Showing papers on "Fault model published in 2014"

A Traveling-Wave-Based Methodology for Wide-Area Fault Location in Multiterminal DC Systems

Abstract: While in many applications, multiterminal dc (MTDC) systems are potentially appropriate substitutes for their ac counterparts, their protection problems still require more attention. This paper proposes a novel traveling-wave-based methodology for fault location in MTDC systems. The traveling-wave principle, along with two graph theory-based lemmas, is deployed to locate the fault by sectionalizing the graph representation of the MTDC system. Accordingly, the system of equations relating the fault inception time, fault point, and first arrival time at different converter locations would be derived and solved. The method merely needs the first surge arrival times, thereby eliminating the practical problems in relation to identifying subsequent traveling waves. More important, it successfully determines the fault location, regardless of the network topology complexity, that is, the number of its meshes and radial lines. To demonstrate the effectiveness of the method, it is applied to some complicated MTDC systems containing meshes and radial lines. Numerous simulation studies carried out for different conditions verify high accuracy, robustness against fault impedance, and noise immunity of the proposed method.

Impedance-Based Fault Location in Transmission Networks: Theory and Application

Abstract: A number of impedance-based fault location algorithms have been developed for estimating the distance to faults in a transmission network. Each algorithm has specific input data requirements and makes certain assumptions that may or may not hold true in a particular fault location scenario. Without a detailed understanding of the principle of each fault-locating method, choosing the most suitable fault location algorithm can be a challenging task. This paper, therefore, presents the theory of one-ended (simple reactance, Takagi, modified Takagi, Eriksson, and Novosel et al. ) and two-ended (synchronized, unsynchronized, and current-only) impedance-based fault location algorithms and demonstrates their application in locating real-world faults. The theory details the formulation and input data requirement of each fault-locating algorithm and evaluates the sensitivity of each to the following error sources: 1) load; 2) remote infeed; 3) fault resistance; 4) mutual coupling; 5) inaccurate line impedances; 6) DC offset and CT saturation; 7) three-terminal lines; and 8) tapped radial lines. From the theoretical analysis and field data testing, the following criteria are recommended for choosing the most suitable fault-locating algorithm: 1) data availability and 2) fault location application scenario. Another objective of this paper is to assess what additional information can be gleaned from waveforms recorded by intelligent electronic devices (IEDs) during a fault. Actual fault event data captured in utility networks is exploited to gain valuable feedback about the transmission network upstream from the IED device, and estimate the value of fault resistance.

Automatic and Fast Faulted Line-Section Location Method for Distribution Systems Based on Fault Indicators

Abstract: Fault indicating devices such as fault indicators (FIs) have been widely used in distribution systems to improve reliability and reduce outage duration. Recently, FIs with communication interfaces are integrated into distribution automation (DA) to further reduce fault-finding time by reporting FIs' statuses back to control center. When faults occur, a lot of alarms and fault information are received from Outage Management System (OMS), Trouble Call System (TCS) and Customer Information System (CIS) and are shown to system operators. As a result, the identification of faulted line sections in a wide-ranging distribution system from FIs' statuses is not an easy task, especially when multiple faults occur simultaneously and/or distributed generators (DGs) are connected. An automatic and fast faulted line-section location method for distribution systems based on FIs is proposed in this paper. The line sections between adjacent FIs can be treated as a possible fault location (PFL) and the fault current detected by the FI can be considered as line current (LC) flowing between the adjacent PFLs. A relationship matrix between PFLs and LCs is then derived and used to design the proposed automatic and fast faulted line-section location method. The faulted line sections can then be located effectively and efficiently by the proposed method. Test results for an actual distribution system demonstrate the validity of the proposed faulted line-section location method.

Development and Analysis of Interturn Short Fault Model of PMSMs With Series and Parallel Winding Connections

Abstract: In this study, interturn short fault models of permanent magnet synchronous motors (PMSMs) employing series and parallel winding connections are developed using deformed flux models based on both fault winding flux information and inductance variations caused by cross flux linkages that depend on the distribution of same phase windings. As these models take into account fault winding within a three-phase winding dynamics analysis, they constitute fourth-order assessments. In the parallel-winding model, an additional dynamical analysis is used to describe variations in current distribution caused by the parallel connection between fault and healthy windings. Based on deformed flux modeling and positive sequence current assumptions, the proposed model is derived in both positive and negative sequence synchronous reference frames. A finite-element method-based simulation is applied to validate the proposed PMSM model.

