Στην παρούσα διπλωματική εργασία εξετάζεται το ζήτημα της προστασίας σε Συστήματα Διανομής Ηλεκτρικής Ενέργειας με παρουσία Κατανεμημένης Παραγωγής. Η παραδοσιακή ακτινική μορφή των Συστημάτων Διανομής μεταβάλλεται με την παρουσία μονάδων Κατανεμημένης Παραγωγής, καθώς αυτές αποτελούν ενεργά στοιχεία και συμβάλλουν στο ρεύμα βραχυκύκλωσης. Συνεπώς ανακύπτει ένα σύνολο προβλημάτων στην λειτουργία του Συστήματος Προστασίας, όπως αύξηση του επιπέδου σφάλματος και διαταραχή στην επιλογική συνεργασία των διατάξεων προστασίας. Συχνά, τα προβλήματα που επιφέρει η παρουσία μονάδων Κατανεμημένης Παραγωγής στο Σύστημα Προστασίας του δικτύου διανομής, θέτουν το όριο στην εγκατάσταση περαιτέρω μονάδων. Αρχικά, παρουσιάζονται γενικές έννοιες, που έχουν σχέση με την προστασία σε δίκτυα διανομής , και παρατίθενται γενικά στοιχεία για την Κατανεμημένη Παραγωγή. Στην συνέχεια, παρέχεται η μεθοδολογία υπολογισμού των ρευμάτων βραχυκύκλωσης και τα μοντέλα των στοιχείων σε περίπτωση σφάλματος. Με τα ανωτέρω, επεξηγούνται οι αλλαγές στο ισοδύναμο κύκλωμα σε περίπτωση σφάλματος του Συστήματος Διανομής με την παρουσία Κατανεμημένης Παραγωγής και αναφέρεται το ζήτημα της αύξησης του επιπέδου σφάλματος. Επιπλέον, παρουσιάζονται τα επιμέρους ζητήματα που έχουν σχέση με τις επιπτώσεις της παρουσίας Κατανεμημένης Παραγωγής στο Σύστημα Προστασίας του Συστήματος Διανομής, όπως το ζήτημα της διαταραχής στην επιλογική συνεργασία ηλεκτρονόμων, ασφαλειών και διακοπτών αυτόματης επαναφοράς, το ζήτημα της μείωσης της επέκτασης των ηλεκτρονόμων απόστασης κ.α. Ακολούθως, επεξηγείται η Προστασία Διασύνδεσης και οι μέθοδοι και πρακτικές που χρησιμοποιούνται ώστε να προσαρμόζεται μία μονάδα Κατανεμημένης Παραγωγής στην παραδοσιακή λειτουργία του Συστήματος Προστασίας του Συστήματος Διανομής. Ιδιαίτερα αναλύεται το φαινόμενο της λειτουργίας νησίδος ενώ επεξηγείται και ο ρόλος του μετασχηματιστή διασύνδεσης στην λειτουργία του Συστήματος Προστασίας του δικτύου. Με βάση την ανάλυση και τη θεωρητική εξέταση εννοιών, μεθόδων και επιμέρους ζητημάτων (Μέρος Α), στο Β Μέρος της παρούσας εργασίας, παρουσιάζονται χαρακτηριστικά παραδείγματα εγκατάστασης Κατανεμημένης Παραγωγής σε εναέρια ακτινικά δίκτυα Μέσης Τάσης του ελληνικού Συστήματος Ηλεκτρικής Ενέργειας, στα οποία διερευνώνται οι επιπτώσεις στην λειτουργία του Συστήματος Προστασίας. Μέσω της μελέτης περιπτώσεων καταδεικνύεται ο ρόλος των χαρακτηριστικών των μονάδων Κατανεμημένης Παραγωγής και της θέσης εγκατάστασης τους στην εμφάνιση πιθανών προβλημάτων. Η διαταραχή στην επιλογική συνεργασία διακόπτη αυτόματης επαναφοράς και ασφαλειών, η εσφαλμένη λειτουργία του διακόπτη αυτόματης επαναφοράς λόγω ρευμάτων βραχυκύκλωσης και η αύξηση του επιπέδου σφάλματος, προκύπτουν ως τα σημαντικότερα προβλήματα. Τέλος, εξάγονται γενικά συμπεράσματα και προτείνονται λύσεις. / -

