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This thesis proposes, analyses and implements a fast and accurate real-time power system disturbances identification method based on an enhanced linear least squares algorithm for mitigation and monitoring of various power quality problems such as current harmonics, grid unbalances and voltage dips. The enhanced algorithm imposes less real-time computational burden on processing the system and is thus called ???efficient least squares algorithm???. The proposed efficient least squares algorithm does not require matrix inversion operation and contains only real numbers. The number of required real-time matrix multiplications is also reduced in the proposed method by pre-performing some of the matrix multiplications to form a constant matrix. The proposed efficient least squares algorithm extracts instantaneous sine and cosine terms of the fundamental and harmonic components by simply multiplying a set of sampled input data by the pre-calculated constant matrix. A power signal processing system based on the proposed efficient least squares algorithm is presented in this thesis. This power signal processing system derives various power system quantities that are used for real-time monitoring and disturbance mitigation. These power system quantities include constituent components, symmetrical components and various power measurements. The properties of the proposed power signal processing system was studied using modelling and practical implementation in a digital signal processor. These studies demonstrated that the proposed method is capable of extracting time varying power system quantities quickly and accurately. The dynamic response time of the proposed method was less than half that of a fundamental cycle. Moreover, the proposed method showed less sensitivity to noise pollution and small variations in fundamental frequency. The performance of the proposed power signal processing system was compared to that of the popular DFT/FFT methods using computer simulations. The simulation results confirmed the superior performance of the proposed method under both transient and steady-state conditions. In order to investigate the practicability of the method, the proposed power signal processing system was applied to two real-life disturbance mitigation applications namely, an active power filter (APF) and a distribution synchronous static compensator (D-STATCOM). The validity and performance of the proposed signal processing system in both disturbance mitigations applications were investigated by simulation and experimental studies. The extensive modelling and experimental studies confirmed that the proposed signal processing system can be used for practical real-time applications which require fast disturbance identification such as mitigation control and power quality monitoring of power systems

Fires generate heat and propel burning material into the air above and around the core of the fire. Fires under power lines reduce the breakdown strength of the air insulation due to the influence the heat and particles have on the electric field surrounding the conductors. The result can be flashovers and undesirable power supply interruptions in the electrical transmission network with a considerable impact on Eskom's 275 kV and 400 kV MTS (main transmission system) networks. Eskom typically experiences a loss in sales, a reduction in the quality of the power supplied to consumers and disgruntled consumers who in turn experience financial losses due to a loss in production. In this thesis, the high frequency characteristics of corona and electrical discharges generated by the fire phenomena are studied. The influence of the operating voltages on the electric fields, the potential of different media to initiate ionisation and comparison of conductor construction (bundling and diameter) are all considered in the measurement of high frequency signals in the range of frequencies available in the tuned circuits connected to power lines. The propagation of these high frequency signals is studied both in isolation of other sources of high frequency signals (within controlled laboratory conditions) and in the real environment adjacent to all other interfering sources. Finally the fingerprinting of the varying high frequency signal patterns associated with fires is considered with a view to implementing an operational early detection device. Early detection of a fire allows the utility to understand the source of a system fault, manage it effectively and if possible pre-empt possible failure by means of appropriately applied standard operating guidelines (SOG) to minimise the impact. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

This thesis proposes, analyses and implements a fast and accurate real-time power system disturbances identification method based on an enhanced linear least squares algorithm for mitigation and monitoring of various power quality problems such as current harmonics, grid unbalances and voltage dips. The enhanced algorithm imposes less real-time computational burden on processing the system and is thus called ???efficient least squares algorithm???. The proposed efficient least squares algorithm does not require matrix inversion operation and contains only real numbers. The number of required real-time matrix multiplications is also reduced in the proposed method by pre-performing some of the matrix multiplications to form a constant matrix. The proposed efficient least squares algorithm extracts instantaneous sine and cosine terms of the fundamental and harmonic components by simply multiplying a set of sampled input data by the pre-calculated constant matrix. A power signal processing system based on the proposed efficient least squares algorithm is presented in this thesis. This power signal processing