Grounding grid detection noise reduction method and device based on pulsed eddy current electric-magnetic signal cross correlation

Abstract

The invention relates to a grounding grid detection noise reduction method and device based on pulsed eddy current electric-magnetic signal cross correlation, and belongs to the technical field of nondestructive detection. According to the method, through a receiving coil and a horizontal electric field sensor in a central loop structure, a horizontal electric field signal and a vertical magnetic field signal which are excited by a pulsed eddy current signal to a grounding grid are collected at the same time. A pure noise signal is acquired by closing an excitation signal, and power frequency noise is filtered by using least square fitting and a Block Subtraction method. And then, the vertical voltage signal and the electric field signal are converted into a vertical magnetic field signal, and an optimal matching phase between the vertical voltage signal and the electric field signal is searched through a snow melting optimizer, so that random noise removal is realized. The method effectively improves the signal-to-noise ratio of the pulsed eddy current data in transformer substation detection, and is suitable for the scenes of tower grounding body detection, city detection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing, and relates to a grounding grid detection noise reduction method and device based on the cross-correlation of pulsed eddy current electro-magnetic signals. Background Art

[0002] At present, the pulsed eddy current method is widely used in the measurement of substation grounding grid parameters. However, there are a large number of electromagnetic radiation sources in the substation, such as reactors, transformers, communication equipment, etc., which will generate a large number of electromagnetic interference signals, seriously affecting the quality and interpretation ability of the pulsed eddy current method to detect the grounding grid signal.

[0003] Existing noise reduction methods mainly include:

[0004] Noise modeling method: Use the correlation between noise samples or model the noise based on the correlation to reduce the noise of the noisy signal. However, this method is time-consuming to model the power frequency noise and it is difficult to effectively process random noise.

[0005] Estimation algorithm: Reliably extracts effective pulse eddy current secondary field signals from the data set in the presence of noise. However, this method will cause signal loss in the later reconstruction, and the noise reduction effect depends on the experience of experiments and the selection of the main components of the reconstruction, and the amount of calculation is large. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method and device for reducing noise in grounding grid detection based on the cross-correlation of pulsed eddy current electro-magnetic signals. The pulsed eddy current method can be used to measure the parameters of the substation grounding grid. However, during the measurement process, due to the presence of a large number of electromagnetic radiation sources in the substation, such as reactors, transformers, communication equipment, etc., they will generate a large number of electromagnetic interference signals, which will affect the quality and interpretation ability of the pulsed eddy current method to detect the grounding grid signal. Based on the cross-correlation between the vertical magnetic field and the horizontal electric field measured by the receiving coil in the center loop structure, the present invention designs a device for simultaneously collecting the horizontal electric field signal and the vertical magnetic field signal excited by the pulsed eddy current signal on the grounding grid, and designs a noise reduction method through the high correlation between the electric field signal and the magnetic field signal and the low correlation between the noise, thereby effectively improving the signal-to-noise ratio of the pulsed eddy current data in the substation detection.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A grounding grid detection noise reduction method based on pulse eddy current electro-magnetic signal cross-correlation includes the following steps:

[0009] Step 1: Through the receiving coil and horizontal electric field sensor in the central loop structure, the horizontal electric field signal and the vertical magnetic field signal excited by the pulse eddy current signal on the ground grid are collected simultaneously;

[0010] Step 2: Turn off the excitation signal, collect the pure noise signal, and collect the electric field and voltage pure noise of duration t1 through the electric field sensor and the receiving coil respectively;

[0011] Step 3: Turn on the excitation signal, collect the noisy electromagnetic field signal of duration t2, and use the signals of the two time periods as a processing unit, where the duration t2 is several times longer than the duration t1;

[0012] Step 4: Preprocess the entire pure noise sample collected during the t1 period by least squares fitting to obtain a purer power frequency noise sample;

[0013] Step 5: Apply the Block Subtraction method to subtract the noise characteristic domain determined by the locked phase from the noisy data of the measured time t2, that is, the pure noise signal of the time t1, so as to suppress the power frequency noise;

[0014] Step 6: Convert the vertical voltage signal into a vertical magnetic field signal B z1 , converting the electric field signal into a magnetic field signal B in the time domain z2 ;

[0015] Step 7: Use the exploration and balance mechanism in the snowmelt optimizer to achieve B z1 and B z2 The best matching phase is searched between them, and the optimal matching of electric field signal and magnetic field signal is achieved before outputting the noise reduction signal.

