Insulating Crepe Paper – Complete Technical Guide for Oil‑Immersed Transformer Insulation

What is Insulating Crepe Paper

Core Material & Key Technical Specifications

Note: Elongation is the most critical selection indicator. Low‑elongation grades focus on dielectric performance for gentle‑curve wrapping; high‑elongation grades are selected for sharp bends and complex conductor contours.

Main Application Scenarios in Transformer Manufacturing

1. Transformer lead wire wrapping

   The most common application. Transformer winding outgoing leads often contain multiple bends, corners and transition sections. Crepe paper’s stretch property enables tight wrapping without crack generation, avoiding air pockets which cause partial discharge under medium‑voltage and high‑voltage stress.
2. Tap‑changer and bushing‑connector insulation wrapping

   Used for insulating connection parts of tap changers and bushing‑connector terminals. Under equipment vibration and thermal expansion‑shrinkage cycles, crepe wrapping stays closely attached to metal surfaces.
3. Crepe paper tube for conductor sleeving

   Pre‑formed crepe paper tubes slide directly over copper conductors, replacing multi‑layer manual tape wrapping. Uniform wall thickness ensures consistent insulation, saves manual winding labour in mass transformer production.
4. Winding end stress relief insulation

   Applied on coil end portions to absorb mechanical stress generated during short‑circuit impact and thermal expansion, reducing insulation cracking risk.
5. Instrument transformers and reactors

   For current transformers, voltage transformers and shunt reactors, crepe paper provides compact insulation for small‑size bent conductors.

Core Performance Advantages of Insulating Crepe Paper

1. Excellent elongation & tear resistance

   Compared with flat kraft paper of equal thickness, crepe paper achieves 5‑15 times higher elongation and 3‑6 times higher tear resistance. It tolerates thermal expansion of copper conductors during transformer load changes without insulation rupture.
2. Superior oil‑impregnation capacity

   Micro‑wrinkled surface enlarges contact area with transformer mineral oil. Vacuum oil‑filling process achieves thorough penetration into paper fibre gaps, forming reliable oil‑paper composite insulation system and improving heat dissipation efficiency.
3. Good conformability for complex geometry

   It fits curved, angular and irregular metal conductor surfaces. Operators can complete multi‑layer overlapping wrapping without pre‑shaping the insulation material.
4. Low chemical impurity & long‑term stability

   High‑purity wood‑pulp raw material restrains chemical reaction with transformer oil and copper winding, slowing down insulation ageing for long service‑life transformers.
5. Multiple processing forms for flexible production

   Available as jumbo rolls, narrow slit tapes and finished tubes. Factories can choose forms according to manual wrapping or automatic winding production lines.

Insulating Crepe Paper VS Flat Kraft Paper / Pressboard

Practical engineering tip: In most oil‑immersed transformer designs, three materials are used together. Pressboard builds structural barriers, flat kraft paper insulates flat coil layers, and insulating crepe paper handles all bent lead‑wire positions.

Handling, Storage & Common Application Mistakes

Storage requirements

• Store in dry, clean indoor warehouse; ambient relative humidity controlled below 65 %.
• Seal original packaging before use, avoid absorbing moisture from air. Moist crepe paper will degrade dielectric strength.

• Prevent sharp object punctures and dust, metal‑particle contamination. Foreign conductive particles inside paper will trigger partial‑discharge faults in finished transformers.

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Common mistakes during production & wrapping

1. Over‑stretching crepe paper during wrapping operation: Excessive stretching will destroy the micro‑crepe structure and reduce elongation performance. Keep moderate tension.
2. Insufficient overlapping rate: Recommended wrapping overlap ratio is 25‑50 %. Too little overlap creates insulation gaps.
3. Mixing general‑purpose crepe paper (non‑transformer‑grade): Ordinary packaging crepe paper contains high ash and impurity content and must never be used inside oil‑filled power equipment. Always confirm compliance with IEC 60554 for transformer‑grade material.
4. Using damaged or damp crepe paper: Discard rolls/tapes with tear, mildew or moisture ingress, do not attempt to reuse them after simple drying.

How to Correctly Specify Insulating Crepe Paper for Procurement

1. Base paper thickness
2. Elongation grade (percentage)
3. Product form: roll / slit tape / crepe paper tube (if tube, define inner diameter and wall thickness)

4. Applicable standard: IEC 60554 transformer‑grade insulating crepe paper

   
   

   
   

Conclusion