Dissertations / Theses on the topic 'Medium Voltage Network'

To provide electricity access to the population currently deprived of it, is one of the sustainable development goals. Although the number is decreasing and is below 1 billion people without access to electricity for the first time in the year 2017, there is still much to be done. At the current rate of electrification an additional approximately 550 million people of those deprived now would have access to electricity by the year 2030, but 650million would still be without electricity access. This report studies the spatial factors that affect how MV network expansion occurs. The motivation for this report comes from studying previous research work using GIS and studying the Open Source Spatial Electrification Tool (OnSSET) which is developed by the division of Energy Systems Analysis at KTH. The objective of this tool is to aid electrification planning by examining options ranging from national grid expansion to off-grid resources such as solar, wind, hydro based on spatial analysis of data. The study is conducted into two parts. First by undertaking a literature review of relevant GIS based electrification and utility planning articles, to identify the factors that contribute to the costs of grid network extension. Thereafter, existing grid networks in Malawi, Nigeria and Uganda have been analyzed to examine the correlation to the different factors identified in the literature review. A qualitative comparison is conducted between the different countries to aid the development of spatial analysis tools such as OnSSET. The observations made studying the countries in the Sub-Saharan Africa region are noted down in the results section depicting similarities in planning and implementation of the grid network. Finally, necessary suggestions are made that might supplement and help the efforts in geospatial electrification network planning tools like OnSSET. The differences between literature review and practical geospatial analysis tools is also mentioned including the challenges faced during this thesis.
Att kunna förse el till befolkningen som för närvarande ej har tillgång till det är ett av de globala hållbarhetsmålen. Även om andelen av befolkningen som inte har tillgång till el sjunker och befinner sig under 1 miljard för första gången år 2017, behöver mer göras. Vid nuvarande tillväxt av antalet människor som får tillgång till el kommer ytterligare 550 miljoner ha tillgång år 2030, men 650 miljoner kommer fortfarande vara utan. Denna rapport studerar de rumsliga faktorerna som påverkar sättet som utbyggnad av MV-nätverk sker. Motiveringen till denna rapport härrör från tidigare forskning med GIS och undersökningar av Open Source Spatial Electrification Tool (OnSSET) vilket är utvecklat av enheten för Energisystemanalys på KTH. Syftet med detta verktyg är att bistå planering för elektrifiering genom att analysera såväl utbyggnad av det nationella elnätet som fristående alternativ som sol-, vind- och vattenbaserade resurser med hjälp av spatiala dataanalyser. Denna undersökning genomförs i två delar. Den första delen behandlar litterära studier av relevanta GISbaserade studier för elektrifikations och nätverksplanering,, för att identifiera faktorer som bidrar till kostnaden av nätverkets expansion. Den andra delen behandlar existerande nätverk i Malawi, Nigeria och Uganda som har analyserats för att analysera korrelationen mellan de faktorer som identifierats i den litterära undersökningen. En kvalitativ jämförelse genomförs mellan de olika länderna för att bidra till utvecklingen av rumsliga analytiska verktyg som OnSSET. Observationerna som gjorts vid undersökningen i delen av Afrika söder om Sahara är noterade i resultatsektionen som skildrar likheter i planering och implementering av rutnätverken. Slutligen är nödvändiga förslag gjorda som möjligen kan bidra till och hjälpa i arbetet för geospatial elektrifikations planeringsverktyg som OnSSET. Skillnader mellan litterära undersökningen och praktiska geospatiala analysverktyg är också nämnd inklusive utmaningarna inför denna avhandling.

This thesis deals with the modelling and simulation of MV network overcurrent protection using EMTP. Transmission lines 25 Km in length for both radial and loop network with constant parameters operates at 50 Hz and 66 kV line to line voltages are simulated using EMTP. The first part of the thesis discusses the simulation of Radial network with unearthed neutral for analysing the behaviour of the fault current making the comparison with healthy feeder. Second part is to use a Radial network with compensated neutral, Petersen Coil (PC) is used for compensation of the short circuit current making the similar comparison. Third step is to design a 67N directional replay protection in EMTP to trip the circuit breaker in the fault situation. Then using both Radial and Loop network, a comparison and response of the 67N protection in both situations is analysed. Several simulations of Single Line to Ground Faults (SLGF) with different fault locations were carried out to verify the correct operation of the relay based on the developed protection scheme. The results of the simulation the operation of the relay based on its protection scheme and its response time based on the fault location. Finally, delay between the blocking signals are inserted to see the behaviour of the protection system under loop network configuration.

Ces travaux proposent des améliorations de méthodes de localisation desdéfauts électriques sur les réseaux électriques de distribution. Les réseaux de transportont rapidement été instrumenté en élément de protection. En effet, un incident survenantsur le réseau de transport peut entrainer de graves conséquences s’il n’est pas traité rapidement.Les réseaux de distribution quand à eux possèdent un schéma de protectionminimal. Cependant le développement des smart grids (ou réseaux intelligents) amène denouvelles possibilités avec l’ajout d’équipements de mesures sur le réseau de distribution.Les travaux présentés dans cette thèse développent deux méthodes de localisation de défaut.La première permet de mieux utiliser l’équipement déjà en place (indicateurs depassage de défaut) afin d’isoler de manière rapide et fiable la zone concernée par le défaut.La deuxième permet une localisation précise (en distance) des différents lieux de défautspossibles à partir de mesures électriques
This thesis proposes to improve fault localization methods for electricalpower distribution networks. Transmission networks were quickly equipped with protectionand fault localization equipments. Indeed, faults on the transmission network need tobe dealt with quickly in order to avoid serious consequences. Unlike transmission networks,distribution networks have a minimal protection scheme. The smart grid developmentsbring new possibilities with the installation of new equipments giving access to many newvariables. The work presented in this thesis develop two fault localization method. Thefirst aims in using the equipment already installed (fault indicators) in order to isolatequickly and efficiently the zone concerned by the fault. The second method performs aprecise localization (in distance) of the different possible fault locations from the electricalmeasurements made on the network

