The Experts below are selected from a list of 2799 Experts worldwide ranked by ideXlab platform

He Jin-liang - One of the best experts on this subject based on the ideXlab platform.

  • Prediction of Corona Effects Generated From UHVAC Transmission Lines,II:Radio Interference
    High Voltage Engineering, 2010
    Co-Authors: He Jin-liang
    Abstract:

    Corona effect of 13 bundles was tested in the UHV corona cage,and the radio interference excitation function of each bundle was obtained.Furthermore,effects of surface gradient of Conductor,Diameter of sub-Conductor,split space and split number on the radio interference excitation function were studied in detail.The results show that radio interference excitation function is in linear relation with negative reciprocal of gradient.In the same surface gradient case,radio interference excitation function is in linear increasing relation with Diameter of sub-Conductor and logarithm of split number.However,the influence of split space can be neglected.For analyzing the test data,multi-variant regression method is introduced.The obtained regression equation and its coefficients are verified to be highly significant by test of significance.Finally,methods for predicting radio interference generated from UHV lines are proposed,which are suitable for actual situation of China.

  • Prediction of Corona Effects Generated From UHVAC Transmission Lines,I:Audible Noise
    High Voltage Engineering, 2010
    Co-Authors: He Jin-liang
    Abstract:

    With the increase of voltage level,corona effects and electromagnetic environment issue generated from power line become a critical problem of UHV transmission,and are determinatives for the split type of the UHV bundle.Through the corona performance experiments in the UHV corona cage,audible noise generation quantities of 13 bundles are obtained.Effects of surface gradient of Conductor,Diameter of sub-Conductor,split space,and split number on audible noise are studied in detail.The results show that audible noise is in linear relation with negative reciprocal of gradient.In the same surface gradient case,audible noise is in linear increasing relation with Diameter of sub-Conductor and split number.However,the influence of split space can be neglected.Moreover,multi-variant regression method is suggested to be applied to the statistical analysis of test data.The obtained regression equation and its coefficients are verified to be highly significant.Finally,methods for predicting audible noise generated from UHV lines are proposed,which are suitable for actual situation of China.

T. Hadulla - One of the best experts on this subject based on the ideXlab platform.

  • VORTEX-EXCITED VIBRATIONS IN BUNDLED ConductorS: A MATHEMATICAL MODEL
    Journal of Fluids and Structures, 2002
    Co-Authors: Peter Hagedorn, Nilanjan Mitra, T. Hadulla
    Abstract:

    Wind-excited vibrations generated by vortex shedding are very common in high-voltage overhead transmission lines. Although such vibrations are barely perceptible due to their low amplitudes (less than a Conductor Diameter), they are, however, extremely important since they may lead to Conductor fatigue. Mathematical models are therefore necessary for the computation of these vibrations, in order to evaluate the risk of potential damage to the line as well as for studying the efficiency of damping measures. For single Conductor lines, the socalled energy-balance method gives good results in estimating the vibration amplitudes. However, the problem becomes more involved for bundled Conductors with spacer dampers, commonly used in high-power transmission in many countries, and a modified form of the energy-balance method is presented here. Singular perturbation methods are employed, along with the energetically equivalent standing wave amplitudes obtained from the modified energy-balance methods, to determine the bending strains at critical points. This gives an estimate for the maximum strain levels in a Conductor, which can be very useful in the design of transmission lines and for the optimization of the corresponding damping devices. # 2002 Elsevier Science Ltd. All rights reserved. Of the different mechanical vibration phenomena in high-voltage overhead transmission lines, wind-excited oscillations of the Conductors constitute a major issue. The most common of these wind-excited vibrations are those generated by vortex shedding in the frequency range of approximately 10–60 Hz. Thus, only these are considered in this paper. Although such vibrations are barely perceptible due to their lowamplitudes (less than a Conductor Diameter), they are, however, extremely important since they may lead to Conductor fatigue. Mathematical models are therefore necessary for the computation of these vibrations, in order to evaluate the risk of potential damage to the line as well as for studying the efficiency of damping measures. The energy-balance method is commonly used to estimate the vibration amplitudes of single Conductor lines Hagedorn 1980; Vecchiarelli et al., 1999; a more general overviewon the relevant publications can be found in these references. In the present, paper the method is generalized for the case of bundled Conductors with spacer dampers. The main ideas of the mathematical model for a single Conductor may be briefly described as follows. Consider the schematic representation of a single Conductor line shown in Fig. 1. Since the length of the span is typically of the order of L ¼ 300–500 m, the wavelengths l of the vibrations are of the order of a fewmeters, and the sag only a fewpercent of the span, the sag can be neglected. Thus, the Conductor may be modelled as a taut string with

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

Akifumi Izumi - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation of 6000‐A‐class superconducting field windings for 600‐MW‐class superconducting generators
    Electrical Engineering in Japan, 2007
    Co-Authors: Susumu Maeda, Kenji Shimohata, Itsuo Kodera, Hideaki Sano, Akifumi Izumi
    Abstract:

