Factors influencing insulation capacity of overhea

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Factors affecting the insulation capacity of overhead lines and Countermeasures. Overhead power transmission lines are exposed to the wilderness for many years. They are often subject to the erosion and test of severe natural environment and natural disasters such as violent storms, lightning, frost and fog, and are prone to external damage. In addition, with the continuous development of local industry and agriculture, especially the serious over standard problems such as exhaust gas and waste residue discharged by chemical and mineral enterprises are difficult to be fundamentally solved. These objective conditions threaten and damage the insulation capacity of power transmission lines to varying degrees. In order to ensure the safe and economic operation of the line, according to the statistics on the faults of some overhead transmission lines made by Shangluo Power Supply Bureau in 1999 (see Table 1), starting from ensuring the insulation capacity of the line, combined with the characteristics and experience of line operation in mountainous areas, the causes affecting the insulation capacity of the line are found out, and the solutions are put forward

Table 1 Statistics of some overhead line faults

people often say that "diseases enter from the mouth". In order to effectively reduce line faults, we must first strictly control the quality of raw materials to prevent unqualified and hidden defects from being brought into line operation, especially the materials that directly affect the insulation capacity of the line, such as the quality of insulators. Therefore, in the procurement of insulators, priority should be given to large-scale products with good reputation or products with operating experience to prevent unqualified products from going online

For example,

2.2 strictly control the construction quality

in the acceptance of the road, in the past, we often only paid one-sided attention to the common faults and operation channel cleaning of the line foundation, pole tower and cross crossing single arm tensile testing machine, and neglected the other two important processes: first, the sag of the conductor and ground wire was not checked according to the design value, resulting in the sag being too large or too small. Under adverse weather conditions (tornadoes, etc.), A preparation method presented by researchers at Oak Ridge National Laboratory of the U.S. Department of energy was introduced. The insulation gap between the starting conductor and ground wire to the tower was insufficient or exceeded the load force, resulting in discharge, disconnection and other faults; Second, before installation, the energy-saving effect of plastic water supply pipe can reach 50% load mark. After the spring pin is inserted, whether the insulator ball head can slip off automatically, whether the ball head is loose, whether the insulator ball head and steel cap are rusted, and whether the porcelain skirt has bubbles, cracks, deformation and other appearance inspection and cleaning are not careful. The shake test of each piece of porcelain insulator (the insulation resistance measured by 5000v megger shall not be less than 500m Ω) was not strictly implemented on site. In this way, it is easy to bring varying degrees of hidden dangers to the insulation capacity of the line

2.3 strengthen the "salt density" analysis and timely adjust the classification of polluted areas

by measuring the "equivalent attached salt density" (ESDD), it can be found that the flashover voltage of polluted insulators decreases with the increase of ESDD. Therefore, in the operation practice of the line, ESDD should be measured regularly with the change of the surrounding environment of the line. According to the change of ESDD, the grade distribution of polluted areas shall be adjusted in time, and the appropriate insulation level shall be selected to ensure the safe operation of the line

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