Showing papers on "Fault indicator published in 2013"

Fault-Tolerant Control of Wind Turbines: A Benchmark Model

Abstract: This paper presents a test benchmark model for the evaluation of fault detection and accommodation schemes. This benchmark model deals with the wind turbine on a system level, and it includes sensor, actuator, and system faults, namely faults in the pitch system, the drive train, the generator, and the converter system. Since it is a system-level model, converter and pitch system models are simplified because these are controlled by internal controllers working at higher frequencies than the system model. The model represents a three-bladed pitch-controlled variable-speed wind turbine with a nominal power of 4.8 MW. The fault detection and isolation (FDI) problem was addressed by several teams, and five of the solutions are compared in the second part of this paper. This comparison relies on additional test data in which the faults occur in different operating conditions than in the test data used for the FDI design.

Fault Detection for Modular Multilevel Converters Based on Sliding Mode Observer

Abstract: This letter presents a fault detection method for modular multilevel converters which is capable of locating a faulty semiconductor switching device in the circuit. The proposed fault detection method is based on a sliding mode observer (SMO) and a switching model of a half-bridge, the approach taken is to conjecture the location of fault, modify the SMO accordingly and then compare the observed and measured states to verify, or otherwise, the assumption. This technique requires no additional measurement elements and can easily be implemented in a DSP or microcontroller. The operation and robustness of the fault detection technique are confirmed by simulation results for the fault condition of a semiconductor switching device appearing as an open circuit.

DC Ring-Bus Microgrid Fault Protection and Identification of Fault Location

Abstract: A fault protection and location method for a dc bus microgrid system is presented in this paper. Unlike traditional ac systems, dc bus systems cannot survive or sustain high-magnitude fault currents. And if a fault causes the dc bus to de-energize completely, it makes locating faults very difficult. The main goal of the proposed scheme is to detect and isolate faults in the dc bus without de-energizing the entire system and identifying the fault location. In order to achieve this, a ring-type bus was used in this paper. The bus was segmented into overlapping nodes and links with circuit breakers (CBs) to isolate the segment in the event of a fault. Backup protection is implemented for circuit breaker failures to improve system reliability. A noniterative fault-location technique using a probe power is also presented in this paper. This probe power can also be used for a pilot test before main CB reclosing to avoid system issues that can be expected when the reclosing fails due to a permanent fault. The proposed algorithm can be implemented and executed by an intelligent electrical device for individual node. The proposed concepts have been verified with computer simulations and hardware experiments.

Detection of High Impedance Fault in Power Distribution Systems Using Mathematical Morphology

Abstract: A high impedance fault (HIF) is characterized by a small, nonlinear, random, unstable, and widely varying fault current in a power distribution system. HIFs draw very low fault currents, and hence are not always effectively cleared by conventional overcurrent relays. Various schemes are proposed to detect such faults. This paper presents a method to detect HIFs using a tool based on mathematical morphology (MM). The method is implemented alongside the conventional overcurrent relay at the substation to improve the performance of this relay in detecting HIFs. It is rigorously tested on standard test systems using PSCAD/EMTDC® to generate test waveforms, and Matlab® to implement the method. Simulation results show that the proposed method is fast, secure, and dependable.

A Sensor Fault Detection and Isolation Method in Interior Permanent-Magnet Synchronous Motor Drives Based on an Extended Kalman Filter

Abstract: Interior permanent-magnet synchronous motors (IPMSMs) become attractive candidates in modern hybrid electric vehicles and industrial applications. Usually, to obtain good control performance, the electric drives of this kind of motor require one position, one dc link, and at least two current sensors. Failure of any of these sensors might lead to degraded system performance or even instability. As such, sensor fault resilient control becomes a very important issue in modern drive systems. This paper proposes a novel sensor fault detection and isolation algorithm based on an extended Kalman filter. It is robust to system random noise and efficient in real-time implementation. Moreover, the proposed algorithm is compact and can detect and isolate all the sensor faults for IPMSM drives. Thorough theoretical analysis is provided, and the effectiveness of the proposed approach is proven by extensive experimental results.

