Complicated Fault Research Articles

A new approach to fault diagnosis in electrical distribution networks using a genetic algorithm

In this paper, a new approach to fault diagnosis in electrical distribution network is proposed. The approach is based upon the parsimonious set covering theory and a genetic algorithm. First, based on the causality relationship among section fault, protective relay action and circuit breaker trip, the expected states of protective relays and circuit breakers are expressed in a strict mathematical manner. Secondly, the well developed parsimonious set covering theory is applied to the fault diagnosis problem. A 0–1 integer programming model is then proposed. Thirdly, a powerful genetic algorithm (GA) based method for the fault diagnosis problem is developed by using information on operations of protective relays and circuit breakers. The developed method can deal with any complicated faults, and simultaneously determine faulty sections and any hidden defects in the feeder protection systems. Test results for a sample electrical distribution network have shown that the developed mathematical model for the fault diagnosis problem is correct, and the adopted GA based method is efficient.

A general model for representing arbitrary unsymmetries in various types of network analysis

When dealing with unsymmetric faults various proposals have been put forward. In general they have been characterized by specific treatment of the single fault in accordance with the structure and impedances involved. The model presented is based on node equations and was originally developed for transient stability studies in order to allow for an arbitrary fault representation as seen from the positive sequence network. The method results in impedances -or admittances-combining the negative sequence and zero sequence representation for the symmetrical network with the structure and electrical constants of the unsymmetry involving one or more buses. These impedances are introduced in the positive sequence network in the nodes involved in the unsymmetrical conditions. In addition the model can be used for static fault current analysis and presents also in this connection a general method of solution; the method is easy to use since the task of user is limited to establishing the node admittance matrix of the unsymmetry expressed in phase coordinates. The paper is completed with two examples showing the application of the method, one fault for which a well known representation exists and one complicated fault situation which has not been treated before for traditional transient stability analysis.

A tabu search approach to fault section estimation in power systems

In this paper, a new method for fault section estimation in power systems based upon the set covering theory and tabu search (TS) technique is proposed. First, a new mathematical model for the fault section estimation problem is developed based upon the simulation of protection system behavior and the well developed parsimonious set covering theory. Secondly, a new method is presented to solve this problem using a TS based method, in order to find the global optimal solution(s) efficiently. Finally, a sample power system is used to demonstrate the feasibility and efficiency of the developed method. The comparison between the developed TS based and the existing genetic algorithm (GA) based approaches to the fault section estimation problem has also been carried out, and many simulation results show that the TS based approach is more efficient than the GA based approach. The key features of this proposed method are that it can deal with very complicated fault scenarios and can find multiple global optimal solutions directly and very efficiently in a single run. Test results suggest that the developed TS based method is very efficient and of promise for on-line applications.

A MANIFOLD GROWTH MODEL THAT UNIFIES SOFTWARE RELIABILITY GROWTH MODELS

Ensuring software reliability is one of the most important issues in software development. High-precision fault rate prediction is a powerful method for ensuring reliability. A variety of highly accurate methods have been proposed to date, the most widely used being software reliability growth models (SRGMs) based on how the cumulative number of faults detected varies over time. This paper presents a manifold model that unifies existing SRGMs. This model, in addition to reducing the labor in selecting the most suitable model for each growth curve, makes it possible to predict the number of remaining faults for complicated fault growth curves with higher accuracy than previously. Using the manifold model, this paper clarifies the relationships between the existing SRGMs. Then, using actual data, it compares the fault estimation accuracy of the manifold model and representative SRGMs, showing the usefulness of this model.

Analysis of random sequential complicated faults on a balanced power system

Abstract The most general complicated fault on a power system may involve grounding of some phases, short-circuit between some phases and isolation of some phases. All these faults may be simultaneous or may occur in an arbitrary sequence. This paper presents the most general method for analysing such faults. Two matrices, which may be called 'the terminal voltage coefficient matrix' and 'the ground fault coefficient matrix', are employed for the analysis. Special formats are suggested for them. The elements of these matrices can be written immediately for any state of the system. The method proposed in this paper imposes no restriction, either on the sequence in which the complicated fault develops or on the instants at which the individual faults develop. Actual phase variables are employed for the analysis. Expressions for transient terminal voltages, transient phase currents and transient neutral currents are obtained in closed forms which are applicable to all faults. The flowchart for a computer program for the analysis of any conceivable random sequential fault is given. Finally, the results for an arbitrary fault on a fictitious equivalent generator are presented.

