Improving the accuracy of system security assessment in highly stressed transmission grids

Presently, the active and reactive power limits of the power generation model implemented in the TSO´s system security assessment tools do not respond to the grid´s actual voltage. This model is only accurate as long as the voltage remains within narrow limits. This paper proposes to improve the accuracy of the system security assessment by implementing precise voltage dependent reactive power limits of power generation units into a power flow analysis. The proposed model is compared to the presently used model. Its advantages in stressed system conditions are demonstrated by performing a system security assessment in a small test grid.