JPH06251639A - Water tree resistant cable - Google Patents

Abstract

PURPOSE:To provide a cable having high water tree resistance. CONSTITUTION:This water tree resistant cable has an insulation composition made of one or both of 0.1 to 1.0 pts.wt. of a phenol age resistor and a phosphor age resistor added to 100 pts.wt. of base polymer mainly composed of polyethylene having extra low density between 0.89 and 0.91g/cm<3> laid as an insulator on a conductor. Thus, water tree resistance is increased as a result of reducing the crystallinity of the base polymer, and alleviating the condensation of water at an abnormal electrical filed section via the addition of the age resistor. The occurrence of a water tree at an insulation layer can therefore restrained, and the service life and reliability of a power cable can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a water resistant tree cable insulating material composition capable of reducing the generation of water trees generated when a power cable using crosslinked polyethylene as an insulating material is subjected to long-term water immersion. Regarding waterproof tree cable.

[0002]

2. Description of the Related Art Crosslinked polyethylene (XLPE) has been widely used as an insulating material for power cables. In a crosslinked cable using this crosslinked polyethylene as an insulating material, it is known that water tree is generated due to long-term immersion and application of electricity as one of the insulation deterioration. It is absolutely necessary to control the generation of water trees. Water tree is a phenomenon that occurs when water acts on an abnormal electric field portion (foreign matter, void, protrusion) in an insulator, but the generation mechanism has not been clarified yet. According to the researches to date, it is considered that polyethylene easily causes water tree because polyethylene is a non-polar and hydrophobic polymer, so that it easily causes electric charge condensation of water in the abnormal electric field part. (Takahashi et al., 19th Symposium on Electrical Insulation Materials VII-3 (198
6)). It is also known that the water tree resistance of polyolefin changes depending on its crystallinity.

[0003]

Conventionally, in order to improve the water resistance of polyethylene, the method of blending polyethylene with other polymers and the crystallinity of polyethylene have been studied. Does not provide a polyethylene-based insulating material having sufficient water resistance.

The present invention has been made in view of the above circumstances, and provides an insulating material composition for a water-resistant tree cable and a water-resistant tree cable capable of reducing the occurrence rate of a water tree caused by flooding and charging of a power cable. Has an aim.

[0005]

A water-resistant tree cable according to the present invention comprises 100 parts by weight of a base polymer mainly composed of ultra-low density polyethylene having a density of 0.89 to 0.91 g / cm ³ , and a phenolic aging preventive agent. An insulating material composition obtained by adding 0.1 to 1.0 parts by weight of one or both of the agent and the phosphorus-based antioxidant is provided on the conductor as an insulator.

[0006]

The above insulating material composition has a density of 0.89 to 0.91.
0.1 to 1.0 parts by weight of one or both of a phenolic antioxidant and a phosphorus antioxidant are added to 100 parts by weight of a base polymer mainly composed of g / cm ³ ultra-low density polyethylene. By reducing the crystallinity of the base polymer and reducing the condensation of water in the abnormal electric field portion by adding the antioxidant, the water tree resistance is improved.

[0007]

The present invention will be described in detail below. The water resistant tree cable insulation composition according to the present invention has a density of 0.8.
Ultra low density polyethylene of 9 to 0.91 g / cm ³ (hereinafter V
LDPE) is mainly added to 100 parts by weight of one or both of a phenol-based antioxidant and a phosphorus-based antioxidant, and 0.1 to 1.0 part by weight thereof is added.

VLDP which is the main constituent of this base polymer
E is a kind of linear polyethylene produced by the medium and low pressure method using a Ziegler type catalyst. Α to ethylene
-Introducing a large number of short chain branches of olefins to reduce the crystallinity, and ordinary low density polyethylene (LDPE)
Density of 0.91 to 0.93 g / cm ³ , 0.89 to
A lower density VLDPE of 0.91 g / cm ³ is obtained. This VLDPE is a polyethylene having a lower crystallinity and a slightly higher melting point than LDPE, and has a melt flow rate (MFR) of about 0.8 to 0.9 g / 10 min. As the base polymer, VLDPE may be used alone, or VLDPE may be used as a main component and blended with another polymer such as LDPE, another polyolefin, EP rubber or EEA.

To this base polymer, various subcomponents used in the production of ordinary crosslinked polyethylene for cables, for example, various crosslinking components such as peroxide type crosslinking agents, plasticizers, flame retardants and coloring agents are added. be able to.

