By Topic

Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 2 • Date April 2005

Filter Results

Displaying Results 1 - 23 of 23
  • Partial discharge pulse sequence patterns and cavity development times in transformer oils under AC conditions

    Page(s): 395 - 403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1786 KB) |  | HTML iconHTML  

    Discrete partial discharge (PD) pulse occurrence times within the PD pulse bursts in transformer oils were found to extend from approximately 0.42 to 2.9 μs, with the discrete pulse separation times evincing a weak dependence on the inverse of the oil viscosity. Many PD pulse burst patterns exhibited substantial deviation from the classical behavior, which is normally characterized by successive discrete pulses of ascending amplitude with well defined increases in the pulse separation times. The average elapsed time from the incipient formation for the cavity to the onset of the first partial discharge event extended downwards from 0.62 to 0.42 μs with increasing oil viscosity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigations into the effect of humidity on stator winding partial discharges

    Page(s): 341 - 346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1818 KB) |  | HTML iconHTML  

    Online partial discharge (PD) testing has become a powerful tool to plan the maintenance of stator windings of high voltage motors and generators. Interpretation of PD data is best done by monitoring the trend in PD over time. Unfortunately the trend in PD is sometimes difficult to ascertain, especially if the humidity within the stator is variable over time. This paper shows several examples of how PD is affected by humidity in operating machines. Laboratory experiments were also performed to duplicate this phenomenon. In most practical situations, it appears that the PD activity decreases as the humidity increases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial discharge measurements in air and argon at low pressures with and without a dielectric barrier

    Page(s): 362 - 373
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3742 KB) |  | HTML iconHTML  

    Partial discharge (PD) characteristics in air and argon under low pressures down to 13.3 Pa (0,1 Torr) and 60 Hz AC energization are studied in an energized needle-plane electrode arrangement. The electrode configuration, vacuum chamber, facilities, and electrical connections for the experimental setup are described. Two cases are studied for each of two gases, air and argon, with 20 mm spacing between the two electrodes: (1) with and (2) without a Teflon® cap (dielectric barrier). Results for the four series of experiments and analysis of the discharge current pulse waveforms are presented. Topics discussed are the typical waveforms of the discharge current pulses at different pressures, and discharge current pulse rise time vs. pressure relationships. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial discharge, dissipation factor, and corona aspects for high voltage electric generator stator bars and windings

    Page(s): 347 - 361
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3114 KB) |  | HTML iconHTML  

    High voltage stator windings in modern electric generators are subject to high electrical, mechanical, and thermal stress. Operation of these machines in both air and high pressure hydrogen results in different considerations. Operation in the air environment does not offer the dielectric advantages of operating in high-pressure hydrogen. The two major design factors that are significant for the design of high voltage stator bars to be operated in air, are corona activity and PD activity. These of course are closely related. With the movement to increasing the power density of generators, which means operation at higher voltages and higher insulation stress levels, it has become more critical to be sure the design constraints are met in the stator bar design to minimize both partial discharge activity and corona activity involving the stator bars. The stator bar insulation system must be designed for minimum partial discharge activity and ideally is corona free at the stator winding operating stress levels, and at the operating conditions (temperature and pressure) the generator is subject to. This paper will present the findings associated with the development work in designing, testing and implementing a PD reduced and corona free design. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial discharge pulse pattern recognition using an inductive inference algorithm

    Page(s): 320 - 327
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2626 KB) |  | HTML iconHTML  

