JPS6174208A - Crosslinked polyethylene insulated power cable - 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 (Industrial Field of Application) The present invention comprises a cross-linked polyethylene insulation layer and an outer layer of an IJ.
The present invention relates to an improvement in a crosslinked polyethylene insulating capeple made of Fj-vinylnose.

(Prior Art) FIG. 2 is a cross-sectional view of an example of a conventional high-voltage cross-linked polyethylene insulated cable. In the drawing, (1) is a conductor, and ■ is inside! I (conductive layer) (3) is a cross-linked polyethylene formed by extrusion coating polyethylene H + hydrate containing a crosslinker such as dicumyl peroxide (DCP) and applying pressure to cause a cross-linking reaction. Insulating layer, (4
) is an external semiconductive layer, 6) is a metal shielding layer formed by winding copper tape or a large number of copper wires, (6)
) is a polyvinyl chloride sheath. However, in a relatively low voltage cross-linked polyethylene insulated cable such as aKV class, the external semiconductive layer (4 and metal shield F36) may be omitted.

(Problems to be Solved) As mentioned above, the crosslinked polyethylene insulation layer (3) is generally formed by extrusion coating a polyethylene mixture containing a crosslinking agent DCP and applying pressure to cause a crosslinking reaction. However, at this time, decomposition products of the crosslinking agent DCP are produced.

The components of this decomposition product include acetophenone and cumyl alcohol as liquid components, and meta/cumyl alcohol as gas components.
, ethane is generated.

Of these, both acetophenone and cumyl alcohol are 1
0'Ω-ell about 11! Among 1' conductive liquids, acetophenol in particular has been confirmed to have ACM breakdown voltage treeing properties, partial discharge resistance, and water treeing resistance.

As an experiment to show the effect of acetophenone, 0.05 to 0.
This sample was made to absorb 1.5-2.5% acetophenol using 6am low density polyethylene. The electrodes were a normal plate electrode using Nrihoon oil as the surrounding medium (Fig. 3 ■) and a spherical electrode using a flooding mixture of ki/lene and acetone as the surrounding medium (Fig. 3 ■). The results of a short-time breakdown test are shown in FIG. 3. In all cases, when acetophenone is absorbed into polyethylene, the breakdown voltage improves, and this is particularly noticeable as the thickness increases. The reason why the breakdown voltage of the ACM increases when acetophenone is absorbed is believed to be due to the creation of a film of semi-electrical fluid at the defective part to alleviate the steep electric field and suppress partial discharge, based on other experiments.

In addition, the effect of acetophenone in the Tory/Ig test was also found. For example, if you compare the effect of acetophenone after drying to volatilize the decomposition residue and the one in which acetophenone is absorbed, the latter's Tory Ig resistance is approximately three times higher than the former. do.

In this way, the effect of acetophenone on AC breakdown voltage has been confirmed through notes and model tests, but a similar effect also appears in CV cables, and acetophenone acts as a kind of voltage stabilizer on AC performance. be effective.

However, with the structure of the conventional cross-linked polyethylene insulated cable cable shown in Figure 2, the acetophenone volatilizes, so the above-mentioned voltage stabilizer effect is lost, especially when the cable north is made of polyvinyl chloride. Since it has relatively good compatibility with acetophenone, it forms a kind of adsorption layer, causing the problem that acetophenone volatilizes quickly.

(Structure of the Invention) The present invention solves the above-mentioned problem I and provides a cross-linked polyethylene insulated cable with excellent electrical performance.
The cable is characterized by a fluororesin layer provided inside the polyvinyl chloride sheath.

FIG. 1 is a cross-sectional view of an embodiment of the crosslinked polyethylene insulated power cable of the present invention, in which the same symbols as in FIG. 2 indicate the same parts.

In this example, the fluororesin layer (71 is the inner side of the polyvinyl chloride lance (6), that is, the metal barrier layer ((t))
is located outside. The above-mentioned fluororesin layer (n is 0.02 to 0, thickness is about 111W, for example, is composed of polyvinyl fluoride/vinyliso/tape wrapped in 1/2 wraps, or
A tubular tube of polyvinylidene fluoride may be provided, and in the case of a tape filter, two layers are more effective than one layer. In addition, for cables without a fluororesin layer (for example, a relatively low voltage 3KV-treated conductive layer (4) and metal shielding layer), a cross-linked polyethylene insulating layer (3
) may be provided on the uI.

In general, fluororesins such as tetrafluoride ethylene (TFE) and tetrafluoride copolymer (ETFE) vinyliso7 fluoride (PVDF) have better compatibility and permeability to acetophenol than polyethylene, polyvinyl chloride, etc. 5, the compatibility is poor and the permeability is low.

Therefore, the PVC sheath of the C cable (6)
By providing a fluororesin layer 1 on the inside of the fluororesin layer, volatilization of acetophenone can be prevented.

(Example) Using a 6 KV 10G+111” cross-linked polyethylene insulated vinyl sheath cable, (A) original, (B)
Two types of cable samples made of 172 wraps of polyvinylidene tape with a thickness of 0.05W wrapped around the cable core were dried at 80'C for 7 days, and then acetophenone, which is a decomposition residue, was evaporated with M371. did.

The acetophenone content of this cable is 0', 3
59A, but after drying at 80'C for 7 days (the resulting acetophenol content was 0.3% for (A) and 0.05% for (B))
%, and the effect of acetophenol damage prevention 1F b (confirmed) due to the provision of the polyfluorinated vinyliso7 layer.

(Effects of the Invention) According to the above-described crosslinked polyethylene insulated power cable of the present invention, the fluororesin layer, which has poor compatibility with acetophenone and is difficult to absorb, is provided inside the cable's polyvinyl chloride sheath, so crosslinking is prevented. It can be expected that the excellent electrical performance of polyethylene insulated cables will be maintained over a long period of time.

4. The nTI! IL Description FIG. 1 is a cross-sectional view of an example of the cross-linked polyethylene insulated power cable of the present invention, FIG. 2 is a cross-sectional view of an example of a conventional cross-linked polyethylene insulated power cable, and FIG. 3 is a cross-sectional view of an example of the effect of acetophenone. These are experimental results showing an example.

■...Conductor, 2...Inner semiconducting layer, 3...Crosslinked polyethylene insulating layer, 4...Outer semiconducting layer, 5...Metal barrier layer, 6...Polyvinyl chloride sheath, 7 ...
Fu index n effect layer.

1,000 figures 3 houses (mm) Q--

Claims (1)

[Claims] (1) A cross-linked polyethylene insulated power cable comprising a cross-linked polyethylene insulating layer and a polyvinyl chloride sheath as an outer layer, characterized in that a fluororesin layer is provided inside the polyvinyl chloride sheath.