system derives various power system quantities that are used for real-time monitoring and disturbance mitigation. These power system quantities include constituent components, symmetrical components and various power measurements. The properties of the proposed power signal processing system was studied using modelling and practical implementation in a digital signal processor. These studies demonstrated that the proposed method is capable of extracting time varying power system quantities quickly and accurately. The dynamic response time of the proposed method was less than half that of a fundamental cycle. Moreover, the proposed method showed less sensitivity to noise pollution and small variations in fundamental frequency. The performance of the proposed power signal processing system was compared to that of the popular DFT/FFT methods using computer simulations. The simulation results confirmed the superior performance of the proposed method under both transient and steady-state conditions. In order to investigate the practicability of the method, the proposed power signal processing system was applied to two real-life disturbance mitigation applications namely, an active power filter (APF) and a distribution synchronous static compensator (D-STATCOM). The validity and performance of the proposed signal processing system in both disturbance mitigations applications were investigated by simulation and experimental studies. The extensive modelling and experimental studies confirmed that the proposed signal processing system can be used for practical real-time applications which require fast disturbance identification such as mitigation control and power quality monitoring of power systems

Thesis (D.Tech (Engineering Electrical)) - Central University of Technology, Free State, 2005 / When Thomas Edison invented his carbon filament lamp in 1879, gas shares fell overnight. A committee of inquiry was set up to examine the future possibilities of the new method of lighting, and had reached the conclusion that electric light in the home was fanciful and absurd. Today electric light burns in practically every house in the civilised world, with many great advances in the production and use of electricity and electric power supplied by various utilities. The objective of the electric utility to deliver pure sinusoidal voltage at fairly constant magnitude throughout their system is complicated by the fact that there are currently loads on the system that produce harmonic voltages, which result in distorted voltages and currents that can adversely impact on the system performance in different ways. Because the numbers of harmonic producing loads have increased over the years, it has become necessary to address their influence, when making any additions or changes to an installation. Quality of supply measurements have long been used to characterise non-linearity on the power system, and have traditionally been measured with expensive portable analysers. A potentially faster, more integrated, and more flexible solution to measure the harmonics with a Supervisory System is accomplished by this research. Any script which aspired to cover in full detail the whole field of a subject so enormous as techniques to measure the quality of electricity supply on a SCADA system, would hardly be practical in less than a few volumes. The pretensions of this research are both modest and of a more immediate value to the reader.

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 / The IEC 61850 standard, “Communication networks and systems in substations” was promulgated to accommodate the need for a common communication platform within substations for devices from different vendors. The IEC 61850 standard proposes a substation automation architecture that is Ethernet-based, with a “station-bus” for protection devices within the substation and a “process bus” where raw data from the voltage and current transformers are published onto the data network using a device known as a Merging Unit. To date, most of the standardization efforts were focused at the station bus level where event-triggered messages are exchanged between the substation automation devices, commonly referred to as Intelligent Electronic Devices (IEDs). These messages are known as Generic Object Oriented Substation Event messages. Equipment from vendors to accommodate the “process bus” paradigm, however is still limited at present. The Centre for Substation Automation and Energy Management Systems was established within the Electrical Engineering Department at the Cape Peninsula University of Technology with one of its objectives being the development of equipment either for simulation or real-time purposes in compliance with the IEC 61850 standard. In order to fulfil this long-term objective of the Centre, an in-depth understanding of the IEC 61850 standard is required. This document details the efforts at acquiring the requisite knowledge base in support of the educational objectives of the Centre and the research project implements a simulation of a merging unit which is compliant with the functional behavior as stipulated by the standard. This limited functional implementation (i.e. non-real-time) of the merging unit, is achieved through the development of a virtualized data acquisition node capable of synthetic generation of waveforms, encoding of the data and publishing the data in a format compliant with the IEC 61850-9-2 sampled value message structure. This functional behavior of the virtual sensor node which was implemented has been validated against the behavior of a commercial device and the sampled value message structure is validated against the standard. The temporal behavior of the proposed device is commented upon. This research project forms the basis for future real-time implementation of a merging unit.

