Showing papers on "Fault indicator published in 2011"

Wavelet-based protection strategy for DC faults in multi-terminal VSC HVDC systems

Abstract: A new protection algorithm for DC line faults in multi-terminal high voltage DC (MTDC) systems is proposed in this study A four-terminal MTDC model is used to investigate fault behaviour and detection using the simulation program PSCAD/EMTDC The simulation results are post-processed using Matlab The fault clearing must be done very rapidly, to limit the effect of the fault on neighbouring DC lines because of the rapid increase in DC current However, before clearing the line, the fault location must be detected as soon as possible A rapid fault location detection algorithm is therefore needed, preferably without communication The protection algorithm proposed in this study uses wavelet analysis to detect the fault location based on local measurements The protection algorithm consists of three independent fault criteria, of which two use wavelet analysis The third criterion is based on a detection method in the time domain The latter is an additional detection method independent of wavelet analysis Using a two out of three selection criteria results in an increased reliability of the whole protection algorithm The final objective is to implement a protection algorithm which allows to detect a DC fault within 1 ms without using communication between the participating converter stations

A Probabilistic Fault Detection Approach: Application to Bearing Fault Detection

Abstract: This paper introduces a method to detect a fault associated with critical components/subsystems of an engineered system. It is required, in this case, to detect the fault condition as early as possible, with specified degree of confidence and a prescribed false alarm rate. Innovative features of the enabling technologies include a Bayesian estimation algorithm called particle filtering, which employs features or condition indicators derived from sensor data in combination with simple models of the system's degrading state to detect a deviation or discrepancy between a baseline (no-fault) distribution and its current counterpart. The scheme requires a fault progression model describing the degrading state of the system in the operation. A generic model based on fatigue analysis is provided and its parameters adaptation is discussed in detail. The scheme provides the probability of abnormal condition and the presence of a fault is confirmed for a given confidence level. The efficacy of the proposed approach is illustrated with data acquired from bearings typically found on aircraft and monitored via a properly instrumented test rig.

Machine Condition Prediction Based on Adaptive Neuro–Fuzzy and High-Order Particle Filtering

Abstract: Machine prognosis is a significant part of condition-based maintenance and intends to monitor and track the time evolution of a fault so that maintenance can be performed or the task can be terminated to avoid a catastrophic failure. A new prognostic method is developed in this paper using adaptive neuro-fuzzy inference systems (ANFISs) and high-order particle filtering. The ANFIS is trained via machine historical failure data. The trained ANFIS and its modeling noise constitute an mth-order hidden Markov model to describe the fault propagation process. The high-order particle filter uses this Markov model to predict the time evolution of the fault indicator in the form of a probability density function. An online update scheme is developed to adapt the Markov model to various machine dynamics quickly. The performance of the proposed method is evaluated by using the testing data from a cracked carrier plate and a faulty bearing. Results show that it outperforms classical condition predictors.

Building management system with fault analysis

Abstract: A controller for a building management system is configured to analyze faults in the building management system. The controller detects a fault in the building management system by evaluating data of building management system using a system of rules. The controller determines a conditional probability for each of a plurality of possible fault causes given the detected fault. The controller determines the most likely fault cause by comparing the determined probabilities and electronically reports the most likely fault cause.

Further improvements on impedance-based fault location for power distribution systems

Abstract: In this study, further improvements regarding the fault location problem for power distribution systems are presented. The proposed improvements relate to the capacitive effect consideration on impedance-based fault location methods, by considering an exact line segment model for the distribution line. The proposed developments, which consist of a new formulation for the fault location problem and a new algorithm that considers the line shunt admittance matrix, are presented. The proposed equations are developed for any fault type and result in one single equation for all ground fault types, and another equation for line-to-line faults. Results obtained with the proposed improvements are presented. Also, in order to compare the improvements performance and demonstrate how the line shunt admittance affects the state-of-the-art impedance-based fault location methodologies for distribution systems, the results obtained with two other existing methods are presented. Comparative results show that, in overhead distribution systems with laterals and intermediate loads, the line shunt admittance can significantly affect the state-of-the-art methodologies response, whereas in this case the proposed developments present great improvements by considering this effect.

