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Electrical Insulation, 2004. Conference Record of the 2004 IEEE International Symposium on

Date 19-22 Sept. 2004

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Displaying Results 1 - 25 of 150
  • Online monitoring of temperature in power transformers using optimal linear combination of ANNs

    Publication Year: 2004 , Page(s): 70 - 73
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB) |  | HTML iconHTML  

    Inordinate temperature rise in a power transformer due to load current is known to be the most important factor in causing rapid degradation of its insulation and decides the optimum load catering ability or the loadability of a transformer. The top oil temperature (TOT) and hottest spot temperature (HST) being natural outcome of this process, an accurate estimation of these parameters is of particular importance. IEEE/IEC among others, have proposed procedure to estimate the temperatures, however, the accuracy of the predictions are not always as good as are desired. Unacceptable temperature rise may occur due to several fault conditions other than overloading, and hence warrant an online monitoring of the transformer. This paper presents an improved model for predicting TOT and HST based on artificial neural network (ANN). A series of network architecture (p-trained network) have been proposed and trained for working out this task and are further optimally combined to give an improved accuracy. View full abstract»

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  • Using multivariate statistical method to recognize different aging stages of oil-paper

    Publication Year: 2004 , Page(s): 81 - 84
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    The multivariate statistical method is introduced in this paper to diagnose insulation performance and identify its aging stages. Based on the lifetime model obtained by lifetime tests, a reasonable experimental condition is chosen to age several oil-paper samples for about 240 hours. Determination of partial discharge signal is carried out in the constant interval throughout the whole aging period. There are a total of 31 parameters extracted and 11 were found to be closely correlated to the aging stages and are used as aging characteristic parameters in the following analysis. In order to identify the proper aging conditions, the cluster method is used to analyze 30 vectors extracted from 6 samples at 5 different aging stages. It is shown that different samples have the similar performance at the same aging stage. The 30 vectors are used to obtain discriminant functions. The characteristic vector with eleven-dimensions is mapped to two-dimensions and the other 30 vectors are analyzed using discriminant functions. It is concluded that a reasonable result can be achieved using the discriminant functions. View full abstract»

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  • Power transformer PD sources determination using current signals waveshape and pattern distributions

    Publication Year: 2004 , Page(s): 178 - 181
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (615 KB) |  | HTML iconHTML  

    An experimental investigation into the behaviour of partial discharges (PD) in three different types of defect PD models was carried out to study the characterization features. They include corona and discharge along the outer and inner surface of transformers bushing. The signals were collected by a wideband (WB) PD measurement system. Analyses of the signals indicate that the type of PD source can be determined using the signals shape and the PD pattern. View full abstract»

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  • Neutral ground resistor monitoring schemes

    Publication Year: 2004 , Page(s): 388 - 393
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (769 KB) |  | HTML iconHTML  

    One distribution industrial/utility company in the Middle East has experienced several neutral ground resistor [NGR] failures during the past few years at its residential substations. These NGR's are installed in the neutral of the distribution power system transformers to limit the ground fault current. The failure of these NGR's caused the distribution system to be ungrounded. The existence of a phase to ground failure in the ungrounded power system leads to phase to ground voltage build-up in the other two healthy phases which can result in insulation breakdown and electrical equipment failures. This work is aimed at the development of two schemes and the evaluation of a third commercial existing scheme to detect NGR's failures. View full abstract»

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  • Experimental investigations on different insulating liquids and mixtures for power transformers

    Publication Year: 2004 , Page(s): 237 - 240
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    This paper presents a comparison between mineral, ester and silicone oils, and mixtures with mineral oil based on their mean properties, namely the heat transfer, the dielectric strength, the aging stability and the electrostatic charging tendency (ECT), in order to select the most appropriate one for power transformers. The heat transfer is studied by means of kinematic viscosity. The measurements of breakdown voltage are achieved according to IEC 60156 specifications and analyzed by Gaussian's statistics method. The results of aging tests in temperature and in contact with atmosphere as well as the ECT versus the oil humidity and resistivity are also presented. View full abstract»

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  • Design and building of data warehouse for steam turbine-generator set

