Insulation material is one of the most important materials in transformers, and 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 endlessly. 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 the transformer depends to a large extent on the insulation materials used. Insulation materials are increasingly valued by those engaged in transformer design and manufacturing. In the past two decades, new products, new technologies, and new theories of transformer insulation materials have continuously emerged and developed, so that transformer insulation materials and their applications have formed a very important discipline.
Insulation Materials
Insulation materials, also called dielectrics, are materials with high resistivity and low electrical conductivity. Insulating materials can be used to isolate live or different potential conductors so that current flows in a certain direction. In transformer products, insulation materials also play the role of heat dissipation, cooling, support, fixing, arc extinguishing, improvement of potential gradient, moisture resistance, mildew resistance, and protection of conductors. Insulation materials are classified by voltage level: generally divided into: Y (90 ° C), A (105), E (120 ° C), B (130 ° C), F (155 ° C), H (180 ° C), C (greater than 180) ° C). The heat resistance rating of the transformer insulation material refers to the maximum temperature that the insulation material can withstand in the transformer. If the insulating material is used correctly, the material's 20-year life can be guaranteed. Otherwise, it will be reduced according to the law of 8 ° C (for every 8 ° C increase in the insulation temperature of Class A, the service life will be reduced by half, that of Class B insulation is 10 ° C, and that of Class H is 12 ° C. This rule is called the 8 ° rule of thermal aging) Service life. An insulating material composed of a polymer has half the heat resistance than an inorganic dielectric.
Variety of transformer insulation materials
The properties of insulating materials are closely related to their molecular composition and molecular structure. There are many types of transformer insulation materials. Generally, they can be divided into gas insulation materials, liquid insulation materials and solid insulation materials.
Transformer solid insulation materials
Solid insulation materials: Solid insulation materials used in transformers refer to insulation materials that are solid in form or have undergone chemical reactions and have undergone physical changes. There are many types 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 tape, shrink tape, Netted polyester tape and so on.
1 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 Dennison paper), and so on.
2 Insulated wrinkled paper: It is made by creping the insulating paper for electricians. There are wrinkles along its transverse direction, which are pulled apart when stretched. Due to different creping processing procedures, crepe paper with different elongation can be made. The thickness of insulating paper is generally 0.05mm ~ 0.12mm, and the elongation range is 5% ~ 200%. Insulated corrugated paper is often used for wrapping insulation of oil-immersed transformers, such as windings.
3 Dennison paper: Insulating paper is changed into nitrile paper. In the manufacturing process, dinitrileamine, vinyl cyanide, etc. are added to the pulp. Produced by American Dennison Company, the characteristic is that after the paper is wrinkled, after calendering, it has good mechanical cyanity and appropriate elongation. It is an ideal material for the insulation of large transformer winding turns. Using it to wrap the transposed conductor can ensure Pack tightly without bulging.
4 Nomex paper: is a heat-resistant synthetic fiber paper produced by DuPont of the United States. Nomex is the trade name of this fiber paper. Nomex's main component is aromatic polyamide, which has good heat aging properties. It can be used for a long time at 220 ℃ and belongs to the class C insulation material.
5 Adhesive paper: It can be divided into three types: single-sided adhesive paper, double-sided adhesive paper, and diamond-shaped adhesive paper. Adhesive paper is made of 0.07mm rolled paper coated with phenolic resin or epoxy resin and baked and dried.
6 metallized paper: used for ground screen and electrostatic screen. Its backing paper is 0.2mm thick insulating paper, aluminum foil is 0.02mm thick, and the insulation of the insulation screen is wrapped.
7 Insulating cardboard: made of sulfated wood pulp paper. It is used for oil-gap pads, separators, cardboard tubes, corrugated paper, iron yoke insulation, clamp insulation and end-insulation winding clamps for cake-type windings.
8 Insulation tubes: Insulation tubes used in transformers include phenolic paper tube, epoxy glass cloth tube, glass fiber reinforced plastic tube and cardboard tube.
9 Corrugated cardboard: In the oil plate gap structure composed of multi-layer paper cylinders of high-voltage transformers, corrugated cardboard can be used instead of braces to form oil gaps. This insulation structure can save insulation materials on the basis of ensuring insulation performance.
10 Electrical laminates: Laminated insulation materials made of paper, cloth, and wooden veneer as substrates, dip-coated with different adhesives, and heat-pressed or rolled.
11 Nomex paperboard: A paperboard made from synthetic materials based on aramid fibers.
12 Pull-out rods: Glass-fiber pull-out rods are often used in the inter-stage rods, air-gap braces, screws and screws of dry-type transformer cores.
13 Electrical thin molds and electrical composite materials: They have excellent dielectric properties and belong to sheet insulation materials. Electrical films include polypropylene film, polyester film, and polyimide film. Composite material is a composite product made of one side or both sides of a film and a fibrous material.
14 Glass varnished cloth: The glass varnished cloth is made of electric-free alkali-free glass cloth impregnated with insulating varnish and baked. For dry-type transformers.
15 Insulation materials for transformer binding: Insulation materials for transformer binding include cotton tape, shrink tape, semi-dry thin wire tape, mesh semi-dry weft-free tape, glass cloth tape and polyester rope.
