Dangerous Faults Research Articles

Natural rail fracture defect calibration using infrared thermography and edge detection

Rail breakage can cause train derailment that leads to catastrophic consequences, prevention of which is worthy of a significant amount of investment in finance and time. Non-destructive evaluation can provide qualitative and quantitative inspection of rail tracks in-situ to detect dangerous faults, even though these defects are primarily invisible or hardly noticed from the surface of the rail. To make it efficient and convenient, infrared thermography technique offers a remote operation without interfering with rail transportation. The image processing for edge detection can further quantify the defect deterioration by depicting the contour of the defect. Moreover, the optimal parameters for various edge operators provide reliable detection for natural fracture defects.

A new intelligent scheme for short-circuit detection, classification and location in power transmission lines with the PV generation presence

Transmission lines constitute critical energy infrastructure in an electrical installation, as they ensure a reliable and efficient energy transition. However, they are prone to breakdowns, due to their significant length and their continuous exposure to atmospheric conditions. In addition, the photovoltaic energy sources integration can modify their behavior, which contributes to a greater increase in the breakdowns probability. Short circuits are the most common and dangerous fault type, leading in the majority of cases to other fault types. This research describes the development of a new intelligent system that consists of three stages. The first stage aim is to identify whether there is a short circuit or not using a binary SVM. In the second stage, an innovative expert system is used to determine the short circuit type among 11 potential faults. The output of this system depends on the inputs obtained by four binary SVM, each of which determines the fault presence or absence in a phase. The third stage is responsible for estimating the exact fault position in a 100 km transmission line. This stage is made up of 11 universal regressors of type MLP. The proposed system was validated using signals, obtained from a modelled High-Voltage Line with a PV Energy Source (25 kV-50 Hz-100 Km) and processed by the Discrete Wavelet Transform. Statistical metrics (with all p-value < 0.001) validate the proposed system performance with: 100% sensitivity and specificity for the fault detector ; an average sensitivity, specificity, and false alarms of 99.38%, 99.94%, and 0.17%, respectively, for the fault discriminator ; and a 2.66% mean squared error and a 97.80% overall sensitivity for the fault location estimator. These results conclude the proposed approach reliability, demonstrating its potential effectiveness in real-world scenarios.

Behavior analysis of dual-star permanent magnet synchronous generator with inter-turn short fault

ABSTRACT The dual-star PMSMs (DSPMSM) are widely used in high-power applications due to their robustness and reliability. As they mostly work in harsh environments, they are commonly subject to many faults. One of the most dangerous faults is the inter-turn short fault (ITSF), which induces torque vibrations and overheating inside the machine, and may lead to other faults. To properly handle this issue, it must be correctly understood, and the relationship between different machine’s quantities (speed, dq currents, fault ratio and resistance) and the severity of the fault (torque’s oscillations and short-circuit current) must be established. In this context, this paper presents a detailed analysis of the DSPMSM behavior under a single ITSF, considering the influence of the mentioned quantities and the PWM converter on torque oscillations and short-circuit current. A mathematical model of the machine is developed, and a hysteresis current controller is used to impose the desired direct and quadrature axis stator currents. Simulation tests are conducted by considering different scenarios. Simulation results showed that to reduce fault severity, a trade-off between speed reduction and flux weakening must be accomplished, consequently accepting some performance degradation. Also, results showed the complex behavior of the short-circuit current, as it does not rely linearly on fault parameters.

Detection of Carbonization of Paper in Transformers Using Duval Pentagon 2 and Triangle 5

The two most dangerous faults in transformers are arcing in paper insulation and thermal carbonization of paper inside windings. Both may result in catastrophic failures of the transformers. However, these faults are very difficult to detect. Furans content and the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /CO ratio can be used, but they are often unreliable or not sensitive enough when small amounts of paper are involved. Furthermore, they cannot identify the exact location of the fault. Acoustic tests may be used for that purpose, but they are expensive and can be applied only to a small number of transformers. New inexpensive methods have been developed recently, using DGA and Duval Pentagon 1 and Triangle 1, to detect arcing in paper and differentiate it from arcing in oil. Duval Pentagon 2 and Triangle 5 have been used in the present article to detect faults C with thermal carbonization of paper and their location in transformers, i.e., in windings turns (the most dangerous) or in leads entering or exiting the windings. This offers the practical advantage of concentrating maintenance efforts of transformer operators on possible faults C with carbonization of paper in windings turns, which occur in a small number of transformers but may result in severe failures and outages.

