| 1. |
- Gubanski, Stanislaw, 1950
(author)
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Outdoor Polymeric Insulators: Role of Corona in Performance of Silicone Rubber Housings
- 2015
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467374972 ; 2015-December, s. 1-9
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Conference paper (peer-reviewed)abstract
- In the struggle to accept outdoor polymeric insulators as alternatives to the traditionally used porcelain and glass insulators, researchers and engineers have tested numerous ideas. Insulator housings made of silicone rubber (SIR) currently dominate the component design, thanks to their hydrophobic surface properties with excellent long-term durability. Despite of five decades of lasting development, some issues related to the performance of this material in various working conditions still remain to be resolved, including an understanding of the impact of corona discharges on the material deterioration as well as on insulator durability although these are extensively studied questions. The impact on insulator performance of high voltage direct current stress especially needs elucidation.An overview on present use of SIR composite insulators is first provided in this paper. Thereafter the results of recent investigations on the mechanism of corona damage are summarized with an emphasis on the differences between the effects of alternating (AC) and direct current (DC) stresses, demonstrating by evaluating the electrical, mechanical and structural characteristics of SIR-based materials, that the damage is less severe under a DC stress. The effect is attributed to reduction in corona intensity in the vicinity of the material surface by stored electric charge. The same charge has however a positive or negative impact on the insulator voltage withstand under impulse conditions, depending on their polarity.
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| 2. |
- Serdyuk, Yuriy, 1963, et al.
(author)
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Charging Insulating Barrier by Corona in Air in Large Coaxial System
- 2015
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467374972 ; 2015-December, s. 705-708
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Conference paper (peer-reviewed)abstract
- Results of the experimental study and computer simulations of corona charging of an insulating barrier in a large scale coaxial arrangement are reported. A computational model describing transport of charged species generated by corona and their dynamics on dielectric surfaces is presented. The measured and computed voltage-current characteristics of corona discharge are compared and discussed. It is shown that charges deposited on gas-solid dielectric interfaces reach a steady state after few cycles of the applied triangular ac voltage. The electric field induced by the surface charges modifies the field in the entire system and alter corona characteristics.
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| 3. |
- Serdyuk, Yuriy, 1963, et al.
(author)
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Mapping of Fields Induced by Electrical Trees in Polyethylene
- 2015
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467374972 ; 2015-December, s. 860-863
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Conference paper (peer-reviewed)abstract
- A technique for calculating electric field distributions associated with electric trees in polyethylene is presented. The method utilizes images of trees obtained by means of visible-light microscopy and image-to-material conversion for setting up a computational model. Results of calculations of fields induced by various types of single trees in needle-plane electrode system as well as multiple trees in wire-plane system are discussed. For the former, the computed magnitudes of the field strength are compared with those obtained utilizing other advanced imaging techniques.
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| 4. |
- Singh, Shailendra, 1982, et al.
(author)
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Streamer Propagation in Hybrid Gas-Solid Insulation
- 2015
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467374972 ; 2015-December, s. 387-390
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Conference paper (peer-reviewed)abstract
- The influence of a solid dielectric barrier on development of an electrical discharge in air between needle and plane electrodes is analyzed by means of computer simulations. The computational model describing formation and propagation of a streamer in atmospheric air and accounting for charge transport and trapping on barrier surfaces is presented. The results of the simulations performed for 5 cm air gap containing solid barrier (plate) inserted between the needle and plane electrodes are discussed focusing on discharge dynamics and associated electric fields.
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| 5. |
- Xu, Xiangdong, 1984, et al.
(author)
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Spontaneous Partial Discharge Oscillations Studied by Excess Current
- 2015
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467374972 ; 2015-December, s. 55-59
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Conference paper (peer-reviewed)abstract
- This work discusses appearance of spontaneous partial discharge (PD) oscillations in specimen containing dielectrically isolated gas cavity as well as a measurement technique that allows to study such PD activity by quantifying the resulting excess current, which includes both fast PD current pulses and relatively slower charge movements. This is achieved through a comparison of currents measured with and without PDs by simultaneously performed conventional pulse PD detection and dielectric response (DR) measurement from which the excess current wave shape is deduced. The obtained results reveal appearance of an additional “slow” current contribution and this paper discusses how this current is generated and why it may influence the PD activity.
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| 6. |
- Andersson, Johan, 1978, et al.
