Method for extracting current parameters of overhead three-phase power transmission line based on electromagnetic method detection data

Abstract

The invention provides a method for extracting current parameters of an overhead three-phase power transmission line based on electromagnetic method detection data, and relates to the field of geophysical exploration. A proper window function is selected, windowing processing is carried out on the electromagnetic method data, and windowing signals are obtained; fourier transform is carried out on the windowed signal, the frequency spectrum amplitude of the windowed signal is calculated, a frequency-amplitude function is obtained, detection and identification of fundamental waves and harmonic components in the windowed signal are achieved based on the function, and the total number of the fundamental waves and the harmonic components contained in the electromagnetic method data is determined; and determining frequencies, amplitudes and phases of fundamental waves and harmonic waves based on a double-spectral-line algorithm. According to the technical scheme, current harmonics actually existing in the overhead transmission line are fully considered, the extracted current parameters of the transmission line are closer to actual working conditions, and the authenticity and reliability of an extraction result are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geophysical exploration, and particularly relates to a method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic exploration data. BACKGROUND

[0002] In the field of geophysical exploration, electromagnetic radiation of transmission lines is usually regarded as a kind of noise, but can also be used as an effective signal source for characterizing geological features. Whether to eliminate or utilize this electromagnetic radiation, it is necessary to accurately obtain the frequency, amplitude and phase parameters of the current loaded in the transmission line. Although the traditional electrical measurement can directly obtain these parameters through a contact current sensor, such method not only has safety hazards, but also has complex operation complexity, which is difficult to meet the real-time monitoring demand of field geophysical exploration.

[0003] In the field of geophysics, some scholars have proposed to determine the current parameters by using optimization theory, but this method is only used to estimate the fundamental wave of single frequency of the transmission line current, without considering the current harmonics existing in the actual transmission line. SUMMARY

[0004] The purpose of the present application is to provide a method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic exploration data, and to provide technical support for using electromagnetic radiation of transmission lines to detect electrical structure of underground medium and to process electromagnetic data.

[0005] The above purpose of the present application is achieved by the following technical solutions: S1: collecting electromagnetic data of a high-voltage transmission line erection area; S2: selecting a suitable window function to perform windowing processing on the electromagnetic data to obtain a windowed signal; S3: performing Fourier transform on the windowed signal to calculate the frequency spectrum amplitude, obtaining a frequency-amplitude function, and based on the function, detecting and identifying the fundamental wave and harmonic components in the windowed signal to determine the total number of the fundamental wave and harmonic components contained in the electromagnetic data; S4: determining the frequency, amplitude and phase of the fundamental wave and the harmonic wave based on a bispectrum line algorithm.

[0006] Optionally, step S1 comprises: a plurality of measuring points are arranged on the same transmission line in the high-voltage transmission line erection area, and the electromagnetic data is obtained by multi-point measurement, and the spatial position information of the measuring points is recorded; The electromagnetic data includes: effective signal and interference signal; the interference signal includes: artificial interference source signal and natural interference source signal.

[0007] Optionally, step S2 comprises: the electromagnetic data is processed by a 4th-order self-convolution Nuttall window function The windowing process is implemented to obtain a windowed signal, as follows

[0008]

[0009] wherein is a 4th order self-convolution type Nuttall window function; is the windowed signal.

[0010] Optionally, step S3 comprises: S31: performing Fourier transform on the windowed signal to obtain a frequency-amplitude function; S32: identifying a peak value with a signal-to-noise ratio greater than a preset threshold in the frequency spectrum of the frequency-amplitude function, and determining the fundamental component by comparing the peak value intensity with the background noise level; S33: detecting other characteristic peak values in the frequency-amplitude function, and determining the harmonic components according to their frequency multiple relationship with the fundamental component; S34: determining the total number of the fundamental and harmonic components contained in the input signal by counting the number of the characteristic peak values from the fundamental component and the harmonic components.

[0011] Optionally, step S3 comprises: If the windowed signal contains only the fundamental component, a bispectrum line algorithm is used to calculate the frequency, amplitude and phase of the fundamental component; The frequency spectrum of the windowed signal is represented as:

[0012] wherein, represents the initial amplitude; represents the initial phase; represents N the 4th order derivative of the self-convolution window function, P the 3rd order derivative of the self-convolution window function, represents the self-convolution order; is the position corresponding to the peak in the frequency domain function, the positions of the local maximum spectrum line and the second largest spectrum line near the peak are the 1st and roots, and , and the amplitudes of the spectrum lines are and ; Let , , the correction formula of is:

[0013] the frequency , amplitude A, phase The fitting formula of the amplitude A and the phase is respectively

[0014]

[0015]

[0016] Wherein, f represents a sampling frequency; represents a principal value of an argument of a complex number; represents a function value of the windowed signal at a frequency of .

