JPH04126309A - Water tree inhibitor type bridging polyethylene cable - Google Patents

Abstract

PURPOSE:To inhibit a water tree without reducing the electric resistance of an insulating body by having a water tree inhibitor contained in the inner and outer layers or the inner and outer semiconductive layers of the insulating body. CONSTITUTION:A water tree inhibitor is contained in either or both of an inner semiconductive layer and an outer semiconductive layer. For example, to a high voltage electric power cable which consists of an inner semiconductive layer 2 provided around the outer circumference of a cable conductor 1 positioned at the center, an insulating body 3. an outer semiconductive layer 4, a metallic tape shield 5, a holding tape 6 and a plastic sheath 7, are added predetermined quantities of 4-4'-thiobis (3-methyl-6-t-butyl-phenole) and hydroxystea phosphatic calcium. Thus, a water tree can be inhibited without reducing the electric characteristics of a bridging polyethylene insulating body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-voltage cable using cross-linked polyethylene as an insulator.

[Prior Art] Water tree degradation of cross-linked polyethylene insulation is caused by the interaction between water that has penetrated into the insulation and the electric field within the insulation during cable use. As a countermeasure for this, when manufacturing cables,
Additives that have a water tree inhibiting effect, such as fatty acid metal salts and fatty acid amides containing OH groups in the molecule, are mixed inside the insulator, and this effect is described in Japanese Patent Application Laid-Open No. 58-22030.
It is described in Publication No. 4.

[Problems to be Solved by the Invention] However, although it depends on the amount added, the above-mentioned additive is basically not an insulating material, but is a material that increases the affinity between water and polyethylene, thereby preventing water from entering polyethylene. Partially condensed. Since it has the effect of preventing the occurrence of water trees by preventing the occurrence of water trees, it also has the negative effect of lowering the insulation resistance of polyethylene.

That is, there was a drawback that the insulation resistance of crosslinked polyethylene, which has one advantage of high insulation resistance, was reduced. Furthermore, since it has an OH group, it has the disadvantage of increasing the dielectric loss tangent of the insulator, and for this reason, water tree inhibitors cannot be used for high voltage cables with a rating of 66 kV or higher, where the dielectric loss tangent is a practical problem. There was also this inconvenience.

The purpose of the present invention was to solve the above-mentioned drawbacks of the prior art and to provide a novel cross-linked polyethylene insulator capable of suppressing water tree without deteriorating its electrical properties. Our objective is to provide polyethylene electrical cables.

[Means and effects for solving the problem] The gist of the present invention is not to contain the water tree inhibitor in the entire crosslinked polyethylene insulator, but to add it to the inner and outer layers of the insulator, the inner and outer semiconductive layers, or even the inner and outer half of the insulator. The reason is that the tape in contact with the conductive layer contains a water tree inhibitor, thereby leaving an insulating layer that does not contain the water tree inhibitor, thereby preventing deterioration of the electrical properties as a whole effect of the insulator. This is what I did.

[Example] Specific examples of fatty acid metal salts containing an OH group in the molecule include:
Calcium hydroxystearate, aluminum hydroxystearate, zinc hydroxystearate, lead hydroxystearate, barium hydroxystearate, lithium hydroxystearate, manganese hydroxydistearate, calcium ricinoleate, aluminum ricinoleate, zinc ricinoleate, lead ricinoleate , barium ricinoleate, lithium ricinoleate,
Manganese ricinoleate, etc.

Specific examples of fatty acid amides include stearic acid amide,
Oleic acid amide, erucic acid amide, hydroxystearic acid amide, palmitic acid amide, N,N'-ethylenebis-hydroxystearic acid amide, N,N'-
hexamethylene bis-hydroxystearamide,
N, N'-methylenebis-hydroxystearamide, N.

N'-ethylene bis-stearamide, N.

N'-methylenebis-stearamide, N.

Examples include N'-xylylene bis-hydroxystearamide.

Hereinafter, specific examples will be described with reference to the drawings.

Example 1 As shown in the cross-sectional view of the cable in FIG. 1, an internal semiconducting layer 2. Insulator 3. Outer semiconducting layer 4. In a high voltage electrical cable formed from a metal tape shield 5, a holding tape 6 and a plastic sheath 7, the inner semiconducting layer 2 and the outer semiconducting layer 4 are
It is composed of 0.25 parts by weight of 4'-thiobis(3-methyl-6-t-butyl-phenol) and 0.5 parts by weight of calcium hydroxystearate.

