Kraven på ett driftsäkert elnät ökar hela tiden i takt med att elanvändning blir allt viktigare i dagens samhälle. Luftledningar byts ut med markkabel och möjlighet till reservmatningar samt bra elkvalitet är av hög prioritering. Skicket på elnätets utrustning försämras med åren och kommer med tiden behöva bytas ut. Med uppdrag från Uddevalla Energi AB har siffror tagits fram berörande spänningsfall, kapacitiv jordfelsström och belastningar vid normaldrift och reservmatning, samt ålder och typ på kablar i Uddevalla citys mellanspänningsnät. Den här rapporten presenterar dessa resultat och ger några förslag på ändringar om så krävs. Även en del om planerade framtida utbyggnationer tas upp och hur dessa påverkar nätet. För att få fram resultaten används Uddevalla Energis program för nätberäkning, "DpPower". Beräkningarna visade att vid normaldrift var alla värden godkända enligt tumregler som Uddevalla Energi följer. Vid reservmatning däremot var vissa linjer överbelastade, analysen visar dock tillgängliga lösningar. Ålder och status på kablar i nätet varierar stort vilket gör det svårt att specificera hur ombyggnationer ska ske. Hänsyn bör istället tas till överbelastningar. / The demand of reliable power distribution is increasing as the usage of power is increasing in the society of today. Overhead lines are replaced by underground cables, availability to reserve power supply and power quality is of high priority. The condition of the equipment deteriorates over the years and will eventually have to be replaced. By request from Uddevalla Energi, values have been provided concerning voltage drop, capacitive ground fault current and loads during normal operation and standby power supply. The types and ages of cables in Uddevalla City’s high-voltage network has also been looked at. This report presents these results and gives some suggestions for modifications if required. Planned future deployments are looked over and how these may affect the network. To obtain these results the network calculating program "DpPower" was used. The calculations presented shows that in normal operation all values are approved within the company standards that Uddevalla Energi follows. For the reserve supply however, some lines are overloaded. The analysis shows possible solutions for these issues. Age and status of cables in the network varies widely, making it difficult to specify how redevelopments should take place. Instead the overloads should be given more consideration.

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 2014 / In recent times, renewable energy-based distributed generation (DG) has captivated the industrial sector and on a global scale this has become a leading research area. Distributed generation using wind, solar energy or biomass as a source of energy can produce electricity on a small scale. Therefore, there is a strong focus on using renewable energy as a safe alternative source of energy, especially because it can in future play a dominant role in the world’s energy production and help to tackle the increase of global warming caused by fossil energy. However, a major problem facing renewable energies is that they are highly dependent on weather conditions. Since the power generated by DG, as well as consumption, depends on the weather conditions, irregularity of production and consumption leads to frequency and voltage fluctuations, and it can become difficult to determine and monitor consumer usage at any given time. Distributed generation can then be subjected to discrepancies in consumer usage and this can lead to severe overloading. As a result, microgrids powered by DG, operating in a single, stand-alone controllable system mode, face new challenges in terms of balancing a cluster of loads. Balancing a cluster of loads by making sure at all times that the entire system operates without overloading, is an essential requirement for the proper operation of a power system. The microgrid load considered in this project is the sum of sensitive and non-sensitive loads, respectively 5 kW and 100 kW, which constitute load requirement of one village; this total load required by a number of villages is called a cluster load. Depending on the input power generated by a DG-based photovoltaic (PV) system, these loads can be controlled using a logic control switch (LCS). When the power produced is less than the minimum load required by a component of a cluster, overloading occurs. The purpose of using an LCS is to ensure that a stable system is maintained under various loads and resource conditions. An LCS is used to continuously monitor and adjust load through circuit breakers. It is a good alternative to load balancing for a cluster of villages in rural area where a microgrid is operating in stand-alone mode. The focus of this research is to design a photovoltaic system with a maximum capacity of 1 MW providing power to a cluster of rural villages, and operating in stand-alone mode, and then to apply different control techniques (droop control, dq0 reference frame + proportional integral (PI) controller, and PI controller alone) at the inverter terminal of the PV system, in order to evaluate the stability of the output voltage. Another goal of the research is to develop an energy management system (EMS) algorithm to support the PV system in reducing loads. Therefore, a iii stable system under various load and resource conditions, as well as suitable control mechanisms are required to model a PV system. There is a need for the modelling of a PV array using a physical modelling block in MATLAB (SIMULINK) software. The state flow provided by SIMULINK is used in this project to develop an algorithm for load balancing. The state flow gives possibilities of modelling complex algorithms by combining graphical and tabular representations to create sequential decision logic, derived from state transition diagrams and tables, flow charts and truth tables. Furthermore, the design of a microgrid using photovoltaic DG and an energy management system, has been developed. The present work mainly consists of a stand-alone microgrid operation, where the power generated must be equal to the load power. In addition, different control methods, consisting of a dq0 reference frame + PI controller, are analysed at the invertor terminal. Subsequently an LCS algorithm is developed; this is required to maintain the system within certain limits and prevents overloading. LCS algorithms are based on a flowchart and allow switching automatically selected loads, depending on the power (solar radiation) available. In addition, a flow chart provides an easy way of using a graphical transition state and state chart to establish a set of rules for the system. The simulation results show that both droop control and a dq0 reference frame + PI controller are much better than a PI controller alone; these results also compared well with similar studies found in the literature. Also, these results are further improved with an EMS in order to maintain the output voltage of the microgrid, by switching on and off certain loads depending on the input power. The modelling of the microgrid using DG, based on photovoltaic systems with a maximum capacity of 1 MW, supports and improves the PV system by reducing loads. Moreover, droop control, and dq0 transformation + PI control present a better result than PI controller alone.

