Method, device and system for measuring oil level of oil conservator of transformer

Abstract

The invention relates to the technical field of oil level measurement, in particular to a transformer oil conservator oil level measurement method, device and system.The method comprises the steps that high-frequency pulse sound wave signals sent by ultrasonic liquid level sensors and echo signals received by the ultrasonic liquid level sensors are collected, and the initial sound wave transmission time of the high-frequency pulse sound wave signals is obtained; acquiring a characteristic factor of each intrinsic mode function of each echo signal; reconstructing a de-noised echo signal of each echo signal through characteristic factor distribution of all intrinsic mode functions of each echo signal; obtaining each echo signal segment of each de-noised echo signal and an impurity interference coefficient of each echo signal segment; obtaining the impurity interference degree of each ultrasonic liquid level sensor; and calculating the oil level height in the oil conservator. The invention aims to improve the precision of the measurement result of the oil level height in the oil conservator by improving the measurement precision of the transmission time of the high-frequency pulse sound wave signal.

Description

Technical Field

[0001] This application relates to the technical field of oil level measurement, and particularly to a method, device, and system for measuring the oil level of a transformer conservator tank. Background Art

[0002] The conservator tank is a key component supporting oil-immersed power transformers. By measuring the oil level, the consumption and change trend of transformer oil can be understood, which helps to promptly detect abnormal oil levels in the conservator tank and take corresponding measures to ensure the safe and stable operation of power transformers.

[0003] Currently, ultrasonic measurement methods are often used to measure the oil level in the transformer conservator tank. However, due to the influence of the surrounding environmental temperature and humidity during the use of the transformer conservator tank, there are often impurities such as metal particles, sediment, and bubbles in the conservator tank. The existing ultrasonic measurement methods ignore the interference of impurities in the conservator tank on the propagation of ultrasonic waves, resulting in inaccurate ultrasonic transmission time, and further causing the measurement result of the oil level height in the conservator tank to deviate from the actual oil level height. Summary of the Invention

[0004] In view of the above, it is necessary to provide a method, device, and system for measuring the oil level of a transformer conservator tank. Compared with traditional oil level measurement methods, by improving the measurement accuracy of the transmission time of high-frequency pulsed acoustic wave signals, the accuracy of the measurement result of the oil level height in the conservator tank is improved: In a first aspect, an embodiment of the present application provides a method for measuring the oil level of a transformer conservator tank, the method comprising the following steps: Collect high-frequency pulsed acoustic wave signals sent by each ultrasonic liquid level sensor and received echo signals, and obtain the initial acoustic wave transmission time of each high-frequency pulsed acoustic wave signal; Obtain each intrinsic mode function of each echo signal, and by analyzing the correlation in the time domain and the similarity of the frequency distribution in the frequency domain between each intrinsic mode function and all high-frequency pulsed acoustic wave signals, obtain the characteristic factor of each intrinsic mode function; reconstruct the denoised echo signal of each echo signal through the distribution of the characteristic factors of all intrinsic mode functions of each echo signal; Use an endpoint detection algorithm to obtain each echo signal segment of each denoised echo signal, and by comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distributions of each echo signal segment of the remaining denoised echo signals, obtain each reference echo signal segment of the said echo signal segment; By analyzing the difference in the complexity of the signal distribution and the amplitude difference between each echo signal segment and its each reference echo signal segment, obtain the impurity interference coefficient of each echo signal segment; Obtain the impurity interference degree of each ultrasonic liquid level sensor through the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor; Calculate the oil level height in the conservator through the impurity interference degree and the initial acoustic wave transmission time.

[0005] In one of the embodiments, the process of obtaining the characteristic factor is as follows: Use the coherent averaging method to obtain the average time-domain signal of all high-frequency pulsed acoustic wave signals; Calculate the correlation coefficient between each intrinsic mode function and the average time-domain signal; Use the Fourier transform to obtain the spectra of each intrinsic mode function and the average time-domain signal respectively, and calculate the spectral similarity between the spectra of each intrinsic mode function and the average time-domain signal; Take the product of the correlation coefficient and the spectral similarity as the characteristic factor of each intrinsic mode function.

[0006] In one of the embodiments, the process of obtaining the denoised echo signal is as follows: Adopt a threshold segmentation algorithm to obtain the segmentation threshold of the characteristic factors of all intrinsic mode functions of any echo signal; Reconstruct the signals of all intrinsic mode functions greater than the segmentation threshold to obtain the denoised echo signal of the any echo signal.

