Xinlao Wei

Harbin University of Science and Technology, Charbin, Heilongjiang Sheng, China

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Publications (14)0 Total impact

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    ABSTRACT: Taken a composited insulation system of oil and pressboard filled in two parallel tabulate electrodes as research object, the oil-flow electrification experiment was carried out without applied voltage and under DC voltage. The relationship between leakage current and velocity was measured. The electric­ field caused by oil-flow electrification was calculated. The breakdown characteristics experiment of the composited insulation system was carried out at different velocity, stressed by AC voltage, DC voltage and AC plus DC voltages with different AC voltage content. The result shows that, as the velocity increases, the breakdown voltage of the oil-pressboard composited insulation system may decrease and the electric-field caused by oil-flow electrification may increase. The oil-flow electrification will increase under DC electrification than that without applied voltage.
    01/2011;
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    ABSTRACT: to investigate the effect of DC electric field on streaming electrification in converter transformer, an oil/paper tube model with concentric cylindrical electrode geometry was built and the flow electrification under the DC electric field was investigated in laboratory. The results demonstrated that the energization by positive DC voltage can enhance the streaming electrification especially at high temperature. With the increment of temperature, the streaming current first increases and reaches a peak value, and then decreases at higher temperature. The flow velocity has a little effect on the streaming current in the low temperature region. However, in the high temperature region the increase of flow velocity greatly enhances the electrification. Furthermore, ion migration is the main reason that causes the flow electrification under the DC electric field.
    01/2011;
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    ABSTRACT: It is reported that bacteria suspended in solution were inactivated by the pulsed electric field (PEF) process using coaxial treatment chamber and tube-plate treatment chamber. The bacteria inactivation effects in slightly non-uniform electric field and highly non-uniform electric field are studied in this paper. The samples, treated in the two treatment chambers, are subjected to the same flow rate and the same pulses number. Their inactivation effects are compared. Experimental result shows that the tube-plate treatment chamber is more effective than the coaxial treatment chamber.
    Properties and Applications of Dielectric Materials, 2009. ICPADM 2009. IEEE 9th International Conference on the; 08/2009
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    ABSTRACT: In HVDC transmission systems, the oil and oil-impregnated pressboard insulation of converter transformers is subjected to composite AC and DC voltage. Therefore, a study on breakdown characteristics of this insulation under AC, DC and composite AC and DC voltage is essential. In this paper, breakdown tests on transformer oil and oil-impregnated pressboard insulation under all kinds of those voltages have been completed and the relationship between breakdown peak voltage and AC ratio is discussed. It is shown that the breakdown field strength of transformer oil decreases with the increases of oil gap under any waveform. Breakdown peak voltage of a given oil gap has little change with the variation of AC ratio, but evident inflection point occurs in their relation curve. Breakdown peak voltage of a given oil-impregnated pressboard decreases remarkably with the increases of AC ratio.
    01/2009;
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    ABSTRACT: A new measuring system of dielectric loss factor (tandelta) with TMS320F2812 DSP for high voltage capacitive apparatus is presented in this paper. By using harmonic analysis method for measuring phase difference, the quasi-synchronous algorithm and measurement error adaptive corrected with DSP is adopted. Test results show that the measuring system based on DSP has higher precision, stability and anti-interference reliability.
    01/2009;
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    ABSTRACT: This article analyzes the different types of voltage applied on the valve side winding of the converter transformer. The oil-paper insulation model is established in laboratory in order to analyze the distribution characteristics of electrical field caused by the voltage applied on the insulation. The distribution of the fields caused by DC voltage, AC voltage, DC superimposed voltage and polarity reversal voltage is emulated with FEM (finite element method). It can be concluded from the results that the resistive distributed electrical field caused by DC voltage will lead to high field intensity in the pressboard. The capacitive distributed electrical field caused by AC voltage will lead to high field intensity in the oil. Influenced by the space charge field, the oil withstands most of the applied voltage in the stage of polarity reversal. The results can provide evidence for the insulation design of the converter transformer.
    01/2009;
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    ABSTRACT: This paper deduced the relationship of transmembrane voltage on cell membrane and frequency by solving the Laplace's equation. The value of transmembrane voltage will decrease when the frequency of outer electric field increases, and this decrease will be faster if the frequency exceeds a certain frequency band. The transmembrane voltage is determined by frequency components contained in the pulse on the condition of the electric field intensity is fixed when a pulsed electric field is applied. The more low-frequency components contained, the larger transmembrane voltage is, and thus a better sterilization effect can be obtained. By comparing the frequency components contained in the three types of pulses mostly used in PEF and their sterilization effect respectively, the analysis of relationship of transmembrane voltage-frequency is validated.
    Properties and Applications of Dielectric Materials, 2009. ICPADM 2009. IEEE 9th International Conference on the; 01/2009
