Cellular networks in Africa have grown exponentially over the past 10 years and their data centres (DCs) on average consume 3 MW of electrical power. They require a reliable electrical power supply and can have a downtime loss of over a million dollars per hour. Power quality, reliability and availability have emerged as key issues for the successful operation of a data centre. Investigations are carried out into emerging technologies and their application in data centre power distribution systems for cellular networks in Africa. Best practices are applied to develop a power distribution system (PDS) with the objective of achieving optimal reliability and availability. Analytical techniques are applied to determine and compare the reliability and availability of various power systems. Minimal cut set simulations identify system weak points and confirm component selection. Components’ inherent characteristics (CIC) and system connectivity topology (SCT) are key factors in the improvement of data centre availability. The analysis practices can be used by engineers and managers as a basis for informed decision making in determining power system reliability and the availability of an existing or a new data centre design. Weak points in the PDS of a data centre causing downtime are identified through analysis, and accurate solutions can be determined to prevent or minimise downtime. System connectivity topology (SCT) techniques were identified that could increase the reliability and availability of data centres for cellular networks in Africa. These techniques include multiple incomers from the utility company, redundancy levels of critical equipment and parallel distribution paths. Two case studies were carried out on data centres for a cellular network, one in Nigeria and one in Cameroon. The reliability and availability of both data centres was improved, with substantial reduction in downtime per year. The outcome of the case studies shows the importance of designing and implementing the power distribution system with sufficient levels of redundancy for critical equipment, and parallel distribution paths. / MSc (Engineering Sciences in Nuclear Engineering), North-West University, Potchefstroom Campus, 2014

The presented thesis investigates the identification of burst locations in water distribution systems (WDS) by analysis of field and simulation experimental data. This required the development of a new hybrid method of burst detection and sizing, and also a burst location identification algorithm. Generally, existing practice relies on a combination of some simple procedure and experience of the involved staff and cannot be easily automated. The practical methods are based on direct manifestation of burst on the surface or on systematically surveying suspected areas e.g. by using listening sticks, such methods are very time consuming. The proposed burst location algorithm is based on comparing data by means of statistical analysis of field data with results of water network simulation. An extended network hydraulic simulator is used to model pressure dependent leakage terms. The presence of a burst changes the flow pattern and also pressure at network nodes which may be used to estimate the burst size and its location. The influence of such random factors as demand flows and background leakage on the process of burst detection is also considered. The field data is from a generalised fixed area and variable area (FAVOR) test where inlet pressure is being stepped up and down and the following variables are measured: inlet flow, inlet pressure (head) and pressure at a number of selected sensitive nodes. The method has three stages and uses two different models, one is inlet flow model (IFM) to represent the total inlet flow and another is the extended hydraulic model to simulate different burst locations. Initially the presence of a potential burst is investigated. If this is confirmed precise values of the demand, background leakage flow and burst flow in IFM are subsequently estimated. They are used to identify the burst site at the third stage of the method. The method can be easily adapted for practical use. It requires data from experiments carried out at night between 1am and 5am and involves placing typically about 20 temporary loggers to collect the measurements during this period. It also requires the availability of a hydraulic model which normally is in the possession of a water company. The program has been implemented in the Matlab package and is easy to use. The current methodology is tuned to identify a single burst but can be generalised to identify locations of multiple bursts.

The goal of this study was to determine the economic feasibility of battery energy storage system (BESS). Three major economic benefits derived from BESS using were studied: 1. Energy Purchase Shifting, 2. Distribution Feeder Deferral, 3. Outage Avoidance. The economic analysis was based on theoretical modeling of the BESS and distribution system. Three simulation models were developed to quantify the effects of different parameters, such as: BESS round-trip efficiency, life span, rated power, rated discharge time, marginal cost of electric energy, 24 h feeder load profile, annual load variation, feeder load growth rate and feeder length. An optimal battery charging/discharging method was presented to determine the differential cost of energy (DCE). The annual maximum DCE was calculated using stochastic probability analysis on seasonal load variation. The net present value was evaluated as the present value difference between two investments: first, the distribution feeder upgrade without BESS deferral, and second, with BESS deferral. Furthermore, the BESS’s contributions under different outage strategies were compared. It was determined that feeder length is the most significant parameter. The economics of the studied system becomes favorable when the feeder length exceeds a critical value.

