Transformer insulation material is one of the most important materials in the transformer, and its performance and quality directly affect the reliability of the transformer operation and the service life of the transformer. In recent years, new insulating materials used in transformer products have emerged one after another.
With the rapid development of science and technology, electrical equipment such as motors and transformers are increasingly used. The reliability and service life of transformers depend to a large extent on the insulating materials used. Insulating materials are increasingly valued by those engaged in transformer design and manufacturing.
Insulating materials, also called dielectrics, are materials with high resistivity and low conductivity. Insulating materials can be used to isolate live conductors or conductors of different potentials, so that current flows in a certain direction. In transformer products, insulating materials also play a role in heat dissipation, cooling, support, fixation, arc extinguishing, improvement of potential gradient, moisture-proof, mildew-proof and conductor protection. Insulation materials are classified according to voltage levels: generally divided into: Y (90℃), A (105), E (120℃), B (130℃), F (155℃), H (180℃), C (greater than 180
There are many types of insulating parts for transformers. Many insulating materials are needed to manufacture transformer insulation. Insulating materials are used in transformers to isolate conductive parts from each other and between conductive parts and ground (zero potential). The stable technical performance of the insulating material plays an important role in the stable operation reliability of the transformer and the service life of the transformer.
As an important part of transformers, insulating materials must have reasonable insulation and mechanical properties that can effectively achieve high compressive strength, high tensile strength and bending strength. And its elastic deformation can be ignored. However, due to the different roles and geometric shapes of insulating parts in transformers, common insulating materials used in oil-immersed transformers electrical insulation pressboard, ddp insulation paper,cable paper, electrical crepe paper, and epoxy glass cloth laminated sheet.
Electrical insulation paperboard is made of 100% pure sulphate wood pulp. It can be thoroughly dried, degassed and oiled through vacuum drying. It has good electrical and mechanical properties and is the most commonly used insulating material in oil-immersed transformers. The heat-resistant grade of the insulating paperboard is Y grade, which becomes A grade after being immersed in oil.
Depending on the thickness, insulating paperboard has different specifications such as 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, etc. According to different formats, insulating paperboards include 1000mm×2000mm, 2030mm×4200mm, 2100mm×3200mm, 3200×4200mm, 3200×6100mm, etc. According to the density, it can be divided into low density cardboard, medium density cardboard and high density cardboard. Among them, the density of low-density paperboard is 0.75～0.9g/cm3, and the strength is low. The mechanical properties are poor, but the formability is mainly used to make molded parts. Medium-density paperboard is also called standard board, with a density of 0.95-1.15g/cm3, good hardness and high electrical strength. It is mainly used for insulating paper tubes, stays, spacers and other general insulating parts and laminated products. High-density paperboard has a density of 1.15～1.3g/cm3, with high electrical and mechanical properties. It is mainly used for non-bending parts such as pressing plates, pads, and oil gap pads.
Diamond dotted Insulation Paper is made of electrical grade Insulating paper coated with B-stage heat curable epoxy resin on either or both sides. The base paper is made from unbleached 100% Sulfate kraft pulp.
The epoxy resin is applied on base paper in diamond pattern, which is consisted of 9.5mm x 9.5mm diamonds with 15.9mm center spacing.
Diamond dotted paper has good dielectric properties and mechanical properties after being heat solidified.The Diamond Dotted Paper to be used in oil immersed transformers, for coil insulation. On the insulation layer, there is a layer dotted epoxy resin that will be changed with high temperature change that is to be called as felt.
The cable paper commonly used in transformers is made of pure sulphate wood pulp. Cable paper has high mechanical strength and electrical strength. Cable paper is mainly used for turn insulation and laminated insulation of transformer winding wires, as well as lead wires, branch wires, electrostatic ring insulation, and rolled insulation tubes.
Insulating crepe paper is made by corrugating insulating paper for electricians. There are wrinkles along the transverse direction, and the wrinkles are pulled apart during use. Due to different creping processing procedures, crepe paper with different elongation can be made. Crepe paper is often used for transformer wrapping insulation, such as insulation wrapping of winding heads, leads, and electrostatic rings.
Epoxy glass cloth sheet is made by heating and pressing glass fiber cloth with epoxy resin. It has high mechanical performance at medium temperature and stable electrical performance at high temperature. It has high mechanical and dielectric properties, good heat resistance and moisture resistance. Mainly used to make the oil passage between the frames and the adjusting piece for the final assembly.
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