Mechanical strength
Pure silicone rubber has a small mechanical strength, and generally uses white carbon black as a reinforcing filler, which can significantly improve the strength of the insulator. Because of the small size and large specific surface area of the silica particles, it can interact strongly with the silicone molecules to improve the interface condition. At the same time, the surface of the silica contains many hydroxyl groups, and the particles can form a network through hydrogen bonding and van der Waals forces. structure. The surface area and the average particle size of the silica are within an appropriate range to achieve an optimum performance of the silicone rubber. The composite insulator core rod has a tensile strength of up to 7000 MPa and a specific strength five times that of high quality carbon steel. Some regions and departments have proposed the use of synthetic insulators, and the mechanical strength is one level higher than that of traditional porcelain and glass insulators. If the porcelain insulator is used, it is l60kN, and the composite insulator is 210kN. Actually. When the load is less than 40% of the rated mechanical load, the reliability of the operation can be guaranteed. Therefore, synthetic insulators can be selected in accordance with the method of porcelain insulators without having to increase the mechanical allowable load value. The mandrel load deflection measurement shows that the composite insulator has good bending resistance, good resistance to dancing and breeze vibration. When used in a tensile tower, it can withstand a certain bending moment.
Sweep
Whether the contamination of silicone rubber insulators is heavier than porcelain insulators, there is no consensus. Due to the occurrence of some pollution flashing accidents and excessive accumulation of insulators in the heavily polluted areas, the problem of cleaning of silicone rubber insulators gradually surfaced. Due to the high flashover voltage of the silicone rubber insulator, even if the water repellency decreases or disappears shortly, the fouling pressure is 20% higher than that of the porcelain insulator. Therefore, cleaning areas and general dirty areas are free of sweeping. Regular replacement can be used for particularly severe industrial and saline-alkali contaminated areas.
Seal reliability
The seal at the joint of the composite insulator end fitting and the mandrel sheath has not received sufficient attention. It may be the cause of brittle fracture and interface breakdown. The end connection structure of the silicone rubber insulator is mostly wedge-shaped, and slippage between the mandrel and the fitting during long-term heavy load operation is unavoidable. When the sealant and the fitting have poor adhesion, the slight slip is enough to make the seal open; when the sealant is not elastic enough, the excessive slip can break the sealant. From this perspective, the use of a crimped end structure is one of the ways to prevent seal damage. In addition, the engineering application sealant is mostly room temperature silicone rubber, its anti-aging performance is not as good as high temperature silicone rubber, which may lead to premature deterioration in the case of corona in the end fittings. For products of 110 kV and below, it is more dangerous to not use the pressure equalizing ring, or 220 kV and the upper pressure ring of the upper product. In short, whether the end seal is maintained for a long time under long-term electromechanical action requires trial demonstration and long-term operation.