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The electrical protection of power networks with fault contribution from inverter-based power sources imposes new application challenges that have to be dealt with by protection engineers. This paper describes the development of a study case model of an HVDC-MMC link for testing the protection behaviour of connected converter transformers. The paper summarises the implementation and validation of the converter control as well as enhancements to provide Fault Ride-Through capability and fast fault current injection as required by the German Technical Connection Rules for HVDC. The grid code standard requires positive- and negative-sequence reactive current injection in the case of grid faults. A Doubled Decoupled Synchronous Reference Frame Phase Locked Loop (DDSRF-PLL) for Vector Current Control (VCC) is implemented. Additionally, a Fault Detection and Fault Ride-Through Reference Generator with a Current Limitation strategy is introduced. Though these techniques are well described in the literature, the DDSRF is improved for current control stability. The relationship between the parameters of the PLL and the control, as well as the behaviour of the protection system, are demonstrated. Grid faults with large voltage dips pose a significant challenge to the stability of the control system. Nevertheless, it is shown that with the developed model, it is possible to make general statements about the protection behaviour in an inverter-based environment. [ABSTRACT FROM AUTHOR]

In this paper, a novel high temperature superconducting (HTS) thin film device as planar levitator and fault current limiter is firstly proposed and tested. Nowadays, planar magnetic levitation (maglev) levitator (PML) employed in planar maglev system is a promising high-precision positioning mechanism for modern high-end industrial fields, due to the attractive features of noncontact, zero friction, high precision, light weigh, simple structure, high reliability, fast response and fewer interfering factors, etc. In contrast to other maglev technologies, HTS maglev technology has the advantages of passive self stabilization levitation, light weight, high vacuum gain, simple structure, energy saving and no electromagnetic pollution, etc. Thus, the PML fabricated by HTS thin film can further simplify the system control strategy and improve operation efficiency. In this paper, we designed and fabricated the double sided YBa2Cu3O7-x thin film based PML and analyzed its levitation force characteristics. Besides, we also tested its fault current limiting performance, which can be employed to limit the fault current in the planar maglev system. It can be found from the experimental results that, the HTS-PML can offer the levitation force more than 400 kN/m3 and 100 N/kg, meanwhile, it can also generate the quench resistance more than 15 Ω to limit the fault current effectively. This work is perspective for the future planar maglev applications, to improve the system compactness, stability, reliability, miniaturization and lightweight with multifunctional integrated design. [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]

The occurrence of short-circuit faults in AC/DC microgrids gives rise to exceptionally high currents with rapid escalation, particularly in DC feeders where current zero-crossing is absent. This study introduces a comprehensive design procedure for a solid-state breaker tailored to address this challenge. A key innovation of the proposed solid-state circuit breaker lies in the incorporation of a current limiter reactor, which effectively constrains the current flow in both the load commutation switch and main breakers. Additionally, the inclusion of a resistive branch diminishes energy dissipation in the main breakers, safeguarding them against voltage stress. Consequently, the operational efficiency of the breaker is significantly enhanced, ensuring swift and efficient fault current interruption in vulnerable AC/DC microgrid scenarios. The efficacy of the proposed solid-state breaker was rigorously examined through analytical studies, and the results were validated using MATLAB/Simulink simulations. This breakthrough design represents a promising advancement in the realm of microgrid protection, offering a robust solution for mitigating the impact of short-circuit faults in AC/DC systems. [ABSTRACT FROM AUTHOR]

This paper presents a state‐space average model of a three‐level photovoltaic (PV) inverter to understand short‐circuit currents transient characteristics. Analytical solution of the model is also derived. The proposed model is validated with PV system controller hardware in‐loop (HIL) test method. The errors between simulation and HIL tests results under various conditions are evaluated, testifying the validity of the proposed model. With the model and analytical solution, the decaying time constants of sub‐transient and transient processes are derived, which shows that the time constants of a three‐level PV inverter are not fixed and they vary with voltage dips. The analytical expression of short‐circuit currents is also formulated. The findings from this study are essential to short‐circuit current calculations of a power grid with large‐scale PV plants, coordination of power system protections, and grid planning. [ABSTRACT FROM AUTHOR]

Five‐phase permanent magnet synchronous machine (PMSM) can operate under open‐circuit faults with the appropriate current regulations. However, the traditional current regulations based on the five‐phase half‐bridge inverter have to satisfy the constraint of zero neutral point current, which limits the fault‐tolerant performance of the machine. Thus, this paper investigates the current regulation based on the five‐phase six‐leg (FPSL) inverter, which relieves the zero‐neutral point current limitation, and both current regulations considering the maximum torque (MT) and minimum copper loss (MC) are derived under different open‐circuit conditions. The cost of the system has increased, but with the new regulations, better fault‐tolerant operation capability of the machine can be obtained under all kinds of open‐circuit faults. Moreover, with the introduction of the neutral point current, the machine can work under triple‐phase open‐circuit faults. In conclusion, the proposed control scheme based on the FPSL inverter expands the fault‐tolerant operation capability of the five‐phase PMSM. The experiment results prove the effectiveness of the proposed current regulation on increasing average torque or reducing copper loss under fault‐tolerant operation. [ABSTRACT FROM AUTHOR]

Fault detection is an important part of aeroengine health management. Intelligent fault detection methods represented by machine learning have been widely studied. However, most studies assume that training and test data follow the same distribution, which is unrealistic. Due to the degradation of engine performance or change of engine operating environment, the historical operation data of aeroengines are different from the current operation data of the engine. If the engine history operation data are directly used to train a fault detection model, the fault detection of the current engine may lead to low efficiency and affect the reliability of fault detection. In order to overcome this problem, transfer learning is introduced into aircraft engine fault detection in this paper. This paper combines transfer learning with support vector data description (SVDD), a common fault detection algorithm, and proposes SVDD-based transfer learning (SVDD-TL). This algorithm takes the spherical center of the SVDD as the knowledge structure to transfer from the source domain to the target domain, which can improve the detection accuracy of the model in the target domain. A fault detection experiment for an aeroengine was designed. Single and mixed fault data were used in the experiment, and the variation of fault data quantity was considered. Experimental results showed that the proposed method can improve the fault detection accuracy of the model in the target domain and still have good detection performance when the amount of fault data changes. [ABSTRACT FROM AUTHOR]

