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In this research paper, an adaptive and intelligent protection scheme is developed that brings selectivity and sensitivity to the conventional overcurrent relays considering the changes in grid topologies, changes in grid operation modes, and changes in short-circuit behavior due to the contributions from distributed energy resources in the medium-voltage distribution grids. A quasi-static medium-voltage benchmark grid model is used in the Python-based power system tool pandapower. Definite-time overcurrent relay devices are extended with a communication signal-based tripping scheme suitable for a decentralized communication architecture. Current phasor angles are compared between two primary relays and the result is fed into a tripping logic to achieve selectivity of the primary protection. Furthermore, communication between the primary and backup relays is established, extending the communication signal-based tripping scheme. It analyzes in which cases the proposed communication-based protection scheme's ability to isolate the faulty section after short-circuit events is comparable to conventional schemes based on distance relays that require additional voltage measurements or differential relays that require dedicated high-speed communication. Therefore, the pre-existing and installed communication capabilities can be used to avoid the need for additional measurement hardware or communication technology. [ABSTRACT FROM AUTHOR]

Abstract Microgrids (MGs) can enhance the consumers’ reliability. Nevertheless, besides significant outcomes, some challenges arise. Regarding the intermittent nature of Renewable Energy Resources (RESs), MGs are not operated radially. Accordingly, the reliable protection of MGs considering uncertainty in RESs is crucial for planners and operators. This paper uses data analysis to extract knowledge from locally available measurements using RMS values of symmetrical components. The learning-based characteristic of the suggested technique with a low computational burden exempts the need for an available communication infrastructure in the MG. The Support Vector Machine (SVM) technique is applied to train the Intelligent Electronic Devices to have a reliable MG protection scheme. The proposed method, which performs fault detection and classification together, just requires local information and functions effectively to discriminate faulty from normal conditions considering different uncertainty of resistance faults. Digital simulations on an MV test network were conducted to construct an appropriate database to consider some aspects of uncertainty in the network. The various faults considering their uncertainty, the different modes of operation, the uncertainty of RESs generation, and the load levels are combined to produce myriad scenarios. The simulation results confirm the effectiveness of the proposed adaptive protection approach in accurately distinguishing different system modes and consistently protecting the MG, achieving an accuracy rate of 99.75%. Furthermore, it offers the MG an optimal protection scheme that is not limited by selectivity constraints across diverse conditions.

The electrical protection of active distribution networks is crucial for ensuring reliable, safe, and flexible operations. However, protecting these networks presents several challenges due to the emergence of bi-directional power flows, network reconfiguration capabilities, and changes in fault current levels resulting from the integration of inverter-based resources. This paper introduces an innovative protection strategy for active distribution networks, leveraging the principles of distributed coordination and multi-agent systems. The proposed strategy consists of two stages. The first stage involves a fault detection algorithm that relies solely on local measurements, while the second stage uses agent classification to compute the optimal operating time based on a dynamic matrix representation of the fault path, combined with a simplified distributed optimization problem. The coordination process is formulated as a set of linear optimization problems, simplifying the solution. The proposed protection strategy is validated in a real-time simulation environment using a modified CIGRE MV European grid as a case study, considering low-impedance symmetric fault scenarios and topological changes. The results demonstrate that the protection scheme exhibits robust performance, enhancing the adaptability of the protection equipment while ensuring suitable sensitivity and operational speed. [ABSTRACT FROM AUTHOR]

Increasing distributed generations (DGs) penetration and their plug & play operation challenge the protection coordination of distribution networks due to variable fault current levels. Adaptive protection schemes as a great solution are used to cope with DGs connection status, where the DGs statuses are transmitted to relays via communication links to activate the appropriate Setting Groups (SGs). In this paper, a new hybrid protection scheme is introduced where it is composed of relays with SGs and inter-trip links to develop more sensitive adaptive protection. In the first stage, a sensitivity index is introduced to find the critical constraints and form a set of candidate relays. Then, a new method is proposed to assign the SGs and inter-trips according to the inter-trip effect on coordination restoration. Inter-trips restore the coordination with reducing primary relay operating time reduction, whereas SGs delay the operation of the backup relays. Optimal coordination of the proposed hybrid scheme is simulated on the IEEE 30 Bus distribution grid and compared with other schemes. The results indicate that the proposed hybrid scheme is a more efficient tool to improve the performance of the protection scheme under plug & play operation of DGs achieving lower fault clearance times. [ABSTRACT FROM AUTHOR]

This review paper provides a systematic examination of differential protection schemes in microgrids, particularly focusing on configurations with electronically coupled Distributed Energy Resources (DERs). It consolidates research findings to delineate the challenges and operational complexities introduced by DERs in microgrid protection. The review dissects a variety of approaches ranging from conventional methods to sophisticated data-driven and selective phase-tripping strategies. In doing so, it identifies the gaps in current technologies and underscores the need for evolution in protection schemes to cater to the dynamic nature of microgrids with inverter-based resources (IBR) domination. The paper highlights the shift towards adaptive and intelligent protection mechanisms that promise improved fault detection, isolation, and system resilience. By offering a comprehensive analysis of existing literature, this paper underlines the critical role of differential protection in maintaining microgrid integrity and reliability in the face of growing IBR penetration. Its contribution lies in presenting a cohesive narrative on the progress and prospects of IBR-dominated microgrid protection, serving as a foundational resource for advancing research and practice in this evolving domain.