Bei der Zustandsbewertung von Kabeln steht derzeit das Mittelspannungsnetz im Fokus der Betrachtungen. Das Mittelspannungsnetz verbindet das Hochspannungsnetz mit dem Niederspannungsnetz und nimmt damit eine besondere Bedeutung ein. Störungen in diesem Netz wirken sich direkt als Versorgungsunterbrechung auf den Letztverbraucher aus. Rund 80 bis 85 % der Versorgungsunterbrechungen resultieren aus Problemen im Mittelspannungsnetz, sodass dortige Aktivitäten den größten Hebel bei der Steigerung der Versorgungsqualität entwickeln. Mittels Zustandsbewertung von Kabeln können verdeckte Fehler aufgedeckt oder deren Alterungszustand bestimmt werden. Nicht jeder diagnostizierte Fehler führt unmittelbar zum Ausfall. Er beschleunigt jedoch die Alterung, die letztendlich zum Ausfall führt. Die Arbeit beschäftigt sich mit der Identifizierung von Fehlern in Mittelspannungskabelmuffen im Zusammenhang mit der Alterung, um die Restlebensdauer auszunutzen und dem Ausfall zuvorzukommen
By evaluating the status of cables, hidden errors can be detected or their aging condition can be determined. Not every diagnosed fault leads directly to failure. However, it accelerates aging, which ultimately leads to failure. The work deals with the identification of faults in medium-voltage cable joints in connection with aging in order to exploit the remaining life and to prevent the failure

I samband med att mellanspänningsnätet kablifieras ökar också kraven vad gäller fellokalisering. För att hålla avbrottstiderna i nätet korta är effektiv felsökning erforderlig. Detta arbete syftar till att kartlägga och redogöra för begränsande faktorer som finns vid fellokalisering med fokus på pulsekometoden. Uppdraget utförs tillsammans med Vattenfall Eldistribution AB. Det har uppdagats problem gällande fellokalisering på mellanspänningskablar med pulsekometoden. Ett flertal faktorer bidrar till denna problematik. Resultatet från studien visar att kabelkonstruktionen är en betydande del i det som begränsar pulsekometodens användningsområden och funktionalitet. Rapporten redogör för grundläggande information kring konstruktion och typer av mellanspänningskablar. Kartläggningen uppvisar hur vattenträd påverkar en kabel negativt. Allmänt redogörs för vad som orsakar vattenträd samt vilka avhjälpande åtgärder som vidtas; trippelextrudering samt mantel- och isolationsprovning. Vidare beskrivs olika feltyper, kabeltyper, kabelgenerationer samt instrument- och metodtyper som alla är påverkande faktorer vid fellokalisering. Dokumentering är i högsta grad väsentligt för en lyckad felsökningsprocedur, vilket klarläggs i rapporten. Utöver dokumentation redogörs för hur kabelns kondition kan påverka felsökningsresultatet. Ett antal mätmetoder och mätinstrument finns till förfogande vid felsökning och provning. Alla har sina egna för- respektive nackdelar. De har även tillhörande användningsområden. Pulsekometerns grundfunktion studeras och förklaras. De övriga mätmetoderna, som används vid fellokalisering och provning, redogörs för endast generellt
As the medium voltage network cables in Sweden is buried down in the earth, the demand of fault localization expertise increases. To keep downtimes in the network short, the importance of effective fault localization is necessary. This work is aimed to map and visualize limiting factors within fault localization with focus on the TDR - Time Domain Reflectometry. This work is a collaboration with Vattenfall Eldistribution AB. Problems with fault localization on medium voltage cables with the TDR have been detected. A multiple factors are contributing to this problem. The results of this study show that the cable construction is a significant part in which extent the TDR can be used. The report are also accounting for basic information about construction and types. The mapping also illustrates water treeing and how it affects cables in a negative way. Visualization of what causes water treeing and several actions such as triple extrusion, jacket testing and insulation testing is included in the essay. Further information about fault types, cable types, cable generations, instrument types and method types is given. All of them are affecting factors within the area of fault localization. Documentation is highly important for a successful fault localization procedure, which is clarified in the report. Besides documentation the cable condition and the influence on it affecting the result of fault localization is stated. A number of measuring methods and instruments are available to use when fault localization and testing are occurring. Every instrument has their own advantages and disadvantages. They also have their own respective area of usage. The basic principle of TDR is studied and explained accordingly. The other measuring methods, which are used in fault localization and testing, are shown more generally

The aim of this dissertation is to investigate alternative, more reliable and cost effective ways of improving the reliability performance of medium voltage networks. Customers are mainly affected by faults on the distribution MV network, to which, consequently, we have to pay particular attention. A major requirement on electricity supply systems is high supply reliability for the customer which is mainly determined by the distribution networks. Power system reliability is an essential factor in the quality of supply and is directly related to the number and duration of outages. By analysing the power system properly, the weaknesses will then be identified and improvements can be introduced to minimise the occurrence of outages. A decrease in the outage rate will result in an improvement in reliability and quality of supply of the distribution MV network. The dissertation focuses on improving the network management by increasing the level of network automation and control which improves the operating efficiency of medium voltage distribution networks. Steps are shown how to equip the network according to progressive investment capability, from Fault Path Indicators (FPIs) and remote control Pulseclosing technologies to automatic FuseSavers and Tripsavers used in a feeder automation scheme to minimise the number of disturbances and the outage durations experienced when they occur. The results of a study analysing the impact of different intelligent automation solutions on the reliability performance of Medium Voltage distribution networks are presented in the dissertation. The respective system topologies are modelled and the resulting system reliability performance is determined by reliability calculations such as the SAIDI and SAIFI values. The results show that the distribution automation technologies can have a very significant impact on both the SAIDI and SAIFI performance of the systems. Further, selected details related to the implementation of such intelligent automation schemes are presented in this dissertation.

