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Properties and applications of Dielectric Materials, 2006. 8th International Conference on

Date 26-30 June 2006

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  • [Front cover]

    Page(s): C1
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  • 8th International Conference on Properties and Applications of Dielectric Materials

    Page(s): i
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  • Copyright page

    Page(s): ii
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  • Preface

    Page(s): iii
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  • Conference committee

    Page(s): iv - v
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  • Contents

    Page(s): vi - xxx
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  • Insulation Diagnosis of High Voltage Apparatus by Partial Discharge Investigation

    Page(s): 1 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (13410 KB) |  | HTML iconHTML  

    Investigation of properties of dielectric materials has the fundamental purpose to understand their behaviour once subjected to service stresses and to provide a feedback to material designer and manufacturers. However, an important by-product of such investigation is to single out diagnostic properties, that can allow evaluation of the state of electrical apparatus where these materials are employed. Most of electrical apparatus, in fact, fail due to breakdown or loss of performance of insulation. Therefore, a subtle, but strong, link exists between base material investigation and the development of diagnostic properties for electrical insulation systems. Purpose of this paper is to deal with diagnosis of insulation systems of electrical apparatus, referring in particular to partial discharge detection, which is becoming one of the most effective diagnostic techniques. Problems, limitations and advantages of this technique will be discussed in this paper, showing paramount examples of applications on cables and machines View full abstract»

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  • Promising Characteristics of Nanocomposite Dielectrics

    Page(s): 12 - 22
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    Polymer nanocomposites possess promising high performances as engineering materials, if they are prepared and fabricated properly. It was also clarified that they could provide favorable performances as dielectrics and electrical insulation. Comprehensive reviews were given in literatures by the author firstly in 2004 and secondly in 2005. This review is based on the second paper and covers recent significant findings. It also utilizes a recently proposed multi-core model, i.e. a fine structure of "interaction zone" in order to explain various phenomena associated with nanocomposites View full abstract»

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  • Performance and Diagnostics of Biologically Contaminated Insulators

    Page(s): 23 - 30
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    Biological growth has been observed on insulators installed all over the world. However, so far, its impact on insulator performance is not well known. This paper summarizes a majority of the work published in the field. Based on the gathered experiences, it can be concluded that microbiological growth is unlikely to cause severe degradation of the rubber housings of non-ceramic insulators. Furthermore, it seems that the impact of growth on the insulator performance is rather low. Techniques available for detection and characterisation of growth on insulators are also described and discusses. Among those, laser-induced fluorescence (LIF) spectroscopy has been found to give good results in remote detection of micro-organisms View full abstract»

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  • The Analysis of PD-Sequences from Different Defects

    Page(s): 31 - 35
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5350 KB) |  | HTML iconHTML  

    At the first glance partial discharge processes seem to occur to a large extent at random. But this appearance is often due to the fact, that in many cases partial discharge processes are influenced by local charge accumulations in the region of the defect that are generated by the discharges themselves. Especially in solids these charges prevent the ignition of the next consecutive discharge until the field reset generated by the preceding discharge is overcome, either by a change of the external voltage or by a decrease of the local accumulation of charges. The analysis of pd sequences and not solely data sets accumulated on the basis of the phase angles of occurrence only - revealed the influence of surface and space charges generated by the individual partial discharges. To examine these phenomena in more detail, the pd activity of different types of electric equipment was measured with constant and ramped voltage load. The results revealed that different defects behave differently. The underlying physical phenomena - and especially the influence of the surface conductivity of inner or outer surfaces - will be discussed. In many cases, especially with large scale test objects more than one pd source may be active. The pd signals from different spots may be separated by means of the Pulse Shape Analysis, that uses the distortion of the original signals on the way to the coupling device View full abstract»

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  • Transition of Partial Discharge Behavior with Aging under Square-wave AC Voltage

    Page(s): 36 - 39
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4299 KB) |  | HTML iconHTML  

    Comparison study was carried out on the partial discharge (PD) behaviors in a void under AC voltages with square-wave and sine-wave. The transition of the PD magnitude with aging under square-wave showed the same tendency as that under sine-wave. Moreover, some distinctive characteristics of PDs under square-voltage (e.g. more than two pulses after the voltage rise time and their transition with aging) were observed and their mechanisms were discussed View full abstract»

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  • Efficacy Of Back Propagation Neural Network Based On Various Statistical Measures For Pd Pattern Classification Task

    Page(s): 40 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4268 KB) |  | HTML iconHTML  

