Evaluation method for abnormal vibration of transformer caused by stray current

Abstract

The invention discloses a method for evaluating abnormal vibration of a transformer caused by stray current, and the method comprises the following steps: synchronously monitoring the waveform of neutral point stray current of an affected transformer and the vibration acceleration of the surface of a transformer box body, carrying out the correlation analysis of the stray current and the peak-valley value of the vibration acceleration, and calculating the abnormal vibration of the transformer caused by the stray current. The method comprises the following steps: firstly, obtaining the maximum correlation coefficient and the lag time of the vibration acceleration on stray current, judging the correlation between the abnormal vibration of the transformer and stray current invasion, secondly, carrying out modal analysis on the abnormal vibration acceleration to realize alarm of the abnormal vibration acceleration caused by the stray current, and finally deducing the stray current sensitivity threshold of the vibration of the transformer. And real-time early warning of abnormal vibration of the transformer is carried out according to the stray current monitoring data. Abnormal vibration alarm of stray current of the transformer can be realized, and safe and reliable operation of the transformer is maintained.

Description

Technical Field

[0001] The invention relates to the technical field of transformer detection, and in particular to a method for evaluating abnormal vibration of a transformer caused by stray current. Background Art

[0002] Subway stray current is the leakage current in the subway system during operation. The intrusion of subway stray current into the urban power grid will cause abnormal vibration of the transformer, which is specifically manifested as unstable "howling" of the transformer due to the changing stray current. The abnormal vibration of the transformer induces mechanical failure of the transformer body, such as loosening of the core, winding, clamps and bolts.

[0003] Once the hazard of DC bias magnetization of transformers is discovered during the operation of urban power grids, it is necessary to pay more attention to it. On-site detection data show that stray current is a bipolar current of low-frequency nature. How to determine whether stray current causes abnormal vibration of transformers is the primary issue, and how to analyze the correlation between stray current and vibration acceleration based on the detection data of stray current and vibration acceleration is the core issue. The mode of transformer vibration acceleration is very complex, and how to further separate the abnormal vibration characteristics caused by stray current is a major problem at present. Finally, it is also necessary to sort out the abnormal vibration characteristics of the transformer and obtain the stray current warning threshold of transformer vibration to give full play to the advantages of real-time warning of stray current online monitoring system. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for evaluating abnormal vibration of a transformer caused by stray current, which aims to solve the problems in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for evaluating abnormal vibration of a transformer caused by stray current, comprising the following steps:

[0006] Step S1: synchronously monitor and record the stray current of the neutral point of the affected transformer and the vibration acceleration of the surface of the affected transformer box;

[0007] Step S2: performing a peak-to-valley correlation analysis of the recorded stray current and vibration acceleration taking into account the time lag to obtain the maximum correlation coefficient and lag time of the stray current and vibration acceleration;

[0008] Step S3: When the maximum correlation coefficient between stray current and vibration acceleration is greater than 0.75 and the lag time is less than 40ms, it is determined that the abnormal vibration of the affected transformer is caused by the stray current, and the process goes to step S4; otherwise, a relevant conclusion is given and the on-site monitoring of the stray current and vibration acceleration of the affected transformer is cancelled;

[0009] Step S4: Perform modal analysis on the abnormal vibration of the affected transformer and determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is given and the process goes to step S5. If not, a relevant conclusion is given and the on-site monitoring of stray current and vibration acceleration is canceled.

[0010] Step S5: Take 50% of the extreme value of the upper envelope of the vibration acceleration as the reference value, and take out the mean value of the stray current I when all vibration accelerations reach the reference value. 50％ , Definition I 50％ is the stray current sensitivity threshold of the affected transformer; retains on-site monitoring of stray current and releases on-site monitoring of vibration acceleration.

[0011] Furthermore, the specific process of step S2 is as follows:

[0012] Step S2.1: taking the absolute value of the stray current data with a resolution of 10sps and resampling it to 10ksps;

[0013] Step S2.2: Take out the upper envelope A of the vibration acceleration A + and lower envelope A - ;

[0014] Step S2.3: Set the data offset of the resampled stray current n=0;

[0015] Step S2.4: Calculate the stray current I and the upper envelope A respectively + The correlation coefficient k + , stray current I and lower envelope A - The correlation coefficient k - ;

[0016] Step S2.5: Update k + The maximum value and k - The minimum value of

[0017] Step S2.6: When the data offset n<1000, go to step S2.7, otherwise go to step S2.8;

[0018] Step S2.7: the data offset of the resampled stray current is n=n+1, the stray current I is offset by n sampling points, and the process goes to step S2.4;

[0019] Step S2.8: Output k + The maximum value and corresponding offset n + and k - The minimum value and corresponding offset n - ,Finish.

