Fault Current Research Articles

A Reduced-Order Observer-Based Method for Simultaneous Diagnosis of Open-Switch and Current Sensor Faults of a Grid-Tied NPC Inverter

This paper presents a reduced-order observer-based simultaneous diagnosis strategy for grid-tied neutral point clamped (NPC) inverters subjected to open-switch and current sensor faults. First, the augmented descriptor system is constructed for the NPC inverter to transfer the current sensor fault into a generalized state vector. Then, the matrix transformations are applied to decouple the open-switch fault from the inverter system state and the current sensor fault. Subsequently, a reduced-order observer is developed for the transformed augmented descriptor system to achieve simultaneous precise estimation of the phase current and the current sensor fault. Finally, using the estimation results, a diagnosis algorithm with an adaptive threshold is proposed, which can not only distinguish between current sensor faults and open-switch faults, but also locate the faulty power switch and estimate different types of current sensor faults. Experimental results and comparisons are provided to verify the robustness and effectiveness of the proposed fault diagnosis algorithm.

A Solid-State Circuit Breaker Without Current Limiting Inductor

This paper presents a high-density, high-efficiency megawatt (MW) medium-voltage (MV) solid-state circuit breaker (SSCB) for aviation hybrid electric propulsion applications. The proposed SSCB is based on the mature silicon (Si) insulated gate bipolar transistor (IGBT) devices. With reduced IGBT gate voltage, the proposed SSCB can limit the peak fault current without the fault current limiting inductor. Thus, the specific power density of the SSCB is substantially improved compared with the traditional design. This method has negligible impact on SSCB efficiency, reliability and energy absorbed by the metal-oxide varistor (MOV), while providing additional mechanical layout freedom for power density and insulation enhancement. The potential design challenges due to the extremely high ramp rate of the system fault current and the corresponding solutions are also discussed. The performance of the proposed SSCB is validated with experimental results.

Transmission Line Protection Using Decaying DC Information in Fault Current

Today use of fast and reliable transmission line protection is of importance. This paper presents two protection techniques for transmission lines using information obtained from the decaying DC component of fault current and the pre-fault voltage signal. The fault direction is obtained using the polarities of pre-fault voltage and decaying DC of fault current. Internal faults in the transmission lines are detected with exchange of information on the decaying DC currents at both ends. The protection decisions are derived within a quarter cycle with a signal sampling rate of 4 kHz. Upon testing on a 400 kV simulated transmission system for different fault types, resistances, inception angles, and field data from a 400 kV line, the proposed techniques are found to be accurate.

An Online Metric Learning-Based Open-Switch and Current Sensor Fault Diagnosis for MSPMSM Systems

Rapid and accurate removal of faulty sectors is the conventional fault tolerance method for highly secure multi-sector permanent magnet synchronous motors (MSPMSMs). In this paper, a new fault diagnosis method for MSPMSMs based on metric learning (ML) is proposed. Its advantage is that it can complete fault detection and faulty sector location within 0.1 current fundamental cycle, which is faster than previous methods. Meanwhile, for the faulty sector, 28 types of open switch faults and current sensor faults can be accurately identified. In addition, since the fault diagnosis is based on structural characteristics, the proposed method is independent of system parameters and naturally robust to the speed and current variation. Particularly, using the consistent structural characteristics of MSPMSM sectors, an amplitude-trend distance (ATD) is presented to obviously reflect the difference of the same phase currents between healthy and faulty sectors. Subsequently, to ensure the speed of fault detection and high false alarm immunity, the ATD value under different fault states is theoretically analyzed, and a reasonable threshold is set. Compared to traditional ML methods, which requires complex computational classification methods, four characteristic parameters sector, polar, close to zero (CTZ), and sensor flag (SF) are developed to locate the faulty sector and the faulty switch or current sensor. The experiment results on four-sector PMSM verify the effectiveness of the proposed fault diagnosis method.

