CN-121978481-A - Power distribution cable insulation aging detection method and device based on harmonic leakage

CN121978481ACN 121978481 ACN121978481 ACN 121978481ACN-121978481-A

Abstract

The invention provides a distribution cable insulation aging detection method based on harmonic leakage, which comprises the steps of obtaining magnetic induction intensity generated by leakage harmonic current outside a distribution cable to be detected at a plurality of node positions of the distribution cable, determining harmonic leakage current at each node position, obtaining corresponding common-mode harmonic components and difference-mode harmonic components at a plurality of preselected harmonic angular frequencies, respectively calculating to obtain equivalent capacitance parameters of the distribution cable insulation at each harmonic angular frequency, determining the aging degree of the distribution cable insulation based on the variation of the equivalent capacitance parameters at each harmonic angular frequency, comparing and analyzing the difference-mode harmonic components at different node positions, and determining the node position with abnormally increased amplitude as the node position corresponding to the distribution cable insulation aging defect. The method can realize on-line monitoring, quantitative evaluation and defect positioning of the insulation aging state of the distribution cable under the electrified operation condition, and improves the accuracy and reliability of monitoring.

Inventors

TIAN YE
PANG HUAN
LI XIAOFEI
LIU LELE
ZHU DACHUAN
HU FEILIANG
LIU HAOMENG

Assignees

国网北京市电力公司

Dates

Publication Date: 20260505
Application Date: 20260210

Claims (10)

