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Electrical Insulation (ISEI), Conference Record of the 2012 IEEE International Symposium on

Date 10-13 June 2012

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Displaying Results 1 - 25 of 145
  • Author index

    Publication Year: 2012 , Page(s): 1 - 31
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  • 2012 international symposium on electrical insulation session chairs

    Publication Year: 2012 , Page(s): iv - v
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  • IEEE Dielectrics and Electrical Insulation Society (DEIS)

    Publication Year: 2012 , Page(s): x
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  • 2012 IEEE international symposium on electrical insulation symposium organization

    Publication Year: 2012 , Page(s): iii
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  • Past conferences

    Publication Year: 2012 , Page(s): ix
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  • Table of contents

    Publication Year: 2012 , Page(s): 1 - 10
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  • In memory of John Tanaka (1924 – 2012)

    Publication Year: 2012 , Page(s): vi - vii
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  • Welcome

    Publication Year: 2012 , Page(s): viii
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  • Analytical results of harmonic influenced electrical tree growth images

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    Electrical treeing is a common cause of polymeric insulation failure. Visually oriented research into this ageing mechanism has been limited exclusively to laboratory based exercises. Employing relatively high speed and high resolution cameras have advanced the acquisition of progressive, two dimensional digital colour electrical tree growth images. This paper presents an analysis of processed harmonic influenced electrical tree growth images from a series of laboratory based experiments. The electrical tree growth, quantified using the area, fractal dimension, width length ratio, intensity frequency index, perimeter and estimated volume methods was investigated for a correlation to power quality. The results confirmed total harmonic distortion, waveshape factor and harmonic order were influential factors on electrical tree growth. View full abstract»

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  • Occurrence of partial discharges in low-voltage cables at the failure spot

    Publication Year: 2012 , Page(s): 5 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (387 KB) |  | HTML iconHTML  

    Secondary cabling systems are usually not concerned as objects of diagnostic measurements. However, in case of power plants operating further after their originally planned lifetime, their reliability is a key issue. To perform their complete replacement to achieve the desired level of operation safety is not always economically and technically feasible. Partial discharge testing of low-voltage cables involves several issues that are fundamentally different from middle and high voltage cables. This paper addresses the most basic one, whether partial discharges occur at the failure spot at the relatively low test voltage of selected cable types. To avoid propagation questions, which are to be addressed in the future, as a first step shown in this paper, very short cable samples were prepared with injuries that are similar to those in real life. Partial discharge magnitudes, activity and other processed values were investigated from nominal voltage to test voltage, and the results are shown in this paper. View full abstract»

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  • The electrical trees initiation at different electric field strength in XLPE cable insulation

    Publication Year: 2012 , Page(s): 14 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    In this paper, electrical tree structures once after initiation are presented, and the initiation time of electrical tree at different electric field strength is recorded by the stereomicroscope under continuous voltage. Applied voltage and electrode separation are changed to obtain different field strength. Numerical calculations based on curve fitting show a certain degree of field dependence of the electrical tree initiation time, which leads to a threshold field strength at this experiment system. However, initiation time shows increased dispersion by the decrease of field strength. Even when the field strength is close to the threshold, initiation becomes random. It is inferred that threshold field strength should be considered as an approximate value based on the available experiment results. View full abstract»

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  • The relationship between electric tree aging degree and the equivalent time-frequency characteristic of PD pulses in high voltage cable

    Publication Year: 2012 , Page(s): 18 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (510 KB) |  | HTML iconHTML  

    In the online monitoring on partial discharge of high voltage XLPE cable, severity of insulation electrical tree can be early warned through its partial discharge. This is an important measure to prevent sudden accident in high voltage cable and to ensure the normal operation of power system. This paper will apply the equivalent time-frequency analysis technology classified with PD pulses into the identification of electrical tree degradation of high voltage cable. The electrical tree in the whole insulation of 35kv cable slice is triggered by a tip under rated voltage, and electrical tree photos and PD pulses data are collected in real-time by microscope and PD broadband detection technology, then the relationship between different growth stages of electrical trees and the equivalent time-frequency figure of PD pulses are concluded. In addition, we used double-needle in different depth to trigger electrical trees of different extent in the insulation, concluded the relationship between the two electrical trees of different extent and the hybrid equivalent time-frequency figure of PD pulses, and found the method to distinguish the two electrical trees. Therefore it can provide criteria for the identification of electrical tree degradation of high voltage cable insulation. View full abstract»