[0017] Optionally, the step S3 further comprises: After the fundamental wave parameter extraction is completed, a harmonic wave with a frequency closest to the fundamental wave is taken as a new fundamental wave, a bispectrum line algorithm is applied to solve the new fundamental wave frequency, amplitude and phase parameters, and multiple iteration calculations are performed until the frequency, amplitude and phase of all harmonic waves are obtained.

[0018] An electronic device comprises a processor, a memory, a user interface and a network interface, the memory is used to store instructions, the user interface and the network interface are used to communicate with other devices, and the processor is used to execute the instructions stored in the memory, so that the electronic device executes a method for extracting current parameters of an overhead three-phase transmission line based on electromagnetic detection data.

[0019] A computer readable storage medium stores instructions, when the instructions are executed, a method for extracting current parameters of an overhead three-phase transmission line based on electromagnetic detection data is executed.

[0020] The technical scheme provided by the application has the beneficial effects that: 1. When the windowing processing is implemented, a window function should be selected. The object processed by the application is a signal containing harmonic waves, and if a suitable window function is not used, it is difficult to accurately extract the harmonic wave parameters. The application uses a Nuttall window function processed by 4-order self-convolution, and the window function has excellent spectral characteristics.

[0021] 2. The application comprehensively considers the current harmonic waves actually existing in the transmission line, ensures that the bispectrum line algorithm can accurately extract the parameters of all harmonic waves, and obtains complete and reliable transmission line current parameter information. BRIEF DESCRIPTION OF DRAWINGS

[0022] The application will be further described below in combination with the drawings and embodiments, and in the drawings: Figure 1 is a step diagram in the embodiment of the application; ​Figure 2 is a double-spectrum line algorithm flowchart in the embodiment of the present application; Figure 3 is a simulation data diagram of electromagnetic method with power transmission line influence in the embodiment of the present application; Figure 4 is a frequency-amplitude function diagram in the embodiment of the present application; Figure 5 is a 50 Hz fundamental wave component diagram extracted from simulation data in the embodiment of the present application; Figure 6 is a harmonic component diagram extracted from simulation data in the embodiment of the present application; Figure 7 is a measured data diagram of wide-area electromagnetic method with power transmission line influence in the embodiment of the present application; Figure 8 is a frequency-amplitude function diagram in the embodiment of the present application; Figure 9 is a 50 Hz fundamental wave component diagram extracted from measured data in the embodiment of the present application; Figure 10 is a harmonic component diagram extracted from measured data in the embodiment of the present application; Figure 11 is an electronic device structure schematic diagram in the embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the drawings.

[0024] The embodiment of the present application provides a method for extracting current parameters of overhead three-phase power transmission lines based on electromagnetic method detection data.

[0025] Please refer to Figure 1 , Figure 1 is a step diagram of a method for extracting current parameters of overhead three-phase power transmission lines based on electromagnetic method detection data in the embodiment of the present application, comprising: S1: collecting electromagnetic method data of a high-voltage power transmission line erection area; S2: selecting a suitable window function to perform windowing processing on the electromagnetic method data to obtain a windowed signal; S3: performing Fourier transform on the windowed signal to calculate the spectral amplitude, obtaining a frequency-amplitude function, and based on the function, detecting and identifying the fundamental wave and harmonic components in the windowed signal to determine the total number of fundamental wave and harmonic components contained in the electromagnetic method data; S4: determining the frequency, amplitude and phase of the fundamental wave and the harmonic wave based on the double-spectrum line algorithm.

[0026] Step S1 comprises: Multiple measuring points are arranged on the same power transmission line in the high-voltage transmission line erection area, electromagnetic method data are obtained through multi-point measurement, and spatial position information of the measuring points is recorded. The electromagnetic method data include effective signals and interference signals, and the interference signals include artificial interference source signals and natural interference source signals.

