High-impedance faults (HIFs) on distribution feeders are abnormal electrical conditions that cannot be detected by conventional protection schemes. These faults pose a threat on human lives when neighboring objects become in contact with the line's bare and energized conductors. An accurate electrical model for a HIF is implemented to investigate typical patterns in the line's current that allow for the detection of these faults. The occurrence of HIFs is detected with harmonic-current phase analysis and localized with recloser-sectionalizer technology as presented in this work. A sectionalizer algorithm is then presented showing the decision criteria for HIF declaration and shown to discriminate against nominal behavior in distribution feeders of similar harmonic content. Finally, it is shown that the algorithm will not produce a misreading when a current transformer enters saturation. / Master of Science

Failure of pipes in water distribution systems is a common occurrence especially in large cities. The failure of a pipe results in: loss of water; property damage; interruption of service; decreased system performance; and the financial cost of restoring the failed pipe. The cost of replacement and rehabilitation in the United States is estimated at 23 plus billion dollars. It is virtually impossible to replace all vulnerable pipes at the same time. As a result, there is a need for methods that can help in progressive system rehabilitation and replacement subject to budgetary constraints. If delaying is considered a good strategy due to the time value of money then, the timing of preventive maintenance becomes a crucial element for system maintenance and operation. The central under pinning element in the decision process for scheduling preventive maintenance is the deteriorating nature of a pipe under a given surrounding. By planning to replace pipes before they fail, proper planning can be put in place for securing of finances and labor force needed to rehabilitate the pipes. With this approach, service interruptions are minimized as the loss of service time is limited to the time used in replacing the pipe. In this research, a mechanistic model for assessing the stage of deterioration of an underground pipe is developed. The developed model consists of three sub-models namely, the Pipe Load Model (PLM), the Pipe Deterioration Model (PDM), and the Pipe Break Model (PBM). The PLM simulates the loads and stresses exerted on a buried water main. These loads include the earth load, traffic load, internal pressure, expansive soil loads, thermal, and frost loads. The PDM simulates the deterioration of the pipe due to corrosion resulting from the physical characteristics of the pipe environment. The pipe deterioration effect is modeled in two stages. First, the thinning of the pipe wall is modeled using a corrosion model. Second, the localized pit growth is used to determine the residual strength of the pipe based on the fracture toughness and the initial design strength of the pipe. The PBM assesses the vulnerability of a pipe at any time in terms of a critical safety factor. The safety factor is defined as the ratio of residual strength to applied stress. For a conservative estimate the multiplier effect due to thermal and frost loads are considered. For a chosen analysis period, say 50 years, the pipes with safety factors less than the critical safety factor are selected and ordered by their rank. Aided by the prioritized list of failure prone pipes, utilities can organize a replacement schedule that minimizes cost over time. Additionally a physically based regression model for determining the optimal replacement time of pipe is also presented. A methodology for assessing the consequences of accelerated and delayed replacement is also provided. The methodologies developed in this dissertation will enable utilities to formulate future budgetary needs compatible with the intended level of service. An application of the model and results are included in the dissertation. / Ph. D.

Distribution systems across most parts of the globe are highly radial in nature. As loads are gradually increased on a particular distribution system, a higher operating current state leading to increased fault current levels is attained. Hence, the relay co-ordination is disturbed and equipments such as feeders and circuit breakers need to be replaced with higher rating so that they can handle the new currents often leading to expensive retrofit costs. The use of fault current limiter (FCL) is proposed to mitigate the effects of high current levels on a distribution system. A comprehensive and up-to-date literature review of FCL technologies is presented. Detailed efforts of an in-house developed behavioral superconducting FCL model are delineated, including FCL control algorithm and its implementation in PSCAD®/EMTDC environment. Results from simulation studies are investigated and compared to an actual FCL commissioned by Z-energy to highlight the effectiveness of a generic model without having to access proprietary details. Extending those concepts, a solid-state and hybrid type of limiter is also modeled and it results discussed. Finally, an impact assessment is conducted on the distribution protection scheme, due to the FCL being inserted and subsequently operated in the distribution system. / Master of Science

In electricity markets, capacity cost must be determined in order to make capacity trading. In this thesis, capacity cost and the factors deriving the capacity cost are studied. First, fixed capacity cost of power plants is examined. Direct and indirect costs of fixed capacity cost are detailed with respect to different types of power plants and the impact of these factors to the capacity cost is given. Second, interconnection and system utilization costs of transmission and distribution system are considered in order to simulate energy flow from the producer to the customer. Finally, a capacity cost calculation program is practiced. By the help of this program, capacity cost of power plants is figured out, different cases are compared and the main factors affecting the capacity cost are discussed in detail.

