CN-122017380-A - Method for detecting influence of frequent switching of power grid tide on short circuit resistance of transformer

CN122017380ACN 122017380 ACN122017380 ACN 122017380ACN-122017380-A

Abstract

The invention relates to the technical field of detection of power system equipment, in particular to a detection method for the influence of frequent switching of power grid tide on the short circuit resistance of a transformer, which comprises the steps of screening a high-risk target transformer based on historical operation data of the transformer, detecting the uninterrupted state of the target transformer, arranging a power failure overhaul window period, carrying out deep detection, comprehensively detecting the result, combining with a preset evaluation standard, diagnosing the short circuit resistance level of the transformer and outputting decision suggestions.

Inventors

ZHENG JIUJIANG
FU YAO
ZHAO ZHONGLIANG
LI JUN
ZHU MENGZHAO
GU CHAOLIANG
GUAN QINGGANG
CHEN XING
LUO JUNTING
ZHU QINGDONG

Assignees

沈阳变压器研究院有限公司
国网山东省电力公司电力科学研究院

Dates

Publication Date: 20260512
Application Date: 20251028

Claims (10)

1. The method for detecting the influence of the frequent switching of the power flow of the power grid on the short circuit resistance of the transformer is characterized by comprising the following steps of: S11, screening a high-risk target transformer based on historical operation data of the transformer; S12, detecting the uninterrupted power state of the target transformer to obtain vibration characteristics, frequency response and short circuit impedance parameters of the target transformer; s13, arranging a power failure overhaul window period for the target transformer, and performing deep detection on mechanical and physical states; And S14, integrating the uninterrupted power supply detection and the uninterrupted power supply detection result, combining a preset evaluation standard, diagnosing the short circuit resistance level of the transformer and outputting a decision suggestion.
2. The method for detecting the influence of frequent switching of power grid trend on the short circuit resistance of the transformer according to claim 1, wherein the method for detecting the influence of frequent switching of power grid trend on the short circuit resistance of the transformer is characterized by specifically comprising the following steps: s21, collecting data, namely collecting switching operation times records of all side breakers related to a target transformer, short circuit event data recorded by a fault wave recording device and action information of a protection system; s22, establishing an impact file, and quantitatively counting the times, the amplitude and the duration of short-circuit current impact born by the transformer based on the collected data; s23, judging the risk level, calculating the risk level of the transformer based on the impact file through a preset risk assessment model or threshold comparison, and determining the high risk level transformer as a target transformer; And S24, sequencing the priorities, namely comprehensively sequencing all screened high-risk target transformers according to the magnitude of risk indexes, the importance degree of the transformers in the power grid and the operational years of the transformers, and generating a transformer list for priority detection.
3. The method for detecting the influence of the frequent switching of the power flow of the power grid on the short-circuit resistance of the transformer according to claim 2 is characterized by comprising the following steps of: acquiring switching-on and switching-off operation times records of circuit breakers at each voltage class side of a transformer from a transformer substation monitoring system and an SCADA system, and counting switching frequencies in a specific time period; Extracting waveform data in which the current of the transformer winding exceeds the rated current by a specified multiple; And collecting protection action signals started during abnormal operation of the transformer from the relay protection information management system, wherein the protection action signals comprise starting and outlet action records of differential protection, overcurrent protection and quick-break protection.
4. The method for detecting the influence of frequent switching of power flow of a power grid on the short-circuit resistance of a transformer according to claim 3, wherein the method comprises the following steps of: for each short circuit event, extracting and recording key parameters including a short circuit current peak value, a short circuit current duration time and a current attenuation characteristic from fault recording data; counting all short-circuit events to form an impact event list ordered in a time sequence; And calculating the total times of short-circuit impact events in a specific time window and the impact times distribution of different amplitude intervals.
5. The method for detecting the influence of frequent power flow switching on the short circuit resistance of the transformer according to claim 4, wherein when the risk level is determined, a weighted accumulation evaluation model based on the number of impact times and the impact strength is adopted to calculate a risk index, the calculated risk index R is compared with a plurality of preset threshold intervals, the transformer is divided into a plurality of risk levels according to the comparison result, and the principle expression is as follows: ; Wherein, the As an index of the risk (risk) of, For a weighting coefficient corresponding to the i-th amplitude interval, the weighting coefficient increases non-linearly with increasing current amplitude, The number of times of impact that the short-circuit current amplitude falls in the ith preset interval.
