A method, device and system for measuring oil level in a transformer oil conservator.

Abstract

This application relates to the field of oil level measurement technology, specifically to a method, device, and system for measuring the oil level in a transformer oil conservator. The method includes: acquiring high-frequency pulse acoustic signals transmitted by each ultrasonic level sensor and receiving echo signals; obtaining the initial acoustic transmission time of each high-frequency pulse acoustic signal; obtaining the characteristic factors of each intrinsic mode function (EMF) of each echo signal; reconstructing denoised echo signals of each echo signal based on the distribution of the characteristic factors of all EMFs of each echo signal; obtaining each echo signal segment and the impurity interference coefficient of each echo signal segment; obtaining the impurity interference degree of each ultrasonic level sensor; and calculating the oil level height in the oil conservator. This application aims to improve the accuracy of the oil level height measurement result in the oil conservator by improving the measurement accuracy of the transmission time of the high-frequency pulse acoustic signal.

Description

Technical Field

[0001] This application relates to the field of oil level measurement technology, specifically to a method, device, and system for measuring the oil level in a transformer oil conservator. Background Technology

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

[0003] Currently, ultrasonic measurement methods are commonly used to measure the oil level in transformer oil conservators. However, due to the influence of ambient temperature and humidity during use, transformer oil conservators often contain impurities such as metal particles, sediments, and bubbles. Existing ultrasonic measurement methods ignore the interference of these impurities on ultrasonic wave propagation, resulting in inaccurate ultrasonic wave transmission time. Consequently, the measured oil level in the oil conservator deviates from the actual oil level. 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 in a transformer oil conservator. Compared with traditional oil level measurement methods, this method improves the accuracy of the oil level measurement result by increasing the measurement accuracy of the transmission time of the high-frequency pulse acoustic signal.

[0005] In a first aspect, embodiments of this application provide a method for measuring the oil level in a transformer oil conservator, the method comprising the following steps:

[0006] Collect the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal.

[0007] The intrinsic mode functions (EMFs) of each echo signal are obtained. By analyzing the correlation between each EMF and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, the characteristic factors of each EMF are obtained. The denoised echo signals of each echo signal are reconstructed by the distribution of the characteristic factors of all EMFs of each echo signal.

[0008] The endpoint detection algorithm is used 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 distribution of each echo signal segment of the other denoised echo signals, the corresponding echo signal segments of the given echo signal segment are obtained.

[0009] By analyzing the differences in signal distribution complexity and amplitude between each echo signal segment and its corresponding control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained.

[0010] The impurity interference degree of each ultrasonic level sensor is obtained by analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor.

[0011] The oil level in the tank is calculated using the impurity interference level and the initial sound wave transmission time.

[0012] In one embodiment, the process of obtaining the feature factors is as follows:

[0013] The average time-domain signal of all high-frequency pulse acoustic signals was obtained using the coherent averaging method.

[0014] Calculate the correlation coefficients between each intrinsic mode function and the average time-domain signal;

[0015] The spectra of each intrinsic mode function and the average time domain signal are obtained by using Fourier transform, and the spectral similarity between the spectra of each intrinsic mode function and the spectrum of the average time domain signal is calculated.

[0016] The product of the correlation coefficient and the spectral similarity is used as the characteristic factor of each intrinsic mode function.

[0017] In one embodiment, the process of acquiring the denoised echo signal is as follows:

[0018] A threshold segmentation algorithm is used to obtain the segmentation threshold of the characteristic factors of all intrinsic mode functions of any echo signal; all intrinsic mode functions greater than the segmentation threshold are reconstructed to obtain the denoised echo signal of the given echo signal.

[0019] In one embodiment, the process of acquiring the reference echo signal segment is as follows:

[0020] The time of the sampling point with the largest amplitude in each echo signal segment is taken as the echo arrival time of each echo signal segment.

[0021] From all the denoised echo signals other than the aforementioned denoised echo signal, select the echo signal segment with the shortest time interval between the echo arrival time and the aforementioned echo signal segment, and use it as the reference echo signal segment for the aforementioned echo signal segment.

