Cable insulation ultralow frequency dielectric response influence factor analysis method
By segmenting, measuring and temperature testing XLPE cables, and combining electroacoustic pulse method and DSC technology to analyze the dielectric response change pattern of cable insulation, the problem of insufficient accuracy of cable insulation detection in existing technologies is solved, and a fast and accurate cable aging status assessment is achieved.
Patent Information
- Application Number
- CN202510765023.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-10
- Publication Date
- 2025-10-10
AI Technical Summary
In the existing technology, cable insulation detection methods lack accuracy, especially in the analysis of factors affecting ultra-low frequency dielectric response, which lacks effective empirical data, affecting the reliability and safety of the power network.
By dividing, measuring and drying the XLPE cable segments, calculating the capacitance using the electroacoustic pulse method, testing the oxidation induction time using DSC technology, calculating the activation energy using the Arrhenius equation, analyzing how the dielectric response changes with length, thickness and temperature, and performing normalization processing to obtain objective weights.
It achieves accurate and rapid analysis of factors affecting the ultra-low frequency dielectric response of cable insulation, improves the accuracy and efficiency of detection, and can effectively evaluate the aging status of cables.
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of power cable insulation detection, and in particular relates to a method for analyzing factors affecting ultra-low frequency dielectric response of cable insulation. Background Art
[0002] With the continuous expansion of urban scale and the rapid development of power infrastructure, power cable lines have become the main electrical equipment in the current distribution network due to their safe and reliable power supply, space-saving and beautifying effects on cities. There are many types of power cables. Among them, cross-linked polyethylene (XLPE) cables are widely used in medium and low voltage transmission and distribution lines due to their low maintenance workload, easy laying and good electrical performance. However, in actual operation, cables are often affected by various adverse factors such as insulation aging, moisture intrusion, load changes, external force damage, etc., which lead to the frequent occurrence of various potential problems, which directly affect the reliability of power network transmission and distribution of electric energy. and safety, therefore, it is necessary to conduct regular testing and diagnosis of cable insulation performance, detect the degradation of cable insulation performance caused by insulation damage, moisture, joint aging, partial discharge, and water tree deterioration, and measure the overall aging status of the cable. Among the existing detection methods, ultra-low frequency dielectric loss detection technology is the most effective test method for cable handover test, power outage pre-test, and diagnostic test. However, although the domestic ultra-low frequency dielectric loss detection technology has a certain foundation in related theoretical and practical research, it is still insufficient in the accumulation of relevant empirical data. Therefore, it is necessary to develop an accurate, fast and effective method for analyzing the factors affecting the ultra-low frequency dielectric response of cable insulation. Summary of the Invention
[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an accurate, rapid and effective method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation.
[0004] The object of the present invention is achieved by: a method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation, comprising the following steps: Step 1: Obtain the XLPE cable to be tested, and then divide the XLPE cable into multiple XLPE cable segments of different lengths and thicknesses; Step 2: Measure and record the length and insulation thickness data of the XLPE cable segments. Then, calculate the capacitance of each XLPE cable segment using the electroacoustic pulse method. Then, select the matching external excitation voltage amplitude and capacitance to obtain an effective dielectric response current signal. Finally, based on the length and thickness data of the XLPE cable segments and their corresponding dielectric response current signals, analyze how the ultra-low frequency dielectric response varies with cable length and insulation thickness. Step 3: Obtain the XLPE cable to be tested again, and divide the obtained XLPE cable into multiple pieces of equal length and mass to form temperature impact test samples. Then, sort and number the temperature impact test samples; Step 4: Using DSC, place the samples in environments with different temperatures and test the oxidation induction time of the XLPE cable insulation at different experimental temperatures. Then, calculate the activation energy of the XLPE cable insulation based on the Arrhenius equation and extrapolate its life at the operating temperature to form temperature effect data; Step 5: Preprocess the temperature impact data obtained in step 4; Step 6: Based on the temperature effect data after pre-processing in Step 5, plot the variation curves of the ultra-low frequency dielectric response characteristics of the XLPE cable insulation at different temperatures. Then, based on the variation of the ultra-low frequency dielectric loss response with the test temperature, focus on the frequency shift characteristics of dielectric relaxation with temperature, and calculate the activation energy corresponding to the relaxation process. Finally, further analyze the variation of the linear / nonlinear characteristics of the excitation voltage-response current of the XLPE cable insulation at different test temperatures. Step 7: Based on the analysis results in steps 2 and 6, determine and analyze the impact of cable length, insulation thickness, and temperature on the cable's ultra-low frequency dielectric response. Finally, perform normalization to obtain the objective weight of each indicator.
