Method for evaluating abnormal vibration of transformer caused by stray current

Abstract

The application discloses a kind of stray current causes the evaluation method of transformer abnormal vibration, including the following steps: the neutral point stray current waveform of affected transformer and the vibration acceleration of transformer box surface are monitored synchronously, second, the correlation analysis of stray current and vibration acceleration peak and valley is carried out, the maximum correlation coefficient and the hysteresis time of vibration acceleration to stray current are obtained, the correlation of transformer abnormal vibration and stray current invasion is judged, third, the modal analysis of abnormal vibration acceleration is carried out, realizes that stray current leads to abnormal vibration acceleration alarm, finally, the stray current sensitivity threshold of transformer vibration is deduced, and the real-time early warning of transformer abnormal vibration is carried out by stray current monitoring data;The application can realize transformer stray current abnormal vibration alarm, maintain transformer safe and reliable operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer detection, in particular to an evaluation method for abnormal vibration of a transformer caused by stray current. BACKGROUND

[0002] The subway stray current is a leakage current in the process of subway system operation. The intrusion of the subway stray current into the urban power grid can cause abnormal vibration of the transformer, which is specifically manifested as unstable "whistling" of the transformer caused by the changing stray current. The abnormal vibration of the transformer induces mechanical failure of the transformer body, such as loosening of the iron core, winding, clamp and bolt.

[0003] Once the transformer DC bias magnetization hazard is found in the operation of the urban power grid, it must be paid more attention. The field detection data shows that the stray current is a bipolar current with low frequency. How to determine the abnormal vibration of the transformer caused by the stray current is the primary problem, and how to realize the correlation analysis of the stray current and the vibration acceleration according to the detection data of the stray current and the vibration acceleration is the core problem. The mode of the transformer vibration acceleration is very complex, and how to further separate the abnormal vibration characteristics caused by the stray current is a big 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 the transformer vibration to exert the real-time warning advantage of the stray current online monitoring system. SUMMARY

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

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an evaluation method for abnormal vibration of a transformer caused by stray current, comprising the following steps:

[0006] Step S1: synchronously monitoring the stray current at the neutral point of the affected transformer and the vibration acceleration on the surface of the box body of the affected transformer, and recording;

[0007] Step S2: performing peak-valley value correlation analysis on the recorded stray current and vibration acceleration considering time lag, to obtain the maximum correlation coefficient and the lag time of the stray current and the vibration acceleration;

[0008] Step S3: when the maximum correlation coefficient of the stray current and the 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 step S4 is turned to, otherwise, relevant conclusions are given and the monitoring of the stray current and the vibration acceleration of the affected transformer in the field is released;

[0009] Step S4: modal analysis is performed on the abnormal vibration of the affected transformer, and it is determined whether the abnormal vibration acceleration of the affected transformer is caused by the stray current, if yes, an alarm is given, and the process goes to step S5, if not, a relevant conclusion is given and the monitoring of the stray current and vibration acceleration on site is cancelled;

[0010] Step S5: 50% of the envelope line extreme value of the vibration acceleration is taken as a reference value, the average value I 50％ of the stray current when all vibration accelerations reach the reference value is taken out, I 50％ is defined as the stray current sensitivity threshold of the affected transformer; the monitoring of the stray current on site is retained, and the monitoring of the vibration acceleration on site is cancelled.

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

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

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

[0014] Step S2.3: the data offset n of the resampled stray current is set to 0;

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

[0016] Step S2.5: the maximum value of k + and the minimum value of k - are updated;

[0017] Step S2.6: when the data offset n is less than 1000, the process goes to step S2.7, otherwise, the process goes to step S2.8;

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

[0019] Step S2.8: the maximum value of k + and the corresponding offset n + , and the minimum value of k - and the corresponding offset n - are output, and the process ends.

