CN-122017471-A - Signal injection parameter determination method for 10kV distribution line ground fault

CN122017471ACN 122017471 ACN122017471 ACN 122017471ACN-122017471-A

Abstract

The invention relates to the technical field of power maintenance and discloses a signal injection parameter determination method for a 10kV distribution line ground fault. The method comprises the steps of injecting broadband sweep pulses into a line, adaptively setting sweep steps according to the length of the line to obtain idle frequency spectrum characteristic data, calculating correlation among candidate frequency points in an available frequency band, selecting a plurality of characteristic frequency points with correlation lower than a threshold value, distributing injection energy according to the frequency band where each characteristic frequency point is located, enabling the energy to be inversely proportional to an attenuation coefficient, collecting feedback signals to extract a plurality of response characteristics to form fault characteristic data, comparing the fault characteristic data with a standard fault characteristic library to obtain fault types and matching degrees, encrypting and sampling in a sensitive frequency band and increasing energy if the matching degrees are lower than the threshold value, repeatedly extracting and matching, and calculating the fault distance by utilizing a phase deviation difference value of at least two characteristic frequency points. The self-adaptive determination of injection parameters is realized, and the detection success rate and the positioning accuracy of hidden faults are improved.

Inventors

Yue keyu
LIU YANDE
WANG MINZHEN
LI PEISONG
WANG ZHIGANG
WEI HONGXU
CAI CHAO
ZHENG YU
FU DALONG
WU WENXIN
JIA YUEBO
XU ZHENDONG

Assignees

国网吉林省电力有限公司辽源供电公司
浙江钰伟智能科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260410

Claims (10)

