A method and system for evaluating the electrical thermal degradation of 500kv pumped storage high voltage cable gold cloth

Abstract

This invention discloses a method and system for assessing the electrothermal degradation of the gold-coated fabric in 500kV pumped-storage high-voltage cables. The method includes the following steps: establishing a four-level gold-coated fabric degradation standard and a comprehensive degradation degree calculation model; classifying the four-level gold-coated fabric degradation standard based on the variation law of gold-coated fabric morphological characteristic parameters with the degree of degradation; constructing the comprehensive degradation degree calculation model based on the correlation analysis results of gold-coated fabric electrical characteristic parameters, gold-coated fabric morphological characteristic parameters, and the degree of gold-coated fabric degradation; obtaining the measured values ​​of the electrical and morphological characteristic parameters of the gold-coated fabric body and interface to be assessed; inputting the measured values ​​of each characteristic parameter into the comprehensive degradation degree calculation model to calculate the comprehensive degradation degree of the gold-coated fabric; and determining the current gold-coated fabric degradation level and the corresponding buffer layer defect stage based on the comprehensive degradation degree of the gold-coated fabric, in accordance with the four-level gold-coated fabric degradation standard. This invention achieves a multi-dimensional and objective quantitative assessment of the electrothermal degradation degree of the gold-coated fabric in pumped-storage high-voltage cables.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage cable condition assessment technology, specifically, it relates to a method and system for assessing the electrothermal degradation of gold-coated fabric in 500kV pumped-storage high-voltage cables. Background Technology

[0002] Pumped storage power stations play a role in peak shaving and frequency regulation in the power system, requiring rapid responses to power demand. Therefore, power transmission in pumped storage power stations fluctuates frequently. Under these conditions, high-voltage cables bear periodically fluctuating currents for extended periods. When alternating current flows through the gold-coated cable, it continuously generates Joule heating. Simultaneously, the gold-coated cable, tightly attached to the insulating shielding layer, is exposed to a power frequency electric field. The electric and temperature fields, through coupling, degrade the gold-coated cable, causing changes in related electrical parameters such as the DC resistance of the cable itself and the contact resistance at the interface between the gold-coated cable and the aluminum sheath. In severe cases, this can lead to partial discharge, localized overheating, or even insulation breakdown.

[0003] Currently, there are few methods for assessing the degradation of high-voltage cable gold inlays, and these methods have certain shortcomings: First, most assessment methods use infrared thermography and partial discharge methods to determine cable defects, rather than considering the degree of gold inlay degradation; second, some methods lack quantification of the degradation degree, making it difficult to accurately assess the extent of gold inlay degradation and thus hindering the implementation of corresponding maintenance strategies; third, they rely on single parameters such as the DC resistance or capacitance of the gold inlay itself to assess the degree of degradation; finally, pumped-storage high-voltage cables differ from cables operating in other environments, and existing methods lack consideration for the frequent alternation of cable loads. Therefore, there is an urgent need for a multi-parameter electrothermal degradation assessment method specifically for pumped-storage high-voltage cable gold inlays. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and provide a method for evaluating the electrothermal degradation of the gold cloth in 500kV pumped storage high-voltage cables, which realizes a multi-dimensional and objective quantitative evaluation of the degree of electrothermal degradation of the gold cloth in pumped storage high-voltage cables.

[0005] The objective of this invention is achieved through the following technical solution: a method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable, comprising the following steps:

[0006] S1. Establish a four-level standard for the degradation of gold-coated fabric and a comprehensive degradation calculation model in advance; the four-level standard for the degradation of gold-coated fabric is based on the variation law of the morphological characteristic parameters of gold-coated fabric with the degree of degradation; the comprehensive degradation calculation model is constructed based on the correlation analysis results of the electrical characteristic parameters and morphological characteristic parameters of gold-coated fabric with the degree of degradation of gold-coated fabric.

