The Experts below are selected from a list of 4887 Experts worldwide ranked by ideXlab platform

N Hanasaki - One of the best experts on this subject based on the ideXlab platform.

  • nature of the transition between a ferromagnetic metal and a spin Glass Insulator in pyrochlore molybdates
    Physical Review Letters, 2007
    Co-Authors: N Hanasaki, Kazuyuki Watanabe, T Ohtsuka, I Kezsmarki, S Iguchi, S Miyasaka, Yoshinori Tokura
    Abstract:

    The metal-Insulator transition has been investigated for pyrochlore molybdates R(2)Mo(2)O(7) with nonmagnetic rare-earth ions R. The dynamical scaling analysis of ac susceptibility reveals that the geometrical frustration causes the atomic spin-Glass state. The reentrant spin-Glass phase exists below the ferromagnetic transition. The electronic specific heat is enhanced as compared to the band calculation result, perhaps due to the orbital fluctuation in the half-metallic ferromagnetic state. The large specific heat is rather reduced upon the transition, likely because the short-range antiferromagnetic fluctuation shrinks the Fermi surface.

Zuraimy Adzis - One of the best experts on this subject based on the ideXlab platform.

  • Space charge distribution and leakage current pulses for contaminated Glass Insulator strings in power transmission lines
    IET Generation Transmission & Distribution, 2017
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This study reports an investigation on space charge distribution and leakage current (LC) pulses of four units of Glass Insulators recently removed from service. Simulation works were conducted using finite element software and validated by laboratory experiments. The simulation and experimental results were found to be in good agreement when studying the space charge distribution pattern along the Glass Insulator string. It is evident that the LC waveform can be used to characterise the types of partial discharge according to their occurrence with respect to the AC supply. Thus, the proposed method is viable and reliable to be applied in an online measurement system.

  • Contamination effects on charge distribution measurement of high voltage Glass Insulator string
    Measurement, 2017
    Co-Authors: N.a. A. Othman, Robert Pecsi, Ioan C. Popa, Patricia Gavela, Alin-iulian Dolan, M. Afendi M. Piah, Zuraimy Adzis, Eleonora Darie, John A Morales, Nelson Morales
    Abstract:

    It is certain that accumulated charge greatly enhances the local electric field distribution of Insulator and may lead to breakdown even under nominal voltage. Although research on charge distribution has gained worldwide attention for the past few decades, yet the study of charge distribution on its surface is still insufficient. Therefore, this paper presents the charge distributions measurement on the surfaces of Glass Insulators string without grading ring subject to clean and contaminated conditions. The experimental results revealed that the distribution of charge for Glass Insulator recently removed from service has negative distribution pattern and this is further supported by the simulation work results. Charge injection and extraction occurring at the metal-dielectric interface greatly affects the charge amplitude of the adjacent Insulators. This study also revealed that the presence of contamination affect the charge distribution of the Insulator located near to ground electrode.

  • Partial discharge characterization based on leakage current pulses waveform for contaminated Glass Insulator string
    International Journal of Electrical and Computer Engineering, 2016
    Co-Authors: N. A. Othman, Zuraimy Adzis, M. Afendi M. Piah, Nasir A. Al-geelani
    Abstract:

    This paper deals with the analysis of partial discharge (PD) occurrences based on leakage current (LC) pulses distribution under different level of contamination. In this work, laboratory based contamination performance tests are conducted on four units of Glass Insulator string stacked in I-position. Results show that PD can be characterized (according to their occurrence with respect to the AC supply) as follows: corona discharge occurring dominantly in lightly contaminated Insulators, surface discharge occurring dominantly in medium contaminated Insulators and finally internal discharge occurring dominantly in heavily contaminated Insulators. The ability to distinguish the type of PDs from the LC waveform could be used to monitor and predict the condition of the Insulator. The outcome can be incorporated in a conditioning monitoring system.

  • Leakage current and trapped charge characteristics for Glass Insulator string under contaminated conditions
    2015 IEEE Conference on Energy Conversion (CENCON), 2015
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This paper reports a study on leakage current (LC) and trapped charge characteristics for contaminated Glass Insulator string. Four units of Glass Insulators recently removed from service were contaminated according to IEC 60507. The measurement of trapped charge distribution was made by a radially shaped stainless steel mesh surrounding each Insulator while LC was measured using 100 Q shunt resistor. The results revealed that as the contamination levels increase, the amplitude of LC increases; but the amplitude of trapped charge decreases.

  • Measurement of surface charge distribution on Glass Insulator using steel mesh
    2014 IEEE International Conference on Power and Energy (PECon), 2014
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis, Hussein Ahmad
    Abstract:

    This paper studies the charge distribution on the transmission line Glass Insulator surfaces under two different ac voltages viz. 28 kV and 33 kV. A string of four Insulator units under dry and clean conditions is taken as the main research object. An attempt to capture the accumulated charge has been made by using radially shaped stainless steel mesh placed axially at a distance of 2 cm from each Glass Insulator circumference. Results show that the distribution of charge across each Glass of Insulator in the string is uneven, and the value of surface charge increases with the increment of applied voltage.

