Electromagnetic Transient Model Reconstruction of Generalized Power Transmission Lines Based on Time-Synchronized Waveform Measurements

Thanks to the novel technology of waveform measurement units (WMUs), it is now possible to record time-synchronized waveforms (synchro-waveforms) at different power system locations. Leveraging these new opportunities, this paper introduces a method for accurate wideband measurementbased reconstruction of single-and three-phase frequency-dependent transmission line models for electromagnetic transient (EMT) studies. This method also accommodates hybrid (overhead-underground) systems and longitudinal parameter variations (nonuniformities). A 2-port line model is generated across a broad frequency spectrum using WMU terminal recordings and the numerical Laplace transform. For singlephase uniform lines, one transient recording set is sufficient for model reconstruction; this extends to ideally transposed three-phase lines. For single-phase nonuniform and three-phase uniform and nonuniform untransposed lines, a minimum norm least-squares method is applied to solve an overdetermined system from multiple recordings with linearly independent responses. Simulated measurements from ATP (Alternative Transient Program) are used for three test cases: a three-phase balanced uniform line, a single-phase hybrid system, and a three-phase unbalanced nonuniform line. The reconstructed model responses are compared with ATP simulations, confirming the technique's accuracy and robustness. Furthermore, the impact of practical signal conditions on reconstruction accuracy is analyzed in detail, including noise, resolution, and ratio and phase displacement errors from instrument transformers.