Formal verification of a software countermeasure against instruction skip attacks

Abstract: Fault attacks against embedded circuits enabled to define many new attack paths against secure circuits. Every attack path relies on a specific fault model which defines the type of faults that the attacker can perform. On embedded processors, a fault model consisting in an assembly instruction skip can be very useful for an attacker and has been obtained by using several fault injection means. To avoid this threat, some countermeasure schemes which rely on temporal redundancy have been proposed. Nevertheless, double fault injection in a long enough time interval is practical and can bypass those countermeasure schemes. Some fine-grained countermeasure schemes have also been proposed for specific instructions. However, to the best of our knowledge, no approach that enables to secure a generic assembly program in order to make it fault-tolerant to instruction skip attacks has been formally proven yet. In this paper, we provide a fault-tolerant replacement sequence for almost all the instructions of the Thumb-2 instruction set and provide a formal verification for this fault tolerance. This simple transformation enables to add a reasonably good security level to an embedded program and makes practical fault injection attacks much harder to achieve.

An overview of transmission line protection by artificial neural network: fault detection, fault classification, fault location, and fault direction discrimination

Abstract: Contemporary power systems are associated with serious issues of faults on high voltage transmission lines. Instant isolation of fault is necessary to maintain the system stability. Protective relay utilizes current and voltage signals to detect, classify, and locate the fault in transmission line. A trip signal will be sent by the relay to a circuit breaker with the purpose of disconnecting the faulted line from the rest of the system in case of a disturbance for maintaining the stability of the remaining healthy system. This paper focuses on the studies of fault detection, fault classification, fault location, fault phase selection, and fault direction discrimination by using artificial neural networks approach. Artificial neural networks are valuable for power system applications as they can be trained with offline data. Efforts have been made in this study to incorporate and review approximately all important techniques and philosophies of transmission line protection reported in the literature till June 2014. This comprehensive and exhaustive survey will reduce the difficulty of new researchers to evaluate different ANN based techniques with a set of references of all concerned contributions.

How much can off-fault deformation contribute to the slip rate discrepancy within the eastern California shear zone?

Abstract: >Kinematic assumptions of geodetic inversions for fault slip require that the slip sums to the (plate) boundary velocity. This assumption neglects permanent off-fault deformation, which could account for discrepancies between geologic and geodetic estimates. We use three-dimensional mechanical models to assess if unaccounted permanent strain surrounding faults could contribute to slip rate discrepancies across disconnected faults within the Mojave Desert (California, USA) portion of the eastern California shear zone (ECSZ). We modified fault configurations derived from the Southern California Earthquake Center Community Fault Model to better represent the disconnected nature of active faults in the ECSZ south of the Garlock fault. The models with revised fault geometry produce slip rates that better match geologic strike-slip rates, thus validating the revisions. Within these models, off-fault deformation accounts for 40% ± 23% of the total strain across the ECSZ. This suggests that a significant portion of the discrepancy between the geologic and geodetically modeled slip rates in the ECSZ could be due to the geodetic inversion model assumption of zero permanent off-fault deformation.

Model-Based Health Monitoring for a Vehicle Steering System With Multiple Faults of Unknown Types

Abstract: This paper presents a model-based fault diagnosis and prognosis scheme for a vehicle steering system The steering system is modeled as a hybrid system with continuous dynamics and discrete modes using the hybrid bond graph tool Multiple faults of different types, ie, abrupt fault, incipient fault, and intermittent fault, are considered using the concept of Augmented Global Analytical Redundancy Relations (AGARRs) A fault discriminator is constructed to distinguish the type of faults once they are detected After that, a fault identification scheme is proposed to estimate the magnitude of abrupt faults, the characteristic of intermittent faults, and the degradation behavior of incipient faults The fault identification is realized by using a new adaptive hybrid differential evolution (AHDE) algorithm with less control parameters Based on the identified degradation behavior of incipient faults, prognosis is carried out to predict the remaining useful life of faulty components The proposed algorithm is verified experimentally on the steering system of a CyCab electric vehicle

Differential Fault Analysis on the families of SIMON and SPECK ciphers.