[0007] In one of the embodiments, the process of obtaining the control echo signal segment is as follows: Take the moment when the sampling point with the largest amplitude in each echo signal segment is located as the echo arrival moment of each echo signal segment; From each denoised echo signal except the any denoised echo signal, respectively screen the echo signal segment with the shortest time interval of the echo arrival moment between it and the any echo signal segment as each control echo signal segment of the any echo signal segment.

[0008] In one of the embodiments, the process of obtaining the impurity interference coefficient is as follows: Calculate the entropy of each echo signal segment; Take the average value of the amplitudes of all sampling points in each echo signal segment as the signal amplitude of each echo signal segment; Calculate the difference between the entropy of each echo signal segment and the entropy of its corresponding control echo signal segment; Denote the mean value of all the differences of each echo signal segment as the first difference mean value; Denote the difference between the signal amplitude of each echo signal segment and the signal amplitude of its corresponding control echo signal segment as the amplitude difference; Denote the mean value of all the amplitude differences of each echo signal segment as the second difference mean value; Combine the first difference mean value and the second difference mean value to obtain the impurity interference coefficient of each echo signal segment.

[0009] In one embodiment, the calculation process of the impurity interference coefficient is as follows: map the mean value of the second difference to a positive number, and use the ratio of the mean value of the first difference to the positive number as the impurity interference coefficient of each echo signal segment.

[0010] In one embodiment, the impurity interference degree is the mean value of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor.

[0011] In one embodiment, calculating the oil level height in the conservator includes: Calculate the comprehensive acoustic wave transmission time of all high-frequency pulsed acoustic wave signals through the impurity interference degree and the initial acoustic wave transmission time. The expression is: ; where T represents the comprehensive acoustic wave transmission time of all high-frequency pulsed acoustic wave signals; M represents the number of ultrasonic liquid level sensors; map the impurity interference degree of each ultrasonic liquid level sensor to a positive number, denoted as the mapped positive number, S(i) represents the normalized value of the reciprocal of the mapped positive number of the i-th ultrasonic liquid level sensor; t(i) represents the initial acoustic wave transmission time of the high-frequency pulsed acoustic wave signal sent by the i-th ultrasonic liquid level sensor; Calculate the oil level height in the conservator through the comprehensive acoustic wave transmission time.

[0012] Second, the embodiment of the present application also provides a transformer conservator oil level measurement device, and the device includes: A signal acquisition module, configured to acquire the high-frequency pulsed acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and obtain the initial acoustic wave transmission time of each high-frequency pulsed acoustic wave signal; A signal analysis module, configured to obtain each intrinsic mode function of each echo signal, and obtain the characteristic factor of each intrinsic mode function by analyzing the correlation in the time domain and the similarity of the frequency distribution in the frequency domain between each intrinsic mode function and all high-frequency pulsed acoustic wave signals; reconstruct the denoised echo signal of each echo signal through the distribution of the characteristic factors of all intrinsic mode functions of each echo signal; Use the endpoint detection algorithm to obtain each echo signal segment of each denoised echo signal, and obtain each comparison echo signal segment of the any echo signal segment by comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distributions of each echo signal segment of the remaining denoised echo signals; Obtain the impurity interference coefficient of each echo signal segment by analyzing the difference in the complexity of the signal distribution and the amplitude difference between each echo signal segment and its each comparison echo signal segment; Obtain the impurity interference degree of each ultrasonic liquid level sensor through the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor; An oil level calculation module, configured to calculate the oil level height in the conservator through the impurity interference degree and the initial acoustic wave transmission time.

[0013] In a third aspect, an oil level measurement system for a transformer conservator provided by an embodiment of the present application includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the method for measuring the oil level of a transformer conservator described in any one of the above are implemented.