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  • Study on the oxidative stability of palm fatty acid ester (PFAE) as an insulating oil for transformers

    Publication Year: 2012 , Page(s): 22 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (389 KB) |  | HTML iconHTML  

    Today, esters obtained from plant oils are attracting attention as insulating oils from the viewpoints of renewable resources and low environment impact in the event of leakage. We have developed a palm fatty acid ester (PFAE) synthesized from palm/coconut oil for use as an environmentally friendly insulating oil. PFAE is expected to be an alternative to mineral oil because of its high fluidity and high dielectric characteristics. On the other hand, because insulating oil for transformers is used over several decades, high oxidative stability is required. In our study, we investigate oxidative stability with regard to the electro-chemical characteristics of PFAE compared to another vegetable oil. As a result, the breakdown voltage and total acid value of PFAE showed less change than the other oil. We discuss differences in the oxidation stability of PFAE and it superiority over the other vegetable oil. View full abstract»

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  • Partial discharge properties of ester oils having different molecular structures

    Publication Year: 2012 , Page(s): 26 - 29
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    Partial discharge (PD) properties and dissolved gas analysis (DGA) are investigated on three kinds of fatty acid alkyl esters synthesized from palm oil, fatty acid methyl esters synthesized from soybean oil and from rice bran oil with low viscosity to be adopted in transformers. For comparison, the properties of rapeseed oil of vegetable oil having high viscosity are also investigated. The results revealed that the number of PD and average PD charge depended on the molecular structure of the ester oils. It is indicated that the number of PD of large molecular ester oils and ester oils containing double bonds at hydrocarbon part is relatively few. PD in the ester oils with high viscosity were triggered by bubble. DGA showed that there were no remarkable acetylene gases by PD in the ester oils, though hydrogen gas was generated. CO and CO2 were also generated in the ester oils, especially remarkably generated by PD in ester oils containing double bonds at hydrocarbon part. View full abstract»

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  • Study of electrical and rheological properties of natural and other oils

    Publication Year: 2012 , Page(s): 30 - 33
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    This paper deals with the analysis of promising environmentally compatible electrical insulating fluids for electrical engineering. It starts with the overview of the current state of the art and of the latest trends in the use of biodegradable natural oils. In the experimental part, castor oil, linseed oil, sunflower oil and rapeseed oil as well as their components, fatty acid esters, were studied. Dielectric properties were measured using precision LRC meters Agilent 4284A and 4980A including dielectric liquid test fixture Agilent 16452A. Also, Agilent graphical language environment VEE Pro was used for the communication between a PC and Agilent analyzers. Electrical properties of the above-mentioned oils are presented in the frequency domain in the 20 Hz - 1 MHz in the temperature interval 283 K - 363 K; also shown are rheological properties in the 293 K - 363 K temperature range. View full abstract»

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  • First principles calculations of intrinsic breakdown in covalently bonded crystals

    Publication Year: 2012 , Page(s): 34 - 37
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (213 KB) |  | HTML iconHTML  

    A first principles quantum-mechanical method has been developed for estimating intrinsic breakdown strength of insulating materials. The calculations are based on an average electron model which assumes breakdown occurs when the average energy gain from the electric field and phonon absorption exceeds average energy loss to phonons. Our approach is based on density functional perturbation theory (DFPT) and on the direct integration of electronic scattering probabilities over all possible final states, with no adjustable parameters. Computed intrinsic breakdown field is provided for several covalently bonded materials and compared with experimental data from the literature with good agreement. The numerical model provides physical insight into the material properties which affect breakdown. View full abstract»

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  • Sparkover characteristics of air-CO2 mixed gas in nonuniform field gap

    Publication Year: 2012 , Page(s): 38 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (866 KB) |  | HTML iconHTML  