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
Dentre as diversas fontes de energia renovável, a energia eólica se destaca como uma das mais promissoras. Em meio ao cenário de crise energética em muitos países, crescimento da demanda, maior conscientização ambiental e maior exigência por uma energia de qualidade por parte das sociedades modernas, a energia eólica tem ganhado importância econômica e estratégica. No Brasil, os empreendimentos eólicos são contratados por meio de leilões através dos quais são declarados vencedores aqueles empreendimentos que ofertam o menor preço pela energia gerada. Este modelo vigente é responsável por acirrar a concorrência e, consequentemente, instigar a busca pela otimização das propostas. Considerando este aspecto, é de grande interesse o desenvolvimento de ferramentas computacionais que auxiliem profissionais a desenvolver projetos viáveis técnica e economicamente na fase de planejamento, e de preferência otimizados. Parques eólicos são compostos basicamente por aerogeradores, transformadores responsáveis por elevarem a tensão de saída das turbinas para níveis adequados de distribuição, cabos de média tensão e subestações. A construção da rede coletora de média tensão (rede interna), responsável pela interconexão de todos os aerogeradores e subestações, constitui parcela considerável dos custos globais, o que tem motivado diversos pesquisadores a publicar trabalhos que objetivam encontrar a melhor topologia da rede elétrica que, ao mesmo tempo, minimize os custos e respeite os critérios técnicos estabelecidos, tais como: radialidade, conectividade, variação da tensão nos barramentos, máxima condução de corrente pelo condutor (sobrecarga nos ramos), entre outras. Tendo em vista tais considerações, é proposto nesse trabalho um novo algoritmo de solução para otimização da rede coletora de média tensão de parques eólicos, englobando a determinação da topologia de conexão entre os aerogeradores e subestações e o dimensionamento dos condutores, baseado na utilização de um algoritmo genético modificado como método de otimização. Objetiva-se com esse método minimizar os custos com a aquisição de alguns equipamentos e com as perdas de energia ao longo de um horizonte de planejamento. O método proposto foi testado em parques eólicos fictícios e os resultados obtidos comprovam que o modelo elaborado pode ser utilizado para projetar uma arquitetura otimizada da rede de distribuição interna de parques eólicos.
Among the various sources of renewable energy, wind energy stands out as one of the most promising. Amid the energy crisis scenario in many countries, the demand growth, greater environmental awareness and greater demand for energy quality on the part of modern societies, wind energy has gained economic and strategic importance. In Brazil, wind projects are contracted by means of auctions through which are declared winners those projects that offer the lowest price for energy generated. This current model is responsible for increase competition and consequently instigate the search for optimization of the proposals. Considering this aspect, it is of great interest the development of computational tools to assist professionals to develop technical and economically viable projects in the planning stage, and preferably optimized. Wind farms are basically composed of wind turbines, transformers responsible for raise the output voltage of the turbines for adequate levels of distribution, medium voltage cables and substations. The construction of the medium voltage collector network (internal network), responsible for the interconnection of all wind turbines and substations, constitutes a considerable share of the overall costs, which has motivated many researchers to publish works that aim to find the best grid topology of the electrical network that, at the same time, minimizes costs and respects the technical criteria established, such as: radial configuration, connectivity, voltage variation in bus, current conduction maximum through the cable (overhead in the branches), among others. In view of these considerations, it is proposed in this paper a new solution algorithm to optimization of the medium voltage collector network of wind farms, comprising the determination of topology of connection between the turbines and substations and the sizing of conductors, based on the use of a modified genetic algorithm as optimization method. The objective of this methodology is to minimize the costs of acquisition of some equipment and energy losses over a planning horizon. The proposed method was tested on fictitious wind farms and the results show that the model developed can be used to design the optimized architecture of internal distribution network of wind farms.

Bei der Zustandsbewertung von Kabeln steht derzeit das Mittelspannungsnetz im Fokus der Betrachtungen. Das Mittelspannungsnetz verbindet das Hochspannungsnetz mit dem Niederspannungsnetz und nimmt damit eine besondere Bedeutung ein. Störungen in diesem Netz wirken sich direkt als Versorgungsunterbrechung auf den Letztverbraucher aus. Rund 80 bis 85 % der Versorgungsunterbrechungen resultieren aus Problemen im Mittelspannungsnetz, sodass dortige Aktivitäten den größten Hebel bei der Steigerung der Versorgungsqualität entwickeln. Mittels Zustandsbewertung von Kabeln können verdeckte Fehler aufgedeckt oder deren Alterungszustand bestimmt werden. Nicht jeder diagnostizierte Fehler führt unmittelbar zum Ausfall. Er beschleunigt jedoch die Alterung, die letztendlich zum Ausfall führt. Die Arbeit beschäftigt sich mit der Identifizierung von Fehlern in Mittelspannungskabelmuffen im Zusammenhang mit der Alterung, um die Restlebensdauer auszunutzen und dem Ausfall zuvorzukommen.
By evaluating the status of cables, hidden errors can be detected or their aging condition can be determined. Not every diagnosed fault leads directly to failure. However, it accelerates aging, which ultimately leads to failure. The work deals with the identification of faults in medium-voltage cable joints in connection with aging in order to exploit the remaining life and to prevent the failure.