The work in this paper is applied to the Zhangbei Power grid. In the flexible direct current (DC) power system, the fault current rises extremely fast when a DC fault occurs. The requirements for the peak of breaking current and fault energy absorption of DC circuit breakers (DCCBs) increase linearly, which significantly increases the cost of the equipment. Therefore, in order to reduce the design difficulty of DCCBs, this paper proposes a strategy to control energy after the fault occurs. Firstly, the energy dimension is added on the basis of the traditional vector control of MMC, which constitutes a three-dimensional energy direct control. Subsequently, the architectures of energy fluctuation control and feedforward control are proposed. The influencing mechanisms for the peak fault current, peak fault voltage and energy dissipation are analyzed. Finally, the simulation of energy fluctuation control and feedforward control is constructed on PSCAD/EMTDC. The simulation results show that the energy fluctuation control is obviously better than the conventional three-dimensional energy control, and the feedforward energy control is further improved on this basis. Compared with the conventional vector control, the peak energy is reduced by 45.43% and the peak current is reduced by 25.39%, which helps to simplify the equipment design and reduce the equipment cost. [ABSTRACT FROM AUTHOR]

Currently, theoretical analysis of single‐phase grounding (SPG) faults in low‐current grounding systems has reached a high level of refinement, and the corresponding detection methods have matured. However, there is a significant lack of research on successive grounding (SG) faults, particularly in the area of detecting cross‐line same‐phase successive grounding (CSSG) faults in arc suppression coil grounding systems. To address these issues, a novel faulty line detection method based on transient characteristics of CSSG is proposed. Firstly, a transient equivalent circuit is established, and the characteristics of transient zero‐sequence current (ZSC) are theoretically analysed. Secondly, variational mode decomposition (VMD) is employed to extract low and high‐frequency information from intrinsic mode functions (IMFs). Subsequently, a fault initiation criterion based on kurtosis theory and the Teager‐Kaiser energy operator (TKEO) is proposed, which can accurately detect the occurrence time of secondary faults. Finally, a method for faulty line detection based on cross‐correlation distance (CCD) and transient energy (TE) is proposed. The results of PSCAD simulation under different conditions and field test affirm the accuracy of the analysis and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

There exist problems of hard coordination and threshold setting as well as low sensitivity in overcurrent relay due to the bidirectional and small fault current when distributed generators are integrated into the distribution network. This paper introduces ferrite rings (FRs) to act as boundaries of distribution feeders, and a peak time of voltage traveling wave‐based protection is proposed. The characteristics of FRs are analyzed and their feasibility as line boundary is validated. The fault characteristics of internal and external faults are analyzed when FRs are installed at both ends of the protected feeder. The results show that the peak time of the voltage travelling wave of the internal fault is far smaller than that of the external faults. According to the difference, the fault detection method and the protection scheme are proposed. Simulations in PSCAD and experiment validate that the proposed protection principle can reliably distinguish between internal and external faults. Besides, the proposed protection scheme has higher sensitivity compared to ROCOV‐based protection. [ABSTRACT FROM AUTHOR]

In order to improve the performance of sliding mode observer in detecting the state of induction motor, a state detection method based on particle swarm optimization (PSO)-backstepping (BS)-sliding mode observer (SMO) is proposed in this paper. In this method, the controller is constructed and the parameters of the control rate are optimized, so that the tracking accuracy and robustness of the new observer are improved relative to conventional observer, exponential observer, PI and PID. Firstly, the state equation of the induction motor under stator and rotor winding fault and stator current sensor fault is established. Secondly, the new sliding mode observer is designed using the backstepping method based on the new reaching law. Then, the new fitness function and PSO is used to optimize the parameters of the new sliding mode observer. Finally, the simulation comparison experiment of stator current state detection is carried out under the simulated fault condition of induction motor. The feasibility of the method is verified by comparing the state tracking situation and the state detection error. The comparative experimental results show that the method has less jitter, stronger robustness, and higher state tracking accuracy when detecting stator current states under different faults. [ABSTRACT FROM AUTHOR]

This paper proposes a longitudinal protection scheme utilizing empirical wavelet transform (EWT) for a throughtype cophase traction direct power supply system, where both sides of a traction network line exhibit a distinctive boundary structure. This approach capitalizes on the boundary's capacity to attenuate the high-frequency component of fault signals, resulting in a variation in the high-frequency transient energy ratio when faults occur inside or outside the line. During internal line faults, the high-frequency transient energy at the checkpoints located at both ends surpasses that of its neighboring lines. Conversely, for faults external to the line, the energy is lower compared to adjacent lines. EWT is employed to decompose the collected fault current signals, allowing access to the high-frequency transient energy. The longitudinal protection for the traction network line is established based on disparities between both ends of the traction network line and the high-frequency transient energy on either side of the boundary. Moreover, simulation verification through experimental results demonstrates the effectiveness of the proposed protection scheme across various initial fault angles, distances to faults, and fault transition resistances. [ABSTRACT FROM AUTHOR]

