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In the current scenario, the principle of penetration of electric grid delivery generation technologies is being rigorously applied. With the inclusion of distributed generation sources within the network, the short circuit MVA capacity of the electrical distribution network increases. The variation in short circuit current levels would depend on the network layout, DG sizing, and the DG placement. The discrimination time period associated with the pair of main and backup relays is breached because of the variation in short-circuit current levels. Thus, with the presence of distributed generation, coordination between main and back up relay's malfunctions. The relay settings should therefore be properly updated in every region of the power system. By choosing the Optimum time dial setting (TDS) and pickup current or plug setting, an optimum setting of Overcurrent Relay coordination (OCR) coordination can be achieved. The Elephant herding algorithm (EHA) is suggested to overcome the optimum overcurrent relay coordination without sacrificing the characteristics. The impact of penetration of various Distributed Generation sources on Over-Current Relays in the 33-test bus distribution system has been observed from the simulation outcome and analysis, and the optimal relay settings as well as the usefulness of the proposed algorithm in locating optimal coordination of over-current relays. [ABSTRACT FROM AUTHOR]

In this study, a hybrid algorithm that focused on the water cycle and moth flame (WCMF) algorithm to solve the optimal relay coordination problem in a Microgird has been proposed. In the hybrid WCMF algorithm, the spiral movement of the moth is incorporated in the basic water cycle algorithm (WCA) to increase its performance. Further, the Levy flight function has been added to explore the randomization of the current hybrid model. Due to the Levy flight, the hybrid WCMF algorithm tremendously improves its performance. The competency of the latest hybrid WCMF algorithm is examined in a microgrid to optimize the Time Dial Setting (TDS). An optimum TDS reduces the total operating time of relays installed in the microgrid. A minimum total operating time provides fast protection and enhances the reliability of the network. In this proposed work, the total operating time is obtained only 7.728 s. which is reduced by 66.69%, 59.75%, and 18.52% respectively over the PSO, WCA, and ERWCA techniques. Besides, the proposed techniques obtained this fine results with less control parameters, fewer iterations, and less computational time. Therefore, the hybrid WCMF algorithm is the best tool to enhance microgrid protection coordination compared to the existing techniques. [ABSTRACT FROM AUTHOR]

Relay coordination is reliable and crucial to guarantee that healthy feeders are properly isolated from the defective areas in a microgrid network. An appropriate protection scheme must be properly planned during the design of the microgrid to ensure safety for the power components in the event of a failure. The implementation of distributed generators in the microgrid changes the total network’s Load-Flow and often impacts the magnitude and direction of the fault current. Using the nature-inspired novel evaporation-rate-based water cycle algorithm (ERWCA), the enhancement in microgrid protection is accomplished in this work by optimizing the relay settings, reducing their operation time and time dial setting of each relay. The approach proposed is validated with the IEC microgrid benchmark system and the findings are contrasted with current techniques. It is found that the proposed strategy produces substantial improvement for the microgrid in the application of over-current relays and greatly reduces the relays’ overall net operating time. [ABSTRACT FROM AUTHOR]

This article proposes the optimal coordination problem of protective relays within a hybrid optimisation framework which is presented based on integer coded genetic algorithm (ICGA) and non-linear programming (NLP). The optimal coordination problem of directional overcurrent relays (DOCRs) is implemented while aimed at finding the optimal plug setting multiplier (PSM) and time dial setting (TDS). In this respect, PSM is a function of the current transformer (CT) size and the tap of the relay which is discrete in nature. TDS is a function of the operating time of the relay for different short-circuit currents at different locations of the system. Here, the variables of the problem are decomposed into continuous and discrete variables. The first stage of the problem uses the ICGA to determine the size of CTs considering the permitted tap of relays while the second stage utilises the NLP method to evaluate the feasibility and optimality. The presented framework is then simulated on an 8-bus test system. The obtained results verify the effectiveness and the applicability of the optimisation technique to find the optimal settings of DOCRs.

In this study, an adaptive continuous wavelet transform (CWT)‐based overcurrent protection for smart grids is proposed to enhance the overcurrent protection performance encountering high‐impedance fault (HIF) and current transformer (CT) saturation, which are extremely complex phenomena and their impacts often cause mis‐coordination or mal‐operation. The proposed algorithm samples three phase current waveforms and imports them to CWT to extract high frequency coefficients. Afterwards, the sum of absolute values of the coefficients, Scoef, is calculated for each sample during the last cycle. Meanwhile, several simulations related to HIFs with different impedances and CT saturations with different severities are executed and the fault currents and the sum of absolute values of the coefficients are achieved and saved in the relay memory as (X, Y) coordinates of points (IL‐fault, SL‐coef), named 'learning data'. Thereafter, each Scoef is imported to the X −Y plane and, consequently, the occurrence of HIF or CT saturation is detected and the real‐fault current is estimated by both non‐linear interpolation and extreme learning machine approaches. Subsequently, new time dial setting and Ipickup of the relays are computed and reloaded. Security, dependability, and sensitivity of the proposed adaptive protection method are confirmed by numerous simulation studies. [ABSTRACT FROM AUTHOR]

