Effects of system stray capacitances on overcurrent and directional traveling wave protections applied to lines near inverter-based resources

This paper analyzes the effects of transformer and busbar stray capacitances on existing traveling wave (TW)-based overcurrent and directional protection elements (called TW50 and TW32, respectively), when applied to lines that interconnect inverter-based resources (IBRs). IBR-interconnecting transmission lines are usually terminated by transformers, which are seen as open circuits when high frequency components are analyzed. Thus, stray capacitances on the IBR-interconnecting line terminals dictate the shape of measured TWs, consisting in an important aspect for TW-based functions. PSCAD simulations are carried out to investigate the TW50 and TW32 protections, allowing to evaluate in the impacts of distortions and attenuations that take place on the measured wavefronts at both IBR and grid sides. The obtained results show that the system stray capacitances levels have an important effect on the performance of both TW50 and TW32 elements.