Thesis (MTech (Quality (Engineering)))--Cape Peninsula University of Technology, 2016. / The research study establishes the maturity level of the outage process of the Outage Management Department at Eskom. The outage process started in 2012 to contribute to the effective planning and execution of outages. The successful completion of outages depends on effective planning and execution of an outage. At the time of the research study, poor outage performance at Eskom’s power stations contributed to load shedding of electricity in South Africa. The research problem statement reads as follows: The absence of an outage process maturity indicator diminishes the ability of the Outage Management Department (OMD) to comprehend the current process maturity level. The research question: Will the Outage Management Department be able to identify improvement opportunities if the maturity level of the outage process is established? iv The key research objectives are: • To consider how process maturity enables improvement. • To identify critical elements in an outage process. • To determine what is included in outage planning, control and improvement. • To identify a suitable process maturity model. • To identify a measurement instrument to determine the maturity level of Eskom’s outage process The research study uses a descriptive research design and applies the survey research method. Greener and Martelli’s (2015: Online) Business Research Process (Sources: Greener & Martelli, 2015: Online) is used together with Farooq’s Research Steps for Survey Research (2015, Online). The survey questionnaire adopted from Smith’s Maintenance Planning and Scheduling Maturity Matrix (2013: Online) was used to develop the survey questionnaire. The author developed the Outage Management Maturity Framework by combining Business Process Management Maturity model and a Maintenance Planning and Scheduling Maturity Matrix. The research finding is that a process maturity model can determine the maturity level of the outage process and is useful as a process improvement tool. The research findings rank the maturity level of the outage process at Level 2, Experimenting.

Thesis (MTech (Quality))--Cape Peninsula University of Technology, 2017. / The research study establishes the maturity level of the outage process of the Outage Management Department at Eskom. The outage process started in 2012 to contribute to the effective planning and execution of outages. The successful completion of outages depends on effective planning and execution of an outage. At the time of the research study, poor outage performance at Eskom’s power stations contributed to load shedding of electricity in South Africa. The research problem statement reads as follows: The absence of an outage process maturity indicator diminishes the ability of the Outage Management Department (OMD) to comprehend the current process maturity level. The research question: Will the Outage Management Department be able to identify improvement opportunities if the maturity level of the outage process is established? The key research objectives are: • To consider how process maturity enables improvement. • To identify critical elements in an outage process. • To determine what is included in outage planning, control and improvement. • To identify a suitable process maturity model. • To identify a measurement instrument to determine the maturity level of Eskom’s outage process The research study uses a descriptive research design and applies the survey research method. Greener and Martelli’s (2015: Online) Business Research Process (Sources: Greener & Martelli, 2015: Online) is used together with Farooq’s Research Steps for Survey Research (2015, Online). The survey questionnaire adopted from Smith’s Maintenance Planning and Scheduling Maturity Matrix (2013: Online) was used to develop the survey questionnaire. The author developed the Outage Management Maturity Framework by combining Business Process Management Maturity model and a Maintenance Planning and Scheduling Maturity Matrix. The research finding is that a process maturity model can determine the maturity level of the outage process and is useful as a process improvement tool. The research findings rank the maturity level of the outage process at Level 2, Experimenting.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / This dissertation represents the design and development of a load management system for fixed appliances in a safe direct current (DC) Reconstruction and Development Programme (RDP) house. A combination of valley filling, load shifting and peak clipping load management techniques were employed to assist in reducing the peaks observed in the RDP house load profile during peak hours. A DC RDP house laboratory model was developed. The study is based on the assumption that the normally 220 V alternative current (AC) grid is replaced by a 350 V DC grid. The assumption is thus that 350 V DC is available at the distribution box in the RDP house laboratory model. All theoretical work was based on a 350 V DC system, but due to the lack of a laboratory 350 V DC supply, all physical tests were conducted by making use of a 300 V DC supply which was available. Consequently all calculations were thus based on 300 V DC as well. The geyser was the main fixed appliance focused on since it contributes to a significant portion of the power used. An AC geyser was successfully modified in order to be used in the DC network. Safety of the system was considered