An expert system for power systems fault analysis

This paper describes an expert system for fault analysis which has been put into field tests in the dispatch centre of the North East China Electric Network. Previous expert systems for fault analysis on transmission power systems are mainly based on information about the operation of protective relays, whereas this new expert system mainly uses information on tripped circuit breakers, which is more readily available. For some complicated faults, a small number of relay signals are needed. Data concerning the distribution and characteristics of protective relays are concealed in the fault models in the knowledge base of the expert system. And consequently the large database normally required for these data is unnecessary. This also enables the expert system to be more easily transplanted to other networks. Furthermore, because it can distinguish the operational performances of different relays, it analyses faults more accurately.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of expert system for operation at substation

An expert system that offers support information in substation fault occurrence is described, focusing on a method for fault section estimation. This system edits fault information and estimates the fault section. With respect to the fault section. With respect to fault section estimation, a method that makes maximum use of sequential information on protective relay and circuit breaker operation even for complicated fault conditions involving multiple faults and incorrect operation or incorrect nonoperation of protective relays and circuit breakers. This system is undergoing field test in a commercial EHV substation, and so far normal operation is reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Investigations of the software testing coupling effect

Fault-based testing strategies test software by focusing on specific, common types of faults. The coupling effect hypothesizes that test data sets that detect simple types of faults are sensitive enough to detect more complex types of faults. This paper describes empirical investigations into the coupling effect over a specific class of software faults. All of the results from this investigation support the validity of the coupling effect. The major conclusion from this investigation is the fact that by explicitly testing for simple faults, we are also implicitly testing for more complicated faults, giving us confidence that fault-based testing is an effective way to test software.

A method for locating fault section by using sequential information at substations

This paper presents a new real-time method for locating fault section at substations. When a fault occurs, considerable information resulting from protective relay operation and circuit-breaker operation is recorded. Using this information an attempt is made to locate the fault section, especially by considering the sequential relationship of the information and by dividing fault areas. Primarily, in this method, the fault area is divided into several sections based on protection area and operation time of protective relays. Next, expecting subsequent operation of backup relays, the “waiting time” for reasoning is given to each divided section. After a lapse of “waiting time,” all the suspected fault sections are extracted and given priority based on the empirical knowledge of experts. A prototype of the expert system was developed for fault section location, which was applied to various complicated fault cases. The effectiveness of the method was proved even in case of multiple faults and no-operation of protective relays the circuit breakers.

Aftershocks of the 1988 January 22 Tennant Creek, Australia Intraplate Earthquakes: Evidence For A Complex Thrust-Fault Geometry

On 1988 January 22 three earthquakes of Ms 6.3–6.7 occurred in a 12-hr period near Tennant Creek (Northern Territory) in the Proterozoic North Australian Craton and produced 32 km of surface rupture on two main scarps. the Lake Surprise scarp is shaped like a boomerang with the east arm trending ESE and the west arm, WSW. the Kunayungku scarp lies 7 km to the northwest and trends ESE. Locations of 211 aftershocks determined using data from portable seismograph arrays define a 10-km by 40-km aftershock zone elongated parallel to the trend of the surface ruptures. In the western and eastern part of the fault zone, aftershocks occur only south of the Kunayungku and eastern Lake Surprise scarps, respectively. In the central section, in contrast, aftershocks lie primarily to the north of the western arm of the Lake Surprise scarp. Focal depths range from the surface to 8km. In all sections the shallowest earthquakes lie closest to the scarps, whereas deeper events lie further away. In cross-section, the aftershocks lie in three distinct inclined zones, which delineate fault surfaces ruptured by the main shocks. Aftershocks are concentrated near the edges of the inferred fault surfaces suggesting that stress was relieved in the centre of the faults by rupture during the main shocks. the inferred fault-plane dips are: 45° to the SSW for the Kunayungku fault, 55° to the NNW for the western Lake Surprise fault and 35° to the SSW for the eastern Lake Surprise fault. These dip directions are consistent with the sense of thrust movement inferred from surface deformation. the reversal of fault dip and sense of movement between the central and end segments requires a complicated fault geometry. the aftershock data would allow a second, south-dipping plane in the central section that does not intersect the surface. This blind fault may be responsible for much of the moment release interpreted from the modelling of broad-band teleseismic waveforms (Choy & Bowman 1989). Rupture of the north-dipping plane may have been controlled by a pre-existing fault marked at the surface by a quartz ridge 5-km long and may be of secondary importance. Although the quartz ridge suggests previous faulting, the absence of significant topographic relief together with estimates of erosion rates suggest an average repeat time in excess of 104yr. Preliminary interpretation of water withdrawal histories and water-level data from a borefield adjacent to the eastern Lake Surprise scarp does not support a causal relationship between the borefield and the occurrence of the earthquakes. The nearby Warramunga (WRA) seismic array provides a record of local earthquake activity from 1965 to the present. the fault area was essentially aseismic until two small earthquakes in 1986 February and a series of six magnitude 4–5 earthquakes in 1987 January, which were followed by more than 1000 aftershocks. The frequency of occurrence of aftershocks declined very slowly in 1987, with p = 0.2 in the modified Omori formula, whereas for the 1988 aftershock sequence, p = 1. The low p during 1987 may have been diagnostic of high stress in the source area during the foreshock sequence, whereas the ‘normal’ p during 1988 indicates a reduction of stress following the main shocks.

