摘要 :
There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydrat...
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There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydration effects of a lightning impulse, which may have implications for the effects in flora and fauna. A specific instance is the current hypothesis that trees that explode may do so due to the rapid vaporization of the trees fluids. An understanding of the dehydration effects of lightning impulses in general will offer insight into the possibility of this occurring as well as many other systems where dehydration is applicable. This paper details an investigation into a method of measuring and quantifying the dehydration effects of a lightning impulse and the challenges faced in its development.
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摘要 :
Characteristics of coaxial resistive attenuators of digital instrument for the standard full lightning impulse(LI) measurement are studied. The amplitude - frequency characteristics and the input impedance of two kinds of attenuat...
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Characteristics of coaxial resistive attenuators of digital instrument for the standard full lightning impulse(LI) measurement are studied. The amplitude - frequency characteristics and the input impedance of two kinds of attenuators are analyzed. An approach to evaluation the scale factor of peak voltage for the attenuators are introduced based on the comparison of the peak of the impulse output by a standard lightning impulse generator to that of a standard square wave with rise time of 1.4(mu)s at voltage level of 100V, and the measurement uncertainty of the scale factor for peak value is less than 0.5percent(k(velence)2).
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This paper presents a vertical grounding mesh to transmission line (TL) towers for use in two-layered soils, where the second-layer has a lower resistivity compared to the first. To a better knowing about its behavior, a compariso...
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This paper presents a vertical grounding mesh to transmission line (TL) towers for use in two-layered soils, where the second-layer has a lower resistivity compared to the first. To a better knowing about its behavior, a comparison with horizontal arrangement composed by counterpoise cables, for critical soils from a 230 kV TL, is realized focusing in impulse coefficient parameter. A first analysis of the procedure based on TL-theory with electromagnetic (EM) method is made and an evaluation of homogenous soil for the arrangements is realized. The results indicate a lower grounding resistance and impulsive impedance for the proposed vertical option compared to horizontal arrangement, using much less conductor material and presenting a margin to reduce such parameters due to the distance to effective length.
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摘要 :
There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydrat...
展开
There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydration effects of a lightning impulse, which may have implications for the effects in flora and fauna. A specific instance is the current hypothesis that trees that explode may do so due to the rapid vaporization of the trees fluids. An understanding of the dehydration effects of lightning impulses in general will offer insight into the possibility of this occurring as well as many other systems where dehydration is applicable. This paper details an investigation into a method of measuring and quantifying the dehydration effects of a lightning impulse and the challenges faced in its development.
收起
摘要 :
There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydrat...
展开
There are many aspects of lightning that are not yet understood; indeed many of the aspects of lightning that were believed to be understood have recently seen evolution due to new information. One of these aspects is the dehydration effects of a lightning impulse, which may have implications for the effects in flora and fauna. A specific instance is the current hypothesis that trees that explode may do so due to the rapid vaporization of the trees fluids. An understanding of the dehydration effects of lightning impulses in general will offer insight into the possibility of this occurring as well as many other systems where dehydration is applicable. This paper details an investigation into a method of measuring and quantifying the dehydration effects of a lightning impulse and the challenges faced in its development.
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摘要 :
This paper focuses on the use of dielectric properties of human tissues in analysing injuries as a result of the lighting short stroke current. The lightning short stroke current is decomposed into its frequency components and the...
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This paper focuses on the use of dielectric properties of human tissues in analysing injuries as a result of the lighting short stroke current. The lightning short stroke current is decomposed into its frequency components and the effects of these frequency components on human tissues are analysed. The dielectric properties of nineteen types of human body tissues are examined and the correlations between the impedances of these tissues and the lightning stroke current pathway are investigated. The human tissues are modelled as cylindrical structures using a FEA (Finite Element Analysis) approach and simulated using the COMSOL Multiphysics software suite. The results obtained from the simulations include: current density, complex impedance and total absorbed power of the tissues. Only the first short stroke of the lightning flash is considered as the test parameter. The direct strike mechanism of lightning injury is examined in this paper with the possibility of including other mechanisms of lightning injury in the future. The first short stroke of the lightning flash is modelled using a double exponential model and exhibit a 4 kA 1.8/30μs waveform. This waveform consists of frequencies up to 100 kHz. The skin and bone marrow is found to have the most varying impedances within this frequency range and the heart is found to be the organ with the least impedance. The results from the simulations depict physical properties of real human tissues and hence are valid in the analyses of lightning injuries.