Design and selection of advanced protection schemes have become essential for reliable and secure operation of networked microgrids. Various protection schemes that allow correct operation of microgrids have been proposed for individual systems in different topologies and connections. Nevertheless, protection schemes for networked microgrids are still in development, and further research is required to design and operate advanced protection in interconnected systems. Interconnection of these microgrids in different nodes with various interconnection technologies increases fault occurrence and complicates protection operation. This paper aims to point out challenges in developing protection for networked microgrids, potential solutions, and research areas that need to be addressed for their development. First, this article presents a systematic analysis of different microgrid clusters proposed since 2016, including several architectures of networked microgrids, operation modes, components, and utilization of renewable sources, which have not been widely explored in previous review papers. Second, the paper presents a discussion on protection systems currently available for microgrid clusters, current challenges, and solutions that have been proposed for these systems. Finally, it discusses the trend of protection schemes in networked microgrids and presents some conclusions related to implementation.

Substantial differences in fault levels between grid-tied and islanded modes is one of the primary challenges of microgrid protection. During grid-tied mode, the bulk grid provides significant short-circuit, while during islanded operation the short-circuit magnitude is small due to inverter-based resources limiting their current output close to nominal ratings. Consequently, conventional distribution protection strategies based on overcurrent cannot reliably protect microgrids when operating in islanded mode. Fuses and circuit breakers are particularly affected because of their inverse characteristics. Presently, the absence of affordable solutions for protecting microgrids in islanded mode leads to microgrids shutting down during electrical faults. The contribution of this article is two-fold. The first innovation proposes specific hardware modifications to grid-forming inverters to increase their short-circuit current during electrical faults. The second innovation introduces a novel control strategy designed to preserve control stability margins even when the grid-filter saturates, ensuring sinusoidal output currents under normal and fault conditions. Through experimental results, the inverter with the proposed modifications can provide more than three-times its nominal current during electrical faults. For the prototype testbed, this was sufficient to enable the use of traditional legacy overcurrent protection, achieving the fuse-to-relay and relay-to-relay minimum coordination time for the line-to-ground, line-to-line to ground, and three-phase electrical faults.

Abstract The operational performance of conventional overcurrent protection relay coordination connected to a distribution network is adversely affected by the penetration of distributed generators (DG) at different buses in the network. To address this problem, this paper proposes a novel adaptive protection coordination scheme using a radial basis function neural network (RBFNN), which automatically adjusts the overcurrent relay settings, i.e., time setting multiplier (TSM) and plug setting multiplier (PSM) based on the penetration of DGs. Short circuit currents and voltages measured at different buses are acquired using the remote terminal units (RTU) connected to different buses within the terminal network. Communication between the various remotes and local end station RTUs is through hybrid communication systems of fiber optic and power line communication system modules. The new adaptive overcurrent protection scheme is applied to the IEEE 33-bus distribution network with and without DGs, for single and multi-DG penetration using both the ETAP and MATLAB software. The simulation results show the proposed scheme significantly improves the protection coordination.

Protection relays that incorporate advanced microprocessors are vital to electrical grids, providing fast and reliable responses to faulty conditions using efficient communication protocols. Instant detection and response to various faults are essential to minimise the risk of damage. Numerical relays can identify faulty conditions and trigger circuit breakers to open, thus preventing further damage to the system. Due to the lack of autonomous decision-making capabilities, existing numerical relays require manual reconfiguration in situations such as a change in network configuration and protection settings. These relays also do not have the ability to coordinate fault clearance when multiple sources supply power to the grid. A comprehensive overview of the research aimed at developing a multiagent system (MAS)-based adaptive protection relay will be provided by dividing it into separate articles such as firmware and hardware. This first part delves into the firmware aspects of this innovative relay, highlighting its adaptive capabilities and key considerations in its development. The second part will provide detailed design descriptions for the hardware features of the relay. An STM32MPU multicore advanced microprocessor is utilised to design and develop the adaptive numerical relay firmware. It incorporates several protection relay ANSI codes, communication protocols, and MAS-based adaptive protection schemes as part of the firmware.

The deterministic directional overcurrent relay (DOCR) coordination approaches find limitation in providing fast and reliable protection to today's distribution networks due to growing integration of distributed generations (DGs). In this paper, an adaptive DOCR protection coordination scheme is proposed using an efficient optimization algorithm called the dragonfly algorithm (DA). The main inspiration of the proposed DA optimization technique originates from static and dynamic swarming behaviours of dragonflies. In this approach, the dominant changes in the network topologies are identified by monitoring the status of the circuit breakers connected at the terminals of the DGs and other main power components. When any dominant changes in the network topologies or operating modes are identified, the fault current for that particular condition is calculated and the new optimal DOCRs settings for the prevailing condition are obtained from the substation central computer in online mode. The comparative results with the existing approaches justify the superiority of the proposed scheme in achieving the minimum overall relay operating time and maintaining the coordination between the primary and backup relay pairs. In the proposed adaptive protection scheme, the average percentage reduction in the overall operating times of DOCRs in the 6-bus and the IEEE 14-bus test systems with different levels DG penetration is found to be 49.7% and 15%, respectively, compared to the existing approaches. [ABSTRACT FROM AUTHOR]

