Transmission lines connecting wind farms (WFs) to the main grid experience considerable variations in operating conditions due to changes in wind generation level, number of units in service (NUS), and network topology. These variations significantly challenge the dependability and security of conventional fixed Zone-2 distance protection, particularly when Zone-2 is employed as an overreaching element in teleprotection schemes such as permissive overreach transfer trip (POTT). This paper proposes a setting-group (SG)-based adaptive Zone-2 protection method for WF-connected transmission lines. The proposed approach maximizes Zone-2 fault coverage at both ends of the protected line while rigorously preserving selectivity with adjacent protection zones over a wide range of fault resistances, WF operating conditions, and network topologies, including N-0, N-1, and selected high-impact N-2 scenarios. A hybrid optimization framework is developed to simultaneously determine optimal Zone-2 quadrilateral characteristics for each available SG and to assign the appropriate SG to each operating scenario. To reduce computational burden, a systematic scenario-reduction technique is used to identify only those network elements whose outage significantly affects the relay-measured apparent impedance. Simulation results on a modified IEEE 39-bus test system demonstrate that the proposed method substantially improves Zone-2 coverage compared to conventional fixed-setting schemes. In particular, the method significantly increases the overlap of Zone-2 coverage between line-end relays, yielding marked performance gains for POTT-based protection while also enhancing protection dependability under non-teleprotected operation.

The growing participation of prosumers equipped with renewable generation and storage systems is reshaping distribution network operation. However, most existing studies treat technical and economic objectives separately, often neglecting coordinated demand response (DR) and reactive power management. This paper proposes a comprehensive optimization framework for the optimal placement and operation of prosumers integrating photovoltaic (PV), wind, and hybrid systems with battery energy storage (BESS). The model minimizes total operational cost by jointly considering power purchase and sale, distribution losses, battery degradation, curtailed renewable energy, reactive power penalties, and DR incentives, ensuring balanced techno-economic trade-offs. Furthermore, inverter-based PV and BESS units are leveraged for reactive power support and power factor improvement, while flexible EV charging is modeled as a time-shiftable load to enhance demand-side flexibility. The proposed framework is tested on the IEEE 33-bus distribution network under twelve scenarios combining variations in prosumer placement, DR participation, and reactive power pricing. Results show that coordinated prosumer integration with DR leads to a 50.5 % reduction in energy purchase costs and a 37.5 % drop in reactive power penalties compared to the base case. However, excessive active power injection degraded the network power factor below 0.5, highlighting the necessity of reactive-power control. Time-variable capacitor compensation at buses with high reactive loads (low power factor) effectively improved the network power factor above 0.9 and reduced the total cost by 52.6 %. The model also demonstrates that optimal placement of a limited number of prosumers achieves nearly the same performance as the unrestricted case, confirming its robustness.

Distance relays provide fast protection for transmission lines, but have limitations that require supplementary protection schemes to quickly clear main line faults detected beyond the first zone. This paper proposes a new protection scheme to enhance fault detection accuracy and prevent network instability when instantaneous operation of distance relays is not achieved. The proposed scheme can operate before the conventional backup protection using local protection units implemented in all substations. It identifies the fault between connected lines to the substation by analyzing the detection status of distance relays in local and first adjacent substations. Local protection units in nearby substations communicate with each other and with local distance relays via a telecommunication platform to execute protection algorithm. The fault detection algorithm estimates the likelihood of faults between connected lines by calculating the line fault probability index. This index is calculated by weighting factors assigned to adjacent distance relays using operation and expectation functions. This method remains effective even with telecommunication link failure and is robust against various network and equipment uncertainties. The implementation of fault scenarios on the IEEE 9 bus test system demonstrates that the proposed method is more effective than similar approaches under uncertainty conditions.