Fault Diagnosis of High-Speed Railway Turnout System Based on Improved Group Decision-Making

Turnout system is very important in the safety of railway system. However, the traditional maintenance method of turnouts is mainly based on human experience and basic intelligent model. Aiming at the problems existing in the current intelligent fault diagnosis method of turnout equipment, this paper uses the improved group decision-making method to dynamically and iteratively adjust and optimize the authority of each decision-making expert in the group decision-making method, so as to improve the prediction ability of the existing model, reduce the number of cases of prediction errors and further improve the safety of the turnout system.

Design of a Fractional Order Low-pass Filter Using a Differential Voltage Current Conveyor

In this paper, an active implementation of a differential voltage current conveyor (DVCC) based on a low-pass filter operating in the fractional order domain is presented. The transfer function for a fractional order system is dependent on the rational approximation of sα. Different methods used for calculating the rational approximation, including Carlson, Elkhazalil, and curve fitting, are evaluated here. Finally, to validate the theoretical results, a fractional order Butterworth filter is simulated in the Pspice environment using the 0.5 micrometer CMOS technology with an R-C network-based fractional order capacitor. Additionally, using the Monte Carlo analysis, the impact of current and voltage faults on DVCC response is investigated. It has been inferred that realization with a wider bandwidth is possible.

Transient thermal models of induction machines under Inter‐turn short‐circuit fault conditions

AbstractInduction machines are the working horses in a lot of industries. Inter‐turn short‐circuit (ITSC) fault is one of the most common failure modes taking place in them. It can generate large fault currents that lead to a local temperature rise in the faulty stator slot, which deteriorates the working performance of the machine or even cascades to a complete machine breakdown. This article focuses on developing transient thermal models for an induction machine under ITSC faults. The aim of these thermal models is to understand the thermal behaviour of the induction machine at different ITSC fault propagation stages. The first thermal model is based on finite element method (FEM) simulation that includes a physics‐based model for the thermal contact resistance. The second thermal model is a lumped parameter thermal network that models the stator as inter‐connected slot‐number parts. They are both capable of modelling the characteristic of non‐uniform temperature along the circumferential direction for the induction machine operating under ITSC fault conditions. After area‐weighted averaging the results of the FEM simulation, it is found they are quantitatively consistent, with an average relative error magnitude of 5%, as well.

A fuzzy-based fault section identification method using dynamic partial tree in distribution systems

In a distribution management system (DMS), fault section identification (FSI) is an essential function for the self-healing capability of smart distribution networks. Conventional FSI methods based on the flag of fault indicators (FIs) cannot be properly utilized for distribution networks with distributed energy resources (DERs) since false FIs, unintentionally activated by fault currents flowing from the downstream of a fault location due to the presence of wye-delta transformers for the DER interconnection, are expected to be generated. For more accurate FSI, this paper proposes a fuzzy-based FSI method using the fault current information measured on feeder remote terminal units (FRTUs) installed at automatic switches in distribution lines (DLs). The proposed method takes advantage of the fuzzy evaluation to provide an intuitive index for decision-making by quantifying the possibility of fault for each candidate section. Furthermore, to achieve faster FSI by reducing waiting time for FSI, the partial trees using only validated FIs with fault current information for the faulty DL are dynamically generated, thereby enabling the fault section can be identified regardless of whether the fault current information from every FRTU is available or not. Case studies on IEEE 33-bus distribution system considering various fault conditions are conducted and simulation results show that the proposed method can accurately identify correct fault sections under false FI and communication failure situations with the improved time required for the FSI.

A label information vector generative zero-shot model for the diagnosis of compound faults

Diagnosis of compound faults remains a challenge owing to the coupling of fault characteristics and the exponential increment of the number of possible fault types. Current compound faults diagnostic methods often require a large number of training data for each type of compound fault. In real-world scenarios, training data of compound faults are usually difficult to acquire and sometimes even inaccessible. In contrast, single fault samples are much easier to obtain. Thus in this paper inspired by the idea of zero-shot learning, we present a novel label information vector generative zero-shot model to identify unknown compound faults, using only single fault samples as the training set. This model comprises several modules, namely label information vector (LIV) definition, feature extractor, and generative adversarial modules, respectively responsible for representing the prior knowledge of specific class labels for the single fault and compound fault, extraction of fault features, and mapping the relationship between the fault features and the fault LIVs. By adversarial training between the samples and LIVs of single faults, the model can generate compound fault features using the compound fault LIVs. Thus the unknown compound faults are identified by measuring the distance between the features extracted from the testing compound fault samples and the generated features from LIVs. The proposed method is evaluated on a self-built experimental platform. The results demonstrate that without any compound fault samples in the training set, the compound fault classification accuracy of the model reaches 78.10%.

