Analysis Of Fault Characteristics Research Articles

Study on the Characteristics of Turn-to-Turn Short Circuit Faults in the Primary Windings of the Generator Terminal Voltage Transformer

Turn-to-turn short circuit faults in the primary winding of generator terminal voltage transformers can lead to erroneous operation of stator grounding protection systems. This paper analyzes the fault characteristics associated with such failures and derives formulas for the fault phase current and zero-sequence voltage during a turn-to-turn short circuit in the primary winding. A 3D finite element model of the generator terminal voltage transformer is established by using Altair Flux 3D, and the accuracy of the model is verified. Based on this model, simulation tests were conducted to investigate turn-to-turn short circuits in the primary winding. The results reveal that as the number of shorted turns increases, the voltage of the fault phase decreases continuously while the voltages of the other two phases increase. The current in the short-circuited phase rises significantly, accompanied by an increase in zero-sequence voltage. Visualizations of magnetic field parameters indicate that as the number of shorted turns increases, the magnetic induction magnitude of the fault phase rises steadily and approaches saturation, resulting in heightened magnetic field intensity near the shorted turns. This analysis of fault characteristics through simulation contributes to the advancement of fault diagnosis systems for generator terminal voltage transformers.

Fault characteristics and protection methods for long distribution lines with grid-forming IBDG integration

Grid-forming inverter-based distributed generation (IBDG) is an effective means to address low voltage issues at the end of long distribution lines in remote areas. However, existing distribution protection methods are not suitable for this scenario. By analyzing the voltage phase angles of grid-forming IBDG that meet low voltage remediation requirements, the boundary phase angle conditions corresponding to ”minimum line loss” and ”minimum inverter current” are derived. Based on this, the distribution characteristics of short-circuit currents in long distribution networks are analyzed, and the limitations of traditional three-stage current protection methods are revealed through a regional discussion.An adaptive current protection method is proposed, which automatically adjusts protection device parameters by real-time calculation of regional intersection positions and currents. The effectiveness of this method is verified through simulations. The simulation results confirm the accuracy of the proposed boundary conditions and fault characteristic analysis, demonstrating that the proposed adaptive current protection method can effectively address short-circuit scenarios in long distribution networks with grid-forming IBDG integration.

A lightweight MMC topology with recombined half‐bridge submodules for DC fault ride‐through

AbstractThe lightweight of modular multilevel converter (MMC) and the DC faults ride‐through ability are main challenges for MMC‐high voltage direct current (HVDC) transmission systems. By introducing the concept of time‐division multiplexing, an arm multiplexing MMC (AM‐MMC) topology with high utilization of submodules is presented to reduce the weight and volume of MMC. In order to block the DC side fault current, this paper proposes a novel submodule in AM‐MMC, instead of using full‐bridge submodules. The proposed recombined half‐bridge submodules of AM‐MMC (RHAM‐MMC) contains four half‐bridge submodules and an IGBT with reverse parallel diodes. The topology and operating principle of RHAM‐MMC are introduced in detail. The time‐division multiplexing of middle arms between upper and lower arms is achieved by introducing arm selection switches. Thus, a new type of arm switch and switching method is designed based on the switch state. The DC faults ride‐through strategy is carried out based on its DC fault characteristic analysis. In addition, the economy analysis is conducted on the switching loss and operating loss of RHAM‐MMC. Compared with the fault ride‐through capability of other sub‐modules (SMs), RHAM‐MMC performs better in terms of investment cost and device losses. The simulation results based on MATLAB/Simulink reveal that RHAM‐MMC can achieve the DC side fault ride‐through and show effectiveness of the DC fault ride‐through control strategy.

