Transformer active protection method and system under reclosing short circuit impact

Abstract

The invention discloses a transformer active protection method and system under reclosing short circuit impact, and relates to the field of signal monitoring, and the method comprises the steps: determining a phase generating short circuit current according to three-phase current sampling signals in different time periods; determining an effective vibration channel according to the corresponding vibration sampling signal generating the short-circuit current; extracting a steady-state vibration signal and a transient-state vibration signal at the occurrence moment of the short-circuit current from the vibration sampling signal of the effective vibration channel, and further calculating a frequency intensity ratio mean value of the effective vibration channel; and determining an operation mode of reclosing active protection according to the current effective value at the occurrence moment of the short-circuit current and the frequency intensity ratio mean value of the effective vibration channel. According to the invention, the reclosing operation is comprehensively judged through the current effective value at the occurrence moment of the short-circuit current impact and the frequency intensity ratio mean value of the effective vibration channel, the accuracy of the reclosing operation is improved, and the active protection of the transformer is realized.

Description

Technical Field

[0001] The present application relates to the field of signal monitoring, and in particular to a method and system for active protection of a transformer under a short-circuit impact of a reclosing switch. Background Art

[0002] Power transformers are one of the key and expensive equipment in the power grid. They undertake important tasks such as power transmission and voltage conversion, and are closely related to the safe and stable operation of the power grid. Once a power transformer fails, it is very likely to cause large-scale power rationing or power outages in the power grid, causing unnecessary economic losses and adverse social impacts.

[0003] The automatic reclosing device widely used in the power system can automatically reclose the circuit breaker after the circuit breaker trips. However, the accuracy of the automatic reclosing device is low, and misoperation often occurs, resulting in structural damage to the transformer, inability to achieve active protection of the transformer, and low transformer reliability. Summary of the invention

[0004] The purpose of the present application is to provide a method and system for active protection of a transformer under a short-circuit impact of a reclosing switch, which can improve the accuracy of the reclosing operation and achieve active protection of the transformer.

[0005] To achieve the above objectives, this application provides the following solutions.

[0006] In the first aspect, the present application provides a method for active protection of a transformer under a short-circuit impact of a reclosing switch, comprising: obtaining a three-phase current sampling signal and a three-phase vibration sampling signal of the transformer; dividing the three-phase current sampling signal and the three-phase vibration sampling signal according to the power frequency cycle to obtain the three-phase current sampling signal and the three-phase vibration sampling signal of different time periods; calculating the effective values ​​of the three-phase current sampling signal and the three-phase vibration sampling signal of different time periods; determining the phase generating the short-circuit current according to the effective values ​​of the three-phase current sampling signals of different time periods; finding the corresponding vibration sampling signals of different time periods generating the short-circuit current in the three-phase vibration sampling signals of different time periods, and determining the effective vibration channel according to the effective values ​​of the vibration sampling signals of different time periods generating the short-circuit current; determining the steady-state vibration signal and the transient vibration signal in the vibration sampling signal of the effective vibration channel; calculating the frequency intensity ratio mean of the effective vibration channel according to the steady-state vibration signal and the transient vibration signal in the effective vibration channel; determining the operation mode of the active protection of the reclosing switch according to the effective value of the current at the moment when the short-circuit current occurs and the frequency intensity ratio mean of the effective vibration channel.

[0007] In the second aspect, the present application provides a transformer active protection system under a short-circuit impact of a reclosing switch, comprising: a storage unit, a power supply unit, three current transformers, 3p vibration acceleration sensors, a communication unit, a multi-channel dynamic signal acquisition unit and an analysis and display terminal; the current transformer is arranged on each phase of the three-phase electricity in the rheological box of the transformer, and the vibration acceleration sensor is arranged on the box wall of each corresponding transformer on the low-voltage side of the transformer, and each phase is provided with one current transformer and p vibration acceleration sensors; the current transformer is used to obtain the three-phase current sampling signal of the transformer; the vibration acceleration sensor is used to obtain the three-phase vibration sampling signal of the transformer; the input end of the multi-channel dynamic signal acquisition unit is respectively connected to the output end of the storage unit, the power supply unit, the three current transformers and the 3p vibration acceleration sensors, and the output end of the multi-channel dynamic signal acquisition unit is connected to the analysis and display terminal through the communication unit; the analysis and display terminal is used to apply the above-described method to determine the operation mode of the active protection of the reclosing switch.

