CN-121978411-A - Impedance testing method, device and system for low-frequency transformer

CN121978411ACN 121978411 ACN121978411 ACN 121978411ACN-121978411-A

Abstract

The application relates to the technical field of impedance testing, in particular to a method, a device and a system for testing the impedance of a low-frequency transformer, wherein the method comprises the steps of collecting various electrical data of the low-frequency transformer to be tested at each frequency point; the method comprises the steps of evaluating peak fluctuation degree and baseline drift degree of various electric data in the impedance test process of the low-frequency transformer to be tested, obtaining interference degree of various electric data in the impedance test process of the low-frequency transformer to be tested, obtaining comprehensive interference degree in the impedance test process of the low-frequency transformer to be tested, denoising various electric data by utilizing a wavelet transformation algorithm, wherein wavelet threshold values of the wavelet transformation algorithm are adjusted through the comprehensive interference degree, an impedance curve of the low-frequency transformer to be tested is constructed, and evaluating deformation and abrasion conditions of an internal winding of the low-frequency transformer to be tested, so that accurate impedance test information is provided. The application aims to improve the impedance test precision of a low-frequency transformer.

Inventors

YANG DEHAO
ZHANG JUAN
WU YONG
ZHAO YINGLU
ZHANG YAN
LIANG ZHENWEI
WU YIHAO
ZHU YINGNA
ZHANG LINYIN
GONG QINGQING

Assignees

国网河南省电力公司新野县供电公司

Dates

Publication Date: 20260505
Application Date: 20260319

Claims (10)

1. A method for testing impedance of a low frequency transformer, the method comprising the steps of: Injecting excitation signals into the low-frequency transformer to be tested through the sweep frequency impedance tester, and collecting various electric data of the low-frequency transformer to be tested at each frequency point; Carrying out fluctuation analysis on various electric data at all frequency points respectively to evaluate peak fluctuation degrees of various electric data in the impedance test process of the low-frequency transformer to be tested, and respectively combining the baseline drift degrees of various electric data in the impedance test process of the low-frequency transformer to be tested to acquire the interfered degrees of various electric data in the impedance test process of the low-frequency transformer to be tested so as to obtain the comprehensive interference degrees in the impedance test process of the low-frequency transformer to be tested; And obtaining the winding deformation abrasion degree in the impedance testing process of the low-frequency transformer to be tested through the degree of deviation of the impedance curve from the power frequency in a preset middle-high frequency band and the rising condition of the preset low frequency band, and evaluating the internal winding deformation abrasion condition of the low-frequency transformer to be tested so as to provide accurate impedance testing information.
2. The method for testing impedance of low frequency transformer according to claim 1, wherein the peak fluctuation degree evaluation process is as follows: Recording each frequency point nearest to each power frequency integer multiple as each power frequency multiple frequency point; calculating the average value of various electric data under the neighboring frequency points of each power frequency multiple frequency point, and calculating the difference value between the various electric data under each power frequency multiple frequency point and the average value; Recording the dispersion of various electric data of each power frequency multiple frequency point and the adjacent frequency points thereof as data dispersion; And the peak fluctuation degree is evaluated by integrating the difference values of various electric data under all power frequency multiple frequency points and the data dispersion degree.
3. The method for testing impedance of low frequency transformer according to claim 1, wherein the method for evaluating baseline drift is as follows: calculating the impedance under each frequency point through all kinds of electric data, marking a fitting curve when the impedance under all frequency points in the preset low frequency range are arranged according to the ascending order of frequency as an impedance fitting curve, and marking the dispersion of the normalized value of the curvature of the impedance fitting curve at all frequency points in the preset low frequency range as the curvature dispersion; the fitting curve when various electric data in all frequency points in the preset low frequency range are arranged according to the ascending order of frequency is recorded as an electric data fitting curve, and the dispersion of the normalized value of the slope of the electric data fitting curve at all frequency points in the preset low frequency range is recorded as the slope dispersion; The baseline drift is positively correlated with the curvature dispersion and the slope dispersion, respectively.
4. The method of claim 1, wherein the disturbance rejection level is a normalized value of a product of the peak waviness level and the baseline drift level.
5. The method for testing impedance of low-frequency transformer according to claim 1, wherein the obtaining process of the comprehensive interference degree is as follows: And according to the interference degrees of all kinds of electrical data in the impedance test process of the low-frequency transformer to be tested, acquiring a comprehensive score by adopting a comprehensive evaluation method, and taking the comprehensive score as the comprehensive interference degree.
6. The method for testing impedance of low frequency transformer according to claim 1, wherein said adjusting method of wavelet threshold is to superimpose the product of preset initial wavelet threshold, preset weight coefficient and said integrated interference level on the basis of preset initial wavelet threshold.
7. The method for testing the impedance of the low-frequency transformer according to claim 1, wherein the winding deformation abrasion degree is obtained by the following steps: taking the difference between the normalized value of the slope of the impedance curve at each frequency point and the normalized value of the slope at the adjacent previous frequency point as an index of an exponential function based on a natural constant, wherein the frequency at each frequency point is larger than the frequency at the adjacent previous frequency point; Calculating arithmetic mean of calculation results of the exponential function corresponding to all frequency points in the preset low frequency band; and the deformation abrasion degree of the winding is obtained by combining the degree of deviation of the impedance curve from the power frequency of the preset medium-high frequency band and the arithmetic average.
8. The method for testing impedance of low-frequency transformer according to claim 7, wherein the method for calculating deformation and abrasion degree of winding comprises: arranging the impedance at all frequency points in the preset medium-high frequency range according to the ascending order of the frequency, extracting each wave crest, dividing the arrangement result into each medium-high frequency impedance section through the wave crest, and calculating the difference value of the average value of the frequencies of all the frequency points of the impedance in each medium-high frequency impedance section compared with the power frequency; the winding deformation wear degree is a normalized result of a weighted sum of the arithmetic mean and the sum value.
9. A low frequency transformer impedance testing apparatus employing a low frequency transformer impedance testing method as claimed in claim 1, wherein said apparatus comprises: The electric data acquisition module is used for injecting excitation signals into the low-frequency transformer to be tested through the sweep frequency impedance tester and collecting various electric data of the low-frequency transformer to be tested at each frequency point; The interference analysis module is used for respectively carrying out fluctuation analysis on various electric data at all frequency points so as to evaluate peak fluctuation degrees of various electric data in the impedance test process of the low-frequency transformer to be tested, respectively combining the baseline drift degrees of various electric data in the impedance test process of the low-frequency transformer to be tested to obtain the interfered degrees of various electric data in the impedance test process of the low-frequency transformer to be tested, and further obtaining the comprehensive interference degrees in the impedance test process of the low-frequency transformer to be tested; The impedance testing module is used for denoising various electric data by utilizing a wavelet transformation algorithm, wherein the wavelet threshold value of the wavelet transformation algorithm is adjusted by the comprehensive interference degree, an impedance curve of the low-frequency transformer to be tested is constructed by all electric data after denoising, and the winding deformation abrasion degree of the low-frequency transformer to be tested in the impedance testing process is obtained by the degree of deviation of the impedance curve from the power frequency in a preset middle-high frequency band and the rising condition of the preset low frequency band, so that the deformation abrasion condition of the internal winding of the low-frequency transformer to be tested is evaluated to provide accurate impedance testing information.
10. A low frequency transformer impedance testing system comprising a memory, a processor and a computer program stored in said memory and running on said processor, characterized in that said processor, when executing said computer program, realizes the steps of a low frequency transformer impedance testing method according to any of claims 1-8.