The coupling effect: fact or fiction

Fault-based testing strategies test software by focusing on specific, common types of errors. The coupling effect states that test data sets that detect simple types of faults are sensitive enough to detect more complex types of faults. This paper describes empirical investigations into the coupling effect over a specific domain of software faults. All the results from this investigation support the validity of the coupling effect. The major conclusion from this investigation is that by explicitly testing for simple faults, we are also implicitly testing for more complicated faults. This gives us confidence that fault-based testing is an effective means of testing software.

Fractal geometry in the San Andreas Fault System

It has been noted that the spatial distribution of earthquakes and the mode of strain release in the San Andreas fault system is related to the complexity of fault geometry. Because of their rough appearance over many length scales, faults can be regarded as fractal surfaces. Direct estimates of fractal dimension D of portions of the San Andreas fault system between the northern Gabilan Range and the Salton Sea, including the postulated extent of the great 1857 Fort Tejon earthquake, are obtained from measured fault lengths, analogous to the lengths of coastlines as discussed by Mandelbrot. Regions characterized by complicated fault geometry are associated with larger values of D. Based on fault traces mapped at a scale of 1:750,000, D is 1.3 for this reach of the fault defined as a 30‐km‐wide band about a main fault trace. For that part near Parkfield which could be associated with the nucleation of the 1857 earthquake, D is 1.1; at this same scale, D is 1.4 for the San Andreas and related faults near San Bernardino where the 1857 rupture stopped, compared to 1.2 for the San Andreas‐San Juan fault segments near the point of arrest of the 1966 Parkfield earthquake. At finer map scales (1:24,000 and 1:62,500) critical lengths of ∼ 500 m and 1 km are identified which might relate to the extent of off‐San Andreas fault offsets. The critical lengths also suggest that fault geometry is not self‐similar. If this fractal geometry persists through the seismic cycle, it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault.

Deep crustal reflections from a Vibroseis survey in northern Switzerland

In 1982 a Vibroseis ® survey comprising 180 km of reflection profiles was run in northern Switzerland in order to investigate the suitability of the crystalline basement for the deposition of highly radioactive waste. A configuration was chosen with 144 channels, 25 m of geophone spacing, 20 s sweeps ranging from 11 to 61 Hz and stacking of 4 or 8 sweeps of 3 simultaneous vibrators at twice the geophone spacing. The listening time was generally 4 s and at 4 sites it was extended to 11s for the detection of deeper crustal reflectors. This survey unravelled the complicated fault and thrust system beneath the Swiss folded Jura mountains. The stack from 4 s to 11 s reveals clearly a strong sloping reflector between 3.0 and 3.5 s which is strong evidence for a pronounced differentiation in the upper crust. A series of reflections is observed between 5.8 and 7.2 s the top of which can be correlated with the Conrad discontinuity. A strong “layered” signal between 9.0 and 9.5 s is interpreted as reflections from the M-discontinuity. The main features are compatible with results from nearby refraction surveys in the southern Rhinegraben rift system which show a distinct velocity increase of about 0.5 km/s in the lower crust at a depth ranging from 15 to 20 km, followed by an inversion zone or a laminated structure before reaching the Moho at about 27 km depth. The correlation of the field recordings with the first 10 s of the up-sweep only, shows some loss of resolution in the uppermost 3 s because of the lower frequency content of the signal. However, the lower parts of the sections are nearly identical. The fact that the deeper reflectors in the sections can consistently be traced laterally is a strong argument for using this processing technique. Thus high-coverage Vibroseis surveys utilizing up-sweep can be processed for deep crustal reflections even if the recording time is restricted to the standard 4 s, provided the surface static corrections are carried out with high precision.

