Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work aims to evaluate the performance of some methods used to detect and correct the distorted portions of the secondary current signal waveform, which occur due to the core saturation of current transformers. Such methods are presented didactically divided among techniques existing in the specialized literature and new methodologies proposed. Involving various mathematical tools, methods of correction and detection were combined for the analyzed cases. Computer simulations of faults were made to obtain secondary current signals distorted by saturation, allowing the evaluation of these methodologies. The detection methods were evaluated in terms of the ability to identify saturation intervals and speed response. Moreover, the correction techniques were evaluated in terms of compensation accuracy and their processing time. Transient error calculations and the use of a full cycle Fourier filter were the basis for the qualitative analysis of the correction techniques performance. In each case analyzed, different performances were verified for the combinations tested. It was found that differences in detection time instants of the distorted portions provide different rates of error to the methodologies that are associated with saturation detectors. In this context, one of the techniques proposed for detection of distorted sections showed good precision, ensuring low errors for one of the associated correction methodologies in all the analyzed cases. Also, it was found that methods based on Least Squares have good accuracy for the correction of signals distorted by saturation. / Este trabalho visa avaliar o desempenho de alguns métodos para detecção e correção dos trechos distorcidos da forma de onda dos sinais de corrente secundária, que ocorrem em virtude da saturação do núcleo dos transformadores de corrente. Tais métodos são apresentados didaticamente, divididos entre técnicas existentes na literatura especializada e novas propostas. Envolvendo variadas ferramentas matemáticas, as metodologias de correção e detecção foram combinadas para análise de casos. Simulações computacionais de curtoscircuitos foram realizadas para a obtenção dos sinais da corrente secundária distorcida por saturação. Os métodos de detecção foram avaliados em termos da capacidade de reconhecimento dos intervalos de saturação e velocidade de resposta. Além disso, as técnicas de correção foram avaliadas em termos da 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 das técnicas de correção. Em cada caso analisado, diferentes desempenhos foram verificados. Observou-se que diferenças nos instantes de detecção dos trechos distorcidos propiciam diferentes margens de erro às metodologias de correção, que são associadas aos detectores de saturação. Nesse contexto, uma das técnicas propostas para detecção dos trechos distorcidos apresentou boa precisão, garantindo que uma das metodologias de compensação, a qual foi associada, obtivesse erros relativamente baixos para todos os casos analisados. Também, verificou-se que as metodologias fundamentadas em Mínimos Quadrados possuem boa precisão durante a correção dos sinais distorcidos por saturação.

Orientador: Walmir de Freitas Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T08:26:46Z (GMT). No. of bitstreams: 1 Salles_NewtonJosede_D.pdf: 8861113 bytes, checksum: 46fbfc4ed40c793e3b012449f77b88ab (MD5) Previous issue date: 2013 / Resumo: Recentemente, o ilhamento intencional, ou seja, a operação isolada de uma parte do sistema elétrico de potência que pode ser alimentada localmente por geradores distribuídos, tem representado um grande interesse para as empresas concessionárias de energia elétrica. Tamanho interesse deve-se à capacidade destes geradores em assegurar a redução do tempo de indisponibilidade do fornecimento de energia elétrica, aumentando a confiabilidade das cargas pertencentes ao sistema ilhado. O sucesso da prática do ilhamento intencional é o conhecimento prévio de todas as contingências possíveis que podem resultar em operação ilhada, quer sejam situações de manutenções programadas ou mesmo a perda de subestações de distribuição ou linhas de transmissão de alta tensão. Neste cenário, uma prática comum é utilizar o(s) gerador(es) síncrono(s) distribuído(s) para alimentar o sistema ilhado e garantir a regulação da frequência e da magnitude da tensão, com a atuação do regulador de velocidade e do regulador de tensão, respectivamente. Um dos aspectos mais importantes que deve ser considerado no planejamento do sistema elétrico de potência é o desempenho do sistema de proteção, uma vez que os ajustes dos dispositivos de proteção não são flexíveis o suficiente para acomodar a operação antes e depois de detectado o ilhamento. Neste contexto, esta tese de doutorado apresenta duas contribuições principais: (1) apresentar um estudo detalhado de viabilidade técnica para a realização do ilhamento intencional ¿ dado que o autor deste trabalho é um engenheiro experiente em uma das mais bem conceituadas concessionárias brasileiras, entende-se que o detalhamento destes estudos é de extrema importância para a academia; (2) desenvolver modelos de modernos relés digitais de proteção nos ambientes MATLAB/Simulink, ATP/ATPDraw e ANATEM e utilizar estes modelos em esquemas de proteção suficientemente flexíveis para permitir a viabilidade do ilhamento intencional de geradores síncronos distribuídos. Na avaliação do desempenho de dispositivos de proteção para a formação do