[0027] As an embodiment, in the wide-area electromagnetic method field data acquisition, if there is a high-voltage transmission line and other human electromagnetic interference sources in the survey area, the following links need to be focused on. First, the wide-area electromagnetic method instrument is used to collect the measured signals, which are usually superimposed by electromagnetic method effective signals and interference signals. Second, through the analysis of the time domain characteristics of the measured signals, the interference phenomena such as periodic fluctuation and sudden jump distortion are identified, and the differences in amplitude, period and other characteristics between artificial interference sources and natural interference sources are compared, so as to distinguish different interference sources and evaluate their influence degree. Finally, combined with the distribution of the power transmission lines around the survey area, the determination basis of the high-voltage transmission line as the main interference source is determined.

[0028] As an embodiment, when the data acquisition is carried out, the shape and spatial position parameters of the power transmission line need to be mastered. The main parameters of the overhead three-phase power transmission line include the structure form, the loop number, the height from the ground and the horizontal distance between the lines. Among them, the structure form and the loop number can be determined by visual observation, and the height from the ground and the horizontal distance are recommended to be accurately measured by using a total station. In order to improve the measurement accuracy, multiple measuring points are arranged along the same power transmission line, and more accurate spatial position information is obtained through multi-point measurement.

[0029] Step S2 includes: As an embodiment, the Fourier transform extracts the fundamental wave and harmonic wave parameters of alternating current through discrete spectrum analysis, and its application needs to meet two basic conditions: the sampling period should be an integer multiple of the signal period, and the sampling frequency must be higher than twice the highest frequency of the signal. In the case of considering harmonics, the sampling period and the harmonic period are not integer multiples, and the sampling frequency may be less than the high-frequency harmonic frequency, causing harmonic detection and fundamental wave parameter distortion. The introduction of window function can effectively solve such problems.

[0030] As an embodiment, the classical window function can be divided into two categories: cosine type and non-cosine type. The cosine type window has the characteristics of wide main lobe but fast side lobe decay, which is suitable for accurate calculation of signal amplitude; the non-cosine type window has the characteristics of narrow main lobe and slow side lobe decay, which is more conducive to distinguishing signal components with similar frequencies. Due to the structural differences between the two types of window functions, each has its own advantages in spectrum analysis. By implementing self-convolution operation on the window function, the performance of the main lobe and the side lobe can be improved, thereby improving the comprehensive performance of the window function in frequency resolution and amplitude extraction.

[0031] Through the 4th order self-convolution type Nuttall window function, the electromagnetic method data The windowing process is implemented to obtain a windowed signal, as follows

[0032]

[0033] wherein is a 4th order self-convolution type Nuttall window function; is a windowed signal.

[0034] As an embodiment, the input signal (electromagnetic data) is truncated by a window function to form a short-time signal of finite length, which provides a suitable condition for subsequent Fourier transform. The gradual truncation characteristics of the window function can effectively suppress harmonic leakage and spectral aliasing in the processing of harmonic signals, thereby significantly improving the reliability of signal analysis.

[0035] Step S3 comprises: S31: performing Fourier transform on the windowed signal to obtain a frequency-amplitude function; S32: identifying a peak value with a signal-to-noise ratio greater than a preset threshold in the frequency spectrum of the frequency-amplitude function, and determining the fundamental component by comparing the peak value intensity with the background noise level; S33: detecting other characteristic peaks in the frequency-amplitude function, and determining the harmonic components according to their frequency multiple relationship with the fundamental wave; S34: determining the total number of fundamental and harmonic components contained in the input signal by counting the number of characteristic peaks of the fundamental and harmonic components.

[0036] Step S3 comprises: If the windowed signal contains only the fundamental wave, a two-line spectrum algorithm is used to calculate the frequency, amplitude and phase of the fundamental wave; The frequency spectrum of the windowed signal is represented as:

[0037] wherein represents the initial amplitude; represents the initial phase; represents N the 4th order derivative of the self-convolution window function, P the 4th order derivative, represents the self-convolution order; is the position corresponding to the peak in the frequency domain function, the positions of the local maximum spectrum line and the second largest spectrum line near the peak are the 1st and roots, and , and the amplitudes of the spectrum lines are and ; Set , , determine correction formula is:

[0038] frequency , amplitude A, phase fitting formula is

[0039]

[0040]

[0041] wherein indicates the sampling frequency; indicates the principal value of the argument of the complex number; indicates the function value of the windowed signal at the frequency .

[0042] Step S3 also includes: After completing the fundamental parameter extraction, the harmonic with the frequency closest to the fundamental is taken as the new fundamental, the bispectrum line algorithm is applied to solve the new fundamental frequency, amplitude and phase parameters, and multiple iterations are calculated until the frequency, amplitude and phase of all harmonics are obtained.