in order to interrupt the power in case of overcurrent or to isolate the power. Electronic switches were also developed and implemented to ensure that the DC power could be safely switched on and off and that the low power DC was isolated from the high power DC. LabVIEW allowed all other appliances in the DC RDP house to be virtually represented so that a holistic view of the power use of the house could be represented. This also allowed the system to be successfully simulated before any physical work was conducted. The load management system was successfully implemented by making use of power line communication. This proved to be a cost effective means to apply the load management algorithm. The algorithm consisted mainly of power on / off instructions that were executed during peak and off-peak times. It follows the normal use of timers used in the AC system to help reduce demand. It was found that the load management system successfully reduced the demand during peak hours without compromising the basic needs of the user. The power line communication modem proved to be very reliable in implementing the load management algorithm.

Orientador: Jose Antenor Pomilio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T08:24:07Z (GMT). No. of bitstreams: 1 Ortenzi_Gustavo_M.pdf: 4885292 bytes, checksum: 8a23d8845eaad19c72fe6f84e13af963 (MD5) Previous issue date: 2009 / Resumo: Descreve-se neste trabalho o desenvolvimento de uma fonte de alimentação chaveada para utilização em eletrodomésticos, capaz de entregar três saídas com níveis de tensão e potência diferentes, com uma mínima troca de componentes entre as três versões. Na primeira parte do trabalho é apresentada a aplicação da fonte e suas necessidades, seguido das especificações e da escolha da topologia e do modo de operação. Dando continuidade no desenvolvimento do projeto da fonte, apresenta-se a metodologia de cálculo adotada para o dimensionamento dos componentes a serem utilizados. Uma vez com os componentes dimensionados, apresenta-se a seleção dos componentes visando a estratégia de escalabilidade. Finalizando o dimensionamento dos componentes, apresenta-se o esquemático da fonte de alimentação e os componentes que são modificados de acordo com a versão em questão. A seguir, apresentam-se os resultados obtidos dos testes de regulação cruzada das saídas, as principais formas de onda de corrente e tensão do conversor, o rendimento das três versões considerando diferentes tensões de entrada de rede e a resposta a transiente. Fechando os resultados práticos, apresentam-se os ensaios de desenvolvimento de EMC/EMI, mostrando os resultados iniciais, as modificações implementadas e as soluções adotadas. No último capítulo apresenta-se as conclusões e as perspectivas de continuidade de desenvolvimento deste trabalho. / Abstract: This work describes the development of a switch mode power supply to be used at home appliances, capable to deliver three outputs with voltage and power different levels, changing a minimum number of components between them. At the first part of the work is presented the application of the power supply and its needs, followed by the specifications and choose of the topology and the operation mode. Continuing the design of the power supply's project, it is presented the methodology adopted to calculate and select the components to be used. With the components selected, it is presented the components selection criteria looking the scalability strategy. Ending the component's calculation and selection, the power supply schematic and the components that change according to the used version are shown. After the design, experimental results of the output cross regulation, main waveforms of voltage and current, efficiency and transient response of the three versions considering different AC Mains voltages are shown. Closing the experimental results, the EMI/EMC tests are presented, presenting the preliminary results, followed by the adopted modifications and solutions. The last chapter presents the conclusions and the perspectives of new developments of this work. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientador: Jose Antenor Pomilio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-11T05:49:41Z (GMT). No. of bitstreams: 1 Sperandio_GiulianoSalomao_M.pdf: 1492429 bytes, checksum: f30c57d63ec881417a2d7f6ebaf926c2 (MD5) Previous issue date: 2007 / Resumo: O ozônio se apresenta como um excelente produto químico para ser usado em substituição ou em conjunto com o cloro para o tratamento de água. O ozônio é um potente bactericida e viricida e não deixa resíduos no meio ambiente. A produção deve ser local e requer apenas ar e eletricidade. Um método simples e eficaz para a produção de ozônio é através de microdescargas em barreiras dielétricas em oxigênio. A produção da microdescarga é feita numa célula onde é aplicada uma alta tensão, da ordem de quilovolts. A alta tensão é gerada através de um circuito eletrônico de alto rendimento e interage com a carga para produzir a alta tensão desejada. A fonte de alta tensão foi projetada para fazer o uso das não idealidades do conjunto formado pelo transformador de alta tensão associado a célula ozonizadora. O comportamento da carga permite que a potência de saída seja ajustada pela freqüência de trabalho. A potência de saída é uma variável que está associada com a produção de ozônio a qual pode ser ajustada. O controle da potência foi realizado por um microcontrolador que também incorpora funções de