Yazar "Mamis, MS" seçeneğine göre listele

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    Computation of corona effects in transmission lines using state-space techniques
    (Pergamon-Elsevier Science Ltd, 2003) Herdem, S; Mamis, MS
    In this paper, state-space method is applied to compute transients in power transmission lines by considering corona effects. Transmission line is modeled by lumped parameter identical sections to simulate the distribution nature of the line and nonlinear corona branches are combined with these sections'. The whole system is composed of RLC elements, sources and switches. The response of the system is calculated using state-space method which has been developed for the analysis of nonlinear power electronic circuits with periodically operated switches. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    Computation of electromagnetic transients on transmission lines with nonlinear components
    (Iee-Inst Elec Eng, 2003) Mamis, MS
    A state-space technique (SST) for the computation of electromagnetic transients on transmission lines with nonlinear components is presented. State equations for the nonlinear system are derived and these equations are converted to a set of algebraic equations using the trapezoidal rule of integration. A state-space formulation and numerical solution steps are described. To show the validity of the method proposed, two illustrative examples are given. In the first example, lightning surges on a single-phase with a corona are analysed. The effect of the presence of a surge arrester is investigated in the second example. The results obtained using the state-space technique are compared with those obtained using the electromagnetic transients program (EMTP) and with experimental results available in the literature. The proposed method is accurate, numerically stable and suitable for the computation of electromagnetic transients on transmission lines with several nonlinearities.
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    Lightning surge analysis using nonuniform, single-phase line model
    (Iee-Inst Elec Eng, 2001) Mamis, MS; Köksal, M
    In the analysis of lightning surges, transmission towers are usually simulated by nonuniform lines, but overhead lines are assumed uniform. If the effect of line sags is considered, the variation of the overhead line parameters with respect to space should also be treated as nonuniform. Tower surge response is computed using nonuniform, single-phase line models for both transmission tower and ground wire. Using boundary conditions for these lines, total response of the system in s-domain is obtained. A fast inverse Laplace transform is used for the frequency-to-time domain conversion. The effect of line losses is included.
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    Remark on the lumped parameter modeling of transmission lines
    (Hemisphere Publ Corp, 2000) Mamis, MS; Köksal, M
    Transmission fines are distributed parameter systems. Instead of distributed parameter models, lumped parameter models are also used for steady-state and transient analysis of transmission lines. Lumped parameter modeling for transmission lines is obviously an approximation. This paper aims to investigate the theoretical error in the lumped parameter modeling of transmission fines for steady-state and transient analysis. To determine the error, steady-state and transient responses of the transmission line are calculated by using both distributed and lumped parameter modeling. The effect of number of sections used for lumped parameter modeling is investigated. Obtained results can be used for the determination of the number of sections.
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    s-domain analysis of lightning surges in three-phase systems using nonuniform single-phase line model
    (Springer, 2005) Kaygusuz, A; Mamis, MS; Akin, E
    Surge response of the transmission tower in a three-phase transmission system is computed using s-domain nonuniform single-phase transmission line modelling. First, tower top voltage is obtained considering the tower and the ground wire by excluding the effect of the phase conductors, and then the induced voltages on the phase conductors as a result of the current flowing through the ground wire are computed using the magnetic coupling between the ground wire and the phase conductors. The first step of the analysis is the formulation of the system response in the s-domain, and the second step is the frequency to time domain conversion, which is carried out using fast inverse Laplace transform (FILT). The voltages on the phase conductors and the voltages across the tower insulators are computed, and some of the results obtained using s-domain analysis are compared with those obtaining using electromagnetic transients program (EMTP). The effect of frequency dependence of the line parameters is investigated.
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    Solution of eigenproblems for state-space transient analysis of transmission lines
    (Elsevier Science Sa, 2000) Mamis, MS; Köksal, M
    When lumped parameter models are used for transmission lines, which are originally distributed parameter systems, the set of first order ordinary differential equations (ODEs) of the lumped parameter equivalent circuit can be arranged so that the coefficient matrix is in the tridiagonal form. In the circuit theory, these equations are called as state-equations and in the analytical solution of these equations computation of matrix exponential takes an important part. One way to calculate the matrix exponentials and other matrix functions is to use similarity transformations, which requires eigenanalysis of the coefficient matrix. In this study, state-space technique for computation of transmission line transients is given. Calculation of matrix exponentials for coefficient matrices having tridiagonal structures and eigenproblems associated with it are investigated. QR algorithm, LR algorithm and characteristic equation method for eigenvalue calculation are treated for this type of matrices in both accuracy and computer run time point of views. Several cases are considered and effect of matrix dimension and ill-conditions are also examined. (C) 2000 Elsevier Science S.A. All rights reserved.
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    State-space modeling and analysis of fault arcs
    (Elsevier Science Sa, 2005) Mamis, MS; Meral, ME
    This paper presents a state-space technique for the transient analysis of power systems arcing faults, using the time-dependent dynamic resistance model. The state equations describing the system behavior are derived and these equations are solved by the use of numerical integration. Based on the solution technique, a computer program in the MATLAB environment is developed. The computer program is capable of directly formulating the state equations for a transmission line with a fault arc and it produces data for the arc voltage, current and resistance. (C) 2005 Elsevier B.V. All rights reserved.
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    Transient analysis of nonuniform lossy transmission lines with frequency dependent parameters
    (Elsevier Science Sa, 1999) Mamis, MS; Koksal, M
    An s-domain method for transient analysis of lossy, frequency dependent nonuniform transmission lines having parameters arbitrary varying with space is presented. Nonuniform line is divided into adequate number of sections which are then assumed uniform. The terminal equation for the nonuniform line is calculated by using the terminal equations of the uniform line sections. By using the boundary conditions, total response in s-domain is obtained. Fast inverse Laplace transform is used for frequency to time domain conversion. In one of the examples, the step response of an open ended nonuniform line is obtained and the results are compared with those obtained by lattice-diagram technique. The effect of number of sections is investigated and it is concluded that for sufficiently large number of sections, the results approach to the analytical solutions which can be obtained only for very special nonuniform lines. In the second example, the method is applied for the calculation of transmission tower lightning surge response. (C) 1999 Elsevier Science S.A. All rights reserved.
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    Transient voltage and current distributions on transmission lines
    (Iee-Inst Elec Eng, 2002) Mamis, MS; Nacaroglu, A
    Transient conditions such as switching operations and faults cause the generation of travelling waves on power transmission lines. Spatial current and voltage distributions on the transmission line are computed in the time domain using the state-space technique. The state-space representations of the transmission lines for short- and open-circuit faults and for various types of terminations are given. The results obtained by the method are compared with the solutions obtained in the frequency domain.