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Power system protection and asset management have drawn the attention of researchers for several decades; but they still suffer from unresolved and challenging technical issues. The situation has been recently exacerbated in the wake of the ever-changing landscape of power systems driven by the growing uncertainty and volatility subsequent to the vast renewable energy integration, more frequent natural extreme events due to climate changes, increasing malicious cyberattacks, and more constrained transmission systems as the result of load growth and limited investments. On the opposite side, the proliferation of advanced measuring devices such as phasor measurement units, emerging electric and non-electric sensors, and Internet of Thing (IoT)-enabled data gathering platforms continually expand/nourish the databases; they hence offer unprecedented opportunities to take the advantage of data-driven techniques. Machine learning (ML) as a principal class of artificial intelligence is the perfect match solution to this need and has newly revoked many researchers’ interests to tackle the problems excluding their exact/detailed models. This paper aims to provide an overview on applications of ML techniques in power system protection and asset management. This paper elaborates on issues pertaining to (1) synchronous generators, (2) power transformers, (3) transmission lines, and (4) special and system-integrity protection schemes. In addition to the opportunities offered by the ML techniques, this paper discourses on the barriers and challenges to the wide-spread application of ML techniques in real-world practices.

Given the decisive modernization of power systems and the evolution of protective relaying, it is imperative to merge traditional protection systems with innovative approaches that allow flexibility and time-domain protection. Time-domain approaches for power system protection must be tested in realistic and flexible platforms prior to their actual implementation. Inexpensive and flexible testing platforms are needed to fill this gap; consequently, a hardware-in-the-loop (HIL) testing platform for a distance relay for feeder protection is presented in this article. The relay is tested in an HIL simulation of a single-machine infinite-bus system simulated in PSCAD software, and the distance protection function is implemented in a commercially available LAUNCHXL-F28379D microcontroller. One-phase-to-ground, two-phase-to-ground, two-phase, and three-phase faults are tested in the simulation system, showing the feasibility of the proposed approach for protection system testing.

Integration of Distributed Generation (DG) on distribution networks has a positive impact which includes the following: low power losses, improved utility system reliability and voltage improvement at buses. A real distribution network is radial in which energy flow is unidirectional from generation to transmission and from distribution to the load. However, when a DG is connected to it, the power flow becomes bidirectional, and the protection setting of the network may be affected. Therefore, the aim of this research work is to investigate the impact of distributed generation DG on power system protection. The test distribution network is first subjected to load flow analysis to determine its healthiness with and without DG connection. The load flow results confirm that the integration of the DG into the distribution network reduces the active power load loss by 92.68% and improves voltage profiles at each bus of the network by 90.72%. Thereafter, the impact of DG on the protection setting of the existing test network was investigated. Integrating DGs to the network, from our result, shows an increase in the fault currents, which in turn caused false tripping, nuisance tripping, and blinding of protection relay compared with when DGs are not connected. The protection relays were reset at the point of common coupling (PCC) to prevent any abnormal tripping. This is the major contribution of the research work

Current research on cascading failures of wireless sensor networks (WSNs) mainly focuses on single-sink networks and rarely involves multisink networks. To this end, this article proposes a realistic cascading model for multisink WSNs based on a new load metric “multioriented link betweenness.” On this basis, a memetic algorithm MA-MSP is proposed to help WSNs resist cascading failures via multisink placement optimization, in which the local search operator is designed based on a new network balancing metric “multioriented network entropy.” Extensive simulations have shown that the proposed cascading model can properly characterize the cascading process of multisink WSNs. Link capacity is a key factor in determining network robustness. MA-MSP can obtain a more robust placement scheme with less time compared to existing algorithms. The network communication efficiency is positively related to network robustness, and the average shortest path length is negatively related to network robustness.

Inverter-Based Resources (IBRs), including Wind turbine generators (WTGs), exhibit substantially different negative-sequence fault current characteristics compared to synchronous generators (SGs). These differences may cause misoperation of customary negative-sequence-based protective elements set under the assumption of a conventional SG dominated power system. The amplitude of the negative-sequence fault current of a WTG is smaller than that of an SG. This may lead to misoperation of the negative-sequence overcurrent elements 50Q/51Q. Moreover, the angular relation of the negative-sequence current and voltage is different under WTGs, which may result in the misoperation of directional negative-sequence overcurrent element 67Q. This paper first studies the key differences between the WTGs and SG by comparing their equivalent negative-sequence impedances with SG's. Then, simulation case studies are presented showing the misoperation of 50Q and 67Q due to wind generation and the corresponding impact on communication-assisted protection and fault identification scheme (FID). The impact on directional element is also experimentally validated in a hardware-in-the-loop real-time simulation set up using a physical relay. Finally, the paper studies the impact of various factors such as WTG type (Type-III/Type-IV) and Type-IV WTG control scheme (coupled/decoupled sequence) to determine the key features that need to be considered in practical protection studies. The objective is to show potential protection misoperation issues, identify the cause, and propose potential solutions.