    Partial Discharge is the breakdown confined to the localized regions of the insulating medium. The analysis and classification of Partial Discharge based on its site of occurrence is a complex process notwithstanding the intricacies involved in the digital computer acquisition system, since partial discharge is inherently a stochastic and a non-Markovian process in which there can be significant statistical variability. Since each defect has a particular deterioration mechanism, it is imperative to discern the correlation between the discharge patterns and the nature of defect in order to ascertain the quality of insulation. Neural Network which is a non-parametric method has been a recent innovative technique suitable for partial discharge pattern classification. The Back Propagation Algorithm Neural Network is verified and validated for the various inputs based on established validation techniques. As against the conventional technique of using mathematical descriptors adopted by previous researchers, unique characteristic input feature vectors have been devised in this work in order to provide a possible solution to a simple yet an effective preprocessing methodology. The efficacy of the classification of the standard partial discharge defect sources has been evaluated and analyzed View full abstract»

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  • Soft-Threshold Wavelet De-Noising Technique Application for a Single Arc Discharge Across a Static Gap

    Page(s): 44 - 47
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    In this paper arc discharge characteristics during standard lightning impulse test are analyzed by proposed soft-threshold shrinkage de-noising technique based on wavelet transform (WT) frame. Experimental data is provided to show that the partial features of original digitally recorded and noise contaminated signals can be preserved by using proposed noise suppression method. In addition to characterization of single arc discharge in the time-frequency domain, WT has been applied to obtained de-noised waveforms. It is shown that not only the frequency content of arc discharge but also the time of its occurrence can be determined using WT View full abstract»

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  • Characteristics of Corona Discharge in an Icicle/Iced-plate Electrode System under Negative DC Voltage

    Page(s): 48 - 51
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    This paper presents the results of a series of experiments on the corona discharges occurring at icicle tips under negative DC voltage, using an icicle-iced-plate electrode system. The corona discharge development processes and the responding discharge current pulses were recorded. The influences of the gap distance, the icicle surface state and the freezing water conductivity on the corona inception voltage (V inc) and volume as well as on the current pulse waveforms were investigated. The results were compared with previous experimental results obtained under positive DC voltage. The results will help to advance our knowledge of the initial discharge activities occurring on the ice-covered insulators View full abstract»

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  • Condition Monitoring of Composite Insulators Using Partial Discharge Analysis

    Page(s): 52 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5216 KB) |  | HTML iconHTML  

    Composite insulator are widely used as an outdoor insulator now days. Deterioation due to severe weather and vandalism are usually undetectable. There are many techniques have been introduced in order to detect the insulator condition, one of the technique is introduce here by using partial discharge analysis. The work has been done by examining the PD patterns and behaviour of three different insulator materials that are subjected to high humidity and pollution in the small chamber. This work has exhibited a condition monitoring of composite insulator using PD analysis. It showed an association between the PDs pattern and behaviour and the insulator condition. In addition the method used has gave an opportunity to do on-line monitoring View full abstract»

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  • The Effect of Humidity on Partial Discharge Measurement

    Page(s): 57 - 60
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    This paper is a study of the effect of humidity on partial discharge measurement in rotating machine. As we know, partial discharge measurement is effected by several factors and the humidity is one of the most important factors. To study the effect of humidity on partial discharge test, slot defect stator bar models were manufactured for data acquisition at 40%, 60% and 70% relative humidity respectively. The data were then analyzed by visual inspection to see the difference of three dimension distribution of Hn( (phi,q) and two dimension distribution of Hqmax(phi), Hqn(phi), Hn (phi), H(q) and H(p). Statistical values were also calculated in order to compare the trend of those parameters at each level of relative humidity. The test result shows that visual inspection in the same stator bar model at each level of relative humidity has different patterns. In addition, the statistical parameters change upon the variation of relative humidity. Therefore, partial discharge measurement without consideration on humidity can lead to misinterpretation View full abstract»

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  • Effects of Copolymerization on Space Charge in Polypropylene

    Page(s): 61 - 64
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    The DSC curve, the DC current and the space charge distribution have been measured on polypropylene (H-PP), block copolymer (B-PP) and random copolymer (Z-PP) copolymerized with Ziegler catalyst, and M-PP copolymerized with metallocene catalyst. The copolymers have 3.0~4.5 wt% of ethylene. B-PP with 4.5 wt% of ethylene had similar DSC curve and space charge distribution to H-PP. The magnitude of DC current is in the order of M-PP>Z-PP>B-PP>H-PP. Space charge in PP and PP copolymers depended on copolymerization, electrode, temperature and so on. The effects of copolymerization on morphology, DC current and space charge distribution of PP and PP copolymers have been also discussed View full abstract»

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  • The Effect of Temperature Gradient on Space Charge and Electric Field Distribution of HVDC Cable Models

    Page(s): 65 - 68
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    This paper deals with the analysis of the effect of temperature gradient applied to polymeric cables on space charge accumulation inside insulation bulk. In particular, experimental measurements on HVDC cable models showed that space charge due to temperature gradient is generally negligible with respect to excess charge injected from the electrodes at electrical fields larger than the threshold for space charge accumulation. The effect of temperature gradient can be revealed only at fields close to the threshold, i.e. 5 to 10 kV/mm, leading, however, to a small extent of charge accumulation, of the order of tens of mC/m View full abstract»