As the anti-aging agent added to this base polymer, one or both of a phosphorus-based anti-aging agent and a phenol-based anti-aging agent are used, and a phosphorus-based anti-aging agent and a phenol-based anti-aging agent are used respectively. You may mix and use 1 or more types. The phosphorus-based antioxidant can be appropriately selected and used from various commercially available products containing phosphoric acid esters, and the phenol-based antioxidant can also be appropriately selected from various commercially available products containing a phenol derivative. Can be used. The amount of these antioxidants added is in the range of 0.1 to 1.0 parts by weight, and most preferably 0.1 to 0.2 parts by weight, based on 100 parts by weight of the base polymer. If the amount added is less than 0.1 part by weight, the water tree suppressing effect of the obtained insulating material composition cannot be sufficiently obtained, and if the amount added is more than 1.0 part by weight, the water tree suppressing effect reaches a peak. And the physical properties of the base polymer are adversely affected, which is not preferable.

This insulating material composition can be coated on a cable conductor to form an insulating layer by a method similar to that of conventional crosslinked polyethylene. That is, an insulating material composition obtained by adding the above antioxidant to the base polymer is kneaded by heating,
An insulating layer having a desired thickness is formed on the conductor by the common extrusion / dry crosslinking method.

The power cable manufactured as described above has a base polymer 10 mainly composed of VLDPE.
An insulating material composition obtained by adding 0.1 to 1.0 parts by weight of one or both of a phenolic antioxidant and a phosphorus antioxidant to 0 part by weight is used, so the crystallinity of the base polymer is To reduce the water tree resistance and reduce the condensation of water in the abnormal electric field part by adding an anti-aging agent, which suppresses the water tree and extends the life and reliability of the power cable. It is possible to improve the sex. Hereinafter, the effects of the present invention will be clarified by experimental examples.

(Experimental example) Density is 0.89 to 0.90 g / c
m ³ , MFR 0.8 to 0.9 g / 10 min, crystallinity about 15
% VLDPE as a main component, and a commercially available anti-aging agent was added to a base polymer in which a cross-linking agent was blended to obtain an insulating material composition. The antiaging agent used here is as follows.・ Phosphorus anti-aging agent (A): Adeka Argus
ADEKA STAB-Phosphorus anti-aging agent (Old B): Sand Company Sand Starb-Phenolic anti-aging agent (Old C): Sumitomo Chemical
Sumilizer-Phenolic anti-aging agent (Anti-D): These anti-aging agents were added as shown in Table 1 to 100 parts by weight of Irganox base polymer manufactured by Ciba-Geigy Japan, and each of Examples 1 to 4 was added. An insulating material composition was prepared, and a current XLPE (comparative example) was added to these four kinds of compositions for comparison, and a three-layer common extrusion / dry cross-linking method was used to form an insulating thickness of 3 mm and a conductor cross-sectional area of 100 m.
A m ² cable was prototyped. Figure 1 shows the structure of the test cable
Shown in. In FIG. 1, reference numeral 1 is a water resistant tree cable, 2
Is a conductor (cross-sectional area 100 mm ² ), 3 is an insulating layer (3 mm
Thickness), 4 is an inner semiconductive layer (1 mm thick), 5 is an outer semiconductive layer (0.8 mm thick), 6 is a shield layer (0.44 mm)
Thickness) and 7 are sheaths (2.2 mm thick).

10 kV is applied to each cable
1kHz, internal / external water injection, 90 ° C heat cycle (8h
Power was applied for up to 6 months depending on the flooded power application conditions (rON, 16 hr OFF). The insulating layer of each cable that underwent this water immersion test was taken out, and the number of water trees generated was examined by an optical microscope. The results are shown in Table 1.

[0015]

[Table 1]

From the results shown in Table 1, a cable prepared by using an insulating material composition prepared by adding one or both of a phosphorus anti-aging agent and a phenol anti-aging agent to a base polymer mainly composed of VLDPE is: It was confirmed that the water tree resistance was improved compared to the current cable.

[0017]

As described above, according to the present invention,
Since an insulating material composition prepared by adding 0.1 to 1.0 parts by weight of one or both of a phenolic antioxidant and a phosphorus antioxidant to 100 parts by weight of a base polymer mainly composed of VLDPE is used. , The water-tree resistance is improved by lowering the crystallinity of the base polymer, and the water-tree generation in the insulating layer is prevented by reducing the condensation of water in the abnormal electric field part by adding an antioxidant. As a result, the life of the power cable can be extended and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a water resistant tree cable used in an experimental example of the present invention.

[Explanation of symbols]

1 ... Water resistant tree cable, 2 ... Conductor, 3 ... Insulation layer.

Claims (1)

[Claims] 1. A base polymer 100 mainly composed of ultra-low density polyethylene having a density of 0.89 to 0.91 g / cm ^3.
A water-resistant tree cable, wherein an insulating material composition comprising 0.1 to 1.0 parts by weight of one or both of a phenol-based antioxidant and a phosphorus-based antioxidant is added to a conductor as an insulator.