Near-source ground motion estimation for assessing the seismic hazard of critical facilities in central Italy

We apply the Probabilistic Seismic Hazard Analysis (PSHA) and compute Physics-Based Simulations (PBS) of ground motion for three dams in the Campotosto area (Central Italy). The dams, which confine an artificial water reservoir feeding hydroelectric power plants, are located in an active seismic zone between the areas that experienced the 2009 L’Aquila and 2016–2017 Central Italy seismic sequences. The probabilistic disaggregation estimated for a return period of 2475 years, corresponding to the collapse limit state for critical facilities, indicates that the most dangerous fault is associated with a maximum magnitude of 6.75 ± 0.25 within a distance of 10 km. This fault is used in PBS to emulate the Maximum Credible Earthquake scenario. To capture the ground motion variability, we input a pseudo-dynamic source model to encompass spatial and temporal variations in the slip, rise time and rupture propagation, heavily affecting the near-source ground motion. Indeed, the ground motion above the rupture volume is mainly influenced by the epistemic uncertainties of rupture nucleation and slip distribution. The computed broadband seismograms are consistent with the near-source shaking recorded during the 2016 MW 6.6 Norcia earthquake and constrain the upper bound of the simulated ground motion at specific sites. Our modelling reinforces the importance of considering vertical ground motion near the source in seismic design. It could reach shaking values comparable to or larger than those of the horizontal components. This approach can be applied in other areas with high seismic hazard to evaluate the seismic safety of existing critical facilities.

THE IMPACT OF ROADSIDE TECHNICAL INSPECTIONS ON TRANSPORT AND LOGISTICS SYSTEMS IN THE SLOVAK REPUBLIC

Road transport safety, apart from environmental protection, is one of the most important tasks for the contemporary world. Annually, about 50 million people are injured in road accidents around the world, of which nearly 1.5 million die as a result. Transport safety consists of many activities and includes various initiatives, including legal changes, training, preventive actions, building safe road infrastructure, and the production of safe vehicles and control systems. This article deals with the issue of performing roadside technical inspections in the Slovak Republic. Specifically, it analyses the results of these roadside technical inspections in individual counties of the Slovak Republic and examines their possible impact on transport and logistics systems in these counties. The correlation analysis showed that the number of checks under the technical roadside inspections is weakly related to the number of logistics centres, but the number of such inspections is moderate in relation to the number of failed vehicles (correlation coefficient = 0.44079). In addition, due to the age of the vehicles, the number of serious and dangerous faults found on them during maintenance inspection increases.

Safety Integrity Level of Shut-Off Valve in a Burner Management System

The safety control and command system, such as the burner manage-ment system, requires that the system must be reliable, available and safe. The reliability is based on choosing equipment, with a high level of safety and which is suitable for the safety system. The availability and security are provided, among others, by redundancy. It is presented by M-Canal out of N-Canal (MooN) architecture, the (N-M) indicates how many dangerous faults are possible, with-out the performance of the systems being impeded. An essential quantitative analysis based on the evaluation of the PFDavg is part to give high trust in the BMS. This paper will discuss how a quantitative method can be used to select the appropriate SIL according to shutdown system for Burner Management System (BMS). This system is a part of a safety solution that manages a combustion sys-tem; it allows the safe start-up operation, and the shutdown of multiple burner furnace section of a boiler, and main flame detection.