proteção e comando remoto. Os resultados obtidos pela implementação prática do circuito eletrônico corroboram o modelo e as simulações feitas. O circuito foi desenvolvido por uma demanda da indÚstria. A etapa de desenvolvimento do circuito em laboratório atingiu uma maturidade satisfatória para industrialização / Abstract: The ozone gas is a powerful oxidizing substance and it can be used for the treatment of water. It is known to be a potent bactericide and viricide and leaves no harmful residues to the environment. Ozone has to be produced on-site and requires only air and eletricity. An efficient way to produce ozone is through diclectric-barrier discharge in oxigen. An electronic high-efficiency circuit is used to generate the necessary high- voltage to make the electric discharge. The circuit was designed to use the resonance of the transformer plus the silent-discharge ozone-generator tube. The transformer non-idealities are usefull for allowing the converter operation in the resonance region, minimizing the commutation losses. The output power can be adjusted setting the switching frequency. The circuit works properly and the practical results match to the simulations. This converter was developed according to the specification of an industry and it is now going into commercial production / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Abstract Class A and class AB operational amplifiers are an essential part of a mixed- signal chip, where they are used as active filter sub-blocks, compensators, reference current generators and voltage buffers, to name just a few of many applications. For analog circuits such as operational amplifiers a mixed-signal chip is a very unfriendly operating environment, where the power supply is often corrupted by high current switching circuits. In addition, power supply voltages for analog blocks are shrinking, because of the deployment of new battery technologies and fine line length integrated circuit processes, which can reduce the amplifier dynamic range a problem requiring supply insensitive low voltage compatible amplifier topologies and other analog blocks. The aims of this thesis were to further develop the low voltage compatible class AB amplifier topologies published earlier by other authors, to improve their bandwidth efficiency by means of re-examining two- and three-stage amplifier compensation techniques and to find solutions for enhancing the high frequency power supply noise rejection performance of class A and class AB amplifiers without degrading their signal path stability. The class AB amplifier cores presented here improve the amplifier’s power supply noise insensitivity at high frequencies and increase bandwidth efficiency when compared to the commonly used two-stage Miller compensated amplifier, enabling the construction of better buffers and more power-efficient and reliable low voltage mixed signal chips.

D.Ing / It is every person’s social responsibility to ensure that electrical energy is used as efficiently as possible. This is as a result of the considerable fossil fuels that are currently required to generate electricity. These fuels are available in limited supply on Earth and result in air pollution when consumed in the electrical energy generation process. Moreover, as scarcity increases, not just in fuel reserves, but also in electricity infrastructure such as servitudes, generation capacity etc, the costs of electricity also rises. This then brings about an opportunity to reduce input costs if the electrical energy is utilized as efficiently as possible. This can however only be done by the application of a suitable strategy. This thesis develops an electrical load management (ELM) strategy which may be effective in reducing input costs, by reducing electrical energy costs. This strategy has it’s foundation in tried-and-tested ELM strategies (albeit called by other names such as demand-side management (DSM) and Energy Management (EM)) developed by the world’s foremost utility research organization called EPRI over a number of decades, thereby ensuring, to some extent, the success of the proposed strategy. The strategy has been tested, in its constituent parts, in a real world environment in the South African mining industry. The examples of the sub-elements that have been tested in the industry are the artificial neural network (ANN) for short-term forecasting; the statistical regression technique for short-term load forecasting; the analysis of the external factors affecting the electricity supply industry and also the comparison of electricity tariffs in the mining industry. The validity of the strategy is further enhanced by the involvement of Technology Managers within the mining industry which have been involved with ELM in the mining industry for a number of years. Their input was solicited via an in-depth survey which was conducted in this industry. This survey represents the ELM strategy currently in existence of: - 62 shafts or open pit operations, 44 process plants and 5 smelter operations. The largest mining groups in South Africa were involved in this survey so that this survey represents: amongst others, 40% of the gold mining industry, 62% of the platinum mining industry and 95% of the diamond mining industry. The collective experience represented by the survey is equivalent to 67 man-years in ELM in the mining industry. Electricity tariffs are the means by which benefits for electrical load management are obtained. It thus warranted an