Orientador: José Roberto Sanches Mantovani / Banca: Fabio Bertequini Leão / Banca: Luis Gustavo Wesz da Silva / Resumo: Neste trabalho propõe-se um algoritmo baseado na meta-heurística busca dispersa para o problema de reconfiguração de redes de distribuição de energia elétrica radiais, considerando como sistema de codificação uma estrutura denominada representação nó profundidade (RNP). O problema é modelado como não linear inteiro misto e considera como objetivo principal minimizar as perdas de potência ativa nos alimentadores do sistema de distribuição. Utiliza-se neste trabalho o modelo de cargas com potência constante, como também o modelo exponencial de cargas. O algoritmo proposto é implementado em linguagem de programação C++ e testado em quatro sistemas conhecidos na literatura, 14, 84, 136 e 202 barras. A partir dos resultados obtidos, verifica-se o bom desempenho do algoritmo, pois é capaz de gerar soluções de boa qualidade atendendo a todas as restrições físicas e operacionais do problema. / Abstract: This work proposes a scatter search algorithm to solve the electric power distribution system reconfiguration problem, considering the encoding system node depth representation. The problem is a mixed-integer nonlinear programming and the objective is to minimize the real power losses in the distribution system. It is used in the work load model with constant power, but also exponential model load. The proposed algorithm is implemented in C + +. The validity of the methodology is verified through four commonly case studies such as 14, 84, 136 and 202 bus system. Results show the effectiveness and good performance of the proposed algorithm, where it obtains the good quality solution satisfying the operational and physics constraints of problem. / Mestre

Distribution system design and planning is facing a major change in paradigm because of deregulation of the power industry and with rapid penetration of distributed generation (DG) sources. Distribution system design and planning are key features for determining the best expansion strategies to provide reliable and economic services to the customer. In classical planning, the load growth is typically met by adding a new substation or upgrading the existing substation capacity along with their feeders. Today, rapid advances in DG technology and their numerous benefits have made them an attractive option to the distribution companies, power system planners and operators, energy policy makers and regulators, as well as developers. This thesis first presents a comprehensive planning framework for the distribution system from the distribution company perspective. It incorporates DG units as an option for local distribution companies (LDCs) and determines the sizing, placement and upgrade plans for feeders and substations. Thereafter, a new heuristic approach to multi-year distribution system planning is proposed which is based on a back-propagation algorithm starting from the terminal year and arriving at the first year. It is based on cost-benefit analysis, which incorporates various energy supply options for LDCs such as DG, substations and feeders and determines the size, placement and upgrade plan. The proposed heuristic approach combines a bi-level procedure in which Level-1 selects the optimal size and location of distribution system component upgrades and Level-2 determines the optimal period of commissioning for the selected upgrades in Level-1. The proposed heuristic is applied to a 32-bus radial distribution system. The first level of the distribution system planning framework is formulated as a mixed integer linear programming (MILP) problem while the second level is a linear programming (LP) model. The results demonstrate that the proposed approach can achieve better performance than a full optimization for the same distribution system.

