Methodologies for Defining Harmonic Specifications in Transmission Systems at Future Points of Connection of Energy Resources

The integration of renewables into transmission networks introduces significant challenges for maintaining power quality, particularly in greenfield substations where harmonic observability is absent. TSOs must define harmonic specifications for new PoCs, including permissible distortion limits and Thevenin equivalent parameters, early in the planning process. This paper presents and compares two approaches for forecasting harmonic background levels at transmission-level PoCs. The first, currently applied by the Polish TSO, uses a deterministic method based on a steady-state harmonic model and nodal admittance relationships, producing fixed distortion values for selected scenarios and contingencies. The second, under development, introduces a probabilistic framework that leverages…