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The increasing use of inverter‐based distributed generation requires a comprehensive study of its effects on fault analysis and the effectiveness of protection systems in distribution networks. This study examines the impact of different inverter control modes on multiple types of protective relay schemes. These include different overcurrent relay (OCR) schemes, both standard and nonstandard tripping characteristics, optimal coordination approaches, and different grid operation scenarios. The investigation is conducted through the utilization of grid‐connected and islanding operation modes, with fault resistance values of 0 and 5 Ω. The study is carried out on a 14‐bus CIGRE network which includes two photovoltaic (PV) farms with a capacity of 10 MVA each. The research provides several significant contributions, including the analysis of fault current contributions, examination of issues in OCR protection, investigation of the influence of fault impedance levels on OCR performance, evaluation of ideal coordination methods, and carrying out a comparative analysis utilizing optimization technique by using the water cycle optimization algorithm (WCA) and the particle swarm optimization algorithm (PSO). In addition, to guarantee the robustness of the suggested protection strategy, this work adopts a hardware‐in‐the‐loop approach. The OMICRON‐256 system is utilized to carry out real‐time testing on a SIPROTEC 7SJ62 multifunction protection relay, which validates the effectiveness of the proposed method in protecting microgrids under different PV control strategies. The total operating time for the nonstandard tripping scheme was 12.077–12.3003 s for PSO and WCA, respectively, while for the standard tripping scheme, it was 12.1226 and 12.1564 s. Moreover, these findings offer practical insights that can assist operators in effectively designing the power networks with grid‐connected PV systems by showing OCR miscoordination and no tripping events in power systems with PVs under inverters controllers. [ABSTRACT FROM AUTHOR]

This study introduces envelope- and machine learning (ML)-based electrical fault type detection algorithms for electrical distribution grids, advancing beyond traditional logic-based methods. The proposed detection model involves three stages: anomaly area detection, ML-based fault presence detection, and ML-based fault type detection. Initially, an envelope-based detector identifying the anomaly region was improved to handle noisier power grid signals from meters. The second stage acts as a switch, detecting the presence of a fault among four classes: normal, motor, switching, and fault. Finally, if a fault is detected, the third stage identifies specific fault types. This study explored various feature extraction methods and evaluated different ML algorithms to maximize prediction accuracy. The performance of the proposed algorithms is tested in an emulated software–hardware electrical grid testbed using different sample rate meters/relays, such as SEL735, SEL421, SEL734, SEL700GT, and SEL351S near and far from an inverter-based photovoltaic array farm. The performance outcomes demonstrate the proposed model's robustness and accuracy under realistic conditions. [ABSTRACT FROM AUTHOR]

Advent of distributed generation and progression towards an intelligent grid infrastructure within the domain of contemporary electrical power systems have created dynamic load profiles. Accompanying these developments, protective relays are faced with an evolving electrical load landscape and variable fault current conditions, resulting in disparate operational timings throughout the diurnal cycle. In light of these challenges, this paper delineates the formulation and simulation of a novel adaptive protection strategy for overcurrent relays, meticulously tailored to accommodate the fluctuations in electrical load. To construct a robust framework for this adaptive mechanism, a series of hypothetical fault current scenarios are meticulously crafted to activate the relays within the briefest time interval feasible. Further innovating within this sphere, this paper introduces a new hybrid algorithm, deftly amalgamating the strengths of three preeminent metaheuristic models: Improved Harmony Search, Particle Swarm Optimization, and Differential Evolution. Simulations and analyses substantiate the efficacy of the algorithm in optimizing the coordination among overcurrent relays aiming to uphold the overarching protective imperatives of the grid. For the IEEE 6‐bus system, the mean value of the objective function during 24 h in Monte Carlo is 292.6607 and very close to 272.0758 in the simulation of eight stochastic scenarios, which contributes to the validity of the approach in practical settings. Also, in the IEEE 30‐bus system, the results of the mean relay operation time set for the hours with the lowest and highest consumption load are 17.1297 and 14.8049 s, which reveals the increase in the operation speed of the relays. [ABSTRACT FROM AUTHOR]