Erawan Field, Gulf of Thailand: A History of Applying Evolving Geophysical Technology to a Complex Geologic Structure: ABSTRACT

The Erawan gas field, with estimated recoverable reserves of 1.5 tcf of natural gas, was discovered in 1972. The drilling locations have all been selected on the basis of complicated reflection seismograph results. The productive section is a Tertiary sandshale sequence of fluvial to shallow-marine origin, and individual sand units rarely exceed 50 ft (15 m) in thickness. The Erawan structure is a complexly faulted graben, with fault block rotation producing an anticlinal attitude. High fault density (200 to 500 m separation) and thin productive beds result in many separate hydrocarbon traps. Commercially productive sands occur at depths between 5,000 and 9,000 ft (1,525 to 2,740 m) subsea. Union Oil Co. of California acquired the acreage in 1968 and End_Page 597------------------------------ shot the first seismic survey the same year. These data were adequate to confirm a thick sedimentary section, and they contained sufficient structural indications to select the initial drill site. By 1974, four different seismic surveys had been conducted. More and more faulting became apparent with improving data quality. To resolve the structural pattern, a high-resolution seismic survey was conducted in 1976. These data first demonstrated the very complicated fault patterns now known to exist. Additionally, processing of this survey proved that migration is essential for fault definition, although dips are relatively shallow. Paradoxically, it was observed that the best seismic correlations across the many faults were predominantly low frequency. Consequently, a low-frequency sei mic survey was initiated in 1979. Interpretation of this survey made it possible to correlate gross sedimentary units over large areas of the structure. These correlations were consistent with well control. In 1979, development plans were completed and a 3-D seismic survey was conducted prior to installation of permanent production facilities. This survey comprised 5,000 line-km of data with subsurface coverage of 25 m in the dip direction and 75 m along strike. Nonstandard processing techniques are being tested, both for Erawan field data and other structures in the Gulf of Thailand. Wavelet processing, utilizing a recorded far-field signature, has shown significant improvement in some cases. Migration before stack has significantly enhanced the data by better fault definition and impro ed correlations across the faults. Development plan for Erawan field consists of five platforms with 12 well slots per platform. Gas will be transported by pipeline to Bangkok and condensate will be separated and offloaded via a single point mooring system. Gas production of 250,000 mcf is planned with first production in the fall of 1981. The development program will continue to be heavily dependent upon detailed analysis of 3-D and other seismic reflection data for optimum positioning of boreholes in both horizontal and vertical dimensions. End_of_Article - Last_Page 598------------

Wrench Fault Tectonics: ABSTRACT

Relations among basin formation, sedimentation, and uplift in response to wrench faulting are well documented, especially in California, and together with rock and clay model laboratory studies, the California examples provide considerable insight to the mechanics of wrench fault tectonics in both space and time. Wrench faults are produced in both pure and simple shear deformation, but it is the unique nature of strain in simple shear which leads to the characteristic en echelon arrangement of related folds and faults, structures which constitute the principal traps for hydrocarbons along wrench faults in many parts of the world. Coalescing and rotated fractures combine within the length of the fault zone to form a braided arrangement of faults around lozenge-shaped, uplifted, and downdropped blocks. Whether an uplift or basin develops depends on the bending geometry of the fault segments and the sense of slip across the wrench fault zone itself. Adjacent highlands along such tectonically active zones may shed great volumes of generally coarse sediment into these equally tectonically active basins, and such basins are typified by unusually thick sequences of coarse clastic sediments stacked in a shingled or Venetian-blind-like arrangement. The structure along the edges of the uplifted blocks may be complicated in detail, involving the geometrical interplay of steeply and gently inclined strata together with variable components of dip and strike separation on faults of diverse attitudes. It is along these complicated fault block margins, however, where favorable traps for hydrocarbons can be anticipated and have yet to be explored in many areas. End_of_Article - Last_Page 1683------------