[0043] As an embodiment, the complete process of the bispectrum line algorithm is shown in Figure 2 .

[0044] The present application provides an embodiment as follows, step 1: Figure 3 The electromagnetic method data dominated by the electromagnetic radiation signal of the transmission line is obtained by numerical simulation. The field source adopts a coplanar arrangement of three-phase circuit, and the heights of the three-phase transmission lines are 14 m, 15 m and 16 m respectively. The measuring point is located on the ground 60 m away from the transmission line in the horizontal direction. The current components loaded in the line are shown in Table 1. Influenced by the harmonic components, Figure 4 the signal waveform in

[0045] Table 1 Main parameters of current fundamental and harmonic

[0046] Step 2: truncate the input signal based on the window function to generate a short-time signal with limited length.

[0047] Step 3: convert the short-time signal into a complex frequency domain signal based on Fourier transform, calculate the complex modulus and construct a frequency-amplitude function curve (as shown in Figure 4(As shown). Figure 4 The display shows a peak with the largest amplitude at 50 Hz, which corresponds to the fundamental frequency component. Simultaneously, eight smaller peaks were detected, all with center frequencies that are odd multiples of the fundamental frequency, consistent with harmonic characteristics. Therefore, it can be determined that the input signal contains nine frequency components generated by the transmission line, including one fundamental frequency and eight harmonics.

[0048] Step 4: Use the dual-spectral-line algorithm to determine the fundamental frequency, simultaneously estimate the fundamental amplitude and phase, and plot the time-domain signal waveform of the fundamental frequency as shown below. Figure 5 As shown in the figure, no waveform distortion was observed in the result, verifying the superiority of the self-convolution Nuttall window in waveform preservation and demonstrating the advanced nature of the window function selected in this invention.

[0049] Based on the fundamental frequency, harmonic analysis is performed within the odd harmonic range to determine the frequency, amplitude, and phase parameters of each harmonic component in turn. Figure 6 The time-domain waveforms of the extracted harmonics are shown, with the frequency values ​​marked in each sub-figure being rounded calculation results. These results verify the effectiveness of this invention in estimating multi-order, cross-frequency band harmonic parameters, demonstrating its excellent high-frequency harmonic extraction capability.

[0050] This application provides an embodiment as follows: Step 1: Figure 7 This section presents field measurement data using the wide-area electromagnetic method. The signal channel exhibits typical nonlinearity and non-stationarity due to superimposed interference such as periodic fluctuations and abrupt distortions. Compared to the natural background electromagnetic field signal, this type of interference signal shows significant differences in amplitude intensity, energy distribution, and periodic regularity. This noise originates from complex human activities in the survey area, with electromagnetic radiation from high-voltage transmission lines being the dominant interference.

[0051] Step 2: Truncate the input signal based on the window function to generate a short-time signal with a finite length.

[0052] Step 3: Perform Fourier transform processing on the windowed signal to obtain the frequency-amplitude function, such as... Figure 8 As shown. Figure 8 A significant spike appeared near the 50 Hz frequency point, with its intensity significantly higher than the background noise benchmark, confirming it as an effective characterization of the power frequency fundamental frequency. Simultaneously, nine peaks were detected at... The left and right spikes represent harmonics, and their center frequencies follow a distribution pattern of odd multiples of the fundamental frequency. Therefore, it can be concluded that the input signal contains ten signal components caused by the transmission line, of which one is the fundamental frequency and nine are harmonics.

[0053] Step 4: The fundamental frequency is located by the modulus function highest peak, the fundamental frequency is calculated as 50.86 Hz according to the bispectrum line algorithm, and the amplitude and phase of the component are estimated, and the time domain signal waveform is drawn as shown in Figure 9 The nine odd harmonic components from the third to the nineteenth are determined by combining the preset threshold value. Figure 10 The waveforms of the respective harmonic components are shown, and the frequency values of the subplots are the calculation results truncated to the unit place. The experiment realizes high-precision identification and effective separation of the power fundamental wave and its harmonic components in a complex outdoor environment, which embodies the engineering applicability of the present application.

[0054] The present application also discloses an electronic device. Referring to Figure 11 , Figure 11 is a structural schematic diagram of an electronic device disclosed by the present application embodiment. The electronic device 500 can include at least one processor 501, at least one network interface 504, a user interface 503, a memory 505, and at least one communication bus 502.

[0055] The communication bus 502 is used to realize the connection and communication between the components.

