Overvoltage And Insulation Coordination Of EHV Substation In The High-altitude Area

With the rapid development of the social economy and the expansion of the power grid, there is more intensive power grid located in Tibetan Plateau and Yunnan-Guizhou Plateau. It is very important for the reliability and safety of the power system to study the overvoltage and insulation coordination of EHV substation in the high-altitude area.The overvoltage and insulation coordination of EHV substation in the high-altitude area is based on the modified calculation of the insulation strength of EHV substation in the high-altitude area. This paper presents the relationship between the altitude and the insulation strength, and the insulation strength of a'hai hydropower plant was calculated considering the impact of the altitude. Using the electromagnetic transient analysis program ATP-EMTP, the lightning-overvoltage model was established based on the structure chart and parameters of a'hai hydropower plant and transmission lines, and the lightning overvoltage was calculated. The relationship between the lightning overvoltage and the lightning-attack position was studied, and the relationship between the lightning overvoltage and the distance from the transformer to the top of the dam to the terminal of the transmission lines was also studied. Overvoltage-control methods were discussed. The switching-overvoltage model was established based on the structure chart and parameters of a'hai hydropower plant and transmission lines, and the switching voltage was calculated. The necessity and feasibility of the Elimination of closing resistors on EHV circuit breakers was discussed in this paper. At last, the concept of rigid staggered closing was introduced, and the formula on the closing time of each line was deduced.