Adding more power plants and transmission stations to the power system of Nigeria has been influenced by a substantial and rapidly growing nonlinear load demand over the past decades. This has resulted in an exponential increase in fault current due to complexity inherent in the Nigerian power system network. If not properly coordinated, this can lead to undesired tripping of the protection relays. Hence, it is crucial to ensure that relays installed in the grid can effectively detect and isolate fault current from both the upstream and downstream in order to maintain the integrity of the grid. To achieve this, an optimal Predictive, Analytical and Coordination Scheme (PACS) for over-current relays (OCRs) is introduced into the system. This paper provides a comprehensive examination of various optimisation techniques used for achieving PACS in the integrated power networks with review of literature on OCRs. The review emphasises the features, benefits and drawbacks of the techniques employed to address over-current protection coordination issues in a balanced and objective way. Additionally, the paper discusses potential avenues for future research in the field of PACS that could lead to significant advances in the field of optimal OCR coordination.

Power system fault diagnosis is crucial for identifying the location and causes of faults and providing decision-making support for power dispatchers. However, most classical methods suffer from significant time-consuming, memory overhead, and computational complexity issues as the scale of the power system concerned increases. With rapid development of quantum computing technology, the combinatorial optimization method based on quantum computing has shown certain advantages in computational time over existing methods. Given this background, this paper proposes a quantum computing based power system fault diagnosis method with the quantum approximate optimization algorithm. The proposed method reformulates the fault diagnosis problem as a Hamiltonian by using Ising model, which completely preserves the coupling relationship between faulty components and various operations of protective relays and circuit breakers. Additionally, to enhance problem-solving efficiency under current equipment limitations, the symmetric equivalent decomposition method of multi-z-rotation gate is utilized. Furthermore, the small probability characteristics of power system events is utilized to reduce the number of qubits. Simulation results based on the test system show that the proposed methods can achieve the same optimal results with a faster speed compared with the classical higher-order solver provided by D-Wave. [ABSTRACT FROM AUTHOR]

Nowadays, the problem of the coordination of relay protection systems during faults becomes widespread, as the trip of the circuit breaker must be fast. One of the solutions is the application of the Internet of Things. The object of this research is a relay protection system architecture, which uses elements of the Internet of Things and is based on open standards. The research aims to address the efficiency of using the Internet of Things in the relay protection systems, as well as the relevance of the proposed architecture. This architecture unifies processes encompassing relay protection, data collection, analysis, real-time communication protocols, and secure data transmission techniques. Apart from the increased quality of relay protection, it provides a well-organized framework for the precise and efficient acquisition, transmission, and analysis of data. As a result of the research, it was derived that the Internet of Things can be used in relay protection applications along with the proposed architecture if certain conditions are met. [ABSTRACT FROM AUTHOR]

This paper introduces a virtual consensus‐based wide area differential protection method through cooperative control concepts and graph theory. Using multi‐agent systems eliminates the need for a direct telecommunication connection between the protective relays to implement the proposed differential protection. In addition, applying telecommunication subgraphs facilitates the establishment of numerous differential protection areas. Collaboration between protected areas is facilitated by common agents, establishing a wide‐area cooperative protection network. The capability of the network operator to define various protection areas and the collaboration between these areas ensure the versatility of the proposed method for various protection purposes. The present paper primarily represents the application of the proposed protection system as a wide‐area supervisor protection for distance relays. Performance evaluations on an IEEE 39‐bus test system illustrate the method's effectiveness in various scenarios. The results show enhanced power system stability and resilience, particularly when traditional methods struggle to detect power swings with high impedance variation rates. [ABSTRACT FROM AUTHOR]

This article proposes a novel approach for the optimal coordination of adaptive directional overcurrent relay (ADOCR) for modernized active distribution system (ADS) with microgrid (MG) functions. The goal is to keep the coordinating circumstances while reducing the protective relay operation time, as much as possible. With the proposed round-off mixed-integer particle swarm optimization (ROMI-PSO), the setting parameters are not limited to only relay time multiplier setting (TMS) and pickup current setting (PS) but can include the discrete parameter as relay characteristic curve setting (CS). In the proposed framework, The CS can be both IEC and IEEE standard curves in the proposed framework. Four buses radial system and IEC-benchmark MG system were used in a number of simulation experiments. Comparing the suggested methodology to other current methods revealed that it is more effective at determining the minimum relay operating times and ensuring the proper operation of protections under various fault allocations and operating circumstances. [ABSTRACT FROM AUTHOR]

