Broken Fault Research Articles

Economic Implementation of 99.98% Efficiency in Natural-Cooling Modular MVDC SSCBs

This paper presents a modular medium voltage direct-current (MVDC) solid-state circuit breaker (SSCB) with high efficiency. The presented design method is modularity oriented, which includes thermal analysis of conduction cell, busbar design of conduction disk, and structure design of conduction tower. The implementation includes both continuous current conduction and fault current interruption. This paper includes three major contributions. First, it presents an economic analysis in terms of efficiency and cost as the design guideline for the main conduction configuration of SSCBs. Second, it provides a complete modular SSCB design procedure, showing both parallel and cascade scalability. Third, this paper investigates the effect of main conduction path stray resistances on SSCB efficiency and power loss. A medium-voltage SSCB prototype rated at 4kV/100A are experimentally implemented. The power density achieves 26.2 kW/L. The continuous conduction tests are conducted at 100A for 1hour, the steady-state efficiency achieves 99.98% with maximum temperature of 37°C. The fault interruption tests are successfully conducted at 4 kV/ 137A and 4 kV/ 1 kA with different system inertia.

Investigation of Impulse Aging of Energy-Absorption Elements for Hybrid DC Circuit Breakers

The state of the energy-absorption branch MOV in the hybrid DC circuit breaker (DCCB) has a very important impact on the short fault breaking operation of the circuit breaker. Therefore, it is necessary to evaluate the state of the MOV, which is also called the “sleep component”. Due to DCCB being placed indoors, the aging is mainly caused by short-circuit impulse current. Therefore, this paper mainly focuses on the study of the short-circuit impulse aging characteristics of the energy-absorption branch MOV. The dynamic simulation system of a hybrid DCCB was built to investigate the impulse of short-circuit current on the MOV of the energy-absorption branch during the circuit breaking process. Then, an accelerated impulse aging test platform was built and the accelerated impulse aging tests of the MOV were conducted. The aging characteristics of the MOV were analyzed in detail and detailed analysis was conducted of the macroscopic parameters and microstructure changes. The results indicate that the nonlinear coefficient α could be emphasized as a basis for judging the “sleeping” component states and aging degree of the hybrid DC circuit breaker, and can be expected to be applicable to MOV condition monitoring of BCCB in the future.

Electromagnetic disturbance characteristic of typical high voltage switchgear interruption process in offshore wind farm based on integrated conduction model

AbstractIn an offshore wind farm, a high‐voltage switchgear interruption in an offshore substation creates a high‐frequency, high‐amplitude overvoltage that can cause severe electromagnetic interference problems in the intelligent electronic device. To address this issue, mathematical models, vector fitting and finite element method were used to build an integrated electromagnetic disturbance conduction model, whose accuracy was verified by large current interruption tests. Through the simulation of a typical offshore wind farm's single‐phase grounding fault interruption process, the electromagnetic disturbance characteristics and the impact of the ground position are obtained. The results show that during the fault interruption process of phase B grounded, the dominant frequency of disturbance voltage can reach 4.34 MHz, and the amplitude can reach 1.12 kV. The ground grid has a large impact on the interference voltage, which can reach a maximum value of 2.28 kV under specific conditions. The disturbance voltage in the fault process mainly comes through the current transformer, while during the interruption process, it mainly comes through the ground grid. The authors provide a method to establish the integrated electromagnetic disturbance simulation model, which can improve the accuracy of the electromagnetic disturbance conduction process simulation of intelligent components.

Global symmetry breaking and topological defects

In this article, we present the fundamentals of Goldstone's theorem and the breaking of global symmetries. As well as one of the important aspects to take into account in the process of spontaneous symmetry breaking are the possible topological defects generated by the breaking. For this reason, we will expose the concept of topological defect and the calculation of the relic density of the axion, considered as a candidate to dark matter.

