A Proposal to Mitigate Over-Voltage Issue within Period of 2017-2020 and A Vision to 2025 in Central Vietnam

The transmission grid systems are the spines of the electric systems, so ensuring conditions of security, quality, reliability and voltage stability is a pressing and necessary requirement for power transmission networks. In recent years, the North-South 500kV transmission line has tended mostly to transmit high capacity from North and Central to South Vietnam in order to meet the demand of South Vietnam and exploit hydro-power plants, optimally and efficiently. At many times, when the demand of the national power system goes down, the phenomenon of over voltage usually occurs at the nodes in Centre section of North-South 500kV line; especially during the new year holiday, the voltage exceeds the allowable limit. In this paper, the author researched and calculated the voltage magnitudes at 500kV nodes in Central Vietnam using the PSS/E software to simulate the electrical system, then the author also proposed equipping the additional 128MVar of shunt reactor at Doc-Soi, Pleiku-2, Dak-Nong and Di-Linh nodes as well as equipping the circuit breakers for electrical reactors in operation. The goals are to ensure that the voltage profiles of the 500kV, 220kV nodes are always within the allowable range between now and 2025, to add voltage regulating tool to the special modes during the new year holiday, to improve the quality of voltage, to reduce the operations, to meet the progress of putting the non-local-operator stations into operation, to reduce losses and to improve the stability of the power system.