.

(This is because the extension of the cable due to thermal expansion and contraction can be absorbed within the conduit, so the cable offset can be reduced.) (2) Compared to a cable that changes the structure of the cable and makes snakes more likely to occur. , the objective can be achieved economically. (When extruding the cable sheath, (a) the amount of sheath extrusion is increased. (b) By slowing down the speed at which the cable is fed out, the amount of sheath extrusion per unit length is increased.

(c) Installing another extruder will intermittently extrude the protrusions of the sheath. This is because it can be done without changing or remodeling the line. ) The shape of the protrusion should preferably be a streamlined and gentle shape that does not cause snagging in the conduit.

It is desirable that the height of the protrusion is equal to the amount of change in downward movement of the cable in response to a change in the temperature of the conductor of the cable. For example, the coefficient of linear expansion of the cable is 18 x 10-6 (
1/'C), conductor temperature change 65 (''C) distance between protrusions 1
If it is 500 +am, the downward displacement is about 24mm
Therefore, the optimum height of the protrusion is about 24 mm.

[Effects of the Invention] As described above, according to the present invention, the sys of the power cable is formed with substantially streamlined knob-like protrusions at certain intervals, so that as the temperature of the cable increases, the gaps between the knob-like protrusions are reduced. Self-deformation heat allows the cable to deform easily and absorb thermal expansion and contraction without causing problems such as stress concentration. A telescoping power cable can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the external appearance of an embodiment of the self-deforming heat-expandable power-storage cable of the present invention, Fig. 2 is a vertical cross-sectional side view of the embodiment, and Fig. 3 is a cable of the embodiment. FIG. 4 is an explanatory view showing a state in which the cable is drawn into the conduit, and FIG. 4 is an explanatory view showing a state in which the extension is absorbed by deformation of the cable of the embodiment. 1: power cable, 2: sis, knob.

Claims (1)

[Claims] 1. In a self-deforming thermal expansion/contraction absorption power cable that absorbs the elongation of the cable in the conduit due to heat generation, the sheath of the power cable is formed with roughly streamlined knob-like protrusions at certain intervals. A self-deforming thermal expansion and contraction absorbing power cable.