Browsing by Department "Aswan University"

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    Proposed Approach to Investigate the Current and Voltage Distributions of Isolated and Grounded Systems during Earth Fault Conditions
    (IEEE, 2023) Gouda, Osama E.; Dein, Adel Z.El; Tag-Eldin, Elsayed; Lehtonen, Matti; Darwish, Mohamed M.F.; Cairo University; Aswan University; Future University in Egypt; Department of Electrical Engineering and Automation; Benha University
    One important objective of this article is to present a novel approach to study the current density and ground surface potential around the area surrounding earthed and isolated systems in the event of a line-to-earth fault. The present study is done in the case of uniform and two layers of soil. The contact and arc resistances of the line-to-ground faulty conductors are considered. A grounded system is usually implemented with rods and/or grounding grids, the impact of both on step and touch potentials and current density are investigated, discussed, and adapted. The methods of the calculations are based on the electrical concepts, the charge simulation method, and the image method for the grounding system. The results obtained are in agreement with that reported by others, with the benefits of the proposed algorithm for its ease of application, simplicity, and it does not need complex computer programs or a long time in calculations. 3-D dimensions contours of the current density and the electric potential on the earth's surface around the faulty point in case of homogeneous and two layers of soil are presented, whether the network is grounded or isolated. Comparing the results obtained with those reported by the others, differences of 2.2% in the Ground Potential Rise, 2.46% in the current density, and 0.5% in the fault current passes into the isolated system are recorded. These values in the differences are within the acceptable limits.
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    Studying Direct Lightning Stroke Impact on Human Safety near HVTL Towers Considering Two Layer Soils and Ionization Influence
    (IEEE, 2023-01-10) Gouda, Osama E.; El Dein, Adel Z.; Omar, Sara Yassin; Darwish, Mohamed M.F.; Lehtonen, Matti; Cairo University; Aswan University; Department of Electrical Engineering and Automation; Department of Electrical Engineering and Automation
    A lightning strike is considered one of the most risky natural phenomena that can lead to human harmful and the surrounding soil layers. To tackle this issue, this article investigates the influence of direct lightning characteristics in terms of human body safety. Specifically, such investigation is carried out on the effect of resistivities of two-layer soils on human safety when lightning stroke hits the towers of the high voltage transmission lines (HVTLs). The merit of the proposed study is that the soil ionization phenomenon is taken into consideration. Further, the study focuses on the current passing through the human heart, when step and touch (contact) voltages are generated by grounding potential rise, caused by direct lightning strikes transmission tower and the produced potential rise that a person could be exposed. Also, studying the effects of peak current and time of lightning strokes are investigated. Additionally, the paper presents the effect of different reflection factors on human safety.For validation purposes, the ATP program is used in the simulation of the grounding system as well as the human body model. Numerous simulations were accomplished in order to examine the behavior of the current passing through with the human heart. Based on the simulation results, it was concluded that the soil characteristics have superior influences on the contact and step potentials and, accordingly, the survival threshold.
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    Thermal analysis of the influence of harmonics on the current capacity of medium-voltage underground power cables
    (John Wiley & Sons, 2023-10) Gouda, Osama E.; El Dein, Adel Z.; Tag-Eldin, Elsayed; Lehtonen, Matti; Darwish, Mohamed M.F.; Cairo University; Aswan University; Future University in Egypt; Department of Electrical Engineering and Automation; Benha University
    In this article, an algorithm is proposed and used to study the influence of harmonics on the behavior of medium-voltage underground cables in flat formation. The proposed algorithm is a thermal model based on the heat equilibrium of the thermal circuit nodes of the medium-voltage cable system. The impact of harmonics on the temperature rise of the cable elements and the cable capacity is evaluated in this article. Also, the impact of harmonics on the derating factors of cable for different soil types is presented. Finally, the measurement of temperatures of cable cores is carried out experimentally and compared with the calculated results to validate the proposed algorithm. One of the algorithm merits is that several harmonic percentages can be taken into account for each cable phase individually, and the heat exchange between the cable phases and their sheath is also taken into consideration. From the obtained results, it is illustrated that the presence of harmonics has a remarkable influence on the cable core temperature; mainly, harmonics of the third and fifth orders may lead to dry zone formation around the cable. It is also observed that the presence of harmonics has an important influence on the cable current, especially when it is buried in soil that has high thermal resistivity during the summer season (suction tension = ∞). In summer, the cable core temperature reached 152.162°C, 139.053°C, and 133.375°C when lime, sand, and silty sand, respectively, are used as backfill materials, rather than 90°C in the normal operating condition of the 11 kV three-phase single-core cable. It is observed also that with the increase of the soil thermal resistivity, the ratio of (Formula presented.) / (Formula presented.)) reached about 1.2 times at 2.5 K m/W soil thermal resistivity. In addition, it is also observed that the impact of harmonics leads to a percentage reduction in the derating factor of the cable center phase by 11.88%–12.37% depending on the composition of the backfill materials.