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Background: When a power system blackout occurs, it affects the economy of the country and every aspect of human life. Cascading failures can easily occur and cause a major blackout in the power grid due to the breakdown or failure of important nodes or links. Recently, transmission network reconfiguration (TNR) becomes a hot topic and has made many concerns after major blackouts of power systems. Aims: TNR is the second‐stage action plan to restore power systems and plays a major role in the process of power system restoration. On the other hand, grid resilience involves a quick dynamic reconfiguration of power systems to minimize the propagation of attack influences on the grid. The motivations to include the works in this survey are based on the quality of the research performed in the transmission network reconfiguration problem for grid resilience. In this article, the state‐of‐the‐art review of recent progress in the network reconfiguration problem of the transmission system for grid resilience is discussed with practical challenges, technical issues, and power industry practices. Materials & Methods: In this paper, complex network theory‐based indices with advantages, disadvantages, and their applications have been discussed to assess the important nodes and lines for network reconfiguration problem during sudden disturbances in power systems. Furthermore, optimization models have been presented with objective functions as well as their constraints. Taken together, optimization methodologies have been discussed to solve network reconfiguration problem with merits and demerits. Results: This survey paper presents current trends in research and future research directions concerning transmission network reconfiguration for academic researchers and practicing engineers. Furthermore, the most current studies in improving transmission network reconfiguration problem are reviewed by highlighting their advantages and limitations. Discussion: Based on a thorough comparison of literature some future perspectives are also discussed for transmission network reconfiguration problem for grid resilience. Conclusion: This review paper provides a comprehensive review of current practices applied to transmission network reconfiguration. The core focus of this paper will remain on complex network theory‐based indices, optimization models, optimization methodologies, challenges, and technical issues, and discusses future direction for transmission network reconfiguration problem for grid resilience. Furthermore, the most current studies in improving transmission network reconfiguration problem are reviewed by highlighting their advantages and limitations. [ABSTRACT FROM AUTHOR]

In recent days, the optimal allocation of distributed generators (DGs) problem in the distribution system caught several reader's attention to improve the system efficiency, to meet the future load growth. In this article, a multiobjective approach is proposed to determine the optimal locations for DGs, optimal DGs sizes, optimal power factors of DGs in the presence of optimal network reconfiguration to maximize the maximum loadability (λmax), minimize the active power loss and maximize the loading margin factor (λv) of the system. Butterfly Optimization (BO) algorithm is implemented to optimize the desired objectives. The Ɛ‐constraint method is used for multiobjective optimization, spanning tree technique is used for checking the radiality of the system and modified repetitive power flow using radial load flow algorithm is developed for finding theλmax, λv.The proposed approach is tested on 33 bus and 69 bus radial distribution test systems. Four scenarios are considered to achieve the desired objectives and each scenario consists of two cases: optimal allocation of DGs in the initial configured network, optimal allocation of DGs in the optimal reconfigured network. Results suggest that optimal allocation of DGs in scenario 4 gives a better improvement in maximum system loadability, loading margin factor, and active power loss reduction of the system. Obtained results compared with the suitable methods and algorithms that are available in the literature. [ABSTRACT FROM AUTHOR]

Summary: Reconfiguration of the distribution network (DN) is the changing of status of normally open and close switches for a specific purpose. In this paper, a situation is studied in which a fluctuating load (such as a welder) violates the network power quality (PQ) standards. Therefore, in order to mitigate the emission of the generated flicker, an optimization problem is developed for improving the PQ of the network comprising voltage flicker level and voltage profile in addition to the network power loss as a traditional objective of the DN reconfiguration. The optimization procedure is performed by changing the network configuration using tie and sectionalizing switches. Discrete particle swarm optimization is utilized to optimize the network configuration. The proposed method is evaluated in two DNs. IEEE standard 69‐bus DN and 95‐bus practical Iranian DN are considered as case study networks. The results show the effectiveness of the proposed method for improving the network PQ, especially in case of voltage flicker. The presented studies and procedure will guide the utility engineers in making decisions associated with the choice of reasonable mitigation technique to overcome the identified PQ problems. [ABSTRACT FROM AUTHOR]

One of the concerns of distribution network operators is the presence of harmonics in the network and their related issues. In most practical distribution networks, there is not enough information available about harmonic contents of customers for network operators. On the other hand, the changing nature of harmonic contents makes their evaluation more complex. Accordingly, in this article, for the first time, a new method for evaluation of harmonic distortion level is presented based on the IEEE‐519 standard. The method focuses on impedance characteristics of the network buses and uses the harmonic current and voltage limits, which are determined by the mentioned standard. The proposed method is utilized as harmonic constraint for network reconfiguration of IEEE 69‐bus and practical Iranian 95‐bus distribution networks. The results indicate the effectiveness of the proposed method for evaluation of harmonic distortion level in the distribution network. The proposed method can also be used as a useful tool in distribution networks where harmonic contents of nonlinear loads are not available. [ABSTRACT FROM AUTHOR]

