Study on the Effect of Optimizing the Configuration of Metal-oxide Arresters in UHV Engineering on Suppressing Slow-front overvoltage

The overvoltage level of UHV substation, transmission line and the characteristics of metal-oxide arrester (MOA) are the foundation of insulation co-ordination. Deep suppression of overvoltage level of UHV system is conducive to improving the insulation margin of transmission lines and substations, and even reducing their insulation level. In this paper, under the conditions of different system structures and line lengths, EMTP program is used to calculate and study the measures of suppressing slow-front overvoltage by adopting lower rated voltage MOA in UHV substation and installing line type MOA near the midpoint of the transmission line. The results of the this study show that the use of lower rated voltage MOA or the installation of line type MOA near the midpoint of line can lower overvoltage with a length of 400km or less to about 1.6p.u. or less. For the distance of transmission line that more than 400 km, it is necessary to combine the two suppression measures to achieve the same suppression effect.