The integration of synchronous generators (SG) to the grid will present serious problems in some instances. The increase in fault current level is one of the most crucial issues, which causes miscoordination between directional over current relays (DOCRs), in addition to putting excessive pressure on the circuit breakers. This research uses the Fault Current Limiters (FCL) to restore coordination, without changing the settings of DOCRs, by reducing the level of fault current in the grid. The main goal of this research is to find the optimal size, location, and number of FCLs at the minimum cost and with the least operation time for the relays, using Jellyfish Search Optimisation (JSO) algorithm. This can be achieved through three different approaches. The first one is optimizing the location, number, and impedance size of the FCL by minimising a cost function. The second approach involves optimizing the backup relay operation time. A combination of the two previous approaches is used as the third approach. The outstanding feature of this research is that it considers the optimal location of DG and FCL while optimizing the operation times of DOCRs, which is a new framework. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the fault current contributions of small‐scale single‐phase photovoltaic inverters under grid‐connected operation and their potential impact on the protection of distribution systems. To conduct this analysis, an autotransformer‐based voltage dip generator is proposed as a means to test the photovoltaic inverters' contribution to short‐circuit currents. Laboratory tests are then performed to obtain the short‐circuit current contribution of eight single‐phase photovoltaic inverters. Using the short‐circuit current data obtained, a behaviour model is developed and simulated on Matlab‐Simulink. The model is then applied to a real distribution system and case studies are conducted to simulate the potential impacts on the protection system. Results indicate that while the massive penetration of small‐scale single‐phase photovoltaic inverters can alter the protection system's operating time, the impacts are not significant. Only in very specific scenarios, such as events related to high impedance faults, some impact can be observed. In these situations, the presence of photovoltaic inverters further complicates the already difficult task of identifying high impedance faults through conventional overcurrent protections. This study provides valuable insights into the integration of photovoltaic inverters into distribution systems, and can aid in the development of effective protection measures for future grid designs. [ABSTRACT FROM AUTHOR]

There is growing concern regarding air pollutants (NOx, SOx, and PM) and carbon emissions from ocean-going vessels in harbor areas and the role of high-voltage shore connection (HVSC) systems in mitigating these emissions during vessel berthing. The HVSC operates as a TN grounding system in humid environments, and it needs a proper grounding design to ensure safety when faults occur. This article intends to examine the overvoltage resulting from fault currents and its implications for the safety of operators when a single line-to-ground fault takes place within the design of HVSC grounding systems. The assessment is carried out by employing actual scenarios and parameters from a container berth at Kaohsiung Harbor in Taiwan. Considering site conditions, such as the wet ground surface, human body resistance, and electric shock duration, the tolerable safe voltage level is derived using IEEE Std. 80 and IEC 60479-1. Based on the shore power system grounding architecture specified in IEEE/IEC 80005-1, an equivalent circuit model is constructed to calculate the fault currents using symmetrical component analysis. The actual touch voltages generated in various locations are analyzed under scenarios of connecting or disconnecting the equipotential bonding between the ship and the shore using neutral grounding resistor (NGR) designs. This article delves into the scenarios of electric shock that may occur during the operation of an actual container ship's shore power system. It evaluates whether various contact voltage values exceed current international standards and verifies the grounding design and safety voltage specifications of IEEE/IEC 80005-1. According to the results of this study, the use of NGR and protective earthed neutral (PEN) conductors in HVSC is crucial. This can limit fault currents, reduce touch voltage, and ensure the safety of personnel and equipment. Therefore, ensuring and monitoring equipment conductors and adopting NGRs of appropriate sizes are crucial elements in maintaining electrical safety in HVSC systems. [ABSTRACT FROM AUTHOR]

Wind turbines are vulnerable to negative sequence current injection, the conventional automatic reclosing scheme for wind power outgoing lines, since we may inject negative sequence components into the system and reclose it without distinguishing the nature of the fault through rectification. Moreover, reclosing in permanent faults could induce a secondary impact on the system. To solve the above problems, an adaptive reclosing scheme for cross-line faults on double-circuit wind power outgoing lines with shunt reactors is proposed. Firstly, a new tripping strategy and a single-side partial-phase reclosing method are proposed for multiple types of outgoing line faults, while, simultaneously, phase-to-phase coupling loops are established. Secondly, the criteria of fault nature are established based on the fault phase shunt reactor current and fault phase voltage characteristics, and transient faults are rapidly and accurately distinguished from permanent ones according to the criteria. Finally, the theoretical derivation and simulation experiments are conducted on the PSCAD/EMTDC platform to demonstrate that the proposed adaptive reclosing method is applicable to avoid the injection of negative sequence currents into wind turbines. Meanwhile, the success rate of reclosing for wind power outgoing line is significantly improved and the continuity of power transmission on the wind farm(s) is ensured. [ABSTRACT FROM AUTHOR]

Inversion tectonics, in which old normal faults act as reverse faults in current stress fields, are frequently observed in northeastern Japan (Tohoku District); however, the conditions that control these fault activities remain unclear. To improve the identification of faults that are more favorable to slip under current stress conditions, the regional fault mechanisms in the Tohoku District must be better understood. The stress field in the Tohoku District and the likelihood of fault activities were thus estimated using slip tendency (ST) analysis. The results show that in the eastern margin of the Japan Sea (EMJS), the reverse fault type is dominant in the stress field. The maximum horizontal direction changes clockwise from E–W to NW–SE from the northern to the southern regions and counterclockwise from NW–SE to E–W from the Japan Sea to the inland area. In the Tohoku inland area, the estimated direction of the maximum horizontal axis changed after the 2011 Tohoku-Oki earthquake, from E–W to WNW–ESE. ST values were calculated for seven events in the EMJS area. To avoid the influence of the Tohoku-Oki earthquake, only stress field data prior to the 2011 Tohoku-Oki earthquake were used to determine ST values for four of the events in the Tohoku inland area. The results showed eastward-dipping fault planes with low dip angles (approximately 30°–45°) and large ST values (approximately > 0.7). The large ST values indicate that the stress field fault is favorable to slip and the results were consistent with the actual fault plane in the EMJS area. However, in the Tohoku inland area and the southern part of fault model of the 1993 Hokkaido Nansei-Oki earthquake, fault planes with large ST values were found to be inconsistent with the slipped fault plane, thus indicating that slipping was unfavorable. The regional differences are consistent with the volcano distribution and thus, the fluid supply from volcanic activity may have helped the fault slip under difficult stress conditions. [ABSTRACT FROM AUTHOR]