[0005] Furthermore, in step 2, before calculating the capacitance of each XLPE cable segment by the electroacoustic pulse method, the XLPE cable segment needs to be vacuum dried.
[0006] Furthermore, the preprocessing operation in step 5 can filter and remove noise data and unreasonable data of the temperature-affected data.
[0007] The beneficial effects of the present invention are as follows: the present invention first calculates the capacitance of XLPE cable segments of different lengths and thicknesses to obtain an effective dielectric response current signal, and analyzes the variation of the ultra-low frequency dielectric response with the cable length and insulation thickness based on the dielectric response current signal; then, XLPE cables of equal length and mass are sorted and numbered, and placed in environments of different temperatures respectively, and the oxidation induction time of the XLPE cable insulation is tested; then, according to the Arrhenius equation, the activation energy of the XLPE cable insulation is calculated, and its life at the operating temperature is extrapolated to form temperature influence data; then, after pre-processing the temperature influence data, a curve of the variation of the ultra-low frequency dielectric response characteristics of the XLPE cable insulation at different temperatures is plotted, and the variation of the linear / nonlinear characteristics of the XLPE cable insulation dielectric excitation voltage-response current is analyzed; finally, the influence of the cable length, insulation thickness and temperature factors on the ultra-low frequency dielectric response of the cable is judged, and normalization processing is performed to obtain the objective weight of each indicator; in general, the present invention has the advantages of being accurate, fast and having good use effect. DETAILED DESCRIPTION
[0008] The present invention will be further described below.
[0009] Embodiment: A method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation, comprising the following steps: Step 1: Obtain the XLPE cable to be tested, and then divide the XLPE cable into multiple XLPE cable segments of different lengths and thicknesses; Step 2: Measure and record the length and insulation thickness data of the XLPE cable segments. Then, vacuum dry the XLPE cable segments. After drying, calculate the capacitance of each XLPE cable segment using the electroacoustic pulse method. Then, select the matching external excitation voltage amplitude and capacitance to obtain an effective dielectric response current signal. Finally, based on the length and thickness data of the XLPE cable segments and their corresponding dielectric response current signals, analyze how the ultra-low frequency dielectric response changes with cable length and insulation thickness. Step 3: Obtain the XLPE cable to be tested again, and divide the obtained XLPE cable into multiple pieces of equal length and mass to form temperature impact test samples. Then, sort and number the temperature impact test samples; Step 4: Using DSC, place the samples in environments with different temperatures and test the oxidation induction time of the XLPE cable insulation at different experimental temperatures. Then, calculate the activation energy of the XLPE cable insulation based on the Arrhenius equation and extrapolate its life at the operating temperature to form temperature effect data; Step 5: Preprocess the temperature impact data obtained in step 4 to filter and remove noise data and unreasonable data; Step 6: Based on the temperature effect data after pre-processing in Step 5, plot the variation curves of the ultra-low frequency dielectric response characteristics of the XLPE cable insulation at different temperatures. Then, based on the variation of the ultra-low frequency dielectric loss response with the test temperature, focus on the frequency shift characteristics of dielectric relaxation with temperature, and calculate the activation energy corresponding to the relaxation process. Finally, further analyze the variation of the linear / nonlinear characteristics of the excitation voltage-response current of the XLPE cable insulation at different test temperatures. Step 7: Based on the analysis results in steps 2 and 6, determine and analyze the impact of cable length, insulation thickness, and temperature on the cable's ultra-low frequency dielectric response. Finally, perform normalization to obtain the objective weight of each indicator.