Changes in electric network topology, such as line outages, alter fault currents, potentially causing mis-coordination among protective relays. This paper presents an adaptive protection scheme for coordinating overcurrent relays (OCRs) and distance relays (DSRs) using setting groups. The proposed method adjusts group settings in response to line outages, employing a metaheuristic optimization algorithm to cluster possible network topologies into setting groups and determine optimal characteristic curves. Nested within this framework, linear programming algorithm solves a sub-problem to compute optimal time multiplier settings for OCRs. The objective function of the linear programming is designed to prevent the excessive clustering of topologies into a limited number of setting groups, addressing a common limitation of optimization-based clustering. Simulation results indicate that employing comprehensive settings across all network topologies either results in mis-coordination or significantly increases OCR operating times. In contrast, the proposed method achieves complete coordination across all topologies by optimizing characteristic curves, demonstrating superior performance over conventional approaches. Evaluated on the IEEE 8-bus and 30-bus test systems, this approach eliminates mis-coordination and markedly reduces the objective function value compared to existing methods, confirming its effectiveness for adaptive OCR-DSR coordination.

Distance relays are a crucial component of transmission network protection, and factors such as remote infeed make it challenging to ensure both security and dependability of the protection system. To address this challenge, this paper proposes an adaptive protection based on precalculated settings using the setting group (SG) capability of existing numerical distance relays. This scheme optimizes the zone-1 coverage of the relay in the R-X plane to include faults on the designated line as much as possible (dependability) while excluding faults outside the intended line (security). The paper considers the effects of different topologies (N-0, N-1, and specific N-2 topologies) and pre-fault line loads on the apparent impedance measured by the relay. Given these different topologies and line-loading scenarios, the total number of Network States (NSTs) can become significantly larger than the available number of SGs, making it impractical to assign a distinct SG to each NST directly. This necessitates mechanisms to group similar NSTs and assign an SG to each NST group. To overcome this challenge, a hybrid Particle Swarm Optimization-Binary Integer Linear Programming (PSO-BILP) algorithm is proposed. This algorithm simultaneously determines the optimum relay’s settings for each SG and identifies the proper SG to activate in each NST. The PSO component optimizes the relay’s settings, while the BILP component assigns the optimal SG for each NST. The effectiveness of this method is demonstrated through implementation and testing on the IEEE 39-bus network, showcasing significant improvements in the protection system’s performance.

Recent natural disasters and man-made attacks have imposed substantial challenges on power distribution companies and consumers. The integration of photovoltaic (PV) systems into power distribution networks has risen due to environmental, technical, and economic factors. Additionally, technological advancements have made it possible to provide reactive power using PV systems and battery energy storage (BES) systems. This article proposes a comprehensive framework for the optimal allocation of PV and BES systems within the power distribution system to minimize energy losses and energy not served (ENS) during normal conditions, as well as load interruption under emergency conditions. The framework models the formation of small microgrids, accounting for operational and physical limitations, coordinating them with the network recovery process, and considering various production and load scenarios to maximize the restoration of interrupted loads during emergency conditions. An analysis has been conducted to determine the penetration levels of BES in power distribution systems under these conditions. A Mixed-Integer Quadratic Programming (MIQP) formulation is employed for cost optimization, with the model coded in MATLAB and implemented on a modified IEEE 33-bus network. Results demonstrate that the proposed method significantly enhances the distribution network’s resilience during emergencies, achieving a 22.3% reduction in load interruptions and a 26.5% decrease in associated costs. Additionally, energy losses are reduced by 6.7%, while ENS improves by 7.2% compared to configurations optimized solely for normal conditions. This research underscores the importance of strategically integrating PV and BES systems to improve performance metrics in normal and emergency scenarios within power distribution networks.

Tele-protection schemes efficiently clear faults at line ends, but failures in the telecommunication link or relay malfunction can cause delayed fault clearance, network instability and significant power loss. Hence, this paper presents a reliable protection method as a backup for tele-protection schemes which is designed based on nearby distance relays zone pickup. The proposed protective method introduces a novel ability to adjust sensitivity to fault events through a security factor index. This method can adapt to network uncertainties or changes in topology, using one-step calculation of optimal values based on the least square error method and provides the fast adaptation to network changes. In addition, it enables the fault detection even if a relay fails at one of the faulted line terminals. Performance evaluation of the proposed method has been done based on the reliability indices through a wide simulation of fault scenarios on the IEEE 9-bus system. Considering the possible uncertainties, the test results have shown that the proposed method is more efficient with 98.5 % dependability compared to the conventional tele-protection schemes. While this index is evaluated at 90 % and 92.5 % in the PUTT and POTT schemes, respectively.

