In this thesis, we studied the narrowband power line communication system. This system mainly utilizes the 60Hz power line as the medium to transmit network signals. In the beginning, we studied the power line channel characteristics and the coupling circuit structure, that was used to couple the signal to the power line. Impedance mismatch and signal attenuation may occur when the loading in the power line network changes. To this end we added a driver to the coupling circuit to reduce the output impedance, and hence enhance signal magnitude. In addition, we add the cross-phase coupling circuit with bandpass filter characteristics at the 220V socket. It was found that our cross-phase coupling circuit was able to improve the performance of the power line communication system when cross-phase transmission took place. Finally, we simulated the indoor power line network environment, measured several kinds of residential appliance noise and analyzed the influence on the power line communication system of the appliance noise.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2017-12-21T11:52:32Z No. of bitstreams: 1 luisguilherrmedasilvacosta.pdf: 2910682 bytes, checksum: da61cee3e668dc7356aa3ab54ff0c28c (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-22T11:58:44Z (GMT) No. of bitstreams: 1 luisguilherrmedasilvacosta.pdf: 2910682 bytes, checksum: da61cee3e668dc7356aa3ab54ff0c28c (MD5) / Made available in DSpace on 2017-12-22T11:58:44Z (GMT). No. of bitstreams: 1 luisguilherrmedasilvacosta.pdf: 2910682 bytes, checksum: da61cee3e668dc7356aa3ab54ff0c28c (MD5) Previous issue date: 2017 / Esta tese de doutorado apresenta, inicialmente, uma revisão sobre acopladores para power line communication (PLC), utilizados para acoplar o sinal dos transceptores PLC à rede de energia elétrica. As questões predominantes para o projeto de acopladores e, consequentemente, os diferentes tipos de acopladores são discutidos. Uma classificação dos acopladores PLC baseada nos tipos de acoplamentos (capacitivo, indutivo, resistivo e por antenas), níveis de tensão, largura de banda de frequência, modos de propagação e números de conexões com a rede de energia elétrica é apresentada. Em seguida, o projeto de circuitos PLC de acoplamento capacitivo não adaptativos, single input single output (SISO) de baixa tensão para aplicações banda larga e banda estreita são discutidos. O acoplador PLC banda estreita é projetado para a banda de frequência de 9 kHz-500 kHz, enquanto os acopladores banda larga são projetados para a banda de frequência de 1.7-50 MHz, 1.7-100 MHz e 1.7-500 MHz. Além disso, discute-se as especificações e o projeto dos protótipos desses circuitos de acoplamento PLC medindo seus parâmetros de espalhamento. A seguir, é discutida a medida da impedância de acesso da rede de energia elétrica de baixa tensão na banda de frequência 2- 500 MHz, visando apresentar prévio conhecimento da impedância de acesso da rede de energia elétrica no Brasil com base em uma campanha de medição realizada em várias instalações em três cidades brasileiras diferentes. Além disso, é proposto um procedimento para obter um modelo estatístico da impedância de acesso na referida faixa de frequência. Com base em uma série de medidas de impedâncias de acesso da rede de energia elétrica e critérios para a escolha de modelos estatísticos, esta tese sugere duas distribuições para modelar as componentes resistência e reatância da impedância de acesso da rede de energia elétrica. Uma vez que, os parâmetros de tais modelos mudam com a frequência e que a impedância de acesso é um processo aleatório no domínio da frequência, um modelo simples para gerar amostras em função desse processo aleatório, que leva em consideração as distribuições sugeridas, é detalhado. Por fim, é proposto um circuito de acoplamento adaptativo PLC, capacitivo, SISO de baixa tensão. Estes circuitos de acoplamento adaptativos usam três diferentes filtros analógicos passa-baixa com diferentes impedâncias de entrada. A impedância de entrada de cada filtro analógico é projetado de acordo com os valores obtidos através da campanha de medição, e a impedância de saída é projetada para 50 Ω. A escolha do filtro analógico que proporciona melhor casamento de impedância com a rede de energia elétrica é obtido por um microcontrolador, que através de um conversor analógico digital, monitora a tensão fornecida por um circuito que mede a potência dos sinais injetados nos acopladores PLC pelos transceptores PLC. A monitoração da potência é realizada continuamente pelo conversor analógico digital do microcontrolador que escolhe qual o filtro analógico proporciona o melhor casamento de impedância com a rede de energia elétrica e comuta os filtros analógicos através de uma chave de analógica conectando os transceptores PLC a rede de energia elétrica através dos acopladores PLC. Além disso, as medições dos valores do parâmetro de espalhamento S11 confirmam que a componente resistiva da impedância de acesso da rede de energia elétrica apresentou melhor casamento de impedância entre 50 Ω e 100 Ω. Por fim, os valores medidos do parâmetro de espalhamento S12 mostram que a atenuação cresce com o aumento da frequência devido ao comportamento indutivo da rede de energia elétrica. / This work outlines a comprehensive review of PLC coupling circuits, which are required for narrowband and broadband PLC transceivers. Prevailing issues that protract the design of