analysis of all the factors affecting the electricity tariffs and in particular the factors affecting the price of electricity. To this end the Electricity Supply Industry (ESI) was analyzed in-depth and proactively to identify the external factors which may affect the price of electricity. Production intrusions may not be tolerated in the mining industry and as these intrusions have been the major cause for abandoning such ELM strategies previously, an electrical load model with production correlation was developed in this research which affords production a very high priority in the ELM strategy. Moreover, this load model, which is a key element of the ELM strategy in this thesis, forecasts the electrical efficiency of a mine in the near future. The effect of this efficiency forecast is to give management a real-time and proactive tool by which to make decisions. This approach avoids potentially large inefficiencies on the overall mine load such as when the electrical efficiency was only checked at the end of each month. This model may be used either in real-time control mode or in simulation mode to test various ELM initiatives before they are implemented. The model has either a statistical-regression based load-forecasting algorithm or an Artificial Neural Network (ANN) load-forecasting algorithm at its core. The choice of which forecasting methodology is used is determined by the value of the Pearson’s rank correlation coefficient for a set of test data. The latest prevailing ELM technologies have also been incorporated into a matrix for easy identification. The matrix should assist with the implementation of this ELM strategy. Not all of the technologies found in the matrix result in control of the mining load for ELM initiatives such as: “peak-clipping”, “load-shifting” or “valley-filling”. Some of these technologies result in “conservation” of the electrical energy by the application of newer and more efficient techniques to perform the necessary activities found on a typical mine (drilling, ventilation, cooling etc.). A complete strategy for ELM in the South African mining industry is thus developed in this thesis which overcomes two of the most serious pitfalls associated with previous strategies. These pitfalls being, the inadequate focus on production in those strategies and also the lack of real-time, efficiency-forecasting of the overall mine load. The strategy also focuses the potential Electrical Load Manager on the key steps of this process, by means of an intuitive, step-by-step approach. It is grounded in the demand-side management (DSM) experiences of the past, enhanced by actual case studies of the sub-elements in the mining industry and has been ratified by the involvement of very experienced Technology Managers active in ELM in South African mining industry.

The disturbing current situation regarding the world climate has initiated a major wave of urgent developments towards decreasing the overall impact of human activities on the living environment. A major role player in this development is the automobile industry that is inherently connected to pollution of various types, be it air, water or noise pollution. There have been drastic changes not only in the technologies employed in producing vehicles and components, but also in the construction and technologies built into modern automobiles to lessen the overall environmental impact of the industry. Noxious emissions have been decreased, overall efficiencies increased and vehicles are becoming more economical with each new generation. Stricter laws dictate that the level of acceptable vehicle emissions is to be decreased ever further and all manufacturers are developing various possibilities to achieve this. With the emergence of hybrid vehicle technology, there was also a sudden development of different electrical systems that were made viable by the higher onboard voltage systems employed in hybrid vehicles. One of these developments was the electrical air conditioning compressor for use in automobile applications. Although it is designed to operate with a higher voltage than the traditional 12V onboard vehicle systems, it is theoretically possible to incorporate it into a 12V system by making use of a DC-DC converter to step up the supply voltage of the electrical compressor sufficiently to allow for its successful operation. The question therefore arises whether it would be feasible and sensible to employ an electrical air conditioning system in conventional combustion engine vehicles from an overall fuel consumption and vehicle emissions point of view. A modelling approach was taken where an overall vehicle driving simulation was created to represent an average modern production vehicle. The simulation was then extended to include the options of incorporating models for both mechanically and electrically driven air conditioning systems. This provides insight into the influences of the air conditioning system on the vehicle’s overall fuel consumption and an opportunity to compare the influences from the two different systems. This study attempted to provide answers to some of the viability questions regarding the incorporation of electrically driven air conditioning systems into vehicles that use standard 12V onboard voltage systems. It was found that the electrical system has definite potential as a viable replacement option for the conventional system should it be combined with an appropriate alternator and equipped with an efficient control system.