    Publication Year: 2004 , Page(s): 12 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    Turbine generator set is the key equipment in a power system. Keeping the turbine generator set working under safe and reliable condition as long as possible is a subject which draws much attention in engineering field and research field. Online monitoring is a means commonly used. Due to the long running time of an online monitoring system, a large amount of complete equipment information is gained that is very useful to condition-based maintenance and data mining of faults. Data warehouse technology, which is the core of turbine generator set diagnosis information memory and reading, is introduced in this paper. The method of design and building of a data warehouse applied to online monitoring and diagnosis is presented Also. View full abstract»

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  • The effect of winding stresses on the pulse endurance of corona resistant magnet wire

    Publication Year: 2004 , Page(s): 169 - 173
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (671 KB) |  | HTML iconHTML  

    Past studies have indicated reliability advantages of using corona resistant magnet wire (CRMW) for insulation systems in motors operated with pulse width modulated (PWM) adjustable speed drives. However, twisted pair testing of CRMW after the application of mechanical stress indicates that these life advantages of CRMW rapidly diminish, where a 60 - 70% reduction in life is observed for each 9% elongation stress. This contrasts with an observed reduction of only ∼25% for standard wire. Hence, it is important to understand how stresses induced in this wire during winding, insertion, and end turn blocking operations can affect magnet wire pulse resistance performance. To this end, pulse endurance life testing of magnet wire twisted pairs was compared with pulse endurance testing of a wound stator model. These tests indicate that the winding stresses observed for stators can be simulated by inducing a mandrel pull stress in the magnet wire prior to forming a twisted pair. The use of this correlation can not only improve the studies of winding stresses on CRMW, but also assess the impact of varnish treatment on winding life. These studies will facilitate further improvement in the insulation system reliability. View full abstract»

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  • Design and realization of an on-line monitoring system for over-voltage in distribution grids

    Publication Year: 2004 , Page(s): 394 - 397
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (715 KB) |  | HTML iconHTML  

    The design and realization of an on-line monitoring system for over-voltage of distribution grids was introduced. This device can monitor waveforms of varied over-voltage on 10 kV bus bar, monitor internal and atmospheric over-voltage, has high frequency response, short response time, and flexible adjustment of parameters. The system has become a long term and stable system in the Chongqing power grid. It can reflect the real over-voltages in power systems objectively and has provided strong scientific evidence for experts when analyzing insulation failures. View full abstract»

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  • Assessment of thermal aging of HVDC converter transformer insulation

    Publication Year: 2004 , Page(s): 230 - 232
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (621 KB) |  | HTML iconHTML  

    An HVDC converter transformer was removed from service and salvaged after 24 years of service. It had not experienced an in-service failure, although others from the same family had failed as a result of overheating. The salvage of the transformer provided an opportunity to observe signs of overheated cellulose, to take paper samples for DP measurements, and to assess the mechanical strength of the bonded CTC. View full abstract»

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  • Estimating motor life using motor circuit analysis predictive measurements. Part II

    Publication Year: 2004 , Page(s): 15 - 17
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (509 KB) |  | HTML iconHTML  

    For pt.I see ibid., p.451-4 (2003). In the first paper (Penrose, et al., 2003), the keys to the implementation of a technology for predictive maintenance and reliability and the ability to estimate how much time is left prior to equipment failure was outlined. The first part of the study was to establish a baseline for electric motor life time estimation using motor circuit analysis techniques was presented. In the second part of the study, variations of operating conditions including environment, load, cycling, and others were evaluated to fine-tune the estimation. The focus of the study is low voltage, random wound machines in a variety of environments. Additional studies are in progress for medium voltage rotating machinery. View full abstract»

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  • Ice progressive stress method: repeatability during full-scale testing of 400 kV line and apparatus insulators and application of the test results

    Publication Year: 2004 , Page(s): 560 - 563
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB) |  | HTML iconHTML  

    The ice progressive stress (IPS) method fulfils international requirements and has been included by IEEE in the position paper of accepted ice test procedures Farzanch, M. et al. (2003). The present paper analyses the repeatability of the test results of 400 kV voltage class line cap-and-pin/long rod insulators and circuit breakers. The results of the tests of nine different types of full-scale insulator strings and three different types of full-scale T-formed circuit breakers are analyzed. The analysis of the repeatability showed that the results are repeatable in terms of the variation of the different test parameters. The statistical test results in the form of 50% flashover voltage and standard deviation are completely applicable for the statistical dimensioning (availability calculations) using specially developed computer program. Examples are presented in the paper. View full abstract»

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  • Optimization of corona ring design for long-rod insulators using FEM based computational analysis