The signal injection parameter determination method for the ground fault of the 10kV distribution line is characterized by comprising the following steps of: S1, line spectrum mapping, namely injecting broadband sweep frequency pulse into a target line, adaptively setting sweep frequency stepping according to the length of the line, and collecting feedback signals to obtain no-load spectrum characteristic data comprising line input impedance, attenuation coefficient and background noise; s2, selecting characteristic frequency points, namely calculating the correlation between any two candidate frequency points in the available frequency band screened according to the attenuation coefficient and the background noise, and selecting a plurality of frequency points with the correlation lower than a set threshold value as the characteristic frequency points; S3, energy distribution, namely distributing injection energy to each characteristic frequency point according to the frequency band where the characteristic frequency point is located, so that the energy is inversely proportional to the attenuation coefficient of the frequency point, forming signals with different frequencies and energy combinations, and sequentially injecting the signals into a line; S4, fault feature extraction, namely collecting feedback signals under each frequency and energy combination, and extracting a plurality of response features to form fault feature data of the current line state; S5, performing fault matching and identification, namely performing similarity comparison on the current fault characteristic data and a pre-stored standard fault characteristic library to obtain a fault type and a matching degree thereof; S6, iterative optimization, namely if the matching degree is lower than a set threshold value, encrypting frequency sampling points in a sensitive frequency band corresponding to the primarily determined fault type, and repeating a fault feature extraction step and a fault matching and identifying step after increasing injection energy according to the degree of missing matching degree; S7, fault location, namely calculating a fault distance by using the phase offset difference value of at least two characteristic frequency points.
2. The method for determining signal injection parameters of a ground fault of a 10kV distribution line according to claim 1, wherein in the step of mapping the frequency spectrum of the line, the step frequency is determined according to the total length of the line and the propagation speed of the signal, so that the step frequency is inversely proportional to the length of the line and directly proportional to the propagation speed of the signal, and the spatial resolution of the frequency-swept signal can cover the whole line.
3. The method for determining the signal injection parameters of the grounding fault of the 10kV distribution line according to claim 1, wherein in the characteristic frequency point selection step, the correlation between two candidate frequency points is measured by respectively carrying out band-pass filtering on line input impedance functions corresponding to the two frequency points, calculating the absolute value of the inner product of the two functions after filtering, dividing the absolute value by the geometric mean value of the respective energy to obtain a ratio which is a correlation coefficient, judging that the two frequency points are irrelevant when the correlation coefficient is smaller than 0.3, and simultaneously retaining the correlation coefficient, and judging that the two frequency points are redundant when the correlation coefficient is larger than or equal to 0.3, and retaining only one with smaller attenuation coefficient.
4. The method for determining signal injection parameters of a ground fault of a 10kV distribution line according to claim 1, wherein in the characteristic frequency point selection step, the available frequency band is a frequency range with an attenuation coefficient lower than 3dB/km and a background noise lower than 1.5 times of the average power of the background noise.
5. The method for determining the signal injection parameters of the ground fault of the 10kV distribution line according to claim 1, wherein the energy distribution step is specifically that for a low-frequency band frequency point which is more than or equal to 20Hz and less than 500Hz, the injection energy is obtained by multiplying a ratio of a preset reference energy by a reference attenuation coefficient and an actual attenuation coefficient and multiplying the ratio by a product of the low-frequency band energy coefficient and a low-frequency weight coefficient; For the intermediate frequency band frequency points which are more than or equal to 500Hz and less than 1500Hz, the injection energy is the preset reference energy multiplied by the ratio of the reference attenuation coefficient to the actually measured attenuation coefficient and then multiplied by the product of the intermediate frequency band energy coefficient and the intermediate frequency weight coefficient; For the high-frequency band frequency points which are more than or equal to 1500Hz and less than or equal to 20kHz, the injection energy is obtained by multiplying preset reference energy by the ratio of a reference attenuation coefficient to an actual measured attenuation coefficient and multiplying the high-frequency band energy coefficient by a high-frequency weight coefficient; The low-frequency band energy coefficient, the medium-frequency band energy coefficient and the high-frequency band energy coefficient are sequentially decreased.
6. The method for determining signal injection parameters for a ground fault of a10 kV distribution line according to claim 1, wherein the plurality of response features extracted in the fault feature extraction step at least includes: amplitude response, i.e., the ratio of the feedback signal amplitude to the injection signal amplitude; phase offset, i.e., the difference between the phase of the feedback signal and the phase of the injection signal; harmonic distortion, i.e., the ratio of the square of the sum of the amplitudes of the subharmonic components in the feedback signal to the amplitude of the fundamental wave; A decay time constant, i.e. the time required for the impulse response envelope to drop to an initial value of 1/e; the degree of polarization, i.e., the difference of the amplitude of the feedback component parallel to the polarization direction of the injected signal minus the amplitude of the vertical component, divided by the sum of the two.
7. The method for determining the signal injection parameters of the grounding fault of the 10kV distribution line according to claim 1, wherein in the fault matching and identifying step, the similarity comparison simultaneously considers the amplitude difference and the morphological similarity between fault characteristic data and standard characteristic data, wherein the amplitude difference is set according to background noise level of each frequency point through weighted Euclidean distance measurement, the morphological similarity is set according to dynamic time regular distance measurement, the similarity value is obtained through exponential transformation after the weighted fusion of the two distances, and the fault type with the highest similarity is taken as an identification result.
8. The method for determining the signal injection parameters of the ground fault of the 10kV distribution line according to claim 1, wherein in the iterative optimization step, the degree of matching degree deficiency is 1 minus the current degree of matching, the energy increase multiple is set to be the sum of 1 and the degree of matching degree deficiency, and when the frequency sampling is encrypted, the original frequency sweep is reduced to one fourth step, and a new frequency sampling point is generated in a sensitive frequency band.
9. The method for determining the signal injection parameters of the grounding fault of the 10kV distribution line according to claim 1, wherein in the fault locating step, the fault distance is calculated by selecting a phase offset difference value of two characteristic frequency points, multiplying the phase offset difference value by a signal propagation speed, dividing by 4 pi and multiplying by an absolute value of a frequency difference of the two frequency points, and taking an average value of calculation results of a plurality of groups of different frequency point pairs as a final fault distance.
10. The method for determining the signal injection parameters of the grounding fault of the 10kV distribution line according to claim 1, wherein the standard fault characteristic library is pre-established in a laboratory environment by repeating the steps S1-S7 under different line conditions for a plurality of typical fault types including high-resistance grounding, insulator breakdown and lightning arrester damage to obtain standard characteristic data of each fault type, simultaneously counting response intensity distribution of each fault type under different frequency points, determining a continuous frequency band with highest response intensity as a sensitive frequency band of the fault type, and storing the continuous frequency band in association with the standard characteristic data.