(author)
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Tracking behaviour in the presence of conductive interfacial defects
- 2009
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781424445592 ; , s. 230-233
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Conference paper (peer-reviewed)abstract
- The study presented in this paper aim at extending the knowledge on how interfacial defects in composite insulation systems may affect surface tracking under contaminated conditions. Model samples mimicking an interfacial conducting defect were made of high temperature vulcanised silicone rubber moulded on epoxy substrate with a circular metallic foil inserted at the interface. They were tested for the tracking resistance by means of the inclined plane test procedure. The samples with defects exhibited shorter time to track compared to reference samples without defects. In addition the tracking was more severe on the defected samples. Electric field simulation performed in parallel revealed that presence of surface contamination increases the distortion of electric field around the defect and thus explain both the effects of more severe damage of material surface and lower time to tracking experienced in this study.
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| 7. |
- Andersson, Mattias, 1985, et al.
(author)
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Invariant Dielectric Strength upon Addition of Low Amounts of HDPE to LDPE
- 2016
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. ; 2016-December, s. 711-714
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Conference paper (peer-reviewed)abstract
- Blending of polyethylenes permits to combine the superior mechanical properties of high-density material with the higher purity that is associated with low-density resins. Mixing different polyethylene architectures offers a lot of advantages, but for electrical applications it is important that there is no detrimental effect on the resulting dielectric strength. Here, the nanostructure of crosslinked blends that comprise low-and high-density polyethylene (LDPE and HDPE) is explored. Despite the presence of higher-melting lamellae the formation of electrical trees under alternating current (AC) conditions is found to be invariant for the investigated HDPE content of 1 to 10 wt%. This observation suggests that the use of polyethylene blends is feasible for AC electrical applications.
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| 8. |
- Atiwi, N., et al.
(author)
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Analysis and Performance of High Voltage DC Power Supplies Used for Low Current Measurements on Dielectric Materials
- 2014
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In: Conference on Electrical Insulation and Dielectric Phenomena Annual Report, 2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Des Moines, IA. - 0084-9162. - 9781479975259 ; , s. 590-593
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Conference paper (peer-reviewed)abstract
- Characterization of the conductive current associated with XLPE, found in power cables requires HVDC power supplies with very stable voltage output. The very low conductivity has led to an increased need of a more accurate measurement technique to characterize the conductive parts of dielectric materials. Commercial HVDC power supplies used for such measurements do not provide a pure DC due to the power electronics that contribute to a high frequency component which in return generates a capacitive current. The generated capacitive current can be difficult to differentiate with the actual measurement of the conductive current. In order to achieve measurements of the conductive current, the influence of the generated capacitive current must be sufficiently lower than the conductive current. By designing a power supply with low ripple generation, the influence of the capacitive current can be diminished. A ripple and harmonic free HVDC power supply consisting of 1 kV battery pack was therefore developed to examine the impact of the high frequency component of commercial HVDC power supplies.
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| 9. |
- Chen, Xiangrong, 1982, et al.
(author)
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Investigation of Temperature Effect on Electrical Trees in XLPE Cable Insulation
- 2012
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781467312509 ; 2, s. 612-615
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Conference paper (peer-reviewed)abstract
- In this paper, combined with the methods of real-time microscopic digital imaging and partial discharge (PD) continuous measurements, the effect of temperature on electrical tree propagation and PDs characteristics in XLPE cable insulation was investigated using an embedded needle electrode arrangement over a range of applied voltages from 9 to 15 kV rms. The temperature of the experiments varied from 10 C up to 70 C, which lay within the rated operating temperature range of XLPE cables. The results obtained show that temperature has dominant effect on electrical tree shapes and growth time. As the electrical tree shapes at lower voltages are influenced by the change of tree channel conductivity, this process appeared to be accelerated greatly by increase of experimental temperature. The tree growth time at higher voltages was decreased at higher temperatures due to the change of material morphology and it was accompanied by intensive PD activity.
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| 10. |
- Chen, Xiangrong, et al.
(author)
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Surface Potential Decay on LDPE and its Nanocomposites
- 2017
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In: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. ; 2017-October, s. 485-488
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Conference paper (peer-reviewed)abstract
- To elucidate capabilities of nanocomposites in a full extend, deep understanding of various physical processes induced by electric fields in the bulk and on surfaces of the materials is needed. This paper reports an investigation of surface potential decay on low-density polyethylene and its mixtures with Al2O3 and MgO nanofillers. Samples of two groups materials with various thicknesses prepeared using different manufacturing processes were used in the study. The samples were pre-charged by negative corona and surface potentials were measured by a non-contact technique at room temperature. The obtained results showed that the addition of nanofillers remarkably slowed down the potential decay process irrespectively of film thicknesses and fabrication processes. This is attributed to the significantly lower conductivities of LDPE nanocomposites as compared to pure material. Moreover, the conductivities of the filled materials exhibited strong electric field dependences. It is postulated that the effect can be related to the increased trap energy in the nanocomposites.
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