Analysis and experimental validation of bidirectional modified O-Z source fault interrupter for the protection of DC microgrid

Analysis and experimental validation of bidirectional modified O-Z source fault interrupter for the protection of DC microgrid

PCB Rogowski Coil sensor by using Saw blade pattern for arcing fault detection

Rogowski is a special current transformer and has been categorised as a low-power stand-alone current sensor. This sensor is designed by using a Saw blade pattern with 50 turns and 100 turns. This number of turns will impact the increment of the sensitivity of the sensor. Rogowski coil is used for measuring the alternating current (AC) and high-speed current pulses. The PCB Rogowski Coil will detect the arcing fault that design with AutoCAD software after that import to CST software. An arc is created when the electrical current jumps the gap between two conductive materials. The most common causes of arcs include worn contacts in electrical equipment, damage to insulation, break in a cable and loose connections. In order to reduce the arc fault risk, the arc fault interrupter (AFI) technology and arc fault detectors (AFD) have been developed. However, these devices are most suitable for domestic application or low voltage (LV). This paper proposed a simulation using AutoCAD and CST software to design a Rogowski coil and the Rogowski Coil sensor will be tested by using CST software in terms of radiation pattern. The biggest radiation pattern in red colour is the saw blade pattern in 100 turns at 2 KHz frequency, the radiation pattern covering entire sensor area compared with other radiation patterns with other frequency. The main lobe magnitude for 2 KHz frequency is 46.8 dB, main lobe direction is 180 deg, angular width is 153.4 deg and the side lobe level is zero. This is the best number of turn and frequency compared to 50 turn saw blade sensor.

Zero-sequence current suppression control for fault current damper based on model predictive control

In a multi-terminal direct current (MTdc) system based on a modular multilevel converter (MMC), high-speed and large interruption capability direct current circuit breakers (dc CBs) are required for dc fault interruption. However, commercializing these breakers is challenging, especially offshore, due to the large footprint of the surge arrester. Hence, a supplementary control is required to limit the rate of current rise along with the fault current limiter. Furthermore, the operation of the dc CB is not frequent. Thus, it can lead to delays in fault interruption. This study proposes the indirect model predictive control (MPC)-based zero-sequence current control. This control provides dc fault current suppression by continuously controlling the zero-sequence current component using circulating current suppression control (CCSC) and by providing feedback to the outer voltage loop and inner current loop of MMCs. The proposed control is simulated for pole-to-pole and pole-to-ground faults at the critical fault location of an MTdc system. The simulation is performed in Real Time Digital Simulator (RTDS) environment, which shows that the predictive control reduces the rate of rise of the fault current, providing an additional 3 ms after the dc fault occurrence to the dc CB to clear the fault. Besides, the energy absorbed by the dc CB’s surge arrester during the pole-to-pole and pole-to-ground fault remains the same with the proposed control.

A Fast Protection Relay for MMC-Based DC Grids Robust to Cyber-Physical Anomalies

Half-bridge modular multilevel converters (HBMMCs) are widely applied in modern DC grids, where converter substations have a cyber-physical structure similar to that of a typical intelligent substation. One major issue for HBMMCs is the lack of sufficient fault interruption capability. Hence, a reliable protection relay is necessary. However, conventional relays need a very robust cyber-physical system, and unintended events are not rare in intelligent substations. In this paper, several types of cyber-physical anomalies and their impacts on protection relays are first analyzed. Then, a novel protection relay is proposed based on the difference between the theoretical and the calculated modal measurements. To eliminate inter-substation asynchronization, the Bhattacharyya distance is introduced to quantify the above graphic feature in a sliding time window with high robustness to noise contamination; also, historical data is employed to identify and erase upcoming abnormal samples in real time. Case studies validate the robustness against external faults, power order change, and cyber-physical anomalies. Additionally, the proposed protection relay is highly sensitive to internal faults. Discussions are also conducted to investigate the quantitative capability against abnormal samples, to determine the scope of applications for different DC lines and to compare the proposed protection relay with several state-of-the-art methods.