With the continuous development of society, the requirements of enterprises and the public for the reliability of the power system are also improving, and the fault identification and protection action of the distribution network is conducive to the comprehensive analysis and overhaul of the line, which is of great significance. In this paper, a short-circuit fault identification method for distribution networks based on artificial intelligence technology is proposed to categorize and predict power system faults using an association rule algorithm. Then, a distribution network adaptive protection strategy based on the equivalent impedance of the distributed energy system is proposed, which real-time adjusts the setting value and criterion of the protection through the distribution network containing distributed energy devices connected to the grid and adjusts the working status in normal operation, realizing that the current protection of the distribution network adapts itself to the change of the working conditions of the distribution network system of IIDG. Simulation results show that when two-phase grounding and three-phase short-circuit faults occur in the distribution network under the protection of the adaptive system. The protection circuits start instantaneously in 0.005s, which realizes the functions of the fast startup, self-sustained operation, and controllable shutdown when faults occur in the distribution network. Meanwhile, the feasibility of the scheme is verified by utilizing the system to output short-circuit faults in the case of IIDG grid-connected or off-grid when the respective integrating values are greater than the positive sequence short-circuit current values.

The structure and connections in networked microgrids consisting of two or more interconnected microgrids is influenced by the dynamic behaviors of power markets, the demand and supply interactions between market participants, and the possibility of operating in the grid-connected or islanded modes. Protection zones in the above-mentioned scenarios are dynamic and should not be determined a priori. Also, fault currents will vary depending on the operating modes, online or offline status of Distributed Energy Resources (DERs), variation of solar irradiation or wind speed, etc. This paper proposes a Centralized Intelligent Station-Level Protection (CISP) approach for the protection of various electric power equipment technologies in networked (interconnected) microgrids using adaptive protective relaying algorithms and a network theory-based zone selection algorithm. The proposed CISP approach utilizes wide area IEC 61869-9 Sampled Values (SVs) measurements and IEC 61850 Generic Object-Oriented Substation Events (GOOSE) messages, intelligently determines the protection zones, and automatically selects the protection algorithms to use in each of the protection zones based on the prevailing system topology and operating conditions. The effectiveness of the proposed CISP approach is demonstrated through real-time simulations using the RTDS®. The results obtained were promising for the various system configurations, operating conditions, and fault conditions considered. [ABSTRACT FROM AUTHOR]

The various configurations that exist for a compatible circuit depend on an object, such as operating conditions, the occurrence of an inter-circuit error and the result of the coupling of the transmission line. This feature makes the protection of the same transmission lines very difficult. This paper introduces a new algorithm based on a state diagram that contains location data collected on a passing bus. Combine the different separation processes and the impedance-based process is used. The classification process cannot detect internal errors and only compares with existing phases where the same regional error occurs in the 2D space and the impedance-based method used to cover the resulting error. The proposed algorithm incorporates impedance-based methodology and separation technology to provide the appropriate response under all operating conditions of the same circuits. [ABSTRACT FROM AUTHOR]

The development of modern power systems is directly related to changes in the traditional principles of management, planning, and monitoring of electrical modes. The mass introduction of renewable energy sources and control devices based on power electronics components contributes to changing the nature of the flow of transient and quasi-established electrical modes. In this area, the problem arises of conducting a more accurate and rapid assessment of the parameters of the electrical regime using synchronized vector measurement devices. The paper presents an extensive meta-analysis of the modern applications of phasor measurement units (PMUs) for monitoring, emergency management and protection of power systems. As a result, promising research directions, the advantages and disadvantages of the existing approaches to emergency management, condition assessment, and relay protection based on PMUs are identified. [ABSTRACT FROM AUTHOR]

In last few decades, microgrid has emerged an interesting and intelligent approach by containing its prospective framework using smart grid protocols. One of the technical issues in implementing microgrid in smart grid environment is to design a distinct protection scheme with the ability to meet the protection requirement in all modes of operation. The motive for this study is to address a technical outlook in protection strategies of microgrid and the challenges to achieve them. Initially, the currently existing protection techniques of AC microgrid followed by DC microgrid are discussed. Since the conventional protection technique cannot be used in DC microgrid directly as there's no zero crossing in DC systems and bidirectional power flow, it needs more attention in proposing a protection strategy for DC. Therefore, this leads to the innovation of adaptive protection in microgrid where the implementation of communication infrastructure makes the system smart. Thus, this paper focuses on detailed literature on protection scheme for AC and DC microgrid. [ABSTRACT FROM AUTHOR]

Protection relays that incorporate advanced microprocessors are vital to electrical grids, providing fast and reliable responses to faulty conditions using efficient communication protocols. Instant detection and response to various faults are essential to minimise the risk of damage. Numerical relays can identify faulty conditions and trigger circuit breakers to open, thus preventing further damage to the system. Due to the lack of autonomous decision-making capabilities, existing numerical relays require manual reconfiguration in situations such as a change in network configuration and protection settings. These relays also do not have the ability to coordinate fault clearance when multiple sources supply power to the grid. A comprehensive overview of the research aimed at developing a multiagent system (MAS)- based adaptive protection relay will be provided by dividing it into separate articles such as firmware and hardware. This first part delves into the firmware aspects of this innovative relay, highlighting its adaptive capabilities and key considerations in its development. The second part will provide detailed design descriptions for the hardware features of the relay. An STM32MPU multicore advanced microprocessor is utilised to design and develop the adaptive numerical relay firmware. It incorporates several protection relay ANSI codes, communication protocols, and MAS-based adaptive protection schemes as part of the firmware. [ABSTRACT FROM AUTHOR]