In the field of fault isolation and clearance in flexible DC power grids, hybrid DC circuit breakers (HDCCB) have been widely used because of their advantages. However, their development is limited by high construction costs and inapplicability in some fault cases. In addition, adaptive reclosing capability is required for overhead DC lines with high fault probability. Therefore, this paper proposes a new type of multi-port hybrid DC circuit breaker (MP-HDCCB) with current limiting, breaking, and self-charging capabilities. The capacitor polarity reversal circuit is designed to reduce the influence of capacitor pre-charging on the normal operation of the system and to solve the problem of two consecutive line faults occurring in a short period of time. In addition, the circuit breaker can limit the current and break in the face of a single line fault, multiple line faults at the same time, and bus faults. It also has the ability of adaptive reclosing and normal operation of the line after a bus fault. Based on the proposed topology, a 500 kV four-terminal DC system is designed, and a model is established in PSCAD/EMTDC to verify the capabilities of the circuit breaker. Results show that the circuit breaker has adaptive reclosing capability and can realize fault current limiting and breaking under different fault conditions. [ABSTRACT FROM AUTHOR]

In recent years, with the rapid development of high-voltage flexible direct current (DC) transmission systems, more and more multi-port high-voltage DC systems have been successfully put into operation. Therefore, the number of connecting ports on the DC bus is gradually increasing, which necessitates higher requirements for clearing fault current. To better protect the DC power grid, this paper integrates a DC fault current limiter with a multi-port DC circuit breaker. This article proposes a modular cascaded multi-port hybrid DC circuit breaker topology. It also elaborates on the topology structure, working principle, and control program under three different fault conditions. It completes the theoretical derivation and analysis of the circuit breaker fault isolation process, as well as the parameter design of the core components. Finally, a model is established in PSCAD/EMTDC for simulation verification. The application performance of the circuit breaker in four-terminal DC systems is studied and analyzed, and the current-limiting effect of the multi-port DC circuit breaker proposed in this article is demonstrated. In addition, the disconnection performance and energy consumption of the arrester have been improved to a certain extent, which has good feasibility and economy. [ABSTRACT FROM AUTHOR]

Deep learning-based fault detection and diagnosis (FDD) methods have received considerable attention, and many methods based on convolutional neural network (CNN) have been applied to fault diagnosis for chemical processes. However, current fault diagnosis methods train and detect all faults using a single model and the same feature inputs, resulting in the neglect of correlations and difference between faults and inferior fault diagnosis performance. In this study, a novel fault diagnosis method named triage-based convolutional neural network (TrCNN) for fault diagnosis is proposed. Initially, the fault set is partitioned into distinct triage types. Subsequently, distinct models are formulated and applied to their respective triage types in the sub networks layer, while a triage network is developed in the triage layer. Ultimately, the models from the triage layer and sub networks layer come together to constitute the triage fault diagnosis system. The proposed method can adaptively select suitable models and features for different triage types, leading to improved diagnostic accuracy, especially for similar faults. When applied to the Tennessee Eastman (TE) chemical process the TrCNN demonstrates impressive performance, validating its effectiveness in fault diagnosis. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents the impact of adding single-phase photovoltaic systems on the fault current of short-circuit faults in asymmetric 400 V low-voltage feeders. This study also attempts to investigate the impact of various parameters on the fault current, such as the penetration coefficient of photovoltaic systems, the impact of downstream or upstream fault on the system installation location, and distance of photovoltaic systems and fault location. Simulations were carried out in the DIgSILENT software. The results show that the fault current will be more different when using photovoltaic systems and that difference is sometimes incremental and sometimes decremental. Therefore, if the penetration coefficient of the system is high, it will sometimes have a significant impact on the protection system. [ABSTRACT FROM AUTHOR]

Detecting and locating high impedance faults (HIF) in overhead distribution networks (ODN) remains one of the biggest challenges for manufacturers and researchers due to the complexity of this phenomenon, where the electrical current magnitude is similar to that of the loads. To simulate HIF, the selection of the HIF model is important, because it has to correctly reproduce the characteristics of this phenomenon, so that it does not negatively influence the simulations results. Therefore, HIF models play a fundamental role in proposing solutions and validating the effectiveness of the proposed methods to detect and localize HIF in ODN. This paper presents a systematic review of HIF models. It is intended to facilitate the selection of the HIF model to be considered. The models are validated based on experimental data from medium voltage (MV) laboratories, specifically, recorded waveforms from two HIF tests conducted in an MV lab were analyzed and compared with three established HIF models. The efficacy of these models was assessed against MV lab test data to ensure a precise representation of both transient and steady-state conditions for fault conductance and current waveforms. The findings show that the two nonlinear resistor models better approximate the waveforms obtained in the experimental tests performed in this study. [ABSTRACT FROM AUTHOR]

Intelligent motor fault diagnosis in industrial applications requires identifying key characteristics to differentiate various fault types effectively. Solely relying on statistical features cannot guarantee high classification accuracy, while complex feature extraction techniques can pose challenges for industry practitioners. Conversely, advanced feature extraction may not ensure that the model effectively learns these features for classification. A feature fusion approach that combines statistical and deep learning features to address these challenges is proposed. Since statistical features form the foundation for general feature extraction, statistical and deep learning features are combined using Extreme Gradient Boosting (XGBoost) algorithm with Particle Swarm Optimization (PSO). The PSO algorithm automates parameter tuning for XGBoost. A deep neural network (DNN) adaptively extracts hidden features, improving bearing fault classification precision using t‐SNE representation. Results successfully prove the DNN's ability to classify diverse motor faults using deep learning features. Thus, integrating statistical features with XGBoost further enhances DNN's performance. To ensure robustness, the proposed method has been compared with different motor fault classification methods and validated across different motor fault datasets, showcasing improved classification accuracy and robust performance, even amidst varying noise levels. This approach represents a promising advancement in intelligent fault diagnosis within industrial contexts. [ABSTRACT FROM AUTHOR]