[0020] Further, the upper envelope line of the vibration acceleration A has a lag time t+ = n + / 10ms, the lower envelope of the vibration acceleration A lags time t - = n - / 10ms; the lag time of the stray current and the vibration acceleration is t + and the mean value of t - , the maximum correlation coefficient of the stray current and the vibration acceleration is 0.5 times k + , the maximum value of k - minus 0.5 times k

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

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

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

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

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

[0026] Step S4.5: based on the analysis in step S4.4, it is determined whether the abnormal vibration acceleration of the affected transformer is caused by the stray current, and if so, an alarm is given and the process proceeds to step S5, otherwise it is considered that the abnormal vibration of the affected transformer induced by the stray current invasion is not strong, and a relevant conclusion is given and the monitoring of the stray current and the vibration acceleration on site is cancelled.

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

[0028] Step S4.11: vibration acceleration data A(t p ) of the affected transformer is collected for one second before and after the absolute peak value of the stray current, t p representing the time one second before and after the absolute peak value of the stray current;

[0029] Step S4.12: fast Fourier transform is performed on A(t p ) to obtain the maximum vibration acceleration spectrum a(f) and the maximum vibration displacement spectrum d(f) of A(t p );

[0030] Step S4.13: assuming that the frequency range is [25Hz, 500Hz], the spectrum points a(f k) and maximum vibration displacement frequency point 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] In the formula, f represents the frequency of the frequency spectrum.

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

[0035] Step S4.21: Collect the vibration acceleration data A(t0) of the affected transformer in the range of the minimum mean value of the absolute value of the stray current for two seconds; t0 represents the two-second time period in which the mean value of the absolute value of the stray current is minimum;

[0036] 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);

[0037] Step S4.23: Set the frequency range to [25Hz, 500Hz], and collect the frequency points a0(f 0k ) and d0(f 0k ) of the 10 peak minimum vibration accelerations, k = 1, 2, …, 10; f 0k represents the kth frequency corresponding to the peak vibration acceleration a0;

[0038] d0(f) is expressed as:

[0039]

[0040] Further, the specific process of step S4.3 is as follows: Abnormal vibration acceleration frequency point comparison, taking f k as the research object, comparing f k and f 0k , k = 1, 2, …, 10, when f k and f 0k are similar frequency points, and the frequency difference is within 1Hz, it is considered to be the same frequency point, when a certain frequency point is different from all the frequency points of f 0k by more than 1Hz, it is considered to be a new excitation frequency point, i.e., abnormal vibration acceleration; output all the excitation frequency point information.

[0041] Further, the specific process of step S4.4 is as follows: Taking the displacement of the frequency spectrum as the research object, taking out the maximum vibration displacement frequency point d k and the minimum vibration displacement frequency point d0k , k = 1, 2,..., 10, and calculate the displacement surge multiplier X c :

[0042]

[0043] wherein c represents the same frequency point number, m represents the same frequency point number; a(f c ) represents the maximum vibration acceleration frequency point; a0(f c ) represents the minimum vibration acceleration frequency point; d(f c ) represents the maximum vibration displacement frequency point; d0(f c ) represents the minimum vibration displacement frequency point.

[0044] Further, the specific process of step S4.5 is: when the displacement surge multiplier X c is greater than 10, an abnormal vibration alarm is issued; new excitation frequency information is calculated for the displacement surge multiplier, and a new displacement surge multiplier Y q :

[0045]

[0046]

[0047]

[0048] wherein q represents the different frequency point number, f q represents the qth different frequency point frequency, a(f q ) represents the maximum vibration acceleration at the frequency f q , a0(f k ) represents the minimum vibration acceleration at the frequency f k , d(f q ) represents the maximum vibration displacement at the frequency f q ; d 0max represents the maximum displacement component of the minimum vibration acceleration frequency spectrum.

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

[0050] When the 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, and relevant conclusions are given and the stray current and vibration acceleration monitoring on site is cancelled.

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

[0052] Compared with the prior art, the present application has the following beneficial effects:

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

[0054] (2) The present application can clearly determine the causal relationship between dynamic stray current and abnormal vibration acceleration, deeply analyze the stray current vibration mode of transformer, and obtain the threshold of transformer vibration tolerance to stray current, so as to realize the alarm of transformer stray current abnormal vibration and maintain the safe and reliable operation of transformer. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0057] Step S1: Synchronously monitor the stray current of the affected transformer neutral point and the vibration acceleration of the affected transformer tank surface, and record.