[0008] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0009] The present application determines the phase generating short-circuit current in the transformer through three-phase current sampling signals, determines the effective vibration channel based on the vibration sampling signal of the phase, and calculates the frequency intensity ratio mean, and then determines the operation mode of active protection of the reclosing switch according to the current value at the time when the short-circuit current occurs and the frequency intensity ratio mean of the effective vibration channel, so as to facilitate timely detection of abnormal state of transformer winding after being hit by a short-circuit shock, and provides a scientific active protection method, thereby improving the accuracy of the transformer reclosing action, realizing active protection of the transformer, and improving the operating reliability of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 A flow chart of a method for active transformer protection under a closing short-circuit shock provided in an embodiment of the present application.

[0012] Figure 2 A time domain waveform diagram of a current sampling signal for generating a short-circuit current provided in an embodiment of the present application.

[0013] Figure 3This is a time domain waveform diagram of a vibration sampling signal of a phase generating a short-circuit current provided in an embodiment of the present application.

[0014] Figure 4 A schematic structural diagram of a transformer active protection system under a closing short-circuit impact provided in an embodiment of the present application. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0016] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0017] Among all the fault types of power transformers, the deformation of windings caused by the short-circuit current at the outlet is the most harmful fault. At this time, the short-circuit electric force acting on the transformer winding surges, posing a great threat to the mechanical stability of the transformer winding. At the same time, the deformation of the transformer winding has a cumulative effect, that is, after a single short-circuit shock, the winding may be slightly deformed, but it can still operate. Such a transformer running with a defect may be directly damaged when it is subjected to the next short-circuit shock, with serious consequences. Operation experience shows that transformer damage tripping caused by line reclosing short-circuit shocks or even multiple reclosing shocks often occurs. Among the faults of the power system, the faults of overhead lines are mostly instantaneous, such as line contact caused by strong winds, surface flashover of insulators caused by lightning strikes, etc. After the short-circuit fault is removed by the relay protection action, the arc will automatically extinguish, and in most cases the insulation at the short-circuit can be automatically restored. Therefore, the automatic reclosing device is widely used in the power system. However, if the transformer winding has structural damage or cumulative damage after the short-circuit impact, it may cause transformer failure during the reclosing operation, endangering the safe operation of the power grid. The existing reclosing protection strategy is to monitor the voltage, current and time, and perform the reclosing operation when the conditions such as the transformer current is lower than a certain threshold, the voltage is stable, or there is no re-fault in a short time are met. The mechanical stability of the transformer winding after the short-circuit impact is not considered, that is, if the transformer winding has insufficient short-circuit resistance, it is very likely that the main transformer will be damaged during the reclosing. With the rapid development of new power systems under the background of dual carbon, the increase in transformer capacity, and the increase in the number of lines and equipment, the number of short-circuit faults and short-circuit currents have also increased. The environment in which the transformer bears the short-circuit impact of the reclosing is more severe, and the damage rate of the main transformer has also increased accordingly. How to ensure the safe and reliable operation of the transformer has become an urgent problem to be solved in the industry. The prior art only realizes automatic reclosing by monitoring voltage, current and time, etc., without considering the mechanical stability of the transformer winding after being subjected to a short-circuit shock. That is, if the transformer winding has insufficient short-circuit resistance, a main transformer damage accident is very likely to occur during reclosing.

[0018] Embodiment 1, as Figure 1 As shown, this embodiment provides a method for actively protecting a transformer under a short-circuit impact of a reclosing switch, specifically comprising:

[0019] Step S1. Acquire three-phase current sampling signals and three-phase vibration sampling signals of the transformer.