Design, Modeling, and Analysis of IEEE Std 80 Earth Grid Design Refinement Methods Using ETAP

The design of a compliant, safe, and reliable substation earth grid is not a straightforward process; in most cases, it requires some additional measures to be taken due to various constraints that differ from environment to environment, such as soil resistivity, a high fault level, a limited surface area, construction budget, etc. The IEEE Std 80-2013 proposes various refinement methods that can be applied to address different situations. For this study, the current limiting method, current diversion method, and touch and step voltage increment method were applied using the Electrical Transient Analysis Program (ETAP). A power system was designed, where a fault current generated by the supply transformers and back-fed by the power system’s motors was exported to the earth grid. Using this fault current, various simulations were conducted to assess the performance of the earth grid. The analysis results show that the application of the current limiting method using neutral earthing resistors has a great impact on the design of the earth grid as this method significantly reduces the fault current injected into the earth grid. Furthermore, by applying the current diversion method, the amount of fault current injected into the earth grid is reduced by a fair amount, which improves the performance of the earth grid. Lastly, increasing the tolerable limits of touch and step voltages by reducing the fault clearance times significantly improves the compliance of the earth grid as the clearance time is reduced. From this study, it is therefore concluded that, by implementing the refinement methods depending on the design requirements and feasibility of the application, one can improve the compliance state of an earth grid.

An Efficient Fault Detection and Exclusion Method for Ephemeris Monitoring

The ephemeris fault needs to be detected and mitigated in the ground-based augmentation system to provide precision approach for the aircraft. In the current fault detection and exclusion (FDE) method, the double-differenced carrier phase (DDCP) observation is used as a test statistic to detect a faulty satellite caused by an ephemeris fault, taking advantage of the residual spatial gradient. However, the current FDE method cannot distinguish whether the fault comes from a reference satellite (RS) or a non-reference satellite (NRS) in DDCP. One way to address this issue is to pre-validate the RS before it can be used to form a DDCP test statistic for detecting ephemeris fault on the NRS. The RS is pre-validated using the previous ephemeris for any newly acquired and re-acquired satellite. This method is developed in detail to present the shortcomings. A more efficient FDE method using multiple hypothesis testing to detect ephemeris fault on both the RS and NRS simultaneously in real time is proposed. Moreover, to facilitate the application in integrity monitoring, the test risks and minimum detectable error are analyzed. The numerical results of the proposed FDE method show an improved performance in detecting ephemeris fault on the RS and a comparable performance on the NRS compared with the current FDE method.

A novel hybrid arc suppression device for single line-to-ground faults

Traditional passive arc suppression devices (ASDs) do not provide complete compensation for single line-to-ground (SLG) fault currents. Meanwhile, active ASDs are expensive. This study proposes a novel hybrid ASD to balance compensation and cost. The hybrid ASD consists of a passive part and an active part. To reduce the fault voltage to near zero, the passive part uses a single-phase isolating transformer and two sets of phase-selection switches. The active part, which compensates for the residual voltage caused by the transformer's leakage impedance, is connected to the secondary side of the transformer and the ground using a small-capacity inverter. A model predictive control (MPC) method is employed as the controller. We conducted simulations and experiments for various SLG fault cases, which demonstrated the effectiveness and robustness of the hybrid ASD in arc suppression. The hybrid ASD that we propose is independent of the neutral point and has several advantages, including low cost, strong arc suppression capabilities, and high robustness.