A Hybrid Framework for Fault Detection, Classification, and Location—Part I: Concept, Structure, and Methodology

Abstract: Bridging the gap between the theoretical modeling and the practical implementation is always essential for fault detection, classification, and location methods in a power transmission-line network. In this paper, a novel hybrid framework that is able to rapidly detect and locate a fault on power transmission lines is presented. The proposed algorithm presents a fault discrimination method based on the three-phase current and voltage waveforms measured when fault events occur in the power transmission-line network. Negative-sequence components of the three-phase current and voltage quantities are applied to achieve fast online fault detection. Subsequently, the fault detection method triggers the fault classification and fault-location methods to become active. A variety of methods-including multilevel wavelet transform, principal component analysis, support vector machines, and adaptive structure neural networks-are incorporated into the framework to identify fault type and location at the same time. This paper lays out the fundamental concept of the proposed framework and introduces the methodology of the analytical techniques, a pattern-recognition approach via neural networks and a joint decision-making mechanism. Using a well-trained framework, the tasks of fault detection, classification, and location are accomplished in 1.28 cycles, significantly shorter than the critical fault clearing time.

Wide-Area Backup Protection Algorithm Based on Fault Component Voltage Distribution

Abstract: A new wide-area backup protection algorithm based on the fault component voltage distribution is proposed in this paper. It is helpful to overcome the problems of complex setting and maloperation under flow transfer of conventional backup protection. The measured values of fault component voltage and current at one terminal of the transmission line are applied to estimate the fault component voltage at the other terminal. Then, the fault element can be identified by the ratio between the measured values and the estimated values. In addition, the speed of fault element identification can be accelerated by a faulted area detection scheme. The proposed method has the advantage of easy setting and low requirement for synchronized wide-area data. The studies performed on the IEEE 39-bus system validate the proposed algorithm under various faults and flow transfer.

A Simple Real-Time Fault Signature Monitoring Tool for Motor-Drive-Embedded Fault Diagnosis Systems

Abstract: The reference frame theory constitutes an essential aspect of electric machine analysis and control. In this study, apart from the conventional applications, it is reported that the reference frame theory approach can successfully be applied to real-time fault diagnosis of electric machinery systems as a powerful toolbox to find the magnitude and phase quantities of fault signatures with good precision as well. The basic idea is to convert the associated fault signature to a dc quantity, followed by the computation of the signal's average in the fault reference frame to filter out the rest of the signal harmonics, i.e., its ac components. As a natural consequence of this, neither a notch filter nor a low-pass filter is required to eliminate fundamental component or noise content. Since the incipient fault mechanisms have been studied for a long time, the motor fault signature frequencies and fault models are very well-known. Therefore, ignoring all other components, the proposed method focuses only on certain fault signatures in the current spectrum depending on the examined motor fault. Broken rotor bar and eccentricity faults are experimentally tested online using a TMS320F2812 digital signal processor (DSP) to prove the effectiveness of the proposed method. In this application, only the readily available drive hardware is used without employing additional components such as analog filters, signal conditioning board, external sensors, etc. As the motor drive processing unit, the DSP is utilized both for motor control and fault detection purposes, providing instantaneous fault information. The proposed algorithm processes the measured data in real time to avoid buffering and large-size memory needed in order to enhance the practicability of this method. Due to the short-time convergence capability of the algorithm, the fault status is updated in each second. The immunity of the algorithm against non-ideal cases such as measurement offset errors and phase unbalance is theoretically and experimentally verified. Being a model-independent fault analyzer, this method can be applied to all multiphase and single-phase motors.