[0020] Optionally, the transformer in step S1 is a transformer in operation.

[0021] In actual application, this application monitors a 110kV transformer, and obtains the three-phase current signal and three-phase vibration signal of the transformer through a current transformer and six vibration acceleration sensors placed on the wall of the transformer box.

[0022] Step S2: Divide the three-phase current sampling signals and the three-phase vibration sampling signals according to the power frequency cycle to obtain the three-phase current sampling signals and the three-phase vibration sampling signals in different time periods.

[0023] Optionally, the power frequency period is 20ms.

[0024] Step S3. Calculate the effective values ​​of the three-phase current sampling signals and the three-phase vibration sampling signals in different time periods, specifically including:

[0025] Furthermore, the calculation formula of the effective value of the three-phase current sampling signal in different time periods is as follows:

[0026]

[0027] In the formula, represents the effective value of the current sampling signal of the jth phase in the mth time period, j = 1, 2, 3, L is the number of sampling points, i jm (k) is the current value of the kth sampling point in the mth time period of the jth phase.

[0028] Optional, f k =10.24kHz; L=204.

[0029] Furthermore, the calculation formula of the effective value of the three-phase vibration sampling signal in different time periods is as follows:

[0030]

[0031] In the formula, represents the effective value of the vibration sampling signal of the pth vibration channel of the jth phase in the mth time period, j = 1, 2, 3, L is the number of sampling points, v jpm (k) is the vibration amplitude of the kth sampling point in the mth time period of the pth vibration channel of the jth phase.

[0032] Step S4. Determine the phase generating the short-circuit current according to the effective values ​​of the three-phase current sampling signals in different time periods, specifically including:

[0033] The phase whose effective value of the current sampling signal in three consecutive time periods is greater than the phase current lockout reclosing setting is selected as the phase generating the short-circuit current.

[0034] Step S5. Find the vibration sampling signals of different time periods corresponding to the short-circuit current in the three-phase vibration sampling signals of different time periods, and determine the effective vibration channel according to the effective values ​​of the vibration sampling signals of different time periods corresponding to the short-circuit current.

[0035] The effective vibration channel is determined according to the effective value of the vibration sampling signal in different time periods corresponding to the short-circuit current, specifically including:

[0036] Among the vibration sampling signals in different time periods corresponding to the generation of short-circuit current, the vibration channels whose effective values ​​of the vibration sampling signals in at least two time periods in three consecutive time periods are greater than the first vibration threshold ε2 are marked as effective vibration channels.

[0037] In actual application, Figure 2 As shown in the figure, the basis for selecting the effective vibration channel when the transformer has a short-circuit current (short-circuit fault) is: when the effective value of the current sampling signal of any phase of the transformer is greater than the phase current blocking reclosing setting ε1 in the a time period, the a+1 time period and the a+2 time period, it is judged that a short-circuit fault has occurred. Figure 3 As shown, if the effective value of the vibration sampling signal of the pth vibration channel is greater than the set vibration over-limit threshold ε2 in at least two sections of the ath section, the a+1th section and the a+2th section, it is marked as a valid vibration channel, and the number of valid vibration channels is q.

[0038] Optionally, here, the phase current lockout reclosing constant ε1=7423A; the vibration over-limit threshold ε2=1.5g; and the number of effective vibration channels q=2.

[0039] Step S6: Determine a steady-state vibration signal and a transient vibration signal in the vibration sampling signal of the effective vibration channel.

[0040] The steady-state vibration signal is 0.05f long before the short-circuit current occurs. k The length of the transient vibration signal after the short-circuit current occurs is 0.1f k The vibration sampling signal of k is the sampling frequency of the vibration signal.

[0041] Step S7. Calculate the frequency intensity ratio mean of the effective vibration channel according to the steady-state vibration signal and the transient vibration signal in the effective vibration channel, specifically including:

[0042] S71. Perform local spectrum refinement and amplification on the steady-state vibration signal and the transient vibration signal in the effective vibration channel through Zoom-FFT transformation to obtain the spectrum distribution of the transformed steady-state vibration signal and the transient vibration signal of the effective vibration channel.