The paper presents some case spectral analysis of zero-sequence voltages and currents in an example industrial power distribution network. The network layout is based on typical power delivery networks in underground coal mines. Ground fault simulations have been made using an ATP/EMTP program. Due to the high environmental risks, the reliability of the protection relay operation related to their selectivity plays an important role. This paper tries to find the reasons for nonselective operation and unnecessary tripping in extensive mine cable networks, particularly with large power sources of higher-order harmonics. It was found that in transient states—due to the decaying oscillations occurring in complex RLC circuits—the results of short time measurements of the criterion values for ground fault protective relays can be overestimated (particularly for small values of ground resistance) and lead to nonselective tripping of a healthy cable line. Therefore, it might be advisable to increase the integration time used for measuring rms values. Also, if there is a significant level of higher harmonics in the industrial network generated by high-power converters, it should be noted that the higher harmonics of the ground fault current and currents measured by ground fault protection relays assume much higher values, which may also cause nonselective tripping. In this case, it may be advisable to use higher harmonic filters in the measuring circuits and to select a sufficiently high sampling frequency in the digital protective relays. [ABSTRACT FROM AUTHOR]

To ensure a stable and reliable power supply, the valid and timely response of protective relays are indispensable. Through the prevention of fault expansions, potential equipment damage or system collapse can be averted, where their setting is one vital prerequisite for such effective implementations. However, the increasing complexity of distribution power systems results in more challenges for protection tuning strategies. Ergo, this paper presents an ensemble that combines the independent factor evaluation (IFE) and quantum genetic optimization (QGO) models to further optimize the performance of relays according to their distributed tuning environment. In this ensemble, both near and far-end fault characteristics can be incorporated. In the first stage, the IFE dimensional reduction model is deployed for massive heterogeneous input data, where the statistical independence of input signals is calculated, the linear transformation matrix to decouple mixed signals is found, the linear combination of such signals is formed, and the non-Gaussian property to sort them is established. This can ameliorate the following calculation efficiency under those high-dimensional data scenarios. Subsequently, the QGO model is designed to further improve relay settings, where qubit representation is built to reduce required chromosomes, the linear superposition of the optimal solution probability in different states is implemented for a better diversity and convergence performance, and a self-adaption quantum gate is established to dynamically update the qubit chromosome groups and two-state solution combinations. Lastly, an empirical case study is presented, which validates the enhanced convergence, accuracy, and rapidity of the proposed ensemble. [ABSTRACT FROM AUTHOR]

Fuzzy and temporal reasoning can effectively improve the accuracy of fault diagnosis methods. However, there are challenges in practical applications, such as missing alarm messages, temporal reasoning with complex calculations, and complex modeling processes. Therefore, this study proposes an improved temporal fuzzy reasoning spiking neural P (ITFRSNP) system for power system fault diagnosis. First, the ITFRSNP system and its reasoning method are proposed to perform association reasoning between confidence degrees and temporal constraints. Second, a general fault diagnosis model and process are developed based on the ITFRSNP system to diagnose various faulty components and simplify the modeling process. In addition, a search method is provided for identifying suspected faulty components, considering the missing alarm message of the circuit breaker. Simulation results of fault cases demonstrate that the proposed method exhibits high accuracy and fault tolerance. It can precisely identify faulty components despite incorrect operations or inaccurate alarm messages of protective relays and circuit breakers. Moreover, the search method effectively narrows down the diagnostic scope without missing suspected faulty components in scenarios where alarms from boundary circuit breakers are missing, thereby enhancing the fault diagnosis efficiency. The fault diagnosis model features a straightforward structure and reasoning process with minimal computational complexity, making it suitable for real-time diagnosis of complex faults within power systems. [ABSTRACT FROM AUTHOR]

The untimely handling of faults in a power system has a negative impact on its operation and even the national economy, and this requires coordination in the functions of protective relaying as well as supervisory & control devices, where digital fault recorders are used to record fault waveforms of electrical physical quantities. The fault recording of a simulated current is taken as the research object in this article, and it is transformed from the time-domain waveform into a phase-domain trajectory, which is used to analyze fault feature parameters and then reformulate the waveform. The original waveform of the current will be substituted by the reformulated one with fault features to realize functions in the power system. The algorithm of reformulating fault recording, the correlativity of the reformulated waveform and its original one, and errors produced in the research process are researched. The high correlation coefficient between the reformulated waveform and its original one shows that the algorithm studied in the article offers a simple and convenient option for fault recording analysis. [ABSTRACT FROM AUTHOR]