Abstract: In 2013, the US National Security Agency proposed two new families of lightweight block ciphers: SIMON and SPECK. Currently, linear and differential cryptanalytic results for SIMON are available in the literature but no fault attacks have been reported so far on these two cipher families. In this paper, we show that these families of ciphers are vulnerable to differential fault attacks. Specifically, we demonstrate two fault attacks on SIMON and one fault attack on SPECK. The first attack on SIMON assumes a bit-flip fault model and recovers the n-bit last round key of SIMON using n/2 bit faults. The second attack on SIMON uses a more practical, random byte fault model and requires n/8 faults on average to retrieve the last round key. The attack presented on SPECK also assumes a bit-flip fault model and recovers the n-bit last round key of SPECK using n/3 bit faults on average.

Bond Graph Approach for Plant Fault Detection and Isolation: Application to Intelligent Autonomous Vehicle

Abstract: The present paper deals with bond graph model-based for structural component fault detection and isolation. The structural conditions of fault detectability and isolability are obtained directly from the bond graph using the properties of the bicausality and the causal path. It is shown that the monitorability analysis using bond graph is automatically deduced using this unified tool, with respect to the detectability and isolability conditions. A real mechatronic system application of intelligent autonomous vehicle is given to show the efficiency and the simplicity analysis of the proposed approach. This paper was motivated by the problem of integrated design of a fault diagnosis system by considering both, system instrumentation and the set of specifications regarding faults. Existing methods dealing with such problems are based mainly on the existing system instrumentation. In this paper, a fault diagnosis system study and analysis is proposed. This is done by using a unified graphical tool such as Bond Graph tool which is used for system modeling, structural analysis and fault diagnosis conclusions. Therefore, system modeling, fault monitorability analysis, and fault indicator generation are all performed by using the same graphical tool. In addition, the proposed method may be exploited for monitorability analysis before industrial design, i.e., ability to detect and isolate faults with given instrumentation architecture and how to make faulty components monitorable by adding new sensors. To show the effectiveness of the proposed method, an application on real mechatronic system is considered.

Combination of Model-based Observer and Support Vector Machines for Fault Detection of Wind Turbines

Abstract: Support vector machines and a Kalman-like observer are used for fault detection and isolation in a variable speed horizontal-axis wind turbine composed of three blades and a full converter. The support vector approach is data-based and is therefore robust to process knowledge. It is based on structural risk minimization which enhances generalization even with small training data set and it allows for process nonlinearity by using flexible kernels. In this work, a radial basis function is used as the kernel. Different parts of the process are investigated including actuators and sensors faults. With duplicated sensors, sensor faults in blade pitch positions, generator and rotor speeds can be detected. Faults of type stuck measurements can be detected in 2 sampling periods. The detection time of offset/scaled measurements depends on the severity of the fault and on the process dynamics when the fault occurs. The converter torque actuator fault can be detected within 2 sampling periods. Faults in the actuators of the pitch systems represents a higher difficulty for fault detection which is due to the fact that such faults only affect the transitory state (which is very fast) but not the final stationary state. Therefore, two methods are considered and compared for fault detection and isolation of this fault: support vector machines and a Kalman-like observer. Advantages and disadvantages of each method are discussed. On one hand, support vector machines training of transitory states would require a big amount of data in different situations, but the fault detection and isolation results are robust to variations in the input/operating point. On the other hand, the observer is model-based, and therefore does not require training, and it allows identification of the fault level, which is interesting for fault reconfiguration. But the observability of the system is ensured under specific conditions, related to the dynamics of the inputs and outputs. The whole fault detection and isolation scheme is evaluated using a wind turbine benchmark with a real sequence of wind speed.

Differential Fault Analysis on the Families of SIMON and SPECK Ciphers

Abstract: In 2013, the US National Security Agency proposed two new families of lightweight block ciphers: SIMON and SPECK. Currently, linear and differential cryptanalytic results for SIMON are available in the literature but no fault attacks have been reported so far on these two cipher families. In this paper, we show that these families of ciphers are vulnerable to differential fault attacks. Specifically, we demonstrate two fault attacks on SIMON and one fault attack on SPECK. The first attack on SIMON assumes a bit-flip fault model and recovers the n-bit last round key of SIMON using n/2 bit faults. The second attack on SIMON uses a more practical, random byte fault model and requires n/8 faults on average to retrieve the last round key. The attack presented on SPECK also assumes a bit-flip fault model and recovers the n-bit last round key of SPECK using n/3 bit faults on average.