Distance and directional elements are widely used in power system protection. One of the used essential signals, having a substantial impact on proper operation, is polarizing voltage. During faults close to a protection relay, memory filters can be used to ensure the availability of this voltage. A basic assumption of these memory filters is that during a fault only an amplitude of a measured voltage changes rapidly and other parameters change very slow. The assumption is correct in power systems with an overwhelming share of traditional rotating generators. However, today, more and more energy sources are connected to power systems through inverters. Algorithms implemented in inverters can control parameters of output voltage so that they can be changed rapidly without any inertia. Therefore, a source of robust polarizing voltage is needed to ensure proper operation of distance and directional elements. The paper presents a method of a reference signal generation based on phase-locked loop (PLL). The algorithm consists of PLL with an adaptive notch filter, and elements adding inertia to the generated signal. The reference signal can be used as a polarizing voltage in protection elements. The paper describes all elements of the algorithm and presets operational tests.

Cascading failure on complex networks has been extensively studied over the past decade. However, restoration of networks from cascading failure is still relatively unexplored. In this paper, we consider cascading failure in conjunction with the restoration process involving repairing the failed nodes in a sequential fashion. Depending on the availability of resources, we tackle the sequential recovery problem from two distinct approaches, namely, result-oriented and resource-oriented restoration approaches. In the result-oriented approach, we aim to restore the network to the largest extent and within the shortest time. Heuristic network restoration strategies based on node load or degree are proposed. For resource-oriented restoration, we aim to maximize the increase of network size with a given number of nodes to be repaired, and we propose a novel iterative strategy to improve performance. Simulation results on the Barabasi–Albert scale-free network, Internet autonomous system-level network, and IEEE 300 bus power system have demonstrated the effectiveness of the proposed sequential recovery strategies.

Cascading failure inevitably emerges in complex power grids that can cause enormous economic losses. Over the past few decades, a great deal of effort has been devoted to failure cascade modeling, with the aim of understanding and preventing this complex process. Significant achievements include reproducing the uneven cascade propagation profiles and the power-law distribution of the size of the cascades. At the same time, power grids keep evolving, as driven by technology advancements and practical needs. Wide deployment of information technologies and high penetration of power electronics devices are two important features of future grids. These developments have profound influences on the cascading failure characteristics in future grids, which cannot be well addressed by existing models. In this tutorial, we provide an overview of the state-of-art approaches in studying cascading failure and discuss the strengths and weaknesses of these methods. The explicit changes brought by the new features to the failure cascade processes are analyzed and the limitations of existing approaches are identified. Challenges in the modeling and analysis of cascading failure and possible research directions targeting the future power grids in the next research phase are presented.

After major disturbances, power system behavior is governed by the dynamic characteristics of its assets and protection schemes. Therefore, modeling protection devices is essential for performing accurate stability studies. Modeling all the protection devices in a bulk power system is an intractable task due to the limitations of current stability software, and the difficulty in updating the setting data for thousands of protection devices. One of the critical protection schemes that is not adequately modeled in stability studies is distance relaying. Therefore, this paper proposes an iterative algorithm that uses two methods to identify the critical distance relays to be modeled in stability studies: (i) apparent impedance monitoring, and (ii) the minimum voltage evaluation (MVE). The algorithm is implemented in Python 3.6 and uses the GE positive sequence load flow analysis (PSLF) software for performing stability studies. The performance of the algorithm is evaluated on the Western Electricity Coordinating Council (WECC) system data representing the 2018 summer-peak load. The results of the case studies representing various types of contingencies show that to have an accurate assessment of system behavior, modeling the critical distance relays identified by the algorithm suffices, and there is no need for modeling all the distance relays.

Urban rail transit has become an important traffic mode in large cities and has brought great conveniences to urban residents, however traffic accidents often occur in daily operations, therefore the safety and robustness must be paid more attention. In this paper, the network utilization of urban rail transit networks (URTNs) is expressed by the travel time difference between user equilibrium and optimal system, and the travel time difference is considered as the assessment indicator of robustness. Meanwhile, Shanghai metro network is taken as the example to analyze the robustness of URTNs under different disturbances, such as node attack, link-demand attack and overall-demand attack. The results show that URTNs have better robustness subjected to the random link-demand attack than node attack, and the robustness decreases with the increase of the attack intensity when the network suffers overall-demand attack. Moreover, we find that the critical stations and links can be identified, and URTNs can be paralyzed when the attack intensity exceeds the critical threshold.

Many real-world networks have scale-free characteristics and can be abstracted into scale-free networks. Aiming at the problem that scale-free networks have low fault tolerance in the face of malicious attacks, we focus on the selective forwarding attack behavior that exists widely in the networks, and build a selective forwarding attack model based on node importance. Moreover, according to the neighbor node’s malicious and non-malicious behavior, a load redistribution strategy for failed node is proposed. Then, the network’s damage degree is given to evaluate the comprehensive impact of cascading failure phenomenon on network connectivity and information integrity under selective forwarding attack. Finally, a cascading failure model of scale-free networks considering selective forwarding attack behavior is obtained. Based on this model, the propagation condition without triggering network cascading failure, the selective forwarding attack intensity threshold and the load loss ratio are obtained. By simulation on the classical BA scale-free network model, the results show that multiple nodes’ random failure occurs in scale-free networks, selective forwarding attack behavior is helpful to improve the connectivity of the network. Besides, the network exists selective forwarding attack intensity threshold, when attack intensity is greater than the intensity threshold, the malicious nodes will not fail because of the failure of the neighbor nodes. But, selective forwarding attack behavior can destroy the information integrity, and there is a negative correlation between the attack intensity and the information integrity. These results have certain guiding significance for cascade failure analysis and prevention method research and design in real life.