The incorrect operation of protective relays and circuit breakers will significantly compromise the safety and stability of power systems. To promptly detect the faults of the relay protection system and the circuit breakers in time and to ensure the operational reliability of these protective devices, this paper proposes a fault tracing method for a relay protection system–circuit breaker based on improved Random Forest. Firstly, an analysis is conducted to identify the causes of incorrect operation of the protective relay and the circuit breaker. The fault types and corresponding alarm messages for the relay protection system and the circuit breaker are categorized, and the alarm feature set is constructed. Then, the Random Forest is improved and trained to develop the fault tracking model. Finally, the operation evaluation process is developed to determine the incorrect operations of the protective relay and the circuit breaker, and the fault tracking model and fault tracking process are then employed to locate the faults of the relay protection system and the circuit breaker. The experimental results demonstrate the method's capability to accurately track faults in the relay protection system and the circuit breaker, thereby assisting operation and maintenance personnel in troubleshooting and highlighting its promising practical potential. [ABSTRACT FROM AUTHOR]

Protective relays play a fundamental role in power systems, whose functions consist of three parts, namely protection, automation, and control, thus called the PAC altogether. It turns out that the architecture of a PACS (protection, automation, and control system) may exert a direct impact on the reliability of protective relay systems, previous studies of which are often conducted on the assumption that intelligent electronic devices (IEDs) have a constant fault rate with only mission reliability of the systems considered. To obtain a more accurate evaluation of system reliability bearing system maintenance in mind, this article proposes a novel method to appraise the reliability of PACSs with integrated consideration of basic and mission reliability. Firstly, the basic reliability of IEDs is calculated by parts count prediction, which will provide a more precise fault rate of IEDs. Secondly, the reliability of PACSs is analyzed by the reliability diagram and Markov model. By using the parts count prediction method to calculate the failure rate of the device, the steady-state probability rate will be accurate more than 0.0107%. At last, a quantitative criterion is finalized for selecting a suitable architecture easily. [ABSTRACT FROM AUTHOR]

The development of the relay protection based on open architecture is a relevant direction of electrical and electronic engineering. The paper presents the problem of the modern microprocessor-based relay protection that consists in the impossibility of the element replacement with alternatives from other manufacturers. The literature review on the reed switches application for relay protection, traditional and open-source solutions are given. Τhe structural scheme of the processes and relay protection device with different modules and the use of open-source communication and Industrial Internet of Things is demonstrated. The goal of the further research of sensibility, selectivity and reliability is set. [ABSTRACT FROM AUTHOR]

This paper presents a Monte Carlo method to solve the Optimal Coordination of Directional Over-Current Protections (OC-DOCP) considering transient configurations and all the possible Fault Locations (FLs). Previous methods cannot guarantee complete selectivity because they do not consider all the possible FLs. In the proposed method, near-end, and far-end faults are complemented by additional FLs, which are chosen from many randomly generated candidates (Monte Carlo method). Each FL candidate is included in the set of constraints at once to solve an OC-DOCP, whose results are the inputs for a simulator that assesses speed and selectivity indexes considering all the possible FLs. Thus, the FL with the maximum selectivity index is chosen to remain in the set of constraints for the next steps in an iterative procedure that finishes when the specified level of selectivity is reached. From the first iteration, the selectivity index obtained with the proposed method is substantially better than those obtained with the optimal solution of previous methods. The selectivity index is increased successively until it reaches practically 100%, without the need of including all the FLs in the set of constraints. Furthermore, an important improvement in the selectivity index is obtained without a significant worsening of the protection speed. The fact of solving many small optimization problems is an attractive feature of this method because facilitates the possibility of applying parallel computing to this problem. • Previous coordination methods consider few fault locations in the optimization model. • Optimal coordination with few locations does not guarantee complete selectivity. • The consideration of all fault locations in the model is computationally burdensome. • Monte Carlo is used to select a reduced set of locations that assure maximum selectivity. • A comparison with two existing solutions over the same case study is carried out. [ABSTRACT FROM AUTHOR]

