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Thesis
Odero AN. HYBRID METHOD OF MOMENTS (MOM)/FINITE ELEMENT METHOD (FEM) FORMULATION FOR PROBLEMS OF TRANSMISSION THROUGH NON-BACKED AND WAVEGUIDE-BACKED CAVITIES OF ARBITRARY SHAPE IN THICK CONDUCTING SCREENS . Benard KD, ed. Juja: JKUAT; 2007. Abstract

Concerted efforts have been made towards developing more elaborate techniques for solving aperture coupling problems. The majority of these techniques, however, deal with apertures of regular shapes and, in each case, only a particular problem has been solved. It is only with the development of numerical methods, such as the Method of Moments and Finite Element Method that it has become possible to treat irregularly shaped apertures.

However, each of the above methods has its own advantages and disadvantages when applied to different problems. The Method of Moments is an integral equation method which handles unbounded problems very effectively but becomes computationally intensive when material and structural inhomogeneities exist. In contrast, the true power of the finite element method is revealed in three-dimensional volume formulations in the presence of material and structural inhomogeneities. The method requires less computer time and storage because of its sparse and banded matrix. The matrix filling time is also negligible when simple basis functions are used. For complex basis functions, the matrix filling time can be significant.

A suitably implemented hybrid method takes advantage of the strengths of the individual methods constituting it while avoiding their weaknesses. This research therefore, as one of its objectives, has developed a hybrid method that combines the method of moments and the finite element method (MOM/FEM). The analysis is based upon the "generalized network formulation" for aperture problems. The cavity region is subdivided into tetrahedral elements resulting in triangular elements on the surfaces of the apertures.

In this work, a hybrid MOM/FEM solution procedure for the general problem of apertures of arbitrary shapes in thick conducting screens and waveguide walls has been developed and used in the analysis of a variety of representative problems. Appropriate modeling of the aperture/cavity has been carried out using tetrahedral and triangular elements. Suitably defined sets of basis functions have been integrated into the formulation which is capable of accurately evaluating fields of apertures of arbitrary shape. The problem has been formulated by invoking the equivalence principles and utilizing boundary conditions on the apertures/cavity to derive equations which have then been transformed into matrices that are then solved numerically by simulation on a digital computer. The finite element method, employing reliable vector formulation, has been employed in the computation of the interior admittance matrix. Here, edge elements or tetrahedra in which the degrees of freedom are assigned to the edges rather than the nodes are utilized. This resulted in the avoidance of nonphysical or spurious modes, a difficulty that arises when node-based elements are used. Based on the preceding formulation, extensive computation of various parameters for apertures/cavities of various shapes has been done and results presented. The two main classes of problems treated in this study comprise apertures of arbitrary shape in thick conducting screens and waveguide-backed apertures.

Odero AN. A Study of the Electrical Insulation Characteristics of Woods Locally locally available in Kenya. Nelson I, ed. Nairobi: University of Nairobi; 1993. Abstract

For my thesis I did a problem formulation and then wrote a computer program to help speedily analyze various insulator profiles for use at high voltages. The program when fed the profile would output the potential and electric field patterns around the high voltage insulator, in addition to predicting it's flashover voltage. Validation of the model was obtained through practical measurement in a high voltage laboratory. Profiles that would insulate very high voltages were arrived at this way in a relatively short time.

Report
Odero AN. Tariff Development for Kenya. Nairobi: University of Nairobi; 1990. Abstract

For my final year undergraduate project, I developed tariffs for various classes of consumers of KPLC electrical energy using the marginal costing technique. This is a forward looking accounting method that takes into account expansion plans and how the power system is to be operated as demand increases. Expansion plans, which would entail capacity/inestment costs, operation and maintenance costs forecasts, administration and general costs forecasts, total kilowatt costs, and peak and off-peak energy and fuel costs, spring from load forecasts. This resulted in an efficient resource allocation scheme in which power prices to consumers are related to the resource costs of changes in consumption, i.e, the addition of a new consumer or an increase in consumption of an existing consumer will impose additional costs on the enterprise, while a reduction in consumption will save costs. These alteration in costs are the ones that need to be reflected in tariffs. The change in the cost to a consumer of altering his electrical behavior will then mirror the change in the cost to the enterprise. This not only results in fair and equitable tariffs, but also ones that inherently have incentives to better consumption patterns by consumers.

This marginal costing technique contrasts sharply with the accounting (traditional) one which is based on examining the records of past expenditure thus becoming backward looking. Such prorated accounting costs are quite different from the costs relevant to resource allocation and creates the illusion that resources which can be used or saved are as cheap or as expensive as in the past, i.e, resources are as abundant or as restricted as in the past. On the one hand this may cause over investment and waste; on the other, it may lead to under investment and unnecessary scarcity. In addition, if the past holds a number of poor projects, the sunk costs of mistakes, if reflected in prices, will overstate the costs to the consumer of extra consumption, which is not efficient. Tariff schedules and the various simplifications thereof are derived by spreading total accounting costs among consumers. This generates tariffs which relate to average rather than to marginal costs.