Study on phase-locked out-of-step fault characteristic analysis and protection of VSPSU

Abstract The variable-speed pumped storage unit (VSPSU) adopts flexible three-phase AC excitation, and the control dominant characteristics of the equipment are significant, which deeply affects the out-of-step (OOS) fault law and stability mechanism of VSPSU. Aiming at the OOS fault of VSPSU, this paper first defines the power angle of VSPSU and analyzes the influence of a phase-locked loop on the power angle stability of the unit. Then, the fault characteristics of the power angle instability of VSPSU are further studied. It is found that the traditional lens impedance protection scheme based on measuring the number of sliding poles has the problem that the phase-locked OOS oscillation cannot be responded to or the response is not timely. Combined with the research on the fault characteristics of power angle instability of VSPSU, an OOS protection method based on a bilateral annular blocker is proposed. The simulation results show that the proposed protection method can quickly and accurately reflect the phase-locked OOS fault of VSPSU, and meet the requirements of VSPSU for the reliability of OOS protection.

Fault Characterization for AC/DC Distribution Networks Considering the Control Strategy of Photovoltaic and Energy Storage Battery

In order to cope with the failure of existing fault analysis schemes for AC/DC distribution networks with a high proportion of distributed generations, this paper proposes a fault characteristic analysis method for AC/DC distribution networks that considers the influence of distributed generation control strategies. Firstly, a transient model for the AC/DC distribution network connected to distributed generations is built. Then, the fault characteristics of the AC/DC distribution network in different stages, such as the capacitor discharge stage, inductive renewal stage, and steady state stage, is analyzed. Finally, detailed simulation analysis is conducted using PSCAD/EMTDC to validate the effectiveness of the developed scheme by the superior approximation performance between simulated curves and calculated curves.

Loose Coupling Mechanism and Fault Characteristics Analysis of Multiple Connections in Full Ceramic Bearing-Pedestal-Foundation System Within Wide Temperature Ranges

Loose Coupling Mechanism and Fault Characteristics Analysis of Multiple Connections in Full Ceramic Bearing-Pedestal-Foundation System Within Wide Temperature Ranges

Compound Fault Characteristic Analysis for Fault Diagnosis of a Planetary Gear Train

The carrier eccentricity error and gear compound faults are most likely to occur simultaneously in an actual planetary gear train (PGT). Various faults and errors are coupled with each other to generate a complex dynamic response, which makes the diagnosis of PGT faults difficult in practice. In order to analyze the joint effect of the error and the compound faults in a PGT, a carrier eccentricity error model is proposed and incorporated into the TVMS model by considering the time-varying center distance, line of action (LOA), meshing angle, and contact ratio. Then, the TVMS of the cracked gear is derived based on the potential energy method. On this basis, the dynamic model of a PGT with both the carrier eccentricity error and compound gear cracks as internal excitations are established. Furthermore, the meshing characteristics and dynamic responses of the PGT are simulated to investigate the compound fault features. A series of experiments are conducted to further analyze the influence of the compound fault on the vibration response. The relevant conclusions can provide a reference for the compound fault diagnosis of a PGT in practice.

Characteristic Investigation and Overvoltage Suppression of MMC-HVDC Integrated Offshore Wind Farms Under Onshore Valve-Side SPG Fault

The valve-side ground fault in the converter station of modular multilevel converter based high voltage direct current (MMC-HVDC) is a serious threat to the security of power systems. Hence, this paper analyzes the most common single-phase-to-ground (SPG) fault characteristics of valve-side faults in onshore converter stations of MMC-HVDC integrated offshore wind farms. The propagation and impact mechanism of onshore SPG fault to offshore HVDC transmission lines, offshore converter station, and wind farms are deduced based on the MMC control principle. Furthermore, an overvoltage suppression strategy based on zero-sequence voltage modulation is proposed. The effect mechanism of this strategy on the transient stability of the system is analyzed. The key parameter of the proposed strategy is also designed considering both the practical engineering requirements and the impact of the system operation. Finally, the theoretical analysis of fault characteristics and the proposed overvoltage suppression strategy are verified by the PSCAD/EMTDC simulation platform. Simulation results not only show good agreement with the theoretical analysis of the fault characteristics, but also prove the effectiveness of the proposed overvoltage suppression strategy.