1. The utility model provides a distribution cable insulation ageing detection method based on harmonic leakage which characterized in that includes: Acquiring magnetic induction intensity signals generated by leakage harmonic currents outside the tested distribution cable at a plurality of node positions of the distribution cable, and determining harmonic leakage current signals at each node position based on the magnetic induction intensity signals; Obtaining corresponding common mode harmonic components and difference mode harmonic components at a plurality of preselected harmonic angular frequencies based on the harmonic leakage current signals at each node location; calculating a corresponding relation based on a frequency domain between common-mode harmonic components and power distribution cable insulation equivalent parameters, respectively calculating to obtain equivalent capacitance parameters of power distribution cable insulation under each harmonic angular frequency, and determining the aging degree of the power distribution cable insulation based on the variation of the equivalent capacitance parameters under each harmonic angular frequency; And under each harmonic angular frequency, carrying out transverse comparison analysis on the difference mode harmonic components at different node positions, and determining the node position with the amplitude of the difference mode harmonic component abnormally increased as the node position corresponding to the insulation aging defect of the distribution cable.
2. The harmonic leakage based power distribution cable insulation degradation detection method of claim 1, wherein the step of determining harmonic leakage current signals at each node location based on the magnetic induction signals comprises: node according to distribution cable Magnetic field response signal generated by harmonic leakage current and linear relation expression calculation node between magnetic field response signal and harmonic leakage current Harmonic leakage current at The linear relation expression is: Wherein, the And For the preset parameters determined according to the experiments, Is a node At harmonic angular frequency The magnetic induction intensity of the lower part is higher than that of the upper part, Is a node At harmonic angular frequency The lower harmonic leakage current.
3. The harmonic leakage based power distribution cable insulation degradation detection method of claim 2, wherein the obtaining corresponding common mode harmonic components and differential mode harmonic components at a plurality of preselected harmonic angular frequencies based on the harmonic leakage current signals at each node location comprises: At harmonic angular frequency Where the node is calculated according to the following formula Common mode harmonic components and difference mode harmonic components at: Wherein, the Is a node At harmonic angular frequency The harmonic leakage current at the bottom of the circuit, And Respectively nodes At the harmonic angular frequency The lower common mode harmonic component and the difference mode harmonic component, And Respectively nodes At the harmonic angular frequency The common mode voltage to ground harmonic component and the differential mode voltage to ground harmonic component, Is the modal transformation ratio coefficient between the common mode and the difference mode, Insulating distribution cables at said harmonic angular frequencies The equivalent capacitance parameter of the lower part of the capacitor, For the angular frequency of the harmonic wave, In imaginary units.
4. The method for detecting insulation degradation of a distribution cable based on harmonic leakage according to claim 3, wherein the step of determining the degradation degree of insulation of the distribution cable comprises: According to the frequency domain calculation relation between the common-mode harmonic components and the corresponding common-mode voltage-to-ground harmonic components, calculating to obtain the insulation of the distribution cable at each harmonic angular frequency The equivalent capacitance parameter The frequency domain calculation relation is as follows: Determining the variation of the equivalent capacitance parameter based on the variation of the equivalent capacitance parameter along with the variation of the harmonic angular frequency And based on the variation of the equivalent capacitance parameter The overall degree of aging of the distribution cable insulation is determined.
5. The method for detecting insulation degradation of a distribution cable based on harmonic leakage according to claim 4, wherein the step of determining the node position corresponding to the insulation degradation defect of the distribution cable comprises: Under the condition of the same harmonic angular frequency, transversely comparing the amplitude values of the difference mode harmonic components at different node positions along the distribution cable; When the amplitude of the differential mode harmonic component at a certain node position is obviously increased relative to the adjacent node position or other node positions, or a obviously prominent local maximum value is formed in the differential mode harmonic component amplitude distribution of each node position along the distribution cable, the node position is judged to be the differential mode harmonic component abnormal node; And determining the abnormal node of the difference mode harmonic component as the node position corresponding to the insulation aging or defect of the distribution cable.
6. The harmonic leakage based power distribution cable insulation degradation detection method of claim 5, further comprising: Acquiring amplitude distribution of common-mode harmonic voltage components and difference-mode harmonic voltage components at node positions corresponding to the determined insulation ageing defects of the distribution cable under a plurality of harmonic angular frequencies; Selecting at least one of the common mode harmonic voltage component and the difference mode harmonic voltage component as a harmonic voltage amplitude acting on a corresponding insulating structure according to voltage bearing modes corresponding to different insulating structure types at the node positions ; Calculating the alternating current stress born by the corresponding insulating structure at the node position based on the following formula : Wherein, the For the electric field conversion coefficient corresponding to the type of the insulating structure, ; Based on the alternating current stress And evaluating the aging life of the corresponding insulating structure at the node position according to the following insulating material electrical aging life model: Wherein, the For the electrical aging life of the insulating material, And The life model parameters are determined through an accelerated aging test of the insulating material; in the process of calculating the insulating electrical aging life of the distribution cable, the electrical aging life is calculated Logarithmic transformation is performed to obtain: , wherein, , , 。
7. The method of harmonic leakage based power distribution cable insulation degradation detection of claim 6, wherein the step of acquiring magnetic induction signals generated by leakage harmonic currents at a plurality of node locations of the power distribution cable comprises: The double-magnetic-core sensing device arranged outside the distribution cable acquires magnetic induction intensity signals generated by leakage harmonic current, the double-magnetic-core sensing device comprises an inner magnetic core and an outer magnetic core, the inner magnetic core and the outer magnetic core are coaxially arranged along the radial direction of the distribution cable, the inner magnetic core is used for inhibiting the magnetic field influence generated by normal load current of the distribution cable, the outer magnetic core is used for sensing the magnetic induction intensity signals generated by leakage harmonic current, the magnetic induction intensity measurement bandwidth corresponding to the outer magnetic core covers 10Hz to 20kHz, and the detection sensitivity to the harmonic leakage current is not lower than 1mA.
8. Power distribution cable insulation aging detection device based on harmonic leakage, characterized by comprising: A magnetic field acquisition module for acquiring magnetic induction intensity signals generated by leakage harmonic current outside the tested distribution cable at a plurality of node positions of the distribution cable, A harmonic leakage current calculation module for determining a harmonic leakage current signal at each node location based on the magnetic induction intensity signal; a modal component extraction module for obtaining corresponding common-mode harmonic components and difference-mode harmonic components at a plurality of preselected harmonic angular frequencies based on the harmonic leakage current signals at each node location; The aging degree evaluation module is used for calculating a corresponding relation based on a frequency domain between common-mode harmonic components and the power distribution cable insulation equivalent parameters, respectively calculating to obtain the equivalent capacitance parameters of the power distribution cable insulation under the harmonic angular frequency, and determining the aging degree of the power distribution cable insulation based on the variation of the equivalent capacitance parameters under the harmonic angular frequency; And the aging position positioning module is used for carrying out transverse comparison analysis on the difference mode harmonic components at different node positions under the harmonic angular frequency, and determining the node position with the abnormal increase of the amplitude of the difference mode harmonic components as the node position corresponding to the insulation aging defect of the distribution cable.
9. An electronic device comprising a processor and a memory, the processor configured to execute a computer program stored in the memory to implement the harmonic leakage-based power distribution cable insulation degradation detection method of any one of claims 1 to 7.
10. A computer readable storage medium storing at least one instruction that when executed by a processor implements the harmonic leakage based distribution cable insulation degradation detection method of any one of claims 1 to 7.

