Composite insulators can take wind and rain and have good self-cleaning performance under wind and rain, so need checking for pollution only once every 4–5 years, and requiring less time for the repair and power interruption. Since the core rod has higher extension strength, composite insulators can result in very light overall weight. Their weight is only 10–20% of the weight of porcelain insulator strings of the same voltage class. Their length can be shortened by more or less 10% in the same voltage class, which can greatly reduce the labor of workers in transportation and field operation.
The composite insulator has many advantages, but also disadvantages, e.g., the loss of hydrophobicity, the risk of the core rod becoming brittle and breaking, lightning strike and birds droppings, which can all make composite insulators lose efficiency.
Since the diameter of the sheds of the composite insulator is less, the minimum electric arc distance is less than for the same length of porcelain insulator strings, and the lightning withstand level is also less than for the same length of porcelain insulator strings
After a lightning strike, the only effect on composite insulators is some white electric erosion; there is no change in their insulating property. But attention must be paid to the erosion of both ends of the fitting.
The internal insulation distance of composite insulators is nearly equal to that of the external insulation, and the structure is in the group of puncture-proof insulators, and therefore does not have the problem of having to detect zero value insulators, and this greatly reduces the workload of operation maintenance.
The material of sheds and sheaths of composite insulators are silicone rubber and the surface is a low energy surface. The creepage distance of composite insulators is bigger and the diameter of the umbrella shed is smaller, and the surface has hydrophobicity and migration of hydrophobicity. Even in a humid and polluted environment, the shed surface of composite insulators will not form a continuous water film; therefore, its antipollution performance is superior to that of a porcelain insulator.
The main component of the composite insulator is a silicone rubber sheath. Silicone rubber is formed by the linkage of high-molecule polymers of polydimethyl siloxane and organic oxygen compounds; the main chain is formed by a silicon oxygen bond. Since the bond energy of the silicon oxygen bond is larger it has good thermostability, and can work at temperatures of −100 to +350°C. Silicon rubber has good ozone resistance performance, and whereas butadiene-propylene propylene butadiene rubber can be readily broken, under room temperature tension on ozone of 150 ppm, however, silicone rubber can last for several months and not be broken.