Showing papers on "Fault indicator published in 2001"

Reconstruction-Based Fault Identification Using a Combined Index

Abstract: Process monitoring and fault diagnosis are crucial for efficient and optimal operation of a chemical plant. This paper proposes a reconstruction-based fault identification approach using a combined index for multidimensional fault reconstruction and identification. Fault detection is conducted using a new index that combines the squared prediction error (SPE) and T2. Necessary and sufficient conditions for fault detectability are derived. The combined index is used to reconstruct the fault along a given fault direction. Faults are identified by assuming that each fault in a candidate fault set is the true fault and comparing the reconstructed indices with the control limits. Fault reconstructability and identifiability on the basis of the combined index are discussed. A new method to extract fault directions from historical fault data is proposed. The dimension of the fault is determined on the basis of the fault detection indices after fault reconstruction. Several simulation examples and one practical c...

A New PMU-Based Fault Location Algorithm for Series Compensated Lines

Abstract: This work presents a new fault location algorithm based on phasor measurement units (PMUs) for series compensated lines. Traditionally, the voltage drop of a series device is computed by the device model in the fault locator of series compensated lines, but by using this approach errors are induced by the inaccuracy of the series device model or the uncertainty operation mode of the series device. The proposed algorithm does not utilize the series device model or knowledge of the operation mode of the series device to compute the voltage drop during the fault period. Instead, the proposed algorithm uses the two-step algorithm, prelocation step and correction step, to calculate the voltage drop and fault location. The proposed technique can be easily applied to any series FACTS compensated line. EMTP generated data using a 300 km, 345 kV transmission line has been used to test the accuracy of the proposed algorithm. The tested cases include various fault types, fault locations, fault resistances, fault inception angles, etc. The study also considers the effect of various operation modes of the compensated device during the fault period. Simulation results indicate that the proposed algorithm can achieve up to 99.95% accuracy for most tested cases.

Systems and methods for managing and analyzing faults in computer networks

Abstract: A system (100) for analyzing a fault includes a fault object factory (110) constructed and arranged to receive fault data and create a fault object (112), and a fault diagnosis engine (101) constructed and arranged to perform root cause analysis of the fault object. The system may further include a fault detector (130) constructed and arranged to detect the fault data in a monitored entity, a fault repository (140) constructed and arranged to store and access the fault object; and a fault handler (150) constructed and arranged to be triggered by the fault diagnosis engine to analyze the fault object.

A New Fault Locator for Three-Terminal Transmission Lines Using Two Terminal Synchronized Voltage and Current Phasors

Abstract: With the advent of the high synchronization accuracy of modern phasor measurement units (PMUs), a new approach for accurately locating faults on three-terminal lines is proposed. Using the data measured from two terminals of three-terminal lines, the proposed technique can provide an extremely accurate fault location. The EMTP/ATP simulator is used to demonstrate the performance of the proposed fault locator. The simulation results show that the accuracy of fault location is very high under various fault resistance, fault locations, prefault loading conditions, source impedance, and fault types.

New multi-ended fault location design for two- or three-terminal lines

Abstract: This paper presents a new fault location system for multiterminal power transmission lines. The algorithm used by this system is suitable for inclusion in a numerical protection relay, which communicates with remote relay(s) over a protective relaying channel. The data volume communicated between relays is sufficiently small to be easily transmitted using a digital protection channel. The new algorithm does not require data alignment, pre-fault load flow information, phase selection information, and does not perform iterations to calculate the distance to the fault. Pre-fault load flow, zero-sequence mutual coupling, fault resistance, power system nonhomogeneity, and current infeeds from other line terminals or tapped loads do not affect the fault location accuracy.

System and method for recognizing faults in machines

Abstract: A system and method for diagnosing one or more faults or one or more potential faults in a machine. The system and method has a communications module for communicating machine data between the machine and the system. It also has a fault recognition module for analyzing the machine data, which can determine one or more faults or potential faults in the machine. An expert system module having a fault tree is guided through only a truncated portion of the fault tree based upon output from the fault recognition module.