    Superconducting generators have many advantages such as increasing generator efficiency and improving power system stability. In Japan, a national project has been conducted since 2000 which is aimed at the development of fundamental technologies required for high-output-density and large-capacity superconducting generators. This paper describes the results of this project, focusing on 6000-A-class field winding development. Copyright © 2004 Wiley Periodicals, Inc. A superconducting generator with a high output density and a large capacity has inherent factors that decrease superconducting stability. These are: (1) increase in the magnetic field in the winding which is caused by the increase in winding current density and (2) difficulty in fabricating windings which increases as a Conductor Diameter becomes larger. To secure the stability, we adopted a higher-copper-content Conductor and a design that increases winding fixing pressure, along with devising a winding method that accommodates larger Conductor Diameter. These improvements were applied to a partial model of a 600-MW field winding. Test results of the model showed good stability, indicating that design and fabrication technique for a 6000-A-class superconducting field winding has been successfully evaluated. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 7– 18, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20332

  • Performance Evaluation of a 6,000 A Class Superconducting Field Windings for 600 MW Class Superconducting Generators
    IEEJ Transactions on Power and Energy, 2005
    Co-Authors: Susumu Maeda, Kenji Shimohata, Itsuo Kodera, Hideaki Sano, Akifumi Izumi
    Abstract:

    Superconducting generators have many advantages such as increasing generator efficiency and improving power system stability etc. In Japan, national project has been conducted since 2000 which is aimed at the development of fundamental technologies required for a high output density and a large capacity superconducting generators. This paper describes the results of this project, focusing on a “6,000A-class field winding development".A superconducting generator with a high output density and a large capacity has inherent factors that decrease superconducting stability. These are: 1) increase in the magnetic field in the winding which is caused by the increase in winding current density and 2) difficulty in fabricating windings which increases as Conductor Diameter becomes larger. To secure the stability, we adopted a higher-copper content Conductor and a design that increases winding fixing pressure, along with devising a winding method that accommodates larger Conductor Diameter. These improvements were applied to a partial model of a 600MW field windings. Test results of the model showed a good stability, indicating that design and fabrication technique for a 6,000A-class superconducting field winding has been successfully evaluated.

Peter Hagedorn - One of the best experts on this subject based on the ideXlab platform.

  • VORTEX-EXCITED VIBRATIONS IN BUNDLED ConductorS: A MATHEMATICAL MODEL
    Journal of Fluids and Structures, 2002
    Co-Authors: Peter Hagedorn, Nilanjan Mitra, T. Hadulla
    Abstract:

    Wind-excited vibrations generated by vortex shedding are very common in high-voltage overhead transmission lines. Although such vibrations are barely perceptible due to their low amplitudes (less than a Conductor Diameter), they are, however, extremely important since they may lead to Conductor fatigue. Mathematical models are therefore necessary for the computation of these vibrations, in order to evaluate the risk of potential damage to the line as well as for studying the efficiency of damping measures. For single Conductor lines, the socalled energy-balance method gives good results in estimating the vibration amplitudes. However, the problem becomes more involved for bundled Conductors with spacer dampers, commonly used in high-power transmission in many countries, and a modified form of the energy-balance method is presented here. Singular perturbation methods are employed, along with the energetically equivalent standing wave amplitudes obtained from the modified energy-balance methods, to determine the bending strains at critical points. This gives an estimate for the maximum strain levels in a Conductor, which can be very useful in the design of transmission lines and for the optimization of the corresponding damping devices. # 2002 Elsevier Science Ltd. All rights reserved. Of the different mechanical vibration phenomena in high-voltage overhead transmission lines, wind-excited oscillations of the Conductors constitute a major issue. The most common of these wind-excited vibrations are those generated by vortex shedding in the frequency range of approximately 10–60 Hz. Thus, only these are considered in this paper. Although such vibrations are barely perceptible due to their lowamplitudes (less than a Conductor Diameter), they are, however, extremely important since they may lead to Conductor fatigue. Mathematical models are therefore necessary for the computation of these vibrations, in order to evaluate the risk of potential damage to the line as well as for studying the efficiency of damping measures. The energy-balance method is commonly used to estimate the vibration amplitudes of single Conductor lines Hagedorn 1980; Vecchiarelli et al., 1999; a more general overviewon the relevant publications can be found in these references. In the present, paper the method is generalized for the case of bundled Conductors with spacer dampers. The main ideas of the mathematical model for a single Conductor may be briefly described as follows. Consider the schematic representation of a single Conductor line shown in Fig. 1. Since the length of the span is typically of the order of L ¼ 300–500 m, the wavelengths l of the vibrations are of the order of a fewmeters, and the sag only a fewpercent of the span, the sag can be neglected. Thus, the Conductor may be modelled as a taut string with