    The atmospheric carbon dioxide concentration has increased since widespread industrialization began. Moreover, there are currently places where the carbon dioxide concentration in the air is high, for example, inside tunnels and forest fire area. Hence, it is important to research the effect of the CO2 concentration on the insulation characteristics of air. This study examined the sparkover characteristics of air-CO2 mixed gases. Two electrodes were used: a rod 5 mm in diameter and a plane electrode 400 mm in diameter. The gap length was 62.5 mm. Synthetic air (nitrogen: 79%, oxygen: 21%) was used in the sparkover tests, and the sparkover voltage was measured in several air-CO2 mixtures. High DC and AC voltages were applied to the electrodes in the sparkover voltage measurement tests. Streamers were examined under several conditions using an image intensifier. The results show that the sparkover voltage depends on the CO2 concentration. Specifically, when the CO2 level increased 0.01% from 0.75% to 0.76%, the sparkover voltage fell rapidly by approximately 20 kV (from 54.3 kV to 33.7 kV) under a positive DC voltage. Similarly, the sparkover voltage also depends on the CO2 concentration under a negative DC voltage and a high AC voltage. View full abstract»

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  • Electrical resistivity characterization of silicon carbide by various methods

    Publication Year: 2012 , Page(s): 43 - 47
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (902 KB) |  | HTML iconHTML  

    In this paper, the variation of the resistivity of SiC powder at low and high voltage as a function of milling time was investigated by controlling the particle size, morphology and compactness (applied pressure). The particle shape and size of commercially available SiC powders were altered by ball milling. The electrical properties of the various SiC powders were characterized at low voltage by using a pressure controlled ohmmeter and frequency-domain spectroscopy. A resistivity increase from 7 to 54 MΩ.cm was observed when the grinding time increased from 5 to 30 minutes, which corresponded to a decrease of the particle size from 54 μm to ~4.5 μm. The nonlinear characterization I-V for high electrical field was investigated. X-ray diffraction and scanning electron microscopy have been carried out to highlight the size decreasing and crystalline structure of the milled powder. View full abstract»

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  • Dielectric response of filled and flexibilized epoxy resin

    Publication Year: 2012 , Page(s): 53 - 58
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    In this work, several nanostructured microcomposite epoxy resin compounds, with or without flexibilized network, are analyzed. Scanning Electron Microscopy is used for the investigation of the phase separation between the flexibilizer and the polymer matrix. Differential Scanning Calorimetry results showed an enhanced molecular mobility for the polymer chains confirmed the expected influence of the flexibilizer. Also, the addition of micro and nanoparticles into epoxy resin increased the glass transition temperature since the fillers prevent the molecular movement of the polymeric chains. Broadband Dielectric Spectroscopy allowed us to determine the influence of the flexibilizer and the influence of the nano and micro filler ratio on the relaxation time versus temperature. After fitting the relaxation peaks using Havriliak-Negami functions, noticeable differences were observed for the β relaxation processes. View full abstract»

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  • Dielectric properties of UV-cured epoxy films treated with Layer-by-Layer nanosilica architectures

    Publication Year: 2012 , Page(s): 59 - 63
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (950 KB) |  | HTML iconHTML  

    This paper focuses on the preparation and characterization of hybrid organic-inorganic epoxy systems obtained through the application of a Layer by Layer (LbL) assembly on a UV-cured epoxy coating. To this aim, a mixture 90/10 (wt.%) of 3,4-epoxycyclohexylmethyl-3',4"-epoxy-cyclo-hexane carboxylate (CE)/diglycidylether-terminated polydi-methyl-siloxane (GTPDMS) was subjected to LbL deposition of 10 and 20 bilayers of silica (positively charged/negatively charged). The relationship between the dielectric properties and transition temperature (Tg) were investigated. Two dielectric relaxation modes namely α and β were observed, attributed to the molecular motions of the polymer chains. The breakdown voltage decreased with increasing number of nanosilica bilayers deposited. View full abstract»

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  • Dielectric and thermal properties of boron nitride and Silica epoxy composites

    Publication Year: 2012 , Page(s): 64 - 68
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (150 KB) |  | HTML iconHTML  

    Samples containing only submicrometric filler (BN), only nanometric filler (Silica) and both fillers were prepared by gravity moulding. A pure epoxy sample was also prepared to quantify the enhanced properties. Glass transition temperatures were measured by Differential Scanning Calorimetry. Dielectric Breakdown data were analysed using the Weibull statistical method and Dielectric Spectroscopy was used at low and high voltage to measure the samples permittivity. The glass transition temperature is decreased by BN presence but not by nanosilica. At ambient temperature, the β relaxation peak is not affected by nanoparticles nor by applied voltage. Strangely, the sample containing the two nanoparticles type is not affected compared to pure epoxy. On dielectric spectra, a supplementary relaxation peak for samples containing nanosilica is present. This peak is associated with the interphase between nanosilica and polymer. View full abstract»

