JPS59180909A - Power cable and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electric cable having a hollow conductor formed by aggregating a large number of compression-molded conductor segments and an extruded plastic insulating layer, and a method for manufacturing the same.

[Background technology]

An insulated cable with an insulating layer made of extruded plastic insulating material is called a solid insulated cable.

In order to separately configure such a solid insulated cable for high voltage power, the inventor formed an insulating layer by extruding plastic using a hollow conductor consisting of a large number of compression-molded conductor segments, and this insulating layer was extruded. In order to eliminate defects such as microvoids and amorphous substances caused by the crosslinking process, a fluid insulator (gas or liquid) with uniform insulation properties and self-healing properties is used, and finally the solid We proposed an electric cable with improved dielectric strength by impregnating the insulating layer with the fluid insulator, and a method for manufacturing the same.

By the way, one of them is more specifically, impregnating the insulating layer with insulating oil, which is a fluid insulator, from the hollow part of the conductor of the electric cable to swell the plastic or plastic insulating layer, and then removing the insulating oil. However, after the fluid insulator is supplied at the time of manufacture, even if insulating oil or gas is not supplied again, it can be used as a cable for a long time. must be distributed.

If we consider the conditions during use, we can see that the load current increases and decreases,
As the line is turned on and off, the temperature of the insulating layer constantly changes from high temperature (for example, 95°C) to room temperature. Insulating oil is used to fill the first micro voids and amorphous crystals with insulating oil, creating amorphous oxides with a mixture of plastic and insulating oil, improving electrical properties and stabilizing them. There is also a risk that this purpose will be lost.

[Disclosure of the invention]

The present invention aims to permanently improve and stabilize the electrical properties by keeping the plastic insulating layer and the insulating oil in a mixed state for a long time, avoiding the aforementioned loss of stability in the electrical properties. The present invention relates to an electric cable impregnated with a high viscosity insulating oil that is below the pour point at room temperature and becomes liquid near the maximum operating temperature, as described below, and a method for producing the same.

The embodiments shown in the drawings will be explained below.

In the figure, 1 ID is a hollow conductor made up of a large number of compression-molded conductor segments.Although not shown, the outer periphery of this conductor is bound with stainless steel tape, and a semiconductive layer is formed by extrusion directly above it. All over the above-mentioned semiconductive layer is an insulating plastic material, for example, a material containing at least one of PE, PP, and polystyrene as a main component, mixed with a crosslinking agent, an antioxidant, etc. as necessary. An insulating layer 2 is formed by extrusion, cross-linked to form a cable core, and then covered with a metal sheath 3, such as a corrugated aluminum sheath, to form the cable.

Metal tubes are attached to both ends of the cable covered with the metal sheath 3, wrapped around a cable drum, stored in a tank or oven, energized to the conductor, and connected to a heating source such as the tank wall. In order to dry the plastic insulation layer of the cable while heating it up, a vacuum pump is connected to the metal tube to evacuate the plastic insulation layer, and once the cable has sufficiently dried, the cable is maintained at a temperature higher than its operating temperature and insulated with insulating oil. For example, one metal tube containing an insulating oil containing at least one of DDB, polybutene, or mineral oil as a main component is filled while applying pressure to the other metal tube.

The filled insulating oil enters the space between the metal sheath and the insulating layer and the hollow space of the hollow conductor, penetrates into the insulating layer over time, swells the insulating layer, and impregnates the insulating layer, creating microvoids and amorphous particles. fill the department. In this case, the SP value of the insulating oil (the closer the SP values of the solubility index niblastic and the insulating oil are, the stronger their relative values are, and the greater the extent to which they dissolve into each other and become a mixed body) are PE, PP, and polystyrene. S of
Since the P value is around 8, the SP value is similar to those,
That is, DDE, polybutene, mineral oil, etc. having a molecular weight of around 8 are suitable.

After that, it is deoiled and filled with high viscosity insulating oil.

For high viscosity insulating oils with: DDE, heavy alkylbenzene.