Complex Field Fault Modeling-Based Optimal Frequency Selection in Linear Analog Circuit Fault Diagnosis

Abstract: Owing to the lack of feasible fault modeling method, hard (open and short) faults, and discretized parametric faults are still the mostly used fault models. These models cannot characterize all soft (parameter shifting) faults because that the parameter of analog element be of continuity character. To address this concern, a complex field fault modeling method is presented first. If fault happens to passive element xi in linear analog circuit, the real (Ur) and imaginary (Uj) parts of faulty voltage phasor U°(U°=Ur+j Uj) must satisfy binary quadratic function Fi(Ur,Uj)=0, which is independent from the value of element xi and uniquely determined by its location and the nominal circuit under test. Hence, the binary quadratic function can model any continuous parameter shifting (soft) or hard fault. Second, to avoid calculating the explicit expression of binary quadratic function, a simulation-based method is given to obtain the locus of the change in the function Fz in the complex plane. Besides, the nominal (fault-free) point, the loci determined by the binary quadratic functions might intersect with each other. It is referred to as aliasing problem in this paper. This problem can be solved by adjusting the frequency of the input signal. Therefore, a constraint optimization method is proposed to select optimal test frequencies. The proposed test generation and compression methods, when combined with the complex field modeling method, can pinpoint much more fault components with less test points and frequencies when compared with the other methods.

Evidence of a larger EM-induced fault model

Abstract: Electromagnetic waves have been recently pointed out as a medium for fault injection within circuits featuring cryptographic modules. Indeed, it has been experimentally demonstrated by A. Dehbaoui et al. [3] that an electromagnetic pulse, produced with a high voltage pulse generator and a probe similar to that used to perform EM analyses, was susceptible to create faults exploitable from a cryptanalysis viewpoint. An analysis of the induced faults [4] revealed that they originated from timing constraint violations.

Fault location on branched networks using a multiended approach

Abstract: Existing travelling-wave fault-location methods are known to perform poorly on branched networks. In this paper, a new fault-location method for use on highly branched networks is demonstrated. The method is based on the retrieval of global positioning system time-stamped arrival times of the fault-induced high-frequency transient. It is shown that for an unambiguous estimation of the fault location, a time-stamp is required from a fault recorder located in each of the two directions from the fault position; therefore, complete coverage of a network can be achieved with a fault recorder on each branch termination. The system is also capable of locating the origin of incipient faults and, therefore, provides a means of detecting potential future faults so remedial action can be taken.

Sensitivity of Coulomb stress change to the parameters of the Coulomb failure model: A case study using the 2008 Mw 7.9 Wenchuan earthquake

Abstract: The Coulomb stress change has been widely employed to interpret mainshock-mainshock and mainshock-aftershock triggering as well as interactions amongst earthquake faults and volcanoes. This quantitative index is computed based on the Coulomb failure criterion and is a function of fault parameters including the source and receiver fault geometries, the friction coefficient on the receiver fault, and Skempton's coefficient of the host rock. Thus, for the robust determination of the Coulomb stress change, the sensitivity of the Coulomb stress change to these model parameters should be thoroughly assessed. However, notwithstanding numerous case studies, almost no systematic investigation of the sensitivity of the Coulomb stress change has been performed. Here we present an error estimator for the Coulomb stress change and then quantitatively investigate the sensitivity of the Coulomb stress change to the fault model parameters for the 2008 Mw 7.9 Wenchuan earthquake. Our results indicate that for this case the Coulomb stress change is the most sensitive to the uncertainty in the dip angle of the receiver fault, while the influences of the uncertainties in the slip model of the source fault, the strike, and rake angles of the receiver fault, and the friction and Skempton's coefficients cannot be neglected. Accordingly, it is crucial to perform a realistic estimate of the uncertainty in the Coulomb stress change. By performing such calculation, future Coulomb stress analyses such as the stress triggering of earthquake sequence and the likelihoods of potential earthquakes could be based on more robust Coulomb stress change maps.

