Abstract
In this paper, three types of insulators with no crack, short crack, and long crack are taken as the research objects to evaluate the influence of the penetrating cracks on the 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> sheath of the roof silicone rubber composite insulator of high-speed train on the flashover characteristics. The continuous voltage rising method is used to obtain the influence characteristics of the crack on the development process of the flashover arc. The constant voltage withstand method is adopted to compare the leakage current when the contamination degree is 0.1 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The test results demonstrate that the crack has no significant effect on the flashover voltage and flashover path, and the flashover arc can burn the edge of the crack. The peak leakage current of the three different tests ranges from 24 mA to 30 mA. Additionally, the development of leakage current can be divided into four stages: rising, continuous violence, falling, and oscillating. Moreover, the sequence of the apparent leakage current of the insulator is long crack insulator, short crack insulator, and the one with no crack. The acceleration of the rising stage of the leakage current increases with the increase in the crack length. Meanwhile, the sum of the time of the rising stage, continuous stage, and falling stage of the insulator with long crack is the smallest. The crack will distort the distribution of current density and the electric field intensity in the vicinity. The results can provide references for evaluating the influence of radial cracks at the edge of the sheath on the flashover characteristics and optimizing the design of the roof insulator sheath structure.
Highlights
By the end of 2020, the mileage of China's high-speed railways has reached 37,900 km
According to the results of constant voltage withstand and continuous voltage rising tests, the influence of cracks on the flashover characteristics of train roof insulators is analyzed in this paper from three perspectives of the arc development process, dry zone location, and leakage current change trend
(1) The results of the continuous voltage rising flashover test demonstrate that the existence of cracks has no significant effect on the flashover voltage and the location of the dry zone, and the flashover voltage is higher than 60 kV
Summary
By the end of 2020, the mileage of China's high-speed railways has reached 37,900 km. J. Ma et al.: Influence of Sheath Radial Crack on Flashover Arc and Leakage Current of Roof Silicon Rubber Insulator for High-Speed Train (a). The research results of Tsinghua University Zhidong Jia et al on the crescentshaped cracks of insulators reveal that the root thickness of transmission line insulator sheath is small, and the soft and high-elastic silicone rubber could decrease the mechanical strength after the reciprocating deflection by the action of airflow. The soft silicone rubber composite insulator on the roof is taken as the research object to evaluate the influence of the cracks at the edge and the intermediate part of the sheath on the insulation characteristics. Regarding three types of insulators (normal, short crack, and long crack), the withstand method is employed to reveal the influence of cracks on the flashover voltage and collect the leakage current changes on the surface of the sheath under non-arc operation. After the thickness of the crack root is deducted, the leakage distance of the 1st sheath of the cracked insulator decreases by about 40 mm compared with the intact insulator
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