Fault Detection and Isolation in Low-Voltage DC-Bus Microgrid System

Abstract: A fault detection and isolation scheme for low-voltage dc-bus microgrid systems is presented in this paper. Unlike traditional ac distribution systems, protection has been challenging for dc systems. The goals of the proposed scheme are to detect the fault in the bus between devices and to isolate the faulted section so that the system keeps operating without disabling the entire system. To achieve these goals, a loop-type dc-bus-based microgrid system, which has a segment controller between connected components, is proposed. The segment controller consists of master and slave controllers that monitor currents and control the segment separation, which include solid-state bidirectional switches and snubber circuits. The proposed system can detect faults on the bus regardless of fault current amplitude or the power supply's feeding capacity. The proposed concepts have been verified by OrCAD/PSpice simulations and experiments on hardware test bed.

Open-Circuit Fault Diagnosis in PMSG Drives for Wind Turbine Applications

Abstract: Condition monitoring and fault diagnosis are currently considered crucial means to increase the reliability and availability of wind turbines and, consequently, to reduce the wind energy cost. With similar goals, direct-drive wind turbines based on permanent magnet synchronous generators (PMSGs) with full-scale power converters are an emerging and promising technology. Numerous studies show that power converters are a significant contributor to the overall failure rate of modern wind turbines. In this context, open-circuit fault diagnosis in the two power converters of a PMSG drive for wind turbine applications is addressed in this paper. A diagnostic method is proposed for each power converter, allowing real-time detection and localization of multiple open-circuit faults. The proposed methods are suitable for integration into the drive controller and triggering remedial actions. In order to prove the reliability and effectiveness of the proposed fault diagnostic methods, several simulation and experimental results are presented.

Line–Line Fault Analysis and Protection Challenges in Solar Photovoltaic Arrays

Abstract: Fault analysis in solar photovoltaic (PV) arrays is a fundamental task to protect PV modules from damage and to eliminate risks of safety hazards. This paper focuses on line–line faults in PV arrays that may be caused by short-circuit faults or double ground faults. The effect on fault current from a maximum-power-point tracking of a PV inverter is discussed and shown to, at times, prevent overcurrent protection devices (OCPDs) to operate properly. Furthermore, fault behavior of PV arrays is highly related to the fault location, fault impedance, irradiance level, and use of blocking diodes. Particularly, this paper examines the challenges to OCPD in a PV array brought by unique faults: One is a fault that occurs under low-irradiance conditions, and the other is a fault that occurs at night and evolves during “night-to-day” transition. In both circumstances, the faults might remain hidden in the PV system, no matter how irradiance changes afterward. These unique faults may subsequently lead to unexpected safety hazards, reduced system efficiency, and reduced reliability. A small-scale experimental PV system has been developed to further validate the conclusions.

On Fault Representativeness of Software Fault Injection

Abstract: The injection of software faults in software components to assess the impact of these faults on other components or on the system as a whole, allowing the evaluation of fault tolerance, is relatively new compared to decades of research on hardware fault injection. This paper presents an extensive experimental study (more than 3.8 million individual experiments in three real systems) to evaluate the representativeness of faults injected by a state-of-the-art approach (G-SWFIT). Results show that a significant share (up to 72 percent) of injected faults cannot be considered representative of residual software faults as they are consistently detected by regression tests, and that the representativeness of injected faults is affected by the fault location within the system, resulting in different distributions of representative/nonrepresentative faults across files and functions. Therefore, we propose a new approach to refine the faultload by removing faults that are not representative of residual software faults. This filtering is essential to assure meaningful results and to reduce the cost (in terms of number of faults) of software fault injection campaigns in complex software. The proposed approach is based on classification algorithms, is fully automatic, and can be used for improving fault representativeness of existing software fault injection approaches.

Electromagnetic Fault Injection: Towards a Fault Model on a 32-bit Microcontroller

Abstract: Injection of transient faults as a way to attack cryptographic implementations has been largely studied in the last decade. Several attacks that use electromagnetic fault injection against hardware or software architectures have already been presented. On micro controllers, electromagnetic fault injection has mostly been seen as a way to skip assembly instructions or subroutine calls. However, to the best of our knowledge, no precise study about the impact of an electromagnetic glitch fault injection on a micro controller has been proposed yet. The aim of this paper is twofold: providing a more in-depth study of the effects of electromagnetic glitch fault injection on a state-of-the-art micro controller and building an associated register-transfer level fault model.