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In this paper, a new approach based on particle swarm optimization (PSO) algorithm is used to evaluate the single-stage impulse generator (SSIG) circuit parameters (R_1, R_2, C_1, and C_2) from the known values of rise and tail ti...
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In this paper, a new approach based on particle swarm optimization (PSO) algorithm is used to evaluate the single-stage impulse generator (SSIG) circuit parameters (R_1, R_2, C_1, and C_2) from the known values of rise and tail times. The results reported in this paper provide the standard lightning impulse (LI) signals which meticulously matches with those waveforms illustrated in the IEEE 4-2013, and IEC-62305-1,2010 standards. This is the first of its kind attempt to use PSO as a tool to evaluate the SSIG circuit parameters. This approach helps to overcome the practice of conventional trial and error methods for finding the impulse circuit parameters. These results are verified by the impulse circuit developed in MATLAB.
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摘要 :
In this paper, a new approach based on particle swarm optimization (PSO) algorithm is used to evaluate the single-stage impulse generator (SSIG) circuit parameters (R_1, R_2, C_1, and C_2) from the known values of rise and tail ti...
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In this paper, a new approach based on particle swarm optimization (PSO) algorithm is used to evaluate the single-stage impulse generator (SSIG) circuit parameters (R_1, R_2, C_1, and C_2) from the known values of rise and tail times. The results reported in this paper provide the standard lightning impulse (LI) signals which meticulously matches with those waveforms illustrated in the IEEE 4-2013, and IEC-62305-1,2010 standards. This is the first of its kind attempt to use PSO as a tool to evaluate the SSIG circuit parameters. This approach helps to overcome the practice of conventional trial and error methods for finding the impulse circuit parameters. These results are verified by the impulse circuit developed in MATLAB.
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This paper presents a more economically advantageous method of obtaining high amplitude current impulses having a high voltage generator (GIT) as a power source. This method consists in the realization of a current impulse testing...
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This paper presents a more economically advantageous method of obtaining high amplitude current impulses having a high voltage generator (GIT) as a power source. This method consists in the realization of a current impulse testing system for high voltage equipment. To obtain impulse currents with GIT, they were introduced into the circuit of the LC pulse delay cell circuit. A current impulse generator (GIC) circuit has been developed to meet current standards. This system has enabled new test methods to be developed and improved equipment developed. The methods and procedures can be applied to extend the fields of research by using current impulses to determine the dynamic and thermal stability of the electrotechnical and electroenergetic equipment, as well as the functional stability of the electronic devices in electromagnetically disturbed environments.
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This paper presents the design and construction of measuring systems for recording lightning surge voltage in a 230 kV overhead lines. The measuring systems consist of high voltage divider and low voltage impulse recorder. The hig...
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This paper presents the design and construction of measuring systems for recording lightning surge voltage in a 230 kV overhead lines. The measuring systems consist of high voltage divider and low voltage impulse recorder. The high voltage divider was designed as a damped capacitor voltage divider having the voltage ratio of 1318. The constructed divider was tested for BIL and AC withstand in accordance with IEC No. 71. The surge voltage on the low voltage side of the voltage divider was measured and recorded by means of remote surge detector and surge recorder, which was designed by using Field Programmable Gate Rays (FPGA) and computer technology. The characteristics of the measuring system was tested in accordance with IEC No. 60-2. The reliability of the measuring system was checked in the high voltage laboratory by applying the lightning impulse voltage superimposed on AC 50 Hz voltage. The designed and constructed measuring system has been installed in the 230 kV substation for 15 months. The waveform and amplitude of lightning surge voltage were recorded. The measured results are illustrated and discussed.
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