A novel passive method based on Permutation Entropy (PE) is proposed for fast, efficient, and differential detection of islanding from other disturbance events in power system. The extremely remark...

Power systems are subjected to various types of faults as well as ferroresonance overvoltages. These results in the interruption of the normal operation of the power grid, failure of equipment, electrical fires, etc. To tackle these issues, this study proposes a dual function limiter to control the fault current and ferroresonance phenomenon in power systems. This compound device is a solid-state series transformer-based limiter that includes IGBT switches, capacitors, rectifiers, and a DC reactor. During the grid normal operation, the proposed limiter is not active and therefore is invisible and it operates in the instant of fault inception or ferroresonance overvoltage occurrences. Analytical studies in all operation modes are presented and assessments on the performance of the proposed ferroresonance and fault current limiter (FFCL) are conducted in Matlab. Simulation results confirm the reported analytical studies and FFCL's performance.

Conversation and assurance issues play a crucial function when talking regarding to the wise grid. This particular paper presents opportunities of testing power framework assurance transfers and correspondence standards for smart supply. A depiction in the Smart Grid lab hardware and the key protection devices is usually presented in the paper. Further employ cases and uses offered by the Labrador equipment are referred to and the possibilities by dynamically setting up devices and program interaction are demonstrated. Ideas for the mix of checked and controllable decentralized vitality sources are demonstrated the network capacity and Quality of Services (QoS) are tested and evaluated. By implementing adaptive modulation scheme, the served users were increased by 10% at heavy Traffic Load (TL).

Load redistribution (LR) attacks represent a major cyber threat to the power grid that can result in branch overloads and even cascading failures in the transmission network by injecting false data to load bus power injection and line power flow measurements. While the mechanism and defense strategies have been well studied for single-occurrence (i.e., discrete) LR attacks, this paper focuses on a yet unexplored category of LR attacks, namely, the continuous LR (CLR) attack, which continuously injects time-varying false data to one or more bus and branch measurements within the system for a certain period of time. To cope with the potentially ever-changing targeted branches (i.e., the branches under attack) and system vulnerability features caused by CLR attacks, this paper takes a different route from the traditional LR defense and mitigation approaches. We propose a novel correlation chain model to capture the vulnerability correlations among branches under the CLR attack. Then, a dynamic sequential-mining algorithm (DSMA) with top-k structure is proposed based on the specific nature of the CLR attack, to mine the historical SCADA measurement database, extract vulnerable branch sequences, and identify the most suitable branches to defend preventively. Simulation studies are conducted on IEEE RTS-96 system to evaluate the effectiveness of the proposed approach in terms of increasing attack costs for the attackers and reducing the potential impacts of CLR attacks.

Coordination of microgrids protections is an emerging research issue due to the increasing participation of distributed generation (DG) in power grids. This review paper aims to show the current weaknesses in the coordination of protections for microgrids, as well as the available solutions and future challenges. The review evidences that microgrid protection systems must face two important aspects. The first one is the dynamic behavior presented by the microgrids that take place due to the intermittency of energy resources. The second one is related to the operation modes of the microgrids, since they may operate either connected or disconnected from the distribution network. The literature review also allowed classifying the most used protection schemes for microgrids. A comprehensive analysis which performs a discusion of the most relevant future challenges regarding microgrid protection coordination is also presented.

Microgrid is a decentralized system in which electrical sources and loads are connected in a way that operates normally in connection with and in synchronous with conventional grid. This system has the ability to work autonomously by disconnecting from conventional grid in island mode. Microgrid offers large number of advantages in power system. Among them, integration of renewable energy sources, reliability, two-way power flow and cost effectiveness are the significant merits of microgrids. Besides its advantages, different challenges are associated with the planning, operation and protection of microgrid systems. Safe two-way power flow, reliable switching of renewable energy, optimal power flow, quick isolation of faulty part from healthy system and incorporation of energy mix modeling are the major challenges behind its real time implementation. In this research, comprehensive analysis is carried out on the planning, operation and protection of microgrid model. A test system is developed in Matlab/ Simulink in which solar power source, wind power source and diesel power source are modelled and connected to residential, commercial and industrial loads. Optimal power flow is achieved through Newton’s method. In addition to this, operation of microgrid test system is ensured by the observation of voltage, current and power under steady state and transient conditions of wind based power generation, DC and AC parameters for solar power generation and generation and demand of power in the case of diesel based power generation within acceptable limits. Circuit breakers are installed to ensure protection against faults. Priority is made on the basis of promotion of renewable energy sources. Moreover, realization of microgrid is depicted with its hardware prototype.