[0014] The present application has at least the following beneficial effects: By analyzing the correlation in the time domain and the similarity in the frequency domain between the intrinsic mode function of the echo signal and the high-frequency pulsed acoustic wave signal, the present application calculates the characteristic factor of the intrinsic mode function of the wave echo signal to preprocess the echo signal. Compared with directly using existing signal denoising algorithms, it can effectively filter out the noise and irrelevant clutter signals in the echo signals received by each ultrasonic liquid level sensor, and reduce the influence of the noise and irrelevant clutter signals on the subsequent evaluation of the degree of impurity interference of the echo signal. By analyzing the amplitude difference between the echo signal segments generated within the same time range and the complexity difference of the signal distribution, the present application evaluates the degree of impurity interference of the echo signals received by each ultrasonic liquid level sensor in the transformer conservator, and performs weighted processing on the initial acoustic wave transmission times obtained by all ultrasonic liquid level sensors based on the evaluation results. By calculating the oil level height in the conservator through the weighted processing results, compared with directly using the acoustic wave transmission time obtained by the ultrasonic liquid level sensor in the existing method to calculate the oil level height in the transformer conservator, it can effectively reduce the influence of the impurities in the conservator on the measurement result of the oil level height, and improve the accuracy of the measurement result of the oil level height in the transformer conservator. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a flowchart of the steps of a method for measuring the oil level of a transformer conservator provided by an embodiment of the present application; Figure 2 It is a schematic diagram of the acquisition process of the characteristic factor; Figure 3 It is a schematic diagram of the acquisition process of the impurity interference degree. Detailed Embodiments

[0017] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example", etc. are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary", "or", "for example", etc. is intended to present relevant concepts in a specific manner.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. It should be understood that unless otherwise stated in this application, " / " means "or".

[0019] In addition, it should be noted that the terms "first" and "second" in this application are used to distinguish similar objects and are not used to describe a specific order or sequence.

[0020] The following specifically describes the specific solutions of a transformer conservator oil level measurement method, device and system provided by this application with reference to the accompanying drawings.

[0021] Please refer to Figure 1 , which shows a step flow chart of a transformer conservator oil level measurement method provided by an embodiment of this application. The method includes the following steps: Step S1, collect the high-frequency pulsed acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and obtain the initial acoustic wave transmission time of each high-frequency pulsed acoustic wave signal.

[0022] A preset number of ultrasonic liquid level sensors are evenly installed at the bottom of the transformer conservator to avoid mutual interference between the ultrasonic liquid level sensors. When installing the ultrasonic liquid level sensors, a coupling agent is applied between the contact surfaces of the ultrasonic liquid level sensors and the conservator to exclude the air existing on the contact surfaces and avoid forming a steel-air interface between the ultrasonic liquid level sensors and the conservator, which affects the propagation of ultrasonic waves.

[0023] In this embodiment, the value of the preset number is 4. The value of the preset number is preset manually, and the implementer can set it according to the actual situation. This application does not make special restrictions.

[0024] The ultrasonic transducer of the ultrasonic liquid level sensor sends high-frequency pulsed acoustic signals into the conservator of the transformer, and the ultrasonic transducer of the ultrasonic liquid level sensor receives the echo signals. Among them, the ultrasonic transducers of all ultrasonic liquid level sensors use the same voltage amplitude and frequency to ensure that all ultrasonic liquid level sensors send the same high-frequency pulsed acoustic signals. The time interval between the high-frequency pulsed acoustic signals sent by each ultrasonic liquid level sensor and the received echo signals is obtained as the initial acoustic wave transmission time of the high-frequency pulsed acoustic signals sent by each ultrasonic liquid level sensor.

[0025] Step S2: By analyzing the high-frequency pulsed acoustic signals sent by each ultrasonic liquid level sensor and the received echo signals, the impurity interference degrees of each ultrasonic liquid level sensor are obtained.

[0026] When the high-frequency pulsed acoustic signals propagate in the conservator of the transformer and encounter impurities such as metal particles, bubbles, and sediments in the oil, the impurities will affect the propagation path of the ultrasonic waves, and then cause a deviation in the transmission time of the ultrasonic waves at this time compared with the transmission time when there are no impurities in the oil. The reason is that the acoustic impedance of the metal particles is quite different from that of the liquid, resulting in strong reflection of the ultrasonic waves on the surface of the metal particles, and the metal particles will scatter the ultrasonic waves, causing part of the ultrasonic wave energy to deviate from the original propagation path; the sediments may form an inhomogeneous medium, resulting in a change in the propagation path of the ultrasonic waves; the acoustic impedance of the bubbles is quite different from that of the liquid, resulting in strong reflection of the ultrasonic waves on the surface of the bubbles, and since the propagation speed of the ultrasonic waves in the gas is much lower than that in the liquid, the bubbles will significantly reduce the effective sound speed of the liquid.

[0027] Based on the above analysis, in this embodiment, by evaluating the degree of impurity interference received by the echo signals of each ultrasonic liquid level sensor, weighted average processing is performed on the initial acoustic wave transmission times of the high-frequency pulsed acoustic signals sent by all ultrasonic liquid level sensors, and the processing result is used as the final acoustic wave transmission time, and then the oil level height is calculated to reduce the influence of the impurities in the conservator on the measurement result of the oil level height.

