Target object electromagnetic radiation disturbance test method and system

Abstract

The application provides a target object electromagnetic radiation interference test method and system, and relates to the technical field of electromagnetic radiation identification. Firstly, voltage signals are injected into each grounding selection circuit at equal time intervals, voltage distortion rates are obtained by analyzing the response voltage signals through sliding time window Fourier transform, target objects with distortion rates exceeding the limit are marked, and current time domain signals thereof are collected. Secondly, the current signals are analyzed for harmonic distortion through fast Fourier transform in the same sliding time window, high-frequency sharp pulse amplitudes and time domain segments are extracted through high-pass filtering and sliding window peak detection. Then, background noise is preset, voltage and current distortion starting times are calibrated, and time difference values are calculated. Finally, when the time difference values are in the preset threshold interval, the high-frequency sharp pulse time domain segments are analyzed through fast Fourier transform, continuous frequency intervals are divided, main frequency intervals are determined, energy proportion and frequency domain characteristic parameters are verified, and electromagnetic radiation interference is determined when the conditions are met.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic radiation identification technology, specifically to a method and system for testing electromagnetic radiation interference from a target object. Background Technology

[0002] The ground fault location circuit is the core component of a power system to achieve accurate fault location. In complex electromagnetic environments, this circuit is susceptible to external electromagnetic radiation interference. If such interference cannot be accurately identified, it can easily lead to malfunction of the ground fault location device.

[0003] Under normal operating conditions, the device collects key electrical quantities such as zero-sequence voltage, zero-sequence current, and phase difference of current in each loop. Through a preset line selection algorithm, it determines whether there is a ground fault and the faulty loop, ensuring the accuracy of line selection. However, if it is affected by electromagnetic radiation sources, non-fault voltage anomalies may occur. For example, after the high-frequency spike pulse generated by the radiation source is coupled to the ground fault selection loop, it will cause the loop voltage waveform distortion. This distortion is not caused by the loop itself, such as insulation damage or ground short circuit, but by the instantaneous effect of external electromagnetic radiation interference. The non-fault distortion caused by electromagnetic radiation is misjudged as a ground fault, causing the line selection device to frequently malfunction, affecting the normal operation of the power grid. After the ground fault selection device malfunctions, when the maintenance personnel arrive at the scene, the radiation source has often stopped operating and the electromagnetic environment has returned to normal. At this time, it is difficult to capture the key features such as high-frequency spike pulses and voltage distortion when the interference occurs.

[0004] Therefore, there is an urgent need for an electromagnetic radiation interference testing technology that can distinguish non-fault electromagnetic interference based on the specific electrical characteristics induced in the grounding line selection circuit by external electromagnetic radiation interference, thereby reducing the impact of line selection device malfunctions on the power grid.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for testing electromagnetic radiation interference of a target object, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The electromagnetic radiation interference test method for the target object includes the following specific steps:

[0009] Voltage signals are injected into each grounding selection circuit in the power system at equal time intervals. The voltage distortion rate is obtained by analyzing the response signal through Fourier transform within a sliding time window. Grounding selection circuits with voltage distortion rates greater than the preset standard limit are marked as target objects, and their current time domain signals are collected.

[0010] The acquired current time-domain signal is subjected to fast Fourier transform to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, it is determined whether there is harmonic distortion. High-pass filtering and sliding window peak detection algorithm are used to obtain high-frequency spike pulse amplitude segments from the current time-domain signal.

[0011] With a preset background noise, when there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of current distortion, and the start time of the time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of voltage distortion. The time difference is calculated based on the start times of current distortion and voltage distortion.

[0012] When the time difference is within the preset time threshold range, the time domain signal corresponding to the high-frequency spike pulse amplitude segment is analyzed for high-frequency energy distribution characteristics. The continuous frequency range with the highest energy proportion is taken as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

[0013] Furthermore, the method for obtaining the voltage distortion rate by analyzing the response signal through Fourier transform within a sliding time window is as follows:

[0014] The voltage signals of each grounding selection loop are acquired in real time. A sliding time window is set to intercept and analyze the voltage signals. The duration of the sliding time window must be greater than 20ms and less than 100ms, and the sliding step size is set to 1 / 2 of the duration. Within each sliding time window, the fundamental component and each harmonic component of the voltage signal are decomposed by Fourier transform. The root mean square value of the fundamental component of the voltage signal is taken as the effective value of the fundamental voltage, and the root mean square value of each harmonic component of the voltage signal is taken as the effective value of the harmonic voltage. The ratio of the square root of the sum of the squares of the effective values ​​of each harmonic voltage to the effective value of the fundamental voltage is taken as the voltage distortion rate. When the voltage distortion rate of a certain grounding selection loop is greater than the preset standard limit, the grounding selection loop is marked as a target object. The value range of the standard limit is not less than 5%.