[0022] In one embodiment, the process of obtaining the impurity interference coefficient is as follows:

[0023] Calculate the entropy of each echo signal segment; take the average amplitude of all sampling points in each echo signal segment as the signal amplitude of each echo signal segment;

[0024] Calculate the difference between the entropy of each echo signal segment and the entropy of each corresponding echo signal segment;

[0025] The average of all the differences in each echo signal segment is denoted as the first difference average.

[0026] The difference in signal amplitude between each echo signal segment and its corresponding reference echo signal segment is denoted as amplitude difference; the mean of all amplitude differences for each echo signal segment is denoted as second difference mean.

[0027] By combining the first average difference and the second average difference, the impurity interference coefficient of each echo signal segment is obtained.

[0028] In one embodiment, the impurity interference coefficient is calculated as follows: the mean of the second difference is mapped to a positive number, and the ratio of the mean of the first difference to the positive number is used as the impurity interference coefficient of each echo signal segment.

[0029] In one embodiment, the impurity interference degree is the average of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor.

[0030] In one embodiment, calculating the oil level in the oil tank includes:

[0031] The combined acoustic wave propagation time of all high-frequency pulse acoustic wave signals is calculated using the impurity interference level and the initial acoustic wave propagation time, expressed as:

[0032] In the formula, T represents the combined acoustic wave transmission time of all high-frequency pulse acoustic wave signals; M represents the number of ultrasonic level sensors; the impurity interference degree of each ultrasonic level sensor is mapped 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 level sensor; t(i) represents the initial acoustic wave transmission time of the high-frequency pulse acoustic wave signal sent by the i-th ultrasonic level sensor.

[0033] The oil level in the tank is calculated using the combined sound wave transmission time.

[0034] Secondly, embodiments of this application also provide a transformer oil conservator oil level measuring device, the device comprising:

[0035] The signal acquisition module is used to acquire the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal.

[0036] The signal analysis module is used to obtain the intrinsic mode functions (EMFs) of each echo signal. By analyzing the correlation between each EMF and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, the characteristic factors of each EMF are obtained. Based on the distribution of the characteristic factors of all EMFs of each echo signal, the denoised echo signal of each echo signal is reconstructed.

[0037] The endpoint detection algorithm is used 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 distribution of each echo signal segment of the other denoised echo signals, the corresponding echo signal segments of the given echo signal segment are obtained.

[0038] By analyzing the differences in signal distribution complexity and amplitude between each echo signal segment and its corresponding control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained.

[0039] The impurity interference degree of each ultrasonic level sensor is obtained by analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor.

[0040] The oil level calculation module is used to calculate the oil level height in the oil tank by using the impurity interference degree and the initial sound wave transmission time.

[0041] Thirdly, embodiments of this application also provide a transformer oil conservator oil level measurement 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, it implements the steps of any of the above-described transformer oil conservator oil level measurement methods.

[0042] This application has at least the following beneficial effects:

[0043] This application preprocesses the echo signal 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 pulse acoustic signal, and calculating the characteristic factor of the intrinsic mode function of the echo signal. Compared with the direct use of existing signal denoising algorithms, it can effectively filter out noise and irrelevant clutter signals in the echo signal received by each ultrasonic level sensor, and reduce the influence of noise and irrelevant clutter signals on the subsequent evaluation of the degree of interference of the echo signal by impurities.

[0044] This application evaluates the degree of interference from impurities in the transformer oil conservator by analyzing the amplitude differences and signal distribution complexity differences between echo signal segments generated within the same time range. Based on the evaluation results, the initial acoustic wave transmission time obtained by all ultrasonic level sensors is weighted, and the oil level height in the oil conservator is calculated using the weighted processing result. Compared with the existing method of directly using the acoustic wave transmission time obtained by the ultrasonic level sensor to calculate the oil level height in the transformer oil conservator, this method can effectively reduce the influence of impurities in the oil conservator on the oil level measurement results and improve the accuracy of the oil level measurement results in the transformer oil conservator. Attached Figure Description

[0045] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 A flowchart illustrating the steps of a transformer oil conservator oil level measurement method according to one embodiment of this application;

[0047] Figure 2 This is a schematic diagram of the process for obtaining feature factors;

[0048] Figure 3 This is a schematic diagram of the process for obtaining the degree of impurity interference. Detailed Implementation

[0049] In the description of the embodiments in this application, the words "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary," "or," and "for example" is intended to present the relevant concepts in a specific manner.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It should be understood that, unless otherwise stated, " / " in this application means "or".