Diagnostics and Prognostics Method for Analog Electronic Circuits

Abstract: Analog circuits play a vital role in ensuring the availability of industrial systems. Unexpected circuit failures in such systems during field operation can have severe implications. To address this concern, we developed a method for detecting faulty circuit condition, isolating fault locations, and predicting the remaining useful performance of analog circuits. Through the successive refinement of the circuit's response to a sweep signal, features are extracted for fault diagnosis. The fault diagnostics problem is posed and solved as a pattern recognition problem using kernel methods. From the extracted features, a fault indicator (FI) is developed for failure prognosis. Furthermore, an empirical model is developed based on the degradation trend exhibited by the FI. A particle filtering approach is used for model adaptation and RUP estimation. This method is completely automated and has the merit of implementation simplicity. Case studies on two analog filter circuits demonstrating this method are presented.

Outlier detection rules for fault detection in solar photovoltaic arrays

Abstract: Solar photovoltaic (PV) arrays are unique power sources that may have uncleared fault current when utilizing conventional overcurrent protection devices. To monitor the PV operation and detect these unnoticed faults, outlier detection rules have been proposed for fault detection based on instantaneous PV string current. This paper discusses three rules in detail: 3-Sigma rule, Hampel identifier, and Boxplot rule. Unlike other methods, the proposed methods do not require weather measurement or efforts in model training. Our experimental results show that Hampel identifier and Boxplot rule may be recommended for PV fault detection. Furthermore, the proposed models become more reliable as the number of PV measurements increases. The developed methods may be integrated with PV monitoring system for real-time operation.

HVAC System Fault Root Cause Self-Determination

Abstract: A method for self-determining a root cause of a system fault in a heating, ventilation, and cooling (HVAC) system includes receiving a fault message indicative of a fault condition in an operating characteristic of the HVAC system; determining a causal relationship between the fault condition and a predetermined list of root causes associated with the fault condition; receiving information indicative of operating conditions of the HVAC system; and eliminating at least one root cause that is unrelated to the fault condition in response to the receiving of the information.

An Efficient Method Based on the Electromagnetic Time Reversal to Locate Faults in Power Networks

Abstract: This paper presents a new method based on the electromagnetic time-reversal (EMTR) theory for locating faults in power networks. The applicability of the EMTR technique to locate faults is first discussed. Using the classical transmission-line equations in the frequency domain, analytical expressions are derived to infer the location of the fault. The accuracy of the proposed method is then discussed in relation to the number of observation points adopted to record the fault-originated electromagnetic transients. Then, this paper illustrates the extension of the proposed method to the time domain. The experimental validation of the proposed method is presented by making reference to a reduced-scale coaxial cable system where real faults are hardware-emulated. Finally, the application of the proposed EMTR-based fault-location method to Electromagnetic Transients Program-simulated cases is presented. The simulated test cases are: a mixed overhead/coaxial cable transmission system and the IEEE 34-bus distribution test feeder. Compared to other transient-based fault-location techniques, the proposed method presents a number of advantages, namely, its straightforward applicability to inhomogeneous media (mixed overhead and coaxial power cable lines), the use of a single observation (measurement) point, and robustness against fault type and fault impedance.

Fault Analysis on Distribution Feeders With High Penetration of PV Systems

Abstract: Fault current profile on a PV-dominated distribution feeder is rather different than a conventional feeder. To estimate the fault current profile on such a feeder, the paper proposes a new method which extends the capability of conventional short-circuit analysis method. The paper also shows that this time-varying fault current profile makes it also more difficult to estimate the time it will take for an overcurrent relay/device to interrupt such a fault current. The paper proposes a method for estimation of this operating time also. Performance of the proposed methods has been assessed by simulations on a sample distribution feeder.