This work provides a detailed protection analysis of a fast, Traveling-Wave (TW), Machine-Learning (ML), local, non-directional, economic, and setting-less protection scheme. The goal is to provide an objective evaluation of how a data-driven TW protection scheme would perform when deployed on a power distribution system as a faster alternative to over-current (OC) protection. Fault simulations consider scenarios from none to high-penetration of renewable energy resources to show its suitability for future applications on Distributed Energy Resources (DER)-dominated distribution systems. A modified IEEE 34 node system with solar Photovoltaic (PV) in multiple locations is modeled in PSCAD/EMTDC. The TW, ML method’s protection scheme is built upon an efficient signal-processing stage, using the Discrete Wavelet Transform, and scaled-down Random Forest models that classify the fault location into several protection zones. The analysis is focused on the quantification of the sensitivity and selectivity of the proposed protection scheme. Furthermore, estimations of the false trip probability and average unnecessary load loss are included, as these events may occur due to the misoperation and miscoordination of the proposed data-driven, signal-based relays. Results show high TW detection rates and fault location accuracies, which cause a small and bounded percentage of imprecise fault locations and unnecessary load loss. Similarly, the same IEEE 34 node system is modeled in OpenDSS and a custom OC protection scheme is designed. The comparison between both methods leads to the conclusion that TW, ML methods can be a significantly faster aid to traditional protection.

Increasing the penetration of renewable energy sources as distributed generation in modern power grids presents several challenges, including voltage level issues and protection system failures resulting from bidirectional power flow and changing network dynamics. Voltage limit violations could potentially damage the utility equipment and lead to power quality problems. Innovative Volt/VAr control methods, such as tap staggering, can be used to overcome these problems. Tap staggering utilizes circulating current between parallel transformers to provide reactive power absorption from the network. However, the absorption of reactive power by the primary substation using tap staggering poses a potential risk to the protection system, particularly the Directional Overcurrent protection scheme with Load Blinder. This could lead to failures or nuisance trips during normal load conditions. In this study, a real power system is modeled using real data in PSS CAPE with 120 scenarios generated through tap staggering application, all based on 24-hour demand/wind generation data. The Tap Staggering Macro and Adaptation Protection Macro were developed for the purpose of analyzing these scenarios. The study demonstrates that tap staggering effectively mitigates overvoltage issues on the transmission system by absorbing reactive power. Although there is an increase in active power losses when tap staggering level is increased on the parallel transformers, the power loss remains within reasonable limits. Despite its benefits, tap staggering has been found to affect the Directional Overcurrent with Load Blinder protection scheme, limiting power transfer generated through wind turbines in the distribution network. This results in changes to the protection scheme’s Directional Overcurrent Pickup, Load Blinder Resistance, and Load Blinder Alpha parameters, requiring adaptation in all scenarios. After adaptation, the protection system operates reliably, guaranteeing efficient and unrestricted transmission of distributed generation power to the grid.

Electrical distribution companies have been investing in modernizing their structures, especially operation automation. The integration of information technologies and communications makes fast power restoration during fault events, providing better profit to companies and a more reliable and safe distribution network for customers. A self-healing strategy can be implemented for protection and control devices to work cooperatively, achieving the global purpose of automatic distribution system restoration. Thus, this work proposes a methodology for short-circuit fault detection, isolation of the faulted section, and restoration of downstream sections using neighbor feeders. The protection devices use standardized IEC and ANSI/IEEE functions to sensitize faults in the system and to promote adequate isolation, allowing the consequent restorative process. A genetic algorithm optimizes the devices' parameters used in the protection scheme, making fastest the isolation process and ensuring the protection system coordination and selectivity. Results obtained using Simulink® allows for verifying the proposed methodology's behavior and efficiency. [ABSTRACT FROM AUTHOR]

Adaptive protection schemes have been developed to address the problem of behavior-changing power systems integrated with inverter-based generation (IBG). This paper proposes a machine-learning-based fault detection and classification technique using a setting-group-based adaptation approach. Multigroup settings were designed depending on the types of power generation (synchronous generator, PV plant, and type-3 wind farm) connected to a transmission line in the 39-Bus New England System. For each system topology, an optimized pretrained ensemble tree classifier was used. The adaptation process has two phases: an offline learning phase to tune the classifiers and select the optimum subset of features, and an online phase where the circuit breaker (CB) status and the active output power of the generators are continuously monitored to identify the current system topology and to select the appropriate setting group. The proposed system achieved an average accuracy of 99.4%, a 99.5% average precision, a 99.9% average specificity, and a 99.4% average sensitivity of classification. The robustness analysis was conducted by applying several fault scenarios not considered during training, which include different transmission network configurations and different penetration levels of IBGs. The case of incorrect selection of the appropriate setting group resulting from selecting the wrong topology is also considered. It was noticed that the performance of developed classifiers deteriorates when the transmission network is reconfigured and the incorrect setting group is selected. [ABSTRACT FROM AUTHOR]