No description available.

The increasing penetration of proactive agents in distribution systems (DS) has opened new possibilities to make the grid more resilient and to increase participation of responsive loads (RL) and non-conventional generation resources. On the resiliency side, plug-in hybrid electric vehicles (PHEV), energy storage systems (ESS), microgrids (MG), and distributed energy resources (DER), can be leveraged to restore critical load in the system when the utility system is not available for extended periods of time. Critical load restoration is a key factor to achieve a resilient distribution system. On the other hand, existing DERs and responsive loads can be coordinated in a market environment to contribute to efficiency of electricity consumption and fair electricity tariffs, incentivizing proactive agents' participation in the distribution system. Resiliency and market applications for distribution systems are highly complex decision-making problems that can be addressed using modern optimization techniques. Complexities of these problems arise from non-linear relations, integer decision variables, scalability, and asynchronous information. On the resiliency side, existing models include optimization approaches that consider system's available information and neglect asynchrony of data arrival. As a consequence, these models can lead to underutilization of critical resources during system restoration. They can also become computationally intractable for large-scale systems. In the market design problem, existing approaches are based on centralized or computational distributed approaches that are not only limited by hardware requirements but also restrictive for active participation of the market agents. In this context, the work of this dissertation results in major contributions regarding new optimization algorithms for market design and resiliency improvement in distribution systems. In the DS market side, two novel contribution are presented: 1) A computational distributed coordination framework based on bilateral transactions where social welfare is maximized, and 2) A fully decentralized transactive framework where power suppliers, in a simultaneous auction environment, strategically bid using a Markowitz portfolio optimization approach. On the resiliency side, this research proposed a system restoration approach, taking into account uncertain devices and associated asynchronous information, by means of a two-module optimization models based on binary programming and three phase unbalanced optimal power flow. Furthermore, a Reinforcement Learning (RL) method along with a Monte Carlo tree search algorithm has been proposed to solve the scalability problem for resiliency enhancement. / Doctor of Philosophy / Distribution systems (DS) are evolving from traditional centralized and fossil fuel generation resources to networks with large scale deployment of responsive loads and distributed energy resources. Optimization-based decision-making methods to improve resiliency and coordinate DS participants are required. Prohibitive costs due to extended power outages require efficient mechanisms to avoid interruption of service to critical load during catastrophic power outages. Coordination mechanisms for various generation resources and proactive loads are in great need. Existing optimization-based approaches either neglect the asynchronous nature of the information arrival or are computationally intractable for large scale system. The work of this dissertation results in major contributions regarding new optimization methods for market design, coordination of DS participants, and improvement of DS resiliency. Four contributions toward the application of optimization approaches for DS are made: 1) A distributed optimization algorithm based on decomposition and best approximation techniques to maximize social welfare in a market environment, 2) A simultaneous auction mechanism and portfolio optimization method in a fully decentralized market framework, 3) Binary programming and nonlinear unbalanced power flow, considering asynchronous information, to enhance resiliency in a DS, and 4) A reinforcement learning method together with an efficient search algorithm to support large scale resiliency improvement models incorporating asynchronous information.

