المستودع الرقمي لـقسم الهندسة الكهربائية والالكترونية

تقدم هذه الأطروحة برنامج حاسوبي تفاعلي لتصميم خطوط النقل الكهربائي ثلاثية الأطوار باستخدام MATLAB. يمكن استخدام هذا البرنامج كوسيلة تعليمية داخل وخارج الفصل الدراسي لشرح أساسيات و ضواهر خطوط النقل الكهربائي.تتناول اغلب الكتب المرجعية المتاحة حاليا لمحتويات خطوط النقل التصميم الكهربائي فقط ولهذا السبب فان اغلب طلاب هندسة القوى الكهربائية يتخرجون من الجامعة وبدون دراية كافية عن الجزء المتعلق بالتصميم الميكانيكي والمتمثل في حسابات ارتخاء الخط والشد على الأبراج وزيادة وزن الموصلات نتيجة لتجمع الثلوج أو زيادة سرعة الرياح وتغير كل من ذلك مع درجات حرارة الجو. كما أن هذا البرنامج مزود ببعض البرامج الإضافية الأخرى والمتمثلة في حسابات قيم سعات ومتحاثات خطوط النقل أخدا في الاعتبار السلك الأرضي. كما أن هذا البرنامج يمكن استخدامه لمعرفة المعاوقات والسعات التسلسلية ( الصفرية والموجبة).وقد تم تزويد هدا البرنامج بقاعدة بيانات تحتوى على مواصفات شاملة للعديد من الموصلات المستخدمة في خطوط النقل الكهربائي.كما أن هذا البرنامج يمكن استخدامه لحسابات شدة المجال الكهربائي حول الموصلات وبالقرب من الأرض.

Abstract

This thesis presents an interactive computer program for three phase overhead transmission line design using MATALB. This program can be used as a self learning tool to understand the course material offered in class and to enhance students understanding to the three phase transmission line subject. This first course is normally given as a core course to all electrical engineering students. Most of the existing text books in power system analysis nowadays cover the Electrical line design only and describe the line performance very efficiently with very few power text books which treat the mechanical line design part. Therefore electrical engineering students with power engineering major are often graduated from school without having sufficient background concerning the mechanical line design features such as; line sag, the mechanical tension at the tower and the conductor sag due to temperature variations or line loading, conductor thermal limit ….etc. The program is also equipped with an additional feature to compute the line sequence impedances and the line sequence capacitances. Other line features are also provided in this package such as ; thermal limit line calculation, line voltage stability phenomena and the electrical field calculation due to transmission line. Therefore using this program the students will then be able to compute the line sequence parameters for both the single circuit as well as the double circuit tower configuration, with and without ground wire. The package has been also provided with a built in data base library to most of the available power line conductors. Therefore power engineering students will then be able to understand the transmission line course contents in more depth and to use the other supporting program modules as a self learning tool for line design and line modeling performance.
.سالم مسعود الكردي (2010)

Abstract

Ad-hoc networking is a concept in computer communications, which means that users wanting to communicate with each other form a temporary network, without any form of centralized administration. Each node participating in the network acts both as host and a router and must therefore be willing to forward packets for other nodes.In a multi-hop wireless packet network, a packet traverses more than one wireless link in traveling from its source to its destination. Such wireless networks have received considerable attention recently in the context of ad hoc networks. Ad-Hoc networks are self-organizing multi-hop wireless networks where not all links along the path of a packet can be activated simultaneously. Hence the performance of a higher level mechanism, such as congestion window or Transport Layer protocol (TCP) will depend crucially on how the links are scheduled for transmission. In multiple access networks, such as the IEEE802.11 wireless LAN, the scheduling of transmissions is done by the medium access control (MAC) protocol. This transmission scheduling is completely unaware of the needs of the TCP congestion window protocol. This thesis is concerned with the poor interaction between the TCP adaptive window protocol, the IEEE 802.11 MAC protocol, and the IEEE 802.11 Ad-Hoc routing protocol. Our thesis follow on the work done by the researchers K. Nahm and C. Kuo in the paper entitled “TCP over 802.11 Multihop networks issues and Performance Enhancement” [1]. Our contributions are two-fold. First we have repeated and confirmed the simulation results reported by K.Nahm and C.Kuo using NS-2 network simulator. Second we have introduced a simple modification in the 802.11 DSR routing protocol which reduces the unnecessary VI reroutings triggered by MAC packet collisions and enforces the TCP to enter the fast retransmit / fast recovery phase to quickly recover the packet loses. This modification has been simulated using NS-2 network simulator and from the results we have found that it provides a substantial improvement in TCP performance in the situations that we have considered in the simulation models
يحي الشارف المبروك (2009)