Orientadores: Walmir de Freitas Filho, José Carlos de Melo Vieira Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T11:09:25Z (GMT). No. of bitstreams: 1 Delvecchi_EsloanyDaisyCarniatto_M.pdf: 1048681 bytes, checksum: 837e57f3ee3363dd7bb9f49a72408fe1 (MD5) Previous issue date: 2011 / Resumo: Geradores síncronos conectados em redes de distribuição de energia elétrica estão sujeitos a operarem de forma ilhada após a ocorrência de distúrbios na rede elétrica. Ilhamento ocorre quando uma parte da rede de distribuição torna-se eletricamente isolada da fonte de energia principal (subestação), mas continua a ser energizada por geradores distribuídos conectados no subsistema isolado. A prática atualmente utilizada pelas concessionárias e recomendada nos principais guias técnicos é desconectar todos os geradores tão logo ocorra um ilhamento. Tipicamente, é necessário detectar uma situação de ilhamento em menos de dois segundos, dependendo, principalmente, do tempo de operação dos religadores automáticos. Os métodos mais comuns e baratos para detectar ilhamento compreendem relés baseados em medidas de freqüência (sub/sobrefrequência, taxa de variação de frequência e "salto de vetor") e o relé de tensão. No entanto, esses relés podem falhar se os níveis de desbalanço de potência ativa e reativa no subsistema ilhado forem pequenos. Portanto, o objetivo dessa dissertação é investigar a potencialidade de novos sinais para detectar ilhamento de geradores síncronos distribuídos, como forma de substituição ou complementação aos dispositivos de proteção anti-ilhamento convencionais. Os sinais analisados neste trabalho são taxa de variação da potência ativa (dP/dt), a relação Volts por Hertz (V/Hz), a variação da impedância (Z) medida no ponto de acoplamento comum (PAC), e a diferença angular ('delta' 'teta') entre as tensões medidas no PAC e na subestação. A investigação é baseada no levantamento de um conjunto de curvas relacionando tempo de detecção e desbalanço de potência ativa/reativa e nas zonas de não detecção, as quais fornecem os pontos de operação para os quais o relé em estudo falha na detecção do ilhamento. As curvas e as zonas são obtidas através de simulações de transitórios eletromagnéticos trifásicas considerando diferentes perfis de carga-geração na rede ilhada. Os resultados obtidos mostram que os sinais analisados têm um grande potencial para esse tipo de aplicação, porém são sujeitos à atuação indevida no caso da ocorrência de eventos que não sejam ilhamentos na rede de distribuição. Assim, uma análise de falsa operação também é conduzida e são propostas melhorias para minimizar e/ou eliminar a atuação indevida desses relés aqui investigados / Abstract: Synchronous generators connected to distribution power networks are likely to operate islanded following faults clearance in the system. Islanding occurs when a portion of the distribution system becomes electrically isolated from the substation, yet it continues energized by distributed generators connected to the islanded system. Utilities and standards recommend the disconnection of distributed generators immediately after islanding occurrences, otherwise it can lead to a number of problems to the generator and the connected loads. Typically, it is required to detect an islanding situation faster than two seconds after the island formation, depending, mainly, on the operation time of automatic reclosers. The most common and economical methods to detect islanding include the relays based on measures of frequency (under/over frequency, rate of change of frequency and vector surge) and voltage. However, these relays can fail if the active and reactive power imbalance levels in the islanded system are small. Therefore, the objective of this thesis is to investigate the potentiality of new signals to detect islanding of distributed synchronous generators, as replacement or complement to conventional protection anti-islanding devices. The signals analyzed in this research are the rate of change of generator active power (dP/dt), the ratio Volts per Hertz (V/Hz), impedance variation (Z) measured at the point of common coupling (PCC), and the angular difference ('delta' 'teta') between the voltage angle measured at the PCC and at the utility substation. The investigation is based on a set of curves, which relate time of islanding detection and active/reactive power imbalance and on the nondetection zones, which provide the operating points for which the relay fails to detect the islanding. These are obtained through electromagnetic transient three-phase simulations considering different profiles of generation-load in the islanded network. The results show that the signals analyzed have a huge potential for this type of