https://repositorio.ufu.br/handle/123456789/18974 Tue, 11 Aug 2026 04:31:48 GMT 2026-08-11T04:31:48Z https://repositorio.ufu.br/handle/123456789/49286 Title: Análise computacional da proteção direcional de sobrecorrente 67F/67N aplicada à linha de transmissão de 345 kV Furnas–Poços de Caldas Abstract: The Brazilian electrical power system comprises an extensive interconnected grid in which transmission lines connect different generation and load centers at high voltage levels. In transmission lines supplied from both ends, short-circuit current may receive contributions from different sources and flow in different directions, making current magnitude alone insufficient to determine the fault direction. In this context, this work presents a computational analysis of directional overcurrent functions 67F and 67N applied to the 345 kV transmission line connecting the Furnas and Poços de Caldas substations in Minas Gerais, Brazil. The 131 km transmission system was modeled in ATP/ATPDraw using Thévenin equivalents to represent the external networks and an equivalent π model for the transmission line. Twenty-seven short-circuit scenarios were simulated, covering three-phase, phase-to-phase-to-ground, phaseto- phase, and single-phase-to-ground faults. Variations in fault location, fault resistance, and fault inception angle were considered, including faults internal and external to the protected line section. A Python routine was developed to process the waveforms exported from ATP/PlotXY in COMTRADE format and extract voltage and current phasors using the Discrete Fourier Transform. For the analysis of function 67F, phase-A current and the quadrature polarizing voltage VBC were used. For function 67N, zero-sequence voltage V0 and inverted zero-sequence current −I0 were employed. The phasor diagrams allowed the faults to be classified as forward or reverse for the relays installed at both ends of the transmission line. The sensitivity analysis showed that, for function 67F, maximum torque angle values between 30◦ and 90◦ correctly classified all evaluated cases, with 45◦ presenting the lowest mean angular distance from the maximum sensitivity axis. For function 67N, values between −15◦ and −90◦ produced consistent classifications in all cases, while −90◦ provided the best overall alignment among the evaluated values. The results demonstrated the influence of the maximum torque angle on directional classification and contributed to understanding the behavior of functions 67F and 67N in a transmission line supplied from both ends. The study was limited to the behavior of the directional element and did not include pickup settings, time delays, or circuit-breaker tripping commands. Thu, 30 Jul 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49286 2026-07-30T00:00:00Z https://repositorio.ufu.br/handle/123456789/49015 Title: Estudo de caso de eficiência energética em indústria alimentícia Abstract: Energy efficiency has been established as one of the central pillars for the sustainable development of industry, especially in the food sector, whose energy demand is significant due to intensive processes in cold, ventilation, compression and cargo handling. In this context, practices that aim at the rational use of electric energy gain prominence, both for their environmental benefits and for the favorable economic impacts they provide. The adoption of measures aimed at efficiency not only reduces energy waste, but also collaborates directly with corporate goals related to sustainability, competitiveness and innovation. The present work is part of this scenario, proposing an applied analysis of the operation of electric motors in ventilation systems of a refrigeration plant, with emphasis on freezing tunnels. The proposal aims to identify opportunities for improvement through technical and operational adjustments in existing components, without the need for immediate large investments in new equipment. The strategy involves the study of the behavior of the motors in front of the demands of the system, evaluating its conformity with the dimensioning, efficiency of operation and influence on the thermal process of the plant. To support the proposal, a theoretical investigation was carried out on the main concepts related to energy efficiency, including electrical losses in engines, yield curves, optimal operating load and impact of mechanical changes in equipment performance. The strategy involves the study of the behavior of the motors in front of the demands of the system, evaluating its conformity with the dimensioning, efficiency of operation and influence on the thermal process of the plant. To support the proposal, a theoretical investigation was carried out on the main concepts related to energy efficiency, including electrical losses in engines, yield curves, optimal operating load and impact of mechanical changes in equipment performance. The methodology adopted considered field measurements, operational data analysis, technical simulations and energy consumption projections, using appropriate tools to estimate the potential impacts of proposed modifications. Finally, the initiative contributes to the strengthening of corporate strategies aimed at optimizing resources, reducing operating costs and mitigating environmental impacts. The analysis presented in this work seeks to offer technical subsidies for more conscious and assertive decisions in the use of electric energy, promoting a modern approach and aligned with current challenges of the industry. By emphasizing the relationship between applied engineering, sustainability and competitiveness, the study reaffirms the relevance of energy efficiency as an indispensable tool for improving production processes, demonstrating that well-planned interventions can generate significant impacts at various levels of the organization. Tue, 08 Jul 2025 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49015 2025-07-08T00:00:00Z https://repositorio.ufu.br/handle/123456789/48826 Title: Análise comparativa de sistemas fotovoltaicos com inversores string e tecnologias MLPE Thu, 14 Nov 2024 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48826 2024-11-14T00:00:00Z https://repositorio.ufu.br/handle/123456789/48680 Title: Análise de Sistemas de Distribuição com REDs Utilizando Python e DSS: Comparação entre Armazenamento Centralizado e Distribuído Abstract: This work analyzes the impact of battery energy storage allocation in distribution networks with distributed generation, comparing centralized and distributed strategies in terms of voltage violation mitigation. The study models a low-voltage distribution feeder with distributed photovoltaic generation, single-phase loads, and representative time-varying demand and generation profiles. To do so, it integrates quasi-static time-series simulations developed in Python with OpenDSS and formulates an optimization problem with discrete and continuous decision variables, solved through a genetic algorithm. The objective function seeks to minimize steady-state voltage violation indicators while considering technical constraints related to the size and placement of the storage systems. The results show that the insertion of distributed generation without storage worsens the electrical performance of the network, increasing the occurrence of overvoltages and expanding the violation indexes. The centralized strategy significantly reduces these problems, eliminating critical violations and substantially decreasing precarious violations, although residual violations remain. In contrast, the distributed strategy presents superior performance, fully eliminating the violations in the evaluated arrangements and providing more homogeneous voltage support along the feeder. However, the results also indicate that progressively increasing the number of batteries does not lead to proportional gains, which suggests diminishing marginal returns. It is concluded that distributed storage is more effective in ensuring voltage compliance, whereas the centralized solution provides relevant improvement with lower installed capacity. Fri, 20 Mar 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48680 2026-03-20T00:00:00Z