Abstract

Electric insulators are one of the main parts of over head Transmission lines, they must meet two requirements, first is the electric insulation for the conductors, and the second is to provide mechanical support for the over head lines. Insulators are subjected to various electric stresses of different origin such as operating voltages and an electric stroke waves due to Lightning storms. Therefore the insulators must perform well under all weather and environment conditions. In addition some times degradation occurs in the insulators performance due to accumulation of different types of pollutions on its surfaces. This project deals with two samples of silicone rubber insulators Have been exposed to the natural pollution for 6 years in continuously energized line working in Libyan transmission network. The test line is connecting between Khomes power station to Khomes switching substation it is 8.5 km long, the site is considered to be the most polluted site in Libya .Several tests have been done on this type of insulators to the effect of Libyan Environment on these insulators to decide if this insulator is suitable for working in the Libyan electrical grid.
عبدالمولى بشير على اوحيده (2010)

Abstract

In order to ensure the promise of anytime-anywhere communication to the customers, Mobile operators must be able to support a large number of users over a large coverage area. So Coverage and Capacity are important issues in the planning process for Third Generation (3G) mobile networks. The planning process aims to allow the maximum number of users sending and receiving adequate signal strength in a cell. In Code division multiple access (CDMA), the Coverage and capacity are not independent of each other as in GSM, it is interference-limited system, meaning that if the traffic increases, the serving cell radius decreases, hence the term cell breathing occurs. This work studies the capacity and coverage of a macrocell CDMA network. The cell breathing effect is studied and a new criteria to link Capacity and Coverage is developed, it is named by Capacity-Coverage Product; CCP. Different designations of CCP formula are given. The influencing of various system parameters on this CCP are studied. Knowing this CCP, the capacity and coverage become straight to estimate. The user distribution is very important issue. Most of previous studies treat user distribution as uniform. This thesis considers the case of non uniform user distributions where a more realistic distribution is chosen. A new interference distribution factor is initiated. The impact of this factor on the capacity and coverage is studied. Existing of Hotspot regions of traffic will cause coverage shrinkage. Installation of hotspot microcells BS inside existing macrocell BS is one possible solution to such situations. In this work a microcell is introduced within the macrocell and a new system parameters are obtained such that the coverage and performance are maintained while the capacity is increased.
محمد عبدالرزاق العالم (2007)

Abstract

In practical environment most of physical systems that are existed, have nonlinear behavior. In most cases the accuracy of these systems, and their responses aren’t acceptable. Therefore to improve the performance of these systems, a modern control methodology must be applied. In the case of nonlinear systems most problems can be divided into two basic types of nonlinear control problems; nonlinear regulation and nonlinear tracking problems. Due to existing of high nonlinearities parts in theses nonlinear systems the use of classical linearization methods don’t provide an acceptable level of accuracy and therefore these problems have gained a great attention in recent years; and there are numbers of methods can be found to solve these nonlinear problems, such as trail and error, feedback linearization, Robust control, Adaptive control, Gain-scheduling and…etc. In This thesis the feedback linearization is choose as a control methodology to solve these problems; The central idea of the feedback linearization approach is to algebraically transform a nonlinear system dynamics into a (fully or partly) linear one, so that linear control techniques can be applied. This differs entirely from conventional linearization (i.e., Jacobian linearization [4]) in that feedback linearization is achieved by exact state transformations and feedback, rather than by linear approximations of the dynamics.
فرج على عبدالسلام بشير (2008)