• Faulted phases detection using backup method that is external to protective relay. • Validates integrity of input data using distributed ledger technology. • Tested using simulated faults in a realistic electrical substation test bed. Modern electrical grids have intelligent electronic devices (IEDs) such as protective relays that use internal logic to detect the types of electrical faults. The increasing integration of distributed energy sources and the resulting complexity of electrical grid communication architectures necessitates enhanced robustness of IEDs' monitoring while maintaining security against potential cyber threats. In this study, a backup electrical faulted phase detection method with a distributed ledger technology (DLT) platform was implemented. Cyber Grid Guard software was developed to collect phase currents and voltages transmitted through IEC 61850 GOOSE messages, detect faulted phases from the IEDs using the GOOSE data, and validate the data by hashing them and storing them in the distributed ledger. In this way, the hashed data were run into an electrical faulted phase algorithm based on using a current threshold for detecting the faulted phases in the medium-voltage main feeder of an electrical substation. The detection of the electrical faulted phases was assessed in a real-time simulator with protective relays, meters, the software framework, and DLT in the loop. The proposed method provides secure and reliable backup detection external to the IEDs, and DLT validation enhances system security and trust. [ABSTRACT FROM AUTHOR]

In bulk power systems, the majority of interaction between cyber and physical components takes place in substations. However, in most of the cyber–physical power system models the physical layer is typically done using the bus-branch (BB) model, where each substation is considered as a single node. This approach will not capture the details of the cyber layer. This paper proposes a framework to model the substations using node-breaker (NB) models for physical system representation so that the detailed station configurations, the current and the voltage transformer positions, arrangements of protective relays, bay control units and associated communication infrastructure within the substations and its dependencies on the physical elements can be captured effectively using a single cyber–physical graph. Keeping a transmission system operator in view, who does not use power flow and security assessment tools for station operations and maintenance, a vulnerability assessment approach is proposed to assess the risk using some representative attack scenarios. The proposed approach is demonstrated using WECC 3-machine system for breaker and half station configuration. The attack scenarios are developed based on the real substation configuration and the adversary's ability to understand the substation protection and BI/BO operations. • A framework to model detailed substation configurations as a cyber–physical graph. • Impact factors are proposed for assessing the consequence of cyber attack for TSOs. • Two attack models are discussed considering adversary's knowledge on the protection. • Proposed framework is implemented on WECC 3-machine system and results are presented. • Importance of securing IED placement info and of programmable BI/BO are highlighted. [ABSTRACT FROM AUTHOR]

Modeling protection devices in the Transient Stability Assessment (TSA) of power systems results in an accurate estimation of system stability and behavior. Miscoordination/misoperations of the relays and circuit breakers (CBs) result in higher order contingencies, > N − 1. Substation (SS) configurations and associated CB operations are usually ignored in TSA, even though the relays are modeled in detail. Replicating such scenarios needs manual fabrications in Bus-Branch (BB) models used in commercial TSA tools, which can be eliminated using Node-Breaker (NB) models. Also, incorporating relay algorithms, including the realistic CB operations and coordinating their timings, increases the complexity of the TSA code for large systems. The development of TSA tools to simulate the practical operation of CBs due to protective relay decisions similar to the physical substation operation is essential. This paper attempts in this direction. This paper uses a systematic approach to convert BB models to NB models. The Sparse Tableau Approach (STA) is used to represent the system in the NB model. It provides an algorithmic approach for automatically placing differential, distance and under/over frequency relays. It also gives programming logic to coordinate the timings between relays and the associated CBs. The program complexity increases with the size of the system as the number of CBs and the associated timers significantly increase based on the station configuration. The simulation results demonstrate the scalability and effectiveness of the proposed framework for the WECC 9 bus, New England 39 bus, and Polish 2383 bus systems. The WECC 9 bus system results are compared and validated with the commercial software PSS®E. • Transient Stability Analysis using Node-Breaker models, including relays and CB operations. • Automatic population of relays, associate CBs, and timers in substation configurations. • Time coordination between the simulation time step, relay trip time, and the CB operating time. • A comparison of the proposed framework for the WECC 9 bus system with PSS®E. • Case studies demonstrating the flexibility and scalability of the proposed framework. [ABSTRACT FROM AUTHOR]