[0016] Furthermore, in step 2 and step 3, the durations t1 and t2 of collecting the noise signal and the noisy electromagnetic field signal meet the following conditions:

[0017] The duration of t1 must include three complete pure noise fundamental frequency cycles to ensure complete characteristics to match the noisy signal. At the same time, for efficiency consideration, the pure noise signal should not exceed three complete cycles. The period depends on the frequency of the transmitting excitation.

[0018] The duration of t2 is approximately several times longer than the duration of t1 to ensure that the feature domain is considered to have no mutation within the duration of t2. At the same time, in order to take into account the detection efficiency, a certain duration of noisy data is included, that is, the duration of t2 is 1 to 3 times the duration of t1 to meet the subsequent Block subtraction.

[0019] Furthermore, in step six, the vertical voltage signal is converted into a vertical magnetic field signal B z1 The formula is:

[0020]

[0021] Among them, N re is the number of turns of the receiving coil, S is the area of ​​the receiving coil, Vz is the received voltage.

[0022] Furthermore, in step 6, the electric field signal is converted into a magnetic field signal B in the time domain. z2 The formula is:

[0023]

[0024] Among them, B z2 =μH, where μ is the magnetic permeability; H is the magnetic field strength; k x and k y are the components of the wave number k generated by excitation in the air in the x and y directions, ω = 2πf is the angular frequency, f is the frequency of excitation; k = ω / v, v is the speed of light in the air, is a unit vector in the vertical direction.

[0025] Furthermore, in step 7, the exploration and balance mechanism in the snowmelt optimizer is used to achieve B z1 and B z2 The search for the best matching phase between , where:

[0026] The processed signal with the power frequency noise removed from the duration of t2 is divided into n signals with the duration of t2, that is, divided into n populations;

[0027] The number of populations used for local exploration and global exploration is n respectively. a and n b , where n a =n b =n / 2;

[0028] Set the number of iterations and the error function to iterate, where the error function is B z1 and B z2 The difference between

[0029] When the error function reaches the set value or the number of iterations is completed, the random noise is removed, that is, the optimal matching of the electric field signal and the magnetic field signal is completed.

[0030] A grounding grid detection noise reduction device based on pulse eddy current electric-magnetic signal cross-correlation, comprising:

[0031] A receiving module, used for simultaneously collecting horizontal electric field signals and vertical magnetic field signals excited by the pulsed eddy current signal on the ground grid, the receiving module comprising a receiving coil and a horizontal electric field sensor;

[0032] The noise collection module is used to turn off the excitation signal and collect the pure noise signal, and collect the electric field and voltage pure noise of duration t1 through the electric field sensor and the receiving coil respectively;

[0033] The signal processing module is used to start the excitation signal, collect the noisy electromagnetic field signal of duration t2, and pre-process the entire pure noise sample of duration t1 by least square fitting to obtain a purer power frequency noise sample;

[0034] A noise suppression module is used to apply a Block Subtraction method to subtract the noise characteristic domain determined by the locked phase from the noisy data of the measured time t2 to suppress the power frequency noise;

[0035] Signal conversion module, used to convert the vertical voltage signal into a vertical magnetic field signal B z1 , and convert the electric field signal into a magnetic field signal B in the time domain z2 ;

[0036] Denoising module, used to achieve B using the exploration and balance mechanism in the snowmelt optimizer z1 and B z2 The best matching phase is searched between them, and the optimal matching of electric field signal and magnetic field signal is achieved before outputting the noise reduction signal.

[0037] Furthermore, the receiving coil in the receiving module uses high temperature resistant nylon material as a skeleton, with a radius of 10 cm, an inductance of 10 mH, a capacitance of 250 pF, a resistance of 2.6 Ω, 300 turns, and a wire diameter of 0.05 mm.

[0038] Furthermore, the signal processing module includes a least squares fitting module and a Block Subtraction module.