[0028] Step S2.1: Obtain the intrinsic mode functions of each echo signal. By analyzing the correlation in the time domain and the similarity of the frequency distribution in the frequency domain between each intrinsic mode function and all high-frequency pulsed acoustic signals, the characteristic factors of each intrinsic mode function are obtained; through the distribution of the characteristic factors of all the intrinsic mode functions of each echo signal, the denoised echo signals of each echo signal are reconstructed.

[0029] The noise interference in the substation is very serious, so that a large amount of electronic noise and irrelevant clutter signals are mixed in the echo signal received by the ultrasonic liquid level sensor. Since the existing signal denoising algorithms can usually only filter out the random noise in the signal, the electronic noise and irrelevant clutter signals in the echo signal cannot be effectively filtered out by the existing signal denoising algorithms. In order to reduce the influence of the electronic noise and irrelevant clutter signals on the subsequent evaluation of the degree of impurity interference of the echo signal, the following processing is carried out.

[0030] Since the echo signal is the echo formed by the high-frequency pulse acoustic wave signal after multiple reflections in the conservator, the characteristics such as the time delay and amplitude attenuation of the echo signal are closely related to the high-frequency pulse acoustic wave signal. Therefore, the echo signal received by the ultrasonic liquid level sensor has a strong correlation with the high-frequency pulse acoustic wave signal it sends. And during the transmission of ultrasonic waves, although the ultrasonic waves will attenuate due to reflection and absorption, the basic frequency components of the ultrasonic waves will not change, making the echo signal have a similar frequency distribution to the high-frequency pulse acoustic wave signal. However, the electronic noise and irrelevant clutter signals in the echo signal usually do not have the above-mentioned correlation and similarity with the high-frequency pulse acoustic wave signal.

[0031] Based on the above analysis, taking the echo signal A(i) received by the i-th ultrasonic liquid level sensor as an example, the signal decomposition algorithm is used to decompose the echo signal A(i) into each intrinsic mode function, and each intrinsic mode function corresponds to a certain frequency band of the echo signal A(i).

[0032] In this embodiment, the complete ensemble empirical mode decomposition and adaptive noise signal decomposition algorithm is used to decompose the echo signal A(i) into each intrinsic mode function. The complete ensemble empirical mode decomposition and adaptive noise signal decomposition algorithm is a well-known technology and will not be elaborated in this application. As other implementation manners, on the basis of being able to decompose the echo signal A(i) into each intrinsic mode function, the implementer can adopt other existing technologies, such as the empirical mode decomposition (EMD) algorithm, the ensemble empirical mode decomposition (EEMD) algorithm, etc. This application does not make special restrictions.

[0033] The coherent averaging method is used to process the high-frequency pulse acoustic wave signals sent by all ultrasonic liquid level sensors to obtain the average time-domain signal of all high-frequency pulse acoustic wave signals, so as to reduce the noise interference suffered by the high-frequency pulse acoustic wave signals during the transmission process. Among them, the coherent averaging method is a well-known technology and will not be elaborated in this application.

[0034] Taking the j-th intrinsic mode function A(i,j) of the echo signal A(i) as an example, the correlation coefficient between the intrinsic mode function A(i,j) and the average time-domain signal is calculated to characterize the correlation degree between the signal component of the echo signal A(i) corresponding to the intrinsic mode function A(i,j) and the high-frequency pulsed acoustic wave signal.

[0035] In this embodiment, the correlation coefficient between the intrinsic mode function A(i,j) and the average time-domain signal is the Pearson correlation coefficient. As other implementation manners, on the basis of being able to measure the correlation degree between the intrinsic mode function A(i,j) and the average time-domain signal, the implementer can use other existing technologies for measurement, such as the Spearman correlation coefficient, etc. This application does not make special restrictions.

[0036] The spectra of the intrinsic mode function A(i,j) and the average time-domain signal are respectively obtained by using Fourier transform, and the spectral similarity between the spectrum of the intrinsic mode function A(i,j) and the spectrum of the average time-domain signal is calculated to characterize the similarity degree of the signal frequency distribution between the signal component of the echo signal A(i) corresponding to the intrinsic mode function A(i,j) and the high-frequency pulsed acoustic wave signal. Among them, the acquisition of the spectrum is a well-known technology and will not be elaborated in this application.

