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CN-122025314-A - DC composite insulator umbrella cover with double-gradient structure, preparation process and composite insulator

CN122025314ACN 122025314 ACN122025314 ACN 122025314ACN-122025314-A

Abstract

The invention relates to the technical field of high-voltage direct-current transmission equipment, and discloses a direct-current composite insulator umbrella cover with a double-gradient structure, a preparation process and a composite insulator, wherein the umbrella cover is of a three-layer composite structure and sequentially comprises a high-resistivity inner layer, a high-dielectric middle layer and a micro-conductive outer layer from inside to outside, the volume resistivity of the high-resistivity inner layer is larger than 1X 10 13 Ω & m, the thickness of the high-resistivity inner layer is 10% -20% of the total thickness of the umbrella cover, the volume resistivity of the high-dielectric middle layer is 1X 10 10 ～1×10 12 Ω & m, the relative dielectric constant is 15% -25, the thickness of the micro-conductive outer layer is 60% -80% of the total thickness of the umbrella cover, the volume resistivity of the micro-conductive outer layer is 1X 10 8 ～1×10 10 Ω & m, the relative dielectric constant is 5% -8, and the thickness of the micro-conductive outer layer is 5% -20% of the total thickness of the umbrella cover. The invention can solve the technical problems of uneven electric field distribution and easy accumulation of surface charges of the umbrella cover of the existing epoxy hard composite insulator, and realize autonomous regulation and control of the electric field in the insulator and rapid discharge of the surface charges.

Inventors

  • LIU SHIZENG
  • ZHANG SHIHONG
  • ZHANG HUACHENG
  • YU WENBIN
  • YUAN YIDI
  • YAN SHICHENG
  • DONG XUEXING
  • E XIANZHONG
  • LIU BINGNAN
  • LI JIANGMING
  • YANG WEIWEI
  • QIU YOUQIANG
  • ZHENG WULUE
  • ZHENG YANGLIANG
  • GUO CHUNHAI
  • LI QIANG
  • YU JINYUN
  • WANG ANJUN
  • HE TONGBO
  • YANG YANG
  • ZHANG CHENKAI
  • MA YIGANG

Assignees

  • 中国南方电网有限责任公司超高压输电公司大理局

Dates

Publication Date
20260512
Application Date
20260403

Claims (10)

  1. 1. The DC composite insulator umbrella cover with the double-gradient structure is characterized by comprising a three-layer composite structure, wherein the three-layer composite structure comprises a high-resistivity inner layer, a high-dielectric middle layer and a micro-conductive outer layer from inside to outside in sequence; The material of the high-resistivity inner layer comprises an epoxy resin matrix and reinforcing fibers, the volume resistivity of the high-resistivity inner layer is larger than 1 multiplied by 10 13 omega-m, and the thickness of the high-resistivity inner layer is 10% -20% of the total thickness of the umbrella cover; The material of the high dielectric middle layer comprises an epoxy resin matrix and a high dielectric inorganic filler, the volume resistivity of the high dielectric middle layer is 1 multiplied by 10 10 ～1×10 12 omega-m, the relative dielectric constant is 15-25, and the thickness is 60-80% of the total thickness of the umbrella cover; The material of the micro-conductive outer layer comprises an epoxy resin matrix and a conductive filler, the volume resistivity of the micro-conductive outer layer is 1 multiplied by 10 8 ～1×10 10 omega-m, the relative dielectric constant is 5-8, and the thickness is 5-20% of the total thickness of the umbrella cover.
  2. 2. The direct current composite insulator umbrella cover with the dual gradient function structure according to claim 1, wherein the reinforcing fiber is one or more selected from glass fiber, basalt fiber and carbon fiber.
  3. 3. The direct current composite insulator umbrella cover with the dual-gradient functional structure according to claim 1, wherein the high-dielectric inorganic filler is one or more selected from barium titanate, calcium titanate, aluminum oxide and lead zirconate titanate.
  4. 4. The direct current composite insulator umbrella cover with the dual-gradient functional structure according to claim 1, wherein the conductive filler is one or more selected from the group consisting of carbon nanotubes, surface modified carbon black and graphite.
  5. 5. The direct current composite insulator umbrella cover with the dual-gradient functional structure according to claim 1, wherein the content of the reinforcing fiber in the high-resistivity inner layer is 20-30wt%.
  6. 6. The direct current composite insulator umbrella cover with the dual-gradient functional structure according to claim 1, wherein the total content of the high dielectric inorganic filler in the high dielectric middle layer is 25-40 wt%.
  7. 7. The direct current composite insulator umbrella cover with the dual-gradient functional structure according to claim 1, wherein the total content of the conductive filler in the micro-conductive outer layer is 5-10wt%.
  8. 8. A process for preparing the direct current composite insulator umbrella cover with the double-gradient structure as claimed in any one of claims 1 to 7, which is characterized by comprising the following steps: s1, pre-treating a die, namely coating a high-temperature release agent on the inner surface of a metal die; S2, constructing a high-resistivity inner layer, namely forming a composite layer formed by the material of the high-resistivity inner layer outside the core rod serving as a framework by adopting a vacuum infusion method or a prepreg coating process, and performing hot pressing and curing; s3, constructing a high dielectric middle layer, namely placing the component obtained in the step S2 into a mould, uniformly coating a layer of high dielectric middle layer material on the outer surface of the component through a centrifugal casting process, and performing pregelatinization; S4, constructing a micro-conductive outer layer, namely coating the material of the micro-conductive outer layer on the surface of the middle layer pre-gelled in the step S3 through a centrifugal casting process; s5, step heating and curing, namely synchronously curing the component obtained in the step S4 by adopting a step heating program; and S6, post-treatment, namely demoulding after solidification, deburring and surface polishing to obtain the DC composite insulator umbrella cover with the double-gradient structure.
  9. 9. The manufacturing process according to claim 8, wherein the step-up temperature program in step S5 is: the step heating program is that the temperature is kept for 1-3 h at 90-110 ℃, 1-3 h at 110-130 ℃ and 3-5 h at 130-150 ℃.
  10. 10. The composite insulator comprises a core rod, hardware fittings arranged at two ends of the core rod, and an umbrella skirt and an umbrella cover which are coated outside the core rod, and is characterized in that the umbrella cover is the DC composite insulator umbrella cover with the double-gradient structure as claimed in any one of claims 1-7.

