Mohamed Nayel

Weightless Swarm Algorithm (WSA) for Dynamic Optimization Problems

In this work the well-known Particle Swarm Optimization (PSO) algorithm is applied to some Dynamic Optimization Problems (DOPs). The PSO algorithm is improved by simplification instead of introducing additional strategies into the algorithm as done by many other researchers in the aim of improving an algorithm. Several parameters (w, V max , V min and c 2) are being excluded from the conventional PSO. This algorithm is called Weightless Swarm Algorithm (WSA) as the prominent parameter, inertia weight w does not exist in this proposed algorithm. Interestingly, WSA still works effectively via swapping strategy found from countless trials and errors. We then incorporate the proven clustering technique from literature into the framework of the algorithm to solve the six dynamic problems in literature. From the series of tabulated results, we proved that WSA is competitive as compared to PSO. As only one parameter exists in WSA, it is feasible to carry out parameter sensitivity to find the optimal acceleration coefficient, c 1 for each problem set.

Study of Soil Resistivity Measurements in Vertical Two-Layer Soil Model

This paper studies and estimates soil resistivity parameters of two-layer vertical soil as a one of the practical soil models. Wenner method is used to measure the apparent soil resistivity. To achieve this study, the image method is proposed to consider the presence of vertical layer soil and four electrodes of the Wenner method. A general apparent resistivity expression is proposed to find the relation between the apparent resistivity and the four electrodes of Winner method locations and soil parameters. The proposed equation with the aid of Gauss-Newton method is used to estimate the soil parameters.

Surface Potential and Resistance of Grounding Grid Systems in Homogeneous Soil

Abstract This article presents laboratory scale models developed to study the performance of grounding systems in uniform soil. Two parallel grids are investigated and correlated with a same mass grid having the same conductor material and extending over the same area at a depth equal to that of the upper grid. The experimental results demonstrate how the potential profiles and ground resistance are influenced by the grounding grid design such as number of meshes, grid depth and spacing between parallel grids. The effectiveness of the two parallel grids is compared with that of the upper grid only. The measured surface potential and ground resistance agreed satisfactorily with the present calculated values

Study of Step and Touch Voltages in Resistive/Capacitive Ground due to Lightning Stroke

This paper aims to calculate step and touch voltages around transmission line tower foot due to lightning strike to the transmission line tower top and injecting the lightning current into resistive/capacitive ground. The transmission tower foot is modeled as hemisphere electrode impeded in the ground with specific conductivity and permittivity. The step and touch voltages are calculated for different towers lengths and different ground parameters

A study on a mutual grounding impedance and its transient characteristic

Self and mutual impedances of grounding electrodes are experimentally investigated for various grounding arrangements and electrode shapes. A transient induced voltage to an electrode is observed to be similar to transient voltages of the electrode and the inducing one when a step-like current is applied individually. Correspondingly, the frequency characteristic of the mutual impedance evaluated by numerical Fourier transform from the measured voltage and current is similar to that of the self impedance. An equivalent model circuit of the grounding impedance is derived from the frequency characteristic, and an EMTP simulation using the model circuit agrees reasonably well with the measured result.

Analysis of Lightning-attractive Areas Around High-voltage Direct Current Transmission Line

Abstract This article studies attractive areas around high-voltage direct current transmission lines due to downward lightning leader presence. The lightning-attractive areas are drawn for power conductors and shielding wires separately to distinguish the shielding failure area. An electromagnetic model is constructed to draw the attractive areas of the high-voltage direct current transmission lines. The transmission line conductors and the downward lightning leader are modeled by using the charge simulation method. Different cases of surrounding conditions, such as lightning slope, ground slope, and wind, are studied for the same downward lightning current. The attractive areas are affected by considering the high-voltage direct current transmission line voltage. As the downward lightning leader charge is negative, the attractive area around the high-voltage direct current transmission line power conductors increases around positive pole subconductors and decreases around negative pole subconductors. The high-voltage direct current transmission line shielding the failure area of the studied cases is increased or decreased due to the surrounding conditions.

A study of zero reference effects on electromagnetic transientient measurements of a grounding electrode

This paper presents the effect of zero reference used in measurements of a grounding electrode transient characteristics. Experimental measurements of many cases of Zero reference have been carried out. Different lengths (20 m, 40 m and 60 m) of the zero reference wire in same and right angel directions to the lead wire direction are examined to obtain their effects on transient voltages of the grounding electrode. Zero reference wire is replaced by a cable with different sheath ends grounding in same and right angel directions. Open end and grounded end of zero reference for different cases are tested and studied. The results show that as the length of zero reference wire increases the measured results accuracy increases. Replace zero reference wire by the cable of grounded sheath at both terminals results to the most accurate measurements.

Investigation of lightning rod striking distance

This paper studies those parameters affecting the lightning stroke to Lightning rod. The downward lightning leader is modeled by using discrete line charges to consider the exponential distribution of charges through the downward lightning leader. The voltage condition used by Rizk is used and modified to investigate the inception of the upward lightning leader and to consider different air conditions (relative air density and air humidity). The influences of lightning parameters and lightning rod height on the lateral striking distance are studied. The results shows that, lightning leader parameters, lightning rod voltage, lightning rod height and ground slope have a series effects on the lateral striking distance.

Investigation of Lightning Rod Shielding Angle

This paper studies those parameters affecting the shielding angle of the lightning rod (Franklin Rod) above very tall buildings. It is recommended that the shielding angle of the lightning rod is about 45o ~ 60o. The downward lightning leader is modeled by using discrete line charge to consider the exponential distribution of charges through the downward leader. The voltage condition used by Rizk is used to investigate the inception of the upward lightning leader. Different air conditions (relative air density and air humidity) are considered for more practical simulation. The influences of lightning parameters and lightning rod height on the shielding angle are studied. The results shows that, lightning leader parameters, lightning rod height and ground slope have a series effects on the shielding angle of the lightning rod. Based on the results, recommendations are supposed to decrease the lightning stroke to the lightning rod.

Analysis of Long Electrode Transient Parameters

This paper aims to analysis of the transient characteristics of Long electrode. Field measurements of wave propagation on an underground naked conductor had carried out. Base on the analysis results of wave propagation in the ground the electrode parameters have been detected. Each part of electrode parameters has been calculated. The analysis of electrode parameters shows dependence and nonlinearity with grounding resistivity, frequency and electrode length.