A fault in a power system is an anomalous state that must be recognized as soon as feasible. To minimize the repercussions of the fault, such as damages occurred to the device, loss of tangible assets and loss of human resources, it is critical to notice the problem promptly. In a power distribution system, there are several approaches for detecting different types of faults. In this paper, a neoteric approach using Bayesian optimized Convolutional Neural Network is used to detect and classify different symmetrical as well as unsymmetrical faults in power distribution systems. The effectiveness of the proposed CNN model is validated for an IEEE 13 bus radial distribution system grid modeled (and simulated) in PSCAD. Time series of the measured 3-phase fault currents (for eleven different categories of faults) are used to create training & testing data. This data has been imported in MATLAB software to develop a CNN classifier (whose hyper-parameters are optimized by using a Bayesian optimizer) for faults in power distribution system, under distinct fault situations by varying fault resistance, faulty node and fault inception angles. Findings of simulation clearly indicate that proposed model has very high categorizing accuracy and is superior and competitive to other techniques available in literature. [ABSTRACT FROM AUTHOR]

In view of the fact that the influence of positive and negative sequence decomposition, which is widely used in positive and negative sequence decoupling control in control system, on the fault current calculation process is not deeply considered in the existing transient analysis methods of permanent magnet direct-drive wind farm short circuit current, this paper proposes a transient short circuit current calculation model that takes into account positive and negative sequence decomposition. The influence of the transient characteristics of positive and negative sequence decomposition on the control system is studied, and the mechanism of its action on the transient change of short circuit current is revealed. The positive and negative sequence decoupling processes of the circuit equation are modified, and the characteristics of the coupling equation are analyzed. The difference in the converter output voltage between the circuit equation and the control equation and the depth of its influence on the calculation process is revealed. On the basis of quantifying the difference at the converter output voltage, the circuit equation and the control equation are combined to form a short-circuit current calculation model with positive and negative sequence decomposition, which accurately characterizes the transient characteristics of fault current under different voltage drops and effectively improves the accuracy of the calculation results. [ABSTRACT FROM AUTHOR]

The non-linearly deterministic fault current characteristics with low current magnitude of high impedance fault (HIF) have thrown an inevitable challenge to the microgrid protection system. Moreover, differentiating HIF from non-fault events is also a challenging task under different operating scenarios of the microgrid. In order to address this, a simple and fast protection algorithm, based on Empirical Mode Decomposition (EMD) in conjugation with Teager-Kaiser Energy Operator (TKEO) is proposed in this article. This scheme process the current signals retrieved from both ends of the line through EMD, and subsequently, the current signal energy is extracted by TKEO. The incidence of a fault is affirmed by measuring the energy difference signal and estimation of entropy. By employing the second layer algorithm using entropy analysis, the non-fault disturbances, such as capacitor and load switching, temporary overloading, and DG outage, have been effectively distinguished from HIFs. The proposed technique is tested for grid-tied and autonomous microgrid operation modes with several HIF and non-fault cases. It is inferred that the proposed technique can detect and differentiate HIFs from other system perturbations seamlessly in less time. Compared to other methods, this scheme has procured excellent accuracy and reliability, and is also not affected by the dynamic current behavior of the microgrid. The PSCAD-EMTDC software is used to build and simulate the test system, and the MATLAB programming interface is utilized to develop and test the suggested method. [ABSTRACT FROM AUTHOR]

With the ongoing expansion and interconnection of electrical power systems, alongside the rapid proliferation of renewable distributed generations (DGs), the short-circuit extent in the power grid is experiencing a significant rise. Fault current limiters (FCLs) have been introduced in an effort to address this issue, ensuring the robustness and sustainability of expensive power system components when confronted with short-circuit faults. Among the various types of FCLs, bridge-type DC reactor fault current limiters (BDCR-FCLs) have emerged as one of the most promising options. While BDCR-FCLs have shown excellent properties in limiting harmful short-circuit currents, they are also advantageous in other respects. This paper investigates the supplementary functionalities of BDCR-FCLs as a multifaceted device towards the enhancement of the quality of supplied energy in terms of total harmonic distortion (THD) reduction, power factor (PF) correction, peak current reduction for nonlinear loads, and soft load variation effects, as well as their capability to limit fault current. To this aim, the capabilities of BDCR-FCLs have been studied through various simulated case studies in PSCAD/EMTDC software V5.0.1, in addition to experimental tests considering an AC microgrid connected to a DC system. The experimental and simulation investigations verify the superior multifaceted functionalities BDCR-FCLs introduce in addition to their excellent fault current-limiting capabilities. The results show that PF improved by 6.7% and 7%, respectively, in simulation and experimental tests. Furthermore, the current THD decreased by 20% and 18% in the simulation and experiment, respectively. [ABSTRACT FROM AUTHOR]

The reliability and stability of differential protection in power transformers could be threatened by several types of inferences, including magnetizing inrush currents, current transformer saturation, and overexcitation from external faults. The robustness of deep learning applications employed for power system protection in recent years has offered solutions to deal with several disturbances. This paper presents a method for detecting internal faults in power transformers occurring simultaneously with inrush currents. It involves utilizing a data window (DW) and stacked denoising autoencoders. Unlike the conventional method, the proposed scheme requires no thresholds to discriminate internal faults and inrush currents. The performance of the algorithm was verified using fault data from a typical Korean 154 kV distribution substation. Inrush current variation and internal faults were simulated and generated in PSCAD/EMTDC, considering various parameters that affect an inrush current. The results indicate that the proposed scheme can detect the appearance of internal faults occurring simultaneously with an inrush current. Moreover, it shows promising results compared to the prevailing methods, ensuring the superiority of the proposed method. From sample N–3, the proposed DNN demonstrates accurate discrimination between internal faults and inrush currents, achieving accuracy, sensitivity, and precision values of 100%. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for the removal of dual decaying DC offsets (DDCOs) to enhance discrete Fourier transform-based phasor estimation. The method proposed in this paper uses the sum of even samples and the sum of odd samples from the input signal to remove the AC components, thereby precisely estimating the primary and secondary DDCOs. The fluctuations induced by DCCOs present in the output of traditional DFT methods are eliminated by using the estimated DCCOs. The performance of the method was evaluated in terms of both mathematical-generated signals and fault current signals from a 154 kV Korean overhead transmission system. PSCAD/EMTDC was used to generate fault current signals at various fault distances and angles. The results show that the proposed method can estimate the phasor of the fundamental frequency component accurately regardless of the primary and secondary DCCOs. The paper concludes by describing the hardware implementation in a prototype unit that considers the real-world requirements of power system protection. [ABSTRACT FROM AUTHOR]