[0015] Furthermore, the method for determining whether harmonic distortion exists based on the amplitude and frequency of each harmonic is as follows:

[0016] The acquired current time-domain signal is subjected to harmonic decomposition using Fast Fourier Transform within a set sliding time window to obtain current spectrum data. Based on this current spectrum data, harmonic decomposition is performed to extract the amplitude and frequency information of each harmonic. After excluding the fundamental component, the square root of the sum of the squares of each harmonic amplitude is taken as the total harmonic amplitude. Then, the proportion of each harmonic amplitude to the total harmonic amplitude is calculated. When the proportion of a certain harmonic is greater than 10%, harmonic distortion is determined to exist.

[0017] Furthermore, the method for obtaining high-frequency spike pulse amplitude segments from the current time-domain signal using high-pass filtering and a sliding window peak detection algorithm is as follows:

[0018] For the current time-domain signal data corresponding to the target object, an 8th-order Butterworth high-pass filter is used to filter out low-frequency components, retain high-frequency signals, and take the absolute value of the signal intensity at each sampling point. High-frequency spike pulses are identified by a sliding window peak detection algorithm. Specifically, the mean of the high-frequency signal plus three times the standard deviation is used as the spike identification threshold. At least three consecutive sampling points greater than the spike identification threshold are merged as high-frequency spike pulse segments. The absolute value of the peak value in each high-frequency spike pulse segment is recorded one by one, and the maximum value is taken as the high-frequency spike pulse amplitude. The high-frequency spike pulse segment in which it is located is taken as the high-frequency spike pulse amplitude segment.

[0019] Furthermore, the method for pre-setting background noise is as follows:

[0020] Extract the current time-domain signal data of the target object when no voltage signal is injected and the system is in a stable no-load state. Use an 8th-order Butterworth high-pass filter to filter out low-frequency components, retain high-frequency signals, and take the absolute value of the signal intensity of each sampling point to calculate the mean and standard deviation. Then, add 3 times the standard deviation to the mean as the background noise.

[0021] Furthermore, the time difference is the result of subtracting the voltage distortion from the current distortion initiation time, and the time threshold range is 1-5ms.

[0022] Furthermore, a high-frequency energy distribution characteristic analysis is performed on the time-domain signal corresponding to the high-frequency spike pulse amplitude segment, and the method of taking the continuous frequency interval with the highest energy proportion as the main frequency interval is as follows:

[0023] A fast Fourier transform is applied to the time-domain signal corresponding to the high-frequency spike pulse amplitude segment to obtain the frequency-domain signal. In this frequency-domain signal, adjacent and uninterrupted frequency points are grouped into the same continuous frequency interval. Specifically, when the energy difference between a certain frequency point and its adjacent points is greater than 50%, a new interval is segmented from that point. The sum of the energy of each continuous frequency interval is calculated, that is, the sum of the energy of all frequency points in each continuous frequency interval. All continuous intervals are sorted in descending order, and the continuous frequency interval with the largest sum of energy is taken as the main frequency interval. The energy is the square of the signal strength value corresponding to the frequency point.

[0024] Furthermore, when the energy proportion of this main frequency range is higher than the preset energy proportion threshold of the total energy of high-frequency peaks, the method for analyzing and obtaining the corresponding center frequency and the bandwidth corresponding to the preset power attenuation is as follows:

[0025] A fast Fourier transform is performed on the time-domain signal corresponding to the amplitude segment of the high-frequency spike pulse to obtain the frequency-domain signal of the high-frequency spike. The sum of the energy of all frequency points in the frequency-domain signal is the total energy of the high-frequency spike. The sum of the energy of the main frequency interval is extracted. When the ratio of the sum of the energy of the main frequency interval to the total energy of the high-frequency spike is higher than a preset energy ratio threshold, subsequent analysis is performed; otherwise, it is directly determined to be non-electromagnetic radiation interference. The energy ratio threshold is not less than 0.8.

[0026] Using the energy of each frequency point within the main frequency range as a weight, the frequencies of all frequency points within the range are averaged using energy weighting, and the result is the center frequency. The frequency point with the highest energy within the main frequency range is selected, and the energy corresponding to this frequency point is the peak energy, and the corresponding frequency is the peak frequency. The corresponding energy ratio is determined based on a preset power attenuation, and the product of the peak energy and this energy ratio is set as the preset energy threshold. The energy of each frequency point is extracted sequentially from the peak frequency to the lower frequency direction, and the frequency whose energy is not greater than the preset energy threshold is the lower limit frequency. At the same time, the energy of each frequency point is checked sequentially from the peak frequency to the higher frequency direction, and the frequency whose energy is not greater than the preset energy threshold is the upper limit frequency. The difference between the upper limit frequency and the lower limit frequency is the bandwidth corresponding to the preset power attenuation, and the value of the power attenuation is in the range of 1dB-6dB.

[0027] Additionally, a target object electromagnetic radiation interference testing system is provided, characterized in that: the system is used to perform the above-mentioned target object electromagnetic radiation interference testing method, including:

[0028] The signal extraction module is used to inject voltage signals into each grounding selection circuit in the power system at equal time intervals, analyze the response signal through Fourier transform within a sliding time window to obtain the voltage distortion rate, mark the grounding selection circuit with a voltage distortion rate greater than the preset standard limit as the target object, and collect its current time domain signal.