application, however, their performance can decrease in case of occurrence of non-islanding events in the distribution system. Thereby, an analysis of false operation is conducted in order to propose improvements to minimize and/or to eliminate improper behavior of these relays / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientador: Walmir de Freitas Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T00:53:15Z (GMT). No. of bitstreams: 1 Silva_RafaelSchincariolda_M.pdf: 3440136 bytes, checksum: 042a03fcb6272566cfc1c79d07478e1c (MD5) Previous issue date: 2012 / Resumo: O aumento da penetração de geradores em redes de distribuição de energia elétrica além de diversificar a matriz elétrica proporciona benefícios técnicos e econômicos. Contudo, também levanta preocupações relativas à confiabilidade no suprimento de energia elétrica. Para plantas eólicas conectadas na média e alta tensão são estabelecidos requisitos de "Fault Ride-Through" que determinam que os geradores devem permanecer conectados à rede durante perturbações com afundamentos de tensão e, em alguns casos, fornecer reativos para o reestabelecimento da tensão terminal. Porém, implementar tais requisitos para geradores na baixa tensão não é trivial. Na ocorrência de grandes perturbações os geradores distribuídos devem obrigatoriamente ser desconectados em casos de ilhamento, caso contrário a segurança de pessoas e equipamentos é colocada em risco e a qualidade de energia fornecida não é garantida. Ainda, durante curtos-circuitos os geradores contribuem para ao aumento das correntes de falta e os esquemas de proteção podem sofrer impactos na seletividade e coordenação. Por isso, para atender o requisito de "Fault Ride- Through" seria necessário além de manter os geradores conectados rever os esquemas de proteção de sobrecorrente, sendo necessários estudos dos impactos desta iniciativa e a análise do comportamento dos principais tipos de geradores distribuídos na ocorrência de curtos-circuitos. Nesta dissertação de mestrado, uma rede de distribuição com geradores distribuídos foi analisada através do estudo de sucessivas simulações de transitórios eletromagnéticos. O comportamento de três tipos de geradores distribuídos na ocorrência de curtos-circuitos foi investigado por meio de estudos de estabilidade, da análise das características de afundamentos de tensão e do suporte de reativos. Os geradores síncronos se mostraram com maior capacidade de suportarem faltas temporárias na rede. Os impactos do aumento das correntes de falta nas proteções contra sobrecorrente e da não desconexão do gerador do sistema ilhado também foram analisados. Os resultados mostraram que a presença de geradores distribuídos pode causar problemas na seletividade e na coordenação da proteção, alem de deteriorar o comportamento transitório de geradores ilhados / Abstract: The increase of distributed generation penetration in distribution systems not only helps to diversify the electrical matrix but also brings both technical and economic benefits. Yet, it also raises worries related to energy supply reliability. For wind power plants into the medium and high voltage networks there are the grid codes for "Fault Ride-Through" which stands that wind generators ought to ride a fault with voltage sag and, in some cases, provide reactive power for the terminal voltage restoration. However, implementing such requisites for low voltage connected generators is not a trivial task, as under great perturbations the distributed generators are required to be disconnected from the grid if an islanding situation occurs. Otherwise, people and equipment security would be at risk and the quality of the supplied power cannot be guaranteed. Besides, during short-circuits generators contribute to the increased fault currents along the grid and because of that the protection schemes should experience loss of selectivity and coordination. So, meeting the fault ride-through requirement demand a review of the anti-islanding schemes in order to permit generator islanding, as well as review the protection schemes to guarantee selectivity and coordination. Therefore, studies about the impacts of this initiative are necessary as well as the main generators behavior analysis under short-circuits. In this dissertation, a distribution network was analyzed through successive electromagnetic transient simulations. The behavior of three types of distributed generators under shortcircuits was investigated by stability studies, voltage sag characteristics and reactive power support. Synchronous generators showed to present the best capability to ride through temporary faults on the grid. The impacts on overcurrent protection of increased shortcircuit currents due to the