A method for evaluating the degree of ablation of the buffer layer of 110kV XLPE cables based on electromagnetic stability factor

Abstract

The present invention discloses a method for evaluating the degree of ablation of a 110kV XLPE cable buffer layer based on an electromagnetic stability factor. The method comprises the following steps: inputting a test signal of a certain amplitude and frequency into the cable segment to be tested, calculating the cable electric field disturbance factor λ, the magnetic field disturbance factor η, and the electromagnetic stability factor σ, respectively; and determining the degree of ablation of the cable buffer layer by the electromagnetic stability factor σ. The beneficial effect of the present invention is that by applying a test signal to a 110kV XLPE cable, calculating the electric field disturbance factor and the magnetic field disturbance factor, and extracting the electromagnetic stability factor to evaluate the degree of ablation of the cable buffer layer, the method is efficient and convenient, and can effectively evaluate the degree of ablation of the 110kV XLPE cable buffer layer. The method provides a scientific basis for formulating operation and maintenance control measures for the buffer layer status of in-service 110kV XLPE cables. This has important practical significance for improving the operational reliability of cables, reducing the occurrence of failures, and extending the service life of cables.

Description

Technical Field

[0001] The invention belongs to the field of cable buffer layer ablation degree assessment, and in particular relates to a 110kV XLPE cable buffer layer ablation degree assessment method based on electromagnetic stability factor. Background Art

[0002] With the rapid development of the economy, the current society's demand for electricity is also increasing. High-voltage cables are key equipment in power transmission systems. However, in recent years, the frequent occurrence of buffer layer ablation failures in high-voltage XLPE cables has attracted widespread attention. Buffer layer ablation failures in high-voltage cross-linked polyethylene (XLPE) cables not only lead to insulation breakdown, but have also become a major issue affecting the safe operation of power grids. Cable buffer layer ablation is not only difficult to detect, but once it occurs, it usually requires the entire cable to be replaced, resulting in huge economic losses. Therefore, assessing the degree of buffer layer ablation of high-voltage cross-linked polyethylene (XLPE) power cables plays a very important role in maintaining the safe operation of power networks.

[0003] Currently, methods for assessing the extent of erosion in 110kV XLPE cable buffers are still relatively scarce, with no widely accepted testing standards or methods. Therefore, a method for assessing the extent of erosion in 110kV XLPE cables' buffers is urgently needed to provide a scientific basis for developing operational and maintenance measures for the buffers of in-service 110kV XLPE cables. This approach is of great practical significance for improving cable reliability, reducing failure rates, and extending cable service life. Summary of the Invention

[0004] This method is a method for evaluating the degree of ablation of the buffer layer of a 110kV XLPE cable based on the electromagnetic stability factor. The method is simple and convenient to operate and can effectively evaluate the degree of ablation of the cable buffer layer by measuring the electromagnetic stability factor during cable operation. The method specifically includes the following steps:

[0005] Step 1: Pass the test signal through the cable and collect

[0006] A 110kV XLPE power cable with a length of L was selected as the research object. A test signal of 110V, 3mA, and a frequency of 50Hz was generated by the test equipment and input into the cable. The cable section to be tested was divided into three equal parts. The corresponding voltage and current signal acquisition equipment was placed equidistantly at the two ends and the middle part. The voltage amplitude of the test signal collected at each point was recorded as: V1, V2, V3, V4, unit: V; the current value was: I1, I2, I3, I4, unit: mA;

[0007] Step 2: Calculate the cable electric field disturbance factor λ

[0008]

[0009] Where L is the length of the cable, unit: m; r is the distance from the center of the cable to the measurement point, unit: cm; V is the cable test voltage, unit: V; D is the outer diameter of the cable, unit: cm; d is the radius of the inner conductor of the cable, unit: cm; R is the effective resistance of the cable segment, unit: Ω; tanδ is the dielectric loss constant;

[0010] Step 3: Calculate the cable magnetic field disturbance factor η

[0011]

[0012] I is the cable test current, unit: mA; r is the distance from the center point of the cable to the measurement point, unit: cm; μ is the magnetic permeability of the cable; L is the cable length, unit: m; dL is the small length vector of the current segment; is the unit vector pointing from the current segment to the measurement point;

[0013] Step 4: Calculate the electromagnetic stability factor σ

[0014]

[0015] Step 5: Evaluate the degree of erosion of the buffer layer of 110kV XLPE cables by using the electromagnetic stability factor σ

[0016] When σ≤0.128, the buffer layer of 110kV XLPE cable is slightly ablated;

[0017] When 0.128<σ≤0.473, the buffer layer of 110kV XLPE cable is moderately ablated;

