110kV XLPE cable buffer layer ablation degree evaluation method based on electromagnetic stability factor

Abstract

The invention discloses a 110kV XLPE cable buffer layer ablation degree evaluation method based on an electromagnetic stability factor, and the method comprises the steps: inputting a test signal with a certain amplitude and frequency into a to-be-tested cable section, calculating a cable electric field disturbance factor lambda, calculating a magnetic field disturbance factor eta, and calculating an electromagnetic stability factor sigma, and judging the ablation degree of the cable buffer layer through the electromagnetic stable factor sigma. The method has the beneficial effects that the ablation degree of the cable buffer layer is evaluated by applying the test signal to the 110kV XLPE cable, calculating the electric field disturbance factor and the magnetic field disturbance factor and extracting the electromagnetic stability factor, the evaluation method is efficient and convenient, and the ablation degree of the 110kV XLPE cable buffer layer can be better evaluated. And a scientific basis is provided for formulating operation and maintenance management and control measures for the buffer layer state of the 110kV XLPE cable in operation. The method has important practical significance for improving the operation reliability of the cable, reducing the fault occurrence rate and prolonging the service life of the cable.

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 an electromagnetic stability factor. Background Art

[0002] With the rapid development of the economy, the current social demand for electricity is also increasing. High-voltage cables are key equipment in power transmission systems. However, in recent years, buffer layer ablation failures of high-voltage XLPE cables have occurred frequently, which has attracted widespread attention. Buffer layer ablation failures of high-voltage cross-linked polyethylene (XLPE) cables not only lead to insulation breakdown, but have also become an important 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, evaluating 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] At present, there is still a lack of methods for evaluating the degree of ablation of the buffer layer of 110kV XLPE cables, and there are no widely used testing standards and methods. Therefore, it is urgent to find a method for evaluating the degree of ablation of the buffer layer of 110kV XLPE cables, so as to provide a scientific basis for formulating operation and maintenance control measures for the buffer layer of 110kV XLPE cables in operation. This has important practical significance for improving the operating reliability of cables, reducing the occurrence of failures, and extending the service life of cables. Summary of the invention

[0004] This method is a method for evaluating the ablation degree 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 ablation degree of the cable buffer layer by measuring the electromagnetic stability factor during cable operation. Specifically, it 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 segment to be tested was equally divided into three parts, and the corresponding voltage and current signal acquisition equipment was placed at the two ends and the middle part at equal distances. 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 measuring 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 measuring point, unit: cm; μ is the magnetic permeability of the cable; L is the cable length, unit: m; dL is the tiny 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 110kV XLPE cable buffer layer ablation by 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. The evaluation method is simple and efficient, and can better evaluate the insulation damage state of the 110kV cable, which has important practical significance for improving the operation reliability of the cable, reducing the occurrence rate 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 in conjunction with the accompanying drawings and specific implementation processes.

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

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

[0024] A 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 equally divided into three parts. The corresponding voltage and current signal acquisition equipment were placed at the two ends and the middle part at equal distances. 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 measuring 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 measuring point, unit: cm; μ is the magnetic permeability of the cable; L is the cable length, unit: m; dL is the tiny 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 buffer layer of the 110kV XLPE cable by the electromagnetic stability factor σ. When σ≤0.428, the buffer layer of the 110kV XLPE cable 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 section to be tested was equally divided into three parts, and the corresponding voltage and current signal acquisition equipment was placed at the two ends and the middle part at equal distances. 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 measuring 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 tiny 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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