Relief Morphometry of Nayaseri Watershed: A Case Study in Northern Slopes of Shimla, Himachal Pradesh, India

The study of relief elements is very significant in geography. Relief set the stage for all types of development of cultural features on the surface of the earth. To make planning regarding development of cultural landscape, for sustainable development, the study of relief is must, particularly in mountainous regions. The study of relief enlighten many characteristics of the area, like - slope, dissection of area, stability and instability of topography, erosion capacity of area, hydrological aspects and stages of sequential development of landforms etc. In the light of this need, relief morphometry of catchment has been studied. To study the Morphometry of the watershed, parameters like – relative relief, absolute relief, dissection index, slope, hypsometric integral curve, clinographic curve, relief ratio and ruggedness number, relief profile have been taken. The topographical map published by Government of India is the database of the analysis. Instruments, like- Rotameter and Planimeter have been used for various measurements. The observations per square kilometer are taken to calculate the areal coverage of absolute and relative relief, average slope and dissection index. The study reveals that the watershed has experienced tectonic incidences in the recent past. Fault, submergence, upliftment, tilt and sudden breaks of slopes are imprints of these activities on topography of the area. Indicators like - Slope, relief ratio, ruggedness number and relief profiles suggest that the watershed has Steep slopes, unstable landmass and capacity of intense erosion. Various measures of relief also imply that the area is in the youthful phase of its sequential development.

Recent Research Advances in Double-Strand Break and Mismatch Repair Defects in Prostate Cancer and Potential Clinical Applications

Prostate cancer remains a leading cause of cancer-related death in men worldwide. Recent research advances have emphasized the critical roles of mismatch repair (MMR) and double-strand break (DSB) in prostate cancer development and progression. Here, we provide a comprehensive review of the molecular mechanisms underlying DSB and MMR defects in prostate cancer, as well as their clinical implications. Furthermore, we discuss the promising therapeutic potential of immune checkpoint inhibitors and PARP inhibitors in targeting these defects, particularly in the context of personalized medicine and further perspectives. Recent clinical trials have demonstrated the efficacy of these novel treatments, including Food and Drugs Association (FDA) drug approvals, offering hope for improved patient outcomes. Overall, this review emphasizes the importance of understanding the interplay between MMR and DSB defects in prostate cancer to develop innovative and effective therapeutic strategies for patients.

Simulation Analysis of Tooth Break Faults of Gear Transmission System based on Electromagnetic Torque Signal

The traditional gear fault simulation model focuses on the vibration signal. However, the vibration sensor is not easy to install, and the vibration signal is easily affected by the installation location and environment of the vibration sensor. The motor itself has the characteristic of sensor. But in the traditional integrated model of motor and gear, the gear model is established based on the dynamical equation of the gear. However, the gear transmission established by the dynamics of the gear can’t fully reflect the running state of the gear. Moreover, the more complex the gear transmission system, the more complex and inaccurate the dynamical equation will be. Based on the above situation, in this paper, the virtual prototype model of the two-stage gear transmission system with broken tooth fault in different parts of the gear is established in Adams, which is imported into Matlab and co-simulated with the motor control model built in Matlab. Then the electromagnetic torque signal is analyzed. The results show that different characteristic frequencies of gear faults can be detected in the electromagnetic torque signal. The virtual prototype model of gear transmission system can accurately reflect the motion state of gear, and the fault of the complex gear transmission system can be simulated.

Analysis of Transient Recovery Voltage of 500 kV Line Considering Current Limiting Reactor

To limit the short-circuit current level, the method of series current, the limiting reactor is used to limit the short-circuit current, and the common access mode of the current limiting reactor is direct access. The series current limiting reactor can effectively limit the short-circuit current in 500kV power system, but after it is connected to the system, it will increase the transient recovery voltage steepness in case of a circuit breaker breaking fault and affect the normal breaking of the circuit breaker. Based on a 500 kV current limiter project, the influence of a lower limit current reactor on the recovery voltage of circuit breaker under different fault conditions is studied by using electromagnetic transient simulation software EMTP. The results show that the transient recovery voltage of the circuit breaker will exceed the standard value after the reactor is connected. When capacitors above 600nF are connected in parallel to the current limiting reactor, the transient recovery voltage could be limited to the standard range.

Circuit Breaker Fault Diagnosis Method Based on Coil Current Time Sequence Phase Trajectory Characteristics

The traditional circuit breaker fault diagnosis method suffers from insufficient feature information extraction and is easily affected by abnormal signal acquisition. To address this, this paper introduces the phase space reconstruction algorithm to reconstruct the current signal for fault diagnosis based on phase trajectory features. The proposed method uses a first-order forward differencing method and mutual information method to process abnormal data and select the parameters of the reconstruction, then extract overall and local inflection point features to construct a fault feature set. The support vector machine algorithm-based model is trained and tested using actual samples, and the results show that the proposed method can adaptively sample anomalous signals, exhibit strong robustness, and significantly improve the accuracy of fault classification.