Fault location has significant importance in energy management system and has been used for many years. Recently, wide-area fault location using phasor measurement units (PMU) has attracted many attentions. However, measurement uncertainties decrease the accuracy of available methods. In this paper, a wide-area fault location method based on weighted maximum exponential squares (WMES) algorithm is proposed which has high robustness against measurement uncertainties. In this method, the measurements are weighted appropriately based on the uncertainty propagation theorem. Using WMES algorithm guarantees the robustness of the proposed method against bad data resulted from measurement uncertainty. In the previous methods, only voltage measurements are used in fault location; however, the formulation in this paper is developed to consider the current measurements provided by PMUs in addition to voltage ones for detecting the fault location. Results of simulation on the standard IEEE 57-bus network illustrates the efficiency of proposed fault location method based on the WMES compared to the other methods.

Severe hurricanes can inflict significant damages in the order of several times the common network failures on both the distribution companies and consumers. Network reconfiguration and condition-based switching are the common actions for enhancing distribution network performance in both normal and emergency conditions. In this paper, a novel approach is presented for simultaneous improvement in resiliency, reliability, and power losses. A practical strategy is proposed by considering the coordination between load restoration and repair of damaged lines in optimal switch placement problems. The use of both remote-controlled switches (RCS) and manual switches (MS) as well as considering practical constraints related to line repair and load restoration leads to the increased number of decision variables and consequently the degraded performance of meta-heuristic methods to obtain the global optimum solutions, especially for larger scale networks. Therefore, the proposed approach uses the exact method of MILP to solve the optimization problem. In this context, the uncertainty related to damage status and repair time of lines during High-Impact Low-Probability (HILP) events is the main challenge in linear modeling of the problem for which new methods are provided in the study. The programming is coded in MATLAB and tested on a modified IEEE 33-bus network.

Mobile energy resources (MERs) are equipment which are used to improve the resiliency of distribution networks after natural disasters. An important point about using these resources is optimal routing and scheduling them to supply essential loads. In this paper, to make the problem more actual, a new formulation considering limited fuel for the trunks that move these energy resources is presented. Then, refueling vehicle is used to lessen the effect of limited fuel. Therefore, an optimization algorithm is presented for optimal allocating refueling vehicle, simultaneously optimal routing and scheduling of limited-fuel MERs. In the next stage, to achieve a better result and reducing the restoration time, a new formulation is presented for prepositioning MERs considering the stochastic occurrence of damages in various points of the network. Latin hypercube sampling method is used as scenario reduction method to implement the stochastic problem formulation. To illustrate the efficiency of the proposed method considering limited fuel for MERs, refueling vehicles, and MERs prepositioning, simulations are carried out on IEEE 33-bus test system and the results are compared with the previous studies' results.

Optimal use of mobile generators can significantly improve resiliency of distribution system. Optimal use means, determining the location and power generation by each of the generators during period of the network outage. There have been some articles about usage of mobile resources so far, but none of these articles have addressed the issue of limited fuel for trucks. In this paper, this limitation is taken into account, and it will be shown that with this assumption, the solutions to the problem will depart from the optimal solution. In order to reduce the effect of this limitation, a network of mobile fuel vehicles has been introduced, which will be determined by each site's optimization and refuelling program. Finally, it will be shown that the solutions to the problem will come closer to the optimal solution when considering a mobile fuel vehicle. In order to show the effectiveness of the proposed solution, it will be tested on 33-Bus IEEE test system with considering daily variables of loads.