Recently, the requirement of the electrical energy from the renewable source has been growing in the South Korea since government’s energy plan to generate the electrical power of 20% as renewable source. In addition, these renewable power plants have been constructed on not only the existing power plant’s side but also customer’s side. These changes in power distribution system cause the fault current to increase higher and to reverse the direction of the fault current. Variable countermeasures to reduce the fault current have been studied and the introduction of the superconducting fault current limiter (SFCL) in the power distribution system, one of them, has been actively reported. However, the installation of the SFCL can affect the power system protection because of the fault current’s decrease or increase, which depends on the construction of the power distribution system. Especially, the application of the SFCL in a closed-loop power distribution system can cause the delayed trip operation or the fast trip operation of the over-current relay (OCR), one of the representative protective devices widely used in a power distribution system. This change can influence on the existed protective coordination. In this paper, the OCR with voltage component, one of the methods to suppress its trip operation’s change in a power distribution system with a closed loop construction due to the application of the SFCL, was suggested and the protection coordination between the OCRs in a power distribution system with a closed loop was analyzed. It was confirmed that a simple using voltage component in the OCR could cause the trip variation of the reverse direction OCR in loop power system and it can be improved by matching the relaying voltage components.

The relay protection system plays an important role in ensuring the stable operation of power systems. Combined with operation data collected from a region in China, this study is aimed at providing a reliable quantitative basis for relay protection systems’ operating maintenance by the aid of a semi-supervised Mahalanobis distance machine learning algorithm. The evaluation result is first applied as a training set on the basis of the analytic hierarchy process fuzzy synthetic evaluation. Then, contrastive analysis is conducted in terms of accuracy, processing time, and feasibility. It includes comparative cases with a supervised multiple regression analysis algorithm and unsupervised K-means algorithm. The comparison result reveals that the algorithm can effectively and accurately predict the running state of the equipment and offer a quantitative reference for relative maintenance strategy.

WOS:000558313300007 The future distribution networks (DNs), commonly known as the smart grid is expected to be reliable, efficient, and can accommodate renewable energy resources. The smart distribution network has to withstand the technical challenges related to the integration of distributed generations (DGs). Among these technical challenges, protection malfunctioning with the increased integration of DGs is one of the important issues, which requires a great concern. Thus, a protection philosophy, which can suit the future smart grid requirements with respect to increased integration of DGs, has to be devised. In this paper, an adaptive protection technique, which is based on the characteristics of fault-current and load-current variation, is proposed. In the proposed method, intelligent electronic devices (IEDs) monitor the status of circuit breakers (CBs) and DGs. If any status change occurs, the calculation and relay agents are triggered to update the IEDs. DigSILENT PowerFactory is used to verify the suggested philosophy. Especially DigSILENT Programming Language (DPL) is used to model the adaptive protection. The solar power plant in the Antalya vicinity in Turkey is used to verify the proposed method. The results of the simulation study show the correct operation and effectiveness of the proposed method.

The dc in a power system may be caused by geomagnetic disturbances that are the result of solar storms and high-altitude nuclear detonations. Increased inverter-based generation is also contributing to small dc injection into the power systems. The resultant dc could have serious consequences for the power systems as it may drive power transformers into saturation, cause transformer internal heating, cause large draw of reactive power, and misoperation of protective relays. This letter proposes a novel power electronics-based dc mitigation approach that involves a transformerless series active filter integrated between the neutral point and ground of power transformers serving multiple purposes. The first objective is to surpass the effect of dc injection, the second goal is voltage regulation, and the third is to provide harmonic isolation or impedance balancing. The proposed device is currently being developed on a 7.2-kV/240-V single-phase transformer; however, the solution is also relevant for 24–500-kV networks. The system circuitry, operation, and control are implemented and verified for this letter in a controller hardware-in-the-loop (C-HIL) test setup using a Typhoon HIL-402 simulator. Results indicate that our approach is a promising alternative to traditional neutral capacitor-blocking strategies.

Fault current characteristics in dc systems depend largely on the response, and hence also the topology, of the ac–dc converters. The presently used ac–dc converter topologies may be categorized into those with controlled or uncontrolled fault-blocking capability and those lacking such capability. For topologies of the former category, generic models of the dc-side fault response have not yet been developed, and a characterization of the influence of control and sensor delays is a notable omission. Therefore, to support accurate and comprehensive dc system protection studies, this article presents three reduced converter models and analyzes the impact of key parameters on the dc-side fault response. The models retain an accurate representation of the dc-side current control, but differ in the representation of the ac-side and internal current control dynamics, and arm voltage limits. The models have been verified against a detailed (full-switching) simulation model for the cases of a full-bridge and a hybrid modular multilevel converter and validated against experimental data from a laboratory-scale prototype. The models behave similarly in the absence of arm voltage limits, but only the most detailed of the three retains a high degree of accuracy when these limits are reached.

The cyberphysical power system resilience testbed implements, tests, verifies, and evaluates cyberphysical resilience solutions for power systems integrated with a communication infrastructure. It offers a platform for real-time simulation of power systems in concert with real-world monitoring, control, and protection.

