OFケーブルの銅化合物劣化に関する絶縁油分析診断法の開発と現場適用

抄録

In recent years, breakdown failures occur in joint boxes of oil-filled cables associated with the adhesion of copper compounds, such as copper sulfide or organocopper compounds. This is the adhesion degradation of copper compounds due to electric charging. Therefore, the degradation should be diagnosed for keeping its high reliability. However, the degradation cannot be predicted by the conventional diagnostic methods based on dissolved gas analysis, because the definition of degradation aspect in the method does not assume this degradation. Therefore, a new degradation diagnosis method is developed based on insulating oil analysis and the trend of the concentration of dissolved copper in the oil and the concentration of combustible gas generated due to the degradation. However, it is not possible to measure the concentration of dissolved copper in the past 30 years, because the majority of oil-filled cables are over 30 years old. Therefore, the past concentration of dissolved copper is calculated by the dielectric loss tangent value of oil, which has been traditionally measured. As a result, the consistency rate of the diagnostic methods was confirmed to be more than 80% by comparison with the results of demolition investigations of the using joint boxes.