Chlorine is the most widely used disinfectant for drinking water treatment. Chlorine canreact with natural organic matter (NOM) in water sources resulting in the formation of potentially carcinogenic disinfection by-products (DBPs). The most common DBPs measured in chlorinated drinking water distribution systems are trihalomethanes (THMs) and haloacetic acids (HAAs). In 2005, the City of Kamloops, British Columbia upgraded the drinking water treatment system to ultrafiltration membrane treatment. The objective of this study was to determine the extent to which upgrades to a drinking water treatment system, specifically, implementation of an ultrafiltration treatment process, impacted DBP formation within a distribution system. This study used a two-phase research approach. Phase I of the study was a distribution system monitoring program that collected water samples and physical and chemical information using data loggers at five sampling sites within the distribution system. Phase II of the study used bench-scale simulations that modeled DBP formation using a flow-through reactor system, the material-specific simulated distribution system (MS-SDS), constructed of pipe material resurrected from the City of Kamloops distribution system. Phase I results suggested that implementation of the ultrafiltration treatment process and accompanying treatment system upgrade was not effective at reducing the concentration of DBPs delivered to consumers. Concentrations of THMs remained relatively constant at sampling sites, while concentrations of HAAs increased following implementation of the ultrafiltration treatment process. The increase in HAA formation was likely due to an increase in retention time of the water within the distribution system following implementation of the ultrafiltration treatment process, rather than due to the treatment process itself. The results of this study are consistent with previous work on South Thompson River water DBP precursors, which suggested that THM and HAA precursors of this source water are small and hydrophilic, and therefore cannot be removed by ultrafiltration processes. Phase II results showed that the MS-SDS was more representative of distribution system c onditions than traditional glass bottles to estimate DBP formation. It is recommended that the MS-SDS be used in parallel with a simultaneous distribution system monitoring program to estimate distribution system retention times from THM and HAA concentrations.

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Fault location is very important for distribution systems, and quickly identifying the fault and restoring the system can help reduce the outage time and make the system more reliable. In this thesis, a method for locating faults on distribution systems is introduced to quickly identify the faulted feeder sections by using the overcurrent information from the switches in the system. Fuzzy logic is utilized. The proposed method can quickly and accurately locate faulted sections with different fault locations, fault types and fault resistances. The method is applicable to cases with single-faults or multi-faults, and is applicable to networks with multi-sources. The case study has demonstrated the effectiveness of the proposed method.

In recent decades, interest in placing renewable resources in conventional power systems has increased because of their ability to reduce fossil fuel consumption, which leads to the preservation of the environment. The rapid increase in employing these renewable resource-based DGs drives the system to be more dynamic, and causes many obstacles that need to be overcome. Power system planners and operators should look at the distribution system from another angle, taking into consideration the intermittent behavior of most renewable resources. Furthermore, solid models that are able to handle the uncertainty in generation levels are required. This thesis presents a comprehensive probabilistic model for representing renewable energy resources in long term planning problems. This model utilized large historical data sets, grouping technique, and statistical analysis in order to handle the fluctuations that are caused by the variations in wind speed or solar irradiance. In this research, renewable resources (wind and PV based DGs) ae well as dispatchable units are optimally allocated and sized using a probabilistic optimization model. This model incorporates the intermittent nature of wind speed and solar radiation into the deterministic optimal power flow equations. The variability from the load side and the uncertainty from the feeding side are considered. Genetic algorithm is used in order to minimize the annual energy losses of a distribution system. This thesis proposes a new iterative-based optimization algorithm is proposed in order to determine the minimum number of states that can precisely describe or represent the behavior of wind speed and solar irradiance in operational planning problems. This algorithm is evaluated using a power system planning problem. The proposed algorithm takes into account the annual energy losses and the total DG penetration level and considers them as an indication of how far the proposed method's outcomes are from the actual results. Three di fferent data groupings are applied (hourly, seasonally, and yearly) to investigate the variety of weather and electricity demands on the proposed method. The obtained results should be maintained within an acceptable limit of error which is in this thesis, 2:5%, and any violation of this limit will interrupt the algorithm sequences. The importance of this method actually lies in its ability to reduce the complexity in reliability analysis such that the number of overall system states will be minimized when the analytical evaluation methods are utilized.