Forward-looking fault simulation for improved static compaction

Abstract: Fault simulation of a test set in an order different from the order of generation (e.g., reverse- or random-order fault simulation) is used as a fast and effective method to drop unnecessary tests from a test set in order to reduce its size. We propose an improvement to this type of fault simulation process that makes it even more effective in reducing the test-set size. The proposed improvement allows us to drop tests without simulating them based on the fact that the faults they detect will be detected by tests that will be simulated later, hence the name of the improved procedure: forward-looking fault simulation. We present experimental results to demonstrate the effectiveness of the proposed improvement.

Fault locating in ungrounded and high-resistance grounded systems

Abstract: One of the most common and difficult problems to solve in industrial power systems is the location and elimination of the ground fault. Ground faults that occur in ungrounded and high-resistance grounded systems do not draw enough current to trigger circuit breaker or fuse operation, making them difficult to localize. Techniques currently used to track down faults are time consuming and cumbersome. A new approach developed for ground-fault localization on ungrounded and high-resistance grounded low-voltage systems is described. The system consists of a novel ground-fault relay that operates in conjunction with low-cost fault indicators permanently mounted in the circuit. The ground-fault relay employs digital signal processing techniques to detect the fault, identify the faulted phase, and measure the electrical distance away from the substation. The remote fault indicators are used to visually indicate where the fault is located. The resulting system provides a fast, easy, economical, and safe detection system for ground-fault localization.

Method and system for fault diagnosis in a data network

Abstract: Method and system of fault diagnosis in a data network. Specifically, one embodiment of the present invention discloses a method for automating the process of determining faults in a data network. A network management station (NMS) receives filtered fault data from the various subnetworks of computer systems that comprise the data network. Each of the subnetworks have an associated performance manager that monitors, collects and filters fault data from the subnetwork. Each of the performance managers send their respective filtered fault data to the NMS. The NMS further analyses the filtered fault data to identify the fault and locate a source of the fault within the topology of the data network. The NMS can further query the network for additional fault data as necessary. The NMS displays the fault, cause, and location of the cause to a network engineer for correction.

Robust fault isolation for a class of non-linear input?output systems

Abstract: The design and analysis of fault diagnosis methodologies for non-linear systems has received significant attention recently. This paper presents a robust fault isolation scheme for a class of non-linear systems with unstructured modelling uncertainty and partial state measurement. The proposed fault diagnosis architecture consists of a fault detection and approximation estimator and a bank of isolation estimators. Each isolation estimator corresponds to a particular type of fault in the fault class. A fault isolation decision scheme is presented with guaranteed performance. If at least one component of the output estimation error of a particular fault isolation estimator exceeds the corresponding adaptive threshold at some finite time, then the occurrence of that type of fault can be excluded. Fault isolation is achieved if this is valid for all but one isolation estimator. Based on the class of non-linear systems under consideration, fault isolability conditions are rigorously investigated, characterizin...

Apparatus and method for detecting and calculating ground fault resistance

Abstract: The field ground fault detector (100, 200, 500) of the present invention detects a ground fault that occurs in the field circuit and in any associated circuits galvanically connected to the field. The field ground fault detector discerns the ground resistance so that it can be monitored to detect gradual degradation of the ground resistance. The detector estimates the resistance of the ground fault and the location of the ground fault. The detector is able to estimate the location of the ground fault during system operation and during periods of non-operation. The invention utilizes a low frequency square wave oscillator (104) to permit measurement of the ground fault resistance when field voltage is not applied, to insure that there are no blind spots when the field is energized, and to provide a method for estimating the ground fault resistance. The field ground detector can differentiate between ground faults that occur on the AC side form those on the DC side of the Thyristor Bridge.