Yoshinori Tokura - One of the best experts on this subject based on the ideXlab platform.

  • contrasting magnetic behaviors in rhodium and ruthenium doped cubic perovskite srfeo3 nearly ferromagnetic metal versus spin Glass Insulator
    Angewandte Chemie, 2016
    Co-Authors: Masataka Kinoshita, Yoshinori Tokura, Hideaki Sakai, Naoaki Hayashi, Mikio Takano, Shintaro Ishiwata
    Abstract:

    The effects of Rh and Ru doping for SrFeO3, a helimagnetic metal with a cubic perovskite structure, are studied by magnetic and resistivity measurements. Although SrRhO3 is a paramagnetic metal and SrRuO3 is a ferromagnetic one, the Rh doping induces a nearly ferromagnetic metallic state, whereas the Ru doping induces a spin-Glass insulating state. Mossbauer measurements evidence a marked difference between SrFe0.8Rh0.2O3 and SrFe0.8Ru0.2O3 in the formal valences of Fe, which are estimated to be 4+ and 3.75+, respectively. The contrasting magnetic behaviors of Rh- and Ru-doped SrFeO3 are discussed in terms of the subtle balance between the double-exchange ferromagnetism and the superexchange antiferromagnetism.

  • nature of the transition between a ferromagnetic metal and a spin Glass Insulator in pyrochlore molybdates
    Physical Review Letters, 2007
    Co-Authors: N Hanasaki, Kazuyuki Watanabe, T Ohtsuka, I Kezsmarki, S Iguchi, S Miyasaka, Yoshinori Tokura
    Abstract:

    The metal-Insulator transition has been investigated for pyrochlore molybdates R(2)Mo(2)O(7) with nonmagnetic rare-earth ions R. The dynamical scaling analysis of ac susceptibility reveals that the geometrical frustration causes the atomic spin-Glass state. The reentrant spin-Glass phase exists below the ferromagnetic transition. The electronic specific heat is enhanced as compared to the band calculation result, perhaps due to the orbital fluctuation in the half-metallic ferromagnetic state. The large specific heat is rather reduced upon the transition, likely because the short-range antiferromagnetic fluctuation shrinks the Fermi surface.

N. A. Othman - One of the best experts on this subject based on the ideXlab platform.

  • Space charge distribution and leakage current pulses for contaminated Glass Insulator strings in power transmission lines
    IET Generation Transmission & Distribution, 2017
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This study reports an investigation on space charge distribution and leakage current (LC) pulses of four units of Glass Insulators recently removed from service. Simulation works were conducted using finite element software and validated by laboratory experiments. The simulation and experimental results were found to be in good agreement when studying the space charge distribution pattern along the Glass Insulator string. It is evident that the LC waveform can be used to characterise the types of partial discharge according to their occurrence with respect to the AC supply. Thus, the proposed method is viable and reliable to be applied in an online measurement system.

  • Partial discharge characterization based on leakage current pulses waveform for contaminated Glass Insulator string
    International Journal of Electrical and Computer Engineering, 2016
    Co-Authors: N. A. Othman, Zuraimy Adzis, M. Afendi M. Piah, Nasir A. Al-geelani
    Abstract:

    This paper deals with the analysis of partial discharge (PD) occurrences based on leakage current (LC) pulses distribution under different level of contamination. In this work, laboratory based contamination performance tests are conducted on four units of Glass Insulator string stacked in I-position. Results show that PD can be characterized (according to their occurrence with respect to the AC supply) as follows: corona discharge occurring dominantly in lightly contaminated Insulators, surface discharge occurring dominantly in medium contaminated Insulators and finally internal discharge occurring dominantly in heavily contaminated Insulators. The ability to distinguish the type of PDs from the LC waveform could be used to monitor and predict the condition of the Insulator. The outcome can be incorporated in a conditioning monitoring system.

  • Leakage current and trapped charge characteristics for Glass Insulator string under contaminated conditions
    2015 IEEE Conference on Energy Conversion (CENCON), 2015
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This paper reports a study on leakage current (LC) and trapped charge characteristics for contaminated Glass Insulator string. Four units of Glass Insulators recently removed from service were contaminated according to IEC 60507. The measurement of trapped charge distribution was made by a radially shaped stainless steel mesh surrounding each Insulator while LC was measured using 100 Q shunt resistor. The results revealed that as the contamination levels increase, the amplitude of LC increases; but the amplitude of trapped charge decreases.

  • Measurement of surface charge distribution on Glass Insulator using steel mesh
    2014 IEEE International Conference on Power and Energy (PECon), 2014
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis, Hussein Ahmad
    Abstract:

    This paper studies the charge distribution on the transmission line Glass Insulator surfaces under two different ac voltages viz. 28 kV and 33 kV. A string of four Insulator units under dry and clean conditions is taken as the main research object. An attempt to capture the accumulated charge has been made by using radially shaped stainless steel mesh placed axially at a distance of 2 cm from each Glass Insulator circumference. Results show that the distribution of charge across each Glass of Insulator in the string is uneven, and the value of surface charge increases with the increment of applied voltage.

