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

Abstract

The present invention relates to a method and device for grounding grid detection noise reduction based on the cross-correlation of pulsed eddy current electromagnetic and magnetic signals, and belongs to the field of non-destructive testing technology. The method simultaneously collects the horizontal electric field signal and the vertical magnetic field signal excited by the pulsed eddy current signal on the grounding grid through the receiving coil and the horizontal electric field sensor in the central loop structure. The pure noise signal is collected by turning off the excitation signal, and the power frequency noise is filtered out using the least squares fitting and Block Subtraction methods. Subsequently, the vertical voltage signal and the electric field signal are respectively converted into vertical magnetic field signals, and the optimal matching phase between the two is found through the snow melt optimizer, thereby achieving the removal of random noise. This method effectively improves the signal-to-noise ratio of pulsed eddy current data in substation detection, and is suitable for scenarios such as tower grounding body detection and urban detection.

Description

Technical Field

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

[0002] Currently, the pulsed eddy current method is widely used to measure parameters of substation grounding grids. However, substations contain numerous electromagnetic radiation sources, such as reactors, transformers, and communications equipment. These sources generate a large amount of electromagnetic interference signals, which seriously affect the quality and interpretation of pulsed eddy current grounding grid signals.

[0003] Existing noise reduction methods mainly include:

[0004] Noise modeling methods: Utilize 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 power frequency noise and has difficulty effectively dealing with random noise.

[0005] Estimation algorithms: These algorithms reliably extract effective pulsed eddy current secondary field signals from data sets in the presence of noise. However, this method can cause signal loss during later reconstruction, and the effectiveness of noise reduction relies on experimentation and experience in selecting the principal components for reconstruction. Furthermore, the algorithm is computationally intensive. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method and device for noise reduction of grounding grid detection based on the cross-correlation of pulsed eddy current electromagnetic and 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 for detecting 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 the cross-correlation of pulsed eddy current electromagnetic and magnetic signals comprises the following steps:

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

[0010] Step 2: Turn off the excitation signal and collect pure noise signals. The electric field and voltage pure noise of duration t1 are collected through the electric field sensor and the receiving coil respectively.

[0011] Step 3: Turn on the excitation signal and collect the noisy electromagnetic field signal of duration t2, and treat 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 time t1 by least squares fitting to obtain a purer power frequency noise sample;

[0013] Step 5: Apply the Block Subtraction method to subtract the noise signature domain determined by the locked phase from the noisy data measured at time t2, i.e., the pure noise signal at time t1, 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 the electric field signal and the magnetic field signal to achieve the optimal matching and then output 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 cycles of the pure noise fundamental frequency to ensure complete characteristic matching of the noisy signal. At the same time, for efficiency considerations, the duration of 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, 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 needs of 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 six, 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 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 a and n b , where n a =n b =n / 2;

[0028] Set the number of iterations and 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 the cross-correlation of pulsed eddy current electromagnetic and magnetic signals, comprising:

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

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

[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 collected for duration t1 through least squares fitting to obtain a purer power frequency noise sample;

[0034] The noise suppression module is used to 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 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 the electric field signal and the magnetic field signal to achieve the optimal matching and then output the noise reduction signal.

[0037] Furthermore, the receiving coil in the receiving module 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.

[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, and the accuracy and reliability of grounding grid detection are improved.

[0043] (2) This method is suitable for substation grounding network 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, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may 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 with reference to the accompanying drawings, in which:

[0048] Figure 1 This is a schematic diagram of the present invention;

[0049] Figure 2 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 of power frequency noise removal;

[0052] Figure 5 Flow chart of the method of the present invention;

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

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

[0055] The following describes the embodiments of the present invention by means of 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 are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

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

[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 there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional 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 the eddy current 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. It has strong periodicity and broadband characteristics. It primarily contaminates magnetic field signals across the entire time domain, causing severe 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 a great influence on the detection depth. Conventional methods such as wavelet noise reduction are not very effective.

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

[0066] When using a center loop device to perform pulsed eddy current electromagnetic field analysis on the substation grounding grid, the transmitting coil can be evenly divided into equal electric dipoles. Then the electromagnetic field excited by its small field source can be regarded as the superposition of the electromagnetic fields excited by 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 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, one is often more concerned with 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 is ≈ 1×10 6 =m), so a 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 zero, and the voltage amplitude measured by the receiving coil is only related to the change in 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 formula (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 The electric field is collected by the horizontal electric field sensor 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 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 first 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, for the sake of efficiency, it is not advisable to include too much pure noise data;

[0084] (2) The duration of t2 is approximately several times longer than that 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 few noisy data.

