Impact of Inverter-Based Resources on Transmission Line Distance Protection

With increasing penetration of inverter-based resources, distance protection can fail to extract reliable fault charactertics from grid-following (GFL) and grid-forming (GFM) inverters, leading to misoperations. In this presentation, the fault behaviour of GFL and GFM inverters is analysed, and their impact on the apparent impedance seen by distance relays is examined. First, parameter sensitivity is investigated through parameter sweeping to identify key control and fault parameters that shape the relay-calculated impedance. Then, relay misoperations are classified into transient and steady-state categories; the former are driven by non-sinusoidal fault dynamics, while the latter are caused by biased apparent impedance after settling. Further, a nonlinear control strategy is proposed to reshape the inverter fault response and reduce transient distance protection misoperations. Finally, an analytical steady-state impedance model is developed to quantify the impact of control and fault parameters and to guide distance relay setting in inverter-dominated systems.