[0056] The user interface 503 can include a display screen, and the optional user interface 503 can further include a standard wired interface and a wireless interface.

[0057] The network interface 504 can optionally include a standard wired interface and a wireless interface (such as a WI-FI interface).

[0058] The present application also discloses a computer readable storage medium, which stores a plurality of instructions, and the instructions are suitable for being loaded by a processor to execute the above-mentioned method for extracting current parameters of an overhead three-phase power transmission line based on electromagnetic method detection data.

[0059] The above are only exemplary embodiments of the present disclosure, and cannot limit the scope of the present disclosure. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure are still within the scope of the present disclosure.

[0060] The present application is intended to cover any variations, uses, or adaptive changes of the present disclosure that follow the general principles of the present disclosure and include common knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and examples are only considered as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A method for extracting current parameters of an overhead three-phase transmission line based on electromagnetic method exploration data, characterized in that, The method comprises the following steps: S1: collecting electromagnetic data of a high-voltage transmission line erection area; S2: selecting a suitable window function to perform windowing processing on the electromagnetic data to obtain a windowed signal; S3: performing Fourier transform on the windowed signal to calculate the frequency spectrum amplitude to obtain a frequency-amplitude function, and based on the function, detecting and identifying the fundamental wave and harmonic components in the windowed signal to determine the total number of the fundamental wave and harmonic components contained in the electromagnetic data; S4: determining the frequency, amplitude and phase of the fundamental wave and harmonic based on a bispectrum line algorithm.

2. A method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic method exploration data according to claim 1, characterized in that, Step S1 comprises: Multiple measuring points are arranged on the same transmission line in the high-voltage transmission line erection area, and electromagnetic data is obtained through multi-point measurement, and the spatial position information of the measuring points is recorded; The electromagnetic data includes: effective signal and interference signal; the interference signal includes: artificial interference source signal and natural interference source signal.

3. The method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic method detection data according to claim 1, characterized in that, Step S2 comprises: Through the 4th order self-convolution type Nuttall window function, the electromagnetic method data The windowing processing is implemented to obtain a windowed signal, as follows wherein is a 4th order self-convolution type Nuttall window function; is a windowed signal.

4. The method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic method detection data according to claim 1, characterized in that, Step S3 comprises: S31: performing Fourier transform on the windowed signal to obtain a frequency-amplitude function; S32: identifying the peak value with a signal-to-noise ratio greater than a preset threshold in the frequency spectrum of the frequency-amplitude function, and determining the fundamental wave component by comparing the peak value intensity and the background noise level; S33: detecting other characteristic peaks in the frequency-amplitude function, and determining the harmonic component according to the frequency multiple relationship with the fundamental wave; S34: determining the total number of the fundamental wave and harmonic components contained in the input signal by counting the number of characteristic peaks of the fundamental wave component and the harmonic component.

5. The method for extracting current parameters of overhead three-phase transmission lines based on electromagnetic method detection data according to claim 1, characterized in that, Step S3 comprises: If the windowed signal only contains the fundamental wave, use the bispectrum line algorithm to calculate the frequency, amplitude and phase of the fundamental wave; The frequency spectrum of the windowed signal is represented as: wherein denotes the initial amplitude; denotes the initial phase; denotes N the P derivative of order denotes the convolution order; is the position of the peak in the frequency domain function, the positions of the local maximum and the second maximum spectral line in the vicinity of and the roots, and , and the amplitudes of the spectral lines are and ; Let , , determine the correction formula for: Frequency , amplitude A, phase of the fitting formulae are wherein denotes the sampling frequency; denotes the principal value of the argument of a complex number; denotes the function value of the windowed signal at frequency ωn.

6. A method for extracting current parameters of an overhead three-phase transmission line based on electromagnetic method exploration data according to claim 5, characterized in that, Step S3 further comprises: After the fundamental wave parameter extraction is completed, the harmonic with the frequency closest to the fundamental wave is taken as a new fundamental wave, The bispectrum line algorithm is applied to solve the frequency, amplitude and phase parameters of the new fundamental wave, and multiple iterations are calculated until the frequency, amplitude and phase of all harmonics are obtained.

7. An electronic device, comprising: The electronic device comprises a processor, a memory, a user interface and a network interface, the memory is used to store instructions, the user interface and the network interface are used to communicate with other devices, and the processor is used to execute the instructions stored in the memory to enable the electronic device to perform the method of any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions, and when the instructions are executed by a computer, the method of any one of claims 1-6 is performed.

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