Abstract
Protection and control systems represent an essential part of distribution networks, ensuring the physical integrity of components and improving system reliability. Protection devices isolate a portion of the network affected by a fault, while control devices reduce the number of de-energized loads by transferring loads to neighboring feeders. The integration of distributed generation has the potential to improve the continuity of energy services through islanding operation during outage conditions. In this context, this paper presents a multi-objective optimization approach for the size and allocation of protection and control devices in distribution networks with microgrids supplied by renewable energy sources. Reclosers, fuses, remote-controlled switches, and directional relays are considered in the formulation. The demand and generation uncertainties define the islanding operation and the load transfer possibilities. A genetic algorithm is presented to solve the allocation problem. The compromise programming is performed to choose the best solution from the Pareto front. Results show interesting setups for the protection system and viability of islanding operation.

Abstract
O sistema de distribuição de energia elétrica é a parcela do sistema de potência mais vulnerável aos eventos de interrupção, originados por fatores naturais externos ou intrínsecos aos equipamentos elétricos. Na mitigação dos impactos desses eventos, simuladores digitais em tempo real são utilizados na obtenção dos transitórios do sistema elétrico, todavia, essa técnica demanda grande esforço computacional. Nesse contexto, propõe-se uma técnica híbrida para simulação do transitório em sistemas de distribuição, combinando a alta taxa de amostragem dos modelos no domínio do tempo para monitoramento de tensão e corrente com a velocidade de processamento dos algoritmos que operam os modelos fasoriais em regime quase-estacionário, ou permanente. A metodologia proposta também permite considerar diferentes tecnologias de geradores distribuídos acoplados na rede. Os resultados dos testes realizados indicam a consistência da metodologia proposta, representando o comportamento do transitório no sistema de distribuição de energia elétrica. Todas as simulações realizadas são comparadas com valores amostrais obtidos usando um software comercial especializado.

Abstract
The sustainable development of power distribution systems must evolve into smart grids, where advanced automation with fast communication channels is essential. The analysis of their behavior uses the Hardware-In-the-Loop simulation for studying normal and critical operating conditions. In this work, we propose a hybrid technique for transient simulation in distribution systems by combining the high sample rate of the time domain models for voltage profile and electrical current monitoring with the processing speed of algorithms that operate the quasi-stationary, or permanent, phasor models. The proposed simulation platform is also based on the state of the art of standardized communication protocols of the power system. Its evaluation is performed using the comparison with specialized commercial software to assess the transient simulation. The time overcurrent protection function and the verification of messages exchanged between the simulator and the tested device highlights the applicability of the proposed methodology.

Abstract
Integration of distributed generation in power distribution networks provides many advantages and challenges to electric power system. Among challenges are the increase in levels of short-circuit currents and changes of power flow direction. These characteristics can interfere in the interruption capacity of protection devices, which are responsible for maintaining the integrity of distribution networks. Therefore, it is essential to understand the effects of distributed generation on protection systems to determine strategies that aim to solve the challenges imposed by this technology. The present work, first, proposes the mathematical formulation to coordinate overcurrent relays and fuse links, considering permanent and temporary faults. The solution is obtained through a dedicated genetic algorithm. Subsequently, this solution method is analyzed under different levels of penetration of distributed generators, allowing to identify points most susceptible to loss of coordination.

Abstract
This work proposes a method to calculate the short- circuit currents in unbalanced three-phase power distribution systems with distributed generation (DG) from non- and renewable energy resources. It takes into account the physical and operational features of four different types of DGs: synchronous, induction, photovoltaic and double-fed induction generator (DFIG). The DG formulations depend upon the connection type that can be directly coupling to the power grid or by using electronic converters or coupling transformers. The proposed method uses the bus impedance matrix with Kron reduction for each generator and superposition conception in the short-circuit current calculation. The results are achieved under a real-work unbalanced distribution network with 135 buses providing typical values of the short-circuit current that are compared with values from commercial software in the evaluation of the proposed methodology.

Abstract
Microgrids are promising to enhance power distribution systems' efficiency, quality, sustainability, and reliability. However, microgrids operation can impose several challenges to traditional protection schemes, like changes in the power flow direction and an increase in short-circuit currents. Microgrids can include several distributed generation technologies with different behaviours during short-circuit conditions, requiring additional protection schemes and devices. In this way, the optimized coordination of reclosers and fuses in distribution networks with directional overcurrent relays, which operate as interconnection devices, might overcome many imposed protection challenges. Regarding different generation technologies, voltage-restrained overcurrent relays and frequency relays are presented as local microgrid protection for rotative and inverter-based distributed generators, respectively. The optimized coordination of these protection devices maximizes microgrid benefits and minimizes operation drawbacks by reducing interruptions impacts and energy not supplied to consumers. This work proposes, thus, a mathematical model for the optimal coordination of protection devices in distribution networks with distributed energy resources operating in grid-connected and islanded modes. The minimization technique of operating times using an elitist genetic algorithm with variable crossover and mutation processes is proposed, as well. The results show adequate coordination using passive and low-cost protection devices.