An accurate fault location technique for distribution lines with tapped loads using wavelet transform

Abstract: This paper investigates the application of wavelet transform as an accurate fault location technique for power distribution lines with tapped loads. When a fault occurs, a transient wave travels from the fault point to substation busbars and load terminals. The time taken for the fault generated transient wave to arrive at busbars or load terminals depends on the distance traveled and the velocity of the travelling wave. In this paper, fault transient detectors (FTDs) based on digital wavelet transform (DWT) are installed at substation busbars and load terminals to capture the time taken for the transient to arrive and be synchronized with a Global Positioning System (GPS) clock. From the recorded time and the topological structure of the network, an accurate fault location is deduced. The fault location technique is validated by EMTP/ATP on an 11 kV distribution line with 7 tapped loads.

Fault location using the high frequency travelling waves measured at a single location on a transmission line

Abstract: The paper describes how the high frequency travelling waves caused by a fault on a transmission line can be observed in the secondary of a conventional protection current transformer. Information extracted from the secondary currents, measured at one location, is used to determine the phases involved in the fault and its location. The validity of the proposed single ended fault location technique is assessed by comparing the fault location decision obtained when analysing the current signals captured by a high frequency disturbance recorder with the actual location of the fault. The actual location was determined using information from a double-ended GPS synchronised travelling wave fault locator and, if available, information from a maintenance crew.

Travelling wave fault locator experience on Eskom's transmission network

Abstract: This paper summarises Eskom's use and experience of recording travelling waves on its transmission grid. TWS fault locators have been extensively utilised, with excellent success, for fault location of transient earth faults on both compensated and uncompensated AC lines as well as on HVDC lines. They have allowed for fault cause identification via burn mark analysis and waveform signatures. Finally, they appear to offer a means for detecting fire caused earth faults through detection of the pre-fault corona.

Developing a fault tolerant power-train control system by integrating design of control and diagnostics

Abstract: Fault detection, isolation and fault tolerant control are investigated for an spark ignition engine. Fault tolerant control refers to a strategy in which the desired stability and robustness of the control system are guaranteed in the presence of faults. In an attempt to realize fault tolerant control, a methodology for integrated design of control and fault diagnostics is proposed. Specifically, the integrated design of control and diagnostics is achieved by combining the integral sliding mode control methodology and observers with hypothesis testing. Information obtained from integral sliding mode control and from observers with hypothesis testing is utilized so that a fault can be detected, isolated and compensated. As an application example, the air and fuel dynamics of an IC engine are considered. A mean value engine model is developed and implemented in Simulink®. The air and fuel dynamics of the engine are identified using experimental data. The proposed algorithm for integration of control and diagnostics is then validated using the identified engine model. Copyright © 2001 John Wiley & Sons, Ltd.

Incipient fault detection and isolation of field devices in nuclear power systems using principal component analysis

Abstract: An integrated method for the detection and isolation of incipient faults in common field devices, such as sensors and actuators, using plant operational data is presented. The approach is based on the premise that data for normal operation lie on a surface and abnormal situations lead to deviations from the surface in a particular way. Statistically significant deviations from the surface result in the detection of faults, and the characteristic directions of deviations are used for isolation of one or more faults from the set of typical faults. Principal component analysis (PCA), a multivariate data-driven technique, is used to capture the relationships in the data and fit a hyperplane to the data. The fault direction for each of the scenarios is obtained using the singular value decomposition on the state and control function prediction errors, and fault isolation is then accomplished from projections on the fault directions. This approach is demonstrated for a simulated pressurized water reactor steam generator system and for a laboratory process control system under single device fault conditions. Enhanced fault isolation capability is also illustrated by incorporating realistic nonlinear terms in the PCA data matrix.

Multiple hypotheses and their credibility in on-line fault diagnosis

Abstract: In this study, a new method that handles multiple hypotheses is presented for fault diagnosis using sequence of event recorders (SERs). To quantify the certainty of hypotheses, a method to calculate their credibility is provided. The proposed techniques are integrated in a generalized alarm analysis module (GAAM) and have been tested with numerous scenarios from the Italian power system.