Online adaptive protection scheme provides an appropriate protection to microgrids for various fault conditions irrespective of bidirectional power flow and changing network topology in a grid-connected or islanded mode of operation. The success of this scheme can, however, be undermined as a result of the operational uncertainties caused by the failure in various components in protection system: namely, communication links and circuit breakers. This paper proposes a framework for assessing the impact of such uncertainties on the reliability of centralized adaptive microgrid protection schemes. It first derives appropriate Markov chain models to describe the dynamic uncertainties associated with lines, communication links, and circuit breakers. The Markov models are then used in a Monte Carlo algorithm to evaluate the reliability indices for an adaptive protection scheme. The proposed framework is tested on a sample microgrid in Simulink-Matlab and Java Agent DEvelopment platform, assuming that the respective communication middleware is carried out by multi-agent and communication simulator. It has been shown that the selection of communication technology in an adaptive protection scheme requires special attention to its failure rate and data transmission bit error as well as data transfer speed. In fact, communication technologies with high failure rate and bit error show poor reliability indices that can cause unwanted delays in fault clearance, particularly when GOOSE time sequence latency is considered in the analysis. Besides, an increase in the fault duration can increase the electromagnetic and thermal stresses inflicted on circuit breakers, further undermining the reliability of the protection system. [ABSTRACT FROM AUTHOR]

The bidirectional power flow, voltage/frequency dynamics, and reduced fault current observed in microgrids pose significant challenges to the protection of electrical systems. Particularly, the dynamic nature of microgrid-distributed energy generation requires protection schemes to adapt dynamically. Distributed protection strategies are commonly found in the literature, with adaptive protection based on multi-agent systems (MASs) being one of the most promising methods. This solution offers high autonomy, fault tolerance, and robustness against multiple fault types under various topology scenarios. This paper presents a systematic review of the current advances in MAS-based adaptive protection systems for AC microgrids. Furthermore, a discussion on the strategies implemented in MAS-based adaptive protection, the most used development frameworks for designing, developing, and testing MAS-based solutions for AC microgrid protection, and limiting factors for the widespread adoption are presented. Finally, open research problems and future research trends in MAS-based adaptive protection are also presented in this research. • Adaptive protection based on multi-agent systems (MAS) is a promising solution. • Advances in MAS-based adaptive protection systems are systematically reviewed. • MAS-based design and simulation for AC microgrid protection are included. • A lack of contributions focused on real-time performance features is noted. • MAS-based strategy's burden reduction of communications systems is also concluded. [ABSTRACT FROM AUTHOR]

Adaptive protection is defined as a real-time system that can modify the protective actions according to the changes in the system condition. An adaptive protection system (APS) is conventionally coordinated through a central management system located at the distribution system substation. An APS depends significantly on the communication infrastructure to monitor the latest status of the electric power grid and send appropriate settings to all of the protection relays existing in the grid. This makes an APS highly vulnerable to communication system failures (e.g., broken communication links due to natural disasters as well as wide-range cyber-attacks). To this end, this paper presents the addition of local adaptive modular protection (LAMP) units to the protection system to guarantee its reliable operation under extreme events when the operation of the APS is compromised. LAMP units operate in parallel with the conventional APS. As a backup, if APS fails to operate because of an issue in the communication system, LAMP units can accommodate a reliable fault detection and location on behalf of the protection relay. The performance of the proposed APS is verified using IEEE 123 node test system.

Smart networks such as active distribution network (ADN) and microgrid (MG) play an important role in power system operation. The design and implementation of appropriate protection systems for MG and ADN must be addressed, which imposes new technical challenges. This paper presents the implementation and validation aspects of an adaptive fault detection strategy based on neural networks (NNs) and multiple sampling points for ADN and MG. The solution is implemented on an edge device. NNs are used to derive a data-driven model that uses only local measurements to detect fault states of the network without the need for communication infrastructure. Multiple sampling points are used to derive a data-driven model, which allows the generalization considering the implementation in physical systems. The adaptive fault detector model is implemented on a Jetson Nano system, which is a single-board computer (SBC) with a small graphic processing unit (GPU) intended to run machine learning loads at the edge. The proposed method is tested in a physical, real-life, low-voltage network located at Universidad del Norte, Colombia. This testing network is based on the IEEE 13-node test feeder scaled down to 220 V. The validation in a simulation environment shows the accuracy and dependability above 99.6%, while the real-time tests show the accuracy and dependability of 95.5% and 100%, respectively. Without hard-to-derive parameters, the easy-to-implement embedded model highlights the potential for real-life applications.

This paper aims to present a centralized adaptive protection scheme (APS) for the directional overcurrent relays (DOCRs) considering system dynamics such as load demand variations, topology changes and DGs to mitigate the above-mentioned effects. The scheme is suitable for different types of networks whether its radial or meshed. Afterall, it can determine the actual topology with the micro-PMUs and breaker status, automatically generate relay names accordingly with the topology bus locations, establish protection coordination pairs, coordinate DOCRs for parallel lines, identify transformers to offer backup operation for differential protection, perform load flow and fault studies, execute contingency and sensitivity analysis, and lastly, coordinate the DOCRs using differential evolution algorithm so that they always have the proper settings to operate in appropriate time providing selectivity. The performance of the proposed centralized adaptive overcurrent protection scheme is tested on the highly meshed IEEE 14 bus system. The proposed scheme has shown that it can adequately consider impacts of system dynamics and DG.