Curved rock etchings reveal which way dangerous faults ruptured—and how they might again

Curved rock etchings reveal which way dangerous faults ruptured—and how they might again

Crack localization in stepped rotors based on Bayesian fusion of multiscale superharmonic characteristic deflection shapes

AbstractA crack is one of the most dangerous faults in rotors of key rotating machinery. In order to make reasonable maintenance, crack localization for rotors under operational conditions is very important and full of challenges. Focusing on crack localization in rotating rotors, a new crack localization method for stepped rotors based on Bayesian fusion of multiscale superharmonic characteristic deflection shapes (SCDSs) is proposed. The non‐linearity induced by cracks is utilized to eliminate the interference of stiffness reduction by steps in the rotor, and the noise‐robustness issue is tackled by casting the SCDSs into multiscale SCDSs with multiscale space theory. Moreover, Bayesian fusion is applied to the multiscale SCDSs to derive a new damage index to localize cracks. Numerical and experimental investigations are conducted to validate the proposed method. The results indicate that the proposed method is effective, accurate and robust for single or multiple crack localization in stepped rotors, and thus, it has a great potential in practical applications.

Evaluation of ISO 26262 and IEC 61508 metrics for transient faults of a multi-processor system-on-chip through radiation testing

Functional Safety standards for programmable electronic systems require i) the evaluation of the probability of hardware failure occurring to the electronic system due to random faults and ii) a sound estimation of the capability of the system to correct or detect the presence of dangerous faults regardless of their probability to occur. This paper presents a methodology to quantify those metrics in relation to a specific class of failures, the Single Event Effects (i.e. Transient faults in ISO 26262 terminology). The methodology is applied using accelerated radiation data measured on a System-on-Chip targeting Automotive and Industrial safety-critical applications. The results show how SPFM, PMHF, SFF, PFH metrics are being calculated. Both SPFM and SFF result to be >99% in this experiment.

Reliable Detection of Stator Interturn Faults of Very Low Severity Level in Induction Motors

The interturn faults are one of the most (if not the most) challenging electrical machine failures to detect online and at incipient severity stages. Past works and experience have shown that this specific fault type will lead to a ground fault and consequently a catastrophic failure of the machine in a very small amount of time. Past works have proposed techniques and methodologies to confront this dangerous fault. However, a common feature in most past efforts is the high level of severity, limited by external resistors to avoid machine breakdowns. Scenarios like the above are not of much use in industry because they lead to the development of diagnostic techniques insensitive to the real fault severity levels that are noncatastrophic and that are by their nature very low. This is the motivation behind this article, which challenges the existing background in this field and offers a reliable solution, which may be adopted in industry. The article studies induction motors with incipient interturn fault severity with many well-known techniques. The experimental results prove many methods unreliable and insensitive to low level interturn fault detection. Finally, the authors propose a novel method that relies on the monitoring of the stray flux at three positions of the machine.

Detection and interpretation of local surface deformation from the 2018 Hokkaido Eastern Iburi Earthquake using ALOS-2 SAR data

We identified and analyzed surface displacements associated with the 2018 Hokkaido Eastern Iburi Earthquake in northern Japan using satellite radar interferograms from the Advanced Land Observing Satellite 2. The data generally show elastic deformation caused by the main earthquake as well as numerous complex surface displacements that cannot be explained by the motion of the seismic source fault. We identified three distinct phenomena: linear surface displacements representing secondary earthquake faults west of the epicenter, surface deformation caused by liquefaction in urban and coastal areas, and coherence changes in the interferograms due to landslides in mountainous areas and liquefaction in urban areas. The linear surface displacements show reverse fault motion with low dip angles and appear to be a geographic extension of known active faults; however, it is unlikely that these displacements were directly connected to the source fault of the main earthquake. Although there is no evidence that they generated strong seismic waves at the time of the main earthquake, there is a possibility that they represent active fault traces and could be the sources of large earthquakes in the future. Therefore, such linear surface displacements can be used to identify potentially dangerous hidden active faults. The interferograms reveal that liquefaction in urban areas occurred in low areas artificially filled during past residential development. Coherence-change maps drawn from the interferograms were useful for detecting liquefaction, but their high sensitivity limited their application for landslide detection in mountainous areas; the phase noise deviation method was more practical for purposes such as rapid response or mitigation. Our methods have the potential to allow improved mapping of local hazards in other areas and can be applied to urban planning and/or safety assessments.

