How to Select the Thickness of Transformer Crepe Paper

Transformer crepe paper is widely used in oil-immersed transformers for conductor wrapping, lead insulation, cushioni...

Transformer crepe paper is widely used in oil-immersed transformers for conductor wrapping, lead insulation, cushioning, and oil duct formation. Selecting the correct thickness directly affects insulation reliability, mechanical strength, and oil circulation performance.

Below is a practical engineering guide for choosing the proper crepe paper thickness.

Selection Based on Voltage Level

The higher the transformer voltage, the greater the insulation distance required.

Note: Final selection depends on total insulation coordination, not only paper thickness.

Selection Based on Application Position

Different parts of the transformer require different mechanical and insulation performance.
✔ Conductor Wrapping
Common thickness: 0.5 – 1.0 mm
Purpose: turn insulation & cushioning
Requirement: flexibility + good elongation
✔ Lead Insulation
Common thickness: 1.0 – 1.5 mm
Purpose: withstand higher electric stress
Requirement: higher dielectric strength
✔ Oil Duct Formation
Common thickness: 1.0 – 1.5 mm
Purpose: maintain oil channels
Requirement: good compression resistance

Selection Based on Mechanical Strength

If the transformer:
Has large current conductors
Experiences strong electromagnetic forces
Is designed for short-circuit resistance
Then thicker crepe paper (≥1.0 mm) is recommended to enhance mechanical stability.

Selection Based on Thermal Design

Standard transformer crepe paper belongs to Class A insulation (105°C).

Thickness impacts:
Heat dissipation
Oil penetration speed
Drying efficiency

Thicker paper:
Improves cushioning
But may slightly reduce oil penetration speed
Therefore, balance insulation margin and cooling performance.

Engineering Calculation Consideration

Thickness should match:
Required dielectric strength (kV/mm)
Safety factor
Impulse voltage level (BIL)
Total insulation structure design
Crepe paper is only one component of the insulation system, working together with pressboard, kraft paper, and transformer oil.

Practical Industry Recommendation

In most distribution transformers (10–35 kV), 0.8 mm and 1.0 mm are the most commonly used specifications.
For power transformers above 110 kV, 1.2–1.5 mm is more common for lead insulation and oil duct applications.

Final Advice

Choosing transformer crepe paper thickness depends on:

Voltage class
Installation position
Mechanical requirements
Thermal design
Overall insulation coordination