Controlling long-term overvoltages in lightly loaded transmission systems

This paper deals with mitigating undesired transmission system long-term overvoltages. The analysis is performed using both power flow analysis (for steady-state) and long-term simulation employing quasi-steady-state approximation. Guidelines and mitigation measures are investigated for planning (such as selecting appropriate shunt reactor locations), as well as operational strategies, such as special transformer load-tap-changer (LTC) controls, and reactive power absorption by wind farms connected through power converters in dedicated distribution feeders. Two case studies are considered, one being a light-load snapshot of the Hellenic Interconnected System, and the other involving a sub-transmission area of the French Transmission Grid.