Papers by Ibrahim Metwally
Electric Power Systems Research, 2007
This paper investigates the capability of some samples of transient surge suppressors (TVSSs), us... more This paper investigates the capability of some samples of transient surge suppressors (TVSSs), used in electrical submersible pump (ESP) installations, to withstand non-destructive standard impulse tests. Tests were performed on different ratings of the TVSS and with a voltage rating up to 2.5 kV, to fulfill the basic impulse withstand level (BIL) of the ESP motors. On the other hand, used and unused TVSS were also tested by the standard high-amplitude impulse currents to examine the degradation effect. Compared to the (old) ...
Simulation Modelling Practice and Theory, 2008
This paper presents a 2D finite-element analysis of the induced eddy currents on motor and oil we... more This paper presents a 2D finite-element analysis of the induced eddy currents on motor and oil well casings of an electrical submersible pump (ESP) oil lifting system. Simulation results revealed that the increase in motor-casing conductivity and/or permeability decreases the eddy-current density on the well casing, contrary to that on the motor casing. Further increase in one or both of these parameters leads to a decrease in both current densities as a result of the skin effect phenomenon. However, the increase of well casing conductivity ...
Electric Power Systems Research, 2007
This paper investigates the capability of some samples of electrical submersible pump (ESP) motor... more This paper investigates the capability of some samples of electrical submersible pump (ESP) motors to withstand standard basic "lightning" impulse level (BIL) and to get the destructive voltage for all phases. Tests were performed on samples from different ESP vendors and with a voltage rating between 1 kV and 2 kV, to fulfill the lightning impulse standard test requirements. All the tested ESP motors showed a decrease in the terminal impedance between one line and the motor casing with the frequency, i.e. low-pass filter effect for fast transient overvoltages. In addition, all ESP motors passed the standard lightning impulse withstand tests with no significant change in the terminal impedance. Used ESP motor failed at 37 pu of the BIL, while all the new ESP motors failed at much lower level up to 22 pu. This trend is attributed to the better oil infiltration in the used motor during runtime than in the new motor with zero runtime. .om (I.A. Metwally).
IEEE Transactions on Electromagnetic Compatibility, 2008
This paper presents a numerical analysis of the reduction of lightning-induced magnetic fields an... more This paper presents a numerical analysis of the reduction of lightning-induced magnetic fields and voltages inside double-layer grid-like spatial shields typically used in reinforced concrete buildings, e.g., nuclear power plants. The calculations are performed with the CONCEPT computer code, which solves Maxwell's equations using the method of moments in the frequency domain. The computer code is extended with the well-known transmission line model (TL-model) in order to simulate direct lightning strikes. The structure under study comprises a cubic cage of 2 m side length having single-or double-layer grid-like spatial shields with square meshes of 0.25 m width. Three lightning-channel attachment points are considered at the cage roof, namely, the center, the midedge, and the corner. The simulated lightning currents are the positive, the negative first, and the negative subsequent strokes at lightning protection level I (LPL I) according to the international standard series IEC 62305. The computed quantities comprise the currents through some selected wires of the grid-like spatial shields, the magnetic fields, the magnetic-field derivatives, and the induced voltage across a typical installation loop inside the shield. The results of the single-layer shield are compared to those of the double-layer one to evaluate the additional reduction of the latter shield.
IEEE Transactions on Electromagnetic Compatibility, 2004
This paper presents measurements of the voltages, the magnetic fields and the magnetic-field deri... more This paper presents measurements of the voltages, the magnetic fields and the magnetic-field derivatives inside a structure simulating reinforced concrete buildings. The test structure comprises a cubic cage of 2-m side length with singleor double-layer reinforced grids. The injected lightning currents simulate the positive, the negative first and the negative subsequent return strokes with amplitudes of 77, 16, and 4.8 kA, respectively. Three distinct points of the lightning stroke impact to the structure roof are considered, namely, the center, the mid-edge and the corner. In the case of a single-layer cage, the results reveal that slow-rising magnetic-field components are generated inside the structure for various lightning currents. This effect becomes dominant for the case of the double-layer cage. For all the simulated currents, striking to the structure corner induces the lowest voltage across it, but gives the highest values for both the resultant magnetic fields and the magnetic-field derivatives. For all striking points, the magnetic fields have the highest values for positive strokes, while the negative subsequent strokes give the highest amplitude of the resultant magnetic-field derivatives and roof-to-floor voltages. Compared to the case of a single-layer cage for the negative subsequent strokes, the use of a double-layer cage shows a considerable mitigation of the voltage across the structure, and a moderate mitigation of both the resultant magnetic fields and the magnetic-field derivatives.