Coulomb Stress Evolution History as Implication on the Pattern of Strong Earthquakes along the Xianshuihe-Xiaojiang Fault System, China

Coulomb stress accumulation and releasing history and its relationship with the occurrence of strong historical earthquakes could deepen our understanding of the occurrence pattern of strong earthquakes and hence its seismic potential in future. The sinistral strike-slip Xianshuihe- Xiaojiang fault zone (XXFS) is one of the most dangerous fault zones in China, extending 1 500-km-long from the central Tibetan Plateau to the Red River fault zone. There are 35 M≥6.5 historical earthquakes occurred since 1327, hence it is an ideal site for studying the Coulomb stress evolution history and its relationship with the occurrences of strong earthquakes. In this study, we evaluated the Coulomb stress change history along the XXFS by synthesizing fault geometry, GPS data and historical earthquakes. Coulomb stress change history also revealed different patterns of historical earthquakes on different segments of the XXFS, such as characteristic recurrence intervals along the Salaha-Moxi fault and super-cycles along the Xianshuihe fault. Based on the occurrence pattern of past historical earthquakes and current Coulomb stress field obtained in this study, we suggest positive ΔCFS and hence high seismic potential along the Salaha-Moxi fault and the Anninghe fault.

Ensuring public safety through proper earthing in low-voltage networks

Electrical network should have proper earthing (grounding) system for its reliable operation and for the safety of operating personnel and connected customers. Good earthing provides a suitable return path for the fault current when a short circuit occurs in the network. In a low-voltage (LV) network mainly terra-terra (TT) and terra-neutral (TN) type network configurations are commonly used. Depending on the agreement between the network operator and the customer, earthing at a customer's point of connection (POC) is provided by a dedicated earth conductor, combined network cable (PEN conductor), or via a separate earth electrode. When an earth retour path is broken or interrupted, it will not be able to provide earth retour circuit and can cause dangerous fault voltage at various exposed parts of the conducting circuit. In this paper, various LV network configurations are discussed. Further, a practical monitoring based case study is presented to analyze the diversity of earth resistance values for different LV network configurations. Also, guiding rules are given to define safe value of circuit impedance and earth resistance path for various configurations. Finally, a proposal is given to optimize the safety needs at a customer's POC.

Alteration Along the Alpine Fault Helps Build Seismic Strain

Detailed analysis of cores drilled through New Zealand's most dangerous on-land fault indicates that its permeability and strength are altered by mineral precipitation between seismic events.

Analysis and Aesearch of White Spot on Creepage Discharge in oil-Pressboard Interface

Creepage discharges on oil impregnated pressboard is one of the most dangerous transformer insulation fault, which can cause the gas action even transformer housing cracking accident. “White spot” is creepage important phenomena in the process of insulation board along the surface, so it is necessary to study the insulation board along the surface of creepage “white spot” in the process of growth characteristics. This paper set up a insulating paper along the surface of creepage “white spot” in the process of growth characteristics of observation platform. Numerical example was calculated under different aging degree creepage cardboard along the surface of the “white spot” in the process of change, statistics and analysis of the “white spot” length, angle and size variation, which is very practical to the production practice.

Recent geodynamics of dangerous faults

The analysis of the existing information concerning the present-day deformation activity of the fault zones in seismically active and aseismic regions suggests that the notions of an active fault and a dangerous fault should be distinguished. It is shown that a fault which is active for an expert in geotectonics will not be considered dangerous by an expert in geotechnical monitoring of buildings. The definition is given according to which a dangerous fault is understood as a zone of linear destruction which accommodates the contemporary short-period (a few months and years) pulsed and/or alternating motions with strain rates above 5 × 10–5 per annum and earthquakes with M ≥ 5. A technique is developed for identifying the dangerous faults based on monitoring the recent ground surface displacements in accordance with a special protocol which ensures an increased degree of detail in time and space. Based on the idea of the probable accumulation of dangerous strains during the operating cycle of the objects, the criteria for assessing their geodynamical risks are formulated.

