Running And Residual Life Management For Strain Clamp Of Overhead Line

In the daily transmission process, due to the long exposure to the air environment and the task of the transmission current, the temperature of strain clamp is high and the corrosion is significant. Because strain clamps are usually located at the place tens of meters from the ground and long-term load high voltage current, frequent sampling inspection is difficult. Scrapping directly will cause great waste of resource. So it is urgent to put forward a convenient and accurate online monitoring scheme. Infrared temperature measurement technology has the advantage of measuring the temperature reflecting the residual life of strain clamp easily, which effectively overcomes the difficulty of inconvenient inspection. Therefore it is very necessary to research the residual life model of strain clamp according to the temperature.In this dissertation, the failure causes and mechanism of this invalid strain clamp were analyzed. Corrosion of strain clamp in air was simulated according to the characteristics of the failure process. The residual life model of strain clamp was established by relating the corrosion process to the heating process. The failure causes and mechanism of this invalid strain clamp were analyzed by means of optical microscope, SEM, EDS and others. The corrosion rate and influential factors of strain clamps were researched by dry-wet immersion test and electrochemical methods. The relationship between the corrosion degree and the corrosion time was established on the corrosion date. The relationship between the corrosion time and the temperature was established by the heat balance of strain clamp and the relationship between the corrosion degree and the corrosion time. According to the critical failure criterion of strain clamp, the critical state of the wire clamp is determined, and the remaining life is predicted. At the same time, the control scheme and the method of using the residual life model were put forward.The experimental results show that:some aluminum strand is broken in the compression process, so rain and other corrosive liquid is easy to flow into the pressure pipe and the interface between pressure pipe and aluminum cable steel reinforced (ACSR) is corroded. The electric resistance of strain clamp increases due to the accumulation of corrosion products. The temperature of strain clamp increases with the increase of resistance. The thermal equilibrium is broken when the temperature of strain clamp exceeds the critical temperature of thermal break down. The temperature will continue to rise, and leading to the failure of strain clamp eventually.The corrosion of the strain clamp occurs preferentially at the defect and then spreads to the surrounding area. In stage of drying, corrosion products will produce micro cracks, and even peeling off due to dehydration. The spalling area will be corroded again as soon as exposed to the corrosive liquid, which results in the longitudinal growth of corrosion products. The corrosion environment has a certain influence on the corrosion rate of strain clamp. Increasing temperature and decreasing pH of solution will both accelerate corrosion of strain clamp. At the same time, the tight degree of strain clamp can also affect the corrosion rate. The empirical formula of environmental influencing factors is obtained based on accelerated test data and measured data. The thermal radiation coefficient of strain clamp was determined by temperature rise test and the temperature resistance model is verified by the temperature rise test. The residual life prediction model of strain clamp with temperature was obtained by combining the corrosion rate function of the laboratory, the heat balance equation and the critical failure criterion of thermal breakdown.