DDP insulation paper for Inter-Layer Insulation in Oil-Immersed Transformers :Selection Guide

DDP Paper for Inter-Layer Insulation in Oil-Immersed Transformer Windings 1. Scope of Application Inter-layer insul...

DDP Paper for Inter-Layer Insulation in Oil-Immersed Transformer Windings

1. Scope of Application

Inter-layer insulation of oil-immersed transformer windings
Voltage levels: 10 kV – 220 kV
Winding types: cylindrical, disc (continuous), multi-layer
Base material compatible with oil-impregnated insulation systems (mineral oil or ester oil)

2. Selection Principles

Selection Based on Voltage Level and Insulation Margin

The thickness of DDP insulation paper should ensure that inter-layer insulation strength meets operating voltage plus safety margin.
Recommended thickness values:

Principle: Higher voltage → thicker DDP paper ; also consider mechanical short-circuit force requirements.

Selection Based on Short-Circuit Force and Mechanical Stress

Large-capacity transformers, high short-circuit current systems, and compact windings → choose thicker DDP  insulation paper  with higher adhesion strength.
Uniform and regular resin dot distribution → ensures inter-layer shear strength.
Typical inter-layer adhesion strength ≥ 400 kPa (adjustable according to design requirements).

Selection Based on Oil Channels and Heat Dissipation

Resin dot coverage should be moderate: 15%–30%
Avoid continuous resin layers → ensure oil channels remain open
Ensure uniform oil impregnation → stable insulation performance

Selection Based on Winding Process and Curing Conditions

Resin dot melting temperature must match the winding drying and curing process
Insufficient curing → inadequate inter-layer bonding
Over-curing → paper embrittlement and accelerated thermal aging

Selection Based on Thermal Performance and Aging

Compatible with oil-immersed transformer insulation class A / F
Stable performance at long-term oil temperatures of 90–110 °C
Short-term thermal resistance ≥ 120 °C
Resistant to thermal aging: no embrittlement, no delamination, no powdering
Selection Based on Oil Compatibility
Compatible with mineral oil or ester oil
Does not affect oil dielectric loss (tanδ)
Good oil absorption → prevents dry spots that could cause breakdown

Selection Based on Winding Structure

Cylindrical winding → ensures radial stability
Disc (continuous) winding → ensures axial stability
Compact winding → improves mechanical strength and reduces the need for additional reinforcement

3. Selection Summary

The selection of DDP insulation paper  should comprehensively consider voltage level, short-circuit force, inter-layer adhesion, oil impregnation, thermal stability, and process compatibility. Proper selection ensures reliable, safe, and durable inter-layer insulation in oil-immersed transformer windings.

4. Manufacturer selection and quotation

XUJUE ELECTRICAL is a professional DDP transformer insulation material manufacturer, since 1958., ensuring reliable quality and stable performance. Throughout customer service, Xujue’s professional team can provide suitable specifications and models of DDP insulation paper 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.

Contact Xujue Electrical  now to get detailed product information and quotation. We can also mail samples for free for your testing.