[0058] The specific process of step S1 is: using stray current sensor and vibration acceleration sensor, continuously monitoring the stray current and vibration acceleration of the affected transformer neutral point and the middle part of the affected transformer tank surface 2m away from the ground for not less than 24 hours, and recording complete stray current I data and vibration acceleration A data, as shown in Figure 1 ; the time resolution of stray current I data is 10sps, and the time resolution of vibration acceleration A data is 10ksps.

[0059] Step S2: Perform peak-valley value correlation analysis on the stray current and vibration acceleration recorded in step S1 considering time lag, to obtain the 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 the upper envelope line A + and the lower envelope line A - of the vibration acceleration A.

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

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

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

[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: Let the data offset n of the resampled stray current be n = n + 1, and the stray current I be offset by n sampling points, and go to step S2.4.

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

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

[0069] Step S3: When the maximum correlation coefficient of the stray current and the vibration acceleration is greater than 0.75, and the lag time is less than 40 ms, it is determined that the abnormal vibration of the affected transformer is caused by the stray current, and go to step S4; otherwise, it is determined that the correlation between the abnormal vibration of the affected transformer and the stray current is not strong, and relevant conclusions are given and the monitoring of the stray current and the vibration acceleration of the affected transformer is released.

[0070] ​Step S4: modal analysis is performed on the abnormal vibration of the affected transformer, and it is determined whether the abnormal vibration acceleration of the affected transformer is caused by the stray current, if yes, an alarm is given, and the process goes to step S5, if not, it is considered that the abnormal vibration of the affected transformer caused by the stray current invasion is not strong, and a relevant conclusion is given and the monitoring of the stray current and the vibration acceleration on site is cancelled.

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

[0072] Step S4.11: vibration acceleration data A(t p ) of the affected transformer within one second before and after the absolute peak value of the stray current is collected, t p representing the time one second before and after the absolute peak value of the stray current.

[0073] Step S4.12: fast Fourier transform (FFT) is performed on A(t p ) to obtain the maximum vibration acceleration spectrum a(f) and the maximum vibration displacement spectrum d(f) of A(t p ).

[0074] d(f) is expressed as:

[0075]

[0076] In the formula, f represents the frequency of the spectrum.

[0077] Step S4.13: the frequency range is set as [25Hz, 500Hz], the frequency points a(f k ) of the maximum vibration acceleration of 10 peak values and the maximum vibration displacement frequency points d(f k ) are collected, k=1, 2,..., 10; f k representing the kth frequency corresponding to the peak vibration acceleration.

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

[0079] Step S4.21: vibration acceleration data A(t0) of the affected transformer within a two-second time range of the minimum average value of the absolute value of the stray current is collected; t0 represents the two-second time period of the minimum average value of the absolute value of the stray current.

[0080] Step S4.22: fast Fourier transform (FFT) is performed on A(t0) to obtain the minimum vibration acceleration spectrum a0(f) and the minimum vibration displacement spectrum d0(f) of A(t0).

[0081] d0(f) is expressed as:

[0082]

[0083] Step S4.23: Set the frequency range as [25Hz, 500Hz], collect the frequency points a0(f 0k ) and d0(f 0k ) of the 10 peak minimum vibration acceleration and minimum vibration displacement, k = 1, 2, …, 10; f 0k represents the kth frequency of the peak vibration acceleration corresponding to a0.

[0084] Step S4.3: Determine the abnormal vibration acceleration of the affected transformer based on the modal analysis of step S4.1 and step S4.2; specifically, the abnormal vibration acceleration frequency is compared, taking f k as the research object, comparing f k and f 0k (k = 1, 2, …, 10), if f k and f 0k are similar frequency points, specifically within 1Hz of the frequency difference, it is considered to be the same frequency point, if a certain frequency point is more than 1Hz different from all the frequency points of f 0k , it is considered to be a new excitation frequency, i.e. abnormal vibration acceleration; output all the excitation frequency information.