[0020] Furthermore, the upper envelope lag time t of the vibration acceleration A+ =n + / 10ms, hysteresis time t of the lower envelope of vibration acceleration A - =n - / 10ms; the lag time between stray current and vibration acceleration is t + and t - The maximum correlation coefficient between stray current and vibration acceleration is 0.5 times k + The maximum value minus 0.5 times k - The maximum value of .

[0021] Furthermore, the specific process of step S4 is as follows:

[0022] Step S4.1: Perform modal analysis on the vibration acceleration of the affected transformer under the action of the maximum stray current;

[0023] Step S4.2: Perform modal analysis on the vibration acceleration of the affected transformer under the action of minimum stray current;

[0024] Step S4.3: determining the abnormal vibration acceleration of the affected transformer based on the modal analysis of steps S4.1 and S4.2;

[0025] Step S4.4: performing displacement modal comparison analysis on the abnormal vibration acceleration of the affected transformer;

[0026] Step S4.5: Based on the analysis in step S4.4, determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is triggered and the process goes to step S5. If not, it is considered that the abnormal vibration of the affected transformer induced by stray current intrusion is not strong, and a relevant conclusion is drawn, and the on-site monitoring of stray current and vibration acceleration is canceled.

[0027] Furthermore, the specific process of step S4.1 is as follows:

[0028] Step S4.11: Collect vibration acceleration data A(t p ), t p Indicates the time one second before and after the absolute peak moment of stray current;

[0029] Step S4.12: A(t p ) is subjected to fast Fourier transform, and A(t p )’s maximum vibration acceleration spectrum a(f), maximum vibration displacement spectrum d(f);

[0030] Step S4.13: Set the frequency band range to [25Hz, 500Hz], and collect 10 frequency spectrum points a (f k) and the maximum vibration displacement frequency d(f k ), k=1,2,...,10; f k represents the kth frequency corresponding to the peak vibration acceleration;

[0031] d(f) is expressed as:

[0032]

[0033] Where f represents the frequency of the spectrum.

[0034] Furthermore, the specific process of step S4.2 is as follows:

[0035] Step S4.21: Collect the vibration acceleration data A(t 0 );t 0 Indicates the two-second period during which the mean absolute value of the stray current is the smallest;

[0036] Step S4.22: A(t 0 ) is subjected to fast Fourier transform, and A(t 0 )'s minimum vibration acceleration spectrum a 0 (f) and minimum vibration displacement spectrum d 0 (f);

[0037] Step S4.23: Set the frequency range to [25Hz, 500Hz], and collect 10 frequency points a with the minimum peak vibration acceleration. 0 (f 0k ) and minimum vibration displacement frequency d 0 (f 0k ), k=1,2,...,10; f 0k Indicates a 0 The kth frequency of the corresponding peak vibration acceleration;

[0038] d 0 (f) is expressed as:

[0039]

[0040] Furthermore, the specific process of step S4.3 is as follows: compare the frequency points of abnormal vibration acceleration, and k As the research object, compared with f k and f 0k , k=1,2,...,10, when f k and f 0k The frequency points are close to each other. Specifically, if the frequency difference is within 1Hz, they are considered to be the same frequency point. 0kIf the difference between all frequency points exceeds 1Hz, the frequency point is considered to be a new excitation frequency point, that is, abnormal vibration acceleration; all excitation frequency point information is output.

[0041] Furthermore, the specific process of step S4.4 is: taking the displacement of the spectrum as the research object, taking out the maximum vibration displacement frequency d of the same frequency k and minimum vibration displacement frequency d 0k , k = 1, 2, ..., 10, and calculate the displacement surge multiple X c :

[0042]

[0043] In the formula, c is the number of the same frequency point, m is the number of the same frequency points; a(f c ) represents the maximum vibration acceleration frequency; a 0 (f c ) represents the minimum vibration acceleration frequency; d(f c ) represents the maximum vibration displacement frequency; d 0 (f c ) represents the minimum vibration displacement frequency.

