JPS5828109A - Of cable line - 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 In ultra-high voltage lines (for example, 275 to 500 KV), in order to reduce power transmission loss and make cables more compact, plastic films are used alone or alternately with kraft paper.
Cables that have an insulator made of plastic film or a composite of plastic film and kraft paper have come to be used. In this case, among plastic materials, polyolefin resins such as polypropylene, polymethylpentene, and polyethylene are used as materials with excellent economical efficiency and industrial productivity. These materials can be used as a single film or as a laminate laminated with kraft paper.

On the other hand, an OF cable has a connection part (terminal connection part or intermediate connection part) for each installation section, and at the connection part, the cable's aluminum, lead or stainless metal sheath is
Normally, lead connections are made using solder containing soot and lead as the main ingredients. A propane torch or the like is used as a heating jig for this lead work, and solder with a bath melting point of 150 to 300°C is melted and welded to the metal sheath of the cable, so the outer layer of the cable's insulation in the vicinity Heated through the metal layer and impregnating oil, local but instantaneous 130-200
reach ℃. In this case, there is no problem if the cable insulation is made of kraft paper like conventional cables, but if polyolefin plastic material is used, if exposed to the high temperature in insulating oil, it may cause local damage. Changes in quality such as dissolution, swelling, and solidification may occur, which is not desirable.

To overcome these drawbacks, lead-free connection methods that do not use lead, so-called low-melting solder that melts within +20'C, have been considered, but these have not been widely used in the past. Ordinary lead construction using traditional materials and construction methods is a method that has a proven track record both technically and in terms of quality.
Even if there is a problem with the cable and it is necessary to take emergency measures, it can be dealt with quickly, and it is also cheaper than other construction methods. However, there are only a few plastic materials that can be used as cable insulators and can withstand ordinary lead construction, and only a few fluororesin plastics, such as Teflon (trade name) and fluorinated ethylene propylene, are mentioned.

However, fluororesin plastics are expensive,
It is not reasonable to use such an expensive plastic material over the entire length of a one-length cable simply for the lead work at both ends of the cable.

Therefore, in the present invention, an insulator that can withstand ordinary lead work is used only in a certain length range from the end of the section cable, and only in the outer layer part, and in other parts, a polyolefin film alone or a film and kraft paper is used. OF cables are constructed using alternately wound insulators or insulators made of a laminate of polyolefin film and kraft paper, and the cable sections are connected using ordinary lead wire, reducing power transmission loss. The objective is to obtain a compact and economical ultra-high voltage OF cable line with less noise.

The implementation of the present invention will be described below.

Normally, low voltage cables are manufactured in long lengths as a prospective product, and after manufacturing, they are cut into pieces according to the length of the installation section and shipped. In this case, even if one manufacturing loft includes multiple sections, the cable is not cut to a predetermined length until manufacturing is completed.

However, when the voltage is 275 to 500 KV, the conductor cross section is 1,
For OF cables of 0.000- or more, the length of the line used and the length of the installation section is clear, and since the manufacturing lot is only for a small number of sections, the shipping section in one manufacturing lot is clearly defined before manufacturing. In most cases,
It is also possible to specify the position where ordinary lead work is to be performed at the installation site.

FIG. 1 shows the relationship between one manufacturing lot and a shipping lot. In the figure, from end A to end B is one manufacturing loft, and for the 0 point in the middle, ac is one section length, and bc is also one section length, for example, ac is 5-300 m, b c is 400 m. The section cables cut at the zero point in the middle are each transported to the installation site as a shipping lot, and after installation at the site, conductors are connected, insulation is applied, and lead work is performed. Such an intermediate 0 point is planned at the stage of manufacturing, and is also at both ends a of l manufacturing lot.

Since the presence or absence of cables etc. connected to this is also known in b, for example, 2 to 50
4 to 100 meters in front and behind the planned lead work location in the middle of m1
, 2-50 again before the end? Only in the part n, as shown by diagonal lines, an insulating material that is not particularly affected by ordinary lead construction is made by wrapping ordinary polyolefin film alone or alternately with kraft paper, or by wrapping polyolefin film and kraft paper alternately. A composite insulator is formed by winding the laminate onto an insulator to a thickness of about 2 to 61 mm.

An example of the cable used in the present invention is shown in FIG. 2 in cross section taken along the line X--X in FIG. 1, in which a lead-resistant insulator is wound.

In the figure, 1 is an electric conductor, and an oil passage 2 is located in the center of it.
is formed. 6- A film made of ordinary polyolefin plastic is wrapped around the outside of the electrical conductor 1, or a film and kraft paper are wrapped alternately, or a tape made of a laminated polyolefin plastic film and kraft paper is wrapped inside the insulator. Form layer 3.

These tapes are wound so that oil passages are formed in the radial direction. Then, an insulating outer layer 4 is formed by wrapping a tape made of a lead-resistant insulating material that is not affected by the heat during lead work.

The following three lead-resistant insulation materials are unaffected by lead construction.
There are seeds.

(1) Kraft paper, which is made of natural fibers and has been commonly used, is a material that is not affected at all. In this case, considering the purpose of the present invention, εX t
A small anδ is preferable.

Kraft paper is generally cheaper than plastic insulating materials, and is a readily available and convenient material for use as an insulating material for conventional cables.