[0010] When the present invention is used, first, XLPE cable segments of different lengths and thicknesses are dried, and after the drying process is completed, the capacitance of each XLPE cable segment is calculated by the electroacoustic pulse method, and then the external excitation voltage amplitude and capacitance that match it are selected to obtain an effective dielectric response current signal, and then the variation law of the ultra-low frequency dielectric response with the cable length and insulation thickness is analyzed according to the dielectric response current signal; then, a plurality of XLPE cable test samples of equal length and equal quality are selected again, and the batch of test samples are sorted and numbered, and then they are placed in environments of different temperatures respectively, and the oxidation induction time of the XLPE cable insulation at different experimental temperatures is measured. The test is carried out at room temperature, and then, according to the Arrhenius equation, the activation energy of the XLPE cable insulation is calculated, and its life at the operating temperature is extrapolated to form temperature influence data. Finally, the temperature influence data is preprocessed, and after the preprocessing is completed, a curve of the change law of the ultra-low frequency dielectric response characteristics of the XLPE cable insulation at different temperatures is drawn, and the change law of the linear / non-linear characteristics of the excitation voltage-response current of the XLPE cable insulation medium is analyzed. Finally, the influence of cable length, insulation thickness and temperature factors on the ultra-low frequency dielectric response of the cable is judged, and normalization processing is performed to obtain the objective weight of each indicator. In general, the present invention has the advantages of being accurate, fast and having good use effect.
[0011] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.
Claims
1. A method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation, characterized in that: The following steps are involved: Step 1: Obtain the XLPE cable to be tested, and then divide the XLPE cable into multiple XLPE cable segments of different lengths and thicknesses; Step 2: Measure and record the length and insulation thickness data of the XLPE cable segments. Then, calculate the capacitance of each XLPE cable segment using the electroacoustic pulse method. Then, select the matching external excitation voltage amplitude and capacitance to obtain an effective dielectric response current signal. Finally, based on the length and thickness data of the XLPE cable segments and their corresponding dielectric response current signals, analyze how the ultra-low frequency dielectric response varies with cable length and insulation thickness. Step 3: Obtain the XLPE cable to be tested again, and divide the obtained XLPE cable into multiple pieces of equal length and mass to form temperature impact test samples. Then, sort and number the temperature impact test samples; Step 4: Using DSC, place the samples in environments with different temperatures and test the oxidation induction time of the XLPE cable insulation at different experimental temperatures. Then, calculate the activation energy of the XLPE cable insulation based on the Arrhenius equation and extrapolate its life at the operating temperature to form temperature effect data; Step 5: Preprocess the temperature impact data obtained in step 4; Step 6: Based on the temperature effect data after pre-processing in Step 5, plot the variation curves of the ultra-low frequency dielectric response characteristics of the XLPE cable insulation at different temperatures. Then, based on the variation of the ultra-low frequency dielectric loss response with the test temperature, focus on the frequency shift characteristics of dielectric relaxation with temperature, and calculate the activation energy corresponding to the relaxation process. Finally, further analyze the variation of the linear / nonlinear characteristics of the excitation voltage-response current of the XLPE cable insulation at different test temperatures. Step 7: Based on the analysis results in steps 2 and 6, determine and analyze the impact of cable length, insulation thickness, and temperature on the cable's ultra-low frequency dielectric response. Finally, perform normalization to obtain the objective weight of each indicator.
2. The method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation according to claim 1, characterized in that: In step 2, before calculating the capacitance of each XLPE cable segment by the electroacoustic pulse method, the XLPE cable segment needs to be vacuum dried.
3. The method for analyzing factors affecting the ultra-low frequency dielectric response of cable insulation according to claim 1, characterized in that: The preprocessing operation in step 5 can filter and remove noise data and unreasonable data of the temperature-affected data.