A new age of electrical energy management is driven by modern communication systems. Technologies such as the Internet of Things (IoT) and cloud and fog computing are becoming seriously considered by the industry as a replacement for old communication systems in modern distribution networks, such as existing supervisory control and data acquisition (SCADA). Large amounts of data, produced by millions of customers, will be used by power system operators in the near future, with the ultimate goal of creating a fully automated and self‐conscious Ssmart Grid (SG). Cloud computing proved to be a very successful technology with applications in many areas, but bandwidth‐ and latency‐related issues raise questions about its efficient application for near real‐time calculations required by SGs. On the other hand, fog computing technology supports fast local data calculation and analysis, which could be the key for near real‐time data management. Power system operations are governed by many devices with different data processing time requirements, e.g. digital relays used for power system protection are often required to operate and communicate with each other in less than 50 ms. On the contrary, smart meters, collecting data for load balancing, are required to communicate just once in several minutes. Sampling rates of modern SCADA systems are often one sample per second. These significant differences in data transmission and calculation speeds pose a big challenge to modern communication systems. This chapter primarily aims to investigate the possibilities of fog computing–based communication system applications in the SG. Existing IEEE test grid topology is used as a basis for the creation of the SG model in MATLAB/Simulink. The developed SG model is made of energy and communication parts adjusted to operate simultaneously in a real‐time simulation environment. A special fog computing–based communication system is recommended and tested for state estimation and load flow calculation. Obtained results of near real‐time simulations proved applicability and efficiency of the proposed communication system for monitoring and regulation of voltage profile in the test grid.

This paper presents a flexible model and testing arrangement that can be used to mimic the fault infeed characteristics of power electronics converters and evaluate the performance of transmission protection schemes to faults when the system is “converter-dominated”. That is, sources (e.g. renewables) and infeeds (e.g. HVDC interconnectors) that are interfaced to the main power system via converters. Actual protection relays are injected, in real time, using the outputs of the various fault simulations. A range of potential protection issues, including slow tripping, erroneous discrimination and non-operation, are illustrated for particular scenarios. The main contributions of the paper include knowledge of how different protection schemes may be affected by converter-interfaced sources and guidance on possible solutions to the observed problems. Two solution options are highlighted: changes to the fault detection methods used within relays, and/or defining the fault-response elements of future grid codes (and therefore future converter fault responses) to ensure that existing protection schemes will not be adversely affected in future low-carbon, converter-dominated systems.

Increasing power demand, penetration of renewables, and limitations of necessary grid expansion are proffering new challenges to existing power system protection and control strategies. However, with the advancement in intelligent electronic devices and relaying technology, fast, accurate and reliable protection schemes can be developed for smart power systems. In this paper, a new protection scheme based on admittance and power change has been proposed with dual-use line relays to detect symmetrical/asymmetrical faults in power systems. A large number of fault environments have been simulated by varying fault distances from relay location, fault resistance, and power angle in single machine infinite bus and WSCC 9-bus systems. Some crucial decisive fault scenarios e.g. close in/far end faults, faults in series compensated line, faults during asymmetrical swings, switching ON/OFF large loads, single and multi-modal swings have also been verified for the proposed index. In this paper, for the first time, detection of faults during power swings have been examined and verified in the presence of wind farms. The simulation results show the proficiency of the proposed algorithm for detecting faults in the presence or absence of power swings.

DC microgrids have attracted increasing concern in industrial applications due to a simple and efficient integration with renewable energy sources, battery energy storage, and variable speed generators and motors. However, extensive application of dc architecture is still restricted by fault protection challenges posed by the absence of natural current zero-crossing. This paper has proposed a novel thyristor-based dc circuit breaker with a one-shot triggering commutating circuit, which maintains a compact size as no additional power supply is required to precharge the commutating capacitors. Considering di/dt limitation of the triggering thyristor in the commutating circuit, a saturable inductor is utilized to avoid hot spot failure in the thyristor. Moreover, saturation characteristic of the inductor allows a sharp-rising commutating current which can provide zero-crossing for the main thyristor with a shorter delay. A real-time analog protecting unit is also introduced to interrupt fault current accurately and rapidly. Furthermore, detailed breaker topology analysis and circuit design guidelines are provided through mathematical modeling. Finally, the proposed breaker design method is verified by simulation studies over two cases and further validated by a 400 V/4 kW laboratory prototype.

With the increasingly close coupling between the cyber network and the physical power grid in Cyber Physical Power System (CPPS), the failure of cyber network has become an important cause of blackout. Equipment failure or abnormal operation state will be appeared without alarm in complex cyber network, which brings hidden failures not been diagnosed and dealt with in time. The invisibility and harmfulness of hidden failures pose a significant threat to the safe, reliable, and stable operation of CPPS. The dual hidden cascading failure model for CPPS is proposed to reveal the failure characteristics of CPPS accurately, considering not only the hidden faults in the power grid, but also the hidden failures in the cyber network. With the different coupled relationships between power systems and cyber networks, the cyber network topology with corresponding failure threshold is obtained according to the simulation of the model with different hidden failure rates of cyber network nodes. When the hidden failure rate is lower than the failure threshold, the scale-free topology cyber network coupled mode is adopted between power grids and cyber networks, otherwise the small-world topology cyber network coupled mode is adopted, which can effectively reduce the risk of power system blackouts. The method proposed in this paper is tested by using IEEE-118 power system and its cyber network. The results show that the method is effective.