An intelligent system for detecting faults in photovoltaic fields

Abstract: In this work, an intelligent system for automatic detection of fault in PV fields is proposed. This system is based on a Takagi-Sugeno-Kahn Fuzzy Rule-Based System (TSK-FRBS), which provides an estimation of the instant power production of the PV field in normal functioning, i.e, when no faults occur. Then, the estimated power is compared with the real power and an alarm signal is generated if the difference between powers overcomes a threshold. The TSK-FRBS has been trained using data collected from a PV plant simulator, during normal functioning. Preliminary tests were carried out in a simulated framework, by reproducing both normal and fault conditions. Results show that the system can recognize more than 90% of fault conditions, even when noisy data are introduced.

Simple Fault Diagnosis Based on Operating Characteristic of Brushless Direct-Current Motor Drives

Abstract: In this paper, a simple fault diagnosis scheme for brushless direct-current motor drives is proposed to maintain control performance under an open-circuit fault. The proposed scheme consists of a simple algorithm using the measured phase current information and detects open-circuit faults based on the operating characteristic of motors. It requires no additional sensors or electrical devices to detect open-circuit faults and can be embedded into the existing drive software as a subroutine without excessive computation effort. The feasibility of the proposed fault diagnosis algorithm is proven by simulation and experimental results.

Hilbert-Transform-Based Transient/Intermittent Earth Fault Detection in Noneffectively Grounded Distribution Systems

Abstract: Conventional relaying algorithms are mostly based on phasor computation. Since it is difficult to obtain accurate phasor results in fast transient situations, most of the feeder relays fail to correctly respond to transient/intermittent earth faults, which are, however, frequent fault cases in distribution systems. This paper presents a novel approach for fault detection and direction determination for these transient/intermittent faults. The basic idea is to extract the fault direction using the instantaneous power's direction. The instantaneous power is obtained by using Hilbert transform. The proposed direction element inherently utilizes the high-frequency components of the transient fault signals at a conventional sampling rate. Together with an intermittence detection algorithm, a scheme for transient/intermittent earth fault detection has been proposed. It has been implemented as a prototype relay. Electromagnetic Transients Program tests as well as physical model tests have proved the effectiveness of the proposed scheme.

Feature Extraction of Demagnetization Faults in Permanent-Magnet Synchronous Motors Based on Box-Counting Fractal Dimension

Abstract: This paper presents a methodology for feature extraction of a new fault indicator focused on detecting demagnetization faults in a surface-mounted permanent-magnet synchronous motors operating under nonstationary conditions. Preprocessing of transient-current signals is performed by applying Choi-Williams distribution to highlight the salient features of this demagnetization fault. In this paper, fractal dimension calculation based on the computation of the box-counting method is performed to extract the optimal features for diagnosis purposes. It must be noted that the applied feature-extraction process is autotuned, so it does not depend on the severity of the fault and is applicable to a wide range of operating conditions of the motor. The performance of the proposed system is validated experimentally. According to the obtained results, the proposed methodology is reliable and feasible for diagnosing demagnetization faults in industrial applications.

A Novel UHV/EHV Transmission-Line Pilot Protection Based on Fault Component Integrated Impedance

Abstract: Based on the ratio of the sum of the fault component voltage phasors across the two terminals in the transmission line to the sum of the current phasors through the same line, which is defined as fault component integrated impedance in this paper, a new transmission-line pilot protection principle is proposed. When an external fault occurs, the amplitude of the fault component integrated impedance that reflects the capacitance impedance of the line becomes large; When an internal fault occurs, the amplitude of the fault component integrated impedance which reflects the impedance of the system source and the line, becomes relatively small. Therefore, the fault in the line can be detected according to this characteristic. The criterion is not affected by the current through the capacitance and is not affected by the fault resistance. It can be applied to the line with or without shunt reactor. Also, it can be easily set. Both the simulation results with Electromagnetic Transients Program and dynamic model data verify the validity of the proposed principle.