Structural features in the Dead Sea-Jordan rift zone, interpreted from a combined magnetic-gravity study

The results of a combined analysis of aeromagnetic and gravity data covering the rift and adjacent areas show two different deep structural models: (a) Across the northern and central portions of the rift zone the crustal thickness and the character of the upper mantle remain unchanged. On the other hand, the lithology of the upper crust varies laterally so that the mafic composition of the rock type probably increases from east to west. (b) The southern portion of the rift may be underlain by an anomalous, low-density upper mantle. Local negative gravity anomalies within the rift zone delineate deep depressions, separated by structural highs. The Dead Sea depression is interpreted to be filled by 7.5 km of young, low-density sediments. Local magnetic anomalies which cover the northern portion only are interpreted as basalt flows. This approach enables delineation of fault patterns which support the classic view of sinistral strike slip movement along a complicated fault system.

Axial Imperfections in Filamentary Crystals of Aluminum Nitride. I

Axial dislocations and other imperfections in single-crystal whiskers of aluminum nitride (hexagonal, wurtzite structure) have been studied by transmission electron microscopy. Axial dislocations with c Burgers vectors and faults on the (101̄0) prismatic planes having fault vectors equal to ½ c have been identified. In addition to simple axial dislocations, the variety of axial imperfections included zig-zagged dislocations and wide periodic imperfections attributed to complicated faults, clearly related to the dislocation with a c Burgers vector. One type of AlN whisker with growth direction 〈c+2a〉 always contained an axial dislocation or the related extended defect, and it is thus concluded that the growth of this type of whisker may have involved an axial dislocation.

STRUCTURAL PLAN OF THE JAPAN-OKHOTSK GEOSYNCLINAL PROVINCE AND THE POSITION OF SAKHALIN

The tectonic framework of the Japan-Okhotsk geosyncline is described in detail. The region contains complicated folds and faults which developed during regional geosynclinal subsidence and seems clearly to exemplify contemporaneous deformation during geosynclinal subsidence. B. N. Cooper

Ultra-high-speed relays in the fields of protection and measurement

Ultra-high-speed relays will follow faithfully the cyclic changes of alternating currents of commercial frequency in their operating coils. If these relays are polarized, they can be utilized to provide measuring equipment in which the quantity to be measured is converted into impulses whose time duration is a function of that quantity. They can also be utilized to form schemes of protection for transformers, feeders, generators and the busbars of switchgear, employing the principle of phase comparison. This principle is attractive in many ways, and ultra-high-speed relays enable it to be applied with simplicity and fast operation. Restricted zone protective equipment so constructed can be designed to have an overall operating time of the order of 0.015 sec, and the discrimination between an internal and external fault can be obtained in the first half-cycle of fault current. The factors which have to be taken into consideration to overcome difficulties which arise with this principle in the case of complicated faults are discussed in the paper. Experimental equipments have been tried out successfully on system faults on the Central Electricity Board's system.

Ultra-high-speed relays in the fields of protection and measurement

Ultra-high-speed relays will follow faithfully the cyclic changes of alternating currents of commercial frequency in their operating coils. If these relays are polarized, they can be utilized to provide measuring equipment in which the quantity to be measured is converted into impulses whose time duration is a function of that quantity. They can also be utilized to form schemes of protection for transformers, feeders, generators and the busbars of switchgear, employing the principle of phase comparison. This principle is attractive in many ways, and ultra-high-speed relays enable it to be applied with simplicity and fast operation. Restricted zone protective equipment so constructed can be designed to have an overall operating time of the order of 0.015 sec, and the discrimination between an internal and external fault can be obtained in the first half-cycle of fault current. The factors which have to be taken into consideration to overcome difficulties which arise with this principle in the case of complicated faults are discussed in the paper.Experimental equipments have been tried out successfully on system faults on the Central Electricity Board&apos;s system.