The Research On Over-Voltage And Restrain Strategy For UHV Transmission Line

The overvoltage of power system ,as an essential project in 1000kV ultra high voltage (UHV) grid,should be studied deeply.It not only affects the insulating strength design of electric equipments,such as transformers,switches,and transmission lines,but also is concerned with the fact that whether the power system operate safely and reliably.1000 kV transmission line parameters as well as system capability features make the overvoltage more serious than ordinary extra high voltage (EHV) lines. Therefore,overvoltage is the crucial issue of the 1000 kV ultra high voltage transmission technique and is the decisive factor of the 1000kV UHV electric grid design .Since the UHV transmission line insulators can only bear relatively low overvoltage margin and overvoltage will lead to insulators breakdown, with power system's huge comprehensive economic losses for replacing insulators,it is necessary to consider that how to limit internal overvoltage of UHV lines.The thesis analyzes the mechanism of power frequency overvoltage and switching overvoltage of the 1000kV Jindongnan-Nanyang-Jingmen transmission line as well as influencing factors theoretically,gives the models of the transmission system and has calculated parameters,then has studied the restrain strategy of overvoltage profoundly.Next,with PSCAD/EMTDC ,this thesis carries out simulating and calculating about temporary power frequency overvoltage and transient switching overvoltage of the 1000kV Jin-Nan-Jing line ,analyzing measures such as using high voltage parallel reactors to restrict power frequency overvoltage as well as adoption of MOA and switching parallel resister to restrict operating overvoltage .On this basis, summarizes the regular pattern of internal overvoltage of UHV lines,proposes the solution for inhibiting and controlling power frequency overvoltage and switching overvoltage.