Description

Impedance testing method, device and system for low-frequency transformer Technical Field The application relates to the technical field of impedance testing, in particular to a method, a device and a system for testing impedance of a low-frequency transformer. Background The low frequency transformer is a core device of the power system, and its impedance parameters directly affect the short-circuit current, the voltage regulation rate, the load distribution during parallel operation and the system stability, so that the accurate measurement of the impedance is relevant for health assessment, fault diagnosis and preventive maintenance of the power device. The traditional sweep frequency impedance method can solve the technical defects of insufficient sensitivity and fuzzy judgment of a frequency response analysis method of the traditional short circuit impedance method, but is influenced by complex electromagnetic testing environment in the impedance testing process of the low-frequency transformer, external strong interference signals can be directly coupled into a testing loop in a mode of space induction or power conduction and the like, the precision of a measuring result is seriously reduced, meanwhile, the integrity and the reliability of an impedance curve can be damaged due to early-stage and slight deformation and abrasion of a winding, wrong diagnosis information is introduced, misjudgment and omission judgment of the impedance testing of the low-frequency transformer are caused, and the safe operation of a power system is threatened. Disclosure of Invention In view of the foregoing, it is necessary to provide a method, an apparatus and a system for testing impedance of a low-frequency transformer, which improve the impedance testing precision of the low-frequency transformer compared with the conventional method for testing impedance of the low-frequency transformer: in a first aspect, an embodiment of the present application provides a method for testing impedance of a low frequency transformer, including the steps of: Injecting excitation signals into the low-frequency transformer to be tested through the sweep frequency impedance tester, and collecting various electric data of the low-frequency transformer to be tested at each frequency point; Carrying out fluctuation analysis on various electric data at all frequency points respectively to evaluate peak fluctuation degrees of various electric data in the impedance test process of the low-frequency transformer to be tested, and respectively combining the baseline drift degrees of various electric data in the impedance test process of the low-frequency transformer to be tested to acquire the interfered degrees of various electric data in the impedance test process of the low-frequency transformer to be tested so as to obtain the comprehensive interference degrees in the impedance test process of the low-frequency transformer to be tested; And obtaining the winding deformation abrasion degree in the impedance testing process of the low-frequency transformer to be tested through the degree of deviation of the impedance curve from the power frequency in a preset middle-high frequency band and the rising condition of the preset low frequency band, and evaluating the internal winding deformation abrasion condition of the low-frequency transformer to be tested so as to provide accurate impedance testing information. In one embodiment, the peak fluctuation degree evaluation process is as follows: Recording each frequency point nearest to each power frequency integer multiple as each power frequency multiple frequency point; calculating the average value of various electric data under the neighboring frequency points of each power frequency multiple frequency point, and calculating the difference value between the various electric data under each power frequency multiple frequency point and the average value; Recording the dispersion of various electric data of each power frequency multiple frequency point and the adjacent frequency points thereof as data dispersion; And the peak fluctuation degree is evaluated by integrating the difference values of various electric data under all power frequency multiple frequency points and the data dispersion degree. In one embodiment, the method for evaluating the baseline drift is as follows: calculating the impedance under each frequency point through all kinds of electric data, marking a fitting curve when the impedance under all frequency points in the preset low frequency range are arranged according to the ascending order of frequency as an impedance fitting curve, and marking the dispersion of the normalized value of the curvature of the impedance fitting curve at all frequency points in the preset low frequency range as the curvature dispersion; the fitting curve when various electric data in all frequency points in the preset low frequency range are arranged according to the ascending order of frequency