Mechanism of Status Evaluation for Water Blocking Buffer Layer of High Voltage Cable Based on Characteristic Gas Analysis

The corrosion and ablation of water blocking buffer layer of high-voltage cables are accompanied with the production of various gases. By selecting characteristic gases and analysing the corresponding relationship between their concentration and the corrosion/ablation stages, it is possible to evaluate the status of the buffer layer. This article analysed the time-varying characteristics of gas concentration during the corrosion and ablation of water blocking buffer layers, revealed the mechanisms of the gas production, and proposed a method for evaluating the status of the buffer layer based on characteristic gas analysis. Results indicated that both the corrosion and ablation processes of the buffer layer produced H 2 , CH 4 and CO 2 , but the ablation process generated additional gases including C 2 H 6 , C 2 H 4 , C 2 H 2 , and CO. The H 2 concentration was positively correlated with the amplitude of applied voltage, water content, and surface pressure, and saturated after a period of generation. On this basis, the mechanism of H 2 production during the corrosion stage, and the decomposition of polyethylene terephthalate (PET) accompanied by hydrocarbon gas production during the ablation stage of the buffer layer were investigated. By detecting the concentration of H 2 in the cable, the overall damage level of the buffer layer can be determined. Additional detection on C 2 H 6 , C 2 H 4 , C 2 H 2 and CO gases can determine whether the buffer layer is in a corrosion state. Finally, the effectiveness of evaluating the status of buffer layer by characteristic gas analysis was proved on new and on-site 110 kV cables.