Voltage sag data utilization for distribution fault location

Abstract: Fault location in distribution systems is an important function for outage management and service restoration directly impacting feeder reliability. In this paper, a fault location method based on matching calculated voltage sag data and data gathered at some nodes in the network is proposed. A method for characterization of voltage sags is utilized to reduce amount of transferred data. The proposed method can pinpoint fault location precisely, and is applicable to any complex distribution systems with load taps, laterals, and sub-laterals, single-phase loads, as well as networks with heterogeneous lines. The performance of the proposed method is demonstrated on the IEEE 123-node distribution test system via computer simulations in ATP software.

A Fault Steady State Component-Based Wide Area Backup Protection Algorithm

Abstract: A novel wide area backup protection algorithm to identify fault branch based on the fault steady state component is proposed. Under normal conditions of the power system, subsets of buses called protection correlation regions (PCRs) are formed on the basis of the network topology and phasor measurement unit (PMU) placement. After the fault occurs, by analyzing the fault steady state component of differential current in each PCR, the fault correlation region is confirmed and then a fault correlation factor (FCF), is calculated in real time to locate the fault branch. The simulation results for the 10-generator 39-bus system verify that this method is able to easily identify fault branch with limited measurement points.

Fault detection systems and methods for self-optimizing heating, ventilation, and air conditioning controls

Abstract: A fault detection system for detecting a fault in a process system includes a first circuit configured to modify an input of the process system with a modifying signal. The fault detection system further includes a second circuit configured to receive an output from the process system and configured to determine whether the fault exists based on at least one of a reduction of a signal component and an unexpected transformation of the signal component, wherein the signal component corresponds to a function of the modifying signal.

Fault models of inverter-interfaced distributed generators: Experimental verification and application to fault analysis

Abstract: This paper investigates the fault behaviour of inverter-interfaced distributed generators in stand-alone networks. It is shown that the rapid transient response of the inverter control system allows its fault behaviour to be characterised by quasi steady-state equivalent fault models. The choice of inverter control strategy, control reference frame and the method of active current limiting dominate the fault response, especially in case of unbalanced faults. The proposed fault models can be directly incorporated in conventional fault analysis methods of which an example is given for a faulty islanded microgrid. Model validation is carried out by comparing experimental measurements with results of analytical fault analysis using the developed fault models and PSCAD time domain simulations.

Data-Driven Fault Detection in Aircraft Engines With Noisy Sensor Measurements

Abstract: An inherent difficulty in sensor-data-driven fault detection is that the detection performance could be drastically reduced under sensor degradation (e.g., drift and noise). Complementary to traditional model-based techniques for fault detection, this paper proposes symbolic dynamic filtering by optimally partitioning the time series data of sensor observation. The objective here is to mask the effects of sensor noise level variation and magnify the system fault signatures. In this regard, the concepts of feature extraction and pattern classification are used for fault detection in aircraft gas turbine engines. The proposed methodology of data-driven fault detection is tested and validated on the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS ) test-bed developed by NASA for noisy (i.e., increased variance) sensor signals.

Design of Smart MVDC Power Grid Protection

Abstract: Improved reliability and safety of the medium-voltage dc power distribution systems on board of all electric ships are the objectives of this paper. The authors propose the integration of the self-healing capability against faults of the measurement system in power system fault detection and protection systems. While most of previous work in the literature focuses on either one aspect independently, here, the two are integrated. On one hand, our approach addresses also the case of concurrent power system fault and measurement system fault. On the other hand, the proposed approach must be capable of distinguishing between the two types of failure. The proposed architecture is based on exchange of information between energy conversion and measurement devices. This makes the impact of communication delays critical, so its analysis is provided for the proposed case study. The impact on the performance of the measurement validation and protection systems is derived and can provide hints on the design. The protection method used as case study consists in controlling power converters to ride through the power system fault while maintaining power supply to the vital loads. To overcome failures of the measurement system, invalid data were detected and reconstructed through their expected value.