IEEE Transactions on Electromagnetic Compatibility, 2006
This paper presents a numerical electromagnetic analysis of magnetic fields and loop voltages ins... more This paper presents a numerical electromagnetic analysis of magnetic fields and loop voltages inside reduced-and full-scale lightning protection systems (LPSs) "structures" resulting from direct lightning strikes. The method of moments is employed to model the whole structure in three dimensions except the lightning channel. The lightning channel is simulated by the wellknown transmission-line model (TL model), where the influence of the lightning-channel generated electric and magnetic fields are taken into account. Three distinct LPSs were modeled, namely, reduced-scale model with return conductors (RSRC), reducedscale model with lightning channel (RSLC), and full-scale model with lightning channel (FS).
European Transactions on Electrical Power, 2005
This paper presents a theoretical simulation for a pipeline running in parallel to AC overhead po... more This paper presents a theoretical simulation for a pipeline running in parallel to AC overhead power lines using the ‘CONCEPT II’ package. This package is based on the method of moment combined with a transmission-line model. A 1 km long, 132 kV, three-phase, double-circuit transmission line, and a 2 km long, 40 cm diameter, 1 m high above-ground pipeline are modelled. Extra shielding wires (ESW) under the phase conductors are investigated. Produced voltages in the pipeline are computed under steady-state power frequency (50 Hz) as well as under direct and indirect lightning strikes to the power line. Different current waveforms are simulated to cover the whole range of those of the anticipated lightning. Under lightning strikes, the voltages across line insulators are computed, too. The results reveal that the ESW give many advantages; namely, (1) reducing the power-frequency electric and magnetic fields at the ground level to meet the regularity limits, (2) improving the shielding effectiveness during lightning strikes by reducing the insulator voltages, (3) mitigating the induced voltages in any metallic structure near the power lines, e.g., pipelines, and (4) using them as optical ground wires for telecommunication purposes, where the probability of lightning strikes to such ESW is much lower than that for the normally used grounding wire(s) at the tower top. Copyright © 2005 John Wiley & Sons, Ltd.
IEEE Transactions on Electromagnetic Compatibility, 2003
This paper addresses a numerical electromagnetic analysis of the influence of installing passive ... more This paper addresses a numerical electromagnetic analysis of the influence of installing passive shield wires "extra ground wires" (EGW) underneath the bottom phase conductor on the lightning shielding performance of 765-kV, 3-phase, double-circuit transmission lines. The method of moment (MOM) is employed to model the whole structure in three dimensions except the lightning channel. The lightning channel is simulated by the well-known transmission-line model (TLM), where the influence of the lightning-channel-generated electric and magnetic fields (EMF) are taken into account. The lightning shielding performance with and without EGW is introduced and discussed, without ac energization and due to three distinct lightning strokes, namely, the negative first, the negative subsequent and the positive strokes. The produced voltages and currents in the phase conductors and ground wires as well as the voltage across the insulators are computed, with and without the EGW, due to different lightning current waveforms, locations and inclination of the lightning channel, and return-stroke velocities. The introduction of such EGW results in a significant improvement of the shielding effectiveness by reducing the lightning-produced voltages and currents in the phase conductors as well as the voltage across the insulators. Accordingly, a much lower transient overvoltages can be expected with less inadvertent outages of the lines, where the probabilities of flashover and back-flashover decrease, and the reliability enhances. Index Terms-Electric and magnetic fields (EMF), extra ground wires (EGWs), insulator voltage, lightning shielding, numerical electromagnetic transient.
IEEE Transactions on Power Delivery, 2007
... 2207 Enhancement of the SPD Residual Voltage at Apparatus Terminals in Low-Voltage Power Syst... more ... 2207 Enhancement of the SPD Residual Voltage at Apparatus Terminals in Low-Voltage Power Systems Ibrahim A. Metwally, Senior Member, IEEE, and Fridolin H. Heidler ... Frequency (in hertz). L Line (live) wire. Inductance at the apparatus terminal, H. N Neutral wire. ...