[0044] Furthermore, the specific process of step S4.5 is as follows: when the displacement surges by multiple X c If the sum is greater than 10, an abnormal vibration alarm is issued; calculate the new excitation frequency information for the displacement surge multiple, and obtain the new displacement surge multiple Y q :

[0045]

[0046]

[0047]

[0048] In the formula, q represents the frequency point number, f q represents the frequency of the qth frequency point, a(f q ) indicates the frequency is f q The maximum vibration acceleration, a 0 (f k ) indicates the frequency is f k The minimum vibration acceleration, d(f q ) indicates the frequency is f q Maximum vibration displacement; d 0max Represents the maximum displacement component of the minimum vibration acceleration spectrum;

[0049] When the new displacement surge multiple is greater than 1, an abnormal vibration alarm is issued;

[0050] When an abnormal vibration alarm is issued, the process goes to step S5. Otherwise, it is considered that the abnormal vibration of the affected transformer induced by the stray current intrusion is not strong, and a relevant conclusion is given and the on-site monitoring of the stray current and vibration acceleration is cancelled.

[0051] Furthermore, in step S5, when the absolute value of the stray current measurement data is greater than the stray current sensitivity threshold, a real-time warning is issued that the stray current causes abnormal vibration acceleration of the affected transformer.

[0052] Compared with the existing technology, the present invention has the following beneficial effects:

[0053] (1) The present invention realizes the alarm of abnormal vibration acceleration caused by stray current through modal analysis of abnormal vibration acceleration, deduce the stray current sensitivity threshold of transformer vibration, and performs real-time early warning of abnormal vibration of the transformer based on stray current monitoring data; it can provide technical reference for monitoring and early warning of DC bias magnetic risk of transformer caused by stray current intrusion.

[0054] (2) The present invention can clarify the causal relationship between dynamic stray current and its abnormal vibration acceleration, deeply analyze the stray current vibration mode of the transformer, and obtain the threshold value of the transformer vibration tolerance stray current, thereby realizing the transformer stray current abnormal vibration alarm and maintaining the safe and reliable operation of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention is a schematic diagram of the synchronous measurement structure of the neutral point stray current and the transformer box surface vibration acceleration. DETAILED DESCRIPTION

[0056] The present invention provides a technical solution: a method for evaluating abnormal vibration of a transformer caused by stray current, comprising the following steps:

[0057] Step S1: synchronously monitor and record the stray current at the neutral point of the affected transformer and the vibration acceleration on the surface of the affected transformer box.

[0058] The specific process of step S1 is: using a stray current sensor and a vibration acceleration sensor, carry out synchronous monitoring of the stray current at the neutral point of the affected transformer and the stray current and vibration acceleration at the middle of the surface of the affected transformer box 2m above the ground for no less than 24 hours, and record the complete stray current I data and vibration acceleration A data, such as Figure 1 As shown; the time resolution of the stray current I data is 10sps, and the time resolution of the vibration acceleration A data is 10ksps.

[0059] Step S2: performing a peak-to-valley correlation analysis of the stray current and vibration acceleration recorded in step S1 with time lag considered, and obtaining a maximum correlation coefficient and lag time of the stray current and vibration acceleration.

[0060] Step S2.1: Take the absolute value of the stray current data with a resolution of 10sps and resample it to 10ksps.

[0061] Step S2.2: Take out the upper envelope A of the vibration acceleration A + and lower envelope A - .

[0062] Step S2.3: Set the data offset of the resampled stray current n=0.

[0063] Step S2.4: Calculate the stray current I and the upper envelope A respectively + The correlation coefficient k + , stray current I and lower envelope A - The correlation coefficient k - .

[0064] Step S2.5: Update k + The maximum value and k - The minimum value of .

[0065] Step S2.6: When the data offset n<1000, go to step S2.7, otherwise go to step S2.8.

[0066] Step S2.7: The data offset of the resampled stray current is n=n+1, the stray current I is offset by n sampling points, and the process goes to step S2.4.

[0067] Step S2.8: Output k + The maximum value and its corresponding offset n + and k - The minimum value of and its corresponding offset n - ,Finish.

[0068] Get: The upper envelope lag time t of vibration acceleration A + =n + / 10ms, hysteresis time t of the lower envelope of vibration acceleration A - =n - / 10ms; the lag time between stray current and vibration acceleration is t + and t - The maximum correlation coefficient between stray current and vibration acceleration is 0.5 times k + The maximum value minus 0.5 times k - The maximum value of .