distributed generators and impacts of not disconnecting the generators during islanding situations were also analyzed. The outcomes showed that keeping distributed generators connected might lead to problems on the protection selectivity and coordination and deteriorate the transient behavior of generators / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Com novas normas, incentivos governamentais e preocupação com questões ambientais, é esperado um crescimento no número de unidades de geradoras conectadas a rede a partir dos consumidores. Algumas questões técnicas relacionadas à elevada penetração de geração distribuída nos alimentadores de distribuição preocupam as concessionárias de energia, as quais buscam meios de prevenir possíveis efeitos indesejados no sistema elétrico. Esta pesquisa apresenta o desenvolvimento de um relé digital aplicado à proteção da conexão de geração distribuída na rede elétrica, com foco em microgeração e minigeração proveniente de geradores síncronos, assíncronos e inversores. O relé digital contempla as principais funções de proteção exigidas pelos procedimentos e normas de acesso nacionais, incluindo algoritmos anti-ilhamento. O seu funcionamento se dá pela medição das grandezas elétricas no ponto de conexão entre a geração distribuída e a rede elétrica, filtragem digital dos sinais e processamento dos algoritmos das funções de proteção. Como num relé digital convencional, as funções de proteção podem ser configuradas individualmente, permitindo construção de expressões lógicas e de bloqueio. O protótipo pode ser monitorado e controlado localmente, através de uma aplicação instalada em um computador e utilizando a rede Ethernet. O protótipo permite controle remoto pela concessionária através de uma rede de telecomunicação em malha instalada no sistema elétrico de distribuição, utilizando protocolo ZigBee. É apresentada uma revisão bibliográfica sobre os efeitos e os problemas da geração distribuída no sistema elétrico, contextualizando o futuro das nossas redes de distribuição em relação a situação de países mais desenvolvidos nesse tema. Em seguida, são apresentadas as principais técnicas de processamento digital de sinais para relés digitais e o funcionamento das funções de proteção. Os detalhes do desenvolvimento do hardware, estratégias para filtragem digital e implementação dos algoritmos de proteção são apresentados. Algumas técnicas no algoritmo de filtragem e nas funções de proteção, como a medição de frequência trifásica utilizando a transformada de Clarke, são discutidas e avaliadas. Os resultados dos testes de funcionamento do protótipo, realizados em laboratório, são apresentados. Concluiu-se que o relé digital contempla um conjunto de proteções que abrange as principais normas para o acesso de geração distribuída no Brasil, pode ser utilizado como proteção de retaguarda para sistemas já dotados de proteções internas, como inversores, além de possibilitar o controle remoto de geração distribuída através da rede de telecomunicação em malha com protocolo ZigBee. / With new standards, government incentives and concerns about environmental questions, is expected the growth of the number of generating units connected to the grid from consumers. Some technical issues related to the high penetration of distributed generation on distribution feeders concerns the power utilities, which look for solutions to prevent possible unwanted effects on the electrical system. This research presents the development of a digital relay applied to protect the interconnection of distributed generation in the grid, focusing on micro and mini electricity generation plants from synchronous and asynchronous generators, and inverters. The digital relay contains the main protection functions required by PRODIST and utilities standards, including anti-islanding algorithms. Its operation is given by the measurement of electrical parameters at the point between the distributed generation and grid, followed by digital signal filtering and protection algorithms processing. Like a conventional digital relay, the protection functions can be individually configured, it’s possible to build logical and blocking expressions with them. The prototype can be monitored and controlled by a personal computer connected in the same local network. The computer must run an interface program. The prototype allow remote control by the utilities, this communication is done by a mesh network installed along the electric distribution system, using the ZigBee protocol. It’s presented a review about the effects and problems caused in the electrical power system by the distributed generation, giving the context of the future Brazilian distribution network in relation to the