[0037] In this embodiment, the spectral similarity is the cosine similarity. As other implementation manners, on the basis of being able to measure the similarity between the spectrum of the intrinsic mode function A(i,j) and the spectrum of the average time-domain signal, the implementer can use other existing technologies for measurement, such as the Pearson correlation coefficient, etc. This application does not make special restrictions.

[0038] The product of the correlation coefficient and the spectral similarity is used as the characteristic factor of the intrinsic mode function A(i,j) to characterize the possibility that the intrinsic mode function A(i,j) is the echo signal component in the echo signal A(i). The schematic diagram of the acquisition process of the characteristic factor is as Figure 2 shown.

[0039] According to the same acquisition method as the characteristic factor of the intrinsic mode function A(i,j), the characteristic factors of each intrinsic mode function of the echo signal A(i) are obtained.

[0040] The segmentation threshold of the characteristic factors of all the intrinsic mode functions of the echo signal A(i) is obtained by using the threshold segmentation algorithm, and all the intrinsic mode functions greater than the segmentation threshold are reconstructed to obtain the denoised echo signal C(i) of the echo signal A(i). Thus, the filtering of the random noise and irrelevant clutter signals in the echo signal A(i) is completed.

[0041] Using the same acquisition method as the denoised echo signal C(i) of the echo signal A(i), the denoised echo signals of the remaining echo signals are obtained.

[0042] Step S2.2: Use an endpoint detection algorithm to obtain each echo signal segment of each denoised echo signal. By comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distributions of the echo signal segments of the remaining denoised echo signals, obtain each reference echo signal segment of the said echo signal segment. By analyzing the differences in the complexity of the signal distributions and the amplitude differences between each echo signal segment and its corresponding reference echo signal segments, obtain the impurity interference coefficients of each echo signal segment. Based on the distributions of the impurity interference coefficients of all the echo signal segments corresponding to each ultrasonic level sensor, obtain the impurity interference degrees of each ultrasonic level sensor.

[0043] Since the amplitude of the echo signal component in the echo signal received by the ultrasonic level sensor is usually higher than the background noise, the endpoint detection algorithm is used to extract each audible segment signal in each denoised echo signal as each echo signal segment of each denoised echo signal.

[0044] In this embodiment, an endpoint detection algorithm based on double thresholds is used to extract each audible segment signal in each denoised echo signal. The endpoint detection algorithm based on double thresholds is a well-known technology and will not be elaborated in this application. As other implementation manners, on the basis of being able to extract each audible segment signal in each denoised echo signal, the implementer can adopt other existing technologies, such as an endpoint detection algorithm based on the maximum of autocorrelation, an endpoint detection algorithm based on the variance of frequency bands, etc. This application does not make special restrictions.

[0045] Furthermore, since all ultrasonic level sensors measure the oil level of the same transformer conservator and the ultrasonic transducers of all ultrasonic level sensors use the same voltage amplitude and frequency, when the high-frequency pulsed acoustic wave signals sent by all ultrasonic level sensors propagate, acoustic wave reflections will occur within the same time range, resulting in the same number of reflected echoes, that is, the same number of echo signals will appear in the echo signals received by all ultrasonic level sensors, and the echo signals generated within the same time range will reach the ultrasonic level sensors within a similar time.

[0046] Take the moment when the sampling point with the largest amplitude in each echo signal segment is located as the echo arrival moment of each echo signal segment, which is used to represent the moment when each echo signal segment reaches the ultrasonic level sensor.

[0047] Taking the k-th echo signal segment C(i,k) of the denoised echo signal C(i) as an example, from each denoised echo signal other than the denoised echo signal C(i), the echo signal segments with the shortest time interval of echo arrival time between them and the echo signal segment C(i,k) are respectively selected. The selected echo signal segments are used as the respective reference echo signal segments of the echo signal segment C(i,k) to represent the echo signal segments generated within the same time range as the echo signal segment C(i,k) in the remaining denoised echo signals.

[0048] When the high-frequency pulsed acoustic wave signal encounters impurities during its propagation in the conservator of the transformer, the impurities cause multiple reflections and refractions of the ultrasonic wave, forming multipath reflection signals. The multipath reflection signals are superimposed on the direct reflection signal, further interfering with the echo waveform, resulting in a more complex and chaotic reflected echo. Moreover, the impurities will absorb part of the ultrasonic wave energy, causing the amplitude of the reflected echo to decay. Therefore, if the high-frequency pulsed acoustic wave signal sent by any one ultrasonic level sensor encounters impurities during transmission, compared with the reflected echoes formed by the high-frequency pulsed acoustic wave signals sent by other ultrasonic level sensors within the same time range, the reflected echo formed by the high-frequency pulsed acoustic wave signal sent by any one ultrasonic level sensor has a smaller echo signal amplitude and a more complex and chaotic echo signal distribution characteristic.