A Fault Detection Technique for the Series-Compensated Line During Power Swing

Abstract: A distance relaying scheme is susceptible to power swing. To avoid unintended trip operation during such conditions, a power swing blocking function is utilized in distance relays. However, if a fault occurs during power swing, the relay should detect the fault and trip as soon as possible. The detection of fault in a series-compensated line during the power swing is further complicated due to complex transients produced by series capacitor and the metal-oxide varistor (MOV) protecting it. This paper proposes a negative-sequence current-based technique for detecting all types of faults during the power swing in a series-compensated line. The technique is tested for different series-compensated systems including a 9-bus 3-machine power system. Different types of faults: symmetrical, asymmetrical, and high resistance occurring during the power swing are simulated through EMTDC/PSCAD to test the algorithm. The method is compared with available techniques and found to be accurate and fast.

Wind turbine fault detection and fault tolerant control

Abstract: Wind turbines are increasingly growing larger, becoming more complex, and being located in more remote locations, especially offshore. Interest in advanced controllers for normal operation has expanded in recent years, but fault detection and fault tolerant control for wind turbines is a less well-developed area of interest. In this benchmark challenge, we have reworked a previous challenge paper to present a more sophisticated wind turbine model - a modern 5 MW turbine implemented in the FAST software - and updated fault scenarios. These updates enhance the realism of the challenge and will therefore lead to solutions that are significantly more useful to the wind industry. This paper presents the challenge model and the requirements for challenge participants. In addition, it provides additional information about the faults selected for the challenge and their basis in field data.

State of the art of superconducting fault current limiters and their application to the electric power system

Abstract: Modern electric power systems are becoming more and more complex in order to meet new needs. Nowadays a high power quality is mandatory and there is the need to integrate increasing amounts of on-site generation. All this translates in more sophisticated electric network with intrinsically high short circuit rate. This network is vulnerable in case of fault and special protection apparatus and procedures needs to be developed in order to avoid costly or even irreversible damage. A superconducting fault current limiter (SFCL) is a device with a negligible impedance in normal operating conditions that reliably switches to a high impedance state in case of extra-current. Such a device is able to increase the short circuit power of an electric network and to contemporarily eliminate the hazard during the fault. It can be regarded as a key component for future electric power systems. In this paper the state of the art of superconducting fault current limiters mature for applications is briefly resumed and the potential impact of this device on the paradigm of design and operation of power systems is analyzed. In particular the use of the FCL as a mean to allow more interconnection of MV bus-bars as well an increased immunity with respect to the voltage disturbances induced by critical customer is discussed. The possibility to integrate more distributed generation in the distribution grid is also considered.

Recent advances in fault diagnosis by Park's vector approach

Abstract: This paper addresses recent advances in fault diagnosis by Park's Vector Approach, with special emphasis being given to the most recent developments concerning power converter fault diagnosis in variable speed ac drives. With the aim to demonstrate the suitability of such approach for power converters self-diagnostic, a detailed comparison of four algorithms intended for real-time diagnosis is also included. Their performance evaluation is accomplished by means of experimental results, analyzing some key features such as effectiveness, robustness against false alarms, detection speed, implementation effort, tuning effort and computational burden.

A Novel Fault-Location Method for HVDC Transmission Lines Based on Similarity Measure of Voltage Signals

Abstract: In this paper, a method for fault locating in HVDC transmission lines is proposed which only uses the voltage signal measured at one of the line terminals. The postfault voltage signal, in a relatively short-time window, is considered and the corresponding fault location is estimated based on the similarity of the captured voltage signal to existing patterns. In this approach, the Pearson correlation coefficient is used to measure the similarity. Despite simplicity and low complexity of the proposed fault-location method, it does not suffer from the technical problems which are associated with the traveling-wave-based methods, such as the difficulty of identifying traveling wavefronts or the strong dependency of accuracy on the sampling frequency. Numerous training and test patterns are obtained by simulating various fault types in a long overhead HVDC transmission line under different fault location, fault resistance, and prefault current values. The accuracy of the proposed fault-location method is verified using these patterns.

A Fault Classification and Localization Method for Three-Terminal Circuits Using Machine Learning

Abstract: This paper presents a traveling-wave-based method for fault classification and localization for three-terminal power transmission systems. In the proposed method, the discrete wavelet transform is utilized to extract transient information from the recorded voltages. Support-vector-machine classifiers are then used to classify the fault type and faulty line/half in the transmission networks. Bewley diagrams are observed for the traveling-wave patterns and the wavelet coefficients of the aerial mode voltage are used to locate the fault. Alternate Transients Program software is used for transients simulations. The performance of the method is tested for different fault inception angles, different fault resistances, nonlinear high impedance faults, and nontypical faults with satisfactory results.