    This paper presents a novel approach in the area of time dependent partial discharge (PD) pulse pattern recognition, to applications based on the inductive learning (decision tree) approach. Different attributes based on pulse shape analysis are used as representative feature vectors that can accurately capture the unique and salient characteristics of the PD pulse shape. In the training phase, a decision tree is developed to relate the pulse shape with the cavity size by using inductive machine learning. The C4.5 machine learning algorithm is deployed to realize the tree using the training data, since it has the capability of inferring the rules and to produce the tree in terms of continuous features. During testing, the cavity size is recognized by means of the rules extracted from the decision tree. The dependency between the features and the classes are examined using the mutual information approach. The proposed algorithm possesses the inherent advantage of explaining the result via the self-created rule base as demonstrated by the results obtained. Those self-created rules can be employed as the basis for applying a fuzzy expert system for the classification of void sizes in an easily interpreted fashion. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Source classification of partial discharge for gas insulated substation using waveshape pattern recognition

    Page(s): 374 - 386
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3667 KB) |  | HTML iconHTML  

    Frequency-domain analysis of ultra-high frequency (UHF) signals for source identification of partial discharge (PD) occurring in SF6 inside gas-insulated substation (GIS) has been widely covered in literature. In this, Fast Fourier Transform and Discrete Wavelet Transform based techniques have been extensively applied to derive classifying features from transformed patterns. On the other hand, it appears feasible to develop a time-domain classifier, which derives features directly from the original waveshape. The time-domain classifier is conceptually simple, and requires potentially less computing resources and simpler algorithmic interface with other intelligent techniques due to elimination of frequency-domain transformation. A novel classifier to extract features directly from time-domain waveforms is proposed for classifying SF6 PD from air corona and among the three types of SF6 PD, regardless of changes in PD locations and measurement conditions. Three sets of classifying features are proposed. Encouraging results have been achieved with comprehensive experimental data, which verifies and proves the usefulness and feasibility of the time-domain classifier. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • UHF defect evaluation in gas insulated equipment

    Page(s): 285 - 296
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3754 KB) |  | HTML iconHTML  

    Small defects in SF6 gas-insulated substations like fixed particles (fixed to conductors or on spacer surfaces) or free moving particles can influence the insulation strength of the insulation system. To determine the risk of such defects on the insulation strength, identification of the PD source is one of the most important steps. In this paper, a method to identify defects based on statistical analysis of frequency spectra is introduced. Finally two examples of risk analysis of defects in GIS are shown. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial discharge signal interpretation for generator diagnostics

    Page(s): 297 - 319
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9378 KB) |  | HTML iconHTML  

    Several common sources of discharges activity occurring on generators have been replicated in the laboratory under well-controlled conditions. Each source was evaluated individually and recorded with a phase resolved acquisition system and with a spectrum analyzer. The dominant features of each respective phase resolved partial discharge (PRPD) pattern are presented. The frequency content of the discharge signal at the detection coupler was also investigated. The association of each well-defined type of discharge source, with its specific PRPD pattern, constitutes the basis of our database used for the discharge source recognition during generator diagnostics. The comparison of laboratory results with actual field measurements gathered over the last decade is summarized. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • PD pulse sequence analysis and its relevance for on-site PD defect identification and evaluation

    Page(s): 276 - 284
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2504 KB) |  | HTML iconHTML  

    Digital partial discharge (PD) diagnosis has become a state of the art, but computer aided procedures based on pattern recognition principles are negatively effected by on-site disturbances. The benefits and limits of expert diagnosis compared to machine intelligent systems are discussed. It is pointed out that a sufficient noise resistivity and test voltage independency of the diagnosis concept is a must for a successful on-site PD defect identification and evaluation. Experimental results are presented, taken into account especially novel evaluation procedures, which are more independent from the applied PD sensors. It is shown that PD defect identification on site at operating voltages and respectively disturbed data is still a challenge. A method of resolution with an intelligent noise resistant diagnosis concept is discussed. A hierarchical and redundant approach is presented, which improves the on site PD source identification as well as on-site risk assessment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial discharges at DC voltage: their mechanism, detection and analysis

    Page(s): 328 - 340
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2757 KB) |  | HTML iconHTML  