The main aim of the study was to analyse the impact of physico-chemical parameters on drinking water quality, biofilm formation and antibiotic resistant bacteria in the drinking water distribution system in Mafikeng, North West Province, South Africa. Another objective was to isolate and characterise Pseudomonas and Aeromonas species from drinking water distribution system and detect the virulence gene determinants in the isolates by PCR analysis. The physico-chemical data obtained were subjected to statistical analysis using Excel 2007 (Microsoft) and SPSS (version 14.0) programmes. Pearson’s correlation product of the moment was used to determine the correlation between EC, TDS, pH and temperature. The two tailed test of significance (p<0.05) was used in order to determine the significance of the result. Antibiotic susceptibility tests were performed using Kirby-Bauer disk diffusion method. Cluster analysis based on the antibiotic inhibition zone diameter data of different organisms isolated from different sites was determined and was expressed as dendograms using Wards algorithm and Euclidean distance of Statistica version 7. Specific PCR was used to determine the identities of presumptive Pseudomonas and Aeromonas species through amplification of the gyrB, toxA and the ecfX gene fragments. Virulence gene determinants for the confirmed Pseudomonas and Aeromonas species were detected by amplifying the exoA, exoS and exoT genes and the aerA and hylH gene fragments, respectively. A Gene Genius Bio imaging system (Syngene, Synoptics; UK) was used to capture the image using GeneSnap (version 3.07.01) software (Syngene, Synoptics; UK) to determine the relative size of amplicons. Physico-chemical parameters were monitored from three drinking water sources three times a week and bacteriological quality was monitored weekly for four months from raw and treated drinking water. Water samples were analysed for pH, temperature, total dissolved solids (TDS) and electric conductivity (EC). Bacterial consortia from drinking water samples were isolated using selective media and enumerated. The results revealed a good chemical quality of water. However, the microbial quality of the water is not acceptable for human consumption due to the presence of Pseudomonas, Aeromonas, faecal coliforms (FC), total coliforms (TC) and Heterotrophic bacteria. The results showed that the drinking water is slightly alkaline with pH value ranging between7.7 to 8.32. What is of concern was the microbial quality of the water. Pseudomonas sp., faecal coliforms (FC), total coliforms (TC) and heterotrophic bacteria were present in some of the treated water samples. The most significant finding of this study is that all drinking water samples were positive for Pseudomonas sp.(>100/100ml), but also that when one considers the TDS it demonstrates that water from the Modimola Dam has an impact on the quality of the mixed water. The prevalence and antibiotic resistance profiles of planktonic and biofilm bacteria isolated from drinking water were determined. The susceptibility of these isolates was tested against 11 antibiotics of clinical interest and the multiple antibiotic resistance (MAR) patterns were compiled. The most prevalent antibiotic resistance phenotype observed was KF-AP-C-E-OT-K-TM-A. All isolates from all samples were susceptible to ciprofloxacin. However, all faecal coliforms and Pseudomonas spp. were susceptible to neomycin and streptomycin. On the contrary all organisms tested were resistant to erythromycin (100%) trimethoprim and amoxycillin. Cluster analysis based on inhibition zone diameter data could not differentiate the various isolated into sample types. The highest prevalence of antibiotic resistant isolates was observed in Modimola Dam and Molopo eye. Biofilms were investigated in both raw water and treated drinking water sources for the presence of faecal coliforms, total coliforms, Pseudomonas spp., Aeromonas spp. and heterotrophic bacteria based on conventional microbiology and molecular methods. Drinking water biofilms were grown twice and the biofilm developing device containing copper and galvanized steel coupons were utilized. The Mini Tap filter, a home water treatment device which can be used at a single faucet, under constant flow was used during the second collection of treated water samples from cold water taps. Scanning electron micrograph revealed the existence of biofilms in all the sites investigated and the highest density was obtained on galvanized steel coupons. Isolates were tested against the antibiotics ampicillin (10μg), cephalothin (5μg), streptomycin (10μg), erythromycin (15μg), chloramphenicol (30μg), neomycin (30 μg), amoxycillin (10 μg), ciprofloxacin (5 μg), trimethoprim (25μg), kanamycin (30μg), and oxytetracycline (30μg). The multiple antibiotic resistance profiles and the presence of virulence related genes were determined. Various types of drug resistance and presence of virulence genes were observed. The most prevalent resistance phenotype observed was KF-AP-C-E-OT-TM-A. In conclusion, the results indicated the occurrence of faecal indicator bacteria in the drinking water destined for human consumption. Faecal indicator bacteria are the major contributors of poor drinking water quality and may harbour opportunistic pathogens. This highlighted survival of organisms to treatment procedures and the possible regrowth as biofilms in plumbing materials. The detection of large proportion of MAR Aeromonas and Pseudomonas species which possessed virulent genes was a cause of concern as these could pose health risks to humans. The data obtained herein may be useful in assessing the health risks associated with the consumption of contaminated water. / PhD (Microbiology), North-West University, Potchefstroom Campus, 2014