The objective of the research is to formulate and demonstrate protection schemes for radial and loop systems, an active distribution system, and a microgrid. The schemes are composed of a) A new loop scheme by utilizing voltage, current, and time (VIT) reclosers and sectionalizers and b) A new protection scheme, the dynamic state estimation-based protection, for active distribution systems and microgrids. The first part of the research explores the closing onto a fault during the conventional loop sectionalizing scheme and provides a VIT scheme that can solve the problem. The immediate benefit of the VIT schemes is a reduction of the nuisance trips because of the fault closing onto a fault. Moreover, the number of protection zones is increased by the application of the VIT sectionalizers. This thesis demonstrates the VIT protection scheme for a traditional distribution system and presents numerical experiments using various test scenarios with various fault locations. The simulation results verify that the protection scheme successfully performs the automatic load transfer scheme for a loop system. The second part of the research identifies the increased number of protection issues according to the installation of distributed generations (DGs) and provides solution to the problem. To solve the issue, a new fault detection scheme, dynamic state estimation-based protection scheme, is illustrated in this thesis based on synchronized measurements. The method uses dynamic state estimation, based on the dynamic model of the component that accurately reflects the nonlinear characteristics of the component. Numerical experiments show that the protection of active distribution systems and microgrids is feasible in real time.

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.

Chlorine is the most widely used disinfectant for drinking water treatment. Chlorine canreact with natural organic matter (NOM) in water sources resulting in the formation of potentially carcinogenic disinfection by-products (DBPs). The most common DBPs measured in chlorinated drinking water distribution systems are trihalomethanes (THMs) and haloacetic acids (HAAs). In 2005, the City of Kamloops, British Columbia upgraded the drinking water treatment system to ultrafiltration membrane treatment. The objective of this study was to determine the extent to which upgrades to a drinking water treatment system, specifically, implementation of an ultrafiltration treatment process, impacted DBP formation within a distribution system. This study used a two-phase research approach. Phase I of the study was a distribution system monitoring program that collected water samples and physical and chemical information using data loggers at five sampling sites within the distribution system. Phase II of the study used bench-scale simulations that modeled DBP formation using a flow-through reactor system, the material-specific simulated distribution system (MS-SDS), constructed of pipe material resurrected from the City of Kamloops distribution system. Phase I results suggested that implementation of the ultrafiltration treatment process and accompanying treatment system upgrade was not effective at reducing the concentration of DBPs delivered to consumers. Concentrations of THMs remained relatively constant at sampling sites, while concentrations of HAAs increased following implementation of the ultrafiltration treatment process. The increase in HAA formation was likely due to an increase in retention time of the water within the distribution system following implementation of the ultrafiltration treatment process, rather than due to the treatment process itself. The results of this study are consistent with previous work on South Thompson River water DBP precursors, which suggested that THM and HAA precursors of this source water are small and hydrophilic, and therefore cannot be removed by ultrafiltration processes. Phase II results showed that the MS-SDS was more representative of distribution system c onditions than traditional glass bottles to estimate DBP formation. It is recommended that the MS-SDS be used in parallel with a simultaneous distribution system monitoring program to estimate distribution system retention times from THM and HAA concentrations.

abstract: There has been a considerable growth in distributed photovoltaic (PV) genera-tion and its integration in electric power distribution systems. This has led to a change in the distribution system infrastructure. Properly planned distributed gen-eration can offer a variety of benefits for system operations and enhance opera-tional performance of the distribution system. However, high penetration of PV resources can give rise to operating conditions which do not arise in traditional systems and one of the potential issues that needs to be addressed involves impact on power quality of the system with respect to the spectral distortion in voltages and currents. The test bed feeder model representing a real operational distribution feeder is developed in OpenDSS and the feeder modeling takes into consideration the ob-jective of analysis and frequency of interest. Extensive metering infrastructure and measurements are utilized for validation of the model at harmonic frequencies. The harmonic study performed is divided into two sections: study of impact of non-linear loads on total harmonic voltage and current distortions and study of impact of PV resources on high frequency spectral distortion in voltages and cur-rents. The research work incorporates different harmonic study methodologies such as harmonic and high frequency power flow, and frequency scan study. The general conclusions are presented based on the simulation results and in addition, scope for future work is discussed. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014