Analysis of Peak Ground Acceleration and Seismogenic Fault Characteristics of the Mw7.8 Earthquake in Turkey

A Mw7.8 earthquake struck Turkey on 6 February 2023, causing severe casualties and economic losses. This paper investigates the characteristics of strong ground motion and seismogenic fault of the earthquake. We collected and processed the strong ground motion records of 379 stations using Matlab, SeismoSignal, and Surfer software: Matlab (Version R2016a), SeismoSignal (Version 5.1.0), and Surfer (Version 23.0.15), and obtained the peak ground acceleration (PGA) contour map. We analyzed the near-fault effect, the fault locking segment effect, and the trampoline effect of the earthquake based on the spatial distribution of PGA, the fault geometry, and slip distribution. We found that the earthquake generated a very strong ground motion concentration effect in the near-fault area, with the maximum PGA exceeding 2000 cm/s2. However, the presence of fault locking segments influenced the spatial distribution of ground motion, resulting in four significant PGA high-value concentration areas at a local dislocation, a turning point, and the end of the East Anatolian Fault. We also revealed for the first time the typical manifestation of the trampoline effect in this earthquake, which was characterized by a large vertical acceleration with a positive direction significantly larger than the negative direction. This paper provides an important reference for understanding the seismogenic mechanism, damage mode, characteristics, and strong earthquake law of the Turkey earthquake.

Single-phase grounding line selection method for closed-loop distribution network adapted to medium voltage microgrid access

Aim: The access of the medium-voltage (MV) microgrid changes the radial structure of traditional distribution networks, causing the distribution network to operate in a closed-loop manner. The closed-loop operation complicates the fault characteristics of the distribution network, and the traditional single-phase grounding (SPG) line selection method is no longer applicable. Therefore, it is necessary to propose a new targeted SPG line selection method. Methods: This paper analyzes the network structure of MV microgrids and MV distribution networks and establishes a multi-level closed-loop operation distribution network model with MV microgrid access. Then, the SPG fault characteristics of the closed-loop operation distribution system under the small current grounding mode are analyzed from the perspective of two-level bus nodes. Furthermore, based on the analysis of fault characteristics, a closed-loop operation distribution network line selection method suitable for microgrid access is proposed, and a detailed design is carried out in terms of equipment configuration and communication schemes, forming a relatively complete automatic line selection system. At the same time, the proposed line selection scheme is based on the two-level bus nodes, which can be analogously applied to the multi-level closed-loop operation distribution network. Results: The simulation results show that the proposed line selection scheme can be effectively applied to the closed-loop operation distribution network with MV microgrid access. Conclusion: The traditional SPG line selection method will have misjudgment problems after the MV microgrid is integrated into the distribution network, but the line selection method proposed in this paper has good adaptability.

A Novel Protection Based on Current Correlation for DC Lines in Hybrid Cascaded Multi-Terminal HVDC Transmission System

This article proposes an innovative DC line protection utilizing current correlation coefficient for hybrid cascaded high-voltage direct-current (HVDC) system. First, the equivalent discharge circuit after DC line fault is inferred, and then fault characteristic analysis on the superimposed network reveals that for the transmission lines connecting line commutated converter (LCC) and modular multilevel converters (MMCs), high-frequency currents of faulty line and non-fault line are negatively correlated, their correlation coefficient is theoretically -1. Whereas, high-frequency currents of two non-fault lines show a strong positive correlation, their correlation coefficient equals theoretically 1. Then, cosine correlation coefficient is adopted to describe current correlations and construct the identification criterion. Simulation demonstrates that protection could differentiate the faulty line accurately. Additionally, it has high sensitivity for high-resistance fault. And it is simple and has low computational complexity, and is insensitive to the line boundary element.

A Hierarchical Maintenance Method for Power System Transmission and Substation Multi-Equipment Operation Status Considering Equipment Service Age

The current conventional maintenance methods for transmission and substation operation equipment are mainly used to extract fault data features by combining micro-network algorithms to process equipment operation data. The lack of effective analysis of equipment fault characteristics leads to poor maintenance results. In this regard, a power system transmission and substation multi-device operation status hierarchical maintenance method considering the age of equipment service is proposed. By accessing the configuration network and interacting with the grid intelligent collection of data, network storage and parallel processing of data are realized. The characteristics of transmission and substation equipment operation data are analyzed and processed to build the maintenance system. In the experiments, the proposed method is validated for the effect of condition assessment. The experimental results show that when the proposed method is used to process the transmission and substation equipment, the condition assessment accuracy is high and it has a more desirable equipment maintenance performance.