Optimal Placement of Fault Indicators Using the Immune Algorithm

Abstract: This paper examines the application of the immune algorithm for the problem of optimal placement of fault indicators to minimize the total cost of customer service outage and investment cost of fault indicators. The reliability index of each service zone is derived to solve the expected energy not served due to fault contingency, and the customer interruption cost is then determined according to the customer type and power consumption within the service zone. To demonstrate the effectiveness of the proposed IA methodology and solve the optimal placement of fault indicators, a practical distribution feeder of Taiwan Power Company is selected for computer simulation to explore the cost benefit of fault indicator placement.

Wavelet fault diagnosis and tolerant of induction motor: A review

Abstract: This paper presents a review of the researches done on fault tolerant control types, methods, main objectives of the fault tolerant control and fault diagnosis of induction motor faults that used the wavelet transform. Wavelet transform from the fault diagnosis point of view, is a summary of the wavelet types (continuous and discrete), machine faults, diagnosis methods and their validation, respectively. Types of software, generality of codes, one dimensional and two dimensional DWT and frequency characteristics components of healthy and faulty induction motor are given. Finally, stator short winding and open winding are taken as a case study to show the effectiveness of the wavelet techniques for fault diagnosis. Key words: Wavelet, induction motor, fault diagnosis, fast Fourier transform, fault indicator, fault tolerant control.

A Novel Fault-Location Algorithm for Double-Circuit Transmission Lines Without Utilizing Line Parameters

Abstract: This paper puts forward a novel algorithm for locating faults on double-circuit transmission lines using two-end unsynchronized current measurements. The algorithm does not require line parameters, which is a radical step forward compared to existing approaches, which require this information, so it can be considered as a settings-free algorithm. Only the positive-sequence current phasors during the fault are processed for determining the sought distance to fault and the synchronization angle, limiting thus the amount of data needed to be transferred from each line terminal. The proposed algorithm is derived by applying the Kirchhoff's voltage law around the parallel circuits loops during the fault. The algorithm is applicable for both transposed and untransposed double-circuit lines and is independent of the fault type. Evaluation studies using reliable Alternative Transients Program-Electromagnetic Transients Program simulation data verify that the accuracy of the proposed algorithm is very high under various fault resistances, fault locations, and source impedances.

Method and system for detecting an arc fault in a power circuit

Abstract: The method of detecting an arc fault in a power circuit comprises the following steps. An AC-signal is injected into the power circuit (52) and a response signal that is related to the injected AC-signal is measured in the power circuit (53). A frequency response of the power circuit is determined from the response signal. Then the frequency response is analyzed and a preferred frequency range is identified (54). A signal related to AC- current flowing in the power circuit within the preferred frequency range is measured (56) and an occurrence of an arc fault in the power circuit is signaled depending on the measured signal (58). The system for detecting an arc fault is designed to perform a method as described before.

Transmission line faults detection, classification and location using artificial neural network

Abstract: Transmission lines, among the other electrical power system components, suffer from unexpected failures due to various random causes. These failures interrupt the reliability of the operation of the power system. When unpredicted faults occur protective systems are required to prevent the propagation of these faults and safeguard the system against the abnormal operation resulting from them. The functions of these protective systems are to detect and classify faults as well as to determine the location of the faulty line as in the voltage and/or current line magnitudes. Then after the protective relay sends a trip signal to a circuit breaker(s) in order to disconnect (isolate) the faulty line.The features of neural networks, such as their ability to learn, generalize and parallel processing, among others, have made their applications for many systems ideal. The use of neural networks as pattern classifiers is among their most common and powerful applications. This paper presents the use of back-propagation (BP) neural network architecture as an alternative method for fault detection, classification and isolation in a transmission line system. The main goal is the implementation of complete scheme for distance protection of a transmission line system. In order to perform this, the distance protection task is subdivided into different neural networks for fault detection, fault identification (classification) as well as fault location in different zones. Three common faults were discussed; single phase to ground faults, double phase faults and double phase to ground faults. The result provides a reliable and an attractive alternative approach for the development of a protection relaying system for the power transmission systems.