The goal of this review paper will be to address complex optimization functions in the area of overcurrent relay optimization, to inspect and valorize their objectives and to critically examine their application in real distribution networks. Special emphasis will be put on observing the optimization of discrimination time between primary and backup relay pairs, and methods which prevent the latter becoming penalty functions will be shown. Furthermore, the impact of distributed generation units on the overcurrent relay optimization problem will be elaborated in detail. Protection settings of all the existing and new relays must be thoroughly inspected before the connection of new production units, because contributing fault currents may have a significant effect on the solution of the overcurrent optimization problem. This is because the relays being used are of an inverse-type. Next, meshed network operation will be critically assessed in comparison with the actual practice of radial operation, and some topologies will be highlighted for future research, while others will be discarded. The distribution network in mesh operation implicitly suggests using numerical relays on both sides of protected elements (usually lines), so their total number will be much higher than in radial operation. Finally, a relatively new concept of adaptive distribution network protection will be reviewed, and its potential application to the overcurrent relay optimization problem will be examined. The purpose of this review paper will be to lay a groundwork for future research papers by inspecting the overall development of the overcurrent relay optimization problem for contemporary and future active distribution networks. [ABSTRACT FROM AUTHOR]

Objective: This paper presents a qualitative comparison of different recently proposed network protection schemes that are based on the distance function. From this comparison, possible opportunities are identified to develop strategies oriented towards protecting active distribution systems. Methodology: This research is carried out in two parts: the first is to identify the fundamental theoretical aspects of distance protection, its main problems, and a description of the most important aspects of the relevant strategies proposed in recent years. The second part consists of selecting aspects and elaborating a qualitative comparison of the different protection schemes analyzed. This comparison makes it possible to establish the advantages and disadvantages of each of the relevant proposals used in conventional electrical networks or active distribution networks. Results: As a result of this research, the most important aspects to consider in the protection design are identified, which therefore strongly affect its performance. These are summarized in a comparative table, which supports future research related to distance protection in active distribution networks. Conclusions: From this research, it can be stated that the solutions analyzed, despite being relevant within the scope of distance protection applied to active distribution networks, have problems to solve. None of these strategies protects the network for all types of failures in a selective, sensitive, reliable, and cost-effective way while guaranteeing minimum supply interruption to consumers. Funding: This paper is a result from projects 6-20-6 funded by Universidad Tecnológica de Pereira and contract 774-2020 (Integra2023) funded by Minciencias, Colombia.

Greenhouse gas emissions are considered a global problem, which is why interest in implementing renewable distributed energy resources (DER) is increasing worldwide. However, despite the contributions to the reduction of fossil primary energy sources, the connection of DERs to power grids often gives rise to new problems in control, operation and protection systems that need to be analyzed and solved. The objective of this paper was to compare a conventional overcurrent protection scheme and several adaptive schemes for active distribution networks (ADN). The proposed methodology consisted of performing an analysis of the adaptive protection approaches for ADN. From this evaluation, the most relevant documents were classified according to the main requirements, contributions, and conclusions. Additionally, some of these proposals were tested with conventional overcurrent protection, using the ATP simulator and Python software. Finally, a quantitative and qualitative analysis of the proposed protection approaches was performed in order to identify limitations to be considered in future research work. The results obtained, when considering different faults and modes of operation of the DNA, showed that the conventional protection coordination approach is highly vulnerable to faults when DERs are connected, mainly due to the change in current magnitudes and direction. The adaptive schemes analyzed have adequate performance, however, several application issues need to be analyzed in the future.

Active distribution networks integrate distributed energy resources into traditional power grids, mainly guided by the intention of addressing climate change concerns. However, integrating distributed energy resources has introduced several challenges for traditional overcurrent protection, including variations in pre-fault and fault current magnitudes and bidirectional power flows. These challenges make it difficult to guarantee reliable protection of active networks in grid-connected and islanded modes. In response to the challenges posed by these new networks, this paper presents an adaptive protection approach that leverages local measurements and data clustering to identify the network operating states accurately. In this approach, reference relay coordination is obtained by considering all distributed energy resources that supply the network during the grid-connected operating state, providing optimal settings for each relay. Next, based on the current operating state, the adaptive relay pickup current is estimated based on local measurements, which is used to adjust the time dial setting of each directional overcurrent relay. The proposed approach is contrasted with the conventional relay, considering several operating states, including DER switching, grid-connected, and islanded modes, for single-phase and three-phase faults and several fault resistances, using the IEEE 34-node test feeder. The results demonstrate the proposal's high performance in avoiding relay miscoordination. Finally, the proposed approach is also simple and suitable for immediate implementation in existing digital relays, as it has a low computation burden and does not require communication systems. • Proposes an approach for communication-less adaptive protection to update the relay settings adequately. • The approach detects the ADN OS originated by the connection/disconnection of DERs, starting from a reference case and using clustering and classification approaches. • The relay parameters are online estimated from the local pre-fault current and voltage measurements. • The proposed solution does not use a centralised computation scheme. • The protection approach uses straightforward computation, resulting in a low computational burden. [ABSTRACT FROM AUTHOR]

