Tao Yao

China Electric Power Research Institute, Peping, Beijing, China

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Publications (7)2.24 Total impact

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    ABSTRACT: The results of a laboratory study on the electrical performance of 1000kV and 500kV post insulators as well as 500kV bushing covered with wet-grown ice were presented in this paper. The tests were performed in a large-scale artificial climate chamber at UHVAC test base of State Grid Corporation of China (SGCC). The ice formed artificially by super cooled water droplets accreted on the energized insulators under an air temperature of -10°C. The 50% flashover voltages and the leakage current were obtained by tests on polluted insulators during ice melting regime. The influence of salt deposit density (SDD) and the average diameter of the insulators to the flashover performance were discussed. The results show that the 50% flashover voltage is decreased with the increasing of SDD, which follows the law of negative power exponent. And a larger diameter of insulator corresponds to a larger icing area when the icing condition is the same, which result a smaller resistance on the surface of the insulator. Therefore, in a fixed SDD, the 50% flashover voltage also decreased with the increasing of the average diameter, but the leakage current before flashover is larger, which can be explained by ohms law.
    No preview · Conference Paper · Oct 2014
  • Zuoming Xu · Tao Xu · Wei Hu · Tao Yao · Xiaodong Wan
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    ABSTRACT: To simulate the special state of ice-covered insulators, the traditional circuit model for insulators flashover was improved by considering the influence of air gaps. Take the energy varying accompany the ice-melting and water vapor into account, Cassie and Mayr differential equations were combined to describe the arc resistance. Based on the dynamic equations of arc resistance and residual ice-layer resistance, the dynamic flashover model of ice-covered insulators was set up. The measured voltage and current on the ice-covered insulators when flashover occurred were approximated as the arc voltage and arc current, which supplied base date to calculated the model parameters using nonlinear least squares method. Thus, the dynamic variations of arc voltage and current from arc generated to flashover on the ice-covered insulators can be simulated. The simulation results have been compared with the experimental results, which validate the presented dynamic flashover model.
    No preview · Conference Paper · Oct 2013
  • Jing Nan · Xiaodong Wan · Tao Xu · Tao Yao · Qin Liu
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    ABSTRACT: The discharge performance of air-gap and insulator string at high altitude regions is different from that of the referring standard conditions as the relative air density decreases with the increasing of altitude. This difference is one of the key question in engineering design of the external insulation. Since the leakage currents of contaminated insulators comprised a large number of noises before partial discharging, it was very difficult to obtain the valid characteristics of signals, especially under high altitude. For the purpose of obtaining surface discharge voltage and its correction in different altitudes, typical proclaim insulator was selected, and comparative experiments were conducted under different altitudes from 0m to 4000m in environmental climate laboratory. The leakage currents of porcelain is monitored and analyzed in various pollution conditions. The results are useful for the pre-warning of the contamination flashover under high altitude conditions. This study provide essential technical support for designing outdoor insulators of power systems in high-altitude regions.
    No preview · Conference Paper · Oct 2013
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    ABSTRACT: The test results show that icing flashover voltages of 28-unit porcelain suspension insulators and composite insulators are, respectively, 20.5 and 18.7% lower than the rated operating voltage under the contamination level of ρESDD/ρNSDD (equivalent salt deposit density/non-soluble deposit density) = 0.1/0.5 mg/cm and severe icing conditions. When using alternate-diameter insulators in the same contamination level, the results are 21.2% higher than the rated operating voltage under moderate icing conditions, but 15.7% lower under severe icing conditions. For the same time period of icing, the maximum withstand voltages (the prospective value of the test voltage that the equipment is capable of withstanding when tested under specified conditions) of V-strings are 30% higher than the rated operating voltage under ρESDD/ρNSDD = 0.1/0.5mg/cm, which have a much better icing flashover performance than the suspension insulator strings. Moreover, the discharge processes of standard insulator string and alternate-diameter insulator string were comparatively analyzed. A large number of air gaps present on the latter ones could be the reason for a better icing flashover performance than standard ones. But severe icing conditions can shorten the width of the air gaps and decrease the flashover voltage greatly.
    No preview · Article · Mar 2012 · Journal of Adhesion Science and Technology
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    ABSTRACT: The icing flashover characteristics and discharge processes of 500 kV ac transmission line long insulator strings energized in the ice accretion were studied. The influence of pollution and grading rings (including simulated conductor) on heavy ice-covered insulators¿ flashover voltage were considered in this paper. Based on the artificial icing test results, it was found that 1) under the severe icing conditions and three salt deposit density (SDD) levels of P<sub>SDD</sub>=0.1, 0.05, 0.025 mg/cm<sup>2</sup>, compared with 500 kV transmission line rated phase to ground voltage, the flashover voltages of 28 units XWP2-160 porcelain double-shed insulator are 20.5% lower, 13.1% lower and 2.3% higher respectively; and the values of the FXBW<sub>4-</sub>500/160 composite insulator are 18.7% lower, 12.0% lower and 4.3% higher respectively. 2) equipped with the given grading ring and simulated conductor the icing flashover stress of 28 units XWP<sub>2-</sub>160 is lower than those without grading ring and simulated conductor under the three pollution degrees. The discharge process of the icing flashover and relevant factors were investigated also, which shows that 1) the locations of the air gaps on icing insulators are not completely random. 2) arcs on long insulator strings require more time to reach a critical length, hence, the arc propagation might be easily influenced by the decreasing of melted water conductivity and ice shedding than short insulator strings.
    No preview · Article · May 2010 · IEEE Transactions on Dielectrics and Electrical Insulation
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    ABSTRACT: In the present paper, study on icing flashover characteristics were carried out in artificial climate chamber of State Grid Electric Power Research Institute (SGEPRI) with XWP2-160 porcelain double sheds suspension insulators. According to IEEE Task Force on insulator icing test methods the natural freezing rain condition was simulated and 3 to 7 units XWP2-160 insulators were icing energized at service voltage. Based on the tests results, the U50% increases with an increase in dry arcing distance linearly for XWP2-160 not more than 7 units. The effect on icing flashover performance of the factors such as ice thickness and applied water conductivity were investigated respectively. More over, ice states and discharge process of insulators icing energized were compared with the de-energized ones and discussed. For the air gaps can enhance the electrical strength of iced insulators, the U50% withstand voltage of insulators icing energized is higher than the de-energized ones.
    No preview · Article · Jul 2009
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    ABSTRACT: The flashover process during ice-melting period of polluted and ice-covered insulator string was studied by experiment in this paper. Arc development, evolution of leakage current and its frequency representation (FFT) were analyzed. The results indicated that the flashover process can be divided into five stages, named initial stage, intermittence local arc stage, arc propagation stage, critical flashover stage and flashover stage. Each stage has distinct discharge phenomenon and a fixed level of leakage current peak value. Both the nonlinearity and the phase angle difference between leakage current and the applied voltage decrease with the raising of leakage current. At the initial stage, the leakage current peak value is less than 10 mA and hardly has any harmonic content. When the arc is intermittent, the harmonic content of the leakage current is the largest. The leakage current waveform is smooth and has fewer harmonics at critical flashover stage.
    No preview · Article · Jan 2009

Publication Stats

25 Citations
2.24 Total Impact Points


  • 2014
    • China Electric Power Research Institute
      Peping, Beijing, China
  • 2013
    • Electric Power Research Institute
      Palo Alto, California, United States
  • 2009-2012
    • State Grid Electric Power Research Institute
      Nan-ching-hsü, Jiangxi Sheng, China