[0039] Furthermore, the noise reduction module includes a snowmelt optimizer.

[0040] Furthermore, the signal conversion module includes a voltage signal to magnetic field signal conversion module and an electric field signal to magnetic field signal conversion module.

[0041] The beneficial effects of the present invention are:

[0042] (1) By simultaneously collecting horizontal electric field signals and vertical magnetic field signals and using the cross-correlation between the two to reduce noise, the signal-to-noise ratio of pulsed eddy current data in substation detection is effectively improved, thereby improving the accuracy and reliability of grounding grid detection.

[0043] (2) This method is suitable for substation grounding grid detection, and can be used in scenarios such as tower grounding detection and urban detection, and has good versatility.

[0044] (3) The power frequency noise is effectively filtered out through the least squares fitting and block subtraction methods, and the snowmelt optimizer is used to quickly find the optimal matching phase between the electric field signal and the magnetic field signal, thereby achieving effective removal of random noise.

[0045] (4) This method is simple to operate, easy to implement, and has a small amount of calculation, and can be quickly applied to practical engineering.

[0046] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0048] Figure 1 It is the principle diagram of the present invention;

[0049] Figure 2 It is a schematic diagram of the device of the present invention;

[0050] Figure 3 Schematic diagram of magnetic field and electric field measurement;

[0051] Figure 4 This is a schematic diagram for removing power frequency noise;

[0052] Figure 5 is a flow chart of the method of the present invention;

[0053] Figure 6 This is the result diagram of the first five cycles of denoising;

[0054] Figure 7 This is the result diagram of a single periodic signal after denoising. DETAILED DESCRIPTION

[0055] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0056] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0057] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0058] The present invention mainly uses the pulsed eddy current method to generate cross-correlation analysis between electric field and magnetic field signals to suppress noise. According to Faraday's law, the dynamic changes between the magnetic field signal and the electric field signal generated by eddy currents are highly correlated, and the noise signal that interferes with their waveforms is usually random, that is, these noise signals are usually independent except for the power frequency signal during the electric field and magnetic field measurement process. That is, the present invention uses the high correlation between the electric field and magnetic field signals and the low correlation between the noise as the core basis for cross-correlation noise reduction. The design idea is as follows Figure 1 shown.

[0059] When the horizontal electric field signal is measured by the electric field sensor, since the electric field sensor is a vector sensor, a vertical electric field signal may be measured simultaneously. However, the measured vertical electric field signal can be ignored for the following reasons.

[0060] (1) The measured electric field signal is mainly excited by the vertical magnetic field signal, so the measured vertical electric field signal is too small and can be almost ignored.

[0061] (2) The magnetic field signal obtained by converting the vertical electric field signal measured by the electric field sensor is independent of Bz1(t) calculated from the magnetic field H. The vertical electric field signal can be filtered out using formula (3).

[0062] The noise sources when collecting magnetic field signals through coils mainly include power frequency noise and random noise:

[0063] Power frequency noise: Power frequency noise is electromagnetic interference generated by electrical equipment in substations, with strong periodicity and broadband characteristics. Power frequency noise mainly pollutes the magnetic field signal in the full time domain, causing serious data distortion.

[0064] Random noise: Random noise is collected through the receiving coil by turning off the excitation signal. It is found that it mainly includes spike noise, Gaussian noise and system background noise. It has the characteristics of wide spectrum distribution, random energy changes, and great influence on the detection depth. Conventional methods such as wavelet noise reduction have poor effect.

[0065] The noise during electric field measurement also includes power frequency noise and random noise. The generation principle of power frequency noise is consistent with that of magnetic field, while random noise is mainly reflected in the non-stationarity of data caused by random noise or interference signals in local areas.

[0066] When using the center loop device to perform pulse eddy current electromagnetic field analysis on the substation grounding grid, the transmitting coil can be evenly divided into equal electric dipoles, so the electromagnetic field excited by its small field source can be regarded as the electromagnetic field superposition of countless horizontal electric dipoles. According to the calculation principle of induced electromotive force, the voltage measured by the receiving coil can be converted into a vertical magnetic field vertical magnetic field signal B z1 :

[0067]

[0068] Among them, N re is the number of turns of the receiving coil, S is the area of ​​the receiving coil, V z is the received voltage.