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  • Three-dimensional Space Charge Distribution in Glass Fiber/Epoxy Composites

    Page(s): 69 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4592 KB) |  | HTML iconHTML  

    By the conventional pulsed electroacoustic (PEA) method, only one-dimensional distribution of the average charge over a whole area parallel to the two electrodes can be observed. Therefore, we have developed a new PEA system capable of measuring three-dimensional space charge distribution. Using this system, we measured the charge distribution in glass/epoxy composites made of lattice woven glass fibers and epoxy resin. It has become clear that the space charge accumulation depends on the internal structure of the composite. There appear repetitious positions where a high charge density is observed on the same lateral cross section along the vertical direction in the composite. Such positions agree with the intersections of the glass fibers. These results clearly show that mismatch of the ratio of the conductivity and permittivity between the two composite materials is responsible for the observed space charge View full abstract»

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  • Effects of Electrode on Space Charge Properties of Polyimide Films

    Page(s): 73 - 76
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    Space charge formation in polyimide films, and therefore, charge injection from the electrodes largely depend upon the water content. In order to clarify the injection properties of positive and negative charge carriers, space charge distributions were observed in the polyimide films with different electrode conditions, such as aluminium was evaporated on a surface of the samples. Only when the rear electrode is a semi-conductive material, the evaporated aluminum electrode enhances charge injection. The positive and negative charge carriers had similar electrode effects on injection each other View full abstract»

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  • Space Charge Distribution Behavior of Nano-SiOx and Low-density Polyethylene Composite

    Page(s): 77 - 80
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    The composite of nano-SiOx and low-density polyethylene is prepared with the double-solution method. Space charge distribution in the composite with various nano-SiOx contents is carried out by pulsed electro-acoustic method. It is shown that the amount of space charge in the composite increases with the nano-SiOx content. The space charge in the composite under 50 kV/mm dc stress is mainly hetero, which is very different from that in the pure polyethylene. However, after electrically stressed at 50kV/mm for one hour, homo space charge is found while the composite being short-circuited. It is believed that the homo space charge injects and accumulates during the dc stressing process, which mainly contributes to the formation of the space charge View full abstract»

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  • In-situ Charge Observation in Insulation Layers of Metal-base Printed Circuit Boards

    Page(s): 81 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2595 KB) |  | HTML iconHTML  

    We have developed in-situ space charge measurement system during ageing tests of printed circuit boards by the pulsed electroacoustic method. It can observe space charge profiles at 358 K (85degC) and 85%RH. Experimental results suggest that internal space charge behaviour is strongly affected by the humidity. This technique should contribute to evaluate test methods of insulation layers as well as to investigate the ageing process View full abstract»

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  • Numerical Analysis of PEA Signal in Line-plate Electrode System

    Page(s): 84 - 87
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    The treeing phenomena are well known as a initiation process of electrical breakdown in the electric power cables. It is discussed that the injected charge from electrode is related to the growth of the tree. The space charge measurement technique by the pulsed electro acoustic (PEA) method is widely used. However, the space charge measurement in the non-uniform electric field has not been realized. From the viewpoint, it is considered that the measurement technique of space charge distribution under non-uniform electric field is important for the investigation of the electrical breakdown phenomena. Although the measurement of the space charge signal (PEA signal) in the needle-plate electrode system has been carried out, the PEA signal could not be detected in the needle-plate electrode system. In order to measure the space charge distribution in non-uniform electric field, a numerical analysis model of acoustic wave generation and propagation in a line-plate electrode system have been developed. In this paper, the experimental results and numerical analysis results in the line-plate electrode system have been reported View full abstract»

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  • Dielectric Characteristics of Insulation Layers of Printed Circuit Boards at High Frequencies

    Page(s): 88 - 91
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    Complex permittivities of various polymeric materials used as the insulation layers of printed circuit boards were measured in the frequency range from 1 MHz to 110 GHz using a newly developed dielectric measurement system and three commercial systems. The new system can measure the complex permittivity of rod-shaped lossy specimens, such as polyacetal, without reference materials. Experimental results reveal that the data measured by using the four different systems were in good agreement. The dielectric loss tandelta of most of the insulation layers was more than 0.01 at frequencies on the GHz order. This studies can contribute to clarifying the dielectric properties of materials used in printed circuit boards that affect the total loss of components as well as electromagnetic compatibility View full abstract»

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  • Critical Temperature to Dielectric Degradation of Printed Circuit Board

    Page(s): 92 - 94
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    Dielectric degradation of printed circuit board based on the thermal properties in an open-air environment was investigated. With increase of the temperature, the copper electrodes were oxidized from Cu 2O to CuO; the base material of epoxy laminate was thermally affected to the change of molecular structure and degradation of dielectric properties. With increase of the temperature, the capacitance and surface resistance decreased, the thermal stimulated current increased and showed a valley value near 450 K and a peak value near 490 K View full abstract»

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