CN-121976430-A - Composite insulating paper and preparation method and application thereof

CN121976430ACN 121976430 ACN121976430 ACN 121976430ACN-121976430-A

Abstract

The invention discloses composite insulating paper, a preparation method and application thereof, and relates to the technical field of electric insulating materials. The composite insulating paper comprises a plurality of insulating cellulose papers which are sequentially laminated, wherein the relative dielectric constant of each layer of insulating cellulose paper gradually increases or decreases layer by layer along the thickness direction of the composite insulating paper, the relative dielectric constant difference between any two adjacent layers of insulating cellulose paper is 0.2-0.5, and the maximum relative dielectric constant difference between the plurality of insulating cellulose papers in the composite insulating paper is 0.5-1.5. By setting the structure of dielectric constant gradient transition, the invention can artificially regulate and control electric field distribution, so that the surface of the insulating paper close to the conductor has higher dielectric constant, and the surface of the insulating paper far away from the conductor has lower dielectric constant, thereby the dielectric constant related to the oilpaper insulating system can present a gentle gradient transition trend, and the possibility of insulation failure is reduced.

Inventors

QIAN YIHUA
WANG QING
ZHAO YAOHONG
ZHAO YIFENG
PENG LEI

Assignees

广东电网有限责任公司电力科学研究院

Dates

Publication Date: 20260505
Application Date: 20260313

Claims (10)

1. The composite insulating paper is characterized by comprising a plurality of insulating cellulose papers which are sequentially laminated, wherein the relative dielectric constant of each layer of insulating cellulose paper gradually increases or decreases layer by layer along the thickness direction of the composite insulating paper, the relative dielectric constant difference between any two adjacent layers of insulating cellulose papers is 0.2-0.5, and the maximum relative dielectric constant difference between the plurality of insulating cellulose papers in the composite insulating paper is 0.5-1.5.
2. The composite insulating paper according to claim 1, wherein the single-layer insulating cellulose paper has a relative dielectric constant of 2.8 to 4.0.
3. The composite insulating paper according to claim 1 or 2, wherein the single-layer insulating cellulose paper has a relative dielectric constant of at least 2.8 to 3.1 and/or the single-layer insulating cellulose paper has a relative dielectric constant of at most 3.7 to 4.0.
4. The composite insulating paper according to claim 1 or 2, wherein the composite insulating paper comprises 2 to 5 layers of insulating cellulose paper which are sequentially laminated.
5. The composite insulating paper according to claim 1, comprising at least one of the following (1) to (4): (1) The paper ration of the composite insulating paper is 150-200 g/m 2 ; (2) The thickness of the composite insulating paper is 0.2-0.5 mm; (3) The paper ration of the single-layer insulating cellulose paper is 30-100 g/m 2 ; (4) The thickness of the single-layer insulating cellulose paper is 0.04-0.16 mm.
6. The composite insulating paper according to claim 1, wherein the composite insulating paper comprises a first layer, a second layer and a third layer which are laminated in this order, the relative dielectric constant of the first layer is 2.8-3.1, the relative dielectric constant of the second layer is 3.2-3.5, and the relative dielectric constant of the third layer is 3.7-4.0.
7. The composite insulating paper according to claim 6, comprising at least one of the following (1) to (9): (1) The thickness of the first layer is 0.05-0.08 mm; (2) The basis weight of the first layer of paper is 30-50 g/m 2 ; (3) The preparation raw materials of the first layer comprise aramid fiber and/or softwood pulp; (4) The thickness of the second layer is 0.08-0.10 mm; (5) The basis weight of the second layer is 50-70 g/m 2 ; (6) The preparation raw materials of the second layer comprise at least one of aramid fiber, softwood pulp and inorganic fiber; (7) The thickness of the third layer is 0.12-0.15 mm; (8) The basis weight of the paper of the third layer is 70-90 g/m 2 ; (9) The third layer is prepared from softwood pulp and/or cotton pulp.
8. The method for preparing the composite insulating paper according to any one of claims 1 to 7, comprising the steps of: Preparing each layer of insulating cellulose paper wet paper web by a papermaking mode, compounding each layer of insulating cellulose paper wet paper web according to the sequence of relative dielectric constants, applying 20-30 kHz of ultrasound, then pressing under the pressure of 0.1-0.5 MPa, and finally drying to obtain the composite insulating paper.
9. An oiled paper insulation system comprising the composite insulation paper of any one of claims 1-7 and an insulation oil.
10. Use of the oilpaper insulation system of claim 9 in an oil immersed transformer.