[0069] Step S3: When the maximum correlation coefficient between stray current and vibration acceleration is greater than 0.75 and the lag time is less than 40ms, it is determined that the abnormal vibration of the affected transformer is caused by the stray current, and the process goes to step S4; otherwise, it is determined that the abnormal vibration of the affected transformer is not strongly correlated with the stray current, and a relevant conclusion is given, and the on-site monitoring of the stray current and vibration acceleration of the affected transformer is lifted.

[0070] Step S4: Perform modal analysis on the abnormal vibration of the affected transformer and determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is triggered and the process goes to step S5. If not, it is considered that the abnormal vibration of the affected transformer induced by stray current intrusion is not strong, and a relevant conclusion is given, and the on-site monitoring of stray current and vibration acceleration is canceled.

[0071] Step S4.1: Perform a modal analysis on the vibration acceleration of the affected transformer under the action of the maximum stray current.

[0072] Step S4.11: Collect vibration acceleration data A(t p ), t p Indicates the time one second before and after the absolute peak of the stray current.

[0073] Step S4.12: A(t p ) is subjected to fast Fourier transform (FFT) to obtain A(t p )’s maximum vibration acceleration spectrum a(f), maximum vibration displacement spectrum d(f);

[0074] d(f) is expressed as:

[0075]

[0076] Where f represents the frequency of the spectrum.

[0077] Step S4.13: Set the frequency range to [25Hz, 500Hz], and collect 10 peak maximum vibration acceleration frequency points a (f k ) and the maximum vibration displacement frequency d(f k ), k=1,2,...,10; f k Indicates the kth frequency corresponding to the peak vibration acceleration.

[0078] Step S4.2: Perform a modal analysis on the vibration acceleration of the affected transformer under the action of minimum stray current.

[0079] Step S4.21: Collect the vibration acceleration data A(t 0 );t0 Indicates the two-second period during which the mean absolute value of the stray current is minimum.

[0080] Step S4.22: A(t 0 ) is subjected to fast Fourier transform (FFT) to obtain A(t 0 )'s minimum vibration acceleration spectrum a 0 (f) and minimum vibration displacement spectrum d 0 (f);

[0081] d 0 (f) is expressed as:

[0082]

[0083] Step S4.23: Set the frequency range to [25Hz, 500Hz], and collect 10 frequency points a with the minimum peak vibration acceleration. 0 (f 0k ) and minimum vibration displacement frequency d 0 (f 0k ), k=1,2,...,10; f 0k Indicates a 0 The kth frequency corresponding to the peak vibration acceleration.

[0084] Step S4.3: Based on the modal analysis of steps S4.1 and S4.2, determine the abnormal vibration acceleration of the affected transformer; specifically, compare the frequency points of the abnormal vibration acceleration, using f k As the research object, compared with f k and f 0k (k=1,2,...,10), if f k and f 0k The frequencies are similar. Specifically, if the frequency difference is within 1Hz, they are considered to be the same frequency. 0k If the difference between all frequency points exceeds 1Hz, the frequency point is considered to be a new excitation frequency point, that is, abnormal vibration acceleration; all excitation frequency point information is output.

[0085] Step S4.4: Perform displacement modal comparison analysis on the abnormal vibration acceleration of the affected transformer.

[0086] Taking the displacement of the spectrum as the research object, the maximum vibration displacement frequency d of the same frequency is taken out k and minimum vibration displacement frequency d 0k (k=1,2,...,10), and calculate the displacement surge multiple X c :

[0087]

[0088] In the formula, c is the number of the same frequency point; m is the number of the same frequency points; a(f c ) represents the maximum vibration acceleration frequency; a 0 (f c ) represents the minimum vibration acceleration frequency; d(f c ) represents the maximum vibration displacement frequency; d 0 (f c ) represents the minimum vibration displacement frequency.

[0089] Output all displacement surge multiples and their corresponding frequency information.

[0090] Step S4.5: Based on the analysis in step S4.4, determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is triggered and the process goes to step S5. If not, it is considered that the abnormal vibration of the affected transformer induced by stray current intrusion is not strong, and a relevant conclusion is drawn, and the on-site monitoring of stray current and vibration acceleration is canceled.