Typical Fault Characteristics Analysis of Distribution Network

China has built the largest power network in the world, forming a pattern of “nationwide interconnection, sending power from west to east, mutual supply between south and north.” As the user-oriented terminal power network, the safe operation of distribution network is the basis of power system stability. However, the distribution network system is huge, widely distributed and prone to failure. In order to quickly and accurately judge the fault category, improve the efficiency of fault location and reduce the non-fault outage area after the fault occurs in the distribution network system. Four typical faults of distribution network, namely single-phase grounding fault, phase-to-phase short circuit fault, ferromagnetic resonance and magnetizing inrush current, are studied in this paper, their fault characteristics are analyzed, and fault simulation analysis is carried out by MATLAB. Finally, the theoretical analysis results are verified by the actual on-site fault recording data, which proves the scientific and feasibility of the theoretical analysis.

Magnetic circuit decomposition model and novel inner‐turn fault protection scheme for shunt reactor with auxiliary windings

AbstractShunt reactor with auxiliary windings (SRAW) can compensate inductive reactive power for long‐distance transmission lines and supply steady power for low‐voltage devices on offshore platforms. The operation characteristics of SRAW can be commonly described by the air‐core transformer equivalent model. However, this model can only make an approximate simulation of the external characteristics of SRAW, and cannot reflect the actual electrical features inside the SRAW. To solve this problem, the authors propose a three‐segment magnetic circuit equivalent model (TMCEM) of SRAW based on the magnetic circuit decomposition method. This model can accurately describe the coupling relationship inside SRAW and can be used for the analysis of internal fault characteristics. Furthermore, through the fault analysis utilizing TMCEM, a novel protection scheme of SRAW based on virtual magnetizing differential current is proposed for the detection of the inner‐turn fault in SRAW. This protection scheme has high sensitivity and can effectively identify the inner‐turn faults without measuring voltages. By testing the physical model of SRAW, the effectiveness of the TMCEM and the proposed protection scheme against inner‐turn fault has been confirmed.

Analysis of fault characteristics and oil and gas enrichment differences in the No. 2 structural belt, Nanpu Sag, Bohai Bay Basin, East China

There are great differences in oil and gas enrichment at different locations in petroliferous basins, and faults are an important factor affecting the differential enrichment of oil and gas. In this paper, taking the No. 2 structure in the Nanpu Sag, Bohai Bay Basin, East China, as an example, based on the analysis of fault geometry and kinematics characteristics, the determination of oil source faults, the analysis of fault trap origin and effectiveness, and the analysis of fault caprock combinations are carried out to study the differences and mechanisms of oil and gas enrichment east and west of the Nanpu No. 2 structure. The results show that the fault-source contact relationship affects the direction of oil and gas migration. The No. 2 structure in the Nanpu Sag has a dual-source hydrocarbon supply. The western structure supplies hydrocarbons from the north and east, with oil and gas migrating along the direction parallel and perpendicular to the fault strike. The east structure supplies hydrocarbons from the south and north, with oil and gas migrating along the direction perpendicular to the fault strike. The effectiveness of fault traps affects the scale of oil and gas accumulation. Most of the traps of the Nanpu No. 2 structure formed before hydrocarbon expulsion, which are all effective traps and are conducive to oil and gas accumulation. The relationship between fault and caprock determines the vertical accumulation layers of oil and gas: The faulted thickness of the east structure is large, the fault is vertically closed, and oil and gas are enriched mainly in the deep layer. The faulted thickness of the west structure is small, and oil and gas are enriched in both deep and shallow layers.

Fault Characteristic Analysis and a Novel Pilot Protection Scheme for Pole-to-Ground Fault in Flexible DC Distribution Network

Fault Characteristic Analysis and a Novel Pilot Protection Scheme for Pole-to-Ground Fault in Flexible DC Distribution Network

A fuzzy set theory-based fast fault diagnosis approach for rotators of induction motors.

