CN-121980863-A - High-voltage direct-current cable degassing time judging method based on crosslinking byproduct migration and application

CN121980863ACN 121980863 ACN121980863 ACN 121980863ACN-121980863-A

Abstract

The application relates to the technical field of power cables, and particularly discloses a high-voltage direct-current cable degassing time judging method based on migration of crosslinking byproducts and application thereof. According to the method, a degassing time prediction model containing a specific coefficient is constructed around the external specific surface area parameter of the crosslinked high-voltage direct-current cable insulating layer, only the geometric parameters of the inner diameter and the outer diameter of the cable insulating layer are required to be obtained through the model, and the shortest degassing time required by the high-voltage direct-current cable can be directly deduced after the external specific surface area of the insulating layer is obtained through calculation. The judging method provided by the application simplifies the calculation flow of the degassing time, does not need to introduce complex interference parameters such as material components, process environment and the like, has good suitability for direct-current cables with different radial dimensions, can realize unified judgment of the degassing time of the cross-specification cable, and solves the technical bottlenecks that the existing degassing time judging technology is complex and difficult to accurately judge the degassing time.

Inventors

Zhan Yunpeng
Ying Xipeng
FU MINGLI
Hou shuai
HUI BAOJUN
ZHU WENBO
LI YANFEI
FAN LINGMENG
FENG BIN
CHEN YUN
LIU JIE

Assignees

南方电网科学研究院有限责任公司
中国南方电网有限责任公司

Dates

Publication Date: 20260505
Application Date: 20260123

Claims (10)

1. The method for judging the degassing time of the high-voltage direct-current cable based on the migration of the crosslinking byproducts is characterized by comprising the following steps of: S1, constructing a migration diffusion model of a cross-linked byproduct in the radial direction of a high-voltage direct-current cable according to a Fick diffusion law; Step S2, degassing the high-voltage direct current cable, and synchronously detecting the initial concentration of the crosslinking byproducts, the arc length of the electric branches in the radial direction of the high-voltage direct current cable, the concentration of the crosslinking byproducts when the electric branches stop growing, and the concentration of the crosslinking byproducts when the electric branches stop growing as a threshold concentration; s3, substituting the degassing time, the initial concentration of the crosslinking byproducts, the threshold concentration of the crosslinking byproducts and the arc length of the electric branches in the radial direction of the high-voltage direct-current cable into the migration diffusion model constructed in the step S1 to obtain the diffusion coefficient of the crosslinking byproducts; And S4, carrying out a degassing simulation experiment on the high-voltage direct-current cable by using finite element simulation software in combination with the diffusion coefficient of the crosslinking byproducts, the initial concentration of the crosslinking byproducts and the threshold concentration of the crosslinking byproducts to obtain a relation curve between the degassing time and the specific surface area outside the insulating layer, and adopting Levenberg-Marquardt fitting to calculate the relation curve to obtain a degassing time prediction model.
2. The method for determining the degassing time of a high-voltage direct-current cable based on migration of a crosslinking byproduct according to claim 1, wherein a migration diffusion model of the crosslinking byproduct in a radial direction of the high-voltage direct-current cable is as follows: Formula (1); In the formula (1), C represents the concentration of the crosslinking by-product at the radius r at the time t, D represents the diffusion coefficient, r represents the radial coordinate, and t represents the diffusion time.
3. The method for determining the degassing time of the high-voltage direct-current cable based on migration of crosslinking byproducts according to any one of claims 1 to 2, wherein the method is characterized by comprising the following steps of: The rated voltage of the high-voltage direct-current cable is 100 kV-500 kV; the inner diameter of the high-voltage direct-current cable insulating layer is 25 mm-70 mm, the outer diameter is 35 mm-100 mm; the crosslinking byproducts comprise at least one of acetophenone, alpha-methylstyrene, cumyl alcohol.
4. The method for determining the degassing time of the high-voltage direct-current cable based on migration of crosslinking byproducts according to any one of claims 1 to 3, wherein the method is characterized by comprising the following steps of: In the degassing simulation experiment, a physical field model is a dilute substance transfer model, the simulation temperature is set to be 30-70 ℃, and the simulation termination condition is that the concentration of the crosslinking by-product in the radial direction of the insulating layer is lower than a threshold concentration.
5. The method for determining the degassing time of a high-voltage direct-current cable based on migration of crosslinking by-products according to claim 4, wherein: In the degassing simulation experiment, finite element simulation software is adopted to establish a simulation model, the simulation model comprises an insulating layer and an air layer, wherein the air layer is a cylindrical area with the outer surface of the insulating layer expanding outwards by 8 mm-12 mm, the insulating layer is divided by adopting a free triangle mesh, the maximum cell is smaller than or equal to 1.2mm, the minimum cell size is larger than or equal to 0.03mm, the air layer is divided by adopting a free triangle mesh, and the maximum cell is smaller than or equal to 140mm, and the minimum cell size is larger than or equal to 0.5mm.
6. The method for determining the degassing time of a high-voltage direct-current cable based on migration of crosslinking byproducts according to claim 1, wherein: In the degassing simulation experiment, a physical field model is a dilute substance transfer model, the simulation temperature is set to be 30-70 ℃, and the simulation termination condition is that the concentration of the crosslinking by-product in the radial direction of the insulating layer is lower than a threshold concentration.
7. The method for determining the degassing time of the high-voltage direct-current cable based on the migration of the crosslinking by-products according to claim 1, wherein the degassing time prediction model is shown in formula (2), and the degassing time of the high-voltage direct-current cable is calculated by using the degassing time prediction model shown in formula (2): formula (2); In formula (2), T 1 represents the shortest degassing time required when the concentration of the crosslinking by-product is lower than the threshold concentration, and S' represents the specific surface area outside the insulating layer.
8. The method for determining the degassing time of the high-voltage direct current cable based on the migration of the crosslinking byproducts according to claim 7, wherein the specific surface area outside the insulating layer is a ratio of the surface area of the outer insulating layer to the volume of the insulating layer of the direct current cable per unit length, and the specific surface area outside the insulating layer is calculated by the following formula: Formula (3); in the formula (3), S' represents the specific surface area outside the insulating layer, D represents the outer diameter of the insulating layer, and D represents the inner diameter of the insulating layer.
9. The high-voltage direct-current cable degassing time judging system is characterized by comprising a data input module, a data processing module and a data output module; the data input module is used for inputting the outer diameter of an insulating layer and the inner diameter of the insulating layer of the high-voltage direct-current cable; The data processing module comprises the degassing time prediction model according to any one of claims 7-8, and is used for receiving parameters of the outer diameter of the insulating layer and the inner diameter of the insulating layer, and performing operation processing by using the degassing time prediction model to obtain the shortest degassing time; The data output module is used for displaying or transmitting the shortest degassing time.
10. A degassing treatment system for a high-voltage direct-current cable, comprising the degassing time prediction model according to any one of claims 7 to 8 or the high-voltage direct-current cable degassing time determination system according to claim 9.

