Application of a protection scheme to mitigate the impact of load rejection in a 500 kV transmission system

This paper investigates application of a protection scheme to mitigate the impact of temporary overvoltages caused by load rejection in the Manitoba Hydro 500 kV transmission system. The sectionalization of Dorsey - Forbes 500 kV line at Riel affects temporary overvoltages seen during a load rejection. The results of electromagnetic transient simulations show that overvoltages due to a load rejection on 230 kV side could severely stress surge arresters and other equipment at both Dorsey and Riel stations, and could also lead to ferroresonance. The simulation results formed the basis for functional specification of the new protection scheme at Riel station.