[0051] It should also be noted that the terms "first" and "second" in this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0052] The following description, in conjunction with the accompanying drawings, details the specific scheme of the transformer oil level measurement method, device, and system provided in this application.

[0053] Please see Figure 1 The diagram illustrates a flowchart of a method for measuring the oil level in a transformer oil conservator according to an embodiment of this application. The method includes the following steps:

[0054] Step S1: Collect the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal.

[0055] A predetermined number of ultrasonic level sensors are evenly installed at the bottom of the transformer oil conservator to avoid mutual interference between the ultrasonic level sensors. When installing the ultrasonic level sensors, a coupling agent is applied between the contact surfaces of the ultrasonic level sensors and the oil conservator to remove air from the contact surfaces and prevent the formation of a steel-air interface between the ultrasonic level sensors and the oil conservator, which would affect the propagation of ultrasonic waves.

[0056] In this embodiment, the preset quantity is 4. The preset quantity is preset by a person and the implementer can set it according to the actual situation. This application does not impose any special restrictions.

[0057] The ultrasonic transducer of the ultrasonic level sensor sends a high-frequency pulsed acoustic signal into the transformer oil tank, and receives the echo signal through its own ultrasonic transducer. All ultrasonic level sensors use the same voltage amplitude and frequency to ensure that they all send the same high-frequency pulsed acoustic signal. The time interval between the transmission of the high-frequency pulsed acoustic signal and the receipt of the echo signal by each ultrasonic level sensor is used as the initial acoustic transmission time of the high-frequency pulsed acoustic signal sent by each sensor.

[0058] Step S2: By analyzing the high-frequency pulse acoustic wave signals sent by each ultrasonic level sensor and the received echo signals, the impurity interference degree of each ultrasonic level sensor is obtained.

[0059] When a high-frequency pulsed acoustic signal propagates within the transformer's oil conservator, it encounters impurities such as metal particles, bubbles, and sediments in the oil. These impurities affect the propagation path of the ultrasound waves, causing a deviation in the transmission time compared to when the oil is free of impurities. This is because the acoustic impedance of metal particles differs significantly from that of the liquid, resulting in strong reflections of the ultrasound waves on the surface of the metal particles. Furthermore, the metal particles scatter the ultrasound waves, causing some of the ultrasound energy to deviate from the original propagation path. Sediments may form a non-uniform medium, altering the propagation path of the ultrasound waves. The acoustic impedance of bubbles differs significantly from that of the liquid, causing strong reflections of the ultrasound waves on the surface of the bubbles. Additionally, since the speed of ultrasound propagation in gases is much lower than in liquids, bubbles significantly reduce the effective speed of sound in the liquid.

[0060] Based on the above analysis, this embodiment evaluates the degree of interference from impurities on the echo signal received by each ultrasonic level sensor, performs weighted averaging on the initial acoustic transmission time of the high-frequency pulse acoustic signals sent by all ultrasonic level sensors, and uses the processing result as the final acoustic transmission time to calculate the oil level height, thereby reducing the impact of impurities in the oil tank on the oil level height measurement results.

[0061] Step S2.1: Obtain the intrinsic mode functions of each echo signal. By analyzing the correlation between each intrinsic mode function and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, obtain the characteristic factors of each intrinsic mode function. Reconstruct the denoised echo signal of each echo signal by analyzing the characteristic factor distribution of all intrinsic mode functions of each echo signal.