[0007] S2. Obtain the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated;

[0008] S3. Input the measured values ​​of each characteristic parameter into the comprehensive degradation calculation model to calculate the comprehensive degradation degree of the gold fabric;

[0009] S4. Based on the overall deterioration degree of the gold fabric, determine the current deterioration level of the gold fabric and the corresponding buffer layer defect stage by referring to the four-level gold fabric deterioration level standard.

[0010] Preferably, in step S1, the four levels of gold fabric degradation include Level I normal state, Level II early degradation, Level III mid-term degradation, and Level IV severe degradation; the correspondence between the overall degradation degree of the gold fabric and the four levels of gold fabric degradation is as follows: 0≤D≤0.2 corresponds to Level I normal state, 0.2<D≤0.5 corresponds to Level II early degradation, 0.5<D≤0.8 corresponds to Level III mid-term degradation, and 0.8<D≤1 corresponds to Level IV severe degradation, where D represents the overall degradation degree of the gold fabric.

[0011] Preferably, in step S1, the Level I normal state corresponds to no obvious local contact defects and the copper wire braiding remains intact; the Level II early deterioration corresponds to slight oxidation or wear of local copper wires and slight loosening of the braiding structure; the Level III mid-term deterioration corresponds to obvious wear or local cross-sectional changes of copper wires and a combination of local loosening and compaction of the braiding structure; and the Level IV severe deterioration corresponds to broken or severely deformed copper wires and a severely loose or even partially disintegrated braiding structure.

[0012] Preferably, the comprehensive degradation calculation model is as follows:

[0013] ,

[0014] Where D represents the overall degradation degree of the gold-plated fabric, with a value ranging from 0 to 1; w i d represents the weighting coefficient of the i-th feature parameter; i is the relative degradation deviation value of the i-th feature parameter, with a value range of 0 to 1.

[0015] Preferably, the formula for calculating the relative degradation deviation value is:

[0016]

[0017] Where V is the current measured value of the characteristic parameter; V0 is the factory reference value of the characteristic parameter.

[0018] Preferably, the weighting coefficients are determined based on the correlation between each feature parameter and the degree of degradation of the gold fabric:

[0019] The weighting range for the DC resistance and AC resistance of the gold-coated fabric body is 0.30–0.40; the weighting range for the interface capacitance between the gold-coated fabric and the buffer layer, the interface contact resistance between the gold-coated fabric and the aluminum sheath, the interface contact resistance between the gold-coated fabric and the buffer layer, and the overall capacitance between the gold-coated fabric and the buffer layer is 0.20–0.30; the weighting range for the distributed inductance of the gold-coated fabric body is 0.15–0.25; the weighting range for the diameter of the copper wire in the gold-coated fabric is 0.06–0.10; the weighting range for the spacing of the copper wire in the gold-coated fabric is 0.05–0.09; and the weighting range for the surface roughness of the copper wire in the gold-coated fabric is 0.03–0.07.

[0020] Preferably, the electrical characteristic parameters include at least one of the following: DC resistance of the gold cloth body, AC resistance of the gold cloth body, contact resistance at the interface between the gold cloth and the aluminum sheath, contact resistance at the interface between the gold cloth and the buffer layer, capacitance at the interface between the gold cloth and the buffer layer, and distributed inductance of the gold cloth body; the morphological characteristic parameters include at least one of the following: surface roughness of the gold cloth copper wire, diameter of the gold cloth copper wire, and spacing of the gold cloth copper wire.

[0021] Preferably, in step S2, when measuring the electrical characteristic parameters, two aluminum plates are used as electrodes, and gold cloth or gold cloth and interface layer are placed between the two aluminum plates. The measurement is performed by a digital bridge, and weights are placed on the aluminum plates to provide contact pressure.

[0022] Preferably, in step S2, when measuring the surface roughness of the copper wire in the gold-coated fabric, multiple equally spaced measurement segments are divided in the axial direction of the copper wire, and multiple measuring points are selected in each measurement segment to measure the surface roughness value; when measuring the diameter of the copper wire in the gold-coated fabric, multiple copper wires are selected as samples, and multiple cross sections are selected along the axial direction of each copper wire for measurement; when measuring the wire spacing of the copper wire in the gold-coated fabric, a continuous braiding unit is selected to measure the distance between the center lines of adjacent copper wires.