Fault location estimation based on matching the simulated and recorded waveforms using genetic algorithms

Abstract: Prompt and accurate location of the faults in a large-scale transmission system is critical when system reliability is considered and usually is the first step in the system restoration. The accuracy of fault location estimation essentially depends on the information available. In this paper, the fault location estimation is mathematically formulated as an optimization problem of which the fault location and fault resistances are unknown variables. An efficient genetic algorithm-based searching scheme is developed for obtaining a solution that is globally optimal.

A fault tolerant induction motor drive system by using a compensation strategy on the PWM-VSI topology

Abstract: This paper proposes the possibility of developing fault diagnosis and remedial operating strategies, which enable a fault tolerant induction motor drive system. The fault mode investigated is the case in which a misfiring does occur in one of the power switches. The fault diagnosis is achieved by using a strategy that permits both identification and isolation of the faulty components. The fault tolerance is obtained by reconfiguration of the inverter topology. This allows for continuous free operation of the drive even with complete loss of one of the legs of the inverter. Experimental results demonstrate the validity of the system proposed.

Arc fault detector with diagnostic indicator

Abstract: A protection device for an electrical circuit having a load includes a sensor operatively associated with the electrical circuit to sense current changes and voltage fluctuations in the electrical circuit. A detector receives input from the sensor and compares the input to known arc fault signatures and arc fault mimicking signatures to determine what category of arc fault or mimicked arc fault occurs. The detector then produces an encoded output signal indicative of the category of arc fault or mimicked arc fault. Categories of arc faults include upstream or downstream series, downstream parallel, downstream line to line, and downstream line to ground.

Fault type selection system for identifying faults in an electric power system

Abstract: The fault identification system includes a first logic circuit which is responsive to conventional protective elements which recognize the presence of low resistance single line-to-ground faults for the A, B and C phases on a power transmission line. The first logic circuit includes a portion thereof for recognizing and providing an output indication of single line-to-ground faults, faults involving two phases and three-phase faults, in response to the occurrence of different combinations of outputs from the protective elements. A calculation circuit, when enabled, is used to determine the angular difference between the total zero sequence current and the total negative sequence current for high resistance faults when the protective elements themselves cannot identify fault conditions. The angular difference is in one of three pre-selected angular sectors. An angular difference in the first sector indicates an A phase-to-ground fault or a BC phase-to-phase to ground fault; an angular difference in the second sector indicates a B phase-to-ground fault or a C phase-to-phase to ground fault; and a signal in the third sector indicates a C phase-to-ground fault or an AB phase-to-phase to ground fault. A processor is used to determine which of the two possible for each angle determination is the actual fault type. An output indication of the actual fault type is then provided.

Automatic machinery fault diagnostic method and apparatus

Abstract: The invention relates to an automatic fault diagnostic procedure for machines, such as steam, gas and hydro-turbines, generators, pumps, electrical motors, etc. For each of a plurality of components, for each of a number of possible faults, a total fault symptom strength value is calculated from measured data. If the value is above a predetermined value, the fault symptom strength is plotted and fitted to a trend line to determine an estimate of when the fault symptom strength will exceed a predetermined value. Output messages are then selected based on the fit.

A complete scheme for fault detection, classification and location in transmission lines using neural networks

Abstract: This work presents an artificial neural network (ANN) approach to simulate a complete scheme for distance protection of a transmission line. In order to perform this simulation, the distance protection task was subdivided into different neural network modules for fault detection, fault classification as well as fault location in different protection zones. A complete integration amongst these different modules is then essential for the correct behaviour of the proposed technique. The three-phase voltages and currents sampled at 1 kHz, in pre and post-fault conditions, were utilised as inputs for the proposed scheme. The Alternative Transients Program (ATP) software was used to generate data for a 400 kV transmission line in a faulted condition. The NeuralWorks software was used to set up the ANN topology, train it and obtain the weights as an output. The NeuralWorks software provides a flexible environment for research and the application of techniques involving ANNs. Moreover, the supervised backpropagation algorithm was utilised during the training process.