Abstract

In this thesis, we present a method for the design of multidimensional digital filters. This method is based on the use of genetic algorithm (GA). GA algorithm is proposed to optimize the coefficients of magnitude frequency response of digital filter design. GA algorithm is used to minimize a cost function representing the difference between the frequency response magnitudes of an ideal and obtained digital filters. Two types of filters namely, Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) are implemented.The digital FIR filter exhibits a wide transition bands and ripples in the pass band which are considered as disadvantages in digital image processing. Therefore, the only way to obtain a steep transition FIR is to use high order which translates to high cost. An alternative way to avoid high cost filters is to use IIR digital filters. Such digital filters can provide steeper transition bands with lower order than equivalent FIR digital filters. Although FIR digital filters have the disadvantages of high cost in term of hardware realizations, they have the advantage of stability and linear phase. Since IIR digital filters have infinite impulse response, they are prone to unstability. Linear phase which is easy to obtain in FIR digital filters is hard to come by IIR digital filters. The low cost and fast filtering make the IIR digital filters attractive. The proposed GA is utilizing for the design of stable IIR filter with near linear phase constraints. Experimental results are presented for 1-D and 2-D digital IIR filter. From the magnitude-frequency response, the convergence of the proposed approach will be able to obtain global minima in a faster time.
ميسون محمد الزرقاني (2010)

Abstract

In wireless communication systems the data rate, capacity, coverage, and spectral efficiency; can be enhanced with multi-carrier transmission and multi-antenna, then the overall wireless communication system performance is greatly enhanced by combining OFDM and MIMO schemes, MIMO helps in increasing the throughput where as OFDM spreading out the frequency selective fading channel over many symbols. In this thesis evaluating performance of the system depends on both link and system levels, where the measure of performance is represented in the throughput, cell radius and the effective signal to interference plus noise ratio (SINR). It also depends on the employed capacity criterion and it takes into account the impact of adaptive modulation and coding. the worked scenarios start from a link level extending to a system level in 3GPP LTE. To achieve the above a number of tasks followed by observations are carried out. They start by analysis of the equations and a Matlab program is written to calculate the cell edge throughput, cell coverage and DL capacity. After the programs implementation, the multi antenna transmission effect is noted on the arrival throughput when taking into account the modulation technique. When increasing the order of the antenna and the throughput is also increased, but it must be traded off with the probability of error; Coverage has also improved by decreasing the order of the modulation technique. For the system level with different traffic, the overall throughput of the system and the capacity of the network are determined by the number of resource blocks (RBs). These RBs depend on the bit rate of the service and bit rate for each RB. The adopted scenarios in this thesis start from link to system, where the features are represented in a flexible base station and user configurations, channel modeling with path loss, user mobility, also at different transmitter and receiver (MIMO). The approaches are useful in single user and multi-user MIMO, then all of the above can be standardized by metrics: capacity, throughput, spectral efficiency, user QoS etc. Finally thesis conclusion and some future work as an extension of this work are presented.
احمد محمد التانزفتى (2013)

Abstract

The conflict that took place in Libya in 2011, up to the present moment, has greatly affected the electrical power network and resulted in the rise of the voltage instability problem. This was due to loss of the some major transmission lines and certain generation units. Owing to the fact that the southern region of the Libyan network has no generation units, voltage drop phenomena has become a common problem as a result of the long transmission distance, which is approximately 750km. A proposed solution in order to solve this problem is via the utilization of small mobile generation units at the network weak points. This thesis revolves around discussing the voltage instability problem within the Libyan Network and how it can be enhanced when small and mobile generation units are connected to the network weak points. It will also establish and identify where the most weakened buses and regions are so that the mobile units should be connected for the attainment of optimized solution. Moreover, this solution was proposed as it can solve not only the voltage instability problem, but it will also solve the inadequacy in generation issue by circulating additional power within the network. Hence, reduce the load shedding phenomena. Furthermore, the thesis also includes future recommendations to improve and enhance the Libyan network by the addition of new 220kV and 400kV transmission lines that will enable the network to cope with the load growth in the future
ربيع محمد عمر (2014)