Application of Fiberglass Filament Wound Tube End Rings in Dry-Type Transformers

Application of Fiberglass Filament Wound Tube End Rings in Dry-Type Transformers I. What Is a Fiberglass Filament Wo...

Application of Fiberglass Filament Wound Tube End Rings in Dry-Type Transformers

I. What Is a Fiberglass Filament Wound Tube End Ring?

A fiberglass filament wound tube end ring is an insulating structural component manufactured from alkali-free glass fiber and epoxy resin using a filament winding process, then cut into ring or semi-ring shapes according to design requirements. It is widely used at the end sections of windings
in dry-type transformers.

Common names include:
Fiberglass filament wound end ring
Insulating end ring
Winding end support ring
GFRP End Ring / Filament Wound Tube Ring

II. Installation Position in Dry-Type Transformers

Location:

• Installed at the upper and lower ends of high-voltage or low-voltage windings
• Positioned between the winding ends and metal clamping plates as part of the end support system

Typical structural arrangement:

Clamping plate
|
Fiberglass filament wound end ring
|
Winding end
|
Spacer / air duct structure

III. Main Functions and Roles

1. End Insulation and Electrical Isolation

• Provides high dielectric strength to isolate winding ends from metal clamping components
• Prevents creepage, partial discharge, and flashover
• Suitable for 10 kV, 20 kV, and 35 kV dry-type transformers

2. Mechanical Support and Structural Stability

• Bears axial compressive forces at winding ends
• Prevents deformation and axial displacement under short-circuit conditions
• Improves short-circuit withstand capability

3. Electric Field Optimization and Partial Discharge Reduction

• Smooths electric field distribution at winding ends
• Reduces electric field concentration points
• Lowers partial discharge (PD) levels

4. Thermal Resistance and Service Life Improvement

• Suitable for Class F (155°C) and Class H (180°C) insulation systems
• Maintains stable performance without softening or carbonization

IV. Why Dry-Type Transformers Rely on Fiberglass End Rings

Item	Dry-Type Transformer
Insulation medium	Solid insulation + air
Cooling method	Natural air / forced air
Partial discharge risk	Higher
End structure strength requirement	Higher

Advantages of fiberglass filament wound end rings:

• Low moisture absorption and excellent dimensional stability
• High mechanical strength compared to paper-based insulation
• No oil compatibility limitations, ideal for dry-type transformers

V. Key Performance Requirements

Property	Typical Requirement
Dielectric strength	≥ 20 kV/mm
Volume resistivity	≥ 1012 Ω·cm
Flexural strength	≥ 300 MPa
Compressive strength	≥ 250 MPa
Thermal class	Class F / Class H
Water absorption	≤ 0.2%

VI. Selection Guidelines and Considerations

1. Selection by Voltage Class

• 10 kV: Standard fiberglass filament wound end rings
• 20–35 kV: Increased wall thickness and high-density filament wound tubes recommended

2. Selection by Mechanical Strength

• For dry-type transformers ≥ 2500 kVA, axial compressive strength is critical
• Ordinary FR4 laminated boards assembled into rings are not recommended

3. Surface Quality and Machining

• Smooth inner and outer surfaces without burrs
• Flat cut edges to avoid local electric field concentration
• Chamfered or rounded edges when required

VII. Summary

Fiberglass filament wound tube end rings are essential insulating and structural components in dry-type transformers, providing high dielectric strength, excellent mechanical support, thermal resistance,and superior short-circuit performance, helping reduce partial discharge and extend transformer service life.

Factory selection

XUJUE ELECTRICAL has over 65 years of experience in producing transformer Fiberglass Filament Wound Tube End Rings insulation materials, ensuring reliable quality and stable performance. Throughout customer service, Xujue’s professional team can provide suitable specifications and models of Fiberglass Filament Wound Tube End Rings insulation materials based on the specific requirements and application scenarios of transformer manufacturing. Whether for small batches or large-scale production, Xujue responds promptly, offering attentive service and high-quality products.