couplers and consequently subtended the inventions of different types of couplers are clearly described. Also, it provides a useful classification of PLC couplers based on the type of physical couplings, voltage levels, frequency bandwidth, propagation modes and a number of connections. Next, the focus is on the design of non-adaptive capacitive, SISO and low-voltage (LV) PLC coupling circuits for both broadband and narrowband applications. The narrowband cover the frequency band 9 kHz-500 kHz, while broadband frequency bands are 1.7-50MHz, 1.7-100MHz and 1.7- 500 MHz. Moreover, it discusses the specification and design of the prototypes of the PLC coupling circuits measuring their scattering parameters. The access impedance of Brazilian in-home, broadband and low-voltage electric power grid in the frequency band 2-500 MHz is taken into account. Based on the use of a measurement setup a large measurement campaign that was carried out in several facilities in three different Brazilian cities is discussed. Also, a procedure to obtain a statistical model of the access impedance in the aforementioned broadband frequency is outlined. Based on a number of measured access impedances and well-known criteria for choosing statistical models, two distributions to model the resistance and reactance components of the access impedance are suggested. Due to the fact that the parameters of such models change with the frequency and the access impedance is a random process in the frequency domain, a simple and effective model to generate samples function of such random process, which takes into account the suggested distributions, is addressed. Finally, adaptive capacitive, SISO and LV PLC coupling circuits are proposed for broadband power line communication. These adaptive coupling circuits use three different analog low-pass filter for impedance matching. This filter is an array of analog low-pass irregular filters that separate the input and output signal into three analog low-pass filters, each one matching the impedance between the electric power grid and PLC transceiver. The input impedance of each filter has a different impedance value, chosen according to the impedance of the measurement campaign, and the output impedance is fixed in 50 Ω for all analog low-pass filter. The choice of the analog filter that provides better impedance matching to the electrical power grid is obtained by a microcontroller, which through an analog-to-digital converter (ADC), measure the voltage provided by a circuit that measures the power of the signals injected into the PLC coupling circuit by the PLC transceivers. The power is continuously measured by an ADC of the microcontroller which chooses which analog filter provides the best impedance matching with the electric power grid and switches the analog filters through an analog switcher connecting the PLC transceivers to the electric power grid through the PLC coupling circuit. In addition, the measured values of the scattering parameter S11 show that the best impedance matching occurs when the resistive impedance component of the access impedance is between 50 Ω and 100 Ω . For the scattering parameter S12 it has been found that the attenuation increases as the frequency increases because of the inductive behavior of the electric power grid.

Switching of shunt reactors and capacitor banks is known to cause a very high rate of rise of transient recovery voltage across the circuit breaker contacts. With improvements in circuit breaker technology, modern SF6 puffer circuits have been designed with less interrupter per pole than previous generations of SF6 circuit breakers. This has caused modern circuit breakers to operate with higher voltage stress in the dielectric recovery region after current interruption. Catastrophic failures of modern SF6 circuit breakers have been reported during shunt reactor and capacitor bank de-energisation. In those cases, evidence of cumulative re-strikes has been found to be the main cause of interrupter failure. Monitoring of voltage waveforms during switching would provide information about the magnitude and frequency of small re-ignitions and re-strikes. However, measuring waveforms at a moderately high frequency require plant outages to connect equipment. In recent years, there have been increasing interests in using RF measurements in condition monitoring of switchgear. The RF measurement technique used for measuring circuit breaker inter-pole switching time during capacitor bank closing is of particular interest. In this thesis, research has been carried out to investigate switching transients produced during circuit breaker switching capacitor banks and shunt reactors using a non-intrusive measurement technique. The proposed technique measures the high frequency and low frequency voltage waveforms during switching operations without the need of an outage. The principles of this measurement technique are discussed and field measurements were carried out at shunt rector and capacitor bank installation in two 275 kV air insulated substations. Results of the measurements are presented and discussed in this thesis. The proposed technique shows that it is relatively easy to monitor circuit breaker switching transients and useful information on switching instances can be extracted from the measured waveforms. Further research works are discussed to realise the full potential of the measuring technique.