[0023] A 500kV pumped-storage high-voltage cable gold-coated electrical thermal degradation assessment system includes:

[0024] The standard and model establishment module is used to pre-establish a four-level gold fabric degradation level standard and establish a comprehensive degradation degree calculation model. The four-level gold fabric degradation level standard is based on the variation law of gold fabric morphological characteristic parameters with the degree of degradation. The comprehensive degradation degree calculation model is constructed based on the correlation analysis results of gold fabric electrical characteristic parameters, gold fabric morphological characteristic parameters and gold fabric degradation degree.

[0025] The data acquisition module is used to acquire the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated.

[0026] The comprehensive degradation degree calculation module is used to input the measured values ​​of each characteristic parameter into the comprehensive degradation degree calculation model to calculate the comprehensive degradation degree of the gold fabric.

[0027] The degradation assessment module is used to determine the current degradation level of the gold fabric and the corresponding defect stage of the buffer layer based on the overall degradation degree of the gold fabric and the four-level gold fabric degradation level standard.

[0028] The present invention has the following advantages and effects compared with the prior art:

[0029] This invention establishes a multi-parameter joint evaluation system by selecting electrical and morphological characteristic parameters of the gold-coated fabric body and interface as evaluation inputs, thus overcoming the one-sidedness of single-parameter evaluation. It proposes a weighted comprehensive degradation quantification model and provides a normalized calculation formula for relative degradation deviation values, unifying the evaluation scale of multiple characteristic parameters and achieving an objective and quantitative evaluation of the degree of gold-coated fabric degradation. Simultaneously, it establishes a four-level gold-coated fabric degradation standard and its correspondence with the development stages of buffer layer defects, allowing the evaluation results to be directly used to guide operation and maintenance decisions. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall process of the present invention for evaluating the electrothermal degradation of 500kV pumped storage high-voltage cables.

[0031] Figure 2 The diagram shows the measurement platform of the 500kV pumped storage high-voltage cable gold cloth electrothermal degradation assessment method in the embodiment, where (a) is the measurement of electrical characteristic parameters of the gold cloth and interface; and (b) is the measurement of electrical characteristic parameters of the gold cloth body.

[0032] In the diagram, 1-aluminum plate; 2-gold cloth; 3-buffer layer or aluminum sheath. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0034] Example 1

[0035] like Figure 1 The diagram shows a flowchart of a method for assessing the electrothermal degradation of the gold-plated fabric in a 500kV pumped-storage high-voltage cable, including the following steps:

[0036] Step S1: Establish evaluation criteria and calculation models in advance.

[0037] This step establishes a four-level standard for the degradation of gold-coated fabric and a comprehensive degradation calculation model in advance, which will be used to quantitatively assess the degree of degradation and determine the level of degradation of the gold-coated fabric samples to be evaluated.

[0038] (a) Obtain the sample data required to establish the standard.

[0039] Electrical and morphological characteristic parameters of the gold-coated fabric body and its interface are selected as evaluation inputs. Electrical characteristic parameters include the DC resistance of the gold-coated fabric body, the AC resistance of the gold-coated fabric body, the contact resistance at the interface between the gold-coated fabric and the aluminum sheath, the contact resistance at the interface between the gold-coated fabric and the buffer layer, the interface capacitance between the gold-coated fabric and the buffer layer, and the distributed inductance of the gold-coated fabric body. Morphological characteristic parameters include the surface roughness of the copper wires in the gold-coated fabric, the diameter of the copper wires, and the spacing between the copper wires.

[0040] (1) Measurement of electrical characteristic parameters

[0041] like Figure 2 As shown, the measurement platform uses two aluminum plates as electrodes. Weights are placed on the aluminum plates to provide constant contact pressure. When measuring the electrical parameters of the gold-plated cloth, the cloth is placed directly between the two aluminum plates, and the two ends of the digital bridge are connected to the two aluminum plates for measurement. Figure 2 As shown in (b). When measuring the electrical parameters of the interface between the gold-plated cloth and the aluminum sheath or buffer layer, the gold-plated cloth and the corresponding interface layer are placed as a whole between the two aluminum plates, as shown in (b). Figure 2 As shown in (a).

