Design and Manufacturing of Composite Insulators

1. Dimensional Tolerances

Unless otherwise specified, the dimensional tolerances of composite insulators shall comply with the following regulations (where d is the inspection dimension in mm):

• For d ≤ 300 mm: ± (0.04d + 1.5) mm

• For d > 300 mm: ± (0.025d + 6) mm (Maximum deviation: ±50 mm)

2. Structural Composition

A composite insulator consists of at least two insulating parts: the core rod and the sheath (with integrated sheds), equipped with metal end-fittings.

3. Composite Insulator Core Rods

The core rod is the internal insulating component of the composite insulator, designed to ensure the specified mechanical strength.

• Material: It is manufactured from glass fiber reinforced resin rods (FRP/GRP).

• Corrosion Resistance: The rod must possess excellent acid-corrosion resistance; the use of specialized acid-resistant core rods is highly recommended.

• Performance Requirements: The core rod must withstand long-term mechanical loads across a wide temperature range, while simultaneously enduring continuous operating voltages and short-term overvoltages.

• Process Compatibility: Core rods used in injection molding processes must be high-temperature resistant.

• Compliance: Core rods shall meet the requirements of the DL/T 864 standard.

4. Quality Control of Core Rods

Core rods must adhere to strict quality control standards regarding longitudinal and transverse dielectric strength, glass fiber content, and hygroscopicity (moisture absorption).

• Dye Penetration Test: Must comply with Clause 5.4.1 of Annex D in GB/T 19519.

• Water Diffusion Test: Must comply with Clause 5.4.2 of Annex D in GB/T 19519.

5. Sheath and Sheds

The sheath is the external insulating part of the composite insulator, providing the necessary creepage distance and protecting the core rod from environmental and climatic influences. The sheds are projecting parts of the sheath designed to increase the creepage distance.

• Minimum Sheath Thickness:

  • Voltage levels ≤ 220kV: Minimum thickness ≥ 3.0 mm.

  • Voltage level 500kV: Minimum thickness ≥ 4.5 mm.

• Material Consistency: The sheath and sheds must be made of the same material.

• Manufacturing Process: The sheath and sheds must be integrally molded (utilizing either injection molding or compression molding).