The transmission line is one of the most crucial electric power system components, demanding special attention since they are subject to failures that can cause disruptions in energy supply. In this scenario, the fault location emerges as a fundamental task, providing an approximate position where the failure occurred in the line. This paper presents a method for fault location using a novel dynamic regressor selection (DRS) framework, in which we introduce embedded normalization, incorporating the data scaling process inside the framework. The DRS aims to select the most accurate models from a pool of regressors to predict the fault distance. Moreover, since there is a lack of a public dataset, this paper presents and makes a new fault dataset available to the scientific community with several features extracted from current and voltage signals of representative failure events. In our experiments, we demonstrate the importance of this embedded normalization as well as the significance in the variation of critical hyperparameters of the DRS strategy, such as the distance metric used to define the region of competence and the criterion to select the best regressors from the pool of predictors. This work also presents the definition of the oracle concept in DRS, which represents the ideal predictor selection scheme. The results demonstrate the effectiveness of the proposed method with a mean error of 0.7086 km ± 0.0068 km, representing 0.1712% ± 0.0016% of the transmission line extension (414 km). [ABSTRACT FROM AUTHOR]

Currently, in modern wind farms, the doubly fed induction generator (DFIG) is commonly adopted for its ability to operate at variable wind speeds. Generally, this type of wind turbine is controlled by using two converters, one on the rotor side (RSC) and the other one on the grid side (GSC). However, the control of these two converters depends mainly on current sensors measurements. Nevertheless, in the case of sensor failure, control stability may be compromised, leading to serious malfunctions in the wind turbine system. Therefore, in this article, we will present an innovative diagnostic approach to detect, locate, and isolate the single and/or multiple real-phase current sensors in both converters. The suggested approach uses an extended Kalman filter (EKF) bank structured according to a generalized observer scheme (GOS) and relies on a nonlinear model for the RSC and a linear model for the GSC. The EKF estimates the currents in the converters, which are then compared to sensor measurements to generate residuals. These residuals are then processed in the localization, isolation, and decision blocks to precisely identify faulty sensors. The obtained results confirm the effectiveness of this approach to identify faulty sensors in the abc phases. It also demonstrates its ability to overcome the nonlinearity induced by wind fluctuations, as well as resolves the coupling issue between currents in the fault period. [ABSTRACT FROM AUTHOR]

This paper introduces a fault location technique for multi-section combined transmission lines, utilizing unsynchronized fault record data. The approach determines the intersection points of the voltage magnitudes computed using the fault current and voltage records of each terminal and the constant line parameters of each section. Finally, the real fault location is identified based on the calculated inverse angle of equivalent impedance. To evaluate the performance of the proposed algorithm, a three-section combined transmission line is constructed using the PSCAD/EMTDC software version 5.0.0, and various fault scenarios are simulated and tested employing the proposed algorithm. The results indicate that the proposed algorithm is applicable to various types of faults in a multi-section combined transmission line; the estimations are accurate. [ABSTRACT FROM AUTHOR]

Various methods are used to reduce fault currents in fault situations occurring in power systems. In this study, a developed single-phase power electronics-based solid-state fault current limiter is presented. The proposed single-phase solid-state fault current limiter is designed as preliminary prototype of the three-phase low voltage solid-state fault current limiter. The maximum current and voltage capability of the fault current limiter is 16 A and 480 V. This limiter works according to the principle of series and parallel resonance. In normal operation, the current passes through the inductance and capacitor, which are in series resonance. Thus, extra voltage drops and power loss in the system are prevented. In the event of a fault, the limiter switches to parallel resonance, and its impedance increases. Therefore, the fault current is decreased. The developed circuit and control algorithm reduces the first peak of fault current with a rather high percentage by comparison with the fault current without fault current limiter. In addition, the amplitude of current oscillation is decreased, and the current is recovered in a short time because the control algorithm determines the fault start and end time fast. The effect of the limiter is demonstrated with the simulation results in Matlab/Simulink. The simulation results are verified with the application study carried out in the laboratory environment. The fault current reaches up to 58.5 A in case of fault current limiter is not used, whereas the developed fault current limiter suppresses the current to around 9 A. The value of maximum fault current decreases to 15% according to the non-fault current limiter used situation. In the study, detailed application notes of the limiter circuit are shared. [ABSTRACT FROM AUTHOR]

Automated fault detection and diagnostics analysis in commercial building systems using machine learning (ML) can improve the building's efficiency and conserve energy costs from inefficient equipment operation. However, ML can be challenging to implement in existing systems due to a lack of common data standards and because of a lack of building operators trained in ML techniques. Additionally, results from ML procedures can be complicated for untrained users to interpret. Boolean rule-based analysis is standard in current automated fault detection and diagnostics (AFDD) solutions but limits analysis to the rules defined and calibrated by energy engineers. Boolean rule-based analysis and ML can be combined to create an effective fault detection and diagnostics (FDD) tool. Three examples of ML's advantages over rule-based analysis are explored by analyzing functional building equipment. ML can detect long-term faults in the system caused by a lack of system maintenance. It can also detect faults in system components with incomplete sets of sensors by modeling expected system operations and by making comparisons to actual system operations. An example of ML detecting a failure in a building is shown along with a demonstration of the soft decision boundaries of ML-based FDD compared to Boolean rule-based FDD analysis. The results from the three examples are used to demonstrate the strengths and weaknesses of using ML for AFDD analysis. [ABSTRACT FROM AUTHOR]