[0042] When measuring characteristic parameters such as inductance or capacitance, connect both ends and select multiple frequency points. Take a reading at each frequency point after it stabilizes, and repeat the test at each measurement point more than 3 times.

[0043] By measuring a large number of gold-coated fabric samples with different degrees of degradation in the manner described above, data on the changes of various electrical characteristic parameters with the degree of degradation of the gold-coated fabric were obtained.

[0044] (2) Measurement of morphological characteristic parameters

[0045] Surface roughness of copper wire: The copper wire is divided into multiple equally spaced measurement segments along its axial direction. Multiple measurement points are selected in each measurement segment to measure the surface roughness value. The surface roughness of a single copper wire is the average value of the results of each measurement point. The overall average roughness is obtained by statistical analysis of the results of multiple copper wires.

[0046] Gold-coated copper wire diameter: Select multiple copper wires as samples, avoiding areas with obvious bending and deformation. Select 3 to 5 cross-sections along the axial direction for each copper wire and measure them with vernier calipers. Calculate the average wire diameter for each copper wire and perform statistical analysis on the wire diameters of multiple copper wires to obtain the overall wire diameter.

[0047] Gold-coated copper wire spacing: Select a structurally complete gold-coated area, select a continuous weaving unit within the area, and the distance between the center lines of adjacent copper wires is the wire spacing. Measure the wire spacing using a reading microscope, repeat the measurement for multiple different gold-coated areas, and average the results to obtain the overall wire spacing.

[0048] By measuring a large number of gold-plated fabric samples with different degrees of degradation in the manner described above, data on the changes of various morphological characteristic parameters with the degree of degradation of the gold-plated fabric were obtained.

[0049] (2) Establish a four-level gold fabric degradation grade standard.

[0050] Based on a large number of measurement data of gold fabric morphology characteristic parameters obtained in step (1), the variation law of gold fabric morphology with the degradation degree is summarized:

[0051] In the initial stage of degradation, slight oxidation or wear begins to appear on the surface of the copper wire, and the woven structure is slightly relaxed locally; as the degradation degree deepens, the wear of the copper wire intensifies, the cross section changes, and the woven structure is both loose and compacted; when the degradation is severe, the copper wire is broken or severely deformed, and the woven structure is severely loose or even partially disintegrated.

[0052] Based on the above law, the degradation degree of the gold fabric is divided into four grades:

[0053] Grade I (normal state): There is no obvious local poor contact phenomenon, the woven form of the copper wire remains intact, no relaxation, fracture or significant deformation occurs, and the overall structural continuity is good.

[0054] Grade II (early degradation): Local copper wires may have slight oxidation or wear, and the woven structure is slightly relaxed locally, but the overall structure still maintains integrity, and the interface contact state has the characteristic of local uneven distribution.

[0055] Grade III (mid-term degradation): The copper wire has relatively obvious wear or local cross-section change, and the woven structure locally presents the coexistence of looseness and compaction.

[0056] Grade IV (severe degradation): The copper wire is broken or severely deformed, the woven structure is severely loose or even partially disintegrated, the contact interface is separated in a large range, and the contact area is greatly reduced.

[0057] The corresponding relationship between the four gold fabric degradation grades and the comprehensive degradation degree D of the gold fabric is:

[0058] 0≤D≤0.2 corresponds to Grade I normal state,

[0059] 0.2<D≤0.5 corresponds to Grade II early degradation,

[0060] 0.5<D≤0.8 corresponds to Grade III mid-term degradation,

[0061] 0.8<D≤1 corresponds to Grade IV severe degradation.

[0062] The four gold fabric degradation grades respectively correspond to different stages of buffer layer defect development.

[0063] (3) Establish a calculation model for the comprehensive degradation degree.

[0064] The different characteristic parameters react to the degradation of the gold fabric to varying degrees. Electrical characteristic parameters directly reflect changes in the conductivity of the gold fabric and are the most sensitive to degradation; morphological characteristic parameters reflect changes in the physical structure of the gold fabric and react relatively slowly.