ilhamento, são utilizados modelos de relés digitais de proteção desenvolvidos durante o mestrado do autor, bem como novos modelos de relés. Os novos modelos de relés foram desenvolvidos para serem usados em ambientes de análise de transitórios eletromecânicos e eletromagnéticos, como o MATLAB/Simulink, ATP/ATPDraw e ANATEM, constituindo uma poderosa ferramenta de análise e simulação, pois permitem que as interações entre o sistema de proteção e a dinâmica do sistema sejam visualizadas no domínio do tempo. Palavras-chave: Geração distribuída, ilhamento intencional, proteção / Abstract: Nowadays, the utilities have strong interest in practicing the intentional islanding, i.e., the islanded operation of part of the electrical power system fed by distributed generators. This interest is resulted by the capacity of distributed generators to decrease outages and, therefore, to increase system reliability. The success of intentional islanding practice relies on the previous knowledge of all the possible contingencies which may result in islanded operation. These contingencies may be scheduled maintenances or even the loss of distribution substations or transmission lines. Under these circumstances, a common practice is to use the distributed synchronous generators to feed the islanded system and to assure the voltage frequency and magnitude control with the speed governor and voltage regulator actuation, respectively. One of the most important aspects that must be considered in electric power systems planning is the performance of protection system, since the relay settings are not flexible enough to assure the suitable operation before and after the islanding occurrence. In this context, this work has two main contributions: (1) to present a detailed study of intentional islanding technical feasibility ¿ the author is a senior engineer at one of the most important Brazilian utilities, as a result the presentation of how to perform these studies in detail is extremely important for Academy; (2) to develop modern digital relays models using time domain simulation tools such as MATLAB/Simulink, ATP/ATPDraw and ANATEM and to use these models in sufficiently flexible protection schemes to achieve successful intentional islanding operations with synchronous generators. The evaluation of protection systems performance for the intentional islanding practice explore the implemented digital relays models in time domain simulations performed using MATLAB/Simulink, ATP/ATPDraw and ANATEM. This option is an important analysis tool that allows the evaluation of the interaction between protection system and system dynamics during the time. Key-words: Distributed generation, intentional islanding, protection / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

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 Supervisor: Prof. R. Tzoneva Co-supervisor: Prof. P. Petev 2013 / Busbars are the most important components in the distribution networks. Faults on the busbar are uncommon, however an occurrence of a busbar fault can lead to a major loss of power. Busbars are the areas in a substation where the levels of current are high and therefore the protective relay application is very critical. In order for the protection scheme to be successful it is important to carry out the following specifications: Selectivity, Stability, Sensitivity, and Speed. To meet all of the above requirements protection must be reliable, meaning that the protection scheme must trip when called up to do so (dependability) and it must not trip when it’s not supposed to (security). The thesis focuses on the reverse blocking busbar protection scheme with aim to improve the speed of its operation and at the same time to increase operational reliability, flexibility and stability of the protection during external and internal faults by implementation of the extended functionality provided by the IEC61850 standard-based protective IEDs. The practical implementation of the scheme by the use of IEC 61850 standard communication protocol is investigated. The research analyzes in detail the reverse blocking busbar protection scheme that is used at the moment in the power systems and it develops an improved IEC 61850 based reverse blocking busbar protection scheme for a distribution network. The proposed scheme is designed for a radial type of a distribution network and is modeled and simulated in the DigSILENT software environment for various faults on the busbar and its outgoing feeders. The results from the simulations are used further for implementation of the designed protection scheme. A laboratory test bench is build using three compliant with the IEC 61850 standard ABB IEDs 670 series, CMC 356 Omicron test injection device, PC, MOXA switch, and a DC power supplier. Two ways of the reverse blocking signals between the IEDs implementation are considered: hard wired and Ethernet communication by using IEC 61850 standard GOOSE messages. Comparative experimental study of the operational trip response speed of the two implementation shows that the performance of the protection scheme for the case of Ethernet communication is better The thesis findings and deliverables will be used for postgraduate studies of other students, research, short courses, and solution of industrial problems. Keywords: Busbar, Power system, reverse busbar blocking scheme; IEC61850; Distribution, Protection relays, IEDs, GOOSE message, laboratory test bench