As shown in FIG. 2, when kraft paper is wrapped as the outer layer 4 of the insulator, the electrical characteristics of the cable are determined by the polyolefin resin in the part of the cable that is not affected by the lead wire, that is, the part corresponding to the outer layer 4. This is slightly worse than insulators made by wrapping polyolefin plastic tape alone or alternately with kraft paper, or by wrapping polyolefin glass tape laminated with kraft paper. Since it is only applied to a limited and short section compared to the total length of the cable, it is averaged over the total length of the cable, and there is almost no layer.

(2) Insulating materials using plastic materials, such as Teflon, fluorinated ethylene propylene, etc., which are not affected by lead construction and have electrical properties equivalent to or better than those of the insulator layer 3 in Figure 2. There is.

Although these materials are expensive and somewhat harder to obtain than kraft paper, they are used only in small amounts for the outer layer of the cable at both ends of the section, so they maintain the same electrical properties over the entire length of the cable. The benefits of gaining it are significant.

(3) Even among polyolefin plastic materials, there is polymethylpente/, which is an insulating material with somewhat excellent heat resistance. This plastic tape made of polymethylpentene alone or alternately with kraft paper, or a tape made by laminating a plastic film made of polymethylpentene and kraft paper, can be used as a cheap and versatile plastic tape made of polypropylene or polyethylene, or A plastic tape and a kraft paper tape are used alternately, or a tape made by laminating these plastic films and kraft paper is wound as an insulator outer layer 4 of a cable having an insulator inner layer 3.

This polymethylpentene is not as expensive as Teflon or fluorinated ethylene propylene. However, since the melting temperature in insulating oil is approximately 160°C, the temperature of the lead work must be controlled to 160°C.
It is necessary to work while keeping the amount within.

The above-described lead-resistant insulation material is applied to the outer layer of the insulator of the section end cable where lead work is applied (shaded area in Figure 1).
Form about 1 shoulder. On the other hand, the insulator of the cable in the part not affected by the heat of the lead wire (the part other than the shaded area in Figure 1) can be used without changing the insulating material of the insulator layer 3. Wrap until layer 4 has the same diameter.

As described above, the metal sheath 5 made of aluminum, lead, or stainless steel is formed on the workpiece that partially has the insulating outer layer 4 at a predetermined position on the cable, as in a normal OF cable, and then An anti-corrosion layer 6 made of polyethylene or vinyl chloride is formed by the pressurized chambers. The cables are dried, deaerated and filled with insulating oil, then cut at the lead-work location, and the cut cables are shipped.

At the installation site, the end of the section cable is stripped, the conductor is connected, the insulation is treated with insulating tape, etc., the insulator is covered with a metal sleeve, and the section cable is placed between both metal sheaths and the end of the metal sleeve. The OF cable line is completed by performing ordinary lead work, vacuum treatment, filling with oil, applying a protective coating thereon, and sequentially forming the connection parts.

Table 1 shows the approximate values of dielectric constant ε and dielectric loss angle tan δ of kraft paper (A), laminate of kraft paper and polyolefin (Bl and plastic only (C1), 10−).

*ε and tanδ of B vary depending on the amount ratio of polyolefin.

Also, when voltage is applied to the cable, the loss wd in the insulator (dielectric) is wd = K ・(t, tan
δ) is expressed as V2. Here, K is a proportionality constant, and ■ is voltage to ground = E- (E: line voltage).

V name, for example, ε=2.8 for the entire insulator. tanδ=0.0
If the old PPLP (which corresponds to B in Table 1, which is a laminate of kraft paper and polypropylene) is used instead of one made only of kraft paper, the loss wd will be reduced to 1/2 to +78.

In the present invention, as already explained, there are places in the middle of the line near the connection points where εtanδ is different, and as a whole there is almost no difference from the loss wdO value described above.

Therefore, according to the present invention, a cable insulated only with an insulator made of polyolefin plastic alone or alternately with kraft paper or an insulator made of a laminate of polyolefin plastic film and kraft paper can be used. It is possible to form a line with little dielectric loss that does not change, and the effect in terms of implementation is enormous.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a manufacturing lower floor, a shipping loft, etc. FIG. 2 is a cross-sectional view of an example of an OF cable used to implement the present invention. I... Electric conductor, 2... Oil passage 1.3... Insulator inner layer, 4... Insulator outer layer, 5... Metal sheath, 6...
...Anti-corrosion layer.

Claims (3)

[Claims] (1) Within a certain length range from the end of the section cable, the outer layer of an insulator consisting of polyolefin/fin film alone or alternately with kraft paper, or a laminate of polyolefin plastic film and kraft paper, is used. An OF cable line characterized in that OF cables having lead insulation are successively connected by lead work. (2) When #f lead insulation is wrapped as an outer layer of an insulator consisting of an inner layer of a polyolefin film alone or an insulator alternately with kraft paper, or a laminate of a polyolefin plastic film and kraft paper, The OF cable line according to claim 1, characterized in that the OF cable line has the same diameter as the portion where only the insulator is wound. (3) As the lead-resistant insulating material, one or more of kraft paper tape, fluororesin tape, a composite of fluororesin tape and Kraft paper tape, polymethylpentene tape, and a composite of polymethylpentene and kraft paper tape is used. O according to claim 1, characterized in that
F cable line.