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.

This letter describes an important improvement to a previously described method to compute the transient voltage and current profiles along transmission lines using the numerical Laplace transform. Previously, the algorithm was applied successively (twice) to obtain such profiles. In this letter, a fast and efficient alternative is described, by means of defining a two-dimensional inversion of the numerical Laplace transform based on MATLAB function ifft2. Cases concerning a single-phase line and a three-phase line are included to demonstrate the effectiveness of the proposed enhancement. The central-processing unit time from the proposed algorithm is substantially lower than the one required by the previous method without loss of accuracy (approximately 5 times lower for the cases under study). In addition, since the proposed algorithm requires less computer resources, it is more suitable for larger sampling rates.

In this study, a transmission line model described in the q–s domain (spatial frequency–temporal frequency) is applied to obtain transient voltage and current profiles along field‐excited multiconductor lines (also known as illuminated lines). The incident field excitation is incorporated into the model by means of Taylor's formulation, in which such field is included by means of series voltage and shunt current sources distributed along the line. For the case of lines excited by an indirect lightning stroke, the corresponding field is computed according to the formulae proposed by Master and Uman. The inverse numerical Laplace transform is applied successively (twice) to obtain the results in the z–t domain, corresponding to the voltage and current profiles along the illuminated line. An initial validation of the model consists of two examples, in which simple analytical expressions are introduced for the voltage and current sources (separately) along the line in order to provide comparisons with alternative transients programme/electromagnetic transients programme. Then, three test cases corresponding to lightning strokes at different locations near the line are considered. Power system computer‐aided design/electromagnetic transient design and control is used in this section for validation purposes.

In this work, transient internal overvoltages along multiconductor transmission lines are obtained by means of a model described in the q-s domain. In such domain, the Telegrapher Equations of the line are defined in a simple algebraic form. These equations are solved for V(q, s) and I(q, s). Then, the inverse numerical Laplace transform (NLT) is applied successively to obtain v(z, t) and i(z, t) (the voltage and current profiles along the line). Additionally, the multiconductor line model presented is applied to obtain the transient profiles along each turn of a transformer winding. Test cases are evaluated for both multiconductor line and transformer winding.

Electromagnetic transients are responsible for overvoltages and overcurrents that can have a negative impact on the insulating elements of the electrical transmission system. In order to reduce the damage caused by these phenomena, it is essential to accurately simulate the effect of transients along transmission lines. Nonuniformities of transmission line parameters can affect the magnitude of voltage transients, thus it is important to include such nonuniformities correctly. In this paper, a frequency domain method to compute transient voltage and current profiles along nonuniform multiconductor transmission lines is described, including the effect of time-varying and nonlinear elements. The model described here utilizes the cascade connection of chain matrices in order to take into consideration the nonuniformities along the line. This technique incorporates the change of parameters along the line by subdividing the transmission line into several line segments, where each one can have different electrical parameters. The proposed method can include the effect of time-dependent elements by means of the principle of superposition. The numerical Laplace transform is applied to the frequency-domain solution in order to transform it to the corresponding time-domain response. The results obtained with the proposed method were validated by means of comparisons with results computed with ATP (Alternative Transients Program) simulations, presenting a high level of agreement.

This paper describes a method in the frequency domain to compute voltage and currents at interior points of a non-uniform multiconductor transmission line during electromagnetic transients, including the effect of time-dependent elements (such as switches). The non-uniformities of the line are incorporated into the model by means of the cascaded connection of chain matrices. This technique subdivides the transmission line into several smaller line segments (chain matrices), each one with different electrical parameters, allowing to simulate the change in parameters along the line. The inclusion of time-dependent elements is done by means of the principle of superposition, where each switching maneuver (or any change in the network topology) is treated as an initial condition problem. The numerical Laplace transform is used to transform the frequency domain solutions to the time domain, where they can be easily analyzed. In order to validate the accuracy of the method presented in this paper, two test cases are presented and the results are compared with those computed with ATP simulations.