[0085] Step S4.4: Displacement modal contrast analysis of the abnormal vibration acceleration of the affected transformer.

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

[0087]

[0088] In the formula, c is the same frequency point number; m is the same frequency point number; a(f c ) represents the maximum vibration acceleration frequency point; a0(f c ) represents the minimum vibration acceleration frequency point; d(f c ) represents the maximum vibration displacement frequency point; d0(f c ) represents the minimum vibration displacement frequency point.

[0089] Output all the displacement surge multiples and their corresponding frequency point 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 the stray current. If yes, issue an alarm and go to step S5. If not, consider that the abnormal vibration of the affected transformer induced by the stray current intrusion is not strong, give the relevant conclusion and cancel the monitoring of the stray current and vibration acceleration on site.

[0091] Specifically, if the displacement surge multiple X c is greater than 10, an abnormal vibration alarm is issued.

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

[0093]

[0094]

[0095]

[0096] In the formula, q represents the number of the frequency point, f q represents the frequency of the qth frequency point, a(f q ) represents the maximum vibration acceleration at the frequency f q , a0(f k ) represents the minimum vibration acceleration at the frequency f k , d(f q ) represents the maximum vibration displacement at the frequency f q ; and 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 is issued.

[0098] If the abnormal vibration alarm is issued, go to step S5. Otherwise, consider that the abnormal vibration of the affected transformer induced by the stray current intrusion is not strong, give the relevant conclusion and cancel the monitoring of the stray current and vibration acceleration on site.

[0099] Step S5: Take the average value I 50％ of the stray current when all the vibration accelerations reach the reference value based on 50% of the extreme value of the envelope line of the vibration acceleration, and define I 50％ as the stray current sensitivity threshold of the affected transformer. Keep monitoring the stray current on site and release the monitoring of the vibration acceleration on site.

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

[0101] While embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating abnormal transformer vibration caused by stray current, characterized in that, Includes the following steps: Step S1: Simultaneously 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 tank; Step S2: Perform a peak-valley correlation analysis on the recorded stray current and vibration acceleration considering time lag to obtain the maximum correlation coefficient and lag time between stray current and vibration acceleration; Step S3: If 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 stray current, and proceed to step S4. Otherwise, give the relevant conclusion and stop the on-site monitoring of stray current and vibration acceleration of the affected transformer. 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 proceeds to step S5. If not, relevant conclusions are given and the monitoring of stray current and vibration acceleration at the site is canceled. Step S5: Using 50% of the extreme value of the upper envelope of vibration acceleration as the reference value, extract the average stray current I at the moment when all vibration accelerations reach the reference value. 50% Define I 50% Set the stray current sensitivity threshold for the affected transformer; retain on-site monitoring of stray current, and disable on-site monitoring of vibration acceleration; The specific process of step S2 is as follows: Step S2.1: Take the absolute value of the stray current data with a resolution of 10 sps and resample it to 10 ksps; Step S2.2: Extract the upper envelope A of the vibration acceleration A. + and lower envelope A - ; Step S2.3: Set the data offset n of the resampled stray current to 0; Step S2.4: Calculate the stray current I and the upper envelope A respectively. + correlation coefficient k + Stray current I and lower envelope A - correlation coefficient k - ; Step S2.5: Update k + The maximum value and k - The minimum value; Step S2.6: If the data offset n < 1000, proceed to step S2.7; otherwise, proceed to step S2.

