JPS6236521B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a detection method capable of detecting the occurrence of stress corrosion cracking in a copper conductor of an overhead distribution insulated wire that has already been installed and is in actual use. The structure of a normal insulated wire for overhead power distribution is to provide a separator such as polyester tape on the outside of a conductor made of hard copper wire or hard copper strands, and
A structure in which the conductor is coated with a plastic insulator or a structure in which the conductor is directly coated with an insulator without a separator, and in either case, the conductor has residual stress during wire drawing or stranding or due to drum winding. Existing. When an insulated wire for overhead power distribution having such a structure is used for an outdoor high-voltage or low-voltage distribution line, moisture, particularly rainwater, enters between the conductor and the insulator through the wire tie-down section, branch section, or other portion where the covering insulator is stripped off. If moisture remains in the gap for a long time, corrosion cell effects such as oxygen concentration cell effects will be applied to the conductor with residual stress, which will cause stress corrosion cracking in the conductor, which will eventually cause the conductor to break. It may arrive. For this reason, on actual railway lines, there is a risk that overhead wires may suddenly break and come down, and there is a need to predict stress corrosion cracking in overhead distribution insulated wires, but until now there has been no simple detection method that can be done on-site. This invention was made in view of the above-mentioned points, and when the actual state of stress corrosion cracking was investigated from removed overhead distribution insulated wires, the following was discovered. That is, when the rainwater that entered the removed wires was broken due to stress corrosion cracking, it was analyzed and found to be acidic, while the rainwater that entered the removed wires that were not broken showed alkalinity. Typically, copper conductors for overhead distribution insulated wires are coated with benzotriazole for the purpose of preventing discoloration and corrosion. An aqueous solution of benzotriazole is alkaline, and when rainwater enters an overhead power distribution insulated wire and forms standing water, some of the benzotriazole adhering to the surface of the copper conductor is eluted into the standing water and becomes alkaline. Then, a neutralization reaction occurs with acidic ions (CO ₂ , NO _x , SO _x ) in the rainwater.
As a result, ammonium ions remain in the rainwater,
Although it is alkaline, stress corrosion occurs when copper, which is a conductor, reacts with ammonium ions, and the remaining rainwater after the ammonium ions are consumed becomes acidic. When the conductor copper and ammonium ions did not react, the rainwater remained alkaline. Therefore, it has become possible to detect stress corrosion cracking by measuring the pH of rainwater that has entered electric wires. Next, the present invention will be explained with reference to examples. Example: 50 of existing 6.6KVOC electric wires that have been installed for 5 years
For each span, rainwater inside the wire was extracted using a water sampler from each tie-down section, and PH was measured. Of the 50 spans of wires, rainwater could be collected from wires with 33 spans.
When the four spans of wires showing 7) were removed and the conductors were examined, stress corrosion cracking was observed in all of them, so new overhead wires were installed, and the rainwater in the remaining 29 spans of wires showed alkalinity. It continued to be used as a railway line, but even after two years had passed, there were no disconnections due to stress corrosion cracking in any of the spans. The table below shows the discoloration of the conductor for 50 spans of the 6.6kVOC wire shown in the example.

【table】

[Table] Also, 2 of the 29 spans where the accumulated water showed alkalinity
The PH measurement and conductor discoloration after a year had hardly changed from the table above, and no stress corrosion cracking was observed. As shown in the examples above, according to the present invention,
Collect accumulated water inside the electric wire from one end of the existing electric wire, and check the pH.
It is extremely effective in practice because stress corrosion cracking can be easily detected by measuring .

Claims (1)

[Claims] 1. Stress in overhead distribution insulated wires characterized by detecting the presence or absence of stress corrosion cracking in existing overhead distribution insulated wires by measuring the pH of accumulated water that has entered between the copper conductor and insulation coating of the existing overhead distribution insulated wires. Corrosion crack detection method.