Switching Surges Simulation In 500kV AC Extra High Voltage Transmission Lines

Researches on switching surges are connected tightly with the development of electric power system. At the beginning of the development, overvoltage caused by single-phase intermittent grounding arc makes the most serious disaster because of neutral-point non-grounding system, so that the research on it becomes most important. After the neutral-point of system is grounding, as the grade of rated voltage and the length of transmission line and the transmission capacity are lifted, overvoltage of switching off transformers and lines of no-load operation becomes very serious. Because of less overvoltage energy of switching off transformers of no-load operation, which can released by using lighting arresters, the research on switching off lines of no-load operation becomes most important. Recent years, because of the development of extra high voltage and the construction of long distance transmission lines, switching surges have new changes, such as the capacitance effect of long distance line of no-load operation will make a very high rising of voltage, on the basis it makes switching surges of very high amplitude, and so as the reclosing. As the improving of breakers and using of reactors, the amplitude of overvoltage and the probability arising overvoltage of switching off lines of no-load operation are reduced obviously, so that switching in lines of no-load operation, and so as the reclosing, becomes one of the most typical and serious switching surges in the extra and ultra high voltage grid, and the most important research target.Switching surges are not only related to the operating modes of power system but also to the allocations and performances and parameters of devices in the system tightly. The overvoltage levels are differences due to different system conditions, so the switching surges in extra high voltage grid becomes one of the most important research target.First, the principle and influencing factors and limiting measures of common switching surges are introduced in the paper. Then, the basic elements of PSCAD/EMTDC (switching surges simulating software, Version 4.0.2) are introduced. Based on the 500kV transmission lines in Zhejiang provincial power system a switching surges equivalent model is established. Using the software, the overvoltage level and variation regularities and influencing factors of extra high voltage grid are simulated, especially the influencing factors of switching in lines of no-load operation and the ability of overvoltage restriction of lighting arrester.