• Improvement schemes for zero-sequence overcurrent and directional relayings of AC line are proposed to avoid the coupling influence of adjacent MMC-HVDC line. • Coupling characteristics of AC line to MMC-HVDC line on the same tower during normal operation and their influence factors are investigated. • Coupling influence between MMC-HVDC line and AC line on the same tower after DC or AC faults and its impact on protective relaying are analyzed. Significant coupling exists between DC and AC lines erected on the same tower or sharing transmission corridors. Electromagnetic and electrostatic coupling between DC and AC lines are investigated based on ± 500 kV MMC-HVDC and 500 kV double-circuit AC lines on the same tower. The interactive coupling characteristics and their impacts on protective relaying are analyzed during normal operation and after DC or AC faults. Voltage coupling ratio and current coupling ratio are defined. The 50 Hz components in MMC-HVDC line may be higher than ripple criterion under the coupling of AC line and can be even more significant when a fault occurs on adjacent AC line. The DC reactor with larger inductance can reduce its impact on MMC-HVDC system. Zero-sequence overcurrent relaying and zero-sequence directional relaying for AC lines may mal-operate when a fault occurs on adjacent MMC-HVDC line. And there is also an interruption risk for AC systems. Improvement schemes are proposed to avoid the mal-operation of protective relaying. Simulation case studies verify the correctness of coupling characteristic analysis and the effectiveness of proposed improvement scheme. [ABSTRACT FROM AUTHOR]

• Protection for inverter-based resources (IBRs) based systems has many challenges. • Developed superimposed quantity-based protection elements for a system with IBRs. • Protection elements are tested in a modified IEEE 9-bus system. • Evaluated system resilience with various maximum current limits in PV controllers. The increasing penetration of inverter-based resources (IBRs) to the power grid brings challenges to protection systems. IBRs may not provide sufficient fault current to trip protective relays, leading to delays in fault isolation and increased risk of equipment damage. To overcome the challenges, superimposed quantity-based elements are developed in this paper for transmission line protection in a power grid with IBRs. The characteristics of the designed protection system are tested under fault conditions in a modified IEEE 9-bus system that includes solar photovoltaic (PV) generation, and evaluated with different maximum current limits in solar PV controllers. The applied method in this paper makes contribution to the protection application for IBR-penetrated transmission systems. Simulation results show that the modeled protection system works effectively with different penetration of solar PV, and the system resilience is enhanced under fault conditions considering the tripping response and reclosing of circuit breakers. [ABSTRACT FROM AUTHOR]

• The complex magnitude-phase plane (MPP) of the fault detection index (FDI), is verified as a key indicator for fault detection in microgrid. • The magnitude and angle of the FDI is used to develope the proposed protective relaying logic. • The relaying scheme is extensively evaluated for variations in fault types, fault locations, fault resistances and distributed generation (DG) penetrations in grid-connected (GC) and non-grid-connected (NGC) modes of operation. • The algorithm is initially tested on MATLAB/Simulink platform and validated on Typhoon HIL platform to assess the real-time performance. • The test results and response time show promising performance in detecting faults. The paper introduces a novel protective relaying method using symmetrical components of current to detect asymmetrical faults in microgrid. This approach is focused on utilizing the complex magnitude-phase plane (MPP) of the fault detection index (FDI), which is computed using the positive and negative sequence components of the current signal retrieved at one end of the faulty line. The MPP obtained from the settling values of the FDI's magnitude (MFDI) and FDI's angle (AFDI) after the fault inception, is considered as the key indicator for fault detection. The scheme is comprehensively evaluated for a wide range of fault situations including variations in fault types, fault locations, fault resistances and DG penetrations in grid-connected (GC) and non-grid-connected (NGC) modes of operation. Several critical no fault cases are also tested to show the efficacy of the proposed logic for false operation. The fault study is conducted extensively on a modified low voltage standard Consortium for Electric Reliability Technology Solutions (CERTS) microgrid and a standard IEEE-34 bus distribution system including DGs. Furthermore, the proposed FDI-based scheme is tested on MATLAB/Simulink platform and validated on Typhoon HIL platform to assess the real-time performance. The test results show that this FDI-based scheme using the MPP concept can be a potent solution for the protection of microgrid. [ABSTRACT FROM AUTHOR]