Application of Statistical Quality Control Methods to Sarong Product Quality at UD. Utomo Joyo

UD. Utomo Joyo has problems related to monthly production defects, where the company has a maximum defect target of 5% of total production for one period, but the defects that occur exceed estimates. This study aims to find solutions to improve the application of the Statistical Quality Control method to the quality of sarong products at UD. Utomo Joyo using Seven Quality Control Tools (7 QC), namely flowcharts, checksheets, histograms, control charts, pareto diagrams, scatter diagrams, and fishbone diagrams. The results of the analysis and discussion show that there are 2 types of product defects such as yarn break defects and color fade/flex defects, while the most common or dominant defect is yarn break defects with a percentage of 68.3%. The findings of these defective products are still within the control limits of UCL and LCL. The proposed improvements are rescheduling to check tools regularly, providing adequate and safe lighting facilities for eye health, providing SOP education to workers before starting work. The advice given is to provide more focus on the most common or dominant product defects, in order to reduce losses and increase customer satisfaction in the future.

Analysis of Voltage Characteristics for Single-Phase Line Break Fault in Resonant Grounding Systems

With the rapid transition of overhead lines to covered conductors, line break fault occurs more frequently in resonant grounding systems. Line break fault, especially with earthing, requires comprehensive study. There are significant advantages for the detection of line break fault using steady-state voltage characteristics on both sides of the fault point. In this paper, a model is built for different types of single-phase line break fault in resonant grounding systems. Based on the fundamental analysis of single-phase line break fault without earthing, the single-phase line break fault with earthing at system/load side is also comprehensively studied. The neutral voltages are derived from the proposed model. The magnitudes, angles, and phase sequences of the three-phase voltages and line-to-line voltages are mathematically derived for both upstream and downstream of the fault point. The difference between single-phase line break fault and single-phase-to-earth fault is identified. The analysis is verified in the simulations. Built upon the analysis in this paper, the detection and location approaches for line break fault in resonant grounding systems can be further studied.

A fault-based probabilistic seismic hazard model for Lebanon, controlling parameters and hazard levels

The present work develops a comprehensive probabilistic seismic hazard study for Lebanon, a country prone to a high seismic hazard since it is located along the Levant fault system. The historical seismicity has documented devastating earthquakes which have struck this area. Contrarily, the instrumental period is typical of a low-to-moderate seismicity region. The source model built is made of a smoothed seismicity earthquake forecast based on the Lebanese instrumental catalog, combined with a fault model including major and best-characterized faults in the area. Earthquake frequencies on faults are inferred from geological as well as geodetic slip rates. Uncertainties at every step are tracked and a sensitivity study is led to identify which parameters and decisions most influence hazard estimates. The results demonstrate that the choice of the recurrence model, exponential or characteristic, impacts the most the hazard, followed by the uncertainty on the slip rate, on the maximum magnitude that may break faults, and on the minimum magnitude applied to faults. At return periods larger than or equal to 475 years, the hazard in Lebanon is fully controlled by the sources on faults, and the off-fault model has a negligible contribution. We establish a source model logic tree populated with the key parameters, and combine this logic tree with three ground-motion models (GMMs) potentially adapted to the Levant region. A specific study is led in Beirut, located on the hanging-wall of the Mount Lebanon fault to understand where the contributions come from in terms of magnitudes, distances and sources. Running hazard calculations based on the logic tree, distributions of hazard estimates are obtained for selected sites, as well as seismic hazard maps at the scale of the country. Considering the PGA at 475 years of return period, mean hazard values found are larger than 0.3 g for sites within a distance of 20–30 km from the main strand of the Levant Fault, as well as in the coastal region in-between Saida and Tripoli (≥ 0.4 g considering the 84th percentile). The study provides detailed information on the hazard levels to expect in Lebanon, with the associated uncertainties, constituting a solid basis that may help taking decisions in the perspective of future updates of the Lebanese building code.