Description

High-voltage direct-current cable degassing time judging method based on crosslinking byproduct migration and application Technical Field The application relates to the technical field of power cables, in particular to a high-voltage direct-current cable degassing time judging method based on migration of crosslinking byproducts and application thereof. Background Crosslinked polyethylene (XLPE) insulated high voltage dc cable is a key electrical equipment for new energy development, and is industrially produced mainly by initiating chemical crosslinking of Linear Low Density Polyethylene (LLDPE) with dicumyl peroxide (DCP). The DCP has low decomposition temperature and high crosslinking efficiency, can form a uniform crosslinked grid structure, and is an ideal chemical crosslinking agent. During the crosslinking reaction, DCP produces polar byproducts such as acetophenone, cumyl alcohol, and alpha-methylstyrene. The residual of these byproducts in the cable insulation layer can significantly affect the space charge distribution, which may lead to distortion of the electric field under the high voltage dc electric field, induce growth of electrical branches and partial discharge, and threaten the long-term operation reliability of the cable. Therefore, in the cable manufacturing process, it is necessary to reduce or remove these crosslinking byproducts by a heating degassing process. Currently, the determination of the degassing process time in industrial production is generally dependent on empirical settings or fumbling through a large number of experiments. The method mainly has the following defects that firstly, a unified and quantitative judging standard is lacking, the degassing endpoint is difficult to accurately determine, insufficient degassing or excessive degassing possibly occurs, and secondly, the degassing time is closely related to the geometric dimension of a cable insulating layer, and the existing method is difficult to establish a universal degassing time prediction model applicable to cables with different specifications, so that repeated tests are needed for developing a new specification product, and the efficiency is low. How to establish a generalized method capable of accurately and efficiently judging the degassing time of a high-voltage direct-current cable and being applicable to different cable specifications is a technical problem to be solved in the field. Disclosure of Invention In view of the above, the present application aims to provide a method for determining degassing time of a high voltage dc cable based on migration of crosslinking byproducts and an application thereof, which are used for solving the technical bottleneck that the existing degassing time determination technology is complex and difficult to accurately determine the degassing time. In order to achieve the technical aim, the application provides a high-voltage direct-current cable degassing time judging method based on migration of crosslinking byproducts, which comprises the following steps: S1, constructing a migration diffusion model of a cross-linked byproduct in the radial direction of a high-voltage direct-current cable according to a Fick diffusion law; Step S2, degassing the high-voltage direct-current cable, and synchronously detecting the initial concentration of the crosslinking byproducts, the arc length of the electric branch in the radial direction of the high-voltage direct-current cable, the concentration of the crosslinking byproducts when the electric branch stops growing, and the concentration of the crosslinking byproducts when the electric branch stops growing as a threshold concentration; S3, substituting the degassing time, the initial concentration of the crosslinking byproducts, the threshold concentration of the crosslinking byproducts and the arc length of the electric branches in the radial direction of the high-voltage direct-current cable into the migration diffusion model constructed in the step S1 to obtain the diffusion coefficient of the crosslinking byproducts; And S4, carrying out a degassing simulation experiment on the high-voltage direct-current cable by using finite element simulation software in combination with the diffusion coefficient of the crosslinking byproducts, the initial concentration of the crosslinking byproducts and the threshold concentration of the crosslinking byproducts to obtain a relation curve between the degassing time and the specific surface area outside the insulating layer, and adopting Levenberg-Marquardt fitting calculation relation curve to obtain a degassing time prediction model. Further, the migration diffusion model of the crosslinking by-product in the radial direction of the high voltage direct current cable is as follows: Formula (1); In the formula (1), C represents the concentration of the crosslinking by-product at the radius r at the time t, D represents the diffusion coefficient, r represents the radial coordinate, and t rep