The biologically-mediated process of nitrification can occur in chloraminated drinking water distribution systems. In this process, ammonia is oxidized to nitrite by ammonia-oxidizing bacteria (AOB) and archaea (AOA). In complete nitrification, nitrite is further converted to nitrate by nitrite-oxidizers; however, bacterial mediation of this step is less critical as a chemical-oxidation pathway also exists. The initial conversion of ammonia to nitrite is also more critical due to its role in the degradation of the disinfectant residual. Nitrification is affected by factors such as the concentrations of ammonia and total chlorine, the pH of the drinking water, and the temperature. The key consequence of distribution system nitrification is an accelerated decay of the disinfectant residual; it can also lead to increases in nitrite and nitrate, and a potential proliferation of heterotrophic bacteria. The goal of this thesis is to enhance understanding of distribution system nitrification; one aspect to this goal is the evaluation of models for nitrification. The approach followed in this study was to collect water samples from two full-scale distribution systems in Southern Ontario. In the first phase, a sampling campaign was conducted at sites in these systems, with water samples being analyzed for parameters considered relevant to nitrification, such as the concentrations of nitrogen species affected by nitrification, the disinfectant residual, and the levels of ammonia-oxidizing microorganisms. In the second phase, batch tests were conducted with water from these same distribution systems. In the course of the field sampling campaign some indications of nitrification were detected, but there were no severe nitrification episodes as indicated by major losses of the disinfectant or prolonged elevations in nitrite levels. On some occasions at some sites there were small rises in nitrite above baseline levels; moderate declines in total chlorine residual were also seen. Nitrifying microorganisms were present in most samples, as detected by both culture-based and molecular methods (PCR). The latter was able to distinguish AOA from AOB; both were detected in the systems included in this study, with AOB gene counts outnumbering those of AOA at most sites. Using Spearman non-parametric correlations, significant correlations were found between some parameters relevant to nitrification. Notably, AOB were found to be positively correlated with heterotrophic plate counts (HPC), reinforcing the latter's role as a useful indicator of microbial regrowth conditions in a distribution system. Also of interest is the negative correlation between total chlorine residual and levels of microorganisms, reminding drinking water professionals of the value of maintaining a stable disinfectant residual. Batch testing investigations compared total chlorine decay curves between inhibited and uninhibited samples to provide insight into the microbial contribution to disinfectant decay. Four types of decay curves were identified, with qualitative differences in the microbial contribution to the disinfectant residual decay. Liquid chromatography with organic carbon detection (LC-OCD) was applied to investigate changes in the character of the dissolved organic carbon over the course of the batch tests. Based on the results of this study, it is recommended to evaluate the results of nitrification batch tests based on a visual identification of the curve type and calculation of the decay rates and critical threshold residual (CTR), rather than relying on the microbial decay factor alone to express the results. An application of this work was in making comparisons to some models for nitrification proposed in the literature. The ultimate goal of these models is to provide drinking water system operators with a prediction of when nitrification episodes will occur so that action may be taken to avert them. The models considered in this study differ in their degree of complexity and in whether they are based on mechanistic considerations. The differences in the underlying principles and data required for analysis make these models suitable for different applications. The results of this evaluation support the use of the model of Fleming et al. (2005) in full-scale distribution systems and the use of the model by Yang et al. (2008) for research applications, while the other models considered can still offer some useful insights. The results of this research can be applied to monitoring and operational practices in chloraminated distribution systems where nitrification is a potential concern. The correlations between parameters that have significance to distribution system nitrification that were found in this study, along with the modelling and batch testing evaluated in this work, can provide insight into predicting conditions favourable to nitrification and avoiding or averting nitrification episodes.

Previous efforts to apply risk analysis for water distribution systems (WDS) have not typically included explicit hydraulic simulations in their methodologies. A risk classification scheme is here employed for identifying vulnerable WDS components subject to an intentional water contamination event. A Monte Carlo simulation is conducted including uncertain stochastic diurnal demand patterns, seasonal demand, initial storage tank levels, time of day of contamination initiation, duration of contamination event, and contaminant quantity. An investigation is conducted on exposure sensitivities to the stochastic inputs and on mitigation measures for contaminant exposure reduction. Mitigation measures include topological modifications to the existing pipe network, valve installation, and an emergency purging system. Findings show that reasonable uncertainties in model inputs produce high variability in exposure levels. It is also shown that exposure level distributions experience noticeable sensitivities to population clusters within the contaminant spread area. The significant uncertainty in exposure patterns leads to greater resources needed for more effective mitigation.

Threat management of water distribution systems is essential for protecting consumers. In a contamination event, different strategies may be implemented to protect public health, including flushing the system through opening hydrants or isolating the contaminant by manipulating valves. To select the most effective options for responding to a contamination threat, the location and loading profile of the source of the contaminant should be considered. These characteristics can be identified by utilizing water quality data from sensors that have been strategically placed in a water distribution system. A simulation-optimization approach is described here to solve the inverse problem of source characterization, by coupling an evolutionary computation-based search with a water distribution system model. The solution of this problem may reveal, however, that a set of non-unique sources exists, where sources with significantly different locations and loading patterns produce similar concentration profiles at sensors. The problem of non-uniqueness should be addressed to prevent the misidentification of a contaminant source and improve response planning. This paper aims to address the problem of non-uniqueness through the use of Niched Co-Evolution Strategies (NCES). NCES is an evolutionary algorithm designed to identify a specified number of alternative solutions that are maximally different in their decision vectors, which are source characteristics for the water distribution problem. NCES is applied to determine the extent of non-uniqueness in source characterization for a virtual city, Mesopolis, with a population of approximately 150,000 residents. Results indicate that NCES successfully identifies non-uniqueness in source characterization and provides alternative sources of contamination. The solutions found by NCES assist in making decisions about response actions. Once alternative sources are identified, each source can be modeled to determine where the vulnerable areas of the system are, indicating the areas where response actions should be implemented.