The advancements in smart grid technologies had brought forth the prospect of self-healing distribution grid through intentional islanding, aided by the steadily rising penetration of inverter-based distributed generations (IBDGs). Adaptive protection is the key enabler for this resilient grid architecture. For cost-effectiveness, overcurrent relays (OCRs) with adaptive features had been proposed, often with the sensitivity problem due to low short-circuit current magnitude from the IBDG taken into consideration and largely addressed. However, apart from this widely discussed sensitivity problem, there is an underlying issue on selectivity of the OCR which is frequently disregarded when designing an adaptive overcurrent protection scheme for IBDG dominated microgrid. This selectivity problem is mainly caused by the current diversion to load during fault, which is often disregarded when performing OCR grading for a conventional grid. In this paper, this selectivity problem of the OCR is discussed in depth through a comparative study of conventional grid and a modern IBDG dominated grid. The coordination time interval margin violations problems are demonstrated through theoretical calculations and real-time hardware-in-the-loop experiments. This research aims to provide better insights into the selectivity problem as a step towards achieving a cost-effective yet reliable overcurrent-based adaptive protection for IBDG dominated microgrid. [ABSTRACT FROM AUTHOR]

This paper presents a novel protection strategy for assuring power-system frequency stability. After many years of use, the existing (static) under-frequency load-shedding concept has proven to be reliable and fast. However, it does not adapt well to volatile operating conditions, which might often lead to a system collapse. This developed into a major obstacle, since operational conditions of modern power systems are persistently subjected to fast and unpredictable changes. Therefore, there is a need to introduce a new capability in under-frequency load-shedding that would be able to fine-tune the mismatch in active power in any conditions. From the practical aspect, a systematic implementation of improvements should not threaten system stability. In terms of cost, a minimum intervention in the existing concept is desirable. This is why we developed an effective upgrade of the existing concept by introducing a specialized group of intelligent electronic devices supported by a principal component analysis technique. This group should be operated alongside the existing solution to monitor the actual frequency conditions and to take over power-balancing when fine-tuning is required. This supports the existing load-shedding and improves the process of frequency stabilization. [ABSTRACT FROM AUTHOR]

The real-time (RT) hardware-in-the-loop (HIL) simulation-based testing is getting popular for power systems and power electronics applications. The HIL testing provides the interactive environment between the actual power system components like control and protection devices and simulated power system networks including different communication protocols. Therefore, the results of the RT simulation and HIL testing before the actual implementation in the field are generally more acceptable than offline simulations. This paper reviews the HIL testing methods and applications in the recent literature and presents a step-by-step documentation of a new HIL testing setup for a specific case study. The case study evaluates real-time implementation of previously proposed communication-dependent logically selective adaptive protection algorithm of AC microgrids using HIL testing of IEC 61850 generic object-oriented substation event (GOOSE) protocol. The RT model of AC microgrid including the converter-based distributed energy resources and battery storage along with IEC 61850 GOOSE protocol implementation is created in MATLAB/Simulink and RT-LAB software using OPAL-RT simulator platform. Local area network (LAN) at the laboratory acts as IEC 61850 station bus for exchanging GOOSE Boolean signals between the RT target and the actual digital relay. The evaluation of the round-trip delay using the RT simulation has been performed. It is found that the whole process of fault detection, isolation and adaptive setting using Ethernet communication is possible within the standard low voltage ride through curve maintaining the seamless transition to the islanded mode. The signal monitoring inside the relay is suggested to avoid false tripping of the relay.

This article presents a new adaptive and optimal overcurrent protection for large-scale wind farms using hybrid grey wolf optimizer and rule-based fuzzy logic controller (GWO-FLC) scheme. The proposed GWO-FLC based adaptive protection scheme overcomes the limitation of conventional protection scheme that suffers from maloperation of relays that damages the power components in the system during fault. Furthermore, due to the intermittent nature of wind, the generated current feeding the grid during extreme high and low wind speeds creates a significant difference in magnitudes of the generated current. Thus, the existence of only one group of settings for the overcurrent relays (OCRs) would cause drastic miscoordination and false tripping during fault. In order to test the performance of the proposed GWO-FLC scheme, several OCRs based on standard Schweitzer Engineering Laboratories industrial protection relay (SEL-751) are developed in MATLAB/Simulink. A large-scale wind farm model is also developed to perform fault analysis, relay setting, and coordination calculation. The GWO is implemented to attain optimal OCR coordination for the defined quadruple group settings for all relays, and the FLC is developed to provide adaptive feature for the relays so that the OCR group settings for each relay are intelligently updated according to the variation of wind speed. Finally, in a laboratory environment, the proposed protection scheme is implemented in real time using field-programmable gate array DE2-115 board equipped with Cyclone IV-E device (EP4CE115F29C7). It is found from both simulation and experimental results that the performance of the proposed hybrid GWO-FLC is robust, reliable, efficient and extremely satisfactory. [ABSTRACT FROM AUTHOR]

Electric power distribution networks are generally radial in nature, with unidirectional power flows transmitted from the highest voltage levels to the consumption levels. The protection system in these distribution networks is relatively simple and consists mainly of fuses, reclosers (RC) and overcurrent relays (OCRs). The installation of distributed generation (DG) in a network causes coordination problems between these devices, because the power flows are no longer unidirectional and can flow upstream to the substation. For this reason, the work proposed here analyzes the most significant impacts that DG has on the protection devices and proposes an adjustment method for the OCRs based on linear programming (LP) techniques with the aim of improving their response time to the different faults that may occur in the main feeder of the network. The distribution system selected for the study is the IEEE 34 bus system using DIgSILENT 14.1 software for its modeling and Matlab for the adjustment of the overcurrent devices. Results indicate that better coordination between protection devices are achieved if LP is used. [ABSTRACT FROM AUTHOR]