Description

Power distribution cable insulation aging detection method and device based on harmonic leakage Technical Field The invention belongs to the technical field of cable insulation monitoring, and particularly relates to a method and a device for detecting insulation aging of a distribution cable based on harmonic leakage. Background Along with the continuous promotion of the construction of a novel power system and a novel power distribution network, the access proportion of new energy power generation equipment, a power electronic conversion device and various nonlinear loads in the power distribution network is continuously improved, and the harmonic content in the running environment of the power distribution system is obviously increased. The harmonic current can not only cause voltage distortion and additional loss in the operation process of the distribution cable, but also generate additional electric field stress and thermal stress in the cable insulation structure, accelerate the medium aging process of the insulation material, further induce insulation breakdown, electric leakage and ground fault, and cause adverse effects on the safety, reliability and power supply continuity of the distribution system. Statistics data show that a considerable part of power distribution cable faults are closely related to insulation aging, and the insulation aging generally has the characteristics of strong concealment, long development period, unobvious early characteristics and the like, and brings great challenges to operation and maintenance management. At present, the insulation state monitoring of the distribution cable mainly adopts the technical means of insulation resistance measurement, withstand voltage test, partial discharge detection, dielectric loss tangent measurement and the like. The insulation resistance measurement and withstand voltage test belongs to an off-line detection mode, needs to be implemented under the condition of power failure, not only affects normal power supply, but also possibly causes additional damage to cable insulation due to high electric stress test, and is difficult to meet the real-time monitoring requirement of a power distribution system in an on-line running state, and the identification capability of early-stage latent insulation aging is limited. Although the partial discharge detection technology can reflect part of the characteristics of insulation defects, the propagation attenuation of high-frequency signals in a distribution cable is obvious, multi-point distributed measurement is generally required, the system is complex, the cost is high, the detection technology is easily affected by on-site electromagnetic interference, the misjudgment and missed judgment risks are high, and the identification effect on slight aging or damp defects is limited. The dielectric loss tangent measurement method has higher requirements on test environment and measurement precision, the variation amplitude of dielectric loss parameters in the insulation aging process is smaller, the measurement error is easy to amplify and evaluate deviation, and the insulation aging state under the multi-factor coupling effect is difficult to comprehensively reflect due to the fact that the analysis is carried out on the basis of single electric parameters. In summary, the existing distribution cable insulation monitoring technology still has defects in the aspects of linearity, sensitivity, anti-interference capability, ageing degree quantitative evaluation and the like, and is difficult to meet the requirements of a novel power system on state sensing and refined operation and maintenance of the distribution cable. Disclosure of Invention The invention aims to provide a harmonic leakage-based power distribution cable insulation aging detection method and device, which can realize on-line monitoring, quantitative evaluation and defect positioning of the insulation aging state of a power distribution cable under the condition of electrified operation and improve the accuracy and reliability of monitoring. In order to achieve the above purpose, the present invention adopts the following technical scheme: The invention provides a power distribution cable insulation aging detection method based on harmonic leakage, which comprises the following steps: Acquiring magnetic induction intensity signals generated by leakage harmonic currents outside the tested distribution cable at a plurality of node positions of the distribution cable, and determining harmonic leakage current signals at each node position based on the magnetic induction intensity signals; Obtaining corresponding common mode harmonic components and difference mode harmonic components at a plurality of preselected harmonic angular frequencies based on the harmonic leakage current signals at each node location; calculating a corresponding relation based on a frequency domain between common-mode harmonic components and power distribution cab