In this paper, we give attention to the robustness of the Cyber-Physical System, which consists of interdependent physical resources and computational resources. Numerous infrastructure systems can evolve into the Cyber-Physical System, e.g., smart power grids, traffic control systems, and wireless sensor and actuator networks. These networks depend on their interdependent networks, which provide information or energy to function. In a Cyber-Physical System, a small failure could trigger serious cascading failures within the entire interdependent networks. In this paper, we try to alleviate these cascading failures between interdependent networks to reduce losses. We discuss the robustness of systems for random attacks by calculating the size of functioning components in entire networks. We change the inter-links topology of the coupled networks to enhance the reliability of the entire system. Then we get the most effective swapping strategy in enhancing the robustness of the Cyber-Physical System compared to previous studies. Different systems’ structures would influence the performance of swap inter links strategies on improving the reliability of networks. Moreover, our work could guide how to optimize a Cyber-Physical System topology by reducing the influence of cascading failures.

DC smart grids enabled by the integration of advanced power electronic converters (PECs) can ease the integration and control of distributed renewable energy resources, electric vehicles, and energy storage systems. However, these highly flexible power systems introduce many challenges when considering the design of reliable, plug-and-play protection that does not rely on dedicated communications infrastructure for device coordination. One particularly difficult challenge is the management of dc-side filter capacitor discharge during short-circuit faults where the large peak fault-current produced can permanently damage exposed semiconductor components within the converter. One solution is to ensure that the trip-time of dc protection devices is sufficiently rapid (sub-millisecond) to guarantee that fault-current is blocked prior to reaching destructive magnitudes. However, such high-speed protection devices do not offer much margin for effective selectivity with downstream devices due to the narrow time window of operation. Accordingly, this paper proposes a non-unit protection scheme for future large-scale dc smart grid applications that increases this time-window of operation to enable improved selectivity whilst retaining a lower level of energy dissipated in the fault. Reliable protection coordination is demonstrated on a dc radial network and is realized using conventional millisecond trip-time devices, and a single solid-state microsecond trip-time device.

This paper proposes a fault (line-to-line) location on Ikeja West – Benin 330kV electric power transmission lines using wavelet multi-resolution analysis and neural networks pattern recognition abilities. Three-phase line-to-line current and voltage waveforms measured during the occurrence of a fault in the power transmission-line were pre-processed first and then decomposed using wavelet multi-resolution analysis to obtain the high-frequency details and low-frequency approximations. The patterns formed based on high-frequency signal components were arranged as inputs of the neural network, whose task is to indicate the occurrence of a fault on the lines. The patterns formed using low-frequency approximations were arranged as inputs of the second neural network, whose task is to indicate the exact fault type. The new method uses both low and high-frequency information of the fault signal to achieve an exact location of the fault. The neural network was trained to recognize patterns, classify data and forecast future events. Feed forward networks have been employed along with back propagation algorithm for each of the three phases in the Fault location process. An analysis of the learning and generalization characteristics of elements in power system was carried using Neural Network toolbox in MATLAB/SIMULINK environment. Simulation results obtained demonstrate that neural network pattern recognition and wavelet multi-resolution analysis approach are efficient in identifying and locating faults on transmission lines as the average percentage error in fault location was just 0.1386%. This showed that satisfactory performance was achieved especially when compared to the conventional methods such as impedance and travelling wave methods.

The implementation of superconducting fault current limiters (SFCL) in the electrical power system requires the coordination of its parameters with the installed power system protection (PSP), in particular when using automatic reclosing (AR). The crucial parameter for AR is the recovery time of the SFCL, understood as the SFCL return time to the superconducting state after its operation. This time will depend mainly on the efficiency of the cooling system and the heat dissipation processes in the electrical insulation system. This article presents the results of experimental research on the return time to the superconducting state of superconducting tapes with layers of electrical insulation of various thicknesses. The tests were carried out in conditions in which the density of energy generated during the surge current flow correspond to the operating conditions of superconducting material in SFCL. Also, the transfer of this energy to liquid nitrogen corresponds to phenomena occurring in SFCL. The recovery time of several types of high temperature superconducting tapes in the zero current state and recovery under load were determined. The range of the load current at which it is possible return to the superconducting state was determined for tapes with and without electrical insulation. It has been shown that the analysis of these processes must take into account the strong dependence between the thermal energy transfer from the sample surface to liquid nitrogen and the type of nitrogen evaporation process on the surface of the sample. The presented research results are of particular importance for the functionality of SFCL and its cooperation with the PSP.

The flow of DC in AC networks leads to half-cycle saturation of power transformers that causes their internal heating, large draw of reactive power and ultimate grid collapse. Transformerless power electronics-based module integrated between the neutral and substation ground of traditional transformers has previously been proposed that provides power system protection against DC flow in grid along with a variety of advanced grid-support features. The technique has already been tested and verified on a controller hardware-in-the-loop (C-HIL) platform. In this paper, the proposed strategy is evaluated on a laboratory scale hardware prototype utilizing Typhoon power hardware-in-the-loop (P-HIL) strategy. The experimental results verify the promising performance of the proposed scheme in nullifying the effect of DC injection, performing harmonics isolation and voltage regulation. Also, an effective transformer and converter protection scheme utilizing a hybrid AC/DC solid-state switch has been proposed and evaluated in this paper.

