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Why does the composite insulator appear flashover
Sep 04, 2018

Under normal power frequency voltage, especially in high temperature and high humidity weather or contaminated HTV silicone rubber composite insulator flashover may operate, and the discharge mechanism of hydrophobic composite insulator is different from the hydrophilicity of porcelain and glass insulator. When the same creepage distance and water repellency are good, the effective creepage distance of the composite insulator is larger than the effective creepage distance of the porcelain insulator and the glass insulator. When the composite insulator is reduced to above HC5, its effective creepage distance can be less than that of porcelain and glass insulators. HTV silicone rubber umbrellas have a hidden danger, and the flashover of composite insulators has been operating for several years.

 The hydrophobicity of HTV silicone rubber can reduce the humidity of composite insulators by 10% and 30%, and the working frequency pollution withstand voltage is reduced by 30%~40%. The significant drop of power frequency intensity is also one of the reasons for flashover. If the hydrophobic part or total loss, the diameter of the disc, the umbrella distance is small, under high humidity atmospheric conditions, a short arc canopy is easily generated and the electric strength is lowered. This is one of the main reasons for the flashover of composite insulators, which should be paid enough attention by the production enterprises and operating departments.

The 220 kV line is not installed in the high pressure balance device at the end of the composite insulator. When the installation pressure equalization device or the high and low pressure side pressure equalization device is installed separately, the skirts of the potential distribution on the high voltage side account for 17.2%, 12.4% and 10.1% respectively. The operating voltage and the installation of the balancing device greatly reduce the voltage at the connection point on the high voltage side, so that the power frequency electrical performance is greatly improved.

A circular rear balance device with a protective layer thickness of 40 mm and 75 mm, a second skirt with a potential distribution of operating voltages of 21.3% and 12.2% on the high voltage side, and a potential distribution curve of 75 mm, respectively The potential distribution curve of the insulator with a depth of 40 mm than the insulator is more uniform, and the depth of the equalization device covering the impact potential distribution is large. When the equalization device is installed, the high voltage distribution of the potential on the insulator accounts for 19% of the operating voltage, which is 1.8% higher than that of the unbalanced device. This indicates that the correct installation of the equalization device has a great influence on the electrical performance of the composite insulator.

The shape of the skirt is optimized according to the aerodynamic principle and external insulation. The umbrella is two large umbrella discs with a diameter of 200-250 mm, and the large pitch umbrella is 130-150 mm. This improves the effective creepage distance of the unit umbrella and also greatly reduces the power frequency flashover voltage of the silicone rubber insulator under high humidity environment. During normal operation, ie under high humidity conditions, the hydrophobic composite insulator is reduced in hydrophobicity to a level of porcelain and glass insulators. It is equivalent to the operation of the XP 160 disc type suspension porcelain and glass insulators.

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