A Study on the Determination of Time Domain Based on Governor-Free Response Qualification in the Korean Power System

in low-inertia power systems. In the Korean power system, Governor-Free (GF) performance is conventionally assessed using a fixed evaluation framework with a 10 s grace period and a 50 s assessment window after a frequency event. However, this approach does not adequately reflect generator-specific dynamic characteristics and may include the effects of Automatic Generation Control (AGC) in the GF assessment result.<br/>This paper proposes a generator-specific GF-only evaluation window based on the dynamic characteristics of the GGOV1 governor model. By considering actuator delay, fuel system dynamics, and turbine response, the effective GF response interval was derived as 2.3–7 s for the target generator. Case studies using actual system event data show that the conventional fixed window can distort the actual GF contribution of individual generators, whereas the proposed method more clearly captures the initial primary frequency response while reducing AGC influence. The proposed approach can improve the fairness and physical consistency of GF performance assessment in low-inertia power systems.