JPS5832176Y2 - power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an improved rubber or plastic insulated aluminum electrically powered cable.

Electric cables generally have an internal semiconductive layer formed on the conductor as necessary, and a rubber or plastic insulating layer and an external semiconductive layer provided in this order on the outside. A configuration is known and used in which a metal shielding layer formed by winding, a metal protective layer formed from lead, and an outer protective sheath formed from polyvinyl chloride, diethylene, or the like are provided in this order, if necessary.

In recent years, due to the demand for lighter weight cables, many have used aluminum instead of lead as the metal protective layer.

However, when it comes to power cables that have an aluminum sheath instead of a lead sheath, holes develop in the aluminum sheath in a relatively short period of time, causing the aluminum sheath to no longer function properly. .

The inventors of the present invention conducted a thorough investigation into the cause of this situation and found that the corrosion of the aluminum coating was caused by electrolytic corrosion.

Now, due to the manufacturing process, some moisture inevitably remains in the insulating coating material of the above-mentioned power cable.

This is due to, for example, moisture penetrating and accumulating in the coating layer during the polyethylene crosslinking and cooling steps.

When such an electric cable is used for a long period of time, the heat cycle causes this moisture to gradually seep out from the insulator to the surface and condense on the outer metal, the surface of the beaten copper tape, etc.

In the case of the above-mentioned power cable, when the copper and aluminum sheathing come into contact in the presence of moisture due to the dew condensation, a so-called local battery is formed, and the condensation causes the aluminum to become electrically base to the copper and corrode it. Furthermore, since an alternating current voltage is applied to the power cable, the electrical current of the cable flows through the copper tape shielding layer to the aluminum, further accelerating the corrosion described above (AC corrosion). I found out.

The inventors conducted extensive research in order to solve the problem of corrosion of the aluminum sheathing in conventional rubber casings or plastic insulated aluminum power cables, and as a result, they created an airtight layer of rubber or plastic under the aluminum sheathing. He found that it was effective to provide a device and completed this idea.

That is, in this invention, an inner semiconductive layer is formed on the conductor as necessary, and a rubber or plastic insulating layer and an outer semiconductive layer are further provided in this order on the outside of the wire layer. This electric cable is characterized by having an airtight layer formed by the above-mentioned method, and an aluminum covering layer provided on the outside of the airtight layer.

An embodiment of the device will be described below with reference to the drawings.

In Fig. 1, 1 is a conductor, 2 is an internal conductive layer formed on the conductor 1 as necessary, 3 is a rubber or plastic insulating layer coated on the outside, and an external semiconductive layer 4 is further outside the conductor. The setting obtains line layer 5.

A metal shielding layer 6 is formed on the outside of the wire layer 5 by wrapping a copper tape or the like in a known manner, and then a rubber-based or plastic-based material, or a suitable combination of these materials is applied to the outside by an appropriate method. An airtight layer γ is provided thereon, an aluminum covering layer 8 is provided thereon, and an external protective sheath 9 such as a vinyl chloride sheath is provided on the outer periphery of the aluminum covering layer 8 as required.

There are no particular limitations on the material and thickness of the airtight layer 7, as long as it is sufficient to cut off contact with the aluminum covering layer 8 and the metal shielding layer 6.

Due to the presence of this airtight layer 7, moisture that has leached out over time from the above-mentioned rubber or plastic insulation layer 3 is trapped here, and as a result, in the presence of the above-mentioned moisture, dissimilar metals, ie copper in this example, are trapped. Aluminum corrosion due to the formation of local batteries due to contact between aluminum and aluminum is completely prevented.

Further, the semiconducting layer 4 mentioned above contains a large amount of carbon, and when it comes into contact with aluminum, the aluminum becomes electrically less noble than carbon, and there is a risk of similar corrosion, but this can also be completely prevented.

In addition, in this invention, for example, the above-mentioned line layer 5 is placed in a dryer,
It is further preferred to keep the moisture content in the rubber or plastic insulation as low as possible.

As is clear from the above description and the examples below, this invention completely prevents the corrosion of the aluminum sheath that occurs in a relatively short period of time that occurs in rubber or plastic insulated aluminum sheath cables. However, it is possible to prevent functional deterioration of the power cable for a long period of time, and the effect is extremely large from an industrial perspective.

The effects of this invention will be specifically explained below using examples.

Example 1 Internal semiconducting layer of IIm on conductor of 80011tM2, 2
4.2 A cross-linked polyethylene insulating layer and an external semiconductive layer of 1 layer are formed in this order, and a 0.2 mm thick copper tape is wrapped around the outside of the layer to obtain a wire layer 5. After extrusion coating of polyethylene, a 2 mm thick aluminum coating is applied on top of this to make it 154KV class.

A cross-linked polyethylene insulated aluminum sheathed cable was manufactured.

For comparison, a cable with aluminum sheathing directly on the extruded external semiconducting layer (Comparative Example 1) and a cable with 2WL1n aluminum sheathing directly on the copper tape shielding layer without any polyethylene sheathing layer (comparison) were used. Example 2) was produced.

Water was poured between the aluminum sheath and copper tape shielding layer of the aluminum sheathed cable thus obtained, and electrostriction was applied between the aluminum sheath and the copper tape in this state, and after one month had passed, both when electrostriction was applied and when no electrostriction was applied. The corrosion status of the cable aluminum sheathing was investigated and the results are shown in Table 1.

According to the results shown in the above table, the effect of preventing corrosion caused by the presence or absence of the polyethylene coating, that is, the effect of this invention, was clearly confirmed, and it was also clear that this corrosion was promoted by the application of voltage.

Example 2 The same wire layer as in Example 1 was used, and the results were shown in Table 2 for cases in which the polyethylene coating thickness was different and other materials were coated (however, a voltage was applied in all cases).

According to the results shown in the table above, it is clear that there is no particular limitation on the thickness of the polyethylene extrusion coating layer provided on the copper tape shielding layer, and that an extrusion coating layer of vinyl chloride is also effective.

It has also been revealed that in semiconductive materials in which the airtight layer contains a large amount of carbon, pitting corrosion is promoted by the carbon, and wrapping with cloth tape is ineffective due to insufficient airtightness.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of this invented capeple. DESCRIPTION OF SYMBOLS 1... Conductor, 2, 4... Semiconductive layer, 3... Rubber or plastic insulator, 5... Wire layer, 6... Metal shielding layer, 7... Airtight layer, 8...・・Aluminum coating, 9・・
- External protective sheath layer.

Claims (1)

[Scope of utility model registration request] An airtight layer made of rubber or plastic, etc. on the outside of the wire core, which is formed by forming an internal semiconductive layer on the conductor as necessary, and further providing a rubber or plastic insulating layer and an external semiconductive layer on the outside in this order. An electric power cable characterized by having an aluminum coating on the outside.