[0069] When testing the grounding grid of a substation, more attention is often paid to the magnetic field response induced by the electric dipole source, and the observation distance is generally much smaller than the free space wavelength (when the excitation is 25 Hz, the wavelength λ≈1×10 6 =100m), so the quasi-static approximation can be used. Therefore, only the electromagnetic field changes caused by the TE polarization mode need to be considered. When dealing with the TE polarization mode, the electric field in the vertical direction is 0, and the voltage amplitude measured by the receiving coil is only related to the change of the vertical magnetic field. According to Faraday's law:

[0070]

[0071] E x and E y are the current magnitudes on the x-axis and y-axis respectively; H z is the magnetic field strength in the vertical direction.

[0072] Since the device only collects data in the time domain, in order to solve the problem that the derivative of the electromagnetic field in space in equation (1) cannot be collected, the wave number k is introduced, and the spatial derivative is expressed in wave numbers, that is, The time derivative is expressed in terms of angular frequency, i.e. Formula (2) is transformed into:

[0073]

[0074] E x and E y It is collected by the electric field sensor in the horizontal direction of the device, k x and k y are the components of the wave number generated by the excitation in the x and y directions, ω = 2πf is the angular frequency, where f is the frequency of the excitation. B is obtained by formula (2) z After the frequency domain expression, it is converted into a time domain signal to obtain B z2 (t).

[0075] B calculated by the electric field E z2 (t) and B calculated from the magnetic field H z1 (t) cross-correlation function

[0076] R EH (τ) = ∫B z1 (t)B z2 (t+τ)dt (3)

[0077] Among them, R EH (τ) represents the cross-correlation function after the measured electric field and magnetic field signals are converted into perpendicular magnetic field strength, which is used for subsequent random noise removal; τ represents the time delay, which is used to calculate the correlation between the two signals at different time points, and is generally equal to the period of an excitation signal.

[0078] The receiving module probe designed by the present invention is as follows Figure 2 As shown, it includes a receiving coil and an orthogonal coupling electric field sensor. The coil uses high-temperature resistant nylon material as a skeleton, has a radius of 10 cm, an inductance of 10 mH, a capacitance of 250 pF, a resistance of 2.6 Ω, 300 turns, and a wire diameter of 0.05 mm.

[0079] During the measurement process, first, the noise conditions need to be continuously evaluated during the measurement because they change over time and the noise information may differ depending on the measurement location.

[0080] Magnetic field and electric field measurement schematic diagram Figure 3 The present invention firstly filters out the power frequency noise signal by using the least square fitting and Block Subtraction method.

[0081] First, turn off the excitation signal and collect the pure noise signal. The electric field and voltage pure noise of duration t1 are collected through the electric field sensor and the receiving coil respectively. After collecting the noise signal, turn on the excitation signal and collect the noisy electromagnetic field signal of duration t2. The signals of the two time periods are used as a processing unit.

[0082] The collection should follow the following principles:

[0083] (1) The duration t1 must contain three complete pure noise fundamental frequency cycles to ensure complete characteristics to match the noisy signal. At the same time, in order to take into account efficiency, it should not contain too much pure noise data;

[0084] (2) The duration of t2 is approximately several times longer than the duration of t1 to ensure that the feature domain can be considered to have no mutation within this duration. At the same time, in order to take into account the detection efficiency, it is not advisable to include too small a number of noisy data.

[0085] Secondly, the entire pure noise sample collected at time t1 is preprocessed by least square fitting to obtain a purer power frequency noise sample. Since the collected power frequency noise signal will not emit mutations within a period of time, the pure noise signal of time t1 can be used to remove the power frequency noise of time t2.

[0086] Block Subtraction is a technique that uses local signals to remove global or background noise by subtracting the average value, background value or other parameters from a specific area in the signal to remove the noise signal.

[0087] The present invention uses Block Subtraction to remove power frequency noise. After completing the acquisition and processing of the pure noise signal of duration t1, Block Subtraction is used to subtract the noise feature domain determined by the locked phase from the measured noisy data of duration t2, that is, the pure noise signal of duration t1, to suppress the power frequency noise. The flow chart is shown in FIG. Figure 4 shown.