Description

DC composite insulator umbrella cover with double-gradient structure, preparation process and composite insulator Technical Field The invention relates to the technical field of high-voltage direct-current transmission equipment, in particular to a direct-current composite insulator umbrella cover with a double-gradient structure, a preparation process and a composite insulator. Background With the development of the hvdc technology to higher voltage class and larger transmission capacity, ±500 kV and above lines have become key components of the backbone grid of the power grid, and they have made unprecedented demands on the performance of the insulating materials of the key equipment of the lines. The insulator not only needs to bear huge mechanical load to ensure the mechanical stability of the circuit, but also must have excellent electrical performance to cope with unique challenges under the direct current electric field. At present, the prior art mainly depends on two measures, namely that firstly, high-dielectric-constant silicon rubber materials are adopted to manufacture umbrella skirts to adjust potential distribution, but the mechanical strength of the materials is often insufficient, the severe requirements on rigidity and creep resistance of structural members of extra-high voltage lines are difficult to meet, and secondly, an equalizing ring is additionally arranged, however, the equalizing effect in a direct-current field is limited, and the size, the weight and the cost of the equalizing ring are exponentially increased along with the voltage level, so that huge structural load and installation problems are brought. In contrast, epoxy materials exhibit the potential to be ideal alternatives due to their excellent mechanical strength, dimensional stability and weatherability. However, when the high volume resistivity is directly applied to a direct current insulator, dissipation of surface charges is hindered by the extremely high volume resistivity, so that charges are continuously accumulated, severe distortion of an electric field is caused, and the risk of partial discharge is increased, so that the direct application of the high volume resistivity in the direct current insulation field is limited. In order to improve the electric field distribution of the epoxy resin insulator, methods of homogenizing and modifying materials (such as adding functional fillers to adjust overall electrical parameters) or applying surface coatings and the like are mostly adopted in the prior art. However, the former often has difficulty in achieving multiple performances, and cannot achieve active and fine regulation of the electric field, and the latter is often limited by interface reliability. Therefore, it is needed to provide a dc composite insulator umbrella cover, a manufacturing process and a composite insulator to solve the problems of uneven electric field distribution and charge accumulation of the epoxy-based insulator in the dc electric field. Disclosure of Invention The invention aims to provide a direct current composite insulator umbrella cover with a dual-gradient function structure, a preparation process thereof and a composite insulator adopting the umbrella cover, so as to solve the technical problems of uneven electric field distribution and easy accumulation of surface charges of the existing epoxy hard composite insulator umbrella cover and realize autonomous regulation and control of an electric field in an insulator and rapid discharge of the surface charges. In order to achieve the above object, the present invention provides the following technical solutions: the DC composite insulator umbrella cover with the double-gradient structure is of a three-layer composite structure and sequentially comprises a high-resistivity inner layer, a high-dielectric middle layer and a micro-conductive outer layer from inside to outside; The material of the high-resistivity inner layer comprises an epoxy resin matrix and reinforcing fibers, the volume resistivity of the high-resistivity inner layer is larger than 1 multiplied by 10 13 omega-m, and the thickness of the high-resistivity inner layer is 10% -20% of the total thickness of the umbrella cover; The material of the high dielectric middle layer comprises an epoxy resin matrix and a high dielectric inorganic filler, the volume resistivity of the high dielectric middle layer is 1 multiplied by 10 10～1×1012 omega-m, the relative dielectric constant is 15-25, and the thickness is 60-80% of the total thickness of the umbrella cover; The material of the micro-conductive outer layer comprises an epoxy resin matrix and a conductive filler, the volume resistivity of the micro-conductive outer layer is 1 multiplied by 10 8～1×1010 omega-m, the relative dielectric constant is 5-8, and the thickness is 5-20% of the total thickness of the umbrella cover. The existing hard epoxy insulator has the problems of uneven electric field distribution and high sur