Traditionally, distribution networks were designedfor unidirectional flow of electricity, but due to integration of distributedenergy resources there is bidirectional flow of power inthe system. This bidirectional flow of power has given rise to newchallenges in the distribution network. These challenges includevoltage variations, fairness issue, protection problems and powersystem stability. Grid operators also require that all convertersconnecting these distributed energy resources with distributionnetwork should have the fault ride through capabilities for systemreliability. In this paper a summary of these challenges occurringdue to integration of distributed energy resources in distributionnetwork is described. Also, a review about the solutions for thesechallenges available in literature is presented.

At present, the entire world is moving towards digitalization, including in the electric power industry. Digitalization is in its heyday and a lot of articles and reports are devoted to this topic. At the same time, the least digitalized of the electrical networks are distribution networks that account for a very large share in electric power systems. The article proposes a methodology for creating a flexible distribution network based on the use of digital technology. Additionally, we elaborate a methodology with the identification and collection of the necessary information to create digital networks, develop ways to adapt the required equipment, and suggest methods of recognition of some short circuits. Furthermore, we address the issue of reliability of the information obtained from digital devices, develop a technique for arranging the devices to cover the entire network as required to improve the power system protection of electrical power distribution networks. The above measures make it possible to ensure the flexibility of the active distribution network, as well as to adjust the parameters of the actuation of power system protection depending on changes in external conditions and in the event of emergencies. We propose a technique for controlling the distribution network, based on the factoring-in of the type of damage during an emergency in real time, as well as a technique for arranging the measuring devices and the creation of an information and communication network. We provide recommendations for the design and operation of electric power distribution networks with digital network control technology.

The article discusses the development of the "Network Analytics" system for analyzing oscillograms with power system protection, which will automatically collect and aggregate data on a remote server and display possible causes of accidents on power lines based on intelligent analysis. The article provides the structure of the system, the general algorithm of work and describes the main modules. The work algorithms of the module for analyzing emergency data from high voltage stations are shown. A test version of the system based on a user web interface is presented, which displays data in real time from a laboratory stand, as well as displays alarm oscillograms and indicates possible causes of failures.

Distance relay is the main type of relays used for transmission lines protection, as it can detects the faults from long distance and it is fast response compared to other relays, also protection zones can be applied to distance relay in order to provide backup protection for other transmission line relays. The operation of distance relay depends on measuring the line impedance and compare it to trip condition. However, the operation of distance relay can affected by some conditions and one of these conditions is renewable energies. Renewable energies sometimes affect relay operation depending on penetration level as it causes wrong detection of fault location seen by the relay. In order to avoid that problem relay setting needs to be changed. The model of system will be simulated by using Matlab/Simulink. Where single line-to-ground and line-to-line faults will be applied in the transmission lines to verify distance relay performance in presence of renewable energies. Zones of protection by distance relays will be studied in order to detect the impact of renewable energy on fault location seen by the relay. ACKNOWLEDGMENT This work was supported by the National Priorities Research Program under Grant 11S-1125-170027 from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

In this paper, a developed and smart protection scheme for the electrical power transmission grid is proposed. Naturally, the electrical power transmission system protection scheme contains two major parts, such as external protection scheme and internal protection scheme. The external scheme consists of basic physical protection systems like open circuit, short circuit, and over voltage protection scheme. In contrast, the internal system includes symmetrical faults and unsymmetrical faults. In this research paper, the external protection system is described. Moreover, the earthquake protection system and temperature protection system are introduced additionally in this development scheme. These additional features provide extra protection in the power transmission grid system against earthquake and fire incidents. The `Internet of Things’ (IoT) is introduced here to digitize the electrical transmission grid technology. With this, the data acquisition will become faster and it will build reliability between the user and supplier.

The cascading failure is a typical failure propagation process which can cause significant consequence to the power system. It can be triggered by the vulnerable set composed of combinations of transmission lines with specific failures. So it is of great significance to identify the vulnerable set. In this paper, we propose an identification model for the vulnerable set under deep learning framework. The main part of the model consists of autoencoder and classification network for reducing dimensionality and identifying vulnerable set respectively. The model is trained by the data generated from cascading failure simulation platform. We conduct experiments on IEEE 30-Bus and 200-Bus systems with different initial failures to validate the identification and generalization capability. And the time consumption is also discussed to demonstrate the efficiency of the model. All of the indicators prove that the model is capable of identifying the vulnerable set effectively.

Once a cyberattack sabotages the integrity of the supervisory layer, commands including active and reactive power setpoints issued by this layer could not be trusted anymore, whereas the distributed energy resources (DERs) must autonomously stay supplying the loads across the grid to prevent cascading failures. In this paper, a comprehensive cyberattack resilient control framework is proposed. After an effective attack on the supervisory layer is detected, the entire grid is clustered into the predefined boundaries. The confined communications within the shaped-up clusters certifies the minimal communications. To ensure compliance with grid integration standards like IEEE 1547, the proposed distributed control framework identifies the physical formation of the grid via pseudo random binary sequence impedance identification (PRBSII) technique and reacts accordingly to support the voltage across the grid to keep it within the predefined boundaries. The proposed cyberattack resilient control framework is validated with simulation under various case studies.