Theses focuses on the evaluation of the possible means of active and reactive power control of generating units connected to medium voltage. First part summarizes analysis of Czech Republic medium voltage distribution grid. It summarizes means of autonomous and dispatcher control of generating units with respect to European Comission directive RfG, standard ČSN EN 50549-2 and national implementation PPDS. Following parts provide description of generating unit and distribution grid models used for simulation in PSCAD. Last part focuses on evaluation of results obtained via simulating steady-state scenarios as well as continuous simulation.

Being part of a larger research project named “Distribution 2020”, the focus of this work has been on increasing the automation of the fault handling in distribution networks, taking into consideration the increasing number of distributed generation (DG) units. The main goal of this work has been to investigate, and further develop methods for locating short circuit faults in distribution networks, with possible presence of DG-units. Also, the developed methods should be simple, and the use of measurements communicated from other locations than the substation should be kept at a minimum. Finally, the fault localization methods should be applicable for a general network. The development of such general methods is meant to be a step towards a more automated fault handling in distribution networks, leading to increased network reliability and reduced outage costs. Fault data have been generated through simulations in the transient electromagnetic program PSCAD, where a simple model of a medium voltage (MV) distribution network was developed. Short circuit data from a real network was not available for this work. A distribution network may have various appearances, as the total length, number of branches, loading, short circuit capacity and other parameters may vary greatly, and generalizing the characteristics for a typical distribution network is not possible. The model parameters are chosen based on real network data, but the model is typically simplified compared to a real network. This work has focused on short circuit faults. Fault simulations have been performed for a feeder without DG, with one DG- and with three DG-units. The impacts of various parameters on the distance estimate obtained by use of conventional distance relays have been investigated. Focus in the investigation was to find which parameters that impact most on the accuracy, and on quantifying the errors in the estimates. It is shown how load and DG introduce substantial errors in the distance estimates from traditional distance relays, and that there is a need for methods to compensate for these impacts in order to obtain a fault localization of sufficient accuracy. Two methods for compensation of the impact from the load and DG-unit(s) on the distance estimates are presented. Both methods make use of pre-fault measurements from the DG-unit together with pre-fault substation measurements, and make rough estimations of the pre-fault load distribution on the feeder. In method 1 the required DG-quantities during fault are estimated, while in method 2 the DG voltage- and current- magnitude and the power factor angle are available from measurements. Requiring only magnitude values from the DG allows for simple communication solutions. In both method 1 and 2 a simple lumped feeder model is utilized for analytical estimation of unknown quantities. This includes estimation of the DG voltage phasor angle referred to the substation voltage. The estimated DG currents during fault in method 1 are quite accurate, especially for twophase short circuits, as seen in Ch. 6.2.5. For three-phase short circuits the estimated currents are generally a bit higher than the simulated. This results in overcompensation of the impact due to the DG in the distance-to-fault estimation. Despite of the overcompensation, the accuracy is improved with compensation 1 in most cases. The improvement is however dependent on the DG location. With a three-phase short circuit at the end of a 30 km long feeder, the largest improvement is seen when the DG is located close to (5 km) the substation, with a reduction of the error from +7.8 km to -1 km. The lowest accuracy of the compensated estimate is obtained when the DG is located at the middle of the feeder. The error is then -1.9 km, which still is an improvement compared to worst case without compensation. The estimates obtained at high load are only slightly more accurate than for low load, despite of the larger difference without compensation. If the DG location is fixed and the fault location is varied, the accuracy of the compensated estimate is decreasing as the fault is moved away from the substation, and the lowest accuracy is obtained when the fault is at the feeder-end. Generally, compensation method 1 results in larger improvement of the accuracy for twophase short circuits, than for three-phase. In method 2, measurements of the DG current- and voltage- magnitudes and the power factor angle during fault are utilized, and very accurate distance estimates are obtained for all cases (largest error with compensation 2 for the shown cases is 0.7 km). The DG-voltage phasor angle relative to the substation voltage is estimated from the lumped feeder model, like in the pre-fault state. The distance estimates are very accurate for all fault cases, so to have measurements from the DG during fault is very advantageous. If the DG voltage magnitude is available during fault it can be utilized for finding the correct faulted branch if there is more than one candidate location. A method where the corresponding DG voltage is estimated for each possible fault location has been suggested. For the example feeder the smallest difference between the estimated and simulated voltage magnitudes corresponded to the correct fault location in all cases. Measurements from the DG-unit during fault result in both more accurate distance estimates and can be used to decide the correct faulted branch, and to have such measurements is therefore very beneficial.

The theoretical part of this thesis deals with distribution networks in terms of distribution according to different criteria, describes the main elements of electric distribution networks and their qualities. The following describes the methods of calculating the steady state of electrical networks. These methods are nowadays used as basics for computer programs. In the penultimate chapter of the theoretical part are summarized the principles for the development of present networks and construction of new electrical networks. The aim of practical part of the thesis is to assess the current condition of the network 22 kV in the city of Brno and assess the condition after installation of 110/22 kV transformation in Brno-Sever switching substation. After evaluating the results of steady state electrical network and identifying certain problems is the following aim a proposal of solving problems that emerged in the network. The result should be operational, functional and reliable electric distribution network. This thesis used to calculate the steady state electrical networks by software PAS DAISY Off-Line Bizon V4.