Ground fault circuit interrupter with functionality for reset

Abstract: A fault circuit interrupter with functionality for reset can include a relay that trips a first circuit when a ground fault or other error is detected in the first circuit. The relay can be a bistable type of relay that is caused to change state by the detection of a ground fault (or other error) in the first circuit. To reset the fault circuit interrupter after it has tripped, a reset mechanism can include means for simulating a ground fault (or other error). A signal can be sent to the relay when a simulated ground fault (or other simulated fault) is output, such that the signal causes the relay to change state to re-close the first circuit after the trip. Accordingly, the interrupter is automatically tested for functionality when it is reset. Moreover, the fault circuit interrupter cannot be reset if the circuitry of the fault circuit interrupter is not operational.

Analysis of fault locating signals for high-impedance grounded systems

Abstract: High-resistance grounding and ungrounded power systems have many advantages, including continuous operation after a ground fault. However, locating ground faults is inherently difficult and is a major disadvantage with these systems. The problem stems from the lack of a good signal, such as a large fault current, that points to the fault. Classical search methods use injected locating signals, but they have shortcomings with intermittent faults, multiple 'same-phase' faults, and closed loop/mesh power networks. New location methods attempt to overcome these previous problems by providing signals that can be used during system operation and with microprocessor-based detectors. This paper explores some of the key technical issues surrounding locating signals. Of concern are the signal flows through the power network including the uniqueness of the signal path. Other issues that are addressed, are signal levels and power requirement, network impedances, and the impact of grounding capacitances and grounding resistances that divert the locating signal.

On-site safety evaluation for earth fault in mining power systems

Abstract: Many mining power systems utilize ineffectively grounded sources to restrict the residual current of single-phase earth fault in order to reduce outage and shock hazard. In practice, with the system expansion, topology changing and insulation aging, the potential residual current and zero sequence voltage for earth fault vary dynamically and some arcing earth faults can easily cause overvoltage and induce multiple faults. In order to improve the system safety, on-site condition monitoring, safety evaluation and preventive maintenance for an earth fault are proposed in this paper. Some techniques for on-line parameters-measurement based on the resonance-measurement principle are presented. Power system operation states are classified into normal secure state, alert state, incipient fault state and fault state. Some security enhancement methods (preventive action and remedial action) for each state are implemented. The prototype for safety evaluation has been developed and installed in industry power systems for several years.

Fault location method for MV cable network

Abstract: This paper presents a method for estimating the location of faults on a radial MV system, which can include many intermediate load taps. In the method nonhomogeneity of the feeder sections is also taken into account. Performance of the technique was investigated using data obtained from EMTP/ATP simulations, based on Dommel (1986). The data recorded during faults in a real MV network were also used. A distribution utility's MV networks are used as an example. The voltage and current data samples obtained from EMTP/ATP simulations or delivered by DFR were converted to a MATLAB format. The 1 kHz sampled data were then used in the MATLAB fault locator model. The basic block diagram of the proposed fault locator is presented. The paper also describes some evaluation results.

Influence of fault arc characteristics on the accuracy of digital fault locators

Abstract: This paper proposes a time domain model of a fault locator with special reference to fault are nonlinearities by applying the MODELS language of the EMTP. It has been found that an impedance relay type locator is significantly influenced by the fault arc nonlinearities, while the current diversion ratio method is not influenced. This validates the advantage of the current diversion approach over the impedance approach.

Integrated design of fault diagnosis and accommodation schemes for a class of nonlinear systems

Abstract: The paper presents an integrated methodology for detecting, isolating and accommodating faults in a class of nonlinear dynamical systems. A fault diagnosis module is used for fault detection and isolation. Based on the fault information obtained during the fault diagnosis procedure, a fault-tolerant control module is designed to compensate for the effects of faults. In the presence of a fault, a nominal controller guarantees the boundedness of all the system signals until the fault is detected. Then the controller is reconfigured after fault detection and after fault isolation, respectively, to improve the control performance using the fault information generated by the diagnosis module. Under certain assumptions, the stability of the closed-loop system is rigorously investigated.