Lazart: A Symbolic Approach for Evaluation the Robustness of Secured Codes against Control Flow Injections

Abstract: In the domain of smart cards, secured devices must be protected against high level attack potential [1]. According to norms such as the Common Criteria [2], the vulnerability analysis must cover the current state-of-the-art in term of attacks. Nowadays, a very classical type of attack is fault injection, conducted by means of laser based techniques. We propose a global approach, called Lazart, to evaluate code robustness against fault injections targeting control flow modifications. The originality of Lazart is two folds. First, we encompass the evaluation process as a whole: starting from a fault model, we produce (or establish the absence of) attacks, taking into consideration software countermeasures. Furthermore, according to the near state-of-the-art, our methodology takes into account multiple transient fault injections and their combinatory. The proposed approach is supported by an effective tool suite based on the LLVM format [3] and the KLEE symbolic test generator [4].

Sensitivity of uplift patterns to dip of the San Andreas fault in the Coachella Valley, California

Abstract: Three-dimensional mechanical simulations of the San Andreas fault system within the Coachella Valley in southern California produce deformation that matches geologic observations and demonstrate the first-order impact of fault geometry on uplift patterns. To date, most models that include the Coachella Valley segment of the San Andreas fault have assumed a vertical orientation for this fault, but recent studies of seismicity and geodetically observed strain suggest that this segment of the fault may dip 60°–70° to the northeast. We compare models with varied geometry along this segment of the fault and evaluate how well they reproduce observed uplift patterns in the Mecca Hills and Coachella Valley. Incorporating well-constrained fault geometry in regional models will provide a more accurate understanding of active faulting in southern California, which is critical for rupture and hazard modeling that is used to identify regions most susceptible to earthquake damage. We have tested three boundary-element method models for the active geometry of the Coachella Valley segment of the San Andreas fault: one contains a vertical Coachella segment, the second contains a northeast ∼65° dipping Coachella segment, and the final alternative contains a vertical Coachella segment plus a subparallel northeast-dipping fault at depth. This final model honors the geometric interpretation of seismicity from the Southern California Earthquake Center Community Fault Model version 4.0. The models containing vertical Coachella Valley segments both produce uplift between the San Andreas and San Jacinto faults that is more uniformly distributed than geologic observations suggest, and these models fail to produce uplift in the Mecca Hills. The dipping model produces tilting of the Coachella Valley consistent with geologic observations of tilting between the San Jacinto and San Andreas faults. The dipping model also produces relative subsidence southwest of the fault and localized uplift in the Mecca Hills that better match the geologic observations. These results suggest that the active Coachella Valley segment of the San Andreas fault dips 60°–70° to the northeast.

Complete Model-Based Equivalence Class Testing for the ETCS Ceiling Speed Monitor

Abstract: In this paper we present a new test model written in SysML and an associated blackbox test suite for the Ceiling Speed Monitor (CSM) of the European Train Control System (ETCS) The model is publicly available and intended to serve as a novel benchmark for investigating new testing theories and comparing the capabilities of model-based test automation tools The CSM application inputs velocity values from a domain which could not be completely enumerated for test purposes with reasonable effort We therefore apply a novel method for equivalence class testing that – despite the conceptually infinite cardinality of the input domains – is capable to produce finite test suites that are complete (ie sound and exhaustive) for a given fault model In this paper, an overview of the model and the equivalence class testing strategy is given, and tool-based evaluation results are presented For the technical details we refer to the published model and a technical report that is also available on the same website

Using Surface Creep Rate to Infer Fraction Locked for Sections of the San Andreas Fault System in Northern California from Alignment Array and GPS Data