The main aim of the study was to analyse the impact of physico-chemical parameters on drinking water quality, biofilm formation and antibiotic resistant bacteria in the drinking water distribution system in Mafikeng, North West Province, South Africa. Another objective was to isolate and characterise Pseudomonas and Aeromonas species from drinking water distribution system and detect the virulence gene determinants in the isolates by PCR analysis. The physico-chemical data obtained were subjected to statistical analysis using Excel 2007 (Microsoft) and SPSS (version 14.0) programmes. Pearson’s correlation product of the moment was used to determine the correlation between EC, TDS, pH and temperature. The two tailed test of significance (p<0.05) was used in order to determine the significance of the result. Antibiotic susceptibility tests were performed using Kirby-Bauer disk diffusion method. Cluster analysis based on the antibiotic inhibition zone diameter data of different organisms isolated from different sites was determined and was expressed as dendograms using Wards algorithm and Euclidean distance of Statistica version 7. Specific PCR was used to determine the identities of presumptive Pseudomonas and Aeromonas species through amplification of the gyrB, toxA and the ecfX gene fragments. Virulence gene determinants for the confirmed Pseudomonas and Aeromonas species were detected by amplifying the exoA, exoS and exoT genes and the aerA and hylH gene fragments, respectively. A Gene Genius Bio imaging system (Syngene, Synoptics; UK) was used to capture the image using GeneSnap (version 3.07.01) software (Syngene, Synoptics; UK) to determine the relative size of amplicons. Physico-chemical parameters were monitored from three drinking water sources three times a week and bacteriological quality was monitored weekly for four months from raw and treated drinking water. Water samples were analysed for pH, temperature, total dissolved solids (TDS) and electric conductivity (EC). Bacterial consortia from drinking water samples were isolated using selective media and enumerated. The results revealed a good chemical quality of water. However, the microbial quality of the water is not acceptable for human consumption due to the presence of Pseudomonas, Aeromonas, faecal coliforms (FC), total coliforms (TC) and Heterotrophic bacteria. The results showed that the drinking water is slightly alkaline with pH value ranging between7.7 to 8.32. What is of concern was the microbial quality of the water. Pseudomonas sp., faecal coliforms (FC), total coliforms (TC) and heterotrophic bacteria were present in some of the treated water samples. The most significant finding of this study is that all drinking water samples were positive for Pseudomonas sp.(>100/100ml), but also that when one considers the TDS it demonstrates that water from the Modimola Dam has an impact on the quality of the mixed water. The prevalence and antibiotic resistance profiles of planktonic and biofilm bacteria isolated from drinking water were determined. The susceptibility of these isolates was tested against 11 antibiotics of clinical interest and the multiple antibiotic resistance (MAR) patterns were compiled. The most prevalent antibiotic resistance phenotype observed was KF-AP-C-E-OT-K-TM-A. All isolates from all samples were susceptible to ciprofloxacin. However, all faecal coliforms and Pseudomonas spp. were susceptible to neomycin and streptomycin. On the contrary all organisms tested were resistant to erythromycin (100%) trimethoprim and amoxycillin. Cluster analysis based on inhibition zone diameter data could not differentiate the various isolated into sample types. The highest prevalence of antibiotic resistant isolates was observed in Modimola Dam and Molopo eye. Biofilms were investigated in both raw water and treated drinking water sources for the presence of faecal coliforms, total coliforms, Pseudomonas spp., Aeromonas spp. and heterotrophic bacteria based on conventional microbiology and molecular methods. Drinking water biofilms were grown twice and the biofilm developing device containing copper and galvanized steel coupons were utilized. The Mini Tap filter, a home water treatment device which can be used at a single faucet, under constant flow was used during the second collection of treated water samples from cold water taps. Scanning electron micrograph revealed the existence of biofilms in all the sites investigated and the highest density was obtained on galvanized steel coupons. Isolates were tested against the antibiotics ampicillin (10μg), cephalothin (5μg), streptomycin (10μg), erythromycin (15μg), chloramphenicol (30μg), neomycin (30 μg), amoxycillin (10 μg), ciprofloxacin (5 μg), trimethoprim (25μg), kanamycin (30μg), and oxytetracycline (30μg). The multiple antibiotic resistance profiles and the presence of virulence related genes were determined. Various types of drug resistance and presence of virulence genes were observed. The most prevalent resistance phenotype observed was KF-AP-C-E-OT-TM-A. In conclusion, the results indicated the occurrence of faecal indicator bacteria in the drinking water destined for human consumption. Faecal indicator bacteria are the major contributors of poor drinking water quality and may harbour opportunistic pathogens. This highlighted survival of organisms to treatment procedures and the possible regrowth as biofilms in plumbing materials. The detection of large proportion of MAR Aeromonas and Pseudomonas species which possessed virulent genes was a cause of concern as these could pose health risks to humans. The data obtained herein may be useful in assessing the health risks associated with the consumption of contaminated water. / PhD (Microbiology), North-West University, Potchefstroom Campus, 2014