[0029] The signal analysis module is used to perform fast Fourier transform on the acquired current time-domain signal to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, it determines whether there is harmonic distortion. It uses high-pass filtering and sliding window peak detection algorithm to obtain high-frequency spike pulse amplitude segments on the current time-domain signal.

[0030] The time difference calculation module is used to preset the background noise. When there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of the current distortion. The start time of the time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of the voltage distortion. The time difference is calculated based on the start times of the current distortion and voltage distortion.

[0031] The interference determination module is used to perform high-frequency energy distribution characteristic analysis on the time domain signal corresponding to the high-frequency spike pulse amplitude segment when the time difference is within a preset time threshold range. The continuous frequency range with the highest energy proportion is taken as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention injects voltage signals into each grounding selection circuit in the power system at equal time intervals. Grounding selection circuits with voltage distortion rates exceeding preset standard limits are marked as target objects. The high-frequency spike pulse amplitude of the target object is analyzed in relation to the time difference between the voltage distortion and the main frequency range energy ratio. The invention determines whether the injected voltage signal has the characteristics of electromagnetic radiation, such as current spikes appearing before voltage distortion, high-frequency energy concentration, and narrow bandwidth, thereby correcting malfunctions of the grounding selection device. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall method flow of the present invention;

[0035] Figure 2 This is a schematic diagram of the effective values ​​of the fundamental and harmonic voltages of this invention;

[0036] Figure 3 This is a schematic diagram of the voltage distortion rate of the present invention;

[0037] Figure 4 This is a statistical chart of the high-frequency spike pulse amplitude of the present invention;

[0038] Figure 5This is a schematic diagram illustrating the bandwidth ratio calculation of the present invention;

[0039] Figure 6 This is a schematic diagram of the overall system structure of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0041] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0042] Example:

[0043] Please see Figures 1 to 5 The present invention provides a technical solution:

[0044] The electromagnetic radiation interference test method for the target object includes the following specific steps:

[0045] S1: Inject voltage signals into each grounding selection circuit in the power system at equal time intervals. Analyze the response signal using Fourier transform within a sliding time window to obtain the voltage distortion rate. Mark the grounding selection circuit with a voltage distortion rate greater than the preset standard limit as the target object and collect its current time domain signal.

[0046] At equal time intervals, voltage signals are injected into each grounding selection circuit in the power system. The voltage value of the signal is no more than 10% of the rated voltage of the circuit, and the waveform is a sine wave. This can cause the circuit to generate a response signal. The distortion characteristics of the response signal can be used to identify whether there is external electromagnetic radiation interference.

[0047] The voltage signals of each grounding selection loop are acquired in real time, and these voltage signals serve as the response signals. A sliding time window is set to extract and analyze the voltage signals. The duration of the sliding time window must be greater than 20ms and less than 100ms. The power system frequency is 50Hz, and the corresponding fundamental period is 20ms. The duration of this sliding time window must include at least one complete fundamental period to improve the accuracy of the judgment. The sliding step size is set to half of this duration to ensure that the distortion characteristics are covered by at least one sliding time window. For voltage signal research, only abnormal loops are screened. Within each sliding time window, the core of Fourier transform is to convert the time-domain voltage signal into a frequency-domain signal. Therefore, the fundamental component and harmonic components of the voltage signal are decomposed by Fourier transform. The root mean square (RMS) value of the fundamental component is taken as the effective value of the fundamental voltage, and the RMS values ​​of each harmonic component are taken as the effective values ​​of the harmonic voltages. The harmonics are the 3rd, 5th, and 7th harmonics, which are common harmonic characteristics. The ratio of the square root of the sum of the squares of the effective values ​​of each harmonic voltage to the effective value of the fundamental voltage is taken as the voltage distortion rate. This formula characterizes the proportion of the total harmonics relative to the fundamental voltage. When the voltage distortion rate of a certain grounding selection loop exceeds a preset standard limit, the grounding selection loop is marked as a target object. The standard limit can be set to 5%, which is a common industry standard requirement. Figures 2-3 As shown, the voltage distortion rate calculated based on the effective value of the fundamental voltage and the maximum effective value of the harmonic voltage can be compared with the standard limit to determine whether the target object has occurred, and then the corresponding current time domain signal can be collected.

[0048] S2: Perform a fast Fourier transform on the acquired current time-domain signal to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, determine whether there is harmonic distortion. Use a high-pass filter and sliding window peak detection algorithm on the current time-domain signal to obtain high-frequency spike pulse amplitude segments.

[0049] In power systems, voltage signals are easily affected by external environments such as grid fluctuations and load changes, which may distort the results of real-time analysis. Therefore, it is necessary to analyze the current time-domain signal. The collected current time-domain signal data is subjected to harmonic decomposition using Fast Fourier Transform (FFT) within a set sliding time window to obtain the current spectrum data, which is faster. Based on the calculation results, subsequent analysis and response can be completed. The specific process of obtaining the current spectrum data by harmonic decomposition using FFT is as follows:

[0050] The acquired time-domain current signal is used to construct a sequence as current data. The current data is padded with zeros to powers of 2. For example, when the sampling frequency is 5000Hz and the sliding time window is 200ms, zeros are padded to 1024 points. The DFT forward transform result of the zero-padded current sequence is then converted into a complex sequence.