  • Characterization of charge distribution on the high voltage Glass Insulator string
    Journal of Electrostatics, 2014
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis, N. A. Ahmad, Hussein Ahmad, H. Kamarden, A. A. Suleiman
    Abstract:

    Irregularity in charge distribution of an Insulator may lead to accelerated aging and electrical breakdown. However, knowledge of charge distribution on the insulation surface is still insufficient albeit has gained worldwide attention. The insufficiency is particularly on the charge profile along the string Insulator under AC excitation. Therefore, charges distributions on the surfaces of Glass Insulators without installed grading ring are investigated in this paper. Simulation and experimental results were found in good agreement when studying the charge distribution pattern along Glass Insulator string where the polarity of charge swinging occurs at the center of suspension string Insulator of I-type.

M. Afendi M. Piah - One of the best experts on this subject based on the ideXlab platform.

  • Contamination effects on charge distribution measurement of high voltage Glass Insulator string
    Measurement, 2017
    Co-Authors: N.a. A. Othman, Robert Pecsi, Ioan C. Popa, Patricia Gavela, Alin-iulian Dolan, M. Afendi M. Piah, Zuraimy Adzis, Eleonora Darie, John A Morales, Nelson Morales
    Abstract:

    It is certain that accumulated charge greatly enhances the local electric field distribution of Insulator and may lead to breakdown even under nominal voltage. Although research on charge distribution has gained worldwide attention for the past few decades, yet the study of charge distribution on its surface is still insufficient. Therefore, this paper presents the charge distributions measurement on the surfaces of Glass Insulators string without grading ring subject to clean and contaminated conditions. The experimental results revealed that the distribution of charge for Glass Insulator recently removed from service has negative distribution pattern and this is further supported by the simulation work results. Charge injection and extraction occurring at the metal-dielectric interface greatly affects the charge amplitude of the adjacent Insulators. This study also revealed that the presence of contamination affect the charge distribution of the Insulator located near to ground electrode.

  • Space charge distribution and leakage current pulses for contaminated Glass Insulator strings in power transmission lines
    IET Generation Transmission & Distribution, 2017
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This study reports an investigation on space charge distribution and leakage current (LC) pulses of four units of Glass Insulators recently removed from service. Simulation works were conducted using finite element software and validated by laboratory experiments. The simulation and experimental results were found to be in good agreement when studying the space charge distribution pattern along the Glass Insulator string. It is evident that the LC waveform can be used to characterise the types of partial discharge according to their occurrence with respect to the AC supply. Thus, the proposed method is viable and reliable to be applied in an online measurement system.

  • Partial discharge characterization based on leakage current pulses waveform for contaminated Glass Insulator string
    International Journal of Electrical and Computer Engineering, 2016
    Co-Authors: N. A. Othman, Zuraimy Adzis, M. Afendi M. Piah, Nasir A. Al-geelani
    Abstract:

    This paper deals with the analysis of partial discharge (PD) occurrences based on leakage current (LC) pulses distribution under different level of contamination. In this work, laboratory based contamination performance tests are conducted on four units of Glass Insulator string stacked in I-position. Results show that PD can be characterized (according to their occurrence with respect to the AC supply) as follows: corona discharge occurring dominantly in lightly contaminated Insulators, surface discharge occurring dominantly in medium contaminated Insulators and finally internal discharge occurring dominantly in heavily contaminated Insulators. The ability to distinguish the type of PDs from the LC waveform could be used to monitor and predict the condition of the Insulator. The outcome can be incorporated in a conditioning monitoring system.

  • Leakage current and trapped charge characteristics for Glass Insulator string under contaminated conditions
    2015 IEEE Conference on Energy Conversion (CENCON), 2015
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis
    Abstract:

    This paper reports a study on leakage current (LC) and trapped charge characteristics for contaminated Glass Insulator string. Four units of Glass Insulators recently removed from service were contaminated according to IEC 60507. The measurement of trapped charge distribution was made by a radially shaped stainless steel mesh surrounding each Insulator while LC was measured using 100 Q shunt resistor. The results revealed that as the contamination levels increase, the amplitude of LC increases; but the amplitude of trapped charge decreases.

  • Measurement of surface charge distribution on Glass Insulator using steel mesh
    2014 IEEE International Conference on Power and Energy (PECon), 2014
    Co-Authors: N. A. Othman, M. Afendi M. Piah, Zuraimy Adzis, Hussein Ahmad
    Abstract:

    This paper studies the charge distribution on the transmission line Glass Insulator surfaces under two different ac voltages viz. 28 kV and 33 kV. A string of four Insulator units under dry and clean conditions is taken as the main research object. An attempt to capture the accumulated charge has been made by using radially shaped stainless steel mesh placed axially at a distance of 2 cm from each Glass Insulator circumference. Results show that the distribution of charge across each Glass of Insulator in the string is uneven, and the value of surface charge increases with the increment of applied voltage.