An Adaptive Centralized Protection and Relay Coordination Algorithm for Microgrid

To meet the increased customer demands, microgrid evolved. The structure of microgrid changes dynamically due to the intermittent nature of renewable-based generation, status of the distributed generator and opening of breakers for fault/maintenance. Hence, the magnitude of fault current is dynamic in nature. In order to deal with these dynamic changes, this paper addresses an adaptive central microgrid controller-based protection and relay coordination scheme, which revises the relay settings dynamically (both radial and looped configuration) for every change in topology. In the proposed algorithm, the primary relay responds to a fault immediately since the individual relays are given with fault level setting. For any abnormality in the network, the fault location is determined both via local relay and microgrid central controller (MCC). Hence, even though the local relay fails to identify the fault due to high fault impedance, the MCC locates the fault accurately and isolates the minimum faulty part. The coordination between relays is carried out by MCC in a time-graded manner based on microgrid central protection and relay coordination algorithm. The proposed algorithm is tested using Matlab in a microgrid built based on the IEEE 33 bus distribution network.

Selection of TCC Curve and Protection Cooperation Method of Distribution Line Using Linear Optimization

Distribution systems are mostly composed of radial structures, which are susceptible to an increased variability and complexity of system operation due to frequent line changes during operation. When multiple changes in distribution lines occur simultaneously, the relative positions of protective devices also change. The existing protection coordination method of distribution lines is configured by considering the operation characteristics and coordination time interval (CTI) of all protective devices in series from the substation to the terminal load. Therefore, the protection coordination algorithm needs to be redesigned whenever a line is changed or a protective device is added to the distribution line for which the existing protection coordination algorithm has been set. In addition, existing protection coordination methods require complex calculations and procedures, which are subject to human errors and are less feasible for responding in real-time to changes in the distribution system. In this paper, we propose the adaptive time–current curve (TCC) method by selecting the time dial setting (TDS) and minimum response time (MRT) of individual protective devices in accordance with the relative distance based on the linear optimization technique. Using PSCAD/EMTDC, a power system analysis program, the minimum operating current and the fault current of each protective device are obtained, and the proposed protection coordination algorithm is verified according to the series configuration relationship of the protective devices. Finally, the proposed method is applied to an actual distribution line to verify the improvement over the existing protection coordination.

Virtual Armature Resistance-Based Control for Fault Current Limiting in a High-Order VSG and the Impact on Its Transient Stability

This article proposes a fault ride through (FRT) technique for a high-order virtual synchronous generator (VSG) that adjusts its virtual armature resistance. When a fault is detected by a dedicated algorithm, the proposed control adjusts the resistance parameter accordingly. The main contribution of this article is to adjust the virtual resistance directly in the machine model to limit the current during faults, unlike other techniques proposed in the literature that add another control loop to produce the virtual impedance effects. To validate the effectiveness of the proposed control, a hardware-in-the-loop real-time simulation platform was adopted using a Typhoon HIL 402 device and a Texas Instruments F28379D digital controller. The results demonstrate that the control effectively limits the converter’s current while still contributing to raising the system’s critical clearing time (CCT) and improving transient stability. The proposed FRT strategy is validated in a three-phase fault scenario in which a 500 kVA–480 V converter’s peak fault current is reduced from 5 kA to 1.4 kA, depending on the resistance value adjusted. The transient stability is also analyzed in 30 different scenarios and the VSG support on the CCT is reduced by 23 ms on average. However, when compared to the baseline scenario without the VSG, the system still sees an increase in CCT with the current limiting control applied. Additionally, the control allows the VSG to smoothly transition to island mode in a scenario where the fault is cleared and the grid is disconnected by a protection system.

Single-ended protection method for hybrid HVDC transmission line based on transient voltage characteristic frequency band

Hybrid high-voltage direct current (HVDC) transmission has the characteristic of long transmission distance, complex corridor environment, and rapid fault evolution of direct current (DC) lines. As high fault current can easily cause irreversible damage to power devices, rapid and reliable line protection and isolation are necessary to improve the security and reliability of hybrid HVDC transmission system. To address such requirement, this paper proposes a single-ended protection method based on transient voltage frequency band characteristics. First, the frequency characteristics of the smoothing reactor, DC filter, and DC line are analyzed, and the characteristic frequency band is defined. A fault criterion is then constructed based on the voltage characteristic frequency band energy, and faulty pole selection is performed according to the fault voltage characteristic frequency band energy ratio. The proposed protection method is verified by simulation, and the results show that it can rapidly and reliably identify internal and external faults, accurately select faulty poles without data communication synchronization, and has good fault-resistance and anti-interference performance.