[0051]

[0052] This is represented as a sequence of current data padded with zeros to the nearest power of 2. Represented as the imaginary unit, It is represented as a complex exponential basis function, where, Represents discrete frequency point indices. , This represents the length of the power of the current data sequence padded with zeros to the nearest power of 2. This represents the index of the sampling point in the discrete-time current data sequence before zero-padding, with values ​​ranging from 0 to 999. This represents the first current data sequence before zero-padding within the sliding time window. The FFT process takes discrete-time sampling points, then uses a butterfly operation to output a complex number sequence, consisting of real and imaginary parts. The real part of each complex number is squared, and then the imaginary part is also squared. The two squared results are added together, and the square root of the sum is taken to obtain the amplitude. Since the spectrum obtained after FFT processing is symmetrical, the analysis only needs to focus on the first half of the frequency points. For the first half of the frequency points, except for the first point representing the DC component, all other frequency points need to be multiplied by 2 and divided by the total length of the current data before zero-padding to restore the actual signal strength. The fundamental, 3rd, 5th, and 7th harmonics are obtained by multiplying the index of each point by the sampling frequency and then dividing by the total length after zero-padding. The nearest frequency index corresponds to the effective value of the current corresponding to the frequency component, i.e., the effective value of the corresponding harmonic and fundamental wave. First, the effective values ​​of the 3rd, 5th, and 7th harmonics are squared respectively, and then these squared results are added together. The square root of the sum is taken to obtain the total effective value of the harmonics. The ratio of the effective value of each harmonic to the total effective value of the harmonics is calculated. When the calculated result of the ratio based on a certain harmonic is greater than 10%, it is determined that there is harmonic distortion in the current time domain signal under the sliding time window, as shown in Table 1. The total harmonic amplitude under each sliding time window is obtained, and the maximum value of the ratio of each harmonic effective value to the total effective value of the harmonics under each sliding time window is statistically analyzed to generate a harmonic distortion judgment table.

[0053] Table 1 Harmonic Distortion Judgment Table

[0054]

[0055] For the current time-domain signal data corresponding to the target object, an 8th-order Butterworth high-pass filter is used to filter out low-frequency components. The cutoff frequency can be set to 1kHz to retain only the high-frequency signal caused by electromagnetic radiation, filtering out low-frequency interference such as the fundamental wave, low-order harmonics, and power grid fluctuations. The high-frequency signal is retained only when the sampling point index remains unchanged and the numerical value is recalculated. The absolute value of the current at each sampling point of the high-frequency signal is taken to characterize the intensity of high-frequency spike pulses. A sliding window peak detection algorithm is used to identify high-frequency spike pulses in the time-domain waveform.

[0056] In the sliding window peak detection algorithm, the sliding window duration can be set to 1 / 20-1 / 10 of the sliding time window, and the step size is 1 / 2 of the duration of its own sliding window. The absolute value of the current is used as the benchmark, and the mean of the high-frequency signal plus three times the standard deviation is used as the peak identification threshold. Within each sliding window, the absolute value of each sampling point is checked to see if it is greater than the peak identification threshold. When the absolute values ​​of at least three consecutive sampling points are greater than the peak identification threshold, the consecutive sampling points are merged into a high-frequency peak pulse segment. The start and end indices of each segment are recorded based on the sampling point indices. Since the step size is 1 / 2 of the duration of its own sliding window, at least 50% of the consecutive points in any peak segment spanning two sliding windows will fall within the peak. Within one window, the same peak segment may be covered by multiple windows. Therefore, the start and end indices of the high-frequency peak pulse segments are merged. For example, if the start and end indices of one high-frequency peak pulse segment are 20 and 24, and the start and end indices of another high-frequency peak pulse segment are 25 and 30, then the start and end indices of the merged high-frequency peak pulse segment are 20 and 30. The reason for merging consecutive sampling points into a high-frequency peak pulse segment when the absolute value of at least 3 consecutive sampling points is greater than the peak identification threshold is that electromagnetic radiation is a continuous pulse signal, and a single sampling point greater than the peak identification threshold is likely to be high-frequency noise.

[0057] Within each sliding time window, the absolute value of the peak value within each high-frequency spike pulse segment is recorded sequentially, and the maximum value is taken as the high-frequency spike pulse amplitude of that sliding time window. This segment, as the core carrier of the most concentrated electromagnetic radiation interference energy, can most realistically reflect the nature of the interference in terms of its time-domain waveform and frequency characteristics, making the electromagnetic radiation interference more representative and providing a data foundation for subsequent high-frequency energy distribution characteristic analysis. The time-domain signal of the high-frequency spike pulse segment containing the high-frequency spike pulse amplitude is retained as the high-frequency spike pulse amplitude segment. This time-domain signal segment is the signal strength of all original sampling points in the high-frequency signal after high-pass filtering. This signal contains only high-frequency components, avoiding interference from low-frequency signals to the frequency domain analysis.