It is an insulating oil composed by mixing polybutene, high viscosity mineral oil, wax, etc., and is used as an insulating oil for solid cables, which are already known as a type of paper insulated cable, and non-drain cables. You can also use It is extremely desirable that at least one component of this high viscosity insulating oil has an SP value of about 8, which is the same as that of the plastic material and the low viscosity insulating and impregnating insulating oil. After deoiling the insulating oil, the cable is heated, and the high viscosity insulating oil is kept at a higher temperature than the maximum operating temperature of the cable later, and is applied to the hollow part of the conductor of the cable and the space under the metal sheath if necessary. Inject under pressure. In this case, one metal tube attached to the metal sheath of the cable is evacuated, and then the other metal tube is injected.

High viscosity insulating oil If kept at a high temperature, the viscosity of the insulating oil will change and it will be easier to impregnate the metal, but if it is brought to room temperature, the insulating oil will shrink and solidify, and in this state it can be handled and installed as a completely solid cable. be.

Even if the cable reaches its maximum temperature when the cable is energized after installation and full load current is applied, as long as it is below the temperature when impregnated with high temperature,
There is no need for an oil tank that collects the expansion of the insulating oil without causing damage to the cable due to the expansion of the fluidized insulating oil.

The first insulating oil impregnation may be omitted.

In this case, as explained above, the cable is heated and dried while being evacuated by a vacuum pump using a metal tube attached to a metal sheath at both ends of the cable, and when it is sufficiently dry, one of the metal tubes is evacuated while being evacuated. The cable is heated and maintained above the maximum temperature during use, and high-viscosity insulating oil with increased fluidity is injected under pressure. This injection is performed into the hollow part of the conductor, where f'L is below the metal sheath.

[action, effect]

As explained above, in the plastic insulated cable of the present invention filled with high viscosity oil, the high viscosity oil melts and uniformly fills the inside of the cable under maximum load, and the impregnated state of the plastic insulation layer is always maintained, and when the load is lowered. The insulating oil also solidifies, so it is like a paper-insulated solid cable with an oil tank along the entire length of the cable, and the plastic insulation layer mixed with the insulating oil is said to maintain high performance permanently, making it easy to install. Because the insulating oil sometimes solidifies, handling is no different from that of conventional plastic insulated cables.

Regarding the manufacturing of the cable, the cable is impregnated with high viscosity insulating oil at a temperature higher than the maximum temperature that occurs during use, so the cable will not be damaged by pressure increase due to expansion of the insulating oil during use. By placing the insulating oil in a state of extremely high temperature heating, injection and impregnation can be carried out smoothly.

[Brief explanation of drawings]

The drawings depict an embodiment of the invention. 1 Hollow conductor, 2 Insulating layer made of extruded plastic,
3.・Metal sauce.

Claims (5)

[Claims] (1) An extruded plastic insulating layer is formed on a conductor having a hollow part, and a metal sheath is formed on the outside of the plastic insulated cape. An electric cable characterized by being impregnated with a high-viscosity insulating oil that becomes liquid at temperatures below the cable's maximum operating temperature. (2) The electrical cable according to claim 1, wherein the extruded glass insulating layer is an insulating layer impregnated with insulating oil in advance. (3) Molding an extruded plastic insulating layer on a conductor having a hollow part, covering the outside with a metal layer to form a cable, drying the insulating layer, and heating the cable above its maximum operating temperature. 1. A method for producing an electric cable, which comprises impregnating a high viscosity insulating oil into the conductor or into the conductor and into the space under the metal source. (4) Prior to impregnation with high viscosity insulating oil, insulating oil is injected into the conductor or into the space under the metal sheath to impregnate the insulating layer and remove the oil. The method for manufacturing the electric cable described in Section 1. (5) at least one type of insulator comprising a plastic material forming a plastic insulating layer, an insulating oil and a high viscosity insulating oil that are first impregnated into the plastic layer;
31. The method for producing an electric caple according to claim 31, wherein a solubility index (sp value) of 8 or less is used in both cases.