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  • Effect of TiO2 nanofillers on electrical, thermal and mechanical parameters of epoxy resin

    Publication Year: 2012 , Page(s): 69 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    Nanotechnology is a general term covering a wide range of many fields. It deals with characteristics in nanometer size and/or microscopic regions on materials and functional devices. Adding small amount of nanofillers to epoxy resins can lead to electrical, mechanical and chemical improvements. To evaluate the influence of the nanofillers on the partial discharge inception voltage and breakdown voltage, the measurements of the specimens were carried out under homogeneous (plane-plane) and inhomogeneous (rod-plane) electrical field configurations at temperatures from 23 °C up to 180 °C. In this study, host material, namely bisphenol-A epoxy resin, and related micro filler are the same basic components for all produced samples and TiO2 nanofillers were considered at different percentages up to 10% by weight (pbw). Then nanofillers were mixed with the host material using high speed mechanical mixer and ultrasound device simultaneously to make sure, that they are mixed with the host material homogeneously and in nanoscale, too. Regarding the importance of a homogeneous distribution of nanofillers, an even distribution of them was validated by means of transmission electron microscopy. The results show, that adding nanofillers can increase the PD inception voltage of the specimens up to around 15% above glass transition temperature (Tg) under inhomogeneous field and around 25% above Tg under homogeneous field. The breakdown voltages increased under inhomogeneous field at some concentrations of nanofillers, but the changes are not considerable. Under homogeneous field, the results show, that nanocomposites have higher breakdown voltage up to Tg than the conventional composites. Mechanical and thermal results show also considerable improvements. View full abstract»

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  • A coastal trial facility for high voltage composite cross-arms

    Publication Year: 2012 , Page(s): 78 - 82
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB) |  | HTML iconHTML  

    A trial site has been developed within a substation on the North East coast of Scotland for electrical testing high voltage composite cross-arms. A 400 kV transformer energizes two cross-arms installed on a lattice tower oriented at 90° from each other. A custom made protection system has been designed to keep the equipment within operating limits and minimize potential damage from faults. The purpose of the trial is to monitor the electrical performance of the cross-arms by measuring the leakage current on the surface of the insulating members. Weather monitoring equipment that includes a weather transmitter, a present weather detector and a solar sensor is used to correlate electrical behavior with specific weather phenomena. Cameras overlooking the cross-arms provide information regarding pollution accumulation and snow accretion. A data acquisition and control platform is responsible for recording the measurements. The monitoring system is capable of compiling and transmitting wirelessly a summary of the leakage current and weather information every five minutes. View full abstract»

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  • Study on aging characteristics of silicone rubber insulator sheds using FTIR

    Publication Year: 2012 , Page(s): 83 - 86
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    In order to explore a method for assessing the aging characteristics of composite insulators, the composite insulators in service were studied using the Fourier Transform Infra-Red (FTIR) test. The influences of several aging factors on the shed materials of composite insulators in service such as shed locations, operating years and environment contamination levels were preliminarily investigated. It indicates that the peak of the FTIR spectra is lower and the main groups are broken for the first shed at the high voltage side and the shed with longer operating years; as for the insulator strings under different environments the effect of contamination level on the FTIR characteristics of the shed is less than that of operating years. View full abstract»

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  • Numerical simulations of ice-covered EHV post station insulator performance equipped with booster sheds

    Publication Year: 2012 , Page(s): 91 - 94
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (747 KB) |  | HTML iconHTML  

    The main objective of this paper is to study numerically the influence of addition of 6 booster sheds (BS) to 2 units of EHV porcelain post insulator on their electrical performance under severe wet-grown ice accumulation based on experimental results. The numerical investigations have been carried out during melting period in order to determine the potential and electric field distributions and the voltage drop along the different air gaps resulting from the addition of BS. Numerical simulations were done using the finite element method (FEM). Adding BS helps to created artificially air gaps which length depends on their position along the ice-covered insulator. Numerical simulations have helped to demonstrate that voltage drop repartition along the different air gap is not uniform. In particularly, it was shown that more that 53% of the applied voltage is concentrated along the first air gap closed to the HV electrode, which also the longest. Also, it was demonstrated that numerical simulations can be useful and an interesting alternative to experimental test in order to improve and optimize the use of BS for improving electrical performance of post insulator under severe icing conditions. View full abstract»

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