[0049] Based on the above analysis, the entropy of each echo signal segment is calculated to represent the complexity of the signal distribution in each echo signal segment. Taking the echo signal segment C(i,k) as an example, the difference between the entropy of the echo signal segment C(i,k) and the entropies of its respective reference echo signal segments is calculated. The mean value of all the differences of the echo signal segment C(i,k) is denoted as the first difference mean. The larger the first difference mean, the more complex and chaotic the echo signal distribution characteristic of the echo signal segment C(i,k) compared with the echo signal segments formed within the same time range.

[0050] In this embodiment, the entropy of the echo signal segment is the fuzzy entropy. As other implementation manners, on the basis of being able to measure the complexity degree of the signal distribution in the echo signal segment, the implementer can use other existing technologies for measurement, such as approximate entropy, sample entropy, etc. This application does not make special restrictions.

[0051] The average value of the amplitudes of all sampling points in each echo signal segment is used as the signal amplitude of each echo signal segment. The difference between the signal amplitude of the echo signal segment C(i,k) and the signal amplitudes of its respective reference echo signal segments is denoted as the amplitude difference. The mean value of all the amplitude differences of the echo signal segment C(i,k) is denoted as the second difference mean. The larger the second difference mean, the larger the echo signal amplitude of the echo signal segment C(i,k) compared with the echo signal segments formed within the same time range.

[0052] Map the second difference mean value of the echo signal segment C(i,k) to a positive number, and use the ratio of the first difference mean value of the echo signal segment C(i,k) to the positive number as the impurity interference coefficient of the echo signal segment C(i,k), which is used to characterize the degree of impurity interference of the echo signal segment C(i,k) in the transformer conservator compared with the echo signal segments formed within the same time range. Take the mean value of the impurity interference coefficients of all echo signal segments of the denoised echo signal C(i) as the impurity interference degree of the i-th ultrasonic level sensor, which is used to evaluate the degree of impurity interference of the echo signal received by the i-th ultrasonic level sensor in the transformer conservator. The greater the impurity interference degree, the lower the credibility of the initial acoustic transmission time measured by the i-th ultrasonic level sensor. Therefore, when performing weighted average processing on all initial acoustic transmission times subsequently, the weight of the initial acoustic transmission time of the i-th ultrasonic level sensor should be smaller. Among them, the purpose of mapping the second difference mean value to a positive number is to avoid a denominator of 0. There are many ways to map data to positive numbers, and this application does not make special restrictions on this. In this embodiment, by taking the second difference mean value as the exponent of an exponential function with the natural constant as the base, the purpose of mapping the second difference mean value to a positive number is achieved. The schematic diagram of the acquisition process of the impurity interference degree is as Figure 3 shown.

[0053] Use the same calculation method as the impurity interference degree of the i-th ultrasonic level sensor to calculate the impurity interference degrees of the other ultrasonic level sensors.

[0054] Step S3, calculate the oil level height in the conservator through the impurity interference degree and the initial acoustic transmission time.

[0055] Perform weighted fusion on the initial acoustic transmission times of the high-frequency pulsed acoustic signals sent by all ultrasonic level sensors through the impurity interference degrees of each ultrasonic level sensor to obtain the comprehensive acoustic transmission time of all high-frequency pulsed acoustic signals. The expression is: ; In the formula, T represents the comprehensive acoustic transmission time of all high-frequency pulsed acoustic signals; M represents the number of ultrasonic level sensors; map the impurity interference degrees of each ultrasonic level sensor to positive numbers, denoted as mapped positive numbers, and S(i) represents the normalized value of the reciprocal of the mapped positive number of the i-th ultrasonic level sensor; t(i) represents the initial acoustic transmission time of the high-frequency pulsed acoustic signal sent by the i-th ultrasonic level sensor. Among them, the purpose of mapping the impurity interference degree to a positive number is to avoid a denominator of 0. There are many ways to map data to positive numbers, and this application does not make special restrictions on this. In this embodiment, by taking the impurity interference degree as the exponent of an exponential function with the natural constant as the base, the purpose of mapping the second difference mean value to a positive number is achieved.

[0056] In this embodiment, the Softmax function is used to obtain the normalized value of the reciprocal.