[0062] The substation experiences severe noise interference, resulting in a significant amount of electronic noise and irrelevant clutter in the echo signals received by the ultrasonic level sensor. Since existing signal denoising algorithms typically only filter out random noise, they are ineffective at removing electronic noise and irrelevant clutter from the echo signals. To reduce the impact of electronic noise and irrelevant clutter on the subsequent evaluation of the degree of interference with the echo signals, the following processing is performed.

[0063] Since the echo signal is formed by multiple reflections of a high-frequency pulsed sound wave signal within the oil tank, its time delay, amplitude attenuation, and other characteristics are closely related to those of the high-frequency pulsed sound wave signal. Therefore, the echo signal received by the ultrasonic level sensor has a strong correlation with the high-frequency pulsed sound wave signal it transmits. Furthermore, although the ultrasonic wave attenuates due to reflection and absorption during transmission, its fundamental frequency components remain unchanged, resulting in a similar frequency distribution between the echo signal and the high-frequency pulsed sound wave signal. In contrast, electronic noise and irrelevant clutter in the echo signal typically do not exhibit the aforementioned correlation and similarity with the high-frequency pulsed sound wave signal.

[0064] Based on the above analysis, taking the echo signal A(i) received by the i-th ultrasonic level sensor as an example, the echo signal A(i) is decomposed into each intrinsic mode function using a signal decomposition algorithm. Each intrinsic mode function corresponds to a certain frequency band of the echo signal A(i).

[0065] In this embodiment, the echo signal A(i) is decomposed into eigenmode functions using a fully integrated empirical mode decomposition and adaptive noise decomposition algorithm. The fully integrated empirical mode decomposition and adaptive noise decomposition algorithm are well-known technologies and will not be described in detail here. As other implementation methods, based on the ability to decompose the echo signal A(i) into eigenmode functions, implementers may use other existing technologies, such as empirical mode decomposition (EMD) algorithm, ensemble empirical mode decomposition (EEMD) algorithm, etc. This application does not impose any special restrictions.

[0066] The high-frequency pulse acoustic wave signals sent by all ultrasonic level sensors are processed by the coherent averaging method to obtain the average time domain signal of all high-frequency pulse acoustic wave signals, so as to reduce the noise interference of high-frequency pulse acoustic wave signals during transmission. The coherent averaging method is a known technology and will not be described in detail in this application.

[0067] 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 degree of correlation between the signal component of the echo signal A(i) corresponding to the intrinsic mode function A(i,j) and the high-frequency pulse acoustic signal.

[0068] 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 another implementation, based on the ability to measure the correlation between the intrinsic mode function A(i,j) and the average time-domain signal, the implementer may use other existing technologies for measurement, such as the Spearman correlation coefficient, etc. This application does not impose any special restrictions.

[0069] The spectra of the intrinsic mode function A(i,j) and the average time-domain signal are 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. This is used to characterize the similarity of the signal frequency distribution between the signal components of the echo signal A(i) corresponding to the intrinsic mode function A(i,j) and the high-frequency pulse acoustic wave signal. The acquisition of the spectrum is a well-known technique and will not be described in detail in this application.

[0070] In this embodiment, the spectral similarity is cosine similarity. As other implementation methods, based on the ability 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 may use other existing technologies for measurement, such as Pearson correlation coefficient, etc. This application does not impose any special restrictions.

[0071] The product of the correlation coefficient and the spectral similarity is used as a characteristic factor of the intrinsic mode function A(i,j), which characterizes the probability that the intrinsic mode function A(i,j) is an echo signal component in the echo signal A(i). A schematic diagram of the characteristic factor acquisition process is shown below. Figure 2 As shown.

[0072] The characteristic factors of each eigenmode function of the echo signal A(i) are obtained using the same method as those for the characteristic factors of the eigenmode function A(i,j).

[0073] A threshold segmentation algorithm is used to obtain the segmentation threshold of the characteristic factors of all intrinsic mode functions of the echo signal A(i). All 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 random noise and irrelevant clutter signals in the echo signal A(i) are filtered out.

[0074] The denoised echo signals of the other echo signals are obtained by using the same method as the denoised echo signal C(i) of echo signal A(i).

