HV substations equipment protection as a strategic point on the power network always has attracted attention of power planners. An increase in the generation capacity and interconnected operation of neighboring grids can result in an increase in the fault currents during a contingency in a power system. The increased fault currents may exceed the maximum fault current rating of existing protective apparatus. Therefore FCLs are used which perform switching operations quickly and safely in the event of a power system fault. This study proposes a methodology for determining the location of FCL by considering the reduction of fault current and the reliability indices according to the location of FCL in a conventional arrangement such as one breaker and half. Finally, the fuzzy decision method which is suitable for solving problems with no advantages respect to each other to determine the optimal location of FCLs is used.

Voltage surges are sudden and short-term increases in voltage that can potentially damage electrical equipment, cause data loss, or disrupt operation. Surge voltage mitigation is crucial for the reliability of power systems and the protection of sensitive electronic equipment. By implementing effective surge protection strategies, power system operators can minimize the risk of damage and improve the overall stability of the electrical infrastructure. In this paper, the surge voltage caused by an evolving close-in fault in the 20 kV busbar of a sub transmission station is investigated. According to the results of the measurements made by recorders at the location of the substation, the reason for happening of the incident is elaborated. Using a simulation by PowerFactory software (DIgSILENT/2022 version), the occurred disturbances and relevant cases are investigated. Focusing on the role of shunt capacitor banks, the necessary solutions to mitigate the surge voltage are presented and their effectiveness are analyzed with the help of simulation

Presence of Distributed Generation (DG) in electric distribution systems provides an attractive new alternative in capacity expansion planning of these systems. In this paper a new model is developed for solving simultaneous placement of HV/MV substations and DG units as a static planning tool. This model aims to minimize fixed and variable costs of planning. Constraints related to DGs, substation and network are incorporated in the developed model. Proposed model can be used for optimal sizing, sitting and defining associated service area of HV/MV substations and DGs in distribution capacity expansion. The proposed model is a mixed-integer nonlinear mathematical model which optimized using genetic algorithm. The effectiveness of proposed model is illustrated through numerical examples.

Resonance and ferroresonance in power systems are categorized as two destructive phenomena especially in HV networks which their occurrence are being initiated in consequence of a power system event. Also, Ferroresonance phenomenon may be initiated by non-power system event such as lightning strike. Hence, the study of resonance and ferroresonance requires an exhaustive evaluation of possible network events in different network configurations. In each event, the analysis of network voltages is conducted based on identified allowable limits by IEEE 519 standard as an evaluation critera. In this paper, a novel comprehensive study approach is proposed for study of ferroresonance phenomena in power networks. The proposed approach comprises different steps including substation equipment modeling, EMT simulation of the probable switching events, evaluation of correspondence results, and finally detecting the probable ferroresonance occurrence. Furthermore, a novel approach for resonance study is also presented. Voltage and current limits are implemented to define an impedance criteria for performing resonance evaluation of network buses. Findings – The proposed method is implemented for study of resonance and ferroresonance in all HV substations of the Khuzestan regional electricity network. By performing the proposed evaluations, the probable condition which may lead to resonance and ferroresonance occurrence are identified. The results are highly valuable for network operators in prevention of unintended overvoltages occurrence.

To design a safe substation grounding grid, it is necessary to compute the split factor for earth fault current and also current distribution in other possible paths. In this paper, a novel, simple and accurate method is developed for determination of this factor. In the proposed algorithm grounding grid impedance of adjacent substations, dissimilar tower footing resistances, different parallel circuits, more than one earth wires and different spans in transmission lines can be considered. In addition, the formulation for the earth faults through line towers is presented.  Finally, the results are compared with the addressed cases that are comparable and show good agreement and accuracy.         

The concept of complex fuzzy sets is a generalization of ordinary fuzzy sets. In this paper, we introduce the concept of complex fuzzy subhypergroups (Hv-subgroups) as well as the concept of complex anti-fuzzy subhypergroups (Hv-subgroups). We investigate their properties and their relations with the traditional fuzzy (anti-fuzzy) subhypergroups (Hv-subgroups), and we prove some results in this respect.

A larger class of algebraic hyperstructures satisfying the group-like axioms is the class of Hv-groups. In this paper, without any condition and in general, we de ne the Hv-normal subgroup and the Hv-quotient group of an Hv-group. We introduce the fundamental equivalence relation of an Hv-quotient group and prove the  rst and third isomorphism theorems for Hv-groups.

Using the notion of "belongingness (e)" and "quasi-coincidence (q)" of fuzzy points with fuzzy sets, we introduce the concept of an (a, b)- fuzzy Hv -ideal of an Hv -ring, where a, b are any two of {e, q, e Vq, e Aq} with a¹e Aq. Since the concept of (e,e Vq)-fuzzy Hv -ideals is an important and' useful generalization of ordinary fuzzy Hv -ideals, we discuss some fundamental aspects of (,e Vq)-fuzzy Hv -ideals. A fuzzy subset A of an Hv -ring R is an (e,e Vq)-fuzzy Rv-ideal if and only if an At, level cut of A, is an Hv -ideal of R, for all t e (0,0.5]. This shows that an (e,eVq)-fuzzy Hv-ideal is a generalization of the existing concept of fuzzy Rv-ideal. Finally, we extend the concept of a fuzzy subgroup with thresholds to the concept of a fuzzy Hv-ideal with thresholds.

The number of Hv-structures, defined on a set is extremely big and gives the chance to applied sciences to work in an opposite to usual direction. Thus one asks from applied sciences to give all restrictions they have, because they reduce the number of possible Hv-structures expressing their problem, by a mathematical model. Moreover, the way of treating Hv-structures gives some new proving methods which can be used in applications. This is the main reason that the Hv-structures have so many applications. Here we present an overview on applications of Hv-structures on other sciences as in Hadronic Mechanics, Lie-Santilli admissible, leptons, biology, teaching, education, and mathematics itself, as well.