Water distribution system utilities must be able to maintain a system’s assets (i.e., pumps, tanks, water mains, etc.) in good working condition in order to provide adequate water quantity and quality to its customers. Various asset management approaches are employed by utilities in order to make optimal decisions regarding the renewal of system components. Part of a good asset management approach is performing a comprehensive risk analysis which consists of considering all potential ways in which the system may fail, the likelihood failure of for each scenario, and the consequences of said failure. This study investigates a water distribution system’s risk of failure due to both acute transient events (e.g., pump trip) and standard pressure fluctuations due to daily system operations. Such an analysis may be useful in optimal decision making such as asset monitoring, scheduling of condition assessments or system renewal projects, policy implementation, and investment priorities in order to keep the utility’s total costs at a minimum. It may also be useful as a precautionary measure to help prevent catastrophic failures such as large main blowouts for which the utility would incur substantial costs, both direct and indirect. As part of this thesis, a database of water distribution system models is used to analyze the effects of an acute transient event for different system configurations. The database was created at the University of Kentucky and has been made available to the research community to test newly developed algorithms for various studies including optimal system operations and optimal system design.

The amoebae Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are free-living amoebae found in both water and soil. They are opportunistic pathogens in humans. Acanthamoeba is the most common cause of illness, usually infecting the eyes and sometimes causing a sight-threatening keratitis. Acanthamoeba spp. and B. mandrillaris can cause granulomatous amoebic encephalitis, in addition to infections of the lungs and skin. N. fowleri causes primary amoebic meningoencephalitis . There is little known regarding the ecology and occurrence of these organisms. A total of 36 high-use recreational surface waters in Arizona were surveyed over a period of two years to assess the occurrence of N. fowleri and seasonal and environmental factors. Overall, 9.3% of the warm weather samples collected were positive for N. fowleri, whereas 16.3% of the samples were positive during cold weather. Although the presence of N. fowleri could not be significantly correlated with physical and chemical parameters such as temperature, pH, turbidity, conductivity, and the presence of heterotrophic bacteria, total coliforms, and Escherichia coli, a weak correlation (0.52) with live amoebic activity was observed. Five lakes to the north and northeast of Phoenix tested positive for the N. fowleri on more than one occasion over multiple seasons. Finished drinking water samples (n= 785) from a municipal potable distribution system were evaluated for the presence of N. fowleri, B. mandrillaris and Acanthamoeba spp. from 18 different regions during three different sampling periods. Physical and chemical parameters were also evaluated but provided no significant correlations with the occurrence of amoebae or indicator organisms. A total of 138 samples (17.9%) were positive for viable amoebae in distribution water with more than an adequate chlorine residual (average of 0.86 mg/L). Microorganisms that are typically used to monitor microbial water quality such as coliforms and E. coli would likely not be found under these circumstances. Clusters with three or more samples testing positive for viable amoebae per region were observed during all three periods. Viable amoebae may not only provide a better assessment of the microbial quality of water, but such clustering could reveal areas with potential water quality issues within the distribution system.