Temporary overvoltages in the Vietnam 500 kV transmission line

This paper investigates temporary overvoltages (TOVs) in Vietnamese 500 kV transmission lines. The accurate modeling of the system components as well as lines, transformers, machines, loads, shunt reactors and surge arresters is presented by taking into account the saturation of transformers and shunt reactors and corona V-I characteristics. The excitation systems of machines are also used in this study. Several events that can produce high TOV levels such as three-phase load rejections and single-phase opening with contingency are examined by using the EMTP. The energy dissipated in the surge arresters is determined. Finally, the methods of limiting the magnitude and duration of TOV levels applied to equipment are presented. A program capable of interfacing with the EMTP is developed to study TOVs and other transient phenomena. The study is useful for constructing and operating such a transmission line.