Under normal power frequency voltage, especially in high temperature and humidity weather or polluted HTV silicone rubber composite insulators, flashover may occur, and the discharge mechanism of hydrophobic composite insulators is different from the hydrophilicity of porcelain and glass insulators. When the same creepage distance and hydrophobicity are good, the effective creepage distance of composite insulators is larger than that of porcelain insulators and glass insulators. When the hydrophobicity of composite insulators drops to above HC5, their effective creepage distance can be smaller than that of porcelain and glass insulators. The hidden danger of HTV silicone rubber umbrella deterioration and the flashover of composite insulators after several years of operation.

The hydrophobicity of HTV silicone rubber can reduce the humidity of composite insulators by 10% and 30%, and the operating frequency pollution tolerance voltage can be reduced by 30% to 40%. The significant decrease in power frequency intensity is also one of the reasons for flashover. If the hydrophobic part or total loss is small, the diameter of the disc and the umbrella distance are small, and under high humidity atmospheric conditions, it is easy to have a short arc in the rain shelter and reduce the electrical intensity. This is one of the main causes of composite insulator flashover and should be given sufficient attention by production enterprises and operating departments.

The 220 kV transmission line does not have a high pressure balancing device installed at the end of the composite insulator. When installing the balancing device or the high and low voltage side balancing devices respectively, the umbrella skirt of the potential distribution on the high voltage side accounts for 17.2%, 12.4%, and 10.1% of the operating voltage, respectively. The installation of the balancing device greatly reduces the voltage at the attachment connection point on the high voltage side, greatly improving its power frequency electrical performance.

Install circular post balancing devices with protective layer thicknesses of 40mm and 75mm respectively. On the high voltage side, the second umbrella skirt with a potential distribution of 21.3% and 12.2% of the operating voltage, and the depth of the 75mm potential distribution curve are more uniform than those of insulators with insulation coverage depth of 40mm. The depth of coverage on the impulse potential distribution balancing device is larger. When the balancing device is installed, the high voltage distribution on the insulator accounts for 19% of the operating voltage, which is 1.8% higher than that without the balancing device installed, indicating that the correct installation of the balancing device has a significant impact on the electrical performance of composite insulators.

Optimize the skirt shape based on pneumatic principles and external insulation. Umbrellas have two large umbrella discs with a diameter of 200-250 millimeters and a spacing of 130-150 millimeters. This increases the effective creepage distance per unit umbrella and greatly reduces the power frequency flashover voltage of silicone rubber insulators. During normal operation under high humidity conditions, the hydrophobicity of hydrophobic composite insulators decreases to a certain level for porcelain and glass insulators. It is equivalent to the operation of XP 160 disc type suspension porcelain and glass insulators.