| As the key part of high-speed train, the insulating property of roof insulator is one of the vital considerations to ensure the safe operation. The operating environment of roof insulator is complex and variable. The harsh operating condition, the bad weather and the severe contamination cause flashover frequently. In order to guarante safe and stable operation of high-speed train, this paper presents three aspects of study:the distribution feature of typical contamination along the railway and insulator surface contamination were investigated, the effective characteristic quantities of insulator contamination status were established and the resistance to tracking performance of epoxy roof insulator was analyzed, which have provided theoretical foundation to avoid flashover.ESDD value method and NSDD value method were used to analyze the typical contamination component characteristics of three kinds of railway nearby cement plant, tunnel, and kerosene serious strip. The contaminated extent of insulator on three positions is "very serious". The insulator contamination near cement plant has the feature of high NEDD value. The insulator contamination has feature of high ESDD and NSDD value. However, in the kerosene serious strip, to insulator contamination, ESDD value is great high, but low NSDD value. The small spray chamber was used to simulate the effect of fog and humidity on roof insulator. The three kinds of natural contamination fog have small effect on ESDD value but have huge effect on NSDD value. In terms of ESDD and NSDD value, intermediate position is slightly above the ends of sheds, and the upper surface is above the lower surface of sheds. To the contamination transverse distribution of roof insulator surface, ESDD and NSDD value are high on the windward and leeward, and is low on the crosswind face.The impedance characteristics, leakage current and critical flashover voltage of different insulator contamination distribution were measured and analyzed. The leakage current along surface increases with rising of the degree of the insulator surface contamination. The range of critical flashover voltage thresholds are approximate 12.5kV～27.5kV,9kV～27.kV,6kV～27.5kV in condition of humidity of 60%～75%, 75%～85%,85%～95%. Under the same impedance magnitude, with the degree of the contamination level increasing, the impedance angle decreases. As the impedance angle is a constant, contamination impedance magnitude declines with the contamination level increasing.The three-dimensional nonlinear transient thermal-electric coupled field model of epoxy insulator producing electric tracking and occurring discharge along surface were established by ANSYS. With minimum tracking conditions, the maximum temperature of the shield surface is higher than upper surface and shed lower surface of shed and the maximum temperature 1218.9K is on the first shield surface. Impacts of tracking on insulator surface insulation are that shield surface is higher than the upper surface of shed and the upper surface of sheds is higher than the lower surface of shed. The temperature distribution and resistance of tracking capabilities were analyzed when the insulator flashovers. With minimum tracking conditions, the maximum temperature 2072K appeared at the first and last sheds edge position. Sheds edge position was easiest tracked, but on the sheds root temperature is lowest and difficultly tracked. The degree of tracking has a nonlinear relationship with time. The eroded depth increases with time linearly. However, the relationship of eroded width and time could be represented by double exponential function. |
PDF Full Text Request