The purpose of this research is to compare the performance for the water quality of two traditional water treatment plants (WTP) and three advanced water treatment plants (AWTP), and to investigate the treated drinking water in distribution systems in Kaohsiung area for promoting the consumers¡¦ self-confidence. Samples of the treated water from five major water supplies¡¦ WTP(noted numbers: WF1, WF2, WF3, WF4 and WF5) and the tap water at user¡¦s end were selected in planning of this work. It was the traditional WTP stage with treated drinking water and distribution systems in Kaohsiung area During 91 year to 92 year, so we conducted WF1 and WF2 of 8 times sampling and WF3, WF4 and WF5 for 2 times sampling at this stage. In and after 93 year, we conducted WF1, WF2, WF3, WF4 and WF5 of 8 times sampling from 93 year to 94year for the advanced WTP stage. The major tests related with the parameters of influencing operation condition included pH, odor (abbreviated as TON), total trihalomethane (abbreviated as THMs), haloacetic acids (abbreviated as HAAs), nitrogen (abbreviated as, NH3-N, hardness, total dissolved solid (abbreviated as TDS), alkalinity, total organic carbon (abbreviated as TOC), calcium ion, flavor profile analysis (abbreviated as FPA), and suspension observation in boiling with treated waters from two WTP , three AWTP and the tap water at user¡¦s end in a distribution system. It point out the better quality of treated water used the advanced water treatment plants than that of traditional water treatment plant. The items with improvement of water quality, including THMs, HAAs, hardness, TON, 2-MIB, TOC, alkinality and Ca ions concentration, is presented. Their efficiency for improvement are respectively 47%, 29%, 43%, 11%, 29%, 15%, 14% and 34%. The insignificant efficiency were concentrated at TDS, NH3-N, pH and FPA. Water quality of six items are fitted for the drinking water standard at present in Taiwan (such as: odor<3 TON; THMs<0.1 mg/L; NH3-N<0.1 mg/L; TDS< 600 mg/L; Hardness <400 mg as CaCO3/L; 6.0<pH <8.5). The HAAs is fit for water quality USEPA first stage water standard (HAAs<80 £gg/L). In the suspension observation in boiling experimentation, we cooperate with the experiment of suspension observation in boiling to do contrast with TDS and hardness experiment, which can find out, the treated water after the advanced procedure, the time with boiling increases, the condition of its suspended substance has great reduction. It show treated drinking water after the advanced WTP can huge improve the traditional WTP¡¦s white suspended substance or white material precipitate questions in the boiling. In the contour map for water quality , we found that Gushan District, Lingya District, Qianzhen District, Xiaogang District, Fongshan City and Daliao Shiang etc had higher concentration profile in the four season (included spring, summer, fall and winter ) and during two seasons (included raining and drying) in the water supplies systems. We hope the contour map can offer a clear information of conveyer system administrator of drinking water and let administrator know where areas have high concentration produced in water quality management planning, in order to having priority or effective solutions (included washing the pipeline, changing the pipeline, changing the water flow, etc.).

The distribution system containing numerous protective facilities and switch equipment ranges over a wide boundary . The most urgent problem the dispatcher has to tackle right after the breakdown of distribution system in how to resume as soon as possible power supply for the none-faulted out-of-service area. Therefore, distribution system service restoration is an important and practical subject. During the process of maintaining and operation ,the distribution district collected a lot of data. These data includes substation-related automatic operating data , switch section of doing a feeder , load data of high and low tension customers, and historical distribution system planning information concerning load transfer while operation, etc. The useful resource could help the dispatcher to get the best load transfer on distribution system service restoration. Datum-oriented researcher refers to the exploration of the concealing regulations and knowledge and the techniques regarding comprehensible model. This thesis manages to collect the maintaining and operation data of the distribution district ; it makes use of the information exploration techniques and ID3 decision tree and fuzzy theory to get the load transfer rule and knowledge , and to establish the load transfer model. After the fault occurred, it would help the dispatcher to get the best tactics for the load transfer on distribution system service restoration under the constraint condition. This thesis chooses the underground distribution system in sijhih of the Keeling District Offices of Taiwan Power Company as a sample. That underground distribution system comprising 8 distribution feeder ,73 distribution spaces,16 high tension customers, 28 feeder section, 4 feeder-tie-switch and 19 lateral-tie-switch will be simulated on computers to verify the proposed method for the distribution system service restoration.