[0057] Based on the comprehensive acoustic wave transmission time, the oil level height in the conservator is calculated. The calculation formula for the oil level height is a well-known technology and will not be elaborated in this application.

[0058] Based on the same inventive concept as the above method, an embodiment of the present application further provides a transformer conservator oil level measuring device, including: A signal acquisition module, configured to acquire the high-frequency pulsed acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and obtain the initial acoustic wave transmission time of each high-frequency pulsed acoustic wave signal; A signal analysis module, configured to obtain each intrinsic mode function of each echo signal, and obtain the characteristic factor of each intrinsic mode function by analyzing the correlation in the time domain and the similarity of the frequency distribution in the frequency domain between each intrinsic mode function and all high-frequency pulsed acoustic wave signals; reconstruct the denoised echo signals of each echo signal through the distribution of the characteristic factors of all the intrinsic mode functions of each echo signal; Use the endpoint detection algorithm to obtain each echo signal segment of each denoised echo signal, and obtain each reference echo signal segment of the any echo signal segment by comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distributions of each echo signal segment of the remaining denoised echo signals; Obtain the impurity interference coefficient of each echo signal segment by analyzing the difference in the complexity of the signal distribution and the amplitude difference between each echo signal segment and its each reference echo signal segment; Obtain the impurity interference degree of each ultrasonic liquid level sensor through the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor; An oil level calculation module, configured to calculate the oil level height in the conservator through the impurity interference degree and the initial acoustic wave transmission time.

[0059] Based on the same inventive concept as the above method, an embodiment of the present application further provides a transformer conservator oil level measuring system, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above methods for measuring the oil level of a transformer conservator are implemented.

[0060] In summary, by analyzing the correlation in the time domain and the similarity in the frequency domain between the intrinsic mode functions of the echo signals and the high-frequency pulsed acoustic wave signals, the present application calculates the characteristic factors of the intrinsic mode functions of the wave echo signals to implement the preprocessing of the echo signals. Compared with directly using the existing signal denoising algorithms, it can effectively filter out the noise and irrelevant clutter signals in the echo signals received by each ultrasonic liquid level sensor, and reduce the influence of the noise and irrelevant clutter signals on the subsequent evaluation of the degree of impurity interference of the echo signals. The present application evaluates the degree of impurity interference of the echo signals received by each ultrasonic liquid level sensor in the transformer conservator by analyzing the amplitude difference between the echo signal segments generated within the same time range and the complexity difference of the signal distribution, and performs weighted processing on the initial acoustic wave transmission times obtained from all ultrasonic liquid level sensors based on the evaluation results. By calculating the oil level height in the conservator using the weighted processing results, compared with directly using the acoustic wave transmission times obtained from ultrasonic liquid level sensors in the existing method to calculate the oil level height in the transformer conservator, it can effectively reduce the influence of the impurities in the conservator on the measurement result of the oil level height and improve the accuracy of the measurement result of the oil level height in the transformer conservator.

[0061] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different blocks may also occur in a different order than disclosed in the descriptions. Sometimes, there is no specific order between different operations or steps. For example, two consecutive operations or steps may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. Each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0062] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the basic features of the present application. Therefore, from any point of view, the above embodiments of the present application should be regarded as exemplary and non-limiting.

Claims

1. A method for measuring the oil level of a transformer oil storage tank, characterized in that: The method comprises the following steps: Collect the high-frequency pulse sound wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and obtain the initial sound wave transmission time of each high-frequency pulse sound wave signal; Obtain each intrinsic mode function of each echo signal, and obtain the characteristic factor of each intrinsic mode function by analyzing the correlation between each intrinsic mode function and all high-frequency pulse sound wave signals in the time domain and the similarity of frequency distribution in the frequency domain; reconstruct the denoised echo signal of each echo signal through the characteristic factor distribution of all intrinsic mode functions of each echo signal; Acquire each echo signal segment of each denoised echo signal by using an endpoint detection algorithm, and acquire each reference echo signal segment of any echo signal segment by comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distribution of each echo signal segment of the remaining denoised echo signals; By analyzing the difference in signal distribution complexity and amplitude between each echo signal segment and its control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained; Obtain the impurity interference degree of each ultrasonic liquid level sensor through the distribution of impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor; The oil level in the oil storage tank is calculated according to the impurity interference degree and the initial sound wave transmission time.

2. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The process of obtaining the characteristic factor is as follows: The coherent averaging method is used to obtain the average time domain signal of all high-frequency pulse sound wave signals; Calculate the correlation coefficient between each intrinsic mode function and the average time domain signal; The frequency spectrum of each intrinsic mode function and the average time domain signal is obtained by Fourier transform, and the frequency spectrum similarity between the frequency spectrum of each intrinsic mode function and the frequency spectrum of the average time domain signal is calculated; The product of the correlation coefficient and the frequency spectrum similarity is used as a characteristic factor of each eigenmode function.

3. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The acquisition process of the denoised echo signal is as follows: A threshold segmentation algorithm is used to obtain a segmentation threshold of characteristic factors of all intrinsic mode functions of any echo signal; all intrinsic mode functions greater than the segmentation threshold are reconstructed to obtain a denoised echo signal of the any echo signal.

4. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The acquisition process of the control echo signal segment is as follows: The time at which the sampling point with the largest amplitude in each echo signal segment is located is taken as the echo arrival time of each echo signal segment; From each denoised echo signal except the any denoised echo signal, the echo signal segments with the shortest time interval between the echo arrival time and the any echo signal segment are selected as the reference echo signal segments of the any echo signal segment.

5. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The process of obtaining the impurity interference coefficient is as follows: Calculate the entropy of each echo signal segment; take the average value of the amplitudes of all sampling points in each echo signal segment as the signal amplitude of each echo signal segment; Calculate the difference between the entropy of each echo signal segment and the entropy of each control echo signal segment; Recording the mean of all the differences of each echo signal segment as the first difference mean; The difference in signal amplitude between each echo signal segment and each control echo signal segment is recorded as the amplitude difference; the mean of all the amplitude differences of each echo signal segment is recorded as the second difference mean; The impurity interference coefficient of each echo signal segment is obtained by combining the first difference mean and the second difference mean.

6. A transformer oil conservator oil level measurement method as claimed in claim 5, characterized in that: The calculation process of the impurity interference coefficient is: mapping the second difference mean to a positive number, and taking the ratio of the first difference mean to the positive number as the impurity interference coefficient of each echo signal segment.

7. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The impurity interference degree is the average value of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor.

8. A transformer oil conservator oil level measurement method as claimed in claim 1, characterized in that: The step of calculating the oil level in the oil storage tank comprises: The comprehensive sound wave transmission time of all high-frequency pulse sound wave signals is calculated by the impurity interference degree and the initial sound wave transmission time, and the expression is: ; Wherein, T represents the comprehensive sound wave transmission time of all high-frequency pulse sound wave signals; M represents the number of ultrasonic liquid level sensors; the impurity interference degree of each ultrasonic liquid level sensor is mapped to a positive number, recorded as the mapped positive number, S(i) represents the normalized value of the reciprocal of the mapped positive number of the i-th ultrasonic liquid level sensor; t(i) represents the initial sound wave transmission time of the high-frequency pulse sound wave signal sent by the i-th ultrasonic liquid level sensor; The oil level in the oil storage tank is calculated by the integrated sound wave transmission time.

9. A transformer oil storage tank oil level measuring device, characterized in that: The device comprises: The signal acquisition module is used to collect the high-frequency pulse sound wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and obtain the initial sound wave transmission time of each high-frequency pulse sound wave signal; The signal analysis module is used to obtain each intrinsic mode function of each echo signal, and obtain the characteristic factor of each intrinsic mode function by analyzing the correlation between each intrinsic mode function and all high-frequency pulse sound wave signals in the time domain and the similarity of frequency distribution in the frequency domain; and reconstruct the denoised echo signal of each echo signal through the characteristic factor distribution of all intrinsic mode functions of each echo signal; Acquire each echo signal segment of each denoised echo signal by using an endpoint detection algorithm, and acquire each reference echo signal segment of any echo signal segment by comparing the amplitude distribution of any echo signal segment of any denoised echo signal with the amplitude distribution of each echo signal segment of the remaining denoised echo signals; By analyzing the difference in signal distribution complexity and amplitude between each echo signal segment and its control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained; Obtain the impurity interference degree of each ultrasonic liquid level sensor through the distribution of impurity interference coefficients of all echo signal segments corresponding to each ultrasonic liquid level sensor; The oil level calculation module is used to calculate the oil level height in the oil storage tank according to the impurity interference degree and the initial sound wave transmission time.

10. A transformer oil conservator oil level measurement system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method for measuring the oil level of a transformer oil conservator as claimed in any one of claims 1 to 8 are implemented.

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