JPH0359524B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in insulated wires for overhead power distribution,
The purpose is to prevent stress corrosion cracking of the insulated wire and increase its service life. The structure of conventional insulated wires for overhead power distribution is that a separate layer such as polyester tape is placed on top of a conductor made of solid copper wire or stranded wire, and then rubber,
These are either a structure covered with a plastic insulator or a structure in which an insulator is coated on a conductor, and in either case, residual stress generated during wire drawing or stranding exists in the conductor. When overhead insulated wires with this structure are used in outdoor high-voltage and low-voltage power distribution passages, atmospheric moisture such as rainwater can damage the areas where the insulation has been stripped off at the anchorage and branch points caused by overhead line construction. It penetrates into gaps between conductors and insulators, between separators, and between stranded wires. If moisture remains in the above-mentioned gap for a long time, the corrosive action of the oxygen-enriched flame battery will be applied to the conductor where residual stress exists, causing stress corrosion to the conductor and eventually causing the conductor to break due to stress corrosion cracking, which is extremely dangerous in terms of safety. It was hot. To prevent such stress corrosion cracking,
Conventionally, the aim was to stabilize the surface of the conductor against corrosion.
In order to make the conductive metal insensitive to corrosion, which has become more sensitive due to residual stress, a method has been taken to form a chelate compound on the surface of the conductive metal, and benzotriazole has been mainly used as the chelating agent. However, benzotriazole is poorly soluble in water;
It is difficult to apply the chelate film evenly on the conductor, and an unevenly applied chelate film has no lubricity, so when the conductor is straightened with a straightening roll after applying the chelating agent or preheated by passing through an electrode ring, the roll is used. There was a risk that the chelate film would be easily removed by being rubbed with something such as, and the effect would be lost. Moreover, in recent years, air pollution has become severe in chemical industrial areas and around large cities, and rainwater contains various corrosive substances.
When corrosive moisture containing cations and anions such as NH ⁺ ₄ , Cl ^- , SO ^2- ₄ enters, the chelate film on the conductor loses its effectiveness, and the conductor becomes corrosive, eventually leading to stress corrosion cracking. This happened often. The present invention has been made in view of the above points, and it provides lubricity to the chelate film and removes NH + 4 , NH ⁺ ₄ ,
This improves the stability of _the chelate film against corrosive aqueous solutions such as Cl ^- and SO ^2-4 . That is, an insulated wire for overhead power distribution comprising a hard copper stranded wire conductor with a rubber or plastic insulation coating layer provided on the outer periphery thereof, characterized in that an aqueous solution containing a chelating agent and an amphoteric surfactant is applied onto the conductor. This is an insulated wire for overhead power distribution.

[Table] In the present invention, the chelating agent may be trifluorothenoylacetone, oxine, acetylacetone, potassium dithizone xandogenate, etc., but it is best to use benzotriazole or methylbenzotriazole in terms of color fastness and heat resistance. preferable. The amphoteric surfactant is a substance that has a hydrophilic group that becomes a cation and a hydrophilic group that becomes an anion in one molecule, and is preferably an alkyl amino acid that has a molecular structure as shown in the following formula.

[Formula] (R: C ₈ - C ₁₈ alkyl group) For example, when benzotriazole is mixed with an alkyl amino acid at a ratio of 7:3, and an aqueous solution easily dissolved in water is applied on a copper conductor, the copper surface A chelate compound film layer made of benzotriazole is formed on the surface of the copper, and then the alkylamino acids are adsorbed onto this chelate compound film layer, reducing the interfacial tension against wetting with copper and water, and forming a uniform chelate layer on the copper surface. The surface of the chelate layer is always wet because it is uniformly mixed with water from the outside, and the chelate layer is given lubricity to prevent damage caused by rubbing from the outside. Cl ^- , NH ⁺ ₄ , SO ^2- ₄ in rainwater that infiltrates
When the cations (NH ⁺ ₄ , Cu ²⁺ ) and anions (Cl ^- , SO ^2- ₄ ) generated on the surface of the copper conductor come into contact with the alkylamino acid amphoteric surfactant,
Since amphoteric surfactants have reactive groups that become cations and anions when dissolved in water, copper, which is a conductor, loses its action as a corrosive ion through a neutralization reaction. Therefore, stress corrosion cracking resistance is significantly improved. In other words, the present invention adds an amphoteric surfactant that has both a hydrophilic group that becomes a cation and a hydrophilic group that becomes an anion in one molecule to the conventionally used benzotriazole, and then coats it on a conductor. It is characterized by It can be applied evenly and has lubricity. In addition, if a corrosive aqueous solution containing Cl ^- , NH ⁺ ₄ , etc. enters the insulated wire, the amphoteric surfactant will preferentially dissolve in water and become cations and anions, causing corrosion. It causes a neutralization reaction with ions in the aqueous solution and protects the conductor copper or the chelate layer on the copper. Example: Cross-linked polyethylene insulated wire (OC60mm ² , conductor
19/20φ), Examples 1 and 2 in Table 1
An aqueous solution containing a chelating agent and an amphoteric surfactant as shown in Figure 1 was applied to the surface of a copper conductor. For comparison, we also prepared a sample coated with only a chelating agent as shown in the Comparative Example in the table. A sample was taken from each of the electric wires made in this way, the insulator was removed, and these samples were wrapped around a PVC pipe with a diameter approximately 15 _times the _conductor diameter.
The sample was placed in a sealed atmosphere in a desiccator containing 35 g of NH ₄₀ H (PH 9), subjected to a heat cycle of 80°C and 20°C, and the time until stress corrosion cracking occurred in the sample was measured. The results are shown in Table 1.
According to Table 1, 0.2% benzotriazole and 0.1% alkyl amino acid as in Example 1 according to the present invention.
No cracking occurred even after 2,000 hours had passed since the conductor was coated with an aqueous solution containing . Similarly, good results were obtained when an aqueous solution of 0.1% methylbenzotriazole and 0.05% alkyl amino acid was applied as in Example 2. However, as in Comparative Example 1, when only benzotriazole was applied without adding an amphoteric surfactant, cracks occurred after 2000 hours, and when only methylbenzotriazole was applied as in Comparative Example 2, cracks occurred after 1000 hours. The effect of adding the amphoteric surfactant was clear. As mentioned above, the insulated wire for overhead power distribution made according to the present invention exhibits excellent resistance to stress corrosion and cracking for a long time in a corrosive atmosphere.
It is extremely effective when applied to OE and OW electric wires.

Claims (1)

[Claims] 1. Insulated wires for overhead power distribution in which a rubber or plastic insulation coating layer is provided on the outer periphery of a hard copper stranded conductor with or without a separator,
An insulated wire for overhead power distribution, characterized in that an aqueous solution containing a chelating agent and an amphoteric surfactant is coated on the conductor.