Radial load flow (RLF) methods are frequently used in solving distribution system problems. The conventional Jacobian-based load flow methods (e.g., Newton-Raphson) may fail to converge in solving distribution system due to high resistance to reactance ratio of distribution lines. RLF methods are based on sweep-based mechanism and require that the line data must be arranged in accordance with network topology. This problem needs special attention particularly in case of solving dynamic power system problems, where topology of the network changes with tie switches position (network reconfiguration problem). This paper has presented an intelligent graph theory-based RLF analysis to solve 'dynamic' problems. The proposed algorithm will help in arranging line data for any combination of tie switch positions, to check the radiality of the system and to ensure that all nodes are connected with the source node. The effectiveness of the proposed method is also validated by solving 16-bus and 33-bus network reconfiguration problem using graph theory-based RLF method. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This study proposes a new strategy to solve the problem of radial power distribution system (RDS) reconfiguration in a multi-objective and constrained environment. Due to the presence of various conflicting objectives and constraints, the proposed strategy uses the Elitist Non-Dominated Sorting Genetic Algorithm-II (NSGA-II), an effective evolutionary multi-objective optimization technique. NSGA-II determines a set of pareto-optimal solutions for the power distribution system topology, considering power losses, reliability and investment in tie-switches. The methodology adopted to evaluate the RDS reliability uses a non-sequential Monte Carlo Simulation and is focused on the impacts of branch failures for interruption energy assessment. The effectiveness of the proposed methodology is demonstrated on a 69 bus RDS. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: In an electrical power system, the generated power is transferred through a high voltage transmission system, and it reaches the low voltage consumers at the distribution side. In a distribution system, I2R loss is very high compared with the transmission system due to high RX ratio, high current, and low voltage. It is a known fact that the economic enticement of distribution companies (DISCOMs) is to minimize losses in their networks. In general, this enticement is the difference in cost obtained between real and standard losses. Thus, when real losses are more than the standard losses, the DISCOMs are penalized economically, or when the opposite occurs, they earn a profit. Hence, loss minimization problem in distribution systems is a well‐suitable researched topic for researchers. Various approaches are investigated and implemented to solve the loss minimization problem in the past. However, these are different from each other by choice of loss minimization tool, problem formulation, methods employed, and the solution obtained. Several methods exist for loss minimization like capacitor allocation, network reconfiguration, distributed generation (DG) allocation, feeder grading, high voltage distribution system, etc. The present article gives a literature review, general background, and comparative exposition of the most often used techniques: (a) network reconfiguration, (b) capacitor allocation, (c) DG allocation, and (d) DSTATCOM allocation for loss minimization in distribution system and its combination versions for achieving maximum potential benefits are (e) simultaneous reconfiguration and capacitor allocation, (f) simultaneous reconfiguration and DG allocation, (g) simultaneous DG and DSTATCOM allocation, and (h) simultaneous reconfiguration, capacitor, and DG allocation based on several published articles. This will make the literature easy to new researchers working in this area. [ABSTRACT FROM AUTHOR]

Summary: Renewable energy sources are becoming popular day by day for distributed generation as technology is becoming cheaper and modular. Power loss reduction is a powerful incentive for a distribution system operator to promote distributed generation. This paper presents a method to minimize annual energy losses through the integration of nondispatchable renewable distributed generation (DG) units and network reconfiguration under varying load demand condition. The optimal location and DG power level are calculated, and then these data are used to determine DG plant size taking into account the nonavailability of renewable energy at certain times. A network reconfiguration strategy is proposed, which takes into account both the time‐varying load and the renewable energy source such that annual energy loss is minimum. The proposed methodology is applied to 33‐node and 118‐node test distribution system with different scenarios. Results show a substantial reduction in energy loss. A cost‐benefit analysis is also carried out. [ABSTRACT FROM AUTHOR]

Summary: The increase in the levels of penetration of distributed generation (DG) and the introduction of smart grid functionalities like network reconfiguration to the distribution network have made its fault current levels unpredictable and complicated the design of its protection. This paper studies the use of distribution grid code requirements, which regulate the fault response of DGs, to control the fault current levels in the network. The paper proposes an algorithm to follow when choosing the grid code requirements for DG dynamic voltage support that would allow for the continued use of traditional protection setups with sufficient speed and reliability; this would help avoid the need for more complicated schemes that heavily rely on an external communication layer that might negatively impact the reliability of the system. A motivating example is used to show that depending on the network configuration different voltage support requirements might be needed. By studying all possible configurations, a common range of requirements can be identified. The paper also considers changing the requirements progressively, such that requirements set for DGs currently connected can be different than those added in the future. This is demonstrated with a second case study where DGs are added in three phases. The results show that DGs added in later phases would need to be subject to stricter requirements than those connected in the initial phase. [ABSTRACT FROM AUTHOR]