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Effect of Composite Insulator Sealing Performance on Its Operation (Part 2)

Pulished on May. 15, 2020

2) overall injection molding process structure

This process is characterized by the use of a rubber injection molding machine. The umbrella skirt and sheath are injected into the mandrel at one time, and the rubber is finished under high temperature and pressure.

Adhesive forming and bonding with mandrel solve the key problems of "interface electrical breakdown" and end seal which affects the reliability of composite insulator. The adhesive interface of the composite insulator is greatly reduced, featuring stable product quality, high labor efficiency, firm adhesive interface, and no erosion by atmospheric pressure. Due to the reliable adhesive quality, 80% of power line fittings suppliers have started to use this process.

1.2 metal structure

At present, there are mainly three kinds of composite insulator-metal structure in operation: outer wedge type, adhesive type, and compression type. The characteristic of the outer wedge-type metal structure is that a group of metal wedges is pressed between the inner cone cavity and the mandrel of the metal, and the self-locking structure is formed by the friction force generated by the compressive stress between the metal wedges and the metal to bear the mechanical load of the insulator.

Composite Insulator

Composite Insulator

The characteristic of this structure is that the mandrel does not need to be processed. When the friction coefficient between the wedge and the metal cone cavity, the mandrel, and the external taper of the metal inner cavity and the wedge are ideally matched, the outer wedge and the mandrel can be synchronized Mobile, with self-locking function. However, due to the difficulty of processing and matching the metal inner cone cavity and the outer wedge, it is difficult to ensure that each fitting is accurately matched with the wedge and the core rod in batch production. Therefore, the composite insulator of this structure has large mechanical strength dispersion, and there is a possibility of relative displacement between the fitting and the core rod, resulting in the defect of inadequate sealing. The glue-mounted structure is to process a groove of a certain depth on the surface of the mandrel and the inner cavity of the metal fitting, place a metal spring in the groove and finally pour the adhesive into the gap between the mandrel and the inner cavity of the metal fitting. After the adhesive is cured, use The inlaid metal spring connects the metal fitting and the mandrel. The mechanical strength of this structure is reliable without relative displacement, and the disadvantage is that the production cycle is long.

The crimping structure is to tightly crimp the fittings and the mandrel together on the crimping machine so that the fittings have a certain plastic deformation so that the inner surface of the mandrel and the fittings produces a pre-tightening hoop force, thereby achieving a close fit The friction load generated by contact with each other bears the tensile load. The process structure is simple, the dispersion of mechanical strength is small, the labor efficiency is high and there is no relative displacement, which has won the approval of manufacturers and users and has been generally adopted by manufacturers.