| In recent years,China’s wind power,photovoltaic and other renewable energy generation has been vigorously developed,these high proportion of renewable energy generation with strong uncertainty access to the grid has brought huge challenge to the stable operation of the power system.Pumped storage power stations have high efficiency and reliable regulation performance,which can well cope with and alleviate this impact brought by the high proportion of renewable energy generation to the grid,therefore,China will accelerate the construction of pumped storage power plants during the 14 th Five-Year Plan period.Large-scale(large and medium-sized)pumped storage power stations are generally located in remote mountainous areas with small building space,and the study of overvoltage and its protection in such power station has important engineering application value and significance under the requirement of high integration and reliability of electrical equipment.This paper carries out research on such pumped storage power stations and their protection based on actual engineering parameters,with the main research content and conclusions including the following:(1)Simulation model analysis and modelling of lightning and operating overvoltage in such pumped storage power stations based on PSCAD(Power Systems Computer Aided Design)simulation software,in conjunction with the electrical wiring and equipment layout characteristics of pumped storage power stations,and parameter setting based on a pumped storage power station project example.(2)Based on a simulation study of lightning overvoltage in pumped storage power stations under different lightning strikes and operating modes,it was concluded that,for the example pumped storage,the overvoltage at the top of lightning strike 1# tower(the nearest tower to the switchyard)was higher than the lightning bypass overvoltage,and that the lightning overvoltage was most severe when the power station was operated in the “single line,single transformer” mode.Based on a simulation study of operating overvoltage in pumped storage power stations,it was concluded that the overvoltage of the transformer in the example of a pumped storage power station is more serious when the transformer is separated from the no-load transformer;a study was carried out on the effect of the presence or absence of cables and different cable lengths on the lightning and operating overvoltage of the transformer in the power station,and it was concluded that the access to cables between the transformer and the switching station is conducive to reducing the value of the lightning overvoltage of the transformer,and the decrease increases with the length of the cables.However,the access to the cable has little effect on the transformer operating overvoltage values.(3)The surge arrester selection work was carried out,comprehensive consideration of parallel resistance and surge arrester on the operating overvoltage limit effect and the actual operation of the power station reliability and engineering input and other factors,for a pumped storage power station example,the Zn O oxide arrester can be used to replace the parallel resistance;lightning overvoltage limit effect of different arrester configuration simulation was studied.The effect of busbar length on the lightning overvoltage of the main electrical equipment in the pumped storage power station was studied,and it was concluded that the change in busbar length has little effect on the value of lightning overvoltage of the relevant electrical equipment;in addition,a simulation study was conducted on the discharge current and limiting measures of surge arresters at different locations in the power station,and it was concluded that surge arresters can be limited by reducing the tower inductance and grounding resistance to limit the discharge current amplitude of surge arrester.Finally,based on the above analysis and research,overvoltage protection schemes and specific recommendations are given for pumped storage power station projects. |
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