[0043] Step S71 specifically includes:

[0044] S711. respectively for the steady-state vibration signal v sw and transient vibration signal v tw Perform complex modulation to obtain a steady-state vibration signal v sw and transient vibration signal v tw The frequency-shifted steady-state vibration signal v′ sw and frequency-shifted transient vibration signal v′ tw , the calculation formula is:

[0045]

[0046]

[0047] Where: f se and f te are the complex modulation center frequencies of the steady-state vibration signal and the transient vibration signal respectively; n1=0, 1, 2, ..., N1-1, N1 is the steady-state vibration signal v sw length; n2 = 0, 1, 2, ..., N2-1, N2 is the transient vibration signal v tw The length of se =100Hz, f te =100Hz.

[0048] S712. respectively calculate the steady-state vibration signal v sw and transient vibration signal v tw , and its frequency shift signal v′ sw and v′ tw Perform discrete Fourier transform, the calculation formula is:

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] In the formula, and They are steady-state vibration signal, transient vibration signal, and frequency-shifted steady-state vibration signal v′ sw and frequency-shifted transient vibration signal v′ tw The discrete spectrum of The spectrum Fsw and F′ sw The discrete frequency points of The spectrum F tw and F′ tw The discrete frequency points of L 01 With L 02 They are and The displacement of F sw L 01 Discrete frequency points and F tw L 02 The discrete frequency points are moved to F′ sw and F′ tw The zero point of .

[0056] S713. Design a digital low-pass filter to calculate the discrete spectrum F′ of the frequency-shifted steady-state vibration signal and the frequency-shifted transient vibration signal sw and F′ tw The output after low-pass filtering and The corresponding calculation formula is:

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] Where H1 and H2 are the transfer functions of the digital low-pass filter, N c1 is the spectral line number corresponding to the cutoff frequency of H1, N c2 is the spectral line number corresponding to the cutoff frequency of H2, and D is the refinement analysis multiple. Here, D=3.

[0064] S714. and Perform an inverse discrete Fourier transform to obtain its time domain output y sw (n1) and y tw (n2), the calculation formula is:

[0065]

[0066]

[0067] In the formula, y sw (n1), y tw (n2) respectively F′ sw and F′ tw Time domain output after filtering.

[0068] S715. Use new sampling frequency f′ k For y sw With y tw Resample to obtain the steady-state resampled vibration signal y′ sw (m1) and the transient resampled signal y′ tw (m2) is used to improve the spectrum resolution, and the calculation formula is:

[0069] y′ sw (m1) = y sw (m1D) m1=0,1,2,L,M1-1;

[0070] y′ tw (m2) = y tw (m2D) m2=0,1,2,L,M2-1;

[0071] f′ k =f k / D;

[0072] Where M1 is y′ sw The signal length of M2 is the signal y′ tw signal length.

[0073] S716. Respectively resample the steady-state signal y′ sw and the transient resampled signal y′ tw Perform discrete Fourier transform to obtain the refined vibration signal spectrum, and the calculation formula is:

[0074]

[0075]

[0076] Where, Y′ sw (ψ1), Y′ tw (ψ2) are the steady-state resampled signals y′ sw and the transient resampled signal y′ tw Discrete spectrum of sw Discrete frequency points, ψ1=0,1,2,L,M1-1; ψ2 is the spectrum Y′ tw The discrete frequency points are ψ2=0,1,2,L,M2-1.

[0077] S717. Adjust Y′ sw and Y′ tw The position of the discrete frequency point in the image is used to obtain the steady-state vibration signal v sw With the transient vibration signal v tw The spectrum distribution of is calculated as:

[0078]

[0079]

[0080] In the formula, ZF sw (ω1), ZF tw (ω2) are the steady-state vibration signals v sw With the transient vibration signal v tw Zoom-FFT transformation result; ω1 is the spectrum ZF sw Discrete frequency point, ω1=L 01 -M1 / 2,L 01 -M1 / 2+1,L,L 01 +M1 / 2-1; ω2 is the spectrum ZF tw Discrete frequency points, ω2=L 02 -M2 / 2,L 02 -M2 / 2+1,L,L 02 +M2 / 2-1.