• Detailed modeling of CIGRE-14 bus standard test system along with inverter control scheme (with and without grid code) and protection system is done in PSCAD environment. • The performance of directional relaying schemes (32Q and 67pos,67neg,67zero) are evaluated in the presence of inverter-interfaced renewable energy resources. A comparative study on the performance of the relays is done in the presence of inverter-interfaced renewable energy resources for different fault types and fault resistances. • The interdependencies between the inverter control scheme used and performance of relaying schemes have been analyzed through mathematical analysis and circuit realization of the inverter-interfaced renewable energy resources. • Based on the mathematical analysis and circuit realization, the probable causes of relay failures in the presence of inverter-interfaced renewable energy resources are detailed. • The impact analysis of the dynamic response of the controller on the protective relay settings from the perspective of protection operation time-frame has been attempted. The potential impacts of the inverter-interfaced renewable energy resources (IIRERs) on the performance of sequence-based directional relaying schemes (SBDRS) have been investigated in this paper. The directional overcurrent relays such as 67 POS , 67 NEG , 67 ZERO and 32Q have been considered for the investigation. CIGRE-14 bus system with IIRERs along with detailed modeling of inverter control scheme (with and without grid codes) and SBDRS have been done in the PSCAD environment. The mathematical analysis and circuit realization of the IIRERs have been attempted in the paper. The exclusive fault characteristics exhibited by IIRERs cause the conventional SBDRS to mal-operate. Significant change in levels of sequence currents and angular relationships between sequence voltages and currents during faults contributes to relay's unpredictable behavior. The comparative study based on different fault types, fault resistances and interconnecting transformer connections have also been done. The study reveals the impact of non-generalized angular differences between positive sequence voltage and current at the inverter terminal on performance of 67 POS. It is found that 67 NEG and 32Q mal-operated for all types of unbalanced faults while the 67 ZERO can be utilized for grounded fault with delta-star grounded connection of interconnecting transformer. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SFCLs) offer an efficient means of limiting fault currents and supporting system reliability. However, they weaken the fault characteristics and reduce the sensitivity of traditional relay protection. The seamless integration of SFCLs with protective relays remains a complex and under-explored area, impeding their widespread industrial adoption. In parallel, current differential protective (CDP) relays are almost the primary protection for all high-voltage electrical equipment and are the cornerstone of global power system security. This paper fills a critical knowledge gap by researching the intricate interaction between resistive superconducting fault current limiters (R-SFCLs) and current differential protective relays. Our investigation commences with a comprehensive mathematical analysis, while researching the influence of R-SFCLs on CDP operation. Subsequently, we conduct a series of comparative experiments using the Matlab Simulink software platform. These tests evaluate the sensitivity, dependability, and security of CDPs in scenarios with and without R-SFCLs. The simulation results not only confirm the accuracy of our analytical framework but also shed light on the multifaceted relationship between R-SFCLs and CDPs. This research contributes to a deeper understanding of how R-SFCLs can be effectively integrated into power systems, offering a roadmap for enhancing grid protection. • Innovative Integration and Mathematical Analysis: This study presents a comprehensive exploration and rigorous mathematical analysis of the challenges in integrating Resistive Superconducting Fault Current Limiters (R-SFCLs) with current differential protective relays (CDPs) in power systems. It revealed the relationship between these components, providing a theoretical foundation for their integration. • Simulink Experiments and Validation of Framework: Extensive comparative experiments conducted using Matlab Simulink offer practical insights into the behavior of R-SFCLs and CDPs under various fault scenarios. The simulation results validate the accuracy of the analytical framework, confirming its effectiveness in addressing key challenges such as fault current limitation and relay sensitivity improvement. • Practical Implications and Contribution to Grid Protection: The study offers practical recommendations for effectively incorporating R-SFCLs into power systems, enhancing grid protection without compromising the reliability and sensitivity of protective relays. It contributes to the field of electrical power and energy systems, providing insights with the potential to influence industrial practices and enhance grid resilience. [ABSTRACT FROM AUTHOR]

• The proposed detection method can detect the remanent flux accurately whether the CT is connected to the system or not. • The proposed method does not change the remanent flux and hardly affects the operation of the protective relays. • The factors that affect measurement accuracy are also discussed and analyzed. Protection current transformer (CT) saturation caused by the remanent flux will affect the performance of protective relays. The saturation can be suppressed by demagnetizing the iron core. Detecting remanent flux can make demagnetization more effective. This paper proposes a remanent flux detection method based on the fluxgate theory, which can effectively measure the magnitude and polarity of the remanent flux using the second harmonic of the current generated by a single-phase electronic inverter. The proposed method can detect the remanent flux without changing it, no matter whether the CT is connected to the power system or not, which means that this method can measure the remanent flux when the CT is under normal operating conditions. The effectiveness of this method is verified in EMTP-RV software, and the simulation results show that this method can detect the remanent flux with high accuracy. [ABSTRACT FROM AUTHOR]