[0058] S3: Preset background noise. When there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of current distortion. The start time of the sliding time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of voltage distortion. The time difference is calculated based on the start times of current distortion and voltage distortion.

[0059] The process of presetting background noise is as follows:

[0060] Extract the current time-domain signal data of the target object when no voltage signal is injected and the system is in a stable no-load state. The same operation as S2 is used. Use an 8th order Butterworth high-pass filter to filter out low-frequency components and retain high-frequency signals to avoid signal waveform distortion caused by phase distortion. Ensure that the time-domain signal statistical logic of noise and high-frequency spike pulse segments is consistent. Take the absolute value of the signal intensity of each sampling point of the high-frequency signal and calculate the mean and standard deviation. Add 3 times the standard deviation to the mean as the background noise, which conforms to the normal distribution 3σ criterion.

[0061] like Figure 4 As shown, when the background noise is 0.020A, the amplitude of the high-frequency spike pulses in multiple sliding time windows is greater than the background noise. Then, the following operations are performed independently within each sliding time window:

[0062] First, determine if the current time-domain signal simultaneously exhibits harmonic distortion and the high-frequency spike pulse amplitude is greater than the background noise. If both conditions are met, locate the high-frequency spike pulse segment based on its amplitude. Take the absolute value of the signal intensity at all sampling points of this segment and compare it point by point with the background noise. Mark the moment corresponding to the first sampling point with the amplitude greater than the background noise as the start time of the current distortion. This is because this moment is the physical starting point where electromagnetic radiation interference triggers the current signal to deviate from the normal noise level. Locate the sliding time window when the voltage distortion rate first exceeds the preset standard limit. The starting time is calibrated as the voltage distortion start time. The voltage distortion rate is the result of analysis within a sliding time window, reflecting the degree of harmonic pollution throughout the window. The start time of the first exceeding the limit window is the earliest possible time of distortion. Finally, based on the above-calibrated current distortion start time and voltage distortion start time, the time difference is calculated, that is, the difference between the current distortion start time and the voltage distortion start time. The electromagnetic radiation source first couples to the voltage loop, causing voltage harmonic distortion, and then couples to the current loop through electromagnetic induction / capacitance. The calculated time difference provides data support for subsequent judgment on whether it is electromagnetic radiation interference.

[0063] S4: When the time difference is within the preset time threshold range, perform high-frequency energy distribution characteristic analysis on the time domain signal corresponding to the high-frequency spike pulse amplitude segment, and take the continuous frequency range with the highest energy proportion as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, analyze it to obtain the corresponding center frequency and the bandwidth corresponding to the preset power attenuation. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

[0064] In power systems, voltage and current distortions during faults are almost synchronous. Therefore, the time threshold range is 1-5ms, which aligns with the time delay between voltage distortion caused by electromagnetic radiation interference and subsequent current distortion due to electromagnetic propagation. When the time difference is within the preset time threshold range, the number of sampling points for the high-frequency spike pulse amplitude segment is padded with zeros to the nearest power of 2. A Fast Fourier Transform is then performed to convert the time-domain signal to a frequency-domain signal. All frequency points in the frequency-domain signal are traversed sequentially according to their indexes, and adjacent, uninterrupted frequency points are grouped into the same continuous frequency interval. Specifically, since the core characteristic of electromagnetic radiation interference in the frequency domain is that energy is concentrated in a continuous small frequency range... The characteristic of noise / irrelevant interference is that energy is scattered across multiple frequency points, thus corresponding to narrowband concentration and broadband dispersion, respectively. Therefore, when the energy difference between a certain frequency point and its adjacent points is greater than 50%, a new interval is defined from that point, as different signal categories are considered. The energy distribution law of electromagnetic radiation interference is that energy will be concentrated in a narrowband interval. Therefore, the sum of energy of each continuous frequency interval is calculated, that is, the sum of energy of all frequency points in each continuous frequency interval. All continuous intervals are sorted in descending order, and the continuous frequency interval with the largest sum of energy is taken as the main frequency interval. Noise and other scattered energy interference are excluded. The energy is the square of the value of the signal strength corresponding to the frequency point.

[0065] The energy of all frequency points in the frequency domain signal is accumulated, and the result is the total energy of the high-frequency peaks. The ratio of the sum of energy in the main frequency range to the total energy of the high-frequency peaks is calculated. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency peaks, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. According to engineering experience, when the ratio is lower than 0.8, it is considered that the energy is dispersed and does not meet the frequency domain characteristics brought by electromagnetic radiation. When the ratio is higher than 0.8, subsequent analysis is performed. Otherwise, it is directly judged as non-electromagnetic radiation interference.