[0081] S72. Calculate the frequency intensity ratio mean of the effective vibration channel according to the spectrum distribution of the transformed steady-state vibration signal and transient vibration signal of the effective vibration channel.

[0082] The calculation formula of the frequency intensity ratio mean of the effective vibration channel is as follows:

[0083]

[0084]

[0085] In the formula, is the frequency intensity ratio mean of the effective vibration channel, K w is the frequency intensity ratio of the wth effective vibration channel, q is the number of effective vibration channels, M1 is the number of frequency points of the refined spectrum obtained after the steady-state vibration signal is transformed by Zoom-FFT, M2 is the number of frequency points of the refined spectrum obtained after the transient vibration signal is transformed by Zoom-FFT, ZF sw (ω1) is the spectrum amplitude at the ω1th frequency point in the refined spectrum obtained after the steady-state vibration signal of the wth effective vibration channel is transformed by Zoom-FFT, ZF tw(ω2) is the spectrum amplitude at the ω2th frequency point in the refined spectrum obtained after the transient vibration signal of the wth effective vibration channel is transformed by Zoom-FFT.

[0086] Step S8. Determine the operation mode of active reclosing protection according to the effective current value at the time when the short-circuit current occurs and the frequency intensity ratio average of the effective vibration channel, specifically including:

[0087] When the effective value of the current at the moment when the short-circuit current occurs is less than the phase current lockout reclosing setting ε1, and the frequency intensity ratio mean of the effective vibration channel is less than the vibration first locking setting ε3, the reclosing is performed immediately.

[0088] When the effective value of the current at the moment when the short-circuit current occurs is less than the phase current lockout reclosing setting ε1, and the first vibration lockout setting ε3 is less than the frequency intensity ratio mean of the effective vibration channel and less than the second vibration lockout setting ε4, delayed reclosing is executed; ε4=λ·ε3.

[0089] When the effective value of the current at the moment when the short-circuit current occurs is greater than the phase current lockout reclosing setting ε1, or when the effective value of the current at the moment when the short-circuit current occurs is less than the phase current lockout reclosing setting ε1 and the frequency intensity ratio mean of the effective vibration channel is greater than the vibration second lockout setting ε4, reclosing will not be performed.

[0090] Optionally, the delay time for executing delayed reclosing is 1 second, λ=1.1.

[0091] In actual application, the effective current value and the frequency intensity ratio average of the effective vibration channel at the time of short-circuit current impact are 7635A and 15.1524 respectively, and the reclosing is locked.

[0092] Embodiment 2, as Figure 4 As shown, the present application also provides a transformer active protection system under reclosing short-circuit impact, and the transformer active protection method system under reclosing short-circuit impact includes: a storage unit, a power supply unit, 3 current transformers, 3p vibration acceleration sensors, a communication unit, a multi-channel dynamic signal acquisition unit and an analysis and display terminal.

[0093] The current transformer is arranged on each phase of the three-phase electricity in the rheological box of the transformer, and the vibration acceleration sensor is arranged on the box wall of each corresponding transformer on the low-voltage side of the transformer. Each phase is provided with one current transformer and p vibration acceleration sensors; the current transformer is used to obtain the three-phase current sampling signal of the transformer; the vibration acceleration sensor is used to obtain the three-phase vibration sampling signal of the transformer.

[0094] The input end of the multi-channel dynamic signal acquisition unit is respectively connected to the output ends of the storage unit, the power supply unit, three current transformers and 3p vibration acceleration sensors, and the output end of the multi-channel dynamic signal acquisition unit is connected to the analysis display terminal through the communication unit; the analysis display terminal is used to determine the operation mode of the active protection of the reclosing switch using the above method.