    Publication Year: 2004 , Page(s): 480 - 483
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB) |  | HTML iconHTML  

    The paper presents a method to optimize the location and the dimensions of the corona ring for transmission line composite insulators using finite element based software, FEMLAB. The procedure used to optimize the corona ring design, which handles more than one parameter, has been verified with examples that have an analytical solution or known optimal values. In this work the optimization is based on finding the maximum field along the insulator surface, such that this maximum field is well below the corona inception level. The design parameters of the ring diameter, diameter of the ring tube, position of the ring in its vertical plane, and the maximum field that cannot exceed the corona inception level have been used in the optimization process. View full abstract»

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  • The importance of correlating dynamics when performing partial discharge measurements and analysis

    Publication Year: 2004 , Page(s): 117 - 122
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (865 KB) |  | HTML iconHTML  

    Online measurement and assessment of partial discharges has proven to be an effective tool in evaluating the condition of insulation and thereby limiting unscheduled outages. Yet, dynamic factors such as humidity, load, and temperature have a significant effect on PD levels. In the past, this data has not been collected simultaneously with PD measurements - something best done on a continuous basis such that correlation and trends can be revealed. This work will show that the best assessment of insulation condition is based on correlating dynamic environmental and load conditions with PD levels and then trending this information over time. This process will result in superior diagnostics and thereby improved maintenance and outage decisions. Actual data collected from rotating equipment and switchgear will be presented and discussed. View full abstract»

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  • Improvements to the performance of silicone rubber housed composite bushings by means of a resistive coating

    Publication Year: 2004 , Page(s): 324 - 327
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB) |  | HTML iconHTML  

    Local discharges in the vicinity of the mounting flange of composite bushings due to the electric field enhancement and dry band arcing on the surface of composite bushings can cause insulating material degradation leading to failure of the bushing. A proposed solution to this problem by employing a resistive silicone rubber coating on composite HV bushings was investigated. Good agreement was obtained between computer software simulation by FEMLAB® and measurement results of potential and field distributions. Wetting and salt-fog chamber tests verified that the resistive silicone rubber coated composite bushings have superior contamination performance. View full abstract»

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  • Novel measurement methods for in-depth analysis of AC metallized film capacitors

    Publication Year: 2004 , Page(s): 568 - 571
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB) |  | HTML iconHTML  

    Metallized film capacitors with self-healing properties become increasingly relevant for high voltage power applications due to their high capacitance density, high power density, and inherent safety. However, because of a lack of generic design rules, introduction of new capacitor designs requires time-consuming aging tests. We present a novel toolkit of measurement methods with the purpose of gaining a deeper knowledge on aging mechanisms and decreasing the development time for new capacitor designs. View full abstract»

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  • Study of timber crossarms coated with castor oil-based polyurethane resins: electrical and mechanical tests

    Publication Year: 2004 , Page(s): 556 - 559
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (705 KB) |  | HTML iconHTML  

    While many countries, including Norway, have long used laminated wood to great advantage as an alternative material for transmission and distribution line supports, the traditional crossarms made of native wood species are still commonly employed in Brazil. This continued use of wood is attributed mainly to its low cost compared with other elements of the power supply system. However, environmental considerations and the shorter lifetime of wood have changed this situation, intensifying the research in this area. This work discusses two reforested wood species, Slash Pine (Pinus elliottii) and Lemon Eucalyptus (Eucalyptus citriodora), coated with castor oil-based polyurethane resins, as an alternative material for distribution line crossarms, from the standpoint of their mechanical and electrical properties and their low cost. A complete description is also given of the entire coating process. View full abstract»

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  • Study of EHD effect on enhanced condensation heat transfer of dielectric fluid

    Publication Year: 2004 , Page(s): 249 - 252
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    The insulating fluid with low boiling point CFC11 was selected as the working fluid and a double-cycle electrohydrodynamics (EHD) experimental model was designed and made. The experiment on condensation heat transfer inside this model was conducted under electrostatic field. The experimental results showed that the electrostatic field can enhance the condensation heat transfer of the dielectric fluid inside the model greatly, and the condensation heat transfer coefficient increased remarkably. This EHD effect enhanced condensation heat transfer technology and shows much reference value for refrigeration and heat transfer engineering. View full abstract»

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  • EAM insulation for medium-volt power cable applications

    Publication Year: 2004 , Page(s): 362 - 365
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB) |  | HTML iconHTML  

