JPS6238927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to improvements in power cable connections and, more particularly, in oil-filled power cable connections.

Here, the structure of the connection part of the oil-filled power cable will be explained based on FIG. 1. In Figure 1, 1
2 is an insulator of an oil-filled power cable, 2 is a connection reinforcing insulator wound around the outer periphery of the cable insulator 1, 3 is an epoxy insulator for electric field mitigation inserted closely around the outer periphery of the reinforcing insulator 2, 4 5 indicates an insulated pipe, 5 indicates an oil-impregnated pipe, 6 indicates an aluminum sheath, 7 indicates a copper pipe, and 8 indicates a lead work.

In the above configuration, so-called laminated synthetic paper, which is made by laminating cellulose paper on a plastic film such as polypropylene, is used as the reinforcing insulator 2 for the connection part. Conventionally, laminated synthetic paper that has been previously dried is further subjected to vacuum degassing treatment and impregnated with oil at room temperature. The impregnating oil used to impregnate the laminated synthetic paper, such as alkylbenzene oil, has the property of swelling and dissolving plastic materials, although there are some differences depending on the oil actually used. When the material is polypropylene, the swelling rate can exceed 10%. Therefore, laminated synthetic paper obtained by laminating cellulose paper on a plastic film, especially laminated synthetic paper obtained by laminating cellulose paper on a polypropylene film, is used as the reinforcing insulator 2 for the connection part of an oil-filled power cable. When used, there is a concern that the swelling of the reinforcing member 2 will apply unreasonable mechanical stress to the epoxy insulator 3 that is tightly inserted into its outer periphery, causing cracks in the insulator 3 and damaging the electrical characteristics of the cable. It was hot.

The present invention has been made in consideration of the above points, and its purpose is to provide a highly economical cable that can withstand long-term use without impairing the electrical characteristics of the cable. The present invention aims to provide a connection structure for oil-filled power cables.

[Summary of the invention]

In order to achieve the above object, the oil-filled power cable of the present invention is provided by laminating cellulose paper on a plastic film as a reinforcing insulator that is provided on the cable insulator and allows the epoxy insulator to be tightly inserted into the outer periphery. It is characterized in that it is made of laminated synthetic paper that is formed by vacuum degassing, oiling, and heat treatment.

〔Example〕

Hereinafter, the present invention will be described based on an embodiment of the drawings. In FIG. 1 showing the connection structure of an oil-immersed power cable, the configuration of each part indicated by reference numerals 1 to 8 is as described above [Background and purpose of the invention]. As described in the above section, in the present invention, the connection reinforcing insulator 2 wound around the outer periphery of the cable insulator 1 is subjected to a heat treatment (for example, at 100° C. for 10 hours) after vacuum degassing and oil filling. The gist is that it is constructed from laminated synthetic paper molded as follows.

FIG. 2 is a swelling rate-time characteristic diagram of polypropylene laminated synthetic paper using heating temperature as a parameter. The swelling saturation time of laminated synthetic paper formed by laminating cellulose paper on a polypropylene film is about 1 to 2 months at room temperature, but when heated at high temperature, it takes about 10 to 2 months as shown in Figure 2. A few dozen hours is enough.

In other words, as shown in Figure 2, the processing conditions to completely swell the laminated synthetic paper, or in other words, the conditions to heat the oil-impregnated laminated synthetic paper to a state where the paper thickness does not change, are approximately 10 hours at 100°C, as shown in Figure 2. It turns out that about 50 hours is enough even at 80℃. Note that once the laminated synthetic paper obtained as described above is heated and swelled, the amount of swelling remains almost unchanged even when the temperature is lowered to around room temperature. The same can be said of laminated synthetic paper made by laminating cellulose paper onto a plastic film.

Therefore, according to the present invention, which has been explained based on FIG. 1 with reference to FIG. Even when the epoxy insulator 3 for electric field relaxation is closely inserted around the outer periphery of the reinforcing insulator 2, the laminated synthetic paper constituting the reinforcing insulator 2 has already swelled and saturated due to the heat treatment after vacuum degassing and oil filling. Therefore, even if the temperature inside the power cable connection becomes high when electricity is applied, the reinforcing insulator 2 will not swell, and unreasonable mechanical stress will be applied to the epoxy insulator 3, causing the insulator 3 to crack. There is no longer any concern that electrical characteristics may be impaired due to the occurrence of turbulence.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to obtain an economical connection structure for an oil-filled power cable that can sufficiently withstand long-term use without impairing the electrical characteristics of the cable. The industrial effects obtained by implementing this method are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a power cable connection part showing an embodiment of the present invention, and FIG. 2 is a swelling ratio-time characteristic diagram of the polypropylene laminated synthetic paper used in the present invention. 1: Oil-filled power cable insulator, 2: Connection reinforcing insulator, 3: Epoxy insulator, 4: Porcelain tube, 5: Impregnated oil, 6: Aluminum sheath, 7: Copper pipe, 8: Lead work.

Claims (1)

[Claims] 1. As a reinforcing insulator that is installed on the cable insulator of an oil-filled power cable and allows the epoxy insulator to be closely inserted into the outer periphery, it is formed by laminating cellulose paper on a plastic film, and is heated after being vacuum degassed and lubricated. A power cable connection part characterized in that it is made of treated laminated synthetic paper.