High-Density Electrical Pressboard Strips for Transformer Insulation Systems

Applications of Electrical Pressboard Strips in oil Transformers In transformer construction, electrical pressboard ...

Applications of Electrical Pressboard Strips in oil Transformers

In transformer construction, electrical pressboard strips (commonly referred to as insulation spacers, sticks, or stays) are critical components that form the “skeleton” of the unit. They serve not only as insulation but also as mechanical supports and oil flow guides.
Their specific applications are reflected in the following four areas:

1. Formation of Cooling Oil Ducts (Core Function)

In oil-immersed transformers, heat is generated within the windings. Pressboard strips are placed horizontally or vertically between winding layers or disks:
Axial Oil Ducts: Vertical long strips (sticks) are placed between winding layers to create longitudinal ventilation channels, allowing transformer oil to flow from bottom to top.
Radial Oil Ducts: In disc-type windings, horizontal spacer strips create transverse channels, enabling oil to penetrate deep into the windings to carry away heat.

2. Mechanical Support and Short-Circuit Resistance

Transformers generate massive axial electromagnetic forces during operation or short-circuit events.
Compressive Support: High-density pressboard strips withstand the axial pressure exerted on the windings, ensuring the stability of the winding height.
Prevention of Deformation: Under high-voltage impact, these strips act as physical barriers to prevent the coils from shifting or tilting, which is vital for the transformer’s short-circuit withstand capability.

3. Electrical Insulation and Isolation

Inter-layer/Inter-segment Insulation: Pressboard strips increase the physical distance between energized components.
Improving Field Distribution: In oil-paper insulation systems, the combination of pressboard strips and transformer oil effectively disrupts the formation of “electrical bridges,” thereby increasing the overall breakdown voltage.

4. Positioning and Reinforcement of Winding Structures

End Insulation: Thick pressboard strips (pressure strips) are used at the ends of the windings to apply pressure and ensure a compact overall structure.
Lead Support: Some strips are used to support internal leads, preventing them from sagging due to vibration or gravity, which could cause a short circuit to ground.

Key Requirements in Application:

High Compressive Strength: Must be machined from high-density pressboard to prevent thinning due to shrinkage over long-term operation, which could cause winding looseness.
Pure and Non-conductive: Strips must be extremely pure, strictly free of metal dust or acidic substances to avoid triggering partial discharge.
Pre-drying Treatment: Must undergo vacuum drying before assembly to completely remove moisture and be thoroughly impregnated with oil after assembly.
Do you require a more technical terminology version for a formal report, or would you like to discuss the manufacturing process of these strips?