Composite Insulator: Definition, Structure & Advantages
1. What is a Composite Insulator?
A composite insulator (or polymeric insulator) is a modern electrical insulation device used in high-voltage transmission lines, substations, and railways. It combines a fiberglass reinforced plastic (FRP) core with silicone rubber housing, offering superior mechanical strength, lightweight design, and pollution resistance compared to porcelain/glass insulators.
2. Composite Insulator Structure
Composite insulators consist of a fiberglass core rod, silicone rubber housing, adhesive layer, end fittings, and grading rings. Each component plays a critical role in ensuring mechanical strength, electrical insulation, and long-term reliability.
2.1 Core Rod
The core rod is the primary load-bearing component and a key part of the internal insulation. It must exhibit high mechanical strength, excellent insulation properties, and long-term stability.
· Fiberglass reinforcement: The core rod is reinforced with high-strength glass fibers, melted at high temperatures into smooth cylindrical strands (diameter ≤10μm) with a tensile strength of approximately 1500 MPa.
· Epoxy resin matrix: The fibers are bonded together using an epoxy resin matrix treated with a silicone-based coupling agent, forming an epoxy fiberglass reinforced rod (FRP rod) that transmits mechanical loads.
2.2 Silicone Rubber Housing & Sheds
The silicone rubber housing serves as the external insulation, providing resistance to wet and pollution flashover while protecting the core rod from environmental degradation.
· Material composition: The housing is made of high-temperature vulcanized (HTV) silicone rubber, reinforced with coupling agents, flame retardants, reinforcing fillers, and anti-aging additives.
2.3 End Fitting Connection
Mechanical loads from conductors are transferred to the core rod through end fittings (e.g., ball-and-socket connections), which are the most stress-concentrated areas.
· Structural impact: Different connection designs result in varying stress distributions, directly affecting the mechanical performance of the insulator.
· Critical factor: The quality of the end fitting connection determines the full utilization of the core rod’s strength and overall mechanical reliability.
2.4 Adhesive Bonding Layer
The adhesive layer bonds the silicone rubber housing to the core rod, ensuring structural integrity and contributing to internal insulation.
· Early methods: Used room-temperature-curing adhesives with segmented shed bonding.
· Modern solution: Integrated injection-molded housing with high-temperature-cured bonding improves adhesion, minimizes interfaces, and ensures impermeability for superior insulation performance.
2.5 End Sealing Layer
The end sealing layer bonds the housing, core rod, and end fittings into a single unit, ensuring airtightness.
· Critical performance factor: Sealing quality directly impacts electrical and mechanical properties.
2.6 Grading Ring
Grading rings are essential for:
· Electric field control: Uniform voltage distribution along the insulator axis.
· Corona suppression: Preventing partial discharges.
· Insulator protection: Enhancing long-term durability.
3. Key Advantages Over Traditional Insulators
Feature Composite Insulator Porcelain/Glass Insulator
Weight 60-70% lighter Heavy, fragile
Pollution Resistance Self-cleaning silicone sheds Requires frequent washing
Mechanical Strength Higher tensile load capacity Prone to cracking
Lifespan 20+ years 15-20 years
4. Applications of Composite Insulators
4.1 Overhead Transmission Lines (AC & DC)
· Ultra-High Voltage (UHV) Lines (≥800kV)
· High-Voltage AC Lines (110kV–500kV)
· HVDC Transmission Systems
4.2 Railway electrification
· 25kV Catenary Systems
· DC Traction Power (1.5kV/3kV)
4.3 Substation Equipment
· Bushings for Transformers & Circuit Breakers
· Surge Arresters & Disconnectors
4.4 Coastal/wind farm projects
· salt fog resistance (passed IEC 62217 salt mist test)
4.5 Polluted industrial areas
5. Why Choose Composite Insulators?
· Structural: 70% weight reduction enables lighter towers
· Safety: Non-fragmenting failure mode
· Economic: 60% lower lifecycle costs
· Environmental: IEC 62217 compliant for coastal installations
For product specifications or technical consultation: sales@tcipower.com