Unidirectional Fault Current Limiter: An Efficient Interface Between the Microgrid and Main Network

Abstract: Increased fault current level may exceed the rating of the existing network's equipment and disrupt coordination of overcurrent relays (OCRs). Introduction of new dispersed generation (DG) units in a grid connected microgrid is the main reason for increasing the fault current level. To overcome the above-mentioned problems, fault current limiters (FCLs) can be utilized between the microgrid (downstream) and main grid (upstream). Most FCLs have a bidirectional current limiting function. Whereas in the case of a fault in downstream, it is advised to disable the FCL in order to prevent some problems occurring in the microgrid. Power quality (PQ) and reliability of the microgrid as well as coordination between the upstream and downstream OCRs are affected by the bidirectional FCL in case of fault in downstream. In this paper a unidirectional fault current limiter (UFCL) is proposed to achieve a proper interaction between the upstream and downstream. During the fault condition in the main network, the UFCL acts normally; however, in case of fault occurrence or heavy load startup in downstream, the UFCL is disabled to avoid the aforementioned problems in the microgrid. Several simulations and experiments are carried out to demonstrate the effectiveness of the UFCL.

A Traveling-Wave Detection Method Based on Park's Transformation for Fault Locators

Abstract: A novel algorithm for transient detection based on Park's transformation is proposed. It is very simple, self-adapts to electrical noise and phase imbalances, and is appropriate to be used in connection with traveling-wave fault location (TWFL) methods. The proposed technique is evaluated through Electromagnetic Transients Program simulations. A 230-kV transmission system case study is carried out, in which power system voltage and current waveforms are picked up one sample at a time. It is shown that the method is very reliable and suitable for multiterminal TWFL algorithms.

An Adaptive Relaying Scheme for Fuse Saving in Distribution Networks With Distributed Generation

Abstract: In some situations, utilities may try to “save” the fuse of a circuit following temporary faults by de-energizing the line with the fast operation of an upstream recloser before the fuse is damaged. This fuse-saving practice is accomplished through proper time coordination between a recloser and a fuse. However, the installation of distributed generation (DG) into distribution networks may affect this coordination due to additional fault current contributions from the distributed resources. This phenomenon of recloser-fuse miscoordination is investigated in this paper with the help of a typical network that employs fuse saving. The limitations of a recloser equipped with time and instantaneous overcurrent elements with respect to fuse savings, in the presence of DG, are discussed. An adaptive relaying strategy is proposed to ensure fuse savings in the new scenario even in the worst fault conditions. The simulation results obtained by adaptively changing relay settings in response to changing DG configurations confirm that the settings selected theoretically in accordance with the proposed strategy hold well in operation.

FPGA-Based Fast Detection With Reduced Sensor Count for a Fault-Tolerant Three-Phase Converter

Abstract: Fast fault detection (FD) and reconfiguration is necessary for fault tolerant power electronic converters in safety critical applications to prevent further damage and to make the continuity of service possible. The aim of this study is to minimize the number of the used additional voltage sensors in a fault tolerant three-phase converter. In this paper, first a practical implementation of a very fast FD scheme with reduced sensor number is discussed. Then, an optimization in this scheme is also presented to decrease the detection time. For FD, special time and voltage criterion are applied to observe the error in the estimated phase-to-phase voltages for a specific period of time. The proposed optimization is based on the fact that following a detectable fault, two line-to-line voltages will deviate from their respective estimated values. Fault detection is studied for a three-leg two-level fault tolerant converter. Control and FD systems are implemented on a single field-programmable gate array. First, hardware in the loop experiments are carried out to evaluate the implemented schemes. Then, fully experimental tests are performed. The results confirm good performance of the proposed detection schemes, the digital controller and the fault tolerant structure. It is shown that such methods can detect and locate a fault in a few tens of microseconds. In certain cases the optimized scheme can be faster up to 50%, and in the other cases they have the same detection time.