[0066] Using the energy of each frequency point within the main frequency range as the weight, perform an energy-weighted average of the frequencies of all frequency points within the range:

[0067]

[0068] In the formula, Indicates the center frequency of the main frequency range. This indicates the total number of frequency points contained within the main frequency range. Indicates the number of frequencies within the main frequency range. Frequency values ​​at each frequency point Indicates the first Energy at each frequency point Indicates the index of the frequency point within the main frequency range. The result of the formula is the center frequency. The higher the energy of the frequency point, the greater the weight, thereby suppressing the interference of frequency domain noise on feature extraction and reflecting the true frequency domain center of the energy accumulation region in the high-frequency peak pulse amplitude segment.

[0069] The core of calculating the bandwidth corresponding to the preset power attenuation is to quantify the frequency domain concentration of the high-frequency spike pulse signal. Essentially, it defines the effective distribution range of signal energy by attenuating the signal power to a frequency range corresponding to the peak power. The power attenuation value ranges from 1dB to 6dB, corresponding to an energy ratio of 25% to 79.4%, assuming low noise interference and more accurate bandwidth calculation. The specific calculation logic is as follows: Within the main frequency range, the frequency point with the highest energy is selected; the energy corresponding to this frequency point is the peak energy, and the corresponding frequency is the peak frequency. Based on the preset power attenuation, the corresponding energy ratio is determined, and the product of the peak energy and this energy ratio is set as the preset energy threshold. The energy of each frequency point is extracted sequentially from the peak frequency towards lower frequencies; the frequency whose energy is not greater than the preset energy threshold is the lower limit frequency. Simultaneously, the energy of each frequency point is checked sequentially from the peak frequency towards higher frequencies; the frequency whose energy is not greater than the preset energy threshold is the upper limit frequency. The difference between the upper limit frequency and the lower limit frequency is the bandwidth corresponding to the preset power attenuation. The bandwidth is a key frequency domain characteristic parameter that distinguishes narrowband electromagnetic radiation interference from broadband anomalous signals: the energy of electromagnetic radiation interference is highly concentrated, and the bandwidth corresponding to the preset power attenuation is relatively narrow; while the energy of broadband anomalous signals is dispersed, and the bandwidth corresponding to the preset power attenuation is significantly larger. The preset frequency range, considering the typical frequency range of electromagnetic radiation, can be set to 10kHz-1MHz. The center frequency is compared with the preset frequency range, and the ratio of the bandwidth corresponding to the preset power attenuation to the center frequency is calculated, i.e., the relative bandwidth. When the center frequency is within the preset frequency range and the relative bandwidth meets the preset relative bandwidth threshold, it is determined that the target object is subject to electromagnetic radiation interference.

[0070] For example, setting a preset power attenuation of 3dB is a common choice in signal processing. This reflects the true frequency range of narrowband signals and quantifies the frequency concentration of high-frequency spike pulse signals. Essentially, it defines the effective distribution range of signal energy by attenuating the signal power to the frequency range corresponding to 50% of the peak power. This 50% represents the corresponding energy proportion. Within the main frequency range, the frequency point with the highest energy is selected; the energy corresponding to this frequency point is the peak energy, and the corresponding frequency is the peak frequency. Setting 50% of the peak energy as the energy threshold for the -3dB bandwidth, the energy of each frequency point is extracted sequentially from the peak frequency to lower frequencies. The frequency whose energy is not greater than this threshold is the lower limit frequency. Simultaneously, the energy of each frequency point is checked sequentially from the peak frequency to higher frequencies; the frequency whose energy is not greater than this threshold is the lower limit frequency. The upper limit frequency, and the difference between the upper and lower limits, is the -3dB bandwidth. This indicator is a key frequency domain characteristic parameter for distinguishing narrowband electromagnetic interference from broadband anomalous signals. Electromagnetic interference has a highly concentrated energy, corresponding to a narrower -3dB bandwidth; while broadband anomalous signals have a dispersed energy distribution, resulting in a significantly larger -3dB bandwidth. The center frequency is compared with a preset frequency range, and the ratio of the -3dB bandwidth to the center frequency is calculated. A relative bandwidth threshold of 0.1 is a common choice for distinguishing between narrowband and broadband signals. Electromagnetic interference is a typical narrowband signal with highly concentrated energy. A ratio of -3dB bandwidth to the center frequency less than 0.1 means that the effective energy of the signal is concentrated within a frequency band of ±5% of the center frequency, which conforms to the energy distribution pattern of electromagnetic interference. Figure 5 As shown, the center frequency is between 35-48kHz. In some sliding time windows, the ratio of the -3dB bandwidth to the center frequency is less than 0.1. This may indicate that the target object is subject to electromagnetic radiation interference during these sliding time windows. It is necessary to comprehensively consider whether there is harmonic distortion, whether the amplitude of the high-frequency spike pulse is greater than the background noise, and whether the time difference is within the preset time threshold range to determine whether the target object is subject to electromagnetic radiation interference. Therefore, when all other conditions are met, and the center frequency is within this frequency range and the ratio of the -3dB bandwidth to the center frequency is less than 0.1, it is determined that the target object is subject to electromagnetic radiation interference.