8. Step S2.7: The data offset of the stray current after resampling is n=n+1, the stray current I is offset by n sampling points, and then proceed to step S2.4; Step S2.8: Output k + The maximum value and the corresponding offset n + and k - The minimum value and the corresponding offset n - ,Finish; The specific process of step S4 is as follows: 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: Determine the abnormal vibration acceleration of the affected transformer based on the modal analysis in steps S4.1 and S4.2; Step S4.4: Perform displacement mode 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 proceeds to step S5. If not, it is considered that the abnormal vibration of the affected transformer induced by stray current intrusion is not strong. A relevant conclusion is given and the monitoring of stray current and vibration acceleration at the site is cancelled. The specific process of step S4.1 is as follows: Step S4.11: Collect vibration acceleration data A(t) of the affected transformer for two seconds, one second before and after the absolute peak of the stray current. p ), t p This indicates the time one second before and after the absolute peak value of the stray current; Step S4.12: For A(t) p Perform a Fast Fourier Transform to obtain A(t) p The maximum vibration acceleration spectrum a(f) and the maximum vibration displacement spectrum d(f) of the vibration. Step S4.13: Assume the frequency band range is [25Hz, 500Hz], and collect 10 spectral points a(f) of the peak maximum vibration acceleration. k ) and the frequency point of maximum vibration displacement d(f k ), k=1,2,...,10; f k This represents the k-th frequency corresponding to the peak vibration acceleration; d(f) is represented as: ； In the formula, Frequency representing the spectrum; The specific process of step S4.2 is as follows: Step S4.21: Collect vibration acceleration data A(t0) of the affected transformer at the minimum mean value of stray current absolute value over a two-second time period; t0 represents the two-second time period at which the mean value of stray current absolute value is the minimum. Step S4.22: Perform a 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 band range to [25Hz, 500Hz], and collect 10 frequency points a0(f) of the minimum peak vibration acceleration. 0k ) and minimum vibration displacement frequency d0(f 0k ), k=1,2,...,10; f 0k This represents the k-th frequency of the peak vibration acceleration corresponding to a0; d0(f) is represented as: ； The specific process of step S4.3 is as follows: Compare the frequency points of abnormal vibration acceleration, and set f... k As the research subject, compared with f k and f 0k k=1,2,...,10, when f k and f 0k These are similar frequency points; specifically, frequencies differing by less than 1 Hz are considered the same frequency point. When a certain frequency point is similar to f... 0k If the frequency difference between all frequencies exceeds 1Hz, then the frequency is considered a new excitation frequency, i.e., abnormal vibration acceleration; output all excitation frequency information.

2. The method for evaluating abnormal transformer vibration caused by stray current according to claim 1, characterized in that: The upper envelope lag time t of vibration acceleration A + =n + / 10ms, the lower envelope hysteresis time t of vibration acceleration A - =n - / 10ms; the hysteresis time of stray current and vibration acceleration is t + and t - The mean value, 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 .

3. The method for evaluating abnormal transformer vibration caused by stray current according to claim 2, characterized in that: The specific process of step S4.4 is as follows: taking the displacement of the spectrum as the research object, the maximum vibration displacement frequency point d of the same frequency is extracted. k and the minimum vibration displacement frequency d 0k Given k=1,2,...,10, calculate the displacement surge factor X. c : ； In the formula, c is the number of the same frequency point, and m is the number of the same frequency points; Indicates the frequency of maximum vibration acceleration; Indicates the frequency of minimum vibration acceleration; Indicates the frequency of maximum vibration displacement; This indicates the frequency point of minimum vibration displacement.

4. The method for evaluating abnormal transformer vibration caused by stray current according to claim 3, characterized in that: The specific process of step S4.5 is as follows: when the displacement increases by a factor of X... c If the sum is greater than 10, an abnormal vibration alarm is triggered; new excitation frequency information is calculated for the displacement surge factor, resulting in a new displacement surge factor Y. q : ； ； ； In the formula, q represents the inter-frequency point number, and f q Let a(f) represent the frequency of the q-th different frequency point. q ) indicates a frequency of f q Maximum vibration acceleration, Indicates frequency as The minimum vibration acceleration, d(f) q ) indicates a frequency of f q The maximum vibration displacement; This represents the maximum displacement component of the minimum vibration acceleration spectrum; If the new displacement increases by a factor greater than 1, an abnormal vibration alarm will be issued; If an abnormal vibration alarm is issued, proceed to step S5; otherwise, 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 monitoring of stray current and vibration acceleration on site is cancelled.

5. The method for evaluating abnormal transformer vibration caused by stray current according to claim 4, 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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