Protection relays are essential components in distribution networks that are used to protect the interphase faults and single-phase-to-ground faults. However, these relays do not assurance the protection due to the sharp growing short circuits. They may be the result of demanding more and more power usage by the commercial and residential users. Overcurrent relay (OCR) is the cost-effective and broadly used element in power system protection. In this paper, the design of an overcurrent relay in 0.18μm CMOS standard technology is performed for the protection of the 10-kilo-volts distribution system against the undesired currents. In this case, we have considered a time-reversed type relay where the operation time of the relay has a reverse proportion with its current. Firstly, crucial features of the relay are converted into digital data using electronic circuits including; encoder, analog to digital converter (ADC), multiplier, etc. In the next step, using an analog comparator leads to having the results of the comparison between the relay nominal-current and the actual line current. Finally, the value and the duration of the overcurrent are compared with the relay characteristics and the output results will ensure the circuit to continue the operation or not. Therefore, the proposed relay guarantees the protection of the system by overcurrent detection and cutting-off the system in the critical situations in a safe and fast way. Simulation results through Hspice can strongly prove the proper operation of the proposed overcurrent relay.

The integration of offshore wind farms has revitalized the interest in multi–terminal high voltage direct current (M–HVdc) transmission grids. HVdc breakers’ importance has increased as M–HVdc grids are now a commercial truth. Several HVdc circuit breaker technologies have been developed, published, and appeared as prototypes for HVdc networks. This paper summarizes the HVdc breaker technologies from the last two decades, distributed mainly in literature. A comparison of various state–of–the–art HVdc breakers is presented. Further, areas are identified where further research and development are required. The goal is to provide primary challenges and prospects in the HVdc breaker field.

Microgrids have gathered a significant amount of attention within the past decade and becoming an essential asset in the energy industry. The ability to integrate sustainable energy generation methods into the distribution network is one of the main reasons for microgrids popularity. A wide variety of Distributed Generation (DG) including wind and other micro-turbine generation, photovoltaic generation along with energy storage, makes the microgrid viable in both grid-connected and islanded modes while reducing the power losses. There are various technical challenges to be tackled in order to harvest the full potential of microgrids, and protection is one of them. Various solutions were introduced, driven by the development of protection techniques. One of the most promising approaches for microgrid protection is adaptive protection. This paper contains a systematic review on adaptive protection of microgrids, including a wide range of applicability variants, their strengths, and drawbacks. It also explores the state-of-the-art researches that utilize computational intelligence to achieve adaptive protection. These solutions are currently at the verge of totally redefining protection solutions with a more flexible and reliable system that will be applied globally.

This study presents a method to place, size, coordinate and adequate protection systems in distribution networks (DNs) with directly-coupled distributed generation (DG). DG penetration increase in DNs is beneficial to the operation of these grids. However, since the majority of DN is already consolidated, with protective devices sized for certain current levels and directionality, adding DG to these systems may cause issues. This study introduces a method to determine protective devices placement, their coordination and sizing, depending on DG location. Direct-coupled DG is considered since DG connected to DNs through power electronics limit the fault current to the network. Firstly, recloser allocation is treated in a multiobjective approach, reducing reliability indices. To solve this problem, particle swarm optimization is applied. Fuse cutouts allocation is determined by a set of rules, developed considering feeder particularities. After, DG is considered and its effects on the protection coordination are evaluated. To adapt DN to receive DG, fault current limiters are placed to avoid recloser – fuse miscoordination. Finally, recloser operation is analyzed to determine the operational philosophy to avoid misoperation in the presence of DG. Graphical and numerical results are presented for test systems to show the functionality and performance of the proposed method.

Current research on cascading model for wireless sensor networks (WSNs) fails to consider the impacts of the sink node on network traffic distribution, which makes them unable to properly reflect the sink-convergence feature of WSNs. In this paper, we build a more practical cascading model for WSNs, in which the load function is defined on each node according to a new traffic metric directional betweenness, and the overload function is defined according to the congested state of each node. In addition, the failed node can recover via reboot after a certain time delay rather than being permanently removed from the network. Simulation results show that the network invulnerability is positively correlated with the overload-tolerance coefficient and negatively correlated with the congestion-tolerance coefficient, and the extension of the recovery time will exacerbate the fluctuation of the cascading process. Moreover, placing the sink node close to the center of the deployment area can contribute to the network invulnerability.

Despite the fact that current research related to the invulnerability of wireless sensor networks (WSNs) against cascading failures has made some progress, most of it focuses on the peer-to-peer structure, which is far from the reality. In this paper, we build a cascading model of clustering WSNs by introducing the concept of sensing load and relay load. We discuss the impacts of model parameters on network invulnerability and evaluate the invulnerability performance of two types of WSN topologies, i.e., scale-free network and random network. Simulation and theoretical results show that the network invulnerability is negatively related to the proportion of cluster heads and positively related to the allocation coefficient. When the degree of each sensor node bears a linear relationship with its initial load, the network invulnerability is strongest. Moreover, to alleviate the damage level caused by cascading failures, we design capacity-expansion schemes and indicate the recommended model parameter settings for each scheme.