The optimal selection of cable's cross-section in distribution networks reduces capital investment costs and network power loss. One of the important points in cable size selection process is taking the damage curve into account, which this curve depends on the type, insulation, and cross-section of cable. The cross-section should be selected in such a way that the cable can withstand short-circuit current until the fault is cleared. In conventional methods, damage curve is considered in optimal cable size selection (OCSS) process with assuming fixed times for fault clearing. In this paper, it is shown that this assumption makes two main issues: interference of cable's damage and overcurrent relay's characteristic curves in some branches, and unnecessary increase in capital investment costs in other branches. To overcome these challenges, a new method is proposed for solving OCSS problem using overcurrent relays coordination as sub-problem to obtain variable fault clearing times. The relays are coordinated with the worst-case conditions to ensure that network changes will not affect the results of OCSS in future. The results show the effectiveness of proposed method with the aim of capital investment costs reduction, and also interfering prevention between the cables damage and overcurrent relays characteristic curves.

Reconfiguration of distribution network with consideration of voltage stability index (VSI) in the presence of distributed generation (DG) is a time consuming and complicated problem, which needs considering various technical constraints. Hence, in this paper a novel formulation based on the mixed integer linear programming (MILP) is proposed. Several linearization methods have been used to present a linear VSI. Network reconfiguration based on MILP not only increases accuracy and pace of solving, but also guaranties the optimal solution. Minimizing real power loss and improving VSI are the objectives of this problem. In addition, some constraints like branches currents, nodal voltage limits, radiality of distribution network, and penetration level of DGs are determined. In order to evaluate the performance of algorithm, the proposed method is tested on 33-bus and 69bus radial network. All scenarios are simulated linearly and non-linearly in GAMS.

The phenomenon of Fault-Induced Delayed Voltage Recovery (FIDVR) appears in networks with high penetration of induction motor loads because the increase in requested reactive powers of motor loads after clearing the fault prevents the rapid return of the bus voltage to the pre-fault level. Load shedding is one of the effective ways to deal with the FIDVR phenomenon, which causes the amount of demand to approach the production of reactive power. In this paper, a wide-area load-shedding method is presented, which performs based on network conditions and loads. Since the introduced indicators for determining the locations and amounts of loads to be shed are based on the values of bus voltages, loads currents, and network impedance matrix; therefore, the proposed method can effectively shed the loads and deal effectively with FIDVR. The voltage estimation process is an important tool to predict the voltages at future moments and is defined based on the modified Gauss-Seidel load flow and the three-order model of the induction motor. This tool enables the proposed method to understand the effect of applying load shedding on voltage recovery and prevents the application of unnecessary ones.

Fault-induced delayed voltage recovery (FIDVR) phenomenon refers to delayed voltage recovery after the occurrence of a fault on the transmission level, caused by the presence of induction motor (IM) loads at the distribution level. Load shedding (LS), which reduces the imbalance of the requested and generated power in the network, is one of the most effective ways to deal with the FIDVR. This paper proposed a wide-area LS strategy based on the voltage estimation process. At first, a process for online voltage estimation is presented using three-order model of IM and modified Gauss-Seidel load flow. This process is used to identify FIDVR-involved buses and verify the calculated amounts and locations of loads to be shed. These variables are calculated through a repetition-based optimization problem, linearized and converted to mixed-integer linear programming form to reduce calculation time. The proposed LS strategy is implemented on the IEEE 118-bus network and the simulation results confirm the efficiency of the proposed method compared to previous ones. The proposed strategy could mitigate the critical FIDVR of all buses with less load to be shed from fewer buses.

The fault-induced delayed voltage recovery (FIDVR) and short-term voltage instability (STVI) phenomena appear in networks with high penetration of induction motor loads because the increase in requested reactive powers of these loads prevents the voltages from quickly returning to their pre-fault levels. Load shedding (LS) is one of the ways to deal with FIDVR and STVI and reduce the imbalance between the generation and demand of reactive power. Under-voltage (UV) relays that disconnect loads during voltage drop cannot effectively deal with this phenomenon because of their inability to detect the effective loads on the reduction of FIDVR and STVI severities. Therefore, the operation of UV relays during these phenomena causes unnecessary load disconnection, and the interference of their operations with FIDVR and STVI must be avoided. This paper presents two wide-area approaches based on network and loads parameters, the first of which deals with the most critical FIDVR, and the second tries to simultaneously handle critical FIDVRs of all buses. Also, bus prioritization for LS during STVI has been addressed. Simulation results revealed the better performance of the proposed approaches than the previous ones in terms of the amount of LS and the number of selected buses for LS.