[0088] After removing the power frequency noise signal, the voltage signals collected by the electric field sensor and the coil are converted into vertical magnetic field signals respectively, and then the random noise signal is filtered out in combination with the cross-correlation function.

[0089] After removing the power frequency noise, Convert the vertical voltage signal into a vertical magnetic field signal B z1 According to formula (2), the electric field signal is converted into a magnetic field signal B in the time domain z2 At this time, B z1 and B z2The two have the same change trend and amplitude. If there is a difference, it means that it is a random noise signal. The correlation between the two can be extracted by formula (3). The random noise can be removed by extracting the most matching phase between the two. However, since the sampling frequency of both the electric field sensor and the coil is too high, it is often greater than the sampling frequency of 1MHz. Therefore, the present invention introduces the snow ablation optimizer (SAO), which can achieve B by using the exploration and balance mechanism in SAO. z1 and B z2 Fast search for the best matching phase between.

[0090] The present invention uses formula (3) as the objective function of the snowmelt optimizer, and divides the signal with a duration of t2 after the above processing into n signals with a duration of t2, that is, n populations. The number of populations used for local exploration and global exploration is n respectively. a and n b , where n a =n b = n / 2. Set the number of iterations and the error function to iterate, where the error function is B z1 and B z2 The difference between .

[0091] When the error function reaches the set value or the number of iterations ends, the random noise is removed, that is, the optimal match between the electric field signal and the magnetic field signal is completed. The electromagnetic signal obtained at this time is the signal with the power frequency noise and random noise removed.

[0092] The process flow chart of the present invention is as follows Figure 5 shown.

[0093] Since the sampling rate of the receiver is quite high, generally 10M, the excitation frequency is set to 25Hz, that is, one cycle is 40ms, that is, 400,000 data collected in one cycle, so all calculations are done by computer. Figure 6 As shown in Figure 1, it is the result of five periodic signals before denoising. Figure 7 As shown in Figure 1, this is the result of a single periodic signal after denoising.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A grounding grid detection noise reduction method based on the cross-correlation of pulsed eddy current electro-magnetic signals, characterized in that: The following steps are involved: Step 1: Through the receiving coil and horizontal electric field sensor in the central loop structure, the horizontal electric field signal and the vertical magnetic field signal excited by the pulse eddy current signal on the ground grid are collected simultaneously; Step 2: Turn off the excitation signal, collect the pure noise signal, and collect the electric field and voltage pure noise of duration t1 through the electric field sensor and the receiving coil respectively; Step 3: Turn on the excitation signal, collect the noisy electromagnetic field signal of duration t2, and use the signals of the two time periods as a processing unit, where the duration t2 is several times longer than the duration t1; Step 4: Preprocess the entire pure noise sample collected during the t1 period by least squares fitting to obtain a purer power frequency noise sample; Step 5: Apply the Block Subtraction method to subtract the noise characteristic domain determined by the locked phase from the noisy data of the measured time t2, that is, the pure noise signal of the time t1, so as to suppress the power frequency noise; Step 6: Convert the vertical voltage signal into a vertical magnetic field signal B z1 , converting the electric field signal into a magnetic field signal B in the time domain z2 ; Step 7: Use the exploration and balance mechanism in the snowmelt optimizer to achieve B z1 and B z2 The best matching phase is searched between them, and the optimal matching of electric field signal and magnetic field signal is achieved before outputting the noise reduction signal.

2. The grounding grid detection noise reduction method based on pulse eddy current electro-magnetic signal cross-correlation according to claim 1 is characterized by: In step 2 and step 3, the durations t1 and t2 of collecting the noise signal and the noisy electromagnetic field signal meet the following conditions: The duration of t1 must include three complete pure noise fundamental frequency cycles to ensure complete characteristics to match the noisy signal. At the same time, for efficiency consideration, the pure noise signal should not exceed three complete cycles. The period depends on the frequency of the transmitting excitation. The duration of t2 is approximately several times longer than the duration of t1 to ensure that the feature domain is considered to have no mutation within the duration of t2. At the same time, in order to take into account the detection efficiency, a certain duration of noisy data is included, that is, the duration of t2 is 1 to 3 times the duration of t1 to meet the subsequent Block subtraction.