[0091] Specifically, if the displacement surges by a factor of X c If the sum is greater than 10, an abnormal vibration alarm is issued;

[0092] Calculate the new excitation frequency information for the displacement surge multiple and obtain the new displacement surge multiple Y q :

[0093]

[0094]

[0095]

[0096] In the formula, q represents the frequency point number, f q represents the frequency of the qth frequency point, a(f q ) indicates the frequency is f q The maximum vibration acceleration, a 0 (f k ) indicates the frequency is f k The minimum vibration acceleration, d(f q ) indicates the frequency is f q Maximum vibration displacement; d 0max Represents the maximum displacement component of the minimum vibration acceleration spectrum.

[0097] If the new displacement surge multiple is greater than 1, an abnormal vibration alarm will be issued.

[0098] If an abnormal vibration alarm is issued, go to step S5, otherwise it is considered that the abnormal vibration of the affected transformer induced by the stray current intrusion is not strong, a relevant conclusion is given and the on-site monitoring of stray current and vibration acceleration is cancelled.

[0099] Step S5: Taking 50% of the extreme value of the upper envelope of the vibration acceleration as the reference value, take out the mean value of the stray current I when all vibration accelerations reach the reference value 50％ , Definition I 50％ is the stray current sensitivity threshold of the affected transformer. The on-site monitoring of stray current is retained, and the on-site monitoring of vibration acceleration is cancelled.

[0100] If the absolute value of the stray current measurement data is greater than the stray current sensitivity threshold, a real-time warning is issued that the stray current causes abnormal vibration acceleration of the affected transformer.

[0101] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating abnormal vibration of a transformer caused by stray current, characterized in that: The steps include: Step S1: synchronously monitor and record the stray current of the neutral point of the affected transformer and the vibration acceleration of the surface of the affected transformer box; Step S2: performing a peak-to-valley correlation analysis of the recorded stray current and vibration acceleration taking into account the time lag to obtain the maximum correlation coefficient and lag time of the stray current and vibration acceleration; Step S3: When the maximum correlation coefficient between stray current and vibration acceleration is greater than 0.75 and the lag time is less than 40ms, it is determined that the abnormal vibration of the affected transformer is caused by the stray current, and the process goes to step S4; otherwise, a relevant conclusion is given and the on-site monitoring of the stray current and vibration acceleration of the affected transformer is cancelled; Step S4: Perform modal analysis on the abnormal vibration of the affected transformer and determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is given and the process goes to step S5. If not, a relevant conclusion is given and the on-site monitoring of stray current and vibration acceleration is canceled. Step S5: Take 50% of the extreme value of the upper envelope of the vibration acceleration as the reference value, and take out the mean value of the stray current I when all vibration accelerations reach the reference value. 50％ , Definition I 50％ is the stray current sensitivity threshold of the affected transformer; retains on-site monitoring of stray current and releases on-site monitoring of vibration acceleration.

2. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 1, characterized in that: The specific process of step S2 is: Step S2.1: taking the absolute value of the stray current data with a resolution of 10sps and resampling it to 10ksps; Step S2.2: Take out the upper envelope A of the vibration acceleration A + and lower envelope A - ; Step S2.3: Set the data offset of the resampled stray current n=0; Step S2.4: Calculate the stray current I and the upper envelope A respectively + The correlation coefficient k + , stray current I and lower envelope A - The correlation coefficient k - ; Step S2.5: Update k + The maximum value and k - The minimum value of Step S2.6: When the data offset n<1000, go to step S2.7, otherwise go to step S2.8; Step S2.7: the data offset of the resampled stray current is n=n+1, the stray current I is offset by n sampling points, and the process goes to step S2.4; Step S2.8: Output k + The maximum value and corresponding offset n + and k - The minimum value and corresponding offset n - ,Finish.

3. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 2, characterized in that: The upper envelope lag time t of vibration acceleration A + =n + / 10ms, hysteresis time t of the lower envelope of vibration acceleration A - =n - / 10ms; the lag time between stray current and vibration acceleration is t + and t - The maximum correlation coefficient between stray current and vibration acceleration is 0.5 times k + The maximum value minus 0.5 times k - The maximum value of .

4. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 3, characterized in that: The specific process of step S4 is: Step S4.1: Perform modal analysis on the vibration acceleration of the affected transformer under the action of the maximum stray current; Step S4.2: Perform modal analysis on the vibration acceleration of the affected transformer under the action of minimum stray current; Step S4.3: determining the abnormal vibration acceleration of the affected transformer based on the modal analysis of steps S4.1 and S4.2; Step S4.4: performing displacement modal comparison analysis on the abnormal vibration acceleration of the affected transformer; Step S4.5: Based on the analysis in step S4.4, determine whether the abnormal vibration acceleration of the affected transformer is caused by stray current. If so, an alarm is triggered and the process goes to step S5. If not, it is considered that the abnormal vibration of the affected transformer induced by stray current intrusion is not strong, and a relevant conclusion is drawn, and the on-site monitoring of stray current and vibration acceleration is canceled.

5. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 4, characterized in that: The specific process of step S4.1 is: Step S4.11: Collect vibration acceleration data A(t p ), t p Indicates the time one second before and after the absolute peak moment of stray current; Step S4.12: A(t p ) is subjected to fast Fourier transform, and A(t p )’s maximum vibration acceleration spectrum a(f), maximum vibration displacement spectrum d(f); Step S4.13: Set the frequency range to [25Hz, 500Hz], and collect 10 frequency spectrum points a (f k ) and the maximum vibration displacement frequency d(f k ), k=1,2,...,10; f k represents the kth frequency corresponding to the peak vibration acceleration; d(f) is expressed as: Where f represents the frequency of the spectrum.

6. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 5, characterized in that: The specific process of step S4.2 is: Step S4.21: Collect vibration acceleration data A(t0) of the affected transformer in the minimum mean value of the absolute value of the stray current within a two-second time range; t0 represents the two-second time period in which the mean value of the absolute value of the stray current is the minimum; Step S4.22: Perform fast Fourier transform on A(t0) to obtain the minimum vibration acceleration spectrum a0(f) and the minimum vibration displacement spectrum d0(f) of A(t0); Step S4.23: Set the frequency range to [25Hz, 500Hz], and collect 10 frequency points a0 (f 0k ) and the minimum vibration displacement frequency d0(f 0k ), k=1,2,...,10; f 0k represents the kth frequency of the peak vibration acceleration corresponding to a0; d0(f) is expressed as:

7. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 6, characterized in that: The specific process of step S4.3 is: compare the frequency points of abnormal vibration acceleration, and change f k As the research object, compared with f k and f 0k , k=1,2,...,10, when f k and f 0k The frequency points are close to each other. Specifically, if the frequency difference is within 1Hz, they are considered to be the same frequency point. 0k If the difference between all frequency points exceeds 1Hz, the frequency point is considered to be a new excitation frequency point, that is, abnormal vibration acceleration; all excitation frequency point information is output.

8. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 7, characterized in that: The specific process of step S4.4 is: take the displacement of the spectrum as the research object, and extract the maximum vibration displacement frequency d of the same frequency k and minimum vibration displacement frequency d 0k , k = 1, 2, ..., 10, and calculate the displacement surge multiple X c : In the formula, c is the number of the same frequency point, m is the number of the same frequency points; a(f c ) represents the maximum vibration acceleration frequency; a0(f c ) represents the minimum vibration acceleration frequency; d(f c ) represents the maximum vibration displacement frequency; d0(f c ) represents the minimum vibration displacement frequency.

9. The method for evaluating abnormal vibration of a transformer caused by stray current according to claim 8, characterized in that: The specific process of step S4.5 is as follows: when the displacement surges by multiple X c If the sum is greater than 10, an abnormal vibration alarm is issued; calculate the new excitation frequency information for the displacement surge multiple, and obtain the new displacement surge multiple Y q : In the formula, q represents the frequency point number, f q represents the frequency of the qth frequency point, a(f q ) indicates the frequency is f q The maximum vibration acceleration, a0(f k ) indicates the frequency is f k The minimum vibration acceleration, d(fq) represents the maximum vibration displacement with frequency fq; d 0max Represents the maximum displacement component of the minimum vibration acceleration spectrum; When the new displacement surge multiple is greater than 1, an abnormal vibration alarm is issued; When an abnormal vibration alarm is issued, the process goes to step S5. Otherwise, it is considered that the abnormal vibration of the affected transformer induced by the stray current intrusion is not strong, and a relevant conclusion is given and the on-site monitoring of the stray current and vibration acceleration is cancelled.

10. The method for evaluating abnormal transformer vibration caused by stray current according to claim 9, characterized in that: In step S5, when the absolute value of the stray current measurement data is greater than the stray current sensitivity threshold, a real-time warning is issued that the stray current causes abnormal vibration acceleration of the affected transformer.

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