Description

Composite insulating paper and preparation method and application thereof Technical Field The invention relates to the technical field of electrical insulation materials, in particular to composite insulation paper and a preparation method and application thereof. Background With the development of productivity, the demand of people for electric power in daily life is also gradually increasing. In a huge power system, an oil-immersed transformer is a core for transporting and distributing power, and in order to avoid power loss during the operation of the transformer, an insulation system is usually required to be introduced outside the power transmission structure for improving the safety. For a power transformer, the aging failure of an internal insulation system is a main cause of a transformation fault, and the failure of solid insulation is irreversible, so that the performance of the insulation system directly determines the operational reliability and service life of the transformer. The oil-paper insulating system formed by dipping insulating paper in insulating oil is a main insulating structure in the current oil-immersed power transformer, and a large amount of oil-paper combined system formed by insulating oil and insulating paper exists among turns of windings, interphase, paper board barriers, conductors, cushion blocks and the like in the oil-immersed power transformer. However, in conventional oiled paper insulation systems, natural lignocellulosic fiber paper, such as unbleached kraft pulp paper, is often used as the insulation paper. The relative dielectric constant of the cellulose insulating paper is about 5.1-6.5 (20 ℃ C., 50 Hz) which is more than 2 times that of the insulating mineral oil (the relative dielectric constant of the mineral oil is about 2.2), and the mismatch of the dielectric constants leads to the formation of a high-field strong region of the insulating paper under the strong electric field of winding end parts, lead corners, the vicinity of metal burrs and the like, and the local discharge and even early breakdown are induced. Thus, most of the current research is focused on the aspect of lowering the dielectric constant of the insulating paper. In recent years, with the development of environment-friendly transformers, natural or synthetic ester insulating oils with higher relative dielectric constants (typically between 3.0 and 3.3) are increasingly used in transformers. For the ester insulating oil system, if the relative dielectric constant of the insulating paper is too low (for example, lower than 2.5), a serious insulating crisis is caused, namely, the too low dielectric constant indicates that the surface of the material is weak in polarity, so that the wettability between the material and the ester insulating oil with stronger polarity is poor, a large number of tiny air gaps remain at an oil-paper microcosmic interface, and strong partial discharge is caused, so that the insulation is too early to fail, and meanwhile, the dielectric constant of the insulating paper is lower than that of the insulating oil, so that the electric field stress originally born by the solid insulating paper is concentrated to weak oil gaps or air gaps in the insulating system, and the overall voltage withstanding level of the transformer is seriously weakened. Therefore, simply lowering the dielectric constant of the insulating paper cannot meet the requirements of the high dielectric constant ester oil paper insulating system, and an insulating paper capable of adapting to the ester insulating oil system must be developed. Disclosure of Invention In order to solve the defects in the prior art, the invention provides the composite insulating paper, the preparation method and the application thereof, and the electric field distribution is manually regulated, so that the surface of the insulating paper close to a conductor has higher dielectric constant, and the surface of the insulating paper far away from the conductor has lower dielectric constant, so that the dielectric constant related to an oil paper insulating system can present a gentle gradient transition trend, and the possibility of insulation failure is reduced. Another object of the present invention is to provide a oiled paper insulation system. It is a further object of the present invention to provide the use of a oiled paper insulation system. The above object of the present invention is achieved by the following technical scheme: The composite insulating paper comprises a plurality of insulating cellulose papers which are sequentially laminated, wherein the relative dielectric constant of each layer of insulating cellulose paper gradually increases or decreases layer by layer along the thickness direction of the composite insulating paper, the relative dielectric constant difference between any two adjacent layers of insulating cellulose paper is 0.2-0.5, and the maximum relative dielectric constant difference betw