IEEE Transactions on Electromagnetic Compatibility, 2007
This paper presents a numerical electromagnetic analysis of loop-termination voltages inside an o... more This paper presents a numerical electromagnetic analysis of loop-termination voltages inside an outer lightning protection system (LPS) resulting from direct lightning strikes. The method of moments is combined with the transmission line model, and employed to model the whole structure in three dimensions and the lightning channel, respectively. Three distinct standard LPS classes and a nonstandard LPS are modeled, namely, LPS1, LPS2, and LPS4, and LPS0, respectively. All cases are simulated using the negative subsequent stroke current at lightning protection level II according to IEC 62305-1. Three distinct current waveforms are selected in order to simulate the variety of different current rises. Three single-phase parallel vertical loops are simulated inside the struck LPS. The results reveal that reducing the LPS mesh width improves its shielding performance, where this may be a basic method to damp the lightning-induced voltages with little dependency on the strike location, and without any appreciable effect of the LPS material. The variation of the lightning-current front shows that the loop-termination voltages are altered within a factor of about 2. Existence and interconnection of extra protective earthing, e.g., via information technology cables, and the value and type of the loop-termination impedance also have significant influence on such voltages.
European Transactions on Electrical Power, 2009
IEC 62305-4 gives the rules for the selection and the installation of surge protective devices (S... more IEC 62305-4 gives the rules for the selection and the installation of surge protective devices (SPDs), where the maximum enhancement factor is considered to be equal to 2 in the worst case of open-circuit condition. The objective of the present paper is to check this relation for equipment connected to low-voltage (LV) power system. The LV power system is considered as TN-S system with different routings in three- and six-storey buildings. The terminals of apparatus are substituted by a variety of different loads, namely, resistances, inductances, and capacitances. All Maxwell's equations are solved by the method of moments (MoM) and the voltage is calculated at the apparatus terminals. The SPD itself is simulated by a voltage source at the ground floor. The results reveal that the voltage at the apparatus terminals may overshoot the SPD protection level by a factor of 3 irrespective of the number of floors and loops. Copyright © 2008 John Wiley & Sons, Ltd.
IEEE Transactions on Power Delivery, 2009
This paper presents a numerical electromagnetic analysis of loop-termination voltages inside an o... more This paper presents a numerical electromagnetic analysis of loop-termination voltages inside an outer lightning protection system (LPS) resulting from direct and indirect lightning strikes. The method of moments is combined with the transmission-line model and employed to model the whole structure in three dimensions and the lightning channel, respectively. Three distinct types of class II LPS are modeled with one- and three single-phase parallel vertical loops of the TN-S system inside the LPS. All cases are simulated by using the negative subsequent stroke current with linear-rising front at lightning-protection level II. The connected equipment at the loop terminals is considered in the offstate to simulate the worst condition. The results reveal that for the three-loop configurations, the middle-loop termination voltages of all floors are always higher than those of the outer loops and the frequency of oscillations of the middle loop is roughly twice that of the outer ones. In addition, the midedge strike case gives higher loop-termination voltages for all floors than those of the corner strike case. For the slender LPS, the effect of the strike location dominates in the case of high surge impedance of the feeder only.
IEEE Potentials, 2011
This article presents a survey on failures, monitoring, and new trends of power transformers. The... more This article presents a survey on failures, monitoring, and new trends of power transformers. There are three main types of power transformers, namely, oil immersed, gas-insulated, and dry-type transformers with or without cast coil insulation system. Operating stresses of power transformers have increased due to the load growth and the increased bulk power transactions, where recent and imminent alternating current (AC) systems are rated 1,100 kV and 1,200 kV, respectively. Failures of windings, onnload tap changers (OLTC), and bushings are the main defective components as they represent about 84% of the failure statistics. Online and offline diagnostic monitoring of power transformers can be used to detect faults at an early stage, prevent degeneration into catastrophic phenomena, and monitor the aging process of the insulating systems. Many of the well-known preventive maintenance techniques are discussed. New trends of power transformers have recently taken many steps forward in different dimensions, e.g., Powerformer, Dryformer and Windformer utilizing high-voltage (HV) cross-linked polyethylene (XLPE) cables, gas-insulated transformers (GIT), converter transformers rated ±800 kV, and high-temperature super conducting (HTS) transformers. The latter type represents a key technology for future power systems engineering as they offer many advantages over the others.
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Papers by Ibrahim Metwally