Soft Open Points (SOPs) are power electronic devices installed in place of normally-open points in electrical power distribution networks. They are able to provide active power flow control, reactive power compensation and voltage regulation under normal network operating conditions, as well as fast fault isolation and post-fault supply restoration under abnormal conditions. The use of SOPs for the operation of medium voltage (MV) distribution networks was investigated. Three aspects were studied, which include the control of an SOP, benefit analysis of using SOPs and distribution network voltage control with SOPs. Two control modes for the operation of an SOP, which is based on back-to-back voltage source converters (VSCs), were developed. The operating principle and performance of the back-to-back VSC based SOP under both normal and abnormal network operating conditions were analysed. It was found that during the change of network operating conditions, smooth transitions between the two controls modes were needed. Using soft cold load pickup and voltage synchronization processes can achieve the smooth mode transitions. A steady state analysis framework to quantify the operational benefits of a MV distribution network with SOPs was developed, which considers feeder load balancing, power loss minimization and voltage profile improvement. The framework also considered traditional network reconfiguration and the combination of both SOP control and network reconfiguration to quantify the benefits. It was found that in the case study using only one SOP can achieve a similar improvement in network operation compared to the case of using network reconfiguration with all branches equipped with remotely controlled switches. The combination of both SOP control and network reconfiguration can achieve the optimal network operation.

Soft DC Links are power electronic converters enabling the control of power flow between distribution feeders or networks. This thesis considers the use of Soft DC Links in Medium Voltage (MV) distribution networks to improve network operation while facilitating the integration of distributed generators (DGs). Soft DC Links include Soft Open Points (SOPs) and Medium Voltage Direct Current (MVDC) links. An SOP can be installed to replace mechanical switchgear in a network, providing controllable active power exchange between connected feeders, as well as reactive power compensation at each interface terminal. The deployment of an MVDC link enables power and voltage controls over a wider area, and facilitates the effective use of available capacity between adjacent networks. The benefits of using SOP and MVDC link in MV distribution networks were investigated. A multi-objective optimisation framework was proposed to quantify the operational benefits of a distribution network with an SOP. An optimisation method integrating both global and local search techniques was developed to determine the set-points of an SOP. It was found that an SOP can improve network operation along multiple criteria and facilitate the integration capacity of DGs. A Grid Transformer-based control method of an MVDC link was proposed, which requires only measurements at the grid transformers to determine the operation of an MVDC link. Control strategies considering different objectives were developed. The proposed control method is used in the ANGLE-DC project, which aims to trial the first MVDC link in Europe by converting an existing AC circuit to DC operation. It was found that an MVDC link can significantly increase the network hosting capacity for DG connections while reducing network losses compared to an AC line. An impact quantification of Soft DC Links was carried out on statistically-similar distribution networks, which refer to a set of networks with similar but different topological and electrical properties. A model was developed to determine the optimal allocation of Soft DC Links. It was found that a Soft DC Link can reduce the network annual cost under a wide range of DG penetration conditions. The statistical analysis provides distribution network planners with more robust decisions on the implementation of Soft DC Links.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2013
Harmonic voltages and currents in distribution networks are on the increase in recent times due to the introduction of a proliferation of electronic controlled devices such as variable speed drives. These non-linear devices improve efficiency but distort the supply waveforms. To address the harmonic issues, harmonic filters are used to mitigate distortion levels and prevent damage. These harmonic filters are commonly found at medium voltage levels in power systems. The problem is that knowledge from the design to commissioning stages of these medium voltage harmonic filters are neither well developed nor adequately documented. The aim of this research is to investigate and expound upon the process whilst taking into account all the factors involved throughout the process from bringing such a filter into operation in the real world. Medium voltage harmonic filters are usually the open rack type found in outdoor installations. Capacitors and reactors are the main components used in the construction of such harmonic filters and in some instances resistors are also used. The physical size and spacing of such components determines the construction layout area and how this is done in practice warrants being researched and explained in this thesis. In order to make these factors explicit, a methodology is developed from design, to installation and commissioning and is applied to two networks which are used to prove that the developed methodology is applicable for the different types of harmonic filters designed. The network voltage levels are also different, thus implying that the components will have different design factors. The final arrangements of the harmonic filters are later drawn and shown in three-dimension (3D) as per dimensions. The 3D figures are a further contribution as the design is taken from theory and is ultimately implemented into an installation and construction layout for erection at site. Interviews and surveys are conducted with specialists in industry dealing with harmonic filter applications and the results are analysed as part of implementation of the developed methodology. The design, installation and construction phases are documented and shown to be effective in application and the work disclosed in this thesis will help newcomers to this specialised field and is recommended for use in industry.