6. The method for detecting the influence of frequent power flow switching on the short circuit resistance of the transformer according to claim 5, wherein the method for detecting the uninterrupted power supply state of the target transformer is characterized by comprising the following steps: S31, high-frequency transient vibration measurement, namely arranging a plurality of vibration sensors on the surface of a transformer oil tank, recording vibration signals in the switching operation process, analyzing the spectrum characteristics of the vibration signals, comparing the spectrum characteristics with fingerprint spectrums in a healthy state, and identifying main frequency offset, amplitude variation and low-frequency component abnormality, wherein the sampling frequency of the vibration sensors is higher than 10kHz, and the spectrum analysis range covers 10Hz to 100kHz; S32, frequency response analysis, namely injecting sweep frequency signals into the transformer through the head end and the tail end of the winding in a state that the transformer is stopped but the transformer is not hung, measuring a transfer function, transversely comparing a past test result with a longitudinal comparison three-phase winding transfer function, and identifying radial torsion, axial torsion and integral looseness of the winding, wherein the frequency range of the sweep frequency signals is 100Hz to 10MHz; S33, short-circuit impedance testing, namely measuring the short-circuit impedance of each pair of windings by adopting a low-voltage tester, and comparing the short-circuit impedance with a factory value and a last test value to judge the change of the geometric shape of the windings.
7. The method for detecting the influence of the frequent switching of the power flow of the power grid on the short-circuit resistance of the transformer according to claim 6, wherein the method comprises the following steps of: The sensor arrangement comprises the steps of respectively arranging at least one vibration sensor on a high-pressure side, a low-pressure side and a neutral point side of the outer wall of the transformer oil tank; The signal recording is that when the no-load switch-on and the on-load voltage regulating switch of the transformer are operated, the vibration signal recording is synchronously triggered, and the vibration signals in the time windows of 0.5s before and after the operation are recorded; Performing spectrum analysis, namely performing fast Fourier transform on the recorded vibration signals to obtain vibration spectrum characteristics in a frequency range from 10Hz to 1000 Hz; And (3) spectrum comparison, namely calculating amplitude deviation and dominant frequency deviation of the current vibration spectrum and the health state reference spectrum on the characteristic frequency points.
8. The method for detecting the influence of frequent switching of power flow of a power grid on the short-circuit resistance of a transformer according to claim 7, wherein the method comprises the following steps of: the testing wiring is used for respectively connecting an excitation end and a measurement end of the frequency response analyzer to two ends of a winding to be tested in the state that the transformer is in a shutdown state; Frequency sweep test, namely carrying out frequency sweep test in a logarithmic mode in a frequency range from 100Hz to 10MHz, and recording a voltage transfer function H (f); and a curve analysis step of calculating the similarity degree between the current frequency response curve and the reference curve by adopting a correlation coefficient method.
9. The method for detecting the influence of frequent power flow switching on the short circuit resistance of the transformer according to claim 8, wherein the method for detecting the mechanical and physical states deeply comprises the following steps when a power failure maintenance window period is arranged for the target transformer: s41, visually checking a winding and an iron core, entering a transformer oil tank, and checking whether the winding has concave-convex deformation, a cushion block falls off or shifts, whether a press nail is loose, whether a press nail displacement indicator acts, and whether an iron core clamping piece and a pull belt have cracks; S42, measuring the winding compaction force, namely measuring the residual pretightening force of the press nail by using a special hydraulic device or a torque wrench, and judging whether the residual pretightening force is lower than the minimum pretightening force requirement specified by a manufacturer; S43, auxiliary electrical test, measuring insulation resistance and absorption ratio, evaluating insulation moisture condition, measuring direct current resistance, checking contact state of wire connection point, lead wire and tapping switch contact.
10. The method for detecting the influence of frequent power flow switching on the short circuit resistance of the transformer according to claim 9, wherein when the uninterrupted power supply detection and the uninterrupted power supply detection result are combined, and a preset evaluation standard is combined, the short circuit resistance level of the transformer is diagnosed and a decision suggestion is output, the preset evaluation standard comprises: A11 FRA evaluation, namely judging as abnormal when one of the spectrum deviation larger than 3.0 and the correlation coefficient smaller than 0.90 occurs and the short-circuit impedance change is larger than 2 percent; A12, short-circuit impedance evaluation, wherein when the absolute value of the change is more than 3%, the deformation is judged to be obvious; A13, vibration spectrum evaluation, namely judging that the state is abnormal when one of the deviation of the main vibration frequency point exceeds 10% and the amplitude change exceeds 30% occurs; a14, evaluating the compaction force, namely judging that the compaction fails when the residual pre-tightening force is lower than the minimum requirement; a15, combining multidimensional index association analysis, outputting four short-circuit resistance grades of health, attention, abnormality and severity, and correspondingly giving decision suggestions of continuing operation, shortening detection period, checking in a limited period and immediately exiting operation.