[0065] By analyzing the correlation between each characteristic parameter and the degree of gold fabric degradation, the weight coefficient of each parameter was determined. The principle for allocating the weight coefficients is: the higher the correlation between the parameter and the degree of gold fabric degradation, the greater the weight.

[0066] In this embodiment, the empirical weight ranges for each characteristic parameter are as follows: the weight ranges for the DC resistance and AC resistance of the gold-coated fabric body are 0.30 to 0.40; the weight ranges for the interface capacitance between the gold-coated fabric and the buffer layer, the interface contact resistance between the gold-coated fabric and the aluminum sheath, the interface contact resistance between the gold-coated fabric and the buffer layer, and the overall capacitance between the gold-coated fabric and the buffer layer are 0.20 to 0.30; the weight range for the distributed inductance of the gold-coated fabric body is 0.15 to 0.25; the weight range for the diameter of the copper wire in the gold-coated fabric is 0.06 to 0.10; the weight range for the spacing of the copper wire in the gold-coated fabric is 0.05 to 0.09; and the weight range for the surface roughness of the copper wire in the gold-coated fabric is 0.03 to 0.07.

[0067] The comprehensive degradation calculation model uses a weighted summation method to synthesize the relative degradation deviation values ​​of each characteristic parameter. The calculation formula is as follows:

[0068] ,

[0069] Where D represents the overall degradation degree of the gold-plated fabric, with a value ranging from 0 to 1; w i d represents the weighting coefficient of the i-th feature parameter; i is the relative degradation deviation value of the i-th feature parameter, with a value range of 0 to 1.

[0070] The formula for calculating the relative degradation deviation value is as follows:

[0071] ,

[0072] Where V is the current measured value of the characteristic parameter; V0 is the factory reference value of the characteristic parameter.

[0073] The relative degradation deviation calculation formula maps characteristic parameters of different dimensions to the 0-1 interval, so that each characteristic parameter can be weighted and summed on the same scale.

[0074] Step S2: Obtain the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated.

[0075] According to the measurement method in step S1 (a), the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated are obtained.

[0076] Specifically, in this embodiment, the weight of the weight is 0.2 kg. Using the above-mentioned measurement platform, two aluminum plates are connected to the two ends of the digital bridge to measure the DC resistance of the gold cloth body; multiple frequency points are selected to measure the overall capacitance of the gold cloth and buffer layer, and a reading is taken once after each frequency point stabilizes. The test is repeated more than 3 times for each measuring point.

[0077] For the morphological parameters, multiple copper wires were selected as samples, avoiding areas with obvious bending and deformation. Three to five cross-sections were selected along the axial direction for each copper wire, and measurements were taken using vernier calipers. The average wire diameter of each copper wire was calculated, and statistical analysis was performed on the wire diameters of multiple copper wires to obtain the wire diameter of the gold-coated fabric. A gold-coated fabric area with a complete structure was selected, and continuous weaving units were selected within the area. The distance between the center lines of adjacent copper wires was the wire spacing. The wire spacing was measured using a reading microscope. The above process was repeated for multiple different gold-coated fabric areas, and the results were averaged to obtain the wire spacing of the gold-coated fabric.

[0078] For the raw measurement data, outlier removal and dimensional normalization are required.

[0079] Taking the measurement data of a gold-plated fabric sample in this embodiment as an example:

[0080]

[0081] Step S3: Input the measured values ​​of each feature parameter into the comprehensive degradation calculation model to calculate the comprehensive degradation degree of the gold fabric.

[0082] Substitute the measured values ​​of each characteristic parameter obtained in step S2 into the comprehensive degradation calculation model established in step S1 (iii). First, calculate the relative degradation deviation value of each characteristic parameter according to the relative degradation deviation calculation formula, and then... The overall degradation degree D of the gold fabric is obtained by weighted calculation.