This paper presents the effect of atmospheric turbulence, which is the main factor affecting energy production in renewable sources such as photovoltaic (PV) and wind energy systems. The power generated by PV and wind systems could be affected by partial shading, the temperature of shaded cells increases and thus reduces the energy generation of the shaded photovoltaic and the same is occurred in wind farm(WF) , over the day wind speed or wind direction are varying. In fact, weather instability not only affects the energy production for PV and wind farms but also effects on the sustainability and reliability (RES) during conversion to island mode operation for protection of microgrid which are a part of adaptive protection of the smart grid. On the other hand, It’s deal with the determination of fault current (During three phase short circuit (SC) and phase to ground fault) at different configurations in model, each overcurrent relay (OCR) will be adapted based on the status of the grid that by monitoring the parameters of the grid or microgrid for RES where each OCR’s has several settings (two or more). In adaptive protection system, it’s a centralized supervisory system and it modifying the OCR settings centrally based on the grid configuration. Main advantage of using adaptive protection of OCR to choose the optimum setting that to eliminates the consequences of incorrect OCR coordination values when applied .That will be lead to wrong decision whether incorrect trip event or no response of OCR under fault conditions. That will be facilitated maintain the energy reliability in smart grid.

The smart power grid has been developed and improved constantly to be able to incorporate protection, automation, communication, and advanced control methods. As a result, the smart power grid system protection is expected to be modernized and given the ability to handle the future complexity that emanates from the integration of Distributed Generations (DGs). An Adaptive Multi-Agent System (MAS) can enhance power system protection and make it more reliable, faster, selective, and robust. In this paper, a novel MAS-based adaptive protection technique that suits smart grid applications is proposed. The proposed protection technique consists of agents that communicate with each other and their environment. The agents used in the proposed technique are Short Circuit Current Calculation Agent (SCCA), Load Flow Calculation Agent (LFA), Setting Calculation Agent (SCA), Logic and Operating Agent (LOA), Coordination and Optimization Agent (COA), and Network Configuration Mapping Agent (NCMA). The proposed technique can adapt to the changing conditions in the smart grid. The DigSILENT PowerFactory software is used to verify the proposed technique using a real Distribution Network in the Antalya vicinity of Turkey. The achieved results show that the method can provide fast and selective protection for the smart grid with increased integration of DGs. [ABSTRACT FROM AUTHOR]

Microgrid (MG) is a system of production and distribution of electrical energy that can operate both in grid-connected and islanded modes. This capability leads to significant variations in the fault current level. Moreover, dynamic changes corresponding to the line outage contingencies or outages of the distributed generations (DGs) that are implemented for local generation in the MGs lead to the changes in the fault current level. These changes in the fault current level make some miscoordination between the overcurrent relays (OCRs) in the conventional protection schemes. To overcome this drawback, there is a need for an adaptive protection scheme that can adapt to both operational and dynamic changes and takes effective protection decisions accordingly. This paper first presents a statistic-based review of MG and its protection including total publications, type of publications, the ten most researchers, and the ten most sources. Finally, comprehensive remarks of the 30 most cited papers related to adaptive protection of MG are presented. This paper will help the researchers of the MG protection to learn the most desirable techniques and the concentration of studies in adaptive protection of MGs for future works. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive protection system applied to distribution electric power systems (EPS) which include distributed generation and active network management (ANM) is proposed. Obtained results provide also coordination and selectivity for all analyzed scenarios, as the possibility to use proposed adaptive protection methodology to indicate the deactivated directional function. Traditional adjustments do not provide an accurate coordination system. Modern techniques of control and operation in EPS have been extremely important to the development of solutions to old EPS problems, like loss of coordination and selectivity in protection systems after topological or operational modifications. Methodologies able to keep all protection devices coordinated after network modifications, provoked by ANM system, are actual and relevant. The benefits of the coupled actuation of these techniques made more evident when small generators have been connected to the power grid, a fact that improves a high level difficult to determine power protection parameters based on overcurrent relays. The obtained results indicate for reductions of up to 45% of the improper operations of protection system when compared to the traditional protection systems. [ABSTRACT FROM AUTHOR]

Electric power distribution systems have been submitted to major changes related to the integration of communication infrastructure and new technologies such as distributed generators, electric vehicles, energy storage systems, smart meters with two-way communication, and digital protection equipment. However, in most cases, the functionalities available in the digital equipment are not fully exploited and the same protection rules applied to electromechanical relays are practiced. In this context, this work proposes a new adaptive protection methodology using the functionalities present or potentially present in modern protection equipment. A mixed integer linear programming model for the calculation of phase protection settings and a multi-objective mixed integer linear programming model for the calculation of neutral protection settings. Additionally, the use of operating zones, based on the Thévenin equivalent impedance, is proposed to trigger the automatic adaptation of the overcurrent protection equipment adjustments. Tests employing the proposed methodology in a real distribution system show that coordination and selectivity are guaranteed in the minimal operation time for different operation conditions. The results attest to the usefulness and efficiency of the proposed methodology in automating and guaranteeing the correct performance of the protection system. [ABSTRACT FROM AUTHOR]