3. The grounding grid detection noise reduction method based on pulse eddy current electro-magnetic signal cross-correlation according to claim 1 is characterized by: In step six, the vertical voltage signal is converted into a vertical magnetic field signal B z1 The formula is: Among them, N re is the number of turns of the receiving coil, S is the area of ​​the receiving coil, V z is the received voltage.

4. The grounding grid detection noise reduction method based on pulse eddy current electro-magnetic signal cross-correlation according to claim 1 is characterized by: In step 6, the electric field signal is converted into a magnetic field signal B in the time domain. z2 The formula is: Among them, B z2 =μH, where μ is the magnetic permeability; H is the magnetic field strength; k x and k y are the components of the wave number k generated by excitation in the air in the x and y directions, ω = 2πf is the angular frequency, f is the frequency of excitation; k = ω / v, v is the speed of light in the air, is a unit vector in the vertical direction.

5. The grounding grid detection noise reduction method based on pulse eddy current electro-magnetic signal cross-correlation according to claim 1 is characterized by: In step 7, the exploration and balance mechanism in the snowmelt optimizer is used to achieve B z1 and B z2 The search for the best matching phase between , where: The processed signal with the power frequency noise removed from the duration of t2 is divided into n signals with the duration of t2, that is, divided into n populations; The number of populations used for local exploration and global exploration is n respectively. a and n b , where n a =n b =n / 2; Set the number of iterations and the error function to iterate, where the error function is B z1 and B z2 The difference between When the error function reaches the set value or the number of iterations is completed, the random noise is removed, that is, the optimal matching of the electric field signal and the magnetic field signal is completed.

6. A grounding grid detection noise reduction device based on the cross-correlation of pulsed eddy current electro-magnetic signals, characterized in that: include: A receiving module, used for simultaneously collecting horizontal electric field signals and vertical magnetic field signals excited by the pulsed eddy current signal on the ground grid, the receiving module comprising a receiving coil and a horizontal electric field sensor; The noise collection module is used to turn off the excitation signal and collect the pure noise signal, and collect the electric field and voltage pure noise of duration t1 through the electric field sensor and the receiving coil respectively; The signal processing module is used to start the excitation signal, collect the noisy electromagnetic field signal of duration t2, and pre-process the entire pure noise sample of duration t1 by least square fitting to obtain a purer power frequency noise sample; A noise suppression module is used to apply a BlockSubtraction method to subtract a noise characteristic domain determined by the locked phase from the noisy data of the measured time t2 to suppress the power frequency noise; Signal conversion module, used to convert the vertical voltage signal into a vertical magnetic field signal B z1 , and convert the electric field signal into a magnetic field signal B in the time domain z2 ; Denoising module, used to achieve B using the exploration and balance mechanism in the snowmelt optimizer z1 and B z2 The best matching phase is searched between the two, and the optimal matching of the electric field signal and the magnetic field signal is achieved before outputting the noise reduction signal.

7. The grounding grid detection noise reduction device based on pulse eddy current electro-magnetic signal cross-correlation according to claim 6 is characterized by: The receiving coil in the receiving module uses high temperature resistant nylon material as the skeleton, with a radius of 10 cm, an inductance of 10 mH, a capacitance of 250 pF, a resistance of 2.6 Ω, 300 turns, and a wire diameter of 0.05 mm.

8. The grounding grid detection noise reduction device based on pulse eddy current electro-magnetic signal cross-correlation according to claim 6 is characterized by: The signal processing module includes a least square fitting module and a Block Subtraction module.

9. The grounding grid detection noise reduction device based on pulse eddy current electro-magnetic signal cross-correlation according to claim 6, characterized in that: The noise reduction module includes a snow melt optimizer.

10. The grounding grid detection noise reduction device based on pulse eddy current electro-magnetic signal cross-correlation according to claim 6, characterized in that: The signal conversion module includes a voltage signal to magnetic field signal conversion module and an electric field signal to magnetic field signal conversion module.

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