Research On The Overvoltage Issue Of The 1000kV Jin-Nan-Jing Line

The Overvoltage of the power system ,as an essential project in the 1000 kV power network ,must be studied. It not only affects the insulation intension design of power equipment,such as transformers,switches,and transmission lines,but also is concerned with the fact that whether the power system can operate safely and reliably.1000 kV transmission line parameters as well as system capability features make the overvoltage more serious than ordinary extra high votage (EHV) line. Therefore,overvoltage is the key issue of the 1000 kV ultra high votage (UHV) transmission technique and also the decisive factor of the 1000kV UHV electric network design . Since the UHV transmission line insulators can only bear relatively low overvoltage margin and overvoltage will lead to insulators puncture, with power system's huge comprehensive economic losses for replacing insulators,it is necessary to consider that how to limit internal overvoltage and lower the shielding failure outage rate caused by lightning at the beginning of the construction of UHV lines. The paper analyzes all kinds of overvoltage styles of the 1000 kV JinDongnan-Nanyang-Jingmen transmission line as well as factors affecting them ,proposing programmes for inhibiting and controlling overvoltage. Frist of all,the article brings forth its research tools and content on the basis of an introduction of the present state of research on internal overvoltage and shielding failure outage rate for lightning overvoltage of the UHV overhead transmission line.Then the thesis provides a systematic model and calculates systematic parameters of the 1000KV Jin-Nan-Jing line,confirmimg research methods and process of the internal overvoltage .In the following part,this paper theoretically explains the principles of power frequency overvoltage and operation overvoltage,focusing on three kinds of line overvoltage i.e.capacity effect of unloaded line ,load shedding and single-phrase ground faults,which are three components based on power frequency,as well as inhibition of power frequency overvoltage by different installation positions of the high voltage parallel reactor. When analyzes switching unload line ,the article especially refers to switching phase , non-synchronous switching of circuit breaker and the influence of MOA and switching resister in the circuit breaker on switching overvoltage.Then,with ATPDraw ,this thesis carries out emulating calculation over temporary frequency overvoltage and transient switching overvoltage of the 1000KV Jin-Nan-Jing line ,analyzing measures such as using high voltage parallel reactor to restrict frequency overvoltage as well as adoption of MOA and switching parallel resister to restrict operation overvoltage .The results show as follows:The effect on inhibiting frequency overvoltage is better if we install high reactor at the end of the line rather than at the beginning or both ends;if we only install arresters at both ends of the line to restrict operation overvoltage,practical requirements of the project cannot be reached;if we install arresters at both ends and use switches with switching resistor simultaneously ,we can effectively lower overvoltage from three-phase switching unloaded line and transferred overvoltage after cutting off faults.As for lightning overvoltage of the UHV over-head transmission line ,it is very meaningful for the safety and steadiness of the UHV system to exactly evaluate line's ability to bear lightning stroke for line tripping accidents caused by shielding failure have taken up a large percentage .The thesis carries out research on the shielding effect of ground lines of several UHV transmission towers with the help of modified EGM. The results show that the tower with parallel arranged wire ,V-shaped insulator middle phase ,I-shaped side phase is the best. As for other types of tower ,reducing protecting angle can help achieve better shielding effects.