Example 2 As shown in the cross-sectional view of the cable in FIG. 2, an internal semiconducting layer 2. Inner layer insulator 31. Insulator 3. Outer layer insulator 3e, outer semiconducting layer 4. Metal tape shield 5. Presser tape 6 and plastic sheath 7
In the high voltage power cable formed from the above, the same additive as in Example 1, that is, 4-4, is added to the inner layer insulator 3i (thickness 0.5 mm) and the outer layer insulator 3e (thickness 0.5 mm).
0.25 parts by weight of '-thiobis(3-methyl-6-tert-butyl-phenol) and 0.5 parts by weight of calcium hydroxystearate are added.

Comparative Example 1 In the cable structure shown in FIG. 1, that is, as shown in the cross-sectional view of the cable in FIG. 1, an internal semiconducting layer 2. Insulator 3. Outer semiconducting layer 4. Metal tape seal, 5. In the high voltage electrical cable formed from the holding tape 6 and the plastic sheath 7, the entire insulator 3 is coated with the same additive as in Example 1, namely 4-4'-thiobis(3-methyl-6-tert-butyl-phenol). ) to 0
25 parts by weight and 0.5 parts by weight of calcium hydroxystearate.

Comparative Example 2 In the cable structure shown in FIG. 1, that is, as shown in the cross-sectional view of the cable in FIG. 1, an internal semiconducting layer 2. Insulator 3. Outer semiconducting layer 4. Metal tape shield 5. Presser tape 6 and plastic sheath 7
This is a cable that does not use additives, that is, a cable that does not have any water-retention measures.

In the above four types of cables, the insulator 3 has a thickness of 3 mm, the conductor 1 is a 100 mm thick copper conductor, and the insulator 3 is crosslinked by a dry crosslinking method using nitrogen gas as a heating medium.

The evaluation method was to inject water into the conductor 1 and the metal tape shield 5 of these four types of cables, apply an AC voltage of 5 kV, 50 Hz between the conductor 1 and the metal tape 5 for 500 days, and energize the metal tape shield 5. The temperature was varied from room temperature to 90°C in 12 hour cycles. After applying electricity for 500 days, the insulator 3 was cut into slices and dyed by boiling with a methylene blue aqueous solution.The number and size of condensate trees (herein referred to as water trees including boat trees) were observed and evaluated.

Table 1 shows the results, the measured values of the insulation resistance of the insulator, and the measured values of the dielectric loss tangent.

(The following is a blank space) It can be seen that both Example 1 and Example 2 in the table have the same water tree inhibiting effect as Comparative Example 1, and the electrical characteristics are equivalent to Comparative Example 2.

In other words, Examples 1 and 2 of this invention are as follows:
Water tree inhibiting agent is placed in the path of water penetration into the insulator, which prevents water tree formation, and since the water tree inhibiting agent is not contained in the entire insulator, it also prevents deterioration of electrical properties. has been done.

Next, as shown in the cable cross-sectional view of FIG. 3, which shows another embodiment, a semiconductive tape layer 81. Internal semiconducting layer 2° insulator 3. Outer semiconducting layer 4. Semiconductive tape layer 8e, metal tape shield 5. In the high-volume piezoelectric cable formed from the holding tape 6 and the plastic sheath 7, semiconductive tapes 81 and 8e containing a water tree inhibitor are placed on the inside of the internal semiconductive layer 2 and the external side of the external semiconductive layer 4. Each was applied.

In this case, although there is a possibility that the water tree inhibiting effect may be reduced to some extent, the electrical characteristics are prevented from deteriorating.

[Effects of the Invention] As explained above, in the water tree inhibiting cross-linked polyethylene cable of the present invention, the water tree inhibiting agent is applied to both or either of the inner and outer conductive layers at locations that serve as entry paths when water penetrates into the insulator. A water tree prevention agent is placed in contact with one or both of the inner and outer layers of the insulator, and prevents water tree by penetrating into the insulator along with water when flooded. Therefore, it is possible to suppress water tree without reducing the electrical resistance of the insulator.

[Brief explanation of drawings]

FIG. 1 shows Embodiment 1 of this invention. FIG. 2 is a cross-sectional view showing the structure of the cross-linked polyethylene power cable of Example 2 of the present invention, and FIG. 3 is a cross-sectional view showing the structure of the cross-linked polyethylene power cable of Example 2 of the present invention. FIG. 2 is a cross-sectional view showing the structure of a crosslinked polyethylene electric cable according to an example. 1... Cable conductor 2... Internal semiconducting layer 3...
- Insulator 31... Inner layer insulator e... Outer layer insulator 4... Outer semiconducting layer 5... Metal tape shield 6... Holding tape 7... Plastic sheath 1.8e... Semi-conductive tape diagram

Claims (2)

[Claims] (1) A water tree inhibiting crosslinked polyethylene cable characterized in that a water tree inhibiting agent is contained in one or both of the inner semiconductive layer and the outer semiconductive layer. (2) A water tree inhibiting cross-linked polyethylene cable characterized in that one or both of the inner layer and the outer layer of the insulator contain a water tree inhibitor.