1. Xuefeng Mountain Energy Equipment Safety National Observation and Research Station of Chongqing University Chongqing 400044 China; 2. Xuchang Power Supply Company State Grid Henan Electric Power Company Xuchang 461000 China; 3. State Grid Hunan Extra High Voltage Substation Company Changsha 410000 China
Abstract：With the rapid development of the power system, the long-term safe and stable operation of overhead lines is of great importance. The galvanized clamps are the key connection component. Prolonged exposure to the natural environment causes them to suffer from varying degrees of atmospheric corrosion, resulting in localized failures and shortened operating life. However, there is no uniform standard for identifying the corrosion status of galvanized clamps. In current research, manual identification is somewhat subjective, and machine learning requires a large amount of data support. Other methods, such as ultrasonic reflection, are not suitable for overhead lines. To address these issues, this paper investigates the corrosion temperature rise characteristics of galvanized clamps and proposes a feature quantity to characterize the degree of atmospheric corrosion of galvanized clamps. Based on the measurement of the abnormal temperature rise, the corrosion state of the galvanized clamps can be effectively identified. Firstly, the galvanized parallel clamps were considered as the object of research. An accelerated corrosion and thermal cycling test circuit was set up in the laboratory. The homemade electromagnetic induction coils were used as a stabilized AC power supply. The alternating wet and dry corrosion method was employed to simulate acidic, alkaline, and neutral corrosive environments in the atmosphere. The test current ranged from 240 A to 420 A with a step of 60 A according to IEEE and Chinese standards. Secondly, the surface states of galvanized clamps in various corrosive environments were observed with an electron microscope. The corrosion products and development processes were analyzed. The surface temperatures were measured and recorded by an infrared camera to characterize the temperature rise of the clamps in various corrosive environments. Finally, based on the test results, a feature quantity was defined and extracted, and the corrosion grading method and the fitting equation were proposed. The acid corrosion process includes the formation of the white corrosion layer, the accumulation of the layer, and the exfoliation of the corrosion products. The products are mainly Al2O3, zinc sulfate salts, and SO2, which aggravate corrosion. The alkaline corrosion process is similar to the acidic one, but most of the products are insoluble substances and have a protective effect on the inner aluminum layer. The neutral corrosion can be interpreted as the process of "dissolution - deposition - dissolution". The clamps have maximum temperature rise in an acidic environment. At the low conductivities of the solutions, the temperature rise curves are approximately linear for all of the environments. As the conductivities increase, the temperature rise gradually saturates. The corrosion rate also shows an upward trend as the current increases. The following conclusions can be drawn from the tests and analysis: (1) The acidic environments have the greatest corrosive effect on galvanized clamps, followed by the alkaline and saline environments. (2) Under the same conditions, the temperature rise gradually decreases in acidic, alkaline, and saline environments. The conductivity and current are positively correlated with the temperature rise. (3) The corrosion feature quantity k can objectively characterize the corrosion state of galvanized conductive clamps, and realize accurate identification and grading of corrosion.
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2024, Vol. 39 