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Journal Article
C KJ, O AN. "Effects of Distributed Generation penetration on system power losses and voltage profiles." International Journal of Scientific and Research Publications. 2013;3(12):1-8. Abstractijsrp-p24585.pdf

In present times, the use of DG systems in large amounts in different power distribution systems has become very popular and is growing on with fast speed. Although it is considered that DG reduces losses and improves system voltage profile, this paper shows that this is not always true. The paper presents a GA-IPSO based approach which utilizes combined sensitivity factor analogy to optimally locate and size a multi-type DG in IEEE 57-bus test system with the aim of reducing power losses and improving the voltage profile. The multi-type DG can operate as; type 1 DG (DG generating real power only), type 2 DG (DG generating both real and active power) and type 3 DG (DG generating real power and absorbing reactive power). It further shows that though the system losses are reduced and the voltage profile improved with the location of the first DG, as the number of DGs increases this is not the case. It reaches a point where any further increase in number of DGs in the network results to an increase in power losses and a distortion in voltage profile.

Abungu NO, Konditi DB, Otieno AV. "Analysis of Waveguide-backed Apertures of Arbitrary Shape in a Thick Conducting Screen." World Scientific and Engineering Academy and Society (WSEAS). 2008. AbstractWebsite

Power utility companies are required to supply customers with power within specified voltage limits. Voltage rise in networks with distributed generators therefore poses a challenge. This paper presents a coordinated network controller whose objective is to maintain an optimal voltage profile across the power network. The operations of distributed generators, on-load tap-changing transformers and reactive power sources are controlled. The controller is modelled as an optimisation problem which is solved using Particle Swarm Optimisation. The IEEE 30-bus test network is then used to verify the effectiveness of the controller. The results obtained show that this controller can greatly improve the voltage profile of a power network by varying the parameters of existing generation and voltage control equipment.

Abungu NO, Konditi DB, Otieno AV. "Analysis of Waveguide-backed Inhomogeneously-filled Apertures of Arbitrary Shape in a Thick Conducting Screen." World Scientific and Engineering Academy and Society (WSEAS). 2007. AbstractWebsite

Power utility companies are required to supply customers with power within specified voltage limits. Voltage rise in networks with distributed generators therefore poses a challenge. This paper presents a coordinated network controller whose objective is to maintain an optimal voltage profile across the power network. The operations of distributed generators, on-load tap-changing transformers and reactive power sources are controlled. The controller is modelled as an optimisation problem which is solved using Particle Swarm Optimisation. The IEEE 30-bus test network is then used to verify the effectiveness of the controller. The results obtained show that this controller can greatly improve the voltage profile of a power network by varying the parameters of existing generation and voltage control equipment.

Abungu NO, Konditi DB, Otieno AV. "Analysis of Electromagnetic Transmission through dielectric filled Apertures of Arbitrary Shape in a Thick Conducting Screen." World Scientific and Engineering Academy and Society (WSEAS). 2005. AbstractWebsite

The paper deals with an extension of the previous work appearing in a past issue of this transaction by the authors on hybrid FEM/MOM technique for analyzing transmission properties of arbitrarily shaped apertures on a thick conducting screen. In the present work, the effect of placing different dielectric material slabs in the conducting screen cavity on the electromagnetic transmission parameters is first analyzed and, then, the effect of interchanging the positions of these dielectric slabs relative to the incident field. Validation results for rectangular and cross-shaped slots are presented. Close agreement between our data and published data is observed.  Further data has been generated for rectangular, circular, diamond-shaped and cross-shaped apertures.

Conference Proceedings
Obadiah N'ang'a, George N, W K, Abungu NO. An experimental Prototype for Low Head Small Hydro Power Generation Using Hydram.. Jomo Kenyatta University of Agriculture and Technology(JKUAT): JKUAT; 2012. Abstractjkuat_conference_paper.pdf

The global rise in energy demand has resulted to the over exploitation of both renewable and non renewable energy sources. Most feasible hydroelectric power (HEP) plants sites have been exploited and the current focus is on harnessing energy from small HEP plants which have low head and flow velocity rendering them unsuitable for HEP generation. Previous research work focused on improving the turbine shape and efficiency; designing better water intake, improving the generator and development of turbines suitable for low heads. The main aim of this research was to optimize the power generated by low head small hydro plants through the use of hydraulic ram pump (hydram) to boost the water pressure before it impinges on the turbine. In the current work, a smallHEP prototype system was designed fabricated and test runs conducted. The prototype comprised of; a low head water reservoir, a hydraulic ram pump which was used to increase the head of the water emanating from a low head source, a high head reservoir mounted at a the most optimal height based on the hydram flow rate and pressure considerations and a double cup pelton wheel turbine suitably designed to extract power from the water jet. A drive pipe was used to connect thehydram pump to the low head reservoir while the delivery pipe connected the pump to the high head reservoir. Water from the high head reservoir was used to turn the pelton turbine which was coupled to a generator. The flow rate in the drive pipe and the delivery pipe as well as the pressurein the hydram were optimized by adjusting the waste valve stroke length. It was observed that the hydram was able to pump water to a higher head which then increased the power produced by the turbine.