The coordination of directional overcurrent relays (DOCRs) in meshed power grids with multiple sources is a constrained optimization problem, which has been stated in recent literature as linear (LP), nonlinear (NLP), and mixed-integer nonlinear programming (MINLP) problem. In this paper, the DOCR coordination NLP problem is reformulated as an equivalent quadratically constrained quadratic programming (QCQP) model, leading to significant reduction of problem complexity. Another contribution of this work is the systematic problem statement using graph theory concepts. The proposed method is applied to three different meshed power systems, employing state-of-the-art optimization software. Simulation results demonstrate the efficacy and superiority of the proposed QCQP model over the prevailing NLP approach. [ABSTRACT FROM AUTHOR]

The modern power system networks are very complex and often consist of multiloop structures with increased penetration of renewable energy sources‐based distributed generations. Directional overcurrent relays (DORs) are the key protection devices in such networks and their coordination has a profound impact on the overall protection of networks. Optimisation of DOR settings is an important concern in protection coordination in power systems. In this study, optimisation of DOR settings, namely time dial setting and pickup current (Ip) setting is achieved by adopting symbiotic organism search technique which is a recently proposed proficient optimiser imitating biological give and take policy while searching for an optimum. Computational ability of the technique to coordinate DORs is validated in IEEE 6‐bus and WSCC 9‐bus test systems. Results show that the new technique causes for notable reduction in relays' operating time, with maintaining reliable coordination margin for each primary/backup relay pair, in comparison with other techniques. Also, computation time to find optimum solution is less using the new method. [ABSTRACT FROM AUTHOR]

This study presents a hybrid gravitational search algorithm‐sequential quadratic programming (GSA‐SQP) algorithm based on the GSAand SQP to optimal coordination of directional overcurrent relays (DOCRs). The SQP routine is incorporated in GSA as a local search mechanism to improve the performance of the conventional GSA algorithm. The coordination between DOCRs is formulated as a non‐linear and highly constrained optimisation problem in which two settings namely time dial setting and pick up current setting of each relay are considered as decision variables. The main objective is to minimise the sum of operating times of all the primary relays, which are expected to operate in order to clear the faults of their corresponding zones. Performance of this approach is studied and evaluated on three different test systems with 6, 24 and 38 relays. Simulation results show that the proposed approach provides effective and robust high‐quality solution of the problem. [ABSTRACT FROM AUTHOR]

In this article, the enhanced backtracking search algorithm is employed to achieve optimal coordination of directional over-current relays. A novel objective function is formulated to minimize the total operating times while maintaining the validity of the coordination time interval. The proposed technique is applied to optimize the influential variables of the coordination problem, which are plug tap setting, time dial setting, and type of inverse relay characteristics. Both old electromechanical and digital relays are considered in the study. The enhanced backtracking search algorithm is a recent heuristic-based optimization, and its performance in solving relay coordination problem is compared with other well-established algorithms to demonstrate its viability and effectiveness. [ABSTRACT FROM PUBLISHER]

An effective coordination in an interconnected system can be obtained by ensuring proper settings of overcurrent relays. In this research work, the problem of coordinating the overcurrent relays is formulated as a non‐linear problem, taking into account the as discrete nature of time dial settings and the pickup current settings. An effective approach based on adaptive differential evolution (ADE) algorithm is proposed to solve the coordination problem. The results obtained by ADE are compared with different algorithms on different model test systems and found to be feasible, robust and efficient. [ABSTRACT FROM AUTHOR]

This paper presents optimal coordination of over-current relays by using improved harmony search method (IHS). The objective function of the relay coordination problem is to minimize the operation time of associated relays for given fault conditions in the protection system. The control variables used in this paper are the pickup current and the time dial setting of the relays. The proposed method was tested with 5-bus, WSCC 9-bus and standard IEEE 14-bus test systems. For benchmarking, sequential quadratic programming (SQP) and genetic algorithm (GA) were employed to solve this optimal relay coordination problem. The results showed that the IHS is capable to minimize the operation time of relays in the entire system. As a result, all search algorithms can solve optimal coordination relay which the improved harmony search method gives the best solutions for optimal coordination relay setting. [ABSTRACT FROM AUTHOR]