Probabilistic impact assessment of lightning strikes on power systems incorporating lightning protection design and asset condition

Lightning strikes may result in widespread power outages with long supply interruption times and severe impacts to economy and society. To prevent this from happening now and in the future, power system planning and operation practices must be revisited so that the probability of outages caused by lightning strikes can be reduced. In this context, this article presents a probabilistic framework for impact assessment of lightning strikes on the grid which investigates power system exposure to lightning strikes. This new framework incorporates information about failure rates attributed to lightning protection system design and asset condition together with the probability of lightning activity over time for a probabilistic impact assessment of lightning strikes on the grid. Notably, the probability of lightning activity is conditioned by information about weather patterns and seasons obtained through collaboration with the Met Office. Furthermore, it is demonstrated in the reduced 29-bus Great Britain transmission system model with weather data collected from 2010 to 2019 and validated against historical fault data recordings provided by the National Grid’s Transmission System Performance Reports and by the National Fault Interruption Reporting Scheme. Therefore, the framework is envisaged to assist power system planners to investigate best design and maintenance practices and grid modernization interventions and power system operators to deploy smart operational measures that reduce the probability of power outages caused by lightning strikes.

Multi-port DC circuit breaker based on dual capacitor current limiting and energy sink

The coupling relationship between the removal of the fault current and the dissipation of the residual energy of the fault line during the fault isolation process of the multi-port capacitive current-limiting DC circuit breaker prolongs the breaking time of the fault to a certain extent. In order to solve the above problems, this paper proposes a multi-port DC circuit breaker based on dual-capacitor current limiting and energy sinking on the premise of decoupling the fault current attenuation and removal process and the fault line residual energy discharge process. Further reduce the fault breaking time and equipment withstand voltage requirements of the DC circuit breaker. Firstly, the topology and working principle of the proposed circuit breaker are analyzed, and then the parameters in the topology are designed. Then a simulation model is built in the PSCAD/EMTDC simulation platform to verify the fault breaking performance and breaking time. The effect of decoupling the fault current clearing process and the fault line residual energy discharge process on the effectiveness of shortening the fault breaking time is verified.

Numerical Study of Rayleigh Wave Interaction with Rolling Contact Fatigue Type of Defects

ABSTRACT Rolling Contact Fatigue or Damage (RCF/RCD) presents significant maintenance challenges to railroads across the globe. Quantifying RCF/RCD crack depths and density in rails is important for all railroads to manage their grinding programs effectively and efficiently and being able to conduct ultrasonic testing (UT) of rails for reliable detection of internal fatigue damage. This work focuses on the modeling of Rayleigh waves UT approach to detect and characterize RCF type of defects which can form as: vertical, oblique or branched shaped surface breaking defects in the rail head. Specifically, the transmission coefficient (Tc) of Rayleigh waves was studied using finite element analysis (FEA). The effect of crack tip geometry on Tc values is discussed. The results suggest that for oblique, and branch cracks, characterization based purely on the Tc can be challenging due to symmetric sinusoidal fluctuations in the Tc. A real crack using a micrograph image was also modeled to validate the Tc results for oblique and branched cracks. This points to the need for additional parameters to be identified for efficient and reliable characterization of RCF/RCD type of defects in rails.

Vibration Signal Augmentation Method for Fault Diagnosis of Low-Voltage Circuit Breaker Based on W-CGAN

Low-voltage circuit breaker (LVCB) fault diagnosis based on artificial intelligence (AI) algorithm has always been a research hotspot and got some recent advances. However, AI algorithms usually require sufficient data to train the model, so intelligent fault diagnosis is a challenging task when lack of fault signals. To solve this problem, a fault vibration signal augmentation method based on Wasserstein distance (WD) and conditional generative adversarial networks (CGANs) is proposed in this article. The proposed method uses WD to optimize the adversarial training of generator and discriminator, and thus, the generator can generate vibration signals under different fault conditions, which can be used to extend the training dataset. In order to verify the improvement effect of this method on the accuracy of LVCB fault diagnosis, multiple fault classifiers are trained using generated and real fault signals, and a multidimensional evaluation index system is built to evaluate the classification effect. Experimental results reveal that the method can generate fault signals with high similarity and improve the accuracy of fault diagnosis.