Distribution system plays a significant role in the overall electrical power system due to its impact on electricity costs, reliability as well as security of supplied energy. Optimal development planning of modern distribution system is mainly required to satisfy continuous change in customer demands and generations in a cost-effective manner, utilizing the available smart solutions. All these aspects need to be addressed in modern distribution planning methodology that can be applied today in real-life. Review has shown that there are no distributions planning models that adequately model security of supply of radially operated networks. Moreover, the optimal development planning models still do not consider multiple operating regimes, which has become a necessity due to connection of low carbon technologies. Numerous techniques published on this subject tend to ignore the regulations and planning standards that must be complied during system development, resulting in methodology that is not in-tuned with business practices. Furthermore, a comprehensive model that integrates all major components of today’s real-life distribution planning is still lacking, even though many of them have been addressed individually. In this thesis, integrated planning methodology for development of distribution system is proposed, incorporating utility practices in the UK. The overall methodology built on two independent stages, investment stage and operation stage. The operation stage is further cast into two sub-stages, quality of supply planning and minimization of operation costs planning. The overall planning methodology incorporates the novel probabilistic decision tree concept for distribution system planning to consider probable network uncertainties. The first model which is the investment stage determines the new construction and reinforcement of circuits and switchgear, along with circuit decommissioning. Multiple operating regimes due to fluctuation in generation and load profiles are considered, in addition to explicit modelling of N-1 security constraint according to P2/6 planning standards. The quality of supply planning determines the allocation of switchgear and its automation to maximise the reliability benefits from the regulatory incentive regime. Finally, the operation model determines the optimal network configuration that minimises the total operation costs of distribution system. The final outputs are list of cables and switchgear for construction, reinforcement, and decommission, benefits harvested due to quality of supply investments on switchgear, optimal network running arrangement, etc. These studies have proven to be important in formulating effective strategies for development of distribution system, in compliance to the planning standards and resulted in higher network operation capabilities.

The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.

Energy usage evaluation and condition monitoring for electric machines are important in industry for overall energy savings. Traditionally these functions are realized only for large motors in wired systems formed by communication cables and various types of sensors. The unique characteristics of the wireless sensor networks (WSN) make them the ideal wireless structure for low-cost energy management in industrial plants. This work focuses on developing nonintrusive motor-efficiency-estimation methods, which are essential in the wireless motor-energy-management systems in a WSN architecture that is capable of improving overall energy savings in U.S. industry. This work starts with an investigation of existing motor-efficiency-evaluation methods. Based on the findings, a general approach of developing nonintrusive efficiency-estimation methods is proposed, incorporating sensorless rotor-speed detection, stator-resistance estimation, and loss estimation techniques. Following this approach, two new methods are proposed for estimating the efficiencies of in-service induction motors, using air-gap torque estimation and a modified induction motor equivalent circuit, respectively. The experimental results show that both methods achieve accurate efficiency estimates within ¡À2-3% errors under normal load conditions, using only a few cycles of input voltages and currents. The analytical results obtained from error analysis agree well with the experimental results. Using the proposed efficiency-estimation methods, a closed-loop motor-energy-management scheme for industrial plants with a WSN architecture is proposed. Besides the energy-usage-evaluation algorithms, this scheme also incorporates various sensorless current-based motor-condition-monitoring algorithms. A uniform data interface is defined to seamlessly integrate these energy-evaluation and condition-monitoring algorithms. Prototype wireless sensor devices are designed and implemented to satisfy the specific needs of motor energy management. A WSN test bed is implemented. The applicability of the proposed scheme is validated from the experimental results using multiple motors with different physical configurations under various load conditions. To demonstrate the validity of the measured and estimated motor efficiencies in the experiments presented in this work, an in-depth error analysis on motor efficiency measurement and estimation is conducted, using maximum error estimation, worst-case error estimation, and realistic error estimation techniques. The conclusions, contributions, and recommendations are summarized at the end.

The purpose of this thesis is to introduce readers with design of a surge arresters in four different categories. In the first part of this thesis is described theory of overvoltage, surge arresters and testing. The second part of this thesis is focused on design of surge arresters to protect from overvoltage due switching capacitive loads. The thesis continued with design of surge arresters in medium voltage network. The next part is design of surge arresters to protect from overvoltage due switching inductive loads. The next point is protective distance of surge arresters in different lighting overvoltages. In the conclusion of this thesis is the appreciation of whole problems about surge arresters.