When the overhead line passes through the forest area, the conductor may contact the line to induce the tree-contact single-phase-to-ground fault (TSF), and the persistence of TSF may induce wildfires, bringing serious consequences. However, the amount of TSF electrical features is weak, and traditional protection devices cannot operate effectively, so it is urgent to obtain typical characteristics of TSF. In this study, the simulation experiment is carried out for the tree-contact single-phase-to-ground fault. Firstly, the relativity between fault and characteristics like zero-sequence voltage, zero-sequence current, and differential current are analyzed theoretically. Then, the simulation experiment platform of TSF is built, and the time-varying fault characteristics are acquired. The experimental results show that the average value of the zero-sequence voltage, the amplitude of the power-frequency component of the zero-sequence current, and the amplitude of the power-frequency component of the first and end differential current can accurately reflect the fault current development trend of the single-phase contact tree fault of the conductor, and can be used as the typical characteristic quantity of TSF. The results of this study are helpful for further understanding the fault characteristics of TSF and provide theoretical support for the identification and protection design of TSF. [ABSTRACT FROM AUTHOR]

The article presents the results of research in the field of limiting the effects of overvoltages and improving the conditions for the self-extinguishing of transient faults in medium voltage networks with earth fault current compensation. The aim of the research was to estimate the level of overvoltages generated by an earth fault during re-ignition of the electric arc and to assess the possibility of reducing them by increasing the attenuation of the earth fault circuit. The results of the conducted tests show that to increase the attenuation, which ensures a significant effect of limiting such overvoltages, it is enough to change the way of operation of the devices forcing an additional active component of the earth fault current (AWSCz/ACFA). In Poland, such devices are commonly used to improve the effectiveness of earth fault protection. It was also found that the proposed solution enables accurate tuning of the Petersen coil in networks with natural asymmetry of earth capacitances. Therefore, changes in the operation of AWSCz/ACFA devices may have a beneficial effect on the limiting the effects of repeated ignitions during earth faults and, at the same time, enable the accurate tuning of the Petersen coil and increase its ability to extinguish arc-fed faults. Research and theoretical analysis of the issue were carried out on the basis of data characterizing the parameters of the earth fault circuits of the real 15 kV network. [ABSTRACT FROM AUTHOR]

Hybrid circuit breakers are the most promising circuit breakers among DC circuit breakers. Conventional hybrid circuit breakers complete fault current isolation by converting current to IGBT when fault current occurs. However, in this case, the fault current continues to increase, so the IGBT must be large enough to withstand this current. In addition, in the case of a method of detecting and operating a fault, a delay time of up to hundreds of microseconds occurs, and in a hybrid circuit breaker, this delay time is a very large value. To solve this problem, this paper proposes a hybrid Z-source circuit breaker that operates without delay for low-impedance faults. The proposed breaker is designed to reduce stress on IGBTs and mechanical switches by generating a current zero crossing, as well as to enable the breaker to trip quickly in high-risk cases such as low-impedance fault circuits. Due to the limited environment of the laboratory, we performed 600 V fault isolation experiments. As a result of the experiment, it was confirmed that the proposed circuit breaker successfully isolated the fault within 1.6 ms. The current limiting feature of the Z-source appears to reduce stress on the IGBTs and MOVs used, and it allows for faster fault isolation. [ABSTRACT FROM AUTHOR]

The phase‐locked loop (PLL) is a critical control module applied in the control system of renewable energy sources (RESs) to synchronize with the grid voltage. When a fault occurs, the dynamic response process of the PLL will generate a phase locking error, resulting in a mass of harmonic components in the fault current of the PV inverter, which further poses challenges to transformer differential protection. To address the challenges posed by the phase locking error in practical engineering applications, this paper proposes an improved scheme that uses a digital computer algorithm to record and store the pre‐fault voltage and introduces the limiting coefficient. Firstly, the memory voltage is used to eliminate the phase locking error of the PLL, thereby mitigating harmonic distortion in the fault current of the RESs and ensuring the reliability of the transformer differential protection. In addition, the limiting coefficient is introduced to eliminate the effect of the increased amplitude of the fault current caused by the memory voltage. The voltage reference value of the inverter is multiplied by an appropriate limiting coefficient k and then output to the physical system. Finally, the effectiveness of the proposed scheme is verified by MATLAB/Simulink simulation. [ABSTRACT FROM AUTHOR]

Earth faults is a challenging fault type to locate in resonant grounded networks due to their naturally low fault current, and the problem increases with an increased fault impedance. This paper describes the detailed implementation and laboratory testing of a method for detection, location and clearing of earth faults with very small fault currents. The method consists of two indicators used in the fault detection stage, where their simultaneous operation ensures selective fault detection and faulty feeder selection. One of these indicators also enables continuous fault indication throughout a sectionalizing process. The laboratory tests demonstrate that both indicators function as intended, and it is the current sensors which ultimately limit the attainable sensitivity. Faults up to 15 kΩ were detected successfully in the laboratory network based on phase current measurements, while the sectionalizing indicator showed much higher sensitivity and functioned as intended in a 50 kΩ fault. Measurements from one field test in a 22 kV network corroborate the laboratory results and demonstrate the expected earth fault indicator response. [ABSTRACT FROM AUTHOR]

With the rapid development of high‐speed railway, the auto‐transformer traction network (ATN) is also expanding. However, due to the improved performance of electric multiple units (EMUs) and the non‐linear relationship between impedance and ground fault distance, distance protection has limited coverage and cannot accurately locate the fault distance by measuring impedance. This paper presents a model of the ATN considering the presence of EMUs, which effectively demonstrates the characteristics of current distribution under the ground faults. Furthermore, a ground fault identification method based on multi‐terminal currents is proposed to enhance the accuracy of fault identification and differentiate faults and EMUs. The mapping relationship between current distribution and fault location is derived, and an accurate fault location method is proposed. Compared to existing methods, this method is not affected by EMUs and AT parameters. The fault identification and location scheme for ATN employs multi‐terminal synchronous information. Finally, through simulation and experimental setups, case studies have been conducted to verify the accuracy and robustness of the proposed method in various fault scenarios. Certainly, this research has significant application prospects in fault analysis and detection for HSR. [ABSTRACT FROM AUTHOR]

Tolerating hardware faults in modern architectures is becoming a prominent problem due to the miniaturization of the hardware components, their increasing complexity, and the necessity to reduce costs. Software-Implemented Hardware Fault Tolerance approaches have been developed to improve system dependability regarding hardware faults without resorting to custom hardware solutions. However, these come at the expense of making the satisfaction of the timing constraints of the applications/activities harder from a scheduling standpoint. This article surveys the current state-of-the-art of fault tolerance approaches when used in the context of real-time systems, identifying the main challenges and the cross-links between these two topics. We propose a joint scheduling-failure analysis model that highlights the formal interactions among software fault tolerance mechanisms and timing properties. This model allows us to present and discuss many open research questions with the final aim to spur future research activities. [ABSTRACT FROM AUTHOR]

This paper is based on the distribution characteristics of the protective layer current under the fault state of high-voltage cables, and discovers the monotonic variation law between the fault point position and the power frequency phase difference of the protective layer current at both ends of the cable fault section. A method for fault location using the phase difference of the protective layer current at both ends of the cable section is proposed. For a long cable line composed of multiple complete cross-connected sections, the cross-connected section can be located through the current power frequency phase difference P (section) at both ends of the metal sheath section, just like the section positioning within the complete cross-connected section. If P (section) ∈ (90°, 270°), then the section is a fault section; otherwise, it is a non-fault section. Finally, the relationship curve between the power frequency phase difference of the protective layer current at both ends of the fault section and the distance from the fault point is used to determine the fault location. [ABSTRACT FROM AUTHOR]

The reliability of modern building electrical systems are receiving increasing attention as they become more intelligent and complex. As the majority of building electrical systems use neutral point grounding, earth faults or short circuits can get worse over time and damage both the distribution system and the electrical equipment. To this end, the corresponding three phases and four categories, namely three-phase voltage, three-phase current after fault, three-phase voltage distortion rate, three-phase current distortion rate, a total of 12 dimensional fault feature vectors and 10 fault simulation types, were summarised and extracted in conjunction with the actual operating conditions of the system. Using traditional fault identification ideas and neural network algorithm as reference, a 12-dimensional fault feature vector is used as the model input to construct a building electrical fault diagnosis and detection model based on ELM algorithm. Results showed that the ELM-based model's classification accuracy for this experimental sample was 97.56 %, its AUC was 0.92, and its RMSE was 0.3521. These figures were higher than the classification accuracy and performance of the BP algorithm and GA-BP algorithm fault diagnosis models, and they also demonstrate better robustness and generalizability. The model also has a 97.27 % correct rate in fault discrimination, while the computation time is only 0.201 s, and its fault identification and diagnosis speed is faster than other algorithmic models. At the same time, this research model has a good fault monitoring accuracy of up to 98.6 % for building electrical systems. The research can provide a more sensitive, accurate and rapid fault monitoring method for the current building electrical system. It also improves the reliability of the building electrical system in a complex environment and achieves better protection of the system. This has a certain significance for the development of the building electrical industry. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) cable represents a promising solution for fulfilling the power demands of cities with large loads and high density. However, due to their connection to the distribution network, HTS cables are vulnerable to fault currents exceeding ten times their rated current, which poses a serious threat to both the safety of the cable and the operation of the grid. Considering the highly nonlinear nature of superconducting conductivity, this study develops a field–circuit coupling model to investigate the transient characteristics of distribution networks incorporating superconducting cables (DNSC). Firstly, a finite element model based on the two-dimensional H formulation was built to calculate the electrical and thermal parameters of the HTS cable. Subsequently, an equivalent circuit model of the distribution network was employed to estimate the short-circuit currents. Communicating via a co-simulation server, the superconducting cable current and distribution network impedance were updated in each step. Further, based on an actual DNSC system in Shenzhen, China, the highest quenching temperature of the cable and the maximum fault current of busbars were assessed. Finally, by integrating current limiters into the system, the withstand capability of the cable and busbars was determined, which indicates that the improved protection configuration can effectively suppress fault currents and ensure safe operation. Successfully applied to an actual distribution network, the co-simulation model utilizing the field–circuit coupling method addresses the challenges of solving highly nonlinear and time-varying systems, enabling transient analysis and protection research for the integration of superconducting devices into the conventional grid. [ABSTRACT FROM AUTHOR]

The application of 5G-based communication for pilot protection in a distribution network with distributed generators is becoming increasingly widespread, but the existence of a 5G communication transmission data delay adversely affects the rapidity and reliability of the pilot protection based on the principle of the traditional dynamic time warping distance (DTW) algorithm. Therefore, to address this problem, and according to the difference in fault currents between distributed generators and synchronous machines, a new scheme of pilot protection based on the principle of an improved DTW is proposed. The scheme firstly performs cosine transform on the fault current sequence, and then it normalizes the DTW value. Finally, the proposed scheme is verified via simulation. The simulation results show that, compared with the traditional DTW, the proposed algorithm has better anti-delay characteristics and a stronger anti-interference ability, and the scheme can quickly and reliably identify in-zone and out-of-area faults with strong noise resistance. Further, the action times for a single-phase ground fault, two-phase ground fault, two-phase-to-phase fault, and three-phase short-circuit fault were reduced by 2.9 ms, 4.54 ms, 5.81 ms, and 5.89 ms, respectively. In addition, it is also sui for a distribution network with a high wind and photovoltaic penetration rate. [ABSTRACT FROM AUTHOR]