This paper elaborates a new protection scheme based on dual-setting DOCRs for automated distribution networks. In this course, the reduction in relays operation time saturates as the number of these relays increases. Thus, optimal deployment of dual-setting DOCRs should be specified in an efficient manner. To do so, a multi-objective optimization approach is established which compromises the reduction of total operation time and the number of dual-setting DOCRs. Coordination constraints are accommodated and non-standard inverse-time characteristics are established to intensify flexibility of the proposed strategy. The proposed model lies within a non-linear programming fashion which is tackled by particle swarm optimization (PSO). Moreover, the augmented -constraint approach is utilized to reach the Pareto-optimal solutions following which the fuzzy decision making process determines the best compromised solution. Detailed simulation studies are carried out to interrogate performance of the proposed approach.

Clearing power grid faults swiftly and selectively offers higher security, reliability and sustainability. Accomplishing this aim by deploying directional overcurrent relays (DOCRs) is one of the major challenges in meshed and multisource distribution networks. To overcome this challenge, the current study elaborates a new coordination strategy which concentrates on minimising overall operation time of relays. In this strategy, an auxiliary variable is added to classical operation time model of each DOCR. All the auxiliary variables are considered as coordination constraints which help to yield new and well‐defined time current characteristics (TCCs). In other words, more flexibility is attained in adjusting relay's characteristic which helps to alleviate clearing time of faults. The obtained TCCs can be easily performed by numerical relays. In addition, a new objective function is defined to steer the relay settings towards optimal solutions conveniently. It was shown that the proposed approach not only reduces the operation time of relays, but also prevents miscoordinations. This approach demonstrates a non‐linear programming model tackled by particle swarm optimisation algorithm. The effectiveness of the proposed approach is verified via 8‐bus and IEEE 14‐bus test systems and results are discussed in depth.

Keeping selectivity among protective devices in electrical grids is of crucial importance. This task in the combinatorial protection scheme of distance and directional overcurrent relays (DOCRs) stands as a complicated problem, especially in interconnected networks. To overcome this issue, this paper proposes an enhanced protection coordination (PC) scheme by employing dual time‐current characteristics (D‐TCCs) for overcurrent relays which are followed by two inverse‐time curves in series. These characteristics simplify the complexity of the problem and yield higher flexibility and extensibility in PC process which helps to meet selectivity requirements. However, these characteristics can be implemented by numerical DOCRs which poses investment costs. Therefore, a techno‐economic optimal replacement model is devised to attain a least‐cost numerical DOCRs deployment plan while eliminating miscoordination and minimizing total operation time of the relays. Furthermore, inverse‐time curves of DOCRs are selected optimally among available options for conventional relays. By doing so, the attained flexibility is intensified which lessens imparted economic burden through alleviating the replacement level of numerical DOCRs. The proposed approach calls the need for making amendments in coordination points to handle coordination problem in the case where both conventional DOCRs and numerical DOCRs with D‐TCCs are present. Therefore, coupled with the conventional selectivity constraints, the constraint associated with new coordination points are all together accommodated in the optimization process. The proposed model demonstrates a mixed integer nonlinear programming fashion which is solved with sine‐cosine algorithm. Several numerical studies are carried out to interrogate the validity of the proposed approach. The obtained results are encouraging.

This paper unveils that maintaining a proper voltage protection for inverter-based distributed generations (IBDGs) using overcurrent relays and during the power grids’ faults with considerable resistance stands as a complicated issue. To overcome this challenge, this paper presents a new protection scheme through developing a voltage index (VI) and launching a new characteristic that concentrates on minimizing energy-not-supplied (ENS). If the developed voltage index is in place, the near area faults with considerable resistance could be effectively discriminated from those at a far distance. Moreover, the adopted characteristic represents two operation modes known by fast and slow modes. For the faults in the vicinity of the IBDG, independent from resistances, the fast part of the proposed characteristic and VI are jointly corresponded to clear the faults swiftly. Moreover, to satisfy coordination time interval (CTI) among relays pairs, the slow part acts in the conventional manner which is corresponded during the backup process. To evaluate the performance of the proposed method, numerical studies are carried out on IEEE 33-bus test system. Results show that the ENS index is enhanced while meeting IBDGs’ voltage protection requirements and satisfying selectivity tasks.