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According to our previous experiment, oil flow electrification is closely related to the space charge behaviors in oil-paper insulation system under DC voltage. In this paper, we present a new numerical method to estimate the streaming current in a rectangular paper duct under DC voltage. For the simulation model, we consider the case of laminar flow in a sample of two layers of oil-impregnated-paper...
The mathematical model of the PD process in the lonely inclusion can be described as a series of discharges at the period of the operation voltage. Distribution of the separate discharge times depends on breakdown correlation, extinction and initial condition voltages and the operation voltage. These factors are deterministic as physical phenomena and are stochastic as a result of their influence...
Under high DC voltage, the space charge accumulation can largely alters the local field distribution in epoxy resin. And it has been revealed that nanoparticles have great influences on space charge distribution in epoxy resin. To reveal the mechanism of nanoparticles, the effects of nanoparticles on trap depth are investigated under different temperature. In this work, epoxy resin and its nano composite...
According to our former investigation on space charge properties of two layers of oil-impregnated-paper and oil, the interface charge between oil and paper showed different properties with Maxwell-Wagner theory in which macroscopic conductivity and permittivity were only taken into consideration. It is assumed that the charge barrier existing at interface was responsible for the interfacial charge...
As the temperature difference exists between the inner and outer conductors of high voltage DC cables in practice, it is important to study space charge behavior under temperature gradient. However, due to the effect of temperature on the acoustic propagation, it is necessary to study the waveform recovery method in pulsed electroacoustic (PEA) measurement. In our previous study, only the effects...
Based on the sample of International-trade listed corporations, this paper builds the SFA(Stochastic Frontier Analysis) model and makes an empirical analysis on the technical efficiency of China's foreign trade enterprises. As is indicated in the result, the technical efficiency of China's foreign trade enterprises is extremely low. Besides, ownership structure poses a positive impact on the efficiency,...
Simulation model to investigate the statistical property of electrical breakdown is presented based on the field-assisted percolation model for dielectric breakdown, in which the disorder in morphology is expressed through randomly distributed trap barriers. In addition the effects of sample area and the presence of large defects are evaluated. Assuming that one simulation segment represents an actual...
A two-component composite material is simulated by 8times8times8 cubic cells, containing a spherical inclusion in each of them. A series of produced random numbers are regarded as the radii of these spherical inclusions to simulate the size distribution of inclusions. The finite element method (FEM) is applied to solve the potential distribution and the effective permittivity is calculated by the...
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