Load shedding can be used to compensate for some imbalance between the generated and requested powers in order to deal with destructive effects of fault-induced delayed voltage recovery (FIDVR) phenomenon. This paper presents a load shedding method to deal with critical FIDVRs based on an online voltage estimation process for faster voltage recovery. The voltage at future time can be estimated by modifying the Gauss-Seidel load flow in addition to proper modeling of the dynamic nature of induction motor loads. The voltage estimation process is presented based on one and three-order models of induction motor loads, indicating that the use of three-order model for FIDVR studies leads to better results. The hypothetical step-by-step load shedding is applied in the proposed iterative load shedding method, and the voltage estimation process is used for its verification. All estimated voltages of buses need to meet non-critical conditions to send the actual load shedding command to the network. Comparing the results of the proposed method with previous ones on the IEEE 118-bus network shows its effectiveness in mitigating critical FIDVRs by suggesting less load to be shed in less time.

Fault ride through (FRT), one of the main requirements of the distribution networks, led some generators to be disconnected from the network after a short time. Such incidents in the distribution network with the high penetration of wind plants cause power failure and reduce reliability. To investigate these problems, the FRT requirements of the wind turbine generator are considered part of the objective function of the relay’s coordination. So, when relays are coordinated using optimal settings, the time duration allowed for fault clearing is also considered. This paper presents a method to accelerate relay operation by establishing a telecommunication connection between the relays to prevent the disconnection of wind turbines from the network. This aim is accomplished by transferring the FRT diagram from the voltage-time plane to the current-time plane of each relay, taking into account faults with different resistances. Then the relay diagram and the transferred FRT diagram are compared, and the relay diagram must be placed under the transferred diagram. The fault condition results illustrate that many relays with the new setting improve the FRT capability. For verification, the proposed method has been implemented on IEEE 8-bus and 30-bus ring networks.

Fault-induced delayed voltage recovery (FIDVR) occurs after a fault in a network with high penetration of induction motor (IM) loads. Load shedding (LS) is one of the appropriate methods to reduce the destructive effects of FIDVR on the network, and for this reason, the authors have previously presented three LS methods to deal with FIDVR. The first method uses the index of IM loads’ power change. The second method is an optimization problem and the third method introduces indicators based on sensitivity analysis to find the location and amount of LS. The purpose of this paper is to examine the strengths and weaknesses of those three methods, and to determine each of these methods is suitable for use in what specific conditions. The proposed methods obtain less LS amounts, also, the number of LS locations and moments of proposed methods are fewer than previous ones. However, these methods have different execution times which are related to the speed of utilized processor, and a suitable method to deal with FIDVR must have the ability to shed the load in the initial moments of this phenomenon.

We directly demonstrate, for the first time, the small pixel effect in an amorphous photoconductor by measuring the intrinsic transient response of an amorphous selenium (a-Se) photoconductor pixel of various sizes monolithically combined with a CMOS sensor. Our front-end circuitry leverages the lowest electronic noise reported for aSe photon detection, $\sim 300 \mu \text{V}_{rms}$ measured, to demonstrate the first-ever fully CMOS integrated a-Se pulse heigh spectroscopy results. Fabricated using $0.18 \mu \text{m}$ CMOS mixedsignal technology, the chip contains four pixel arrays with 30, 60, 90, and $120 \mu \text{m}$-pitch, each pixel having its own dedicated charge-sensitive amplifier. Our measured results from a monoenergetic Gamma source demonstrate the capability of a-Se/CMOS pixel arrays to achieve a high count rate when the small pixel effect is leveraged in the high spatial resolution pixel arrays. The results demonstrated can expedite the development of energy discriminating single photon counting imaging detectors for large area mammography tomosynthesis and dedicated breast computed tomography, something that has not as yet been achieved at the commercial scale.