A Fractional Calculus Model of Viscoelastic Stator Supports Coupled With Elastic Rotor–Stator Rub

Rotating machinery is inherently susceptible to costly and dangerous faults. One such commonly encountered fault is undesirable dynamic contact between the rotor and stator (i.e., rotor–stator rub). The forces generated during rotor–stator rub are fundamentally tribological, as they are generated by contact and friction and result in wear. These forces are typically found by assuming linear elastic contact and dry Coulomb friction at the rotor–stator interface, where the normal force is a linear function of the interference. For the first time, this work incorporates viscoelasticity into the stator support and investigates its influence on the global dynamics of rotor–stator rub. The viscoelastic stator supports are modeled using fractional calculus, an approach which adeptly and robustly characterizes the viscoelasticity. Specifically, a fractional derivative order of one-half is employed to generate an analytic time-domain form of viscoelastic impedance. This approach directly assimilates viscoelasticity into the system dynamics, since the rotor equations of motion are integrated numerically in the time-domain. The coupled rotor–stator dynamic model incorporating viscoelastic supports is solved numerically to explore the influence of viscoelasticity. This model provides a framework for analysis of dynamic systems where viscoelasticity is included.

PM Synchronous Machine Drive Response to Asymmetrical Short-Circuit Faults

This paper investigates the impact of machine topology and parameters on the fault-mode characteristics of permanent-magnet synchronous machines (PMSMs) exposed to asymmetrical short-circuit (ASC) faults, one of the most dangerous faults in terms of peak current amplitudes and demagnetization risks. Simulations using an equivalent circuit model combined with finite-element (FE) analysis are used to explore the differences between the ASC fault-mode responses of three major types of PM machines. The effects of several different rotor and winding configurations have been studied to identify the key machine parameters that have a major influence on the fault current amplitudes. Results indicate that fractional-slot concentrated winding (FSCW) PM machines tend to exhibit lower peak currents compared to distributed winding (DW) machines during ASC fault events. Finally, the results from three different types of short-circuit faults are summarized and compared for several PM machine configurations to provide information that will be helpful for choosing the best machine for new applications. Experimental results are provided for constrained ASC fault conditions that build confidence in the models and their predictions.

New Formula (22/17) for Calculation of the Total Amount of Intravenous Fluids Given for Pediatric &amp; Neonatal Surgical Operations Weighing up to 20 Kg or 5 Years Age

Introduction: A new formula(RH) for calculation of intra operative fluids given in neonatal & pediatric life threatening surgical operations from 1 kg – 2o kg body weight (or 1 day – 5 yrs age) was explained in this study. Aim of the Study : To find a simple , correct, & easily applicable formula to avoid any unwanted dangerous faults in calculation of fluid requirements in all types of neonatal& pediatric surgical operations from 1 kg – 20 kg body weight (or 1 day – 5 years age) especially for juniors or early post graduated doctors dealing with these age group (or weights). Patients: (5000 Patients) including neonates, infants & pediatric age group presented to CWTH/Medical city/Baghdad for different types of surgical operations were enrolled in this study divided to 3 groups (Group A) Life threatening and emergency conditions 2300 patients, (Group B) Major& super major elective operations 700 patients & (Group C) Different types of minor to moderate elective surgical operations 2000 patients. Methods: In this new formula intra operative fluid requirements calculated as: a) *Pre existing deficit (Fasting): 20 ml/kg this amount is divided over 3 hours: ½ the amount given in the 1st hour of operation and ¼ the amount is given for each the 2nd& 3rd hours of operations. b) *Maintenance fluid requirements: 4 ml/kg/hr for all weights up to 20 kg. c) *3rd Space replacement: 8 ml/kg/hr for major& super major operations & 4 ml/kg/hr for minor operations. Results: By comparison of this new formula with most of other references and other anesthesia text books fluid formulas regarding this aspect the results is that the difference in the total amounts of fluid requirements per hour was minute and regarded as negligible difference. Conclusion: *This new(RH) formula has been used for years(2005-2015) in neonatal & pediatric anesthetic department in CWTH/ Baghdad Medical City for 5000 neonates, infants & pediatric patients without any complications. a. This new formula is correct, safer, simpler & easily applicable than other formulas. b. The most important point in this new formula, is that it can be summarized by just 2 numbers (22- 17), 22ml/kg for the 1st hr. & 17 ml for the 2nd& 3rd hrs of operation time for major operation.