    Traditionally, medium-volt (MV) power cable producers had two choices for insulation. These broad categories are cross-linked polyethylene (XLPE) and ethylene-propylene rubber (EP), and include all of their variations, such as tree-resistant XLPE (TRXLPE), ethylene-propylene rubber (EPR), ethylene-propylene-diene (EPDM), etc. Over the last several years, technology has developed that has allowed polymer producers to offer a new category of material for use in electrical insulation: EAM (ethylene-alkene copolymer). These materials include components other than the traditional ethylene and propylene building blocks and offer advantages in processability, flexibility, and performance. The broad range of melt flow rates, densities, and molecular weight distributions available allows compound producers to find the right properties to balance optimal distributive mixing with extrusion performance. The biggest challenge facing EAM resins as an insulating material is acceptance by a fairly conservative industry. Cable producers must be able to take advantage of materials with improved processing as well as physical and electrical properties in the cost conscious deregulated utility industry. This work will examine the suitability of filled EAM as an insulation category, and will discuss specific types of materials that fall into that category. The paper will provide cable test data in comparison to traditional XLPE and EPDM formulations available today. Test data will include Association of Edison Illuminating Companies (AEIC) Qualification data, Accelerated Cable Life Test (ACLT) results, and ICEA testing, among others. View full abstract»

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  • Condition assessment of butyl insulated power cable used in generating stations

    Publication Year: 2004 , Page(s): 450 - 453
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB) |  | HTML iconHTML  

    Condition assessment of an insulated power cable becomes important when it has reached or exceeded its design life and is still in service. It becomes important to evaluate the mechanical and electrical condition of the cable insulation to determine or estimate its remaining useful service life without sacrificing reliability. This work details the evaluation of samples of unshielded 5 kV, 500 kcmil copper conductor cable with butyl rubber insulation and a neoprene jacket. The cable had been in operational service in excess of 30 years at a fossil generating station of DTE Energy, and had shown external deterioration around the jacket extending into the insulation. The tests included visual inspection of the cable samples, tensile and elongation tests to assess degradation of cable materials, dissipation factor measurement in a wet environment to assess dielectric stability, water tree growth, and electrical tests to determine voltage level at which the cable experiences partial discharge. The tests showed that the dissipation factor was stable, with acceptable bulk dielectric characteristics. However, visual inspection showed that there were areas where the neoprene jacket was no longer bonded to the insulation which were also areas of electrical discharge activity. There were however no in-service cable failures. View full abstract»

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  • Electrical degradation of fiberglass distribution line poles

    Publication Year: 2004 , Page(s): 544 - 547
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (681 KB) |  | HTML iconHTML  

    This work presents experimental results obtained from the electrical degradation of fiberglass distribution line poles. Four types of accelerated aging tests, including single-stress and multistress aging tests, were conducted for various fiberglass samples. Clean fog, salt fog, and 25 kV AC voltage were the aging stresses in these tests. Samples with different surface conditions were also tested in each type of accelerated aging test in order to evaluate the effect of surface conditions on the electrical degradation of fiberglass distribution line poles. The electrical degradation of fiberglass samples is discussed and analyzed through experimental results obtained from the electrical evaluation tests before and after the accelerated aging tests. View full abstract»

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  • Effect of multistress on the lifetime characteristics of magnet wires used in flyback transformer

    Publication Year: 2004 , Page(s): 200 - 203
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB) |  | HTML iconHTML  

    This work presents the results of the effect of multistress on the lifetime characteristics of fine gauge magnet wires used in the flyback transformers, adjustable speed drives, motor windings, ignition coils. Accelerated life tests are performed on AWG 43 gauge Polyesterimide insulated magnet wires. This study uses pulse voltages. Multistress includes high temperature, high frequency, and high voltages. Lifetime analysis provides statistical information such as lifetime characteristics, probability of failures, and lifetime percentiles. This study uses Weibull distribution to model life characteristics. The failure data of the aging tests is used to obtain parameters of the frequency-electrical-thermal life model. The life model is used to describe the behavior of insulation in the presence of multistress and is also used to estimate the lifetime of magnet wires at any desired stress level. The parameters of the frequency-electrical-thermal life model used in this study are obtained by regression analysis. View full abstract»

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  • Stator insulation weak spot localization on a 6 kV synchronous motor

    Publication Year: 2004 , Page(s): 18 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB) |  | HTML iconHTML  