Description

Signal injection parameter determination method for 10kV distribution line ground fault Technical Field The invention relates to the technical field of power maintenance, in particular to a signal injection parameter determination method for a 10kV distribution line ground fault. Background The signal injection method is one of the common techniques for positioning the ground fault of the power distribution network, and the basic principle is to inject a detection signal with a specific frequency into a line after the fault occurs, and the fault positioning is realized by tracking a signal path or detecting the characteristics of the signal. The method has the advantages of being free from the influence of the distributed capacitance of the circuit, intuitive in principle and the like, and is widely applied to actual operation and maintenance. However, conventional signal injection methods typically employ fixed frequency and fixed energy injection strategies, such as the 220Hz injection signal commonly used. Because the 10kV distribution line has a complex topological structure and numerous branches, and the impedance characteristics of the line dynamically change along with the length, the load and the environmental factors, the injection signals with fixed parameters are difficult to adapt to the actual working conditions of different lines. When the injection frequency falls on a resonance point or a high attenuation frequency band of a line, the device is possibly damaged due to the fact that the signal is too strong or the signal is too weak to be effectively detected, meanwhile, in the face of hidden faults such as high-resistance grounding and insulator breakdown, signals with fixed energy cannot penetrate through the fault point, and feedback signals are easily submerged in background noise. The prior art lacks a dynamic adjustment mechanism for injection parameters, so that the fault detection sensitivity is low, the positioning accuracy is poor, and the operation and maintenance requirements under complex working conditions are difficult to meet. Disclosure of Invention The invention aims to solve the technical problems that the prior art has low sensitivity and poor positioning accuracy on fault detection, and is difficult to meet the operation and maintenance requirements under complex working conditions, and therefore, the signal injection parameter determination method for the grounding fault of the 10kV distribution line is provided. In order to achieve the purpose, the application adopts the following technical scheme that the signal injection parameter determining method for the ground fault of the 10kV distribution line comprises the following steps: S1, line spectrum mapping, namely injecting broadband sweep frequency pulse into a target line, adaptively setting sweep frequency stepping according to the length of the line, and collecting feedback signals to obtain no-load spectrum characteristic data comprising line input impedance, attenuation coefficient and background noise; s2, selecting characteristic frequency points, namely calculating the correlation between any two candidate frequency points in the available frequency band screened according to the attenuation coefficient and the background noise, and selecting a plurality of frequency points with the correlation lower than a set threshold value as the characteristic frequency points; S3, energy distribution, namely distributing injection energy to each characteristic frequency point according to the frequency band where the characteristic frequency point is located, so that the energy is inversely proportional to the attenuation coefficient of the frequency point, forming signals with different frequencies and energy combinations, and sequentially injecting the signals into a line; S4, fault feature extraction, namely collecting feedback signals under each frequency and energy combination, and extracting a plurality of response features to form fault feature data of the current line state; S5, performing fault matching and identification, namely performing similarity comparison on the current fault characteristic data and a pre-stored standard fault characteristic library to obtain a fault type and a matching degree thereof; S6, iterative optimization, namely if the matching degree is lower than a set threshold value, encrypting frequency sampling points in a sensitive frequency band corresponding to the primarily determined fault type, and repeating a fault feature extraction step and a fault matching and identifying step after increasing injection energy according to the degree of missing matching degree; S7, fault location, namely calculating a fault distance by using the phase offset difference value of at least two characteristic frequency points. Preferably, in the step of line spectrum mapping, the setting mode of the sweep frequency step is that step frequency is determined according to the whole line length and the sig