Line Electrical Parameters Research Articles

Parameters-free non-iterative two-terminal measurements synchronization algorithm

This paper presents an innovative phasor-based algorithm to synchronize measurements taken from two-terminal transmission lines. The line capacitive effect is taken into account and only the analysis of steady-state voltage and current phasors is required, eliminating the need for settings based on line electrical parameters. To evaluate the proposed solution, several tests are performed using data from 138 kV, 230 kV, and 500 kV/60 Hz lines that belong to the Brazilian interconnected power grid. Real operating conditions of the Brazilian system are considered to assess the algorithm performance under different scenarios, including light, moderate and heavy line loading cases, and various power factors and line lengths. The obtained results show that the proposed solution is reliable, straightforward, accurate, being useful for practical two-terminal phasor-based applications when traditional common time reference sources are not available.

Time Domain Electromagnetic Transient Analysis of Aerial Nonuniform Transmission Lines Excited by an Incident Electromagnetic Field

In this paper a model for Nonuniform Transmission Lines for electromagnetic transient analysis that incorporates frequency dependency of electrical parameters, variation of line electrical parameters with respect to distance, and distributed excitations due to incident electromagnetic fields is presented. The model is developed using the Method of Characteristics in the actual physical domain instead of the Modal Domain; this simplifies the mathematical development and the final equations. Moreover, the equations of the resultant model are valid either for two-conductor lines or for multiconductor lines without any change; this can be an advantage when the computer programming language considers a scalar as a 1x1 matrix. The proposed numerical model is developed under the hypothesis that the dielectric surrounding the conductors is homogenous. It is shown that in this case the characteristic curves of a Nonuniform Transmission Line become straight lines. Finally, the model is validated by comparison with results obtained using the Numerical Laplace Transform method.

Closed-Form Solution for Traveling Wave-Based Fault Location on Non-Homogeneous Lines

In this paper, a closed-form solution for traveling wave (TW)-based fault location on non-homogeneous lines (NHLs) with multiple sections is proposed. It is able to accurately estimate the fault location on NHLs, taking into account the different propagation velocities, irrespective of the number of sections, including the effects of line electrical parameters uncertainties. The algorithm can be applied to non-homogeneous transmission networks composed by overhead transmission lines (OHLs), underground cable lines (UCLs), submarine cable lines (SCLs), or by any other line section with considerably different electrical characteristics. A wide variety of fault scenarios were simulated in a 380 kV/50 Hz NHL consisting of multiple OHL, UCL, and SCL sections. In each simulation, the proposed algorithm performance was compared against those obtained from an existing two-terminal TW-based fault location approach. The obtained results reveal that the proposed closed-form TW-based solution is generalist and reliable, being useful for fault location applications on NHLs.

Frequency-dependent models of overhead power lines for steady-state harmonic analysis: Model derivation, evaluation and practical applications

This paper presents a novel frequency-dependent model for electric power lines to be used in harmonic studies. First, the differential equations representing the distributed nature of the line electrical parameters are considered; frequency dependency due to the effect of ground return and the skin effect is then incorporated. These derived equations represent what in this paper is defined as the analytical model, used as benchmark for model comparison. The vector fitting technique is used here to approximate the analytical model and derive a frequency-dependent frequency domain model. A passive circuit realization of the proposed model in a PI structure is presented and can be directly implemented in steady-state analysis tools such as harmonic power flow solvers. This paper then presents the evaluation and verification of the proposed model for multiple test cases. The test cases of unbalanced three-phase lines for overhead and underground conductors are considered. Moreover, to evaluate system-level impacts of the proposed model, the IEEE 13 node test feeder is considered. Through the evaluation of the test results, it is shown that the proposed model is more accurate than currently-used steady state models such as the simple (nominal) PI or the constant PI (with constant parameters calculated at fundamental frequency) models in terms of steady state harmonic voltages and currents at the line terminals. Test results obtained using the proposed model are within comparable accuracy to the ones obtained using the electromagnetic and transient (EMT) model, without having to run computationally expensive time domain simulations.

Animations of electromagnetic transients in power transmission lines by means of the two-dimensional numerical Laplace transform

This paper presents the use of animations of the wave propagation phenomena on power transmission lines as a valuable tool for research and educational purposes. These animations are generated from data obtained by transient analysis in the frequency domain applying the two dimensional numerical Laplace transform. Since the line electrical parameters are defined in the frequency domain, the frequency dependence of such parameters is directly taken into account. These animations allow an insightful illustration of how travelling waves propagate along transmission lines during an electromagnetic transient, making them a useful tool to determine transient overvoltages that occur at internal points along power transmission lines. In the educational field, using these animations in electrical engineering courses can help students to have a better understanding of the traveling wave concept and how it differs from the circuit theory. In addition, it allows detailed comparison of the wave propagation along lines under different conditions, such as type of excitation, type of load, introduction of losses, etc.

Accurate Computation of Transient Profiles Along Multiconductor Transmission Systems by Means of the Numerical Laplace Transform

In this paper, transient internal profiles along multiconductor transmission lines are obtained from a model described in the q- s domain (spatial frequency-temporal frequency). In such domain, the telegrapher equations of the line are defined in a direct algebraic form. Applying boundary conditions, these equations can be easily solved for V (q,s) and I (q,s). Then, the inverse numerical Laplace transform is applied successively (twice) to obtain v (z,t) and i (z,t), that is, the voltage and current profiles along the line. Besides, since the line's electrical parameters are defined in the frequency domain, the frequency dependence of such parameters is included in a straightforward manner. Test cases corresponding to an overhead line, a transformer winding, an underground power cable, and a transmission network are evaluated in order to demonstrate the accuracy and versatility of the proposed method. The results are compared with those obtained with Alternative Transients Program/Electromagnetic Transients Program and PSCAD/EMTDC at specific points along the transmission systems under analysis, given that the space discretization is cumbersome and prone to error accumulation in these time-domain simulation programs.

Fitting the frequency-dependent parameters in the Bergeron line model

A new transmission line modeling – TLM is proposed based on the well-established Bergeron method. The conventional Bergeron model is characterized by the line representation through concentrated longitudinal and transversal parameters, i.e., the line electrical parameters are represented by means of electric circuit elements R, L, G and C. The novel approach of this research is the inclusion of the frequency effect in the longitudinal parameters in the Bergeron line representation. This new feature enables to extend the application of the Bergeron method for simulations of transients composed of a wide range of frequencies.

Predictive dynamic model of the negative lightning discharge based on similarity with long laboratory sparks ߝ Part 1: physical process and modeling

This paper presents a predictive dynamic model enabling a description of the whole negative lightning discharge. The proposed model takes into account the different phases of the propagation (i.e., the initiation of the first corona, the pilot leader, the negative and space leaders and their junction up to the final jump). This model is based on an LCR line electrical network parameters derived with electromagnetic field, physical laws and gas discharge theories (L, C and R, being respectively the inductance, the capacitance and the resistance). Criteria for initiation, development, stand-off and some atmospheric conditions are also introduced. From this model the main macroscopic parameters of the negative lightning can be computed.

The waveform degradation in VLSI interconnections

A simple model for the transfer characteristic of an infinitely long resistive-capacitive (RC) distributed transmission line is presented. This model is used to obtain the time-domain response for a ramp function driving the RC distributed line. This model can be used for studying the effect of the line's electrical parameters on its transient response and can be easily implemented for computer-aided analysis of VLSI circuits. >