Application of Crepe Paper Tubes in Transformers

Crepe Paper Tube is a cylindrical insulating component manufactured from electrical-grade crepe insulating paper. It is widely used in oil-immersed power transformers, instrument transformers, and reactors. Owing to its excellent electrical insulation properties, high mechanical strength, and superior oil absorption capability, crepe paper tubing has become an indispensable insulating component within transformer structures.

Why Are Crepe Paper Tubes Used in Transformers?

Excellent Flexibility and Conformability

The unique corrugated structure of crepe paper provides outstanding longitudinal elasticity, allowing the tube to closely conform to and wrap transformer leads, conductors, and irregularly shaped components.

High Dielectric Strength

The longitudinal crepe structure effectively increases the creepage distance, promotes more uniform electric field distribution, and helps prevent partial discharge and insulation breakdown.

Adaptability to Thermal Expansion and Contraction

When used in conjunction with transformer oil, crepe paper tubes can withstand continuous operating temperatures up to 105°C, while also absorbing mechanical stresses caused by temperature fluctuations.

Typical Applications in Transformers

Lead Insulation

Used as insulating sleeves for transformer winding leads, HV/LV outgoing conductors, and tapping leads, preventing short circuits between conductors or between conductors and grounded parts.

Connection Point Insulation

Provides reliable local insulation reinforcement at complex tapping points, lead exits, and electrical connection nodes.

Oil Duct Support

Serves as a supporting framework within cooling oil channels, maintaining unobstructed transformer oil circulation and improving heat dissipation efficiency.

Common Specification Selection of Crepe Paper Tubes

The following are the most commonly used specifications and application characteristics for transformers rated at 10kV, 35kV, and 110kV.

1.10kV Voltage Class (Distribution Transformers)

10kV transformers generally have smaller capacities, thinner internal conductors, and relatively lower insulation requirements.

Common Wall Thickness:1.0 mm – 2.0 mm

With the assistance of transformer oil, a wall thickness of approximately 1 mm is usually sufficient to provide adequate dielectric strength, as transformer oil typically offers a breakdown strength exceeding 10 kV/mm.

Common Inner Diameters

4 mm, 6 mm, 8 mm, 10 mm, 12 mm

These sizes are commonly used for insulating bare copper conductors and tap-changer leads.

Typical Specifications

Φ6 × 1.0 mm ,Φ10 × 1.5 mm

2.35kV Voltage Class

For 35kV transformers, both operating voltage and current increase significantly. Larger conductors and enhanced insulation coordination are required between winding leads, tap changers, and bushing conductors.

Common Wall Thickness:2.0 mm – 4.0 mm

To satisfy higher lightning impulse and power-frequency withstand voltage requirements, thicker tubing or multi-layer insulation systems are commonly employed.

Common Inner Diameters

14 mm, 16 mm, 18 mm, 20 mm, 25 mm

Suitable for larger stranded copper conductors and copper rods.

Typical Specifications

Φ16 × 2.0 mm ,Φ20 × 3.0 mm

3.110kV Voltage Class (High-Voltage Power Transformers)

110kV transformers belong to the high-voltage category and feature highly complex lead structures. Insulation coordination and electric field control become critical design considerations.

Common Wall Thickness:4.0 mm – 6.0 mm

In some applications, multiple layers may be combined to achieve an overall insulation thickness exceeding 8 mm. Such configurations are necessary to withstand high electric field stress and prevent corona discharge and surface flashover.

Common Inner Diameters

25 mm, 30 mm, 40 mm, 50 mm

Large-capacity transformers require larger conductors to carry high currents, necessitating correspondingly larger insulation tubing.

Typical Specifications

Φ30 × 4.0 mm,Φ40 × 5.0 mm

Industry Development Trends

Driven by the expansion of Ultra-High Voltage (UHV) transmission projects, renewable energy grid integration, and growing demand for large power transformers, crepe paper tubes are evolving toward: Higher insulation performance,Greater mechanical strength,More precise dimensional tolerances,Improved manufacturing consistency

Particularly in Extra High Voltage (EHV) and Ultra High Voltage (UHV) transformer applications, high-quality crepe paper tubing plays a vital role in ensuring long-term operational reliability and electrical safety.