    A concise review is given of the progress made in the field of partial discharges (PD) at DC voltage. Although ample reference will be made to work of other authors in this field, the paper will concentrate on the progress that was made at Delft University of Technology over a period of 14 years in three PhD projects. In the first project, a start was made with the analysis of the physics of partial discharges at DC voltage and different types of PD were characterized based on parameters like time interval between PD and PD magnitude. In a second project, PD analysis was applied to HVDC apparatus and different means of classification of PD at DC voltage were proposed. In the third project, PD analysis was applied to HVDC mass-impregnated cables and test specifications were proposed. In this paper the work performed in the above three Ph.D. projects is summarized with ample reference to papers of other workers in this field. Attention is given to the mechanism of PD at DC voltage as compared to AC voltage and techniques for measurement and analysis of DC PD patterns. Examples of practical application of DC PD testing are given. Finally, some thoughts on future work are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • PD knowledge rules for insulation condition assessment of distribution power cables

    Page(s): 223 - 239
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (12755 KB) |  | HTML iconHTML  

    This paper discusses practical experiences in the Netherlands with insulation condition assessment of distribution power cable networks by partial discharge diagnosis and database support. In particular, practical steps are discussed in collecting, analysing and processing the diagnostic data for decision support of utility asset management. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A comment concerning the rise times of partial discharge pulses

    Page(s): 196 - 202
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1636 KB) |  | HTML iconHTML  

    The influence of the discharge mechanism upon the rise time of partial discharge pulses is examined. In contrast to the long rise times characterizing the discharge pulses generated by glow discharges, spark discharges exhibit typically short rise times and large magnitude pulses. The occurrence of the latter is favoured by cavities wherein there is a paucity of free electrons that are necessary for electron avalanche formation. As a consequence, breakdowns across these cavities occur under overvoltage conditions, thus leading to space charge formation and photoemission at the cathode; this results in a rapid development of constricted spark-type breakdown channels. The question of detectability of short and long rise time pulses, utilizing PD detectors having different bandwidths, is considered both in the proximity to, as well as far removed from, the discharge sites. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On line PD measurements and diagnosis on power transformers

    Page(s): 216 - 222
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4421 KB) |  | HTML iconHTML  

    On line partial discharge (PD) measurements provide information on the dielectric integrity of the high voltage insulation of oil insulated power transformers during service. These PD measurements are performed using a broadband antenna on an oil valve and UHF detection of PD signals. The sensitivity of this new detection technique is high and immunity for electromagnetic (EM) interference and corona discharges in air outside the transformer is very good. Dielectric faults can be detected in this way in an early stage of development and are classified in four categories. Automatic pattern recognition techniques of phase resolved pulse sequence (PRPS) data are very useful in risk assessment of dielectric faults. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • First electron availability and partial discharge generation in insulation cavities: effect of light irradiation

    Page(s): 387 - 394
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2452 KB) |  | HTML iconHTML  

    An experimental investigation of the behavior of partial discharges occurring in insulation cavities as a function of light irradiation conditions is presented in this paper. Partial discharge inception voltage (PDIV) measurements were performed for different irradiation conditions of the test objects (visible light, of variable intensity, ultra violet (UV) light or absence of irradiation), defect geometry and conductivity of insulating material. It is shown that changes of such factors involve considerable alteration of partial discharge inception features, in terms of both inception voltage and delay time. Depending on applied field, defect geometry, insulating material characteristics and irradiation condition, in fact, partial discharge inception voltage may be influenced prevailingly by background radiation, as generally stated in literature, or by field-assisted electron detrapping from material-cavity interface. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Advanced suppression of stochastic pulse shaped partial discharge disturbances

    Page(s): 265 - 275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4242 KB) |  | HTML iconHTML  