[0018] When σ>0.473, the buffer layer of 110kV XLPE cable is severely ablated;

[0019] The beneficial effect of the present invention lies in that by applying a test signal to the XLPE cable, the electric field disturbance factor, the magnetic field disturbance factor and the electromagnetic stability factor are calculated, and the degree of ablation of the buffer layer of the 110kV XLPE cable is evaluated by the electromagnetic stability factor. This evaluation method is simple and efficient, and can better evaluate the insulation damage status of the 110kV cable. It has important practical significance for improving the operational reliability of the cable, reducing the occurrence of failures, and extending the service life of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention relates to a flow chart of a method for evaluating the degree of ablation of a 110kV XLPE cable buffer layer based on an electromagnetic stability factor; DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and specific implementation processes.

[0022] Figure 1 The flowchart of a method for evaluating the degree of ablation of the buffer layer of a 110kV XLPE cable based on the electromagnetic stability factor includes the following steps:

[0023] Step 1: Pass the test signal through the cable and collect

[0024] An XLPE power cable with a length of L was selected as the research object. A test signal of 110V, 3mA, and a frequency of 50Hz was generated by the test equipment and input into the cable. The XLPE cable segment to be tested was divided into three equal parts. The corresponding voltage and current signal acquisition equipment were placed at equal distances at the two ends and the middle part. The voltage amplitude of the test signal collected at each point was recorded as: V1, V2, V3, V4, unit: V; the current value was: I1, I2, I3, I4, unit: mA;

[0025] Step 2: Calculate the cable electric field disturbance factor

[0026]

[0027] Where L is the length of the cable, unit: m; r is the distance from the center of the cable to the measurement point, unit: cm; V is the cable test voltage, unit: V; D is the outer diameter of the cable, unit: cm; d is the radius of the inner conductor of the cable, unit: cm; R is the effective resistance of the cable segment, unit: Ω; tanδ is the dielectric loss constant;

[0028] Step 3: Calculate the cable magnetic field disturbance factor

[0029]

[0030] I is the cable test current, unit: mA; r is the distance from the center point of the cable to the measurement point, unit: cm; μ is the magnetic permeability of the cable; L is the cable length, unit: m; dL is the small length vector of the current segment; is the unit vector pointing from the current segment to the measurement point;

[0031] Step 4: Calculate the electromagnetic stability factor

[0032]

[0033] Step 5: Evaluate the degree of ablation of the 110kV XLPE cable buffer layer using the electromagnetic stability factor σ. When σ≤0.428, the 110kV XLPE cable buffer layer is slightly ablated.

[0034] When 0.428<σ≤0.675, the buffer layer of 110kV XLPE cable is moderately ablated;

[0035] When σ>0.675, the buffer layer of 110kV XLPE cable is severely ablated.

Claims

1. A method for evaluating the degree of ablation of the buffer layer of a 110kV XLPE cable based on electromagnetic stability factor, characterized in that The following steps are involved: Step 1: Pass the test signal through the cable and collect A 110kV XLPE power cable with a length of L was selected as the research object. A test signal of 110V, 3mA, and a frequency of 50Hz was generated by the test equipment and input into the cable. The cable segment to be tested was divided into three equal parts. The corresponding voltage and current signal acquisition equipment was placed equidistantly at the two ends and the middle part. The voltage amplitude of the test signal collected at each point was recorded as: V1, V2, V3, V4, unit: V; the current value was: I1, I2, I3, I4, unit: mA; Step 2: Calculate the cable electric field disturbance factor λ Where L is the length of the cable, unit: m; r is the distance from the center of the cable to the measurement point, unit: cm; V is the cable test voltage, unit: V; D is the outer diameter of the cable, unit: cm; d is the radius of the inner conductor of the cable, unit: cm; R is the effective resistance of the cable segment, unit: Ω; tanδ is the dielectric loss constant; Step 3: Calculate the cable magnetic field disturbance factor η I is the cable test current, unit: mA; r is the distance from the center point of the cable to the measuring point, unit: cm; μ is the magnetic permeability of the cable; L is the cable length, unit: m; dL is the small length vector of the current segment; is the unit vector pointing from the current segment to the measurement point; Step 4: Calculate the electromagnetic stability factor σ Step 5: Evaluate the degree of XLPE cable buffer layer ablation by electromagnetic stability factor σ When σ≤0.428, the buffer layer of 110kV XLPE cable is slightly ablated; When 0.428<σ≤0.675, the buffer layer of 110kV XLPE cable is moderately ablated; When σ>0.675, the buffer layer of 110kV XLPE cable is severely ablated.

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