[0075] Step S2.2: Use the 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 distribution of each echo signal segment of the remaining denoised echo signals, obtain each reference echo signal segment of the given echo signal segment. By analyzing the differences in the complexity of the signal distribution and the amplitude differences between each echo signal segment and its reference echo signal segments, obtain the impurity interference coefficient of each echo signal segment. By analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor, obtain the impurity interference degree of each ultrasonic level sensor.

[0076] 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 the sound segment signal from each denoised echo signal as each echo signal segment of each denoised echo signal.

[0077] In this embodiment, a dual-threshold endpoint detection algorithm is used to extract the sound segment signals from each denoised echo signal. The dual-threshold endpoint detection algorithm is a well-known technology and will not be described in detail here. As other implementation methods, based on the ability to extract the sound segment signals from each denoised echo signal, the implementer may use other existing technologies, such as endpoint detection algorithms based on the maximum autocorrelation value or endpoint detection algorithms based on the frequency band variance. This application does not impose any special restrictions.

[0078] Furthermore, since all ultrasonic level sensors measure the oil level in the same transformer tank, and all ultrasonic level sensors use the same voltage amplitude and frequency for their ultrasonic transducers, the high-frequency pulse sound wave signals sent by all ultrasonic level sensors will be reflected within the same time range during propagation, thus generating the same number of reflected echoes. In other words, the echo signals received by all ultrasonic level sensors will have the same number of echoes, and the echo signals generated within the same time range will arrive at the ultrasonic level sensors in similar time intervals.

[0079] The time of the sampling point with the largest amplitude in each echo signal segment is taken as the echo arrival time of each echo signal segment, which is used to characterize the time when each echo signal segment arrives at the ultrasonic liquid level sensor.

[0080] Taking the k-th echo signal segment C(i,k) of the denoised echo signal C(i) as an example, from each of the denoised echo signals other than the denoised echo signal C(i), the echo signal segment with the shortest time interval between the echo arrival time and the echo signal segment C(i,k) is selected. Each selected echo signal segment is used as a reference echo signal segment of the echo signal segment C(i,k) to characterize the echo signal segments generated in the other denoised echo signals within the same time range as the echo signal segment C(i,k).

[0081] When a high-frequency pulsed acoustic signal encounters impurities during its propagation within the transformer's oil conservator, the impurities cause multiple reflections and refractions of the ultrasonic waves, forming multipath reflected signals. These multipath reflected signals superimpose with the direct reflected signals, further interfering with the echo waveform and resulting in a more complex and chaotic reflected echo. Furthermore, the impurities absorb some of the ultrasonic energy, causing an attenuation in the amplitude of the reflected echo. Therefore, if a high-frequency pulsed acoustic signal from any ultrasonic level sensor encounters impurities during transmission, compared to the reflected echoes from other ultrasonic level sensors within the same time frame, the reflected echo from that sensor will have a smaller amplitude and a more complex and chaotic echo signal distribution.

[0082] Based on the above analysis, the entropy of each echo signal segment is calculated to characterize the complexity of the signal distribution within each echo signal segment. Taking echo signal segment C(i,k) as an example, the difference between the entropy of echo signal segment C(i,k) and the entropy of each corresponding echo signal segment is calculated. The mean of all such differences for echo signal segment C(i,k) is denoted as the first mean difference. The larger the first mean difference, the more complex and chaotic the echo signal distribution characteristics of echo signal segment C(i,k) compared to echo signal segments formed within the same time range.

[0083] In this embodiment, the entropy of the echo signal segment is fuzzy entropy. As other implementation methods, based on the ability to measure the complexity of the signal distribution in the echo signal segment, the implementer may use other existing technologies for measurement, such as approximate entropy, sample entropy, etc. This application does not impose any special restrictions.

[0084] The average value of the amplitude of all sampling points in each echo signal segment is taken as the signal amplitude of each echo signal segment. The difference between the signal amplitude of echo signal segment C(i,k) and each of its corresponding echo signal segments is recorded as the amplitude difference. The average value of all