    Digital partial discharge (PD) diagnosis and testing systems are state of the art for performing quality assurance or fault identification on high voltage apparatus as well as commissioning tests. However their on-site application is a rather difficult task as PD information is generally superimposed with electromagnetic disturbances. These disturbances affect negatively all known PD evaluation systems. Especially the detection and suppression of stochastically distributed pulse shaped disturbances is a major problem. To determine such disturbances fast machine intelligent recognition systems are being developed. Three different strategies based on digital signal processing are discussed in this paper, while focusing on time resolved neural signal recognition. The system investigated more closely is currently able to distinguish between PD pulses and disturbances with the disturbances values being ten times higher than the peak values of the PD pulses. Therefore a measuring system acquires the input data in the VHF range (20-100 MHz). The discrimination of the pulses is performed in real time in time domain using fast neural network hardware. With that signal recognition system a noise reassessed phase resolved pulse sequence (PRPS) data set in the CIGRE data format is generated that can be the input source of most PD evaluation software. Optionally a noise reassessed analogue data stream can be generated that is suitable for any conventional PD measuring system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Trends in partial discharge pattern classification: a survey

    Page(s): 248 - 264
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2658 KB) |  | HTML iconHTML  

    Partial discharge (PD) detection, measurement and classification constitute an important tool for quality assessment of insulation systems utilized in HV power apparatus and cables. The patterns obtained with PD detectors contain characteristic features of the source/class of the respective partial discharge process involved. The recognition of the source from the data represents the classification stage. Usually, this stage consists of a two-step procedure, i.e., extraction of feature vector from the data followed by classification/recognition of the corresponding source. The various techniques available for achieving the foregoing task are examined and analyzed; while limited success has been achieved in the identification of simple PD sources, recognition and classification of complex PD patterns associated with practical insulating systems continue to pose appreciable difficulty. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of bulk dielectric polarization upon partial discharge transients: effect of void geometry and orientation

    Page(s): 240 - 247
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2213 KB) |  | HTML iconHTML  

    The induced charge arising from a partial discharge consists of 2 components. One is associated with the actual space charge in the void. The other is related to changes in the polarization of the bulk dielectric. These changes are a direct consequence of the field produced by the space charge. The influence of the void geometry upon the polarization component of the induced charge is examined for a heterogeneous bulk dielectric system. It is demonstrated that, depending on the ratio of the dielectric permittivities and within which dielectric the void is located, the relative magnitude of this component may increase or decrease. The magnitude of this effect is also strongly dependent upon the prolateness/oblateness of the void geometry, and on the orientation of the void with respect to the detecting electrode. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new methodology for the identification of PD in electrical apparatus: properties and applications

    Page(s): 203 - 215
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3944 KB) |  | HTML iconHTML  

    Applications of a new methodology, aimed at the identification of defects occurring in insulation systems of HV apparatus and based on partial discharge (PD) measurements, are presented in this paper. This methodology relies upon the digital acquisition of a large amount of PD pulses and separates the acquired pulses into homogeneous subclasses. Signal processing tools recognize the presence of noise among the different classes. Identification of basic PD source typologies (i.e., internal, corona and surface discharges) is then achieved, resorting to fuzzy algorithms. The proposed procedure is applied to measurements performed on different HV apparatus, such as cables, transformers and rotating machines. The purpose of this paper is to show that the identification process is robust, regarding the measuring circuit, and flexible, so that it can constitute an advanced tool for condition based maintenance, guiding maintenance experts in making decisions on the condition of the insulation system under test. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • IEEE Transactions on Dielectrics and Electrical Insulation - Table of contents

    Page(s): 01
    Save to Project icon | Request Permissions | PDF file iconPDF (1843 KB)  
    Freely Available from IEEE
  • IEEE Dielectrics and Electrical Insulation Society

    Page(s): 0_2
    Save to Project icon | Request Permissions | PDF file iconPDF (1848 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Dielectrics and Electrical Insulation - Information for authors

    Page(s): 04
    Save to Project icon | Request Permissions | PDF file iconPDF (1525 KB)  
    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Dielectrics and Electrical Insulation contains topics concerned with dielectric phenomena and measurements with development and characterization of gaseous, vacuum, liquid and solid electrical insulating materials and systems.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Reuben Hackam