Induction motors have been widely used in industry, agriculture, transportation, national defense engineering, etc. Defects of the motors will not only cause the abnormal operation of production equipment but also cause the motor to run in a state of low energy efficiency before evolving into a fault shutdown. The former may lead to the suspension of the production process, while the latter may lead to additional energy loss. This paper studies a fuzzy rule-based expert system for this purpose and focuses on the analysis of many knowledge representation methods and reasoning techniques. The rotator fault of induction motors is analyzed and diagnosed by using this knowledge, and the diagnosis result is displayed. The simulation model can effectively simulate the broken rotator fault by changing the resistance value of the equivalent rotor winding. And the influence of the broken rotor bar fault on the motors is described, which provides a basis for the fault characteristics analysis. The simulation results show that the proposed method can realize fast fault diagnosis for rotators of induction motors.

Single-phase Grounding Fault Section Locating Technology for Distribution Network Based on Rough Set Algorithm

With the continuous development of distribution networks, the proportion of the power electronic equipment that accesses distribution networks is increasing, which increases the system capacitance current, making the probability of single-phase grounding fault via intermittent arc in the system significantly increased. However, most traditional locating technologies are suitable for single grounding fault type via stable resistance, and cannot locate the fault above, which seriously impairs the reliability of the power supply of distribution networks. In order to solve the problem above, this paper puts forward the single-phase grounding fault section locating technology for the distribution network based on a rough set algorithm. This technology is able to obtain the phase current signals in the system for judgment, and analyze multiple characteristics of current signals with a rough set algorithm, thus determining the fault types in the system correctly. Moreover, it is also able to determine fault sections with proper section locating algorithms based on different fault types. Furthermore, it is able to locate sections of various fault types, such as resistance fault and fault via intermittent arc, with an expanded feasible region. Besides, it only makes a judgment based on phase current without collecting the zero-sequence voltage of the system, ensuring adaptability. Additionally, it is able to supplement and optimize fault type identification categories by adding condition attributes of fault characteristic analysis in the rough set algorithm, having certain engineering application values. In the end, the feasibility of this locating technology was verified with ATP power system simulation software.

Fault Characteristics Analysis of High-Speed Train Transmission Systems

The high-speed train speed has a higher requirement for stability and operating safety with its operating speed increasing. The main focus of this paper is on the fault characteristics analysis of a high-speed train transmission system. The governing equation and boundary conditions of the transmission system are derived using the finite element method, in which a Timoshenko beam element is introduced to represent the wheelset shaft, and a rigid mass element is utilized to represent the gears, bearings, and wheels. To investigate the vibration response mechanism of a high-speed train transmission system, the critical speed of the system and its modal response are given. According to the types of high-speed train component fault features, the local fault features of gear, bearing, and wheelset are given. Healthy and faulty systems with localized faults in gear, bearing, and wheelset are studied. The characteristics of amplitude and frequency are verified numerically and the transmission characteristics of signal and relation are explained when there is local fault defect in the system. The results show that under different fault types, the time domain response of the system has obvious periodic impulse response faults, and the fault frequency band characteristic distribution is different in the frequency domain response. The simulation results are consistent with the experimental results.

Analysis of typical fault characteristics of modular multilevel converter for flexible HVDC transmission

Modular multilevel converter (MMC) has been widely used in VSC-HVDC system for its smooth output waveform, low harmonic content and low switching loss. But compared with the conventional LCC-HVDC system, modular multilevel converter has a short development history, few engineering applications, high failure rate and lacks of very effective protection strategies, which limits its further development. Therefore, this paper firstly introduces topological structure of MMC and its working principle. Then the commonly used control policy of dual-terminal MMC-HVDC project is elaborated. Finally, the transient electrical characteristics of the typical faults are detailedly analyzed through the combination of theoretical analysis and simulation, such as three phase short circuit of converter valve, single phase grounding of converter valve, and the bridge arm short circuit. The conclusion provides an essential theory for the research of the converter protection strategy in the MMC-HVDC project.