Composite insulators have the advantages of good anti-fouling performance, light weight, high mechanical strength, and low maintenance. They have been widely used in Class III and above. The main structure of the composite insulator is generally composed of a core rod, a shed sheath (adhesive layer), a joint fitting and an attachment (equal pressure ring). The core rod is made of resin bonded with millions of glass fibers arranged in parallel along the axis. The formed glass steel rod, the core rod will be hydrolyzed by the moisture, the mechanical strength of the composite insulator is reduced, and the string accident is caused, so that the core rod is protected from the tide is the basic condition for the safe operation of the composite insulator. The composite insulator is equipped with 1~2 equalizing rings to make the electric field distribution uniform, prevent the high-voltage electric field from accelerating the aging of the composite insulator, and have an arc-ignition effect during over-pressure, shortening the discharge time and ensuring that the surface of the shed is not burnt by the arc. Strict operation is required for the installation of the pressure equalizing ring
The cause of the string loss accident occurred in the composite insulator: one is due to the structure and process of the end joint, and the second is due to the creep properties of the mandrel and the moisture aging of the material. In the long-term operation, due to the combined action of atmospheric environment, electric field, mechanical force, etc., the glass fiber in the mandrel will cause mechanical fatigue, the epoxy resin material will age, and the end fitting and the mandrel joint will also loosen. Therefore, the production unit should strictly control the quality of the joint between the metal end and the mandrel.