actual situation of more experienced countries on distributed generation. Following, it’s presented the main technics of digital signal processing applied to digital relays and operation of the protection functions. So then, the details of the hardware development, digital filtering strategies and the implementation of the protection algorithms are presented. Some technics applied to the filtering algorithms and protection function, as the three-phase frequency measurement using Clarke’s transformation, are discussed and evaluated. The test results of the prototype operation are presented, the tests were done in laboratory. The digital relay contain a set of protection functions that covers the main standards of distributed generation access in Brazil, it’s possible to use as a backup protection for systems with protections embedded, as grid tie inverters, and the possibility of remote control of distributed generation through the mesh network with ZigBee protocol.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents innovative methods for detection and correction of the distorted portions of the secondary current waveforms, which occur due to the core saturation of current transformers (CTs). The detection technique is based on the analysis of the plans formed by the secondary current (i2) and their difference-functions (deln). The distance between consecutive points in these plans has a significant increase when saturation occurs, bucking the trend during the undistorted intervals, which are not corrupted by CT saturation. Additionally, the proposed correction of these signals is based on a technique of curve fitting by least squares, which uses the frequency signal estimated from the secondary current signals as a parameter of compensation. The aforementioned frequency signal is estimated using the Mathematical Morphology operators of dilation and erosion, which are used to estimate future values of the α and β signals obtained from the Clarke Transform. Computational simulations of short circuits were performed to obtain the secondary current signals distorted by CT saturation. The detection method was evaluated in terms of the ability to identify saturation intervals and its speed of response. Moreover, the correction technique was evaluated in terms of the compensation accuracy and its processing time. Calculations of transient error and the use of a full cycle Fourier filter were the basis for the qualitative analysis of the performance of the correction technique. The tests revealed that the combination of the proposed techniques ensures excellent accuracy during correction signals distorted by saturation, showing that the proposals constitute a robust tool for use in numerical relays, increasing the reliability of protection schemes in situations involving the saturation of TCs. / Este trabalho apresenta métodos inovadores para detecção e correção dos trechos distorcidos da forma de onda dos sinais da corrente secundária, que ocorrem em virtude da saturação do núcleo dos transformadores de corrente (TCs). A técnica de detecção é fundamentada na análise dos planos formados pela corrente secundária (i2) e suas funções-diferença (deln). A distância entre pontos consecutivos nesses planos tem um aumento significativo quando a saturação ocorre, contrariando a tendência durante os intervalos não distorcidos por saturação. Além disso, a proposta para correção desses sinais utiliza uma técnica de ajuste de curvas por Mínimos Quadrados, a qual emprega o sinal de frequência estimado a partir dos sinais da corrente secundária como parâmetro de compensação. O referido sinal de frequência é estimado por uma metodologia fundamentada em Morfologia Matemática, cujos operadores de dilatação e erosão são utilizados para estimação de valores futuros dos sinais α e β, obtidos a partir da Transformada de Clarke. Simulações computacionais de curtos-circuitos foram realizadas para a obtenção dos sinais da corrente secundária distorcida por saturação. O método de detecção foi avaliado em termos da capacidade de reconhecimento dos intervalos de saturação e velocidade de resposta. Ainda, a técnica de correção foi avaliada com relação à precisão da compensação e do tempo de processamento. Cálculos de erro transitório e a utilização de um filtro de Fourier de ciclo completo foram a base para a análise qualitativa do desempenho da técnica de correção. Os testes revelaram que a combinação entre as técnicas propostas garante excelente precisão durante a correção dos sinais distorcidos por saturação, mostrando que as propostas constituem uma ferramenta robusta para aplicação em relés numéricos, aumentando a confiabilidade dos esquemas de proteção em situações que envolvam a saturação dos TCs.