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, 2012 / The introduction of the IEC 61850 standard in substations for communication networks and systems by the International Electrotechnical Commission (IEC) in 2003 provided the possibility for communication between devices of different manufacturers. However, the advent of this standard also brought about many challenges associated with it. The challenges introduced by this fairly recent standard of communications in Substation Automation Systems (SAS), and the need for the development of cost effective IEC 61850- compliant devices, motivated the decision of the Centre for Substation and Energy Management Systems within the Electrical Engineering Department of the Cape Peninsula University of Technology to focus on the implementation of the IEC 61850 standard using an embedded hardware platform. The development of an IEC 61850 embedded application requires substantial knowledge in multiple domains such as data networking, software modelling and development of Intelligent Electronic Devices (IEDs), protection of the electrical system, system simulation and testing methods, etc. Currently knowledge about the implementation of the IEC 61850 standard usually resides with vendors and is not in the public domain. The IEC 61850 standard allows for two groups of communication services between entities within the substation automation system. One group utilizes a client-server model accommodating services such as Reporting and Remote Switching. The second group utilizes a peer-to-peer model for Generic Substation Event (GSE) services associated with time-critical activities such as fast and reliable communication between Intelligent Electronic Devices (IEDs) used for protection of the power network. The messages associated with the GSE services are the Generic Object Oriented Substation Event (GOOSE) messages. The use of GOOSE messages for protection of the electrical system is very important in modern substations. Detailed knowledge of the structure of these messages is important in instances requiring fault diagnosis to determine the cause of mal– operation or to address interoperability concerns or when developing custom IEC 61850- compliant devices with limited functionality. A practical protection application (overcurrent) case study is presented where GOOSE messages are exchanged between a commercial IED and an IEC 61850-compliant controller based on an embedded platform. The basic data model and software development of an actuator node for a circuit breaker is proposed using an IEC 61850 communication stack on an embedded platform. The performance of the GOOSE messages is confirmed to be as per the functional behaviour specified, and per the IEC 68150 standard in terms of the temporal behaviour required. This thesis document tables the methods, software programs, hardware interfacing and system integration techniques that allow for the development and implementation of a low cost IEC 61850-compliant controller unit on an embedded systems platform for the substation automation system. The overcurrent case study distributed between a commercial IED (SIEMENS Siprotec device) and the actuator application developed on an embedded platform for this project (DK60 board) is in compliance with the IEC 61850 standard and utilizing GOOSE messaging is successfully completed both in terms of functional and temporal behaviour. This novel research work contributes not only to the academic community, but to the international Power Systems community as a whole. Keywords: IEC 61850 standard, IEDs, GOOSE message, software modelling, software development, substation automation systems, communication stack, embedded systems, actuator.

Indiana University-Purdue University Indianapolis (IUPUI) / The substantial increase demand for electrical energy requires high efficient apparatus dealing with energy conversion. Several technologies have been suggested to implement power supplies with higher efficiency, such as multilevel and interleaved converters. This thesis proposes an energy conversion unit with an optimized number of output voltage levels per number of switches nL=nS. The proposed five-level four-switch per phase converter has nL=nS=5/4 which is by far the best relationship among the converters presented in technical literature. A comprehensive literature review on existing five-level converter topologies is done to compare the proposed topology with conventional multilevel converters. The most important characteristics of the proposed configuration are: (i) reduced number of semiconductor devices, while keeping a high number of levels at the output converter side, (ii) only one DC source without any need to balance capacitor voltages, (iii) high efficiency, (iv) there is no dead-time requirement for the converters operation, (v) leg isolation procedure with lower stress for the DC-link capacitor. Single-phase and three-phase version of the proposed converter is presented in this thesis. Details regarding the operation of the configuration and modulation strategy are presented, as well as the comparison between the proposed converter and the conventional ones. Simulated results are presented to validate the theoretical expectations. In addition a fault tolerant converter based on proposed topology for micro-grid systems is presented. A hybrid pulse-width-modulation for the pre-fault operation and transition from the pre-fault to post-fault operation will be discussed. Selected steady-state and transient results are demonstrated to validate the theoretical modeling.