Les procédés bipolaires semi-conducteurs complémentaires à oxyde de métal (BiCMOS) peuvent être considérés comme étant la solution la plus généralepour les produits RF car ils combinent la fabrication sophistiquée du CMOSavec la vitesse et les capacités de conduction des transistors bipolaires silicium germanium(SiGe) à hétérojonction (HBT). Les HBTs, réciproquement, sontles principaux concurrents pour combler partiellement l'écart de térahertzqui décrit la plage dans laquelle les fréquences générées par les transistors etles lasers ne se chevauchent pas (environ 0.3 THz à 30 THz). A_n d'évaluerles capacités de ces dispositifs futurs, une méthodologie de prévision fiable estsouhaitable. L'utilisation d'un ensemble hétérogène d'outils et de méthodes desimulations permet d'atteindre successivement cet objectif et est avantageusepour la résolution des problèmes. Plusieurs domaines scientifiques sont combinés, tel que la technologie de conception assistée par ordinateur (TCAO),la modélisation compacte et l'extraction des paramètres.Afin de créer une base pour l'environnement de simulation et d'améliorerla confirmabilité pour les lecteurs, les modèles de matériaux utilisés pour lesapproches hydrodynamiques et de diffusion par conduction sont introduits dèsle début de la thèse. Les modèles physiques sont principalement fondés surdes données de la littérature basées sur simulations Monte Carlo (MC) ou dessimulations déterministes de l'équation de transport de Boltzmann (BTE).Néanmoins, le module de TCAO doit être aussi étalonné sur les données demesure pour une prévision fiable des performances des HBTs. L'approchecorrespondante d'étalonnage est basée sur les mesures d'une technologie depointe de HBT SiGe pour laquelle un ensemble de paramètres spécifiques àla technologie du modèle compact HICUM/L2 est extrait pour les versionsdu transistor à haute vitesse, moyenne et haute tension. En s'aidant de cesrésultats, les caractéristiques du transistor unidimensionnel qui sont généréesservent de référence pour le profil de dopage et l'étalonnage du modèle. Enélaborant des comparaisons entre les données de références basées sur les mesureset les simulations, la thèse fait progresser l'état actuel des prévisionsbasées sur la technologie CAO et démontre la faisabilité de l'approche.Enfin, une technologie future de 28nm performante est prédite en appliquantla méthodologie hétérogène. Sur la base des résultats de TCAO, leslimites de la technologie sont soulignées
Bipolar complementary metal-oxide-semiconductor (BiCMOS) processescan be considered as the most general solution for RF products, as theycombine the mature manufacturing tools of CMOS with the speed and drivecapabilities of silicon-germanium (SiGe) heterojunction bipolar transistors(HBTs). HBTs in turn are major contenders for partially filling the terahertzgap, which describes the range in which the frequencies generated bytransistors and lasers do not overlap (approximately 0.3THz to 30 THz). Toevaluate the capabilities of such future devices, a reliable prediction methodologyis desirable. Using a heterogeneous set of simulation tools and approachesallows to achieve this goal successively and is beneficial for troubleshooting.Various scientific fields are combined, such as technology computer-aided design(TCAD), compact modeling and parameter extraction.To create a foundation for the simulation environment and to ensure reproducibility,the used material models of the hydrodynamic and drift-diffusionapproaches are introduced in the beginning of this thesis. The physical modelsare mainly based on literature data of Monte Carlo (MC) or deterministicsimulations of the Boltzmann transport equation (BTE). However, the TCADdeck must be calibrated on measurement data too for a reliable performanceprediction of HBTs. The corresponding calibration approach is based onmeasurements of an advanced SiGe HBT technology for which a technology specific parameter set of the HICUM/L2 compact model is extracted for thehigh-speed, medium-voltage and high-voltage transistor versions. With thehelp of the results, one-dimensional transistor characteristics are generatedthat serve as reference for the doping profile and model calibration. By performingelaborate comparisons between measurement-based reference dataand simulations, the thesis advances the state-of-the-art of TCAD-based predictionsand proofs the feasibility of the approach.Finally, the performance of a future technology in 28nm is predicted byapplying the heterogeneous methodology. On the basis of the TCAD results,bottlenecks of the technology are identified
Bipolare komplementäre Metall-Oxid-Halbleiter (BiCMOS) Prozesse bietenhervorragende Rahmenbedingungen um Hochfrequenzanwendungen zurealisieren, da sie die fortschrittliche Fertigungstechnik von CMOS mit derGeschwindigkeit und Treiberleistung von Silizium-Germanium (SiGe) Heterostruktur-Bipolartransistoren (HBTs) verknüpfen. Zudem sind HBTs bedeutendeWettbewerber für die teilweise Überbrückung der Terahertz-Lücke, derFrequenzbereich zwischen Transistoren (< 0.3 THz) und Lasern (> 30 THz).Um die Leistungsfähigkeit solcher zukünftigen Bauelemente zu bewerten, isteine zuverlässige Methodologie zur Vorhersage notwendig. Die Verwendungeiner heterogenen Zusammenstellung von Simulationstools und Lösungsansätzenerlaubt es dieses Ziel schrittweise zu erreichen und erleichtert die Fehler-_ndung. Verschiedene wissenschaftliche Bereiche werden kombiniert, wie zumBeispiel der rechnergestützte Entwurf für Technologie (TCAD), die Kompaktmodellierungund Parameterextraktion.Die verwendeten Modelle des hydrodynamischen Simulationsansatzes werdenzu Beginn der Arbeit vorgestellt, um die Simulationseinstellung zu erläuternund somit die Nachvollziehbarkeit für den Leser zu verbessern. Die physikalischenModelle basieren hauptsächlich auf Literaturdaten von Monte Carlo(MC) oder deterministischen Simulationen der Boltzmann-Transportgleichung(BTE). Für eine zuverlässige Vorhersage der Eigenschaften von HBTs muss dieTCAD Kon_guration jedoch zusätzlich auf der Grundlage von Messdaten kalibriertwerden. Der zugehörige Ansatz zur Kalibrierung beruht auf Messungeneiner fortschrittlichen SiGe HBT Technologie, für welche ein technologiespezifischer HICUM/L2 Parametersatz für die high-speed, medium-voltage undhigh-voltage Transistoren extrahiert wird. Mit diesen Ergebnissen werden eindimensionaleTransistorcharakteristiken generiert, die als Referenzdaten fürdie Kalibrierung von Dotierungspro_len und physikalischer Modelle genutztwerden. Der ausführliche Vergleich dieser Referenz- und Messdaten mit Simulationengeht über den Stand der Technik TCAD-basierender Vorhersagenhinaus und weist die Machbarkeit des heterogenen Ansatzes nach.Schlieÿlich wird die Leistungsfähigkeit einer zukünftigen Technologie in28nm unter Anwendung der heterogenen Methodik vorhergesagt. Anhand derTCAD Ergebnisse wird auf Engpässe der Technologie hingewiesen

Student Number : 9811492X - MSc dissertation - School of Electrical and Information Engineering - Faculty of Engineering and the Built Environment
This dissertation discusses the development of an ATP model of a network to aid measurement techniques in a harmonic evaluation. A theoretical back- ground discussion of various pieces of equipment and their signi#12;cance to har- monics is included. National Electricity Regulator (NRS 048) standards are discussed with refer- ence to performing a basic investigation and short comings. A test study was performed on the Brandspruit Mine in Secunda. ATP models are developed for equipment relevant to the test case, these in- clude AC{AC converters, AC{DC converters, three phase transformers and cables. Finally the measured test case is compared to simulation results and conclusions drawn.