[0083] Substituting the above measurements into the relative degradation deviation formula, we get:

[0084] d1=0.0006, d2=0.0885, d3=0.0408, d4=0,

[0085] By combining the weighting coefficients of each parameter (DC resistance of the gold fabric body 0.35, overall capacitance of the gold fabric and buffer layer 0.30, copper wire spacing 0.20, copper wire diameter 0.15), the overall degradation degree of the gold fabric is calculated as follows:

[0086] D=0.03.

[0087] S4. Based on the overall deterioration degree of the gold fabric, determine the current deterioration level of the gold fabric and the corresponding buffer layer defect stage by referring to the four-level gold fabric deterioration level standard.

[0088] Based on the overall degradation degree of the gold fabric calculated in step S3, D=0.03, and referring to the four-level gold fabric degradation standard established in step S1 (II): D∈[0, 0.2] corresponds to Level I normal state. Therefore, the current degradation level of this gold fabric sample is Level I normal state, corresponding to the normal stage of the buffer layer.

[0089] Example 2

[0090] This embodiment provides a 500kV pumped-storage high-voltage cable gold-coated electrical thermal degradation assessment system, which includes the following modules:

[0091] The standard and model establishment module is used to pre-establish a four-level gold fabric degradation level standard and establish a comprehensive degradation degree calculation model. The four-level gold fabric degradation level standard is based on the variation law of gold fabric morphological characteristic parameters with the degree of degradation. The comprehensive degradation degree calculation model is constructed based on the correlation analysis results of gold fabric electrical characteristic parameters, gold fabric morphological characteristic parameters and gold fabric degradation degree.

[0092] The data acquisition module is used to acquire the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated.

[0093] The comprehensive degradation degree calculation module is used to input the measured values ​​of each characteristic parameter into the comprehensive degradation degree calculation model to calculate the comprehensive degradation degree of the gold fabric.

[0094] The degradation assessment module is used to determine the current degradation level of the gold fabric and the corresponding defect stage of the buffer layer based on the overall degradation degree of the gold fabric and the four-level gold fabric degradation level standard.

[0095] The above embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any changes or other equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A method for evaluating the electrothermal degradation of the gold-plated fabric in a 500kV pumped-storage high-voltage cable, characterized in that... Including the following steps: S1. Establish a four-level standard for the degradation of gold-coated fabric and a comprehensive degradation calculation model in advance; the four-level standard for the degradation of gold-coated fabric is based on the variation law of the morphological characteristic parameters of gold-coated fabric with the degree of degradation; the comprehensive degradation calculation model is constructed based on the correlation analysis results of the electrical characteristic parameters and morphological characteristic parameters of gold-coated fabric with the degree of degradation of gold-coated fabric. S2. Obtain the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated; S3. Input the measured values ​​of each characteristic parameter into the comprehensive degradation calculation model to calculate the comprehensive degradation degree of the gold fabric; S4. Based on the overall deterioration degree of the gold fabric, determine the current deterioration level of the gold fabric and the corresponding buffer layer defect stage by referring to the four-level gold fabric deterioration level standard.

2. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 1, characterized in that, In step S1, the four levels of gold fabric degradation include Level I normal state, Level II early degradation, Level III mid-term degradation, and Level IV severe degradation. The correspondence between the overall deterioration degree of the gold fabric and the four levels of gold fabric deterioration is as follows: 0≤D≤0.2 corresponds to Level I normal state, 0.2<D≤0.5 corresponds to Level II early deterioration, 0.5<D≤0.8 corresponds to Level III mid-term deterioration, and 0.8<D≤1 corresponds to Level IV severe deterioration, where D represents the overall deterioration degree of the gold fabric.

3. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 1, characterized in that, In step S1, the Level I normal state corresponds to no obvious local contact problems and the copper wire braiding remains intact; the Level II early deterioration corresponds to slight oxidation or wear of local copper wires and slight loosening of the braiding structure; the Level III mid-term deterioration corresponds to obvious wear or local cross-sectional changes of copper wires and a combination of local loosening and compaction of the braiding structure; the Level IV severe deterioration corresponds to broken or severely deformed copper wires and a severely loose or even partially disintegrated braiding structure.

4. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 1, characterized in that, The comprehensive degradation calculation model is as follows: ， Where D represents the overall degradation degree of the gold-plated fabric, with a value ranging from 0 to 1; w i d represents the weighting coefficient of the i-th feature parameter; i is the relative degradation deviation value of the i-th feature parameter, with a value range of 0 to 1.

5. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 4, characterized in that, The formula for calculating the relative degradation deviation value is as follows: Where V is the current measured value of the characteristic parameter; V0 is the factory reference value of the characteristic parameter.

6. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 4, characterized in that, The weighting coefficients are determined based on the correlation between each characteristic parameter and the degree of gold fabric degradation: The weighting range for the DC resistance and AC resistance of the gold-coated fabric body is 0.30–0.40; the weighting range for the interface capacitance between the gold-coated fabric and the buffer layer, the interface contact resistance between the gold-coated fabric and the aluminum sheath, the interface contact resistance between the gold-coated fabric and the buffer layer, and the overall capacitance between the gold-coated fabric and the buffer layer is 0.20–0.30; the weighting range for the distributed inductance of the gold-coated fabric body is 0.15–0.25; the weighting range for the diameter of the copper wire in the gold-coated fabric is 0.06–0.10; the weighting range for the spacing of the copper wire in the gold-coated fabric is 0.05–0.09; and the weighting range for the surface roughness of the copper wire in the gold-coated fabric is 0.03–0.

07.

7. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 1, characterized in that, The electrical characteristic parameters include at least one of the following: DC resistance of the gold cloth body, AC resistance of the gold cloth body, contact resistance at the interface between the gold cloth and the aluminum sheath, contact resistance at the interface between the gold cloth and the buffer layer, capacitance at the interface between the gold cloth and the buffer layer, and distributed inductance of the gold cloth body; the morphological characteristic parameters include at least one of the following: surface roughness of the gold cloth copper wire, diameter of the gold cloth copper wire, and spacing of the gold cloth copper wire.

8. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 1, characterized in that, In step S2, when measuring the electrical characteristic parameters, two aluminum plates are used as electrodes, and gold cloth or gold cloth and interface layer are placed between the two aluminum plates. The measurement is performed by a digital bridge, and weights are placed on the aluminum plates to provide contact pressure.

9. The method for evaluating the electrothermal degradation of the gold-plated cloth in a 500kV pumped-storage high-voltage cable according to claim 7, characterized in that, In step S2, when measuring the surface roughness of the copper wire in the gold-coated cloth, multiple equally spaced measurement segments are divided in the axial direction of the copper wire, and multiple measuring points are selected in each measurement segment to measure the surface roughness value; when measuring the diameter of the copper wire in the gold-coated cloth, multiple copper wires are selected as samples, and multiple cross sections are selected along the axial direction of each copper wire for measurement; when measuring the wire spacing of the copper wire in the gold-coated cloth, a continuous braiding unit is selected to measure the distance between the center lines of adjacent copper wires.

10. A system for evaluating the electrothermal degradation of 500kV pumped-storage high-voltage cables, characterized in that, include: The standard and model establishment module is used to pre-establish a four-level gold fabric degradation level standard and establish a comprehensive degradation degree calculation model. The four-level gold fabric degradation level standard is based on the variation law of gold fabric morphological characteristic parameters with the degree of degradation. The comprehensive degradation degree calculation model is constructed based on the correlation analysis results of gold fabric electrical characteristic parameters, gold fabric morphological characteristic parameters and gold fabric degradation degree. The data acquisition module is used to acquire the measured values ​​of the electrical and morphological characteristic parameters of the gold cloth body and interface to be evaluated. The comprehensive degradation degree calculation module is used to input the measured values ​​of each characteristic parameter into the comprehensive degradation degree calculation model to calculate the comprehensive degradation degree of the gold fabric. The degradation assessment module is used to determine the current degradation level of the gold fabric and the corresponding defect stage of the buffer layer based on the overall degradation degree of the gold fabric and the four-level gold fabric degradation level standard.

Images