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This paper investigates the overvoltage due to different types of switching in Nam Theun 2 - Roi Et 2 500 kV network. The study is based on PSCAD/EMTDC performed for a guide line for 500 kV operations in Lao PDR. The appropriate representation for the various components such as transformer, transmission line, circuit breaker, surge arrestor and shunt reactor, have been selected. The study covers two most severe cases: line energization and re- energization due to single phase to ground and three phases to ground faults, and switching under different load conditions is considered. In the series of simulations, the maximum overvoltage is determined. The maximum switching overvoltage (SOV) from light load and three phases to ground fault are quite high. The efficiency of line terminal 444 kV surge arresters to controlled SOV along the 500 kV lines is clearly demonstrated.