26 publications
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The Time and Frequency Response of Shielded Transformer WindingsBy Mohamed Mostafa Saied
Abstract: A distributed-parameter model is presented for the transient and frequency analysis of power transformers’ windings in the presence of electrostatic shielding, a technique occasionally applied for improving their initial voltage distribution. The s-domain solution takes into account the windings’ circuit parameters with special emphasis on the additional distributed capacitances between the windings’ conductors and the conducting shield which is connected to the windings’ line terminal. The closeness of the resulting …
Published in Journal of Power Electronics and Power Systems · Vol. 4, Issue 2, 2014 · pp. 33–47 Read article →
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The Transient Response and Frequency Characteristics of Power Transformers having Non-uniform Winding InsulationBy Mohamed Mostafa Saied
Abstract: This paper presents a Laplace-domain distributed-parameter technique for analyzing the transient and frequency response of power transformers having non-uniform winding insulation. Stronger winding insulation near the windings source side terminals is usually applied in order to mitigate the concentration of the transient voltage stresses close to these locations. This will result in a location-dependent inter-turn capacitance distribution. The suggested procedure for analyzing such windings is based on the cascade connection …
Published in Journal of Power Electronics and Power Systems · Vol. 4, Issue 1, 2014 · pp. 37–52 Read article →
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Effect of the Background Harmonics and the Network’s Impedance Characteristics on the Operation of Shunt CapacitorsBy Mohamed Mostafa Saied
Abstract: This paper deals with the possible adverse harmonic conditions associated with the connection of shunt compensating capacitors to certain network buses. It takes into account both the daily profile of the voltage background harmonics and the frequency dependence of the network's input impedance at these buses. These two factors will be incorporated in four established standards and recommendations used for assessing the severity of the harmonic pollution in the network. …
Published in Journal of Power Electronics and Power Systems · Vol. 3, Issue 1, 2013 · pp. 22–32 Read article →
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The Electromagnetic Transients in Mixed Power Networks with Partial UndergroundingBy Mohamed Mostafa Saied
Abstract: This paper deals with the electromagnetic transients in partially undergrounded mixed high voltage power networks. These networks can include several cable sections replacing parts of the overhead transmission lines. The analysis yields the transient voltage and current distributions along the normal and the partially undergrounded lines. Moreover, the results can indicate eventually existing localized voltage and current concentrations within the network. The study suggests an exact direct analytical distributed parameter …
Published in Journal of Power Electronics and Power Systems · Vol. 7, Issue 2, 2017 · pp. 1–13 Read article →
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A Contribution to the Frequency and Transient Analysis of High Voltage BushingsBy Mohamed Mostafa Saied
Abstract: The paper suggests a method for determining the frequency characteristics and transient response of capacitively graded high voltage bushings. It is based on an s-domain circuit model that describes the grading conducting foils and the insulating layers. In most cases, they are of different axial lengths. A system of simultaneous differential and algebraic equations is derived taking these differences into account. Its closed-form solution, subject to the boundary conditions, can …
Published in Journal of Power Electronics and Power Systems · Vol. 9, Issue 1, 2019 · pp. 15–26 Read article →
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The Frequency and Transient Analyses of a High Voltage Bushing/Transformer CascadeBy Mohamed Mostafa Saied
Abstract: This paper investigates the frequency characteristics and electromagnetic transients of a typical system composed of a high voltage bushing and a power transformer connected in cascade. Detailed distributed-parameter Laplace-domain models are adopted for the digital simulations. These parameters include, among others, the transformer winding’s series inductance, its capacitance to ground and the inter-turn capacitances. Moreover, the number, the geometrical data of the capacitively-graded bushing’s conducting foils and the dielectric insulating …
Published in Journal of Power Electronics and Power Systems · Vol. 9, Issue 1, 2019 · pp. 42–53 Read article →