Insulating Materials For Power Transformers

Insulating Materials For Power Transformers Insulation material is one of the most important materials in transforme...

Insulating Materials For Power Transformers

Insulation material is one of the most important materials in transformers. Its performance and quality directly affect the reliability of transformer operation and the service life of transformers. In recent years, new insulation materials used in transformer products have emerged in an endless stream. With the rapid development of science and technology, the application of electrical equipment such as motors and transformers has become increasingly widespread. However, the reliability and service life of transformer operation depend to a large extent on the insulation materials used. Insulation materials are increasingly valued by people engaged in transformer design and manufacturing. In the past two decades, new products, new technologies, and new theories in transformer insulation materials have continued to emerge and develop, making transformer insulation materials and their applications a very important discipline. Insulation materials, also known as dielectrics, are materials with high resistivity and low conductivity. Insulation materials can be used to isolate conductors with or different potentials, so that current flows in a certain direction. In transformer products, insulation materials also play the role of heat dissipation, cooling, supporting, fixing, arc extinguishing, improving potential gradient, moisture-proof, mildew-proof and protecting conductors. Insulating materials are classified by voltage level: generally divided into: Y (90℃), A (105), E (120℃), B (130℃), F (155℃), H (180℃), C (greater than 180℃). The heat resistance level of transformer insulation materials refers to the maximum temperature that the insulation materials are allowed to withstand in the transformer. If the insulation materials are used correctly, the service life of the materials can be guaranteed to be 20 years. Otherwise, the service life will be reduced according to the 8℃ law (for every 8℃ increase in the temperature of grade A insulation, the service life is reduced by half, the B insulation is 10℃, and the H grade is 12℃. This law is called the 8℃ law of thermal aging). The heat resistance of insulating materials composed of polymers is half lower than that of inorganic dielectrics. The performance of insulating materials is closely related to their molecular composition and molecular structure. There are many varieties of transformer insulation materials, which can generally be divided into gas insulation materials, liquid insulation materials and solid insulation materials according to their form.
Solid insulation materials: Solid insulation materials used in transformers refer to insulation materials that are solid in form or have undergone chemical reactions and physical changes to become solid. There are many kinds of solid insulation materials for transformers, such as insulating paper, insulating cardboard, Nomex paper, glued paper, electrical laminated wood, epoxy glass cloth board, low dielectric loss laminate, insulating paint, insulating glue, cotton cloth tape, shrink tape, mesh non-woven polyester tape, etc.

01 Insulating paper
The insulating paper mentioned here refers to pure sulfate wood pulp paper. Other insulating papers include synthetic fiber paper (such as Nomex paper), nitrile insulating paper (such as Denison paper), etc.
02 Insulating corrugated paper
It is made by corrugating insulating paper for electrical use. There are wrinkles along its transverse direction, and the wrinkles are pulled apart when stretched. Due to different corrugation processing procedures, corrugated paper with different elongations can be made. The thickness of insulating paper is generally 0.05mm~0.12mm, and the elongation range is 5%~200%. Insulating corrugated paper is often used for winding insulation of oil-immersed transformers, such as winding heads,
03Nomex paper
It is a heat-resistant synthetic fiber paper produced by DuPont in the United States. Nomex is the trade name of this fiber paper. The main component of Nomex is aromatic polyamide, which has good heat aging resistance. It can be used for a long time at 220℃ and belongs to Class C insulation material.
04 Diamond dot glue paper DDP insulation paper
It can be divided into three types: single-sided glue paper, double-sided glue paper and diamond glue paper. The glue paper type is made by coating 0.07mm winding paper with phenolic resin or epoxy resin and then baking and drying.
05 Insulation paperboard
It is made of sulfate wood pulp papermaking. It is used for oil gap pads, partitions, paperboard tubes, corrugated paper, iron yoke insulation, clip insulation and end insulation winding pressure plates of pancake windings.
06 Insulation tube
The insulation tubes used in transformers include phenolic glue paper tubes, epoxy glass cloth tubes, fiberglass tubes and paperboard tubes.
07 Corrugated cardboard
In the oil plate gap structure composed of multi-layer paper tubes of high-voltage transformers, corrugated cardboard can be used instead of stays to form oil gaps. This insulation structure can save insulation materials while ensuring insulation performance.
8 Electrical laminates
Insulating materials with a layered structure made of paper, cloth and wood veneer as the base material, impregnated with different adhesives, and hot pressed or rolled.
9 Nomex paperboard
A paperboard made of synthetic materials based on aromatic amide fibers.
10 Drawing rods
Inter-stage rods, air gap stays, screws and screws of dry-type transformer core columns often use glass fiber drawing rods.
11 Electrical thin molds and electrical composite materials
They have excellent dielectric properties and are all thin sheet insulation materials. Electrical films include polypropylene films, polyester films and polyimide films. Composite materials are composite products made by bonding fiber materials to one or both sides of the film.
12 Glass varnished cloth
Glass varnished cloth is made of alkali-free glass cloth for electrical use impregnated with insulating varnish and baked. Used for dry-type transformers.
13 Insulating materials for transformer binding
The insulating materials for transformer binding include cotton cloth tape, compression tape, semi-dry thin wire tape, mesh semi-dry weftless tape, glass cloth tape and polyester rope.

Iron core strap: Hyperten 2000HP
Cooling oil channel, insulating support: PSP3052
Coil outlet insulation: ISO100/ISO131/ISO160
Temperature resistance grade: A, H.

Application scope	Product name Common name / structure	Commonly used thickness/mm	Insulation level	Temperature resistant
Iron core strap	Hyperten 2000HP Pre-impregnated resin glass fiber core strap	0.32	H	180℃
Cooling oil channel, insulating support	PSP3052 Power transformer pressure board	0.8/1.6/3.2	A	105℃
Coil outlet insulation	ISO100 / ISO131 / ISO160 Insulating crepe paper	0.30/0.33/0.35	E	105℃