Abstract: Surface creep rate, observed along five branches of the dextral San Andreas fault system in northern California, varies considerably from one section to the next, indicating that so too may the depth at which the faults are locked. We model locking on 29 fault sections using each section’s mean long‐term creep rate and the consensus values of fault width and geologic slip rate. Surface creep rate observations from 111 short‐range alignment and trilateration arrays and 48 near‐fault, Global Positioning System station pairs are used to estimate depth of creep, assuming an elastic half‐space model and adjusting depth of creep iteratively by trial and error to match the creep observations along fault sections. Fault sections are delineated either by geometric discontinuities between them or by distinctly different creeping behaviors. We remove transient rate changes associated with five large ( M ≥5.5) regional earthquakes. Estimates of fraction locked, the ratio of moment accumulation rate to loading rate, on each section of the fault system provide a uniform means to inform source parameters relevant to seismic‐hazard assessment. From its mean creep rates, we infer the main branch (the San Andreas fault) ranges from only 20%±10% locked on its central creeping section to 99%–100% on the north coast. From mean accumulation rates, we infer that four urban faults appear to have accumulated enough seismic moment to produce major earthquakes: the northern Calaveras ( M 6.8), Hayward ( M 6.8), Rodgers Creek ( M 7.1), and Green Valley ( M 7.1). The latter three faults are nearing or past their mean recurrence interval. Online Material: High‐resolution fault system map, and tables of creep observations and geographic coordinates of fault model.

Systems and methods for event detection and diagnosis

Abstract: Detection of event conditions in an industrial plant includes receiving process data corresponding to one or more sensors, estimating normal statistics from the process data, estimating abnormal statistics from the process data with potential!)' abnormal operation of the one or more components, determining a fault model from the estimated normal and abnormal statistics, the fault model including a learning matrix, one or more fault indices indicating a likelihood of an occurrence of one or more fault events, and a fault threshold corresponding to the one or more sensors, determining one or more further fault indices from the further process data: applying the fault threshold to the one or more further fault indices, and indicating a further occurrence of the one or more fault events when a magnitude of the one or more further fault indices exceeds the fault threshold corresponding to the one or more sensors.

The scale‐dependent slip pattern for a uniform fault model obeying the rate‐ and state‐dependent friction law

Abstract: A uniform antiplane fault model obeying the rate- and state-dependent friction law and surrounded by a steady-slipping region with a constant loading rate is studied through quasi-dynamic numerical method. Findings indicate that the model exhibits scale-dependent slip characteristics. Previous studies have demonstrated that the fault slip pattern changes from aseismic creep or slow earthquakes to seismic instabilities as the fault length W increases from around the nucleation size hc to well above hc. In the latter, instabilities typically nucleate periodically from the center of the fault and develop into characteristic events after the whole fault reaches a background stress level. For a fault with larger W/hc, characteristic events nucleate near the boundary or alternatively from both sides before the entire fault returns to background level. As W/hc increases further, additional events with rupture size between hc and W appear. The number of small events is expected to increase with W/hc. The reason these small events do not rupture the whole fault is that the locked region forming on the fault when nucleation occurs acts as a large and low stress barrier. These small events continually create stress concentrations that serve as preparations for the next larger earthquake until the final characteristic event occurs. Meanwhile, the fault in this process gradually evolves into extreme sensitivity that any slight perturbation could change the original slip pattern. Although the current result is far from explaining the observed slip complexity on natural faults, it suggests a trend of increasing slip complexity with W/hc. Therefore, our understanding of the fault behavior may differ from previous knowledge that a relatively uniform and isolated fault model obeying the rate- and state-dependent friction law only exhibits periodic or aperiodic system-size events.

Aircraft posture robust inversion fault tolerant control method based on neural network observer

Abstract: The invention discloses an aircraft posture robust inversion fault tolerant control method based on a neural network observer. Firstly, a posture dynamic equation of a near space aircraft X-33 is given, and a control surface fault model is built; the adaptive neural network observer is designed according to the control surface fault model of a posture angular rate loop, and a posture angle loop and a designed observer dynamic equation are combined; by the adoption of an instruction filtering inversion method, an angle ring controller and an angular speed ring controller are designed. According to the aircraft posture robust inversion fault tolerant control method based on the neural network observer, precise fault information and interference information are not needed and are respectively hidden in the designed adaptive neural network observer, the hidden information is fed back to the controllers in real time, and robust fault tolerant control is achieved; the problem that robustness and sensibility are needed by FDI is solved, and robust fault tolerant control is achieved; finally, the method is applied to stability control and tracking control over the near space aircraft under control surface fault situations, robust fault tolerant control over the flying posture is achieved, and good control performance and a good control effect are achieved.