A study of Ferranti and energization overvoltages case of 500 kV line in Thailand

Since 1989 the first 500 kV line established, EGAT (Electricity Generation Authority of Thailand) has constructed a number of 500 kV lines. Therefore study related to the overvoltages is necessary to ensure safe operation. This paper presents the study results related to the Ferranti and energization overvoltages that could be effected by some factors. In EGAT 500 kV lines normally the shunt reactors are adopted at the line´s two terminals. Meanwhile the surge arresters have also been installed at line´s two terminals in parallel with the shunt reactors. The reclosing resistor of a circuit breaker is also attached in some cases. Ferranti overvoltages and energization overvoltage are the most common overvoltages in the EHV systems. As these components can have an effect on the values of overvoltages, the study of the effect of these components, shunt reactor, surge arrester, reclosing resistor, on the Ferranti and energization overvoltages should be carried out before the particular line to be commissioned. This study has been carried out by the simulation calculation using EMTP. Two EMTP versions (MicroTrain and ATP) have been used to check the calculation results