Η παρούσα διπλωματική πραγματεύεται την μελέτη της ηλεκτροδότησης ενός αντλιοστασίου, καθώς και του ιδιωτικού Υ/Σ που θα έχει ο καταναλωτής από το δίκτυο ΜΤ της ΔΕΗ. Στα πρώτα κεφάλαια γίνεται μια θεωρητική προσέγγιση του προβλήματος. Ειδικότερα, παρατίθενται οι τύποι παροχής των ιδιωτικών Υ/Σ, ενώ αναλύονται τα μέσα ζεύξης και προστασίας της ΜΤ. Στη συνέχεια παρουσιάζονται τα είδη γείωσης των ιδιωτικών Υ/Σ ΜΤ-ΧΤ καθώς και οι κατηγορίες καλωδίων για την ΧΤ και την ΜΤ και τρόποι εγκατάστασης τόσο των καλωδίων ΧΤ όσο και αυτών της ΜΤ. Ακολουθεί μια περιγραφή των Μ/Τ ισχύων που χρησιμοποιούνται για την ζεύξη με το δίκτυο ΜΤ και τα μέσα προστασίας των Μ/Σ . Ταυτόχρονα αναπτύσσονται τα μέσα ζεύξης - απόζευξης και προστασίας XT αλλά και ο τρόπος λειτουργίας τους με σκοπό την αντιμετώπιση των ρευμάτων βραχυκύκλωσης που ενδεχομένως εμφανίζονται σε μια ηλεκτρική εγκατάσταση. Τέλος περιγράφονται οι πίνακες ΜΤ και ΧΤ μέσα στους οποίους τοποθετούνται τα μέσα προστασίας και ζεύξης - απόζευξης ΜΤ και ΧΤ του Υ/Σ, ενώ παράλληλα επισημαίνεται η αναγκαιότητα και τα πλεονεκτήματα της αντιστάθμισης της άεργου ισχύος και οι τρόποι επίτευξής της. Γίνεται ακόμη ιδιαίτερη αναφορά στην συντήρηση ενός Υ/Σ και στην αναγκαιότητα της. Στο 11ο κεφάλαιο έχουμε την μελέτη ενός αντλιοστασίου και ένα ένα τα βήματα που ακολουθούμε για την ολοκλήρωση της μελέτης από την επιλογή των κινητήρων , την διατομή των καλωδίων ΜΤ και ΧΤ , τις προστασίες τόσο στην ΜΤ και την ΧΤ όσο και στους κινητήρες , την επιλογή του Μ/Σ έως τον υπολογισμό των ζυγών ,τους πίνακες ΜΤ και ΧΤ και την αντιστάθμιση της άεργου ισχύος.
This thesis deals with the study of power supplying of a pump-station, as well as of a private Substation that the consumer would have, from the Medium Voltage network of DEH. In the early chapters is a theoretical approach to the problem. In particular, lists the types of provision of private M/L Voltage Substation, while analysing the connection and protection structures of MV. Then presents the types of groundings in private M/L Voltage Substations and also the categories of cables for LV and MV and ways of installation. Follows a description of power transformers used for coupling with the MV network and the protection of them. At the same time develop the means decoupling – coupling and protections at LV and their operation for dealing with potentially short-circuit currents appear in an electrical installation. Finally describes the MV and LV fields within are placed the protectιons of LV and MV coupling of the M/L Substation, while pointing out the necessity and advantages of counterbalancing the reactive power and ways of achieving it. Is a special reference to maintenance of M/L Substation and the need of it. In the 11th chapter we study a pump-station and one by one the steps to follow to complete the study from the choice of engines, the cross-section of cables LV and MV, protections both in MV, LV and engines, and the selection of suited power transformer till the calculations of bars, fields of LV and MV and counterbalancing the reactive power.

South African medium voltage underground electrical networks consist mainly of cables of paper insulated lead covered construction. This construction is still the standard used for most utilities in South Africa. While the in-service performance history of these cables has been excellent, global manufacture of this cable type is decreasing. Internationally, the use of polymeric cables is increasing, resulting in the security of the supply chain for paper cable becoming an increasingly important issue. The most widely used polymeric construction is cross-linked polyethylene. Modern distribution switchgear, which is increasingly used in South Africa, is designed for the newer polymeric technology as this enables more compact construction and reduced equipment footprint. The reduced clearances present installation and operational issues when using modern switchgear with paper insulated cables. Although a comprehensive literature review was conducted, not much academic work has been done on the process of migrating from one cable platform to another. Manufacturer data, academic reference sources, industry experts and software modelling tools are used to demonstrate that the use of polymeric technology is viable for South African utilities. This dissertation focuses on the difference between paper and polymeric technologies, and explores the advantages and disadvantages of each. Integration issues are examined along with the methods used to overcome the challenges of hybrid or mixed dielectric networks. Economic comparisons between paper and polymeric cables with respect to purchase and operating costs (including the cost of losses) as well as steady state, cyclic, distribution and emergency current ratings are made. The dissertation concludes that it makes economic and engineering sense for users of paper cable in South Africa to change to polymeric technology, taking the recommendations given into consideration in order to choose an optimised cable design and gain maximum benefit from the change.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.