Pablo Gomez

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 measurement-based 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 single-phase 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.

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.

This paper discusses the access to pornographic content by adolescents in virtual environments and its repercussions for their affective-sexual lives. It explores contemporary configurations of sexuality, such as affective and sexual initiation, sexual experimentation and consolidation of the...

This paper introduces a wideband parameter estimation approach for untransposed three-phase overhead transmission lines. The proposed method involves an accurate reconstruction of the 2-port nodal model of the line over a wide frequency band from terminal measurements obtained for a set of tests. The minimum norm least-squares method is applied for the solution of the overdetermined mathematical system resulting from these tests. The reconstructed model is further solved for the series impedance and shunt admittance matrices without the need for modal decupling techniques. Terminal voltage and current measurements used as inputs are simulated using software ATP for several tests that consider different tower configurations. The estimated parameters are compared with those computed analytically, with very close results when compared with analytical parameter calculation considering full frequency dependence.

Accurate calculation of transient overvoltages and dielectric stresses from fast-front excitations is required to obtain an optimal dielectric design of power components subjected to these conditions, which are commonly due to switching and lightning, as well as utilization of power-electronic devices. Toroidal transformers are generally used at the low voltage level. However, recent investigations and developments have explored their use at the medium voltage level. This paper analyzes the model-based improvement of the insulation design of medium voltage toroidal transformers. Lumped and distributed parameter models are used and compared to predict the transient response and dielectric stress along the transformer winding. The parameters of the toroidal transformer are computed using the finite element method considering a three-dimensional geometry. Different strategies for insulation design are proposed by means of optimal insulation thickness and electrostatic shield to reduce transient overvoltage and dielectric stress. The results show that the proposed optimal insulation design based on particle swarm optimization with electrostatic shield can substantially reduce the dielectric stress and dielectric distances. Comparison between simulations and experimental results demonstrates that the frequency domain modeling approach results in accurate calculation of transient overvoltages produced by fast front excitation and can be used effectively for insulation design.

Methods based on both time ( t )-domain and frequency ( f )-domain have been used for electromagnetic transient (EMT) analysis using both circuit-theory and field-theory approaches. Methods based on circuit theory are fast and convenient but may become inapplicable to many engineering problems due to simplifications such as the transverse electromagnetic assumptions. Moreover, t -domain-based techniques rely on approximate methods to account for frequency dependence, which is an essential characteristic of electric conductors, equipment and soil environment. In this paper, f -domain solutions obtained from the method of moments (MoM) discretization of the electric field integral equation (EFIE) are converted to t- domain using the numerical Laplace transform (NLT) by means of post-processing. This circumvents the need to formulate the EFIE and MoM based on the complex frequency which would be required for their application to conventional NLT. Hence, existing MoM implementations can be used to perform a full-wave 3-D EMT analysis for a wide range of power system applications. Examples include energizations of 3-D power system networks with fast and non-vanishing excitations such as step functions, as well as modeling non-linear elements using the piecewise linear approximation. Results from experimental measurements, finite-difference t -domain method, and EMT-type software confirm the validity of the proposed method for power system transients in the range of microseconds down to nanoseconds.

Akihiro Ametani was born in Nagasaki, Japan, on 14 February 1944. He received the B.Sc. and M.Sc. degrees from Doshisha University, Kyoto, Japan, in 1966 and 1968, respectively, and the Ph.D. degree from the University of Manchester, England, in 1973. He was with the Bonneville Power Administration (BPA), Portland, Oregon, from 1976 to 1981 and 1991 to 1992, where he contributed to the development of the Electromagnetic Transient Program (EMTP). He was a professor at Doshisha University from 1974 to 2014.