Conference Paper
Lucy OP, Odero AN. "Solution to Economic Load Dispatch Problem using Particle Swarm Optimization.". In: KSEEE. Mombasa, Kenya; 2014. Abstractpso18sept2014.pdf

This paper proposes to determine the feasible optimal solution of the economic load dispatch power systems problem using Particle Swarm Optimization (PSO) considering various generator constraints. The objective of the proposed method is to determine the steady-state operating point which minimizes the fuel cost, while maintaining an acceptable system performance in terms of limits on generator power, line flow,
prohibited operating zone and non linear cost function. Three diff erent inertia weights; a constant inertia weight CIW, a timevarying inertia weight TVIW, and global-local best inertia weight GLbestIW, are considered with the (PSO) algorithm to analyze the impact of inertia weight on the performance of PSO algorithm. The PSO algorithm is simulated for each of the method individually. It is observed that the PSO algorithm with
the proposed inertia weight (GLbestIW) yields better results, both in terms of optimal solution and faster convergence.

Abungu NO, Konditi DB, Otieno AV. "Analysis of Waveguide-backed Apertures of Arbitrary Shape in a Thick Conducting Screen.". In: 1st JKUAT Scientific, Technological and Industrialization Conference. The JKUAT Scientific, Technological and Industrialization Conference 2006; 2006. Abstract

Power utility companies are required to supply customers with power within specified voltage limits. Voltage rise in networks with distributed generators therefore poses a challenge. This paper presents a coordinated network controller whose objective is to maintain an optimal voltage profile across the power network. The operations of distributed generators, on-load tap-changing transformers and reactive power sources are controlled. The controller is modelled as an optimisation problem which is solved using Particle Swarm Optimisation. The IEEE 30-bus test network is then used to verify the effectiveness of the controller. The results obtained show that this controller can greatly improve the voltage profile of a power network by varying the parameters of existing generation and voltage control equipment.

Abungu NO, Konditi DB, Otieno AV. "A Hybrid Finite Element/Moment Method for Solving Electromagnetic Radiation Problem of Arbitrarily-Shaped Apertures in a Thick Conducting Screen.". In: The KSEEE (Kenya Society of Electrical and Electronics Engineers ) Conference. The Kenya Society of Electrical and Electronics Engineers (KSEEE); 2004. Abstract

In this paper a hybrid numerical technique is presented, suitable for analyzing transmission properties of an arbitrarily shaped slot in a thick conducting plane. The slot is  excited by an electromagnetic source of arbitrary orientation. The analysis of the problem is based on the "generalized network formulation" for aperture problems. The problem is solved using the method of moments(MOM) and the finite element method(FEM) in a hybrid format. The finite element method is applicable to inhomogeneously filled slots of arbitrary shape while the method of moments is used for solving the electromagnetic fields in unbounded regions of the slot. The cavity region has been subdivided into tetrahedral elements resulting in triangular elements on the surfaces of the apertures.  Validation results for rectangular slots are presented. Close agreement between our data and published results is observed.  Thereafter, new data has been generated for cross-shaped, H-shaped and circular apertures.

Abungu NO, Konditi DB, Otieno AV. "Hybrid Method Analysis of Electromagnetic Transmission through Apertures of Arbitrary Shape in a Thick Conducting Scree.". In: World Scientific and Engineering Academy and Society (WSEAS). World Scientific and Engineering Academy and Society (WSEAS); 2004. Abstract

In this paper a hybrid numerical technique is presented, suitable for analyzing transmission properties of an arbitrarily shaped slot in a thick conducting plane. The slot is  excited by an electromagnetic source of arbitrary orientation. The analysis of the problem is based on the "generalized network formulation" for aperture problems. The problem is solved using the method of moments(MOM) and the finite element method(FEM) in a hybrid format. The finite element method is applicable to inhomogeneously filled slots of arbitrary shape while the method of moments is used for solving the electromagnetic fields in unbounded regions of the slot. The cavity region has been subdivided into tetrahedral elements resulting in triangular elements on the surfaces of the apertures.  Validation results for rectangular slots are presented. Close agreement between our data and published results is observed.  Thereafter, new data has been generated for cross-shaped, H-shaped and circular apertures.

Ijumba N, Orero SO, Abungu NO. "Computer applications in voltage monitoring and control (case of the Kenya Power and Lighting Company.". In: The International Workshop on Voltage Collapse & Voltage Regulatio. The International Workshop on Voltage Collapse & Voltage Regulation; 1992. Abstract

When an insulator is placed in an electrode gap, its surface charge field distorts the geometric field, leading to a flashover at a voltage value dependent on the degree of the gap field distortion. This paper reports on studies conducted to determine the relationship between flashover voltages and electric filed distribution along solid insulator surfaces. The surface electric field distribution along different insulator profiles was determined using the Finite-Difference method, and the flashover of the actual profile model measured. The obtained results show that each profile had a peak surface electric field and the higher the peak value, the lower the flashover voltage. The correlation curve for peak electric field and flashover voltage was developed using a curve fitting technique based on the Nelder-Mead simplex algorithm.

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