[0085] Secondly, the entire pure noise sample collected during time t1 is preprocessed using least squares fitting to obtain a purer power frequency noise sample. Since the collected power frequency noise signal does not emit sudden changes over a period of time, the pure noise signal during time t1 can be used to remove the power frequency noise during time t2.

[0086] Block Subtraction is a technique that removes global or background noise from local signals 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 applies Block Subtraction to remove power frequency noise. After completing the acquisition and processing of the pure noise signal of duration t1, Block Subtraction is applied to subtract the noise characteristic domain determined by the locked phase from the measured noisy data of duration t2, that is, the pure noise signal of duration t1, to achieve the suppression of power frequency noise. The flow chart is shown as follows: 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 signals have the same trend of change and amplitude. If there is any difference, it means that they are random noise signals. The correlation between the two signals can be extracted by formula (3). The random noise can be removed by extracting the most matching phase between the two signals. 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. According to the above-mentioned processed t2-length power frequency noise-removed signal, it is divided into n t2-length signals, that is, 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 .

[0091] When the error function reaches the set value or the number of iterations ends, the random noise is removed, that is, the optimal matching of 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, and 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 , it is the result of the five periodic signals before denoising. Figure 7 As shown in Figure 1, the result of a single periodic signal after denoising is shown.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. 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 solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all 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 electromagnetic and magnetic signals, characterized by: The following steps are involved: Step 1: The horizontal electric field sensor in the center loop structure collects the horizontal electric field signal and the vertical magnetic field signal through the receiving coil. At the same time, the horizontal electric field signal and the vertical magnetic field signal excited by the pulsed eddy current signal on the ground grid are collected. Step 2: Turn off the excitation signal and collect pure noise signals. The electric field and voltage pure noise of duration t1 are collected 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 treat the signals of the two time periods as a processing unit; Step 4: Preprocess the entire pure noise sample collected during time t1 by least squares fitting to obtain a purer power frequency noise sample; Step 5: Apply the Block Subtraction method to subtract the noise signature domain determined by the locked phase from the noisy data measured at time t2, i.e., the pure noise signal at time t1, 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 search for the most matching phase between the electric field signal and the magnetic field signal is achieved, and the noise reduction signal is outputted after the optimal matching is achieved; 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 cycles of the pure noise fundamental frequency to ensure complete characteristic matching of the noisy signal. At the same time, for efficiency considerations, the duration of 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 1 to 3 times that of t1 to ensure that the feature domain is considered to have no mutation within the duration of t2. At the same time, to take into account the detection efficiency, a certain length of noisy data is included to meet the needs of subsequent block subtraction.

2. The grounding grid detection noise reduction method based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 1 is characterized by: In step 6, 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.

3. The grounding grid detection noise reduction method based on pulsed eddy current electromagnetic-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 air, is a unit vector in the vertical direction.

4. The method for grounding grid detection noise reduction based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 1, characterized in that: 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 a and n b , where n a =n b =n / 2; Set the number of iterations and 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.

5. A grounding grid detection noise reduction device based on the cross-correlation of pulsed eddy current electromagnetic and magnetic signals, characterized by: include: The receiving module includes a receiving coil and a horizontal electric field sensor, which is used to simultaneously collect the horizontal electric field signal and the vertical magnetic field signal excited by the pulsed eddy current signal on the ground grid. The horizontal electric field sensor is used to collect the horizontal electric field signal, and the receiving coil is used to collect the vertical magnetic field signal. The noise acquisition module is used to turn off the excitation signal and collect pure noise signals, respectively collecting the electric field and voltage pure noise of duration t1 through the electric field sensor and the receiving coil; 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 collected for duration t1 through least squares fitting to obtain a purer power frequency noise sample; The noise suppression module is used to 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 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 electric field signal and the magnetic field signal to achieve the optimal matching and then output the noise reduction signal.

6. The grounding grid detection noise reduction device based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 5, characterized in that: The receiving coil in the receiving module uses high-temperature resistant nylon material as its 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.

7. The grounding grid detection noise reduction device based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 5, characterized in that: The signal processing module includes a least square fitting module and a Block Subtraction module.

8. The grounding grid detection noise reduction device based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 5, characterized in that: The noise reduction module includes a snowmelt optimizer.

9. The grounding grid detection noise reduction device based on pulsed eddy current electromagnetic-magnetic signal cross-correlation according to claim 5, 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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