Oil duct strip for oil-immersed transformers Introduction and technical standards

The oil duct strip (also called insulating support strip or spacer strip) of oil-immersed transformers is a key insul...

The oil duct strip (also called insulating support strip or spacer strip) of oil-immersed transformers is a key insulating component used to fix and isolate windings and ensure smooth oil passages. The following is a detailed description of its introduction, technical standards and installation requirements:

Introduction to oil duct strip

1. Function

Mechanical support: maintain the distance between windings to prevent deformation or displacement.

Insulation isolation: form oil passages to promote transformer oil circulation and heat dissipation.

Electrical strength: withstand the electric field stress between windings.

2. Common materials

Laminated paperboard (Pressboard): high strength and good insulation after being impregnated with transformer oil.

Epoxy glass cloth board: used in scenarios with high mechanical strength requirements.

Nomex® aramid material: high temperature resistant, flame retardant, suitable for special environments.

3. Shape and size

Rectangular strip: common thickness 3~10mm, width 20~50mm, length customized according to winding height.

Chamfer design: edge chamfer to reduce the risk of partial discharge.

Technical standards

Oil duct strip must comply with the following international/domestic standards:

IEC 60641 (laminated paperboard standard)
Specified density (usually ≥1.15 g/cm³), tensile strength (longitudinal ≥80 MPa), oil absorption, etc.

GB/T 19264 (Chinese electrical laminate standard)
Includes requirements such as oil resistance and dielectric strength (≥40 kV/mm).

IEEE C57.12.00 (general standard for transformers)
Proposes overall requirements for the mechanical and electrical properties of insulating components.

User technical agreement: There may be additional requirements for material flame retardancy (such as UL94 V0), environmental protection (sulfur-free), etc.

Installation requirements

1. Pretreatment

Drying treatment: Dry at 105~110℃ before installation to remove moisture (water content ≤0.5%).

Oil impregnation: Pre-impregnate transformer oil to improve insulation performance.

2. Installation specifications

Position and spacing:

Evenly distributed, the spacing is designed according to the winding diameter and heat dissipation requirements (usually 50~150mm).
The oil channel width error is ≤±1mm to ensure smooth oil flow.

Fixed method:

Use insulating binding tape (such as glass fiber tape) to tie firmly without looseness.

Avoid metal fasteners to prevent partial discharge.

Edge treatment:

All edges and corners must be rounded or covered with insulating paper to prevent electric field concentration.

3. Quality control

Cleanliness: There must be no dust or metal chips left during installation.

Withstand voltage test: After installation, it must pass the partial discharge test (such as ≤10pC) and the power frequency withstand voltage test.

4. Environmental requirements

Humidity control: The relative humidity of the installation environment is ≤60%, and it should be operated in a dry room if necessary.

Temperature adaptation: The thermal expansion coefficient of the material must match the winding to avoid temperature difference deformation.

Common problems and countermeasures

Oil channel blockage: Check the position of the support strip during installation to avoid misalignment.
Partial discharge: Ensure that the surface is smooth and free of burrs, and apply semiconductor paint for equalization if necessary.
Failure due to moisture: Seal the package during storage and retest the moisture content before installation.

Special application scenarios

High overload transformer: Use high temperature resistant materials (such as aramid) and increase the number of support strips.
High altitude areas: The creepage distance needs to be increased, and the support strip height may need to be adjusted.
Although the oil duct strip is a small component, it directly affects the heat dissipation and insulation life of the transformer, and must be strictly implemented according to standards and process requirements.