What are the insulation materials of the oil-immersed transformer?

Oil-immersed transformer is a kind of transformer with an iron core and winding immersed in insulating oil. It has good insulation performance, good heat dissipation, low loss, good overload capacity, cheap transformer oil, and low cost. What are the insulation materials of the oil-immersed transformer? mainly: transformer oil, insulation paper, insulation board, insulation tube, insulation tape, and so on. We will introduce various insulation materials in detail in this article.

1. Transformer Oil

It is a kind of light yellow mineral oil, with low viscosity, good cooling, and good insulation performance. it is widely used in all kinds of transformers. Also suitable for transformers with high operating temperatures or high voltage grade and similar electrical equipment as insulation and heat transfer medium. The models are 10#, 25#, and 40#.

 

2. Insulation Paper

It has Diamond Dotted Paper (DDP), and electrical crepe paper.

DDP is used to reduce the interlayer displacement of transformer winding as well as the temperature rise of transformer oil. The product is suitable for the winding interlayer insulation of amorphous alloy transformers and instrument transformers, etc.

The electrical crepe paper is characterized by good oil solubility, widely used for lapping parts insulation and lead parts insulation wrapping in oil-immersed transformers, instrument transformers, and reactors etc., thus improving the electrical and mechanical properties of the product insulation structure.

 

3. Insulation board

It has an electrical press board and laminated wood.

The electrical pressboard is made of 100% pure sulphate wood pulp, with high chemical purity, good elongation rate, and great mechanical and electrical strength. It’s widely used in oil-immersed power transformers, reactors, capacitors, switches, etc., suitable for making bracing strips, paper tubes, pads, and end rings, etc.

The electrical laminated wood is mainly used as insulating and supporting materials in transformers and instrument transformers, suitable for making pressure plates for coil, core pads, trapezoidal pads, lead brackets, fixtures etc. It has a moderate specific weight, high mechanical strength, good solubility in transformer oil, excellent processability, etc. Additionally, its dielectric constant is similar to that of the transformer oil, so it can be in 105 ℃ transformer oil.

 

4. Insulation Tube

It has an electrical crepe paper tube, phenolic laminated paper tube, FRP core tube, and Epoxy fiberglass cloth laminated tube.

The electrical crepe paper tube is mainly used as insulation wrapping material for the oil-immersed transformer leads.

The phenolic laminated paper tube with good dielectric properties is suitable for transformer oil as insulation structural parts for electrical equipment in dry environments. Temperature resistance: E class 120 degrees Celsius.

The FRP core tube can be used to wrap various plastic films and special papers with high precision. This product does not suffer from dimensional changes caused by humidity and has superior dimensional and surface accuracy， compared to plastic cores such as ABS, and it does not rust as iron cores do.

The insulation epoxy glass cloth tube is made of an electric non-alkali glass fiber cloth impregnated with epoxy resin which is processed by hot pressing in baking and forming a mold. Insulation epoxy glass cloth tube has high mechanical properties, dielectric properties and good machinability. It is suitable for insulating structural parts in electrical equipment and can be used in humid environments and transformer oil.

 

5. Insulation Tape

Insulation tape. It has polyester unidirectional binding tape, electrical cloth tape, and polyester shrinkable tape.

The polyester unidirectional binding tape can be used for binding transformer iron cores.

The electrical white cloth tape, made of cotton yarns, is widely used for the general binding of coils on electrical appliances.

The electrical polyester high/low shrinkable tape has a certain degree of heat resistance and insulation, widely used as coil binding materials for motors, electrical appliances, and transformers.

 

6. Other insulation materials

like Oil duct strips,

The oil duct strip is made of a rectangular electrical board strip and DDP bonded with a special adhesive. The product can be firmly bonded to the winding coil, replacing the traditional corrugated containerboard which is easily deformed and produces displacement, so that the coil has better mechanical and electrical properties, and is therefore widely used in oil-immersed transformers.