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    ABSTRACT: In this paper, traveling wave fault location equipment for power cables is designed, and the characteristic waveforms of cable fault point broken down and not broken down are simulated respectively. Then a new traveling wave fault location method based on wavelet transform is presented. Wavelet transform have good performance in denoising and singularity detection, which well solved the difficulty in identifying the initial point of the reflected traveling wave because of the local time-frequency characteristic. The fault distance can be calculated by the round-trip times which the traveling wave spends in the cable. The only required parameter is the length of cable. With the method, the result of fault location is not influenced by the change of propagation velocity of traveling wave. The correctness and effectiveness of this method are analyzed by computer simulation. The obtained results show an acceptable degree of accuracy for fault location.
    Mechatronics and Automation, 2007. ICMA 2007. International Conference on; 09/2007
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    ABSTRACT: Very fast transient overvoltages (VFTO) might result from flashover of the particle-contaminated spacer in gas-insulated switchgear (GIS). To get a better understanding of the effects of voltage wavefront steepness and oscillation frequency on the flashover voltage, experiments were carried out on a simple cylindrical spacer with a metallic protrusion under different voltage waveforms. The results show that the flashover voltage-time (V-t) characteristics are dependent on oscillation frequency and rise time of impulses. The space charge accumulation produced by corona discharge of the metallic particle on the spacer is the main reason that causes the insulation failure of GIS.
    Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
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    ABSTRACT: Luminous signals emitted during predischarge and the breakdown over the spacer in SF6 was investigated by using a photomultiplier tube under Fast Oscillating Impulse (FOI) and Lightning Impulse (LI). The results show that the waveform and polarity have a prominent effect on the luminous characteristics. A single luminous pulse could appear at LI wave front, but under the FOI, the continuous and periodic luminous signal was found. With a spacer contaminated by a metallic particle, the luminous amplitude appeared at wave crest was different from those at wave trough. So the space charge would accumulate on the spacer surface in favor of the leader formation leading to low flashover voltages. It also found that the SF6 gas pressure had different effects on initial predischarge voltages depending on the voltage shapes and polarities.
    Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
  • Qi Wei, Xinlao Wei, Hongzhang Jin
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    ABSTRACT: Brittleness as a characteristic of complex system has been presented. Complex system is chosen as the research object, which is characterized not only by openness, complexity, giant, evolution and emergence, hierarchy but also by brittleness. Moreover, it is existent objectively as the basic characteristic of complex system. Based on the definition, peculiarities, and models of brittleness, theories about brittleness of complex system have been established. In this paper, analysis has been carried out on the SARS based on the theory of brittleness. The results of simulation show that brittle entropy increase and brittle entropy of subsystems tend to ascend at the beginning of SARS interference. After the subsystems obtain the negative entropy from the environment, the entropy will be decreased. Understanding its internal brittle mechanism and adopting effective methods are the key factors of controlling the spread of SARS
    Intelligent Control and Automation, 2006. WCICA 2006. The Sixth World Congress on; 01/2006
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    ABSTRACT: In recent years, the ultra high frequency (UHF) method is employed to reduce and avoid the noises effects on partial discharge (PD) detection for the power transformer on-site. In order to know the UHF signal radiation from the partial discharge in oil impregnated insulation and its propagation characteristics in a transformer tank, the experiments have been carried out in high voltage laboratory. The current impulse waveforms of PD and its UHF signals are measured through the partial discharge detecting circuit and a coupler, respectively. The results show that the electromagnetic wave can be excited from the partial discharge in oil-impregnated insulation with the higher frequency than that in air. The propagation and attenuation characteristics of UHF signals in a metal tank are different from that in opening air. The experimental results also show that the UHF signal can be radiated from the inside of a metal tank through a wire, which makes it possible to measure partial discharge for the power transformer with the coupler fixed at the outside of the tank.
    Electrical Insulating Materials, 2005. (ISEIM 2005). Proceedings of 2005 International Symposium on; 07/2005
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    ABSTRACT: The paper introduces the measurement of tan δ with a quasi-synchronous sampling harmonic analysis method firstly. The principle and the algorithm for harmonic analyzing under the condition of quasi-synchronous sample are described. It is shown, through an analysis about many influencing facts, that this method has high precision and good anti-disturbance characteristics, but the precision of this method is influenced by the methods of signal pick-up. The paper analyses the influence of different methods of signal pick-up on the precision of measurement.
    Properties and Applications of Dielectric Materials, 2003. Proceedings of the 7th International Conference on; 07/2003
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    ABSTRACT: Very fast transient overvoltages (VFTO) generated during disconnecters operation in GIS might cause insulation failure inside or outside GIS. Hence, the breakdown characteristics of GIS stressed by VFTO were studied, and the photoelectric measurements were carried out to investigate the discharge behavior stressed by VFTO or LI. The results show that the space charge accumulation produced by corona discharge of the metallic particle on the spacer is the main reason that causes the insulation failure of GIS
    Properties and Applications of Dielectric Materials, 2000. Proceedings of the 6th International Conference on; 02/2000