Description

Method for detecting influence of frequent switching of power grid tide on short circuit resistance of transformer Technical Field The invention relates to the technical field of power system equipment detection, in particular to a detection method for influence of frequent power flow switching of a power grid on short circuit resistance of a transformer. Background With the increasing complexity of the power grid structure and the large-scale access of new energy power generation, the power grid operation mode becomes more flexible, and the frequent switching of the power flow direction and the power flow of the power transmission line becomes normal. The frequent operation leads to a remarkable increase in the number of times that the transformer bears short-circuit current impact, and although the single impact strength may not reach the extreme conditions of the standard short-circuit test, the cumulative effect and fatigue effect of the transformer can cause progressive damage to the mechanical structure of the transformer, especially the irreversible influence to key components such as windings, a pressing device and the like, so that the short-circuit resistance of the transformer is gradually reduced, and serious potential safety hazards are formed. The detection of the short-circuit resistance of the transformer at present mainly depends on the traditional preventive test and regular maintenance, and the methods have obvious limitations that the conventional electrical test is difficult to effectively find the hidden defect of the mechanical structure, the power failure hanging cover has long detection period, high cost and destructiveness, the existing state monitoring means is single, the assessment capability of the accumulated effect and the fatigue damage is lacked, and more importantly, the systematic detection scheme and the assessment standard for the frequent tide switching working condition are lacked, and the accurate assessment and the predictive maintenance of the short-circuit resistance of the transformer cannot be realized. The invention provides a systematic detection and evaluation method, which establishes a multi-parameter fusion evaluation system by combining historical operation data analysis, uninterrupted power state monitoring and special power failure detection, can quantitatively diagnose the mechanical state degradation of a transformer caused by frequent power flow switching, timely find hidden defects, evaluate the residual short-circuit resistance, provide scientific basis for predictive maintenance and replacement decision of equipment, and finally realize the transition from passive overhaul to active prediction. Disclosure of Invention In order to overcome the problems in the background technology, the invention provides a detection method for the influence of frequent power flow switching of a power grid on the short circuit resistance of a transformer. The technical scheme of the invention is that the method for detecting the influence of frequent switching of power flow of a power grid on the short circuit resistance of a transformer comprises the following steps: S11, screening a high-risk target transformer based on historical operation data of the transformer; S12, detecting the uninterrupted power state of the target transformer to obtain vibration characteristics, frequency response and short circuit impedance parameters of the target transformer; s13, arranging a power failure overhaul window period for the target transformer, and performing deep detection on mechanical and physical states; And S14, integrating the uninterrupted power supply detection and the uninterrupted power supply detection result, combining a preset evaluation standard, diagnosing the short circuit resistance level of the transformer and outputting a decision suggestion. Preferably, when screening the high-risk target transformer based on the transformer historical operation data, the method specifically comprises the following steps: s21, collecting data, namely collecting switching operation times records of all side breakers related to a target transformer, short circuit event data recorded by a fault wave recording device and action information of a protection system; s22, establishing an impact file, and quantitatively counting the times, the amplitude and the duration of short-circuit current impact born by the transformer based on the collected data; s23, judging the risk level, calculating the risk level of the transformer based on the impact file through a preset risk assessment model or threshold comparison, and determining the high risk level transformer as a target transformer; And S24, sequencing the priorities, namely comprehensively sequencing all screened high-risk target transformers according to the magnitude of risk indexes, the importance degree of the transformers in the power grid and the operational years of the transformers, and generating a transformer list f