[0071] Please see Figure 6 The present invention further provides a target object electromagnetic radiation interference testing system for performing the above-described target object electromagnetic radiation interference testing method, comprising:

[0072] The signal extraction module is used to inject voltage signals into each grounding selection circuit in the power system at equal time intervals, analyze the response signal through Fourier transform within a sliding time window to obtain the voltage distortion rate, mark the grounding selection circuit with a voltage distortion rate greater than the preset standard limit as the target object, and collect its current time domain signal.

[0073] The signal analysis module is used to perform fast Fourier transform on the acquired current time-domain signal to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, it determines whether there is harmonic distortion. It uses high-pass filtering and sliding window peak detection algorithm to obtain high-frequency spike pulse amplitude segments on the current time-domain signal.

[0074] The time difference calculation module is used to preset the background noise. When there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of the current distortion. The start time of the time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of the voltage distortion. The time difference is calculated based on the start times of the current distortion and voltage distortion.

[0075] The interference determination module is used to perform high-frequency energy distribution characteristic analysis on the time domain signal corresponding to the high-frequency spike pulse amplitude segment when the time difference is within a preset time threshold range. The continuous frequency range with the highest energy proportion is taken as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

[0076] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0077] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0078] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0079] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for testing electromagnetic radiation interference from a target object, characterized in that, The specific steps include: Voltage signals are injected into each grounding selection circuit in the power system at equal time intervals. The voltage distortion rate is obtained by analyzing the response signal through Fourier transform within a sliding time window. Grounding selection circuits with voltage distortion rates greater than the preset standard limit are marked as target objects, and their current time domain signals are collected. The acquired current time-domain signal is subjected to fast Fourier transform to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, it is determined whether there is harmonic distortion. High-pass filtering and sliding window peak detection algorithm are used to obtain high-frequency spike pulse amplitude segments from the current time-domain signal. With a preset background noise, when there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of current distortion, and the start time of the time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of voltage distortion. The time difference is calculated based on the start times of current distortion and voltage distortion. When the time difference is within the preset time threshold range, the time domain signal corresponding to the high-frequency spike pulse amplitude segment is analyzed for high-frequency energy distribution characteristics. The continuous frequency range with the highest energy proportion is taken as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

2. The method for testing electromagnetic radiation interference of a target object according to claim 1, characterized in that: The method for obtaining the voltage distortion rate by analyzing the response signal through Fourier transform under a sliding time window is as follows: The voltage signals of each grounding selection loop are acquired in real time. A sliding time window is set to intercept and analyze the voltage signals. The duration of the sliding time window must be greater than 20ms and less than 100ms, and the sliding step size is set to 1 / 2 of the duration. Within each sliding time window, the fundamental component and each harmonic component of the voltage signal are decomposed by Fourier transform. The root mean square value of the fundamental component of the voltage signal is taken as the effective value of the fundamental voltage, and the root mean square value of each harmonic component of the voltage signal is taken as the effective value of the harmonic voltage. The ratio of the square root of the sum of the squares of the effective values ​​of each harmonic voltage to the effective value of the fundamental voltage is taken as the voltage distortion rate. When the voltage distortion rate of a certain grounding selection loop is greater than the preset standard limit, the grounding selection loop is marked as a target object. The value range of the standard limit is not less than 5%.

3. The method for testing electromagnetic radiation interference of a target object according to claim 1, characterized in that: The method for determining the existence of harmonic distortion based on the amplitude and frequency of each harmonic is as follows: The acquired current time-domain signal is subjected to harmonic decomposition using Fast Fourier Transform within a set sliding time window to obtain current spectrum data. Based on this current spectrum data, harmonic decomposition is performed to extract the amplitude and frequency information of each harmonic. After excluding the fundamental component, the square root of the sum of the squares of each harmonic amplitude is taken as the total harmonic amplitude. Then, the proportion of each harmonic amplitude to the total harmonic amplitude is calculated. When the proportion of a certain harmonic is greater than 10%, harmonic distortion is determined to exist.

4. The method for testing electromagnetic radiation interference of a target object according to claim 2, characterized in that: The method for obtaining high-frequency spike pulse amplitude segments from current time-domain signals using high-pass filtering and sliding window peak detection algorithms is as follows: For the current time-domain signal data corresponding to the target object, an 8th-order Butterworth high-pass filter is used to filter out low-frequency components, retain high-frequency signals, and take the absolute value of the signal intensity at each sampling point. High-frequency spike pulses are identified by a sliding window peak detection algorithm. Specifically, the mean of the high-frequency signal plus three times the standard deviation is used as the spike identification threshold. At least three consecutive sampling points greater than the spike identification threshold are merged as high-frequency spike pulse segments. The absolute value of the peak value in each high-frequency spike pulse segment is recorded one by one, and the maximum value is taken as the high-frequency spike pulse amplitude. The high-frequency spike pulse segment in which it is located is taken as the high-frequency spike pulse amplitude segment.

5. The method for testing electromagnetic radiation interference of a target object according to claim 4, characterized in that: The method for presetting background noise is as follows: Extract the current time-domain signal data of the target object when no voltage signal is injected and the system is in a stable no-load state. Use an 8th-order Butterworth high-pass filter to filter out low-frequency components, retain high-frequency signals, and take the absolute value of the signal intensity of each sampling point to calculate the mean and standard deviation. Then, add 3 times the standard deviation to the mean as the background noise.