    This work presents the results of a stator insulation weak spot localization measurement on a 6 kV 5.5 MVA motor. The motor in question was build in 1953 and its class B insulation system has been in operation ever since. After 50 years of running, the motor was removed and a new one installed. Visual inspection of the stator didn't show any serious damage, tear or wear. The owner intends to use the motor as a replacement motor in case of an emergency. To increase motor reliability, a stator insulation system replacement is considered. Since the visual inspection didn't show any particular reason to replace the entire insulation system, several diagnostic measurements were performed. This paper describes the results of a PD localization measurement performed on this motor. This novel PD localization technique uses the time of flight of the PD signal through the stator core to pin point the actual PD site of every PD occurrence. The measurement technique and its results will be discussed in-depth. The PD localization measurement detected a region in the insulation system with an elevated PD activity. This localized elevated PD activity supports a decision on which region of the insulation system is best suited for replacement. This is in contrast to replacing the entire insulation system. View full abstract»

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  • Numerical analysis of effect of avalanche space charges on corona onset voltage

    Publication Year: 2004 , Page(s): 245 - 248
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    Based on the Townsend collision theory, the number and field strength of the space charges have great effect on the onset voltage of partial discharge in gaseous insulated apparatus. The facts have not only been proved by many researchers' work, but also been demonstrated by mathematical analysis. In fact, the effects of space charge field created by both the positive ions and the electrons are largely different. The electrons of the head avalanche cause the avalanche to further grow because the electron field strengthens the electric field between the bead avalanche and the anode. And positive ion field also reinforces the electric field between the tail avalanche and the cathode, and the middle areas of the electron avalanche are full of the equivalent ions and electrons, which are called the zone plasma. With growing of the zone plasma in great speed, the gap of electrodes quickly breakdown. Computer programs are developed to calculate the onset voltage. The space charge fields of both the positive ions and the electrons are considered in the calculations. The calculation procedures are represented in detail. Meanwhile, results are gained for the air and the SF6 for a wide range geometrical parameters and gas pressures. The results show that the electrons promote the growth of the avalanche while the positive ions retard the growth of the avalanche. View full abstract»

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  • Identification of three phase induction motor incipient faults using neural network

    Publication Year: 2004 , Page(s): 30 - 33
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB) |  | HTML iconHTML  

    The induction motors are most widely used motors in industrial, commercial and residential sectors because of enormous merits of these over other types of available electrical motors. These motors work under various operating stresses, which deteriorate their motor conditions giving rise to faults. The early detection of these deteriorating conditions in incipient phase and its removal/correction is very necessary for the prevention of any external faults/failure of induction motors reducing repair costs and motor outage time. Fault detection using analytical methods is not always possible because it requires a perfect knowledge of the motor model. The artificial neural network techniques are rather easy to develop and to perform. These networks can be applied when the information about the system is obtained from measurements, which later can be used in the training procedures of the neural networks. Neural detectors can be designed from simulation or experimental tests. In the present paper the applicability/feasibility of artificial neural network (ANN) technique for the detection and identification of incipient faults in an induction motor has been explored. Radial basis function (exact fit) approach has been used for ANN training and test. The applicability of the graphical user interface (GUI) of neural network tool box under Matlab environment has been explored in this paper. The various types of faults have been considered. Three phase instantaneous voltages and currents are utilized in proposed approach. Simulated fault current and voltage data have been used for testing of trained network. View full abstract»

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  • Study on the effect of impulse voltage withstandability on the thermally-aged transformer paper

    Publication Year: 2004 , Page(s): 38 - 41
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (557 KB) |  | HTML iconHTML  

    Transformers play an important role in power transmission. It is, therefore, necessary to know the condition, once the transformer becomes aged. Presently, residual life assessment (RLA) methods are being extensively used to know its condition. The insulation system of a transformer consists of mainly oil and paper; and hence, the conditions of these two materials are critical for reliable operation of transformer. Methodologies are available for RLA studies using different parameters like dissolved gas analysis (DGA), furfural content, and degree of polymerization (DP) etc. However, it is also necessary to study the impulse withstandability of cellulose paper and establish its relationship with DP. In this paper, the effect of ageing of cellulose paper on DP, dielectric strength and impulse withstandability has been studied and a methodology has been developed to know the condition of paper vis-a-vis the impulse withstandability and dielectric strength. View full abstract»

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