[0095] The present application determines the phase generating the short-circuit current in the transformer through the three-phase current sampling signal, determines the effective vibration channel based on the vibration sampling signal of the phase, and calculates the frequency intensity ratio mean, and then determines the operation mode of the active protection of the reclosing switch according to the current value at the time of the short-circuit current and the frequency intensity ratio mean of the effective vibration channel, so as to facilitate timely discovery of the abnormal state of the transformer winding after being subjected to the short-circuit impact, and provides a scientific active protection method, thereby improving the accuracy of the transformer reclosing action, realizing active protection of the transformer, and improving the operation reliability of the transformer. Specifically, the present application selects the effective vibration channel of the transformer under the external short-circuit fault, calculates the spectrum distribution of the transformer vibration signal based on the Zoom-FFT transformation, and determines the active protection method of the transformer under the short-circuit impact of the reclosing switch by combining the effective value of the transformer short-circuit current and the frequency intensity ratio mean of the vibration signal of the effective vibration channel. The judgment method is efficient, accurate, and easy to implement, which facilitates timely discovery of the abnormal state of the transformer winding after being subjected to the short-circuit impact, and provides a scientific active protection method to improve the operation reliability of the transformer.

[0096] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for active transformer protection under short-circuit impact of reclosing, characterized in that: The active transformer protection method under reclosing short-circuit impact includes: Obtaining three-phase current sampling signals and three-phase vibration sampling signals of the transformer; The three-phase current sampling signal and the three-phase vibration sampling signal are divided according to the power frequency cycle to obtain the three-phase current sampling signal and the three-phase vibration sampling signal in different time periods; Calculate the effective values ​​of three-phase current sampling signals and three-phase vibration sampling signals in different time periods; Determine the phase generating the short-circuit current according to the effective values ​​of the three-phase current sampling signals in different time periods; Finding vibration sampling signals of different time periods corresponding to the generation of short-circuit current in the three-phase vibration sampling signals of different time periods, and determining effective vibration channels according to effective values ​​of the vibration sampling signals of different time periods corresponding to the generation of short-circuit current; Determine a steady-state vibration signal and a transient vibration signal from the vibration sampling signal of the effective vibration channel; Calculate the frequency intensity ratio mean value of the effective vibration channel according to the steady-state vibration signal and the transient vibration signal in the effective vibration channel; The operation mode of the active protection of the reclosing switch is determined based on the effective current value at the time when the short-circuit current occurs and the average frequency intensity ratio of the effective vibration channel.

2. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: According to the current value at the time of short-circuit current occurrence and the average value of the frequency intensity ratio of the effective vibration channel, the operation mode of the active protection of the reclosing switch is determined, including: When the effective value of the current at the time of short-circuit current occurrence is less than the phase current blocking reclosing setting ε1, and the frequency intensity ratio average of the effective vibration channel is less than the vibration first blocking setting ε3, reclosing is performed immediately; When the effective value of the current at the time of short-circuit current occurrence is less than the phase current blocking reclosing setting ε1, and the first vibration blocking setting ε3 is less than the frequency intensity ratio mean of the effective vibration channel and less than the second vibration blocking setting ε4, the delayed reclosing is executed; ε4 = λ·ε3; When the effective value of the current at the moment when the short-circuit current occurs is greater than the phase current lockout reclosing setting ε1, or when the effective value of the current at the moment when the short-circuit current occurs is less than the phase current lockout reclosing setting ε1 and the frequency intensity ratio mean of the effective vibration channel is greater than the vibration second lockout setting ε4, reclosing will not be performed.

3. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: The phase generating the short-circuit current is determined according to the effective values ​​of the three-phase current sampling signals in different time periods, specifically including: The phase whose effective value of the current sampling signal in three consecutive time periods is greater than the phase current lockout reclosing setting is selected as the phase generating the short-circuit current.

4. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: The calculation formula of the effective value of the three-phase current sampling signal in different time periods is as follows: In the formula, represents the effective value of the current sampling signal of the jth phase in the mth time period, j = 1, 2, 3, L is the number of sampling points, i jm (k) is the current value of the kth sampling point in the mth time period of the jth phase.

5. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: Determining an effective vibration channel according to the effective values ​​of the vibration sampling signals in different time periods corresponding to the generation of the short-circuit current specifically includes: Among the vibration sampling signals in different time periods corresponding to the generation of short-circuit current, the vibration channels whose effective values ​​of the vibration sampling signals in at least two time periods in three consecutive time periods are greater than the first vibration threshold ε2 are marked as effective vibration channels.

6. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: The calculation formula of the effective value of the three-phase vibration sampling signal in different time periods is as follows: In the formula, represents the effective value of the vibration sampling signal of the pth vibration channel of the jth phase in the mth time period, j = 1, 2, 3, L is the number of sampling points, v jpm (k) is the vibration amplitude of the kth sampling point in the mth time period of the pth vibration channel of the jth phase.

7. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: The steady-state vibration signal is 0.05f long before the short-circuit current occurs. k The length of the transient vibration signal after the short-circuit current occurs is 0.1f k The vibration sampling signal of k is the sampling frequency of the vibration signal.

8. The active transformer protection method under reclosing short-circuit impact according to claim 1 is characterized in that: The frequency intensity ratio mean value of the effective vibration channel is calculated based on the steady-state vibration signal and transient vibration signal in the effective vibration channel, specifically including: The spectrum of the steady-state vibration signal and the transient vibration signal in the effective vibration channel is locally refined and amplified by Zoom-FFT transformation to obtain the spectrum distribution of the transformed steady-state vibration signal and the transient vibration signal of the effective vibration channel; According to the spectrum distribution of the transformed steady-state vibration signal and transient vibration signal of the effective vibration channel, the frequency intensity ratio mean value of the effective vibration channel is calculated.

9. The active transformer protection method under reclosing short-circuit impact according to claim 8 is characterized in that: The calculation formula of the frequency intensity ratio mean of the effective vibration channel is as follows: In the formula, is the frequency intensity ratio mean of the effective vibration channel, K w is the frequency intensity ratio of the wth effective vibration channel, q is the number of effective vibration channels, M1 is the number of frequency points of the refined spectrum obtained after the steady-state vibration signal is transformed by Zoom-FFT, M2 is the number of frequency points of the refined spectrum obtained after the transient vibration signal is transformed by Zoom-FFT, ZF sw (ω1) is the spectrum amplitude at the ω1th frequency point in the refined spectrum obtained after the steady-state vibration signal of the wth effective vibration channel is transformed by Zoom-FFT, ZF tw (ω2) is the spectrum amplitude at the ω2th frequency point in the refined spectrum obtained after the transient vibration signal of the wth effective vibration channel is transformed by Zoom-FFT.

10. An active transformer protection system under reclosing short-circuit impact, characterized in that: The active transformer protection method system under reclosing short-circuit impact includes: a storage unit, a power supply unit, three current transformers, 3p vibration acceleration sensors, a communication unit, a multi-channel dynamic signal acquisition unit and an analysis and display terminal; The current transformer is arranged on each phase of the three-phase electricity in the rheological box of the transformer, and the vibration acceleration sensor is arranged on the box wall of each corresponding transformer on the low-voltage side of the transformer, and each phase is provided with one current transformer and p vibration acceleration sensors; the current transformer is used to obtain the three-phase current sampling signal of the transformer; the vibration acceleration sensor is used to obtain the three-phase vibration sampling signal of the transformer; The input end of the multi-channel dynamic signal acquisition unit is respectively connected to the output ends of the storage unit, the power supply unit, the three current transformers and the 3p vibration acceleration sensors, and the output end of the multi-channel dynamic signal acquisition unit is connected to the analysis display terminal through the communication unit; the analysis display terminal is used to apply the method described in any one of claims 1 to 9 to determine the operation mode of the active protection of the reclosing switch.

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