6. The method for testing electromagnetic radiation interference of a target object according to claim 4, characterized in that: The time difference is the result of subtracting the start time of voltage distortion from the start time of current distortion, and the time threshold range is 1-5ms.

7. The method for testing electromagnetic radiation interference of a target object according to claim 1, characterized in that: The method for performing high-frequency energy distribution characteristic analysis on the time-domain signal corresponding to the high-frequency spike pulse amplitude segment, and selecting the continuous frequency interval with the highest energy proportion as the main frequency interval, is as follows: A fast Fourier transform is applied to the time-domain signal corresponding to the high-frequency spike pulse amplitude segment to obtain the frequency-domain signal. In this frequency-domain signal, adjacent and uninterrupted frequency points are grouped into the same continuous frequency interval. Specifically, when the energy difference between a certain frequency point and its adjacent points is greater than 50%, a new interval is segmented from that point. The sum of the energy of each continuous frequency interval is calculated, that is, the sum of the energy of all frequency points in each continuous frequency interval. All continuous intervals are sorted in descending order, and the continuous frequency interval with the largest sum of energy is taken as the main frequency interval. The energy is the square of the signal strength value corresponding to the frequency point.

8. The method for testing electromagnetic radiation interference of a target object according to claim 7, characterized in that: When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total high-frequency peak energy, the method for analyzing and obtaining the corresponding center frequency and the bandwidth corresponding to the preset power attenuation is as follows: A fast Fourier transform is performed on the time-domain signal corresponding to the amplitude segment of the high-frequency spike pulse to obtain the frequency-domain signal of the high-frequency spike. The sum of the energy of all frequency points in the frequency-domain signal is the total energy of the high-frequency spike. The sum of the energy of the main frequency interval is extracted. When the ratio of the sum of the energy of the main frequency interval to the total energy of the high-frequency spike is higher than a preset energy ratio threshold, subsequent analysis is performed; otherwise, it is directly determined to be non-electromagnetic radiation interference. The energy ratio threshold is not less than 0.

8. Using the energy of each frequency point within the main frequency range as a weight, the frequencies of all frequency points within the range are averaged using energy weighting, and the result is the center frequency. The frequency point with the highest energy within the main frequency range is selected, and the energy corresponding to this frequency point is the peak energy, and the corresponding frequency is the peak frequency. The corresponding energy ratio is determined based on a preset power attenuation, and the product of the peak energy and this energy ratio is set as the preset energy threshold. The energy of each frequency point is extracted sequentially from the peak frequency to the lower frequency direction, and the frequency whose energy is not greater than the preset energy threshold is the lower limit frequency. At the same time, the energy of each frequency point is checked sequentially from the peak frequency to the higher frequency direction, and the frequency whose energy is not greater than the preset energy threshold is the upper limit frequency. The difference between the upper limit frequency and the lower limit frequency is the bandwidth corresponding to the preset power attenuation, and the value of the power attenuation is in the range of 1dB-6dB.

9. A target object electromagnetic radiation interference testing system, characterized in that: The system is used to perform the electromagnetic radiation interference test method for a target object as described in any one of claims 1-8: The signal extraction module is used to inject voltage signals into each grounding selection circuit in the power system at equal time intervals, analyze the response signal through Fourier transform within a sliding time window to obtain the voltage distortion rate, mark the grounding selection circuit with a voltage distortion rate greater than the preset standard limit as the target object, and collect its current time domain signal. The signal analysis module is used to perform fast Fourier transform on the acquired current time-domain signal to obtain the amplitude and frequency of each harmonic. Based on the amplitude and frequency of each harmonic, it determines whether there is harmonic distortion. It uses high-pass filtering and sliding window peak detection algorithm to obtain high-frequency spike pulse amplitude segments on the current time-domain signal. The time difference calculation module is used to preset the background noise. When there is harmonic distortion and the amplitude of the high-frequency spike pulse is greater than the background noise, the moment when the amplitude of the high-frequency spike pulse segment first exceeds the preset background noise is marked as the start time of the current distortion. The start time of the time window when the voltage distortion rate first exceeds the preset standard limit is marked as the start time of the voltage distortion. The time difference is calculated based on the start times of the current distortion and voltage distortion. The interference determination module is used to perform high-frequency energy distribution characteristic analysis on the time domain signal corresponding to the high-frequency spike pulse amplitude segment when the time difference is within a preset time threshold range. The continuous frequency range with the highest energy proportion is taken as the main frequency range. When the energy proportion of the main frequency range is higher than the preset energy proportion threshold of the total energy of the high-frequency spikes, the corresponding center frequency and the bandwidth corresponding to the preset power attenuation are obtained through analysis. When the center frequency of the main frequency range is within the preset frequency range and the proportion of the bandwidth to the center frequency is lower than the relative bandwidth threshold, it is determined to be electromagnetic radiation interference.

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