Radial Power Distribution System Fault Classification Model Based on ANFIS

The classification of problems in power systems plays an extremely important part and has evolved into a necessity that is of the utmost importance to the operation of energy grids. For the purpose of fault classification in IEEE 13 node radial distribution systems, this paper makes use of both an Artificial Neural Network (ANN) and a Neural Fuzzy adaptive Inference System (ANFIS). Simulations of the suggested models are carried out in MATLAB/SIMULINK, and fault currents from all three phases are analyzed in order to extract statistical characteristics. Input data vectors include the standard deviation and correlation factors between the currents of any two phases, while output data vectors include the different sorts of faults. The findings demonstrate that the devised method is appropriate for the classification of all symmetrical and unsymmetrical faults.

Trends in Locally Balanced Energy Systems without the Use of Fossil Fuels: A Review

In recent years, the idea of the operation of energy systems (power systems, heating systems) has changed significantly. This paper is an overview of locally balanced energy systems without the use of fossil fuels. The paper justifies the concept of local energy balancing in a new energy system that does not use fossil fuels (coal, natural gas, and crude oil), based on European Union guidelines and formal documents as well as the literature on the subject. In this context, the issue of local energy self-sufficiency, utilizing renewable energy sources, as well as the concept of local smart grids based on innovative market mechanisms are raised. Attention is also paid to technical issues with regard to locally balanced energy systems, in particular photovoltaic sources and energy storage. Challenges related to the use of electrical protection in networks with many sources of energy are described. In such networks, the power flow is not in one direction only. Moreover, the selection of protections is problematic due to the distribution of short-circuit currents. Additionally, earth fault currents in such networks may be distorted, and this negatively affects the operation of residual current devices. The basic nomenclature describing locally balanced systems has been sorted out as well. Finally, possible future research paths in the field of creating locally balanced systems without the use of fossil fuels are presented.

Enhancing low‐priority traffic reconfiguration designs in mixed‐critical avionics networks

AbstractIn avionics system networking, mixed‐critical networks are commonly used to integrate system applications with different levels of guarantees for various traffic classes on a shared resource platform, effectively addressing issues such as cabling, cost, weight, volume, power consumption, etc. However, current fault recovery and reconfiguration techniques mainly focus on high‐priority time‐triggered (TT) traffic, often neglecting the impact of TT traffic reconfiguration on low‐priority traffic. This paper proposes an avionics mixed‐critical networking approach based on the IEEE 802.1CB protocol, which is shown to be more effective for the post‐failure recovery of Rate‐Constrained (RC) traffic (a typical type of low‐priority traffic in TT networks). Furthermore, an elastic reconfiguration algorithm is presented to ensure quality of service for RC traffic during and after reconfiguration, preventing arbitrary application and traffic shutdown triggered by TT traffic reconfiguration. Simulations demonstrate that the proposed approach and algorithm can significantly improve the post‐failure recovery ratio of RC traffic, as well as guarantee quality of service and network throughput of RC traffic during and after reconfiguration to a certain extent.

Advanced Fault Tolerant 3×3-Phase PM Drive With Concentric Winding for EV Application

Fault tolerant machine drive is essential for EV application to ensure uninterrupted operation during fault event. Among various fault modes, inter-turn fault is the most challenging failure for the PM drive which requires special measures to suppress the excessive fault current. In this paper, a novel concentric winding (CW) is analyzed for a 3×3-phase PM drive to restrict the turn fault current. Compared with the conventional distributed winding (DW), the two sub-coils of each phase occupy the same space angle and both align with the phase axis, and the winding factor of each coil is 0.96 which is 4% lower than the DW. Owing to the two aspects, the coil flux linkages are more effectively nullified after applying winding terminal short circuit (TSC) which indicates lower fault current. The two machines’ healthy performance as well as various fault modes’ behaviors are investigated by detailed simulation and test investigation. The results prove the CW machine has the same healthy characteristics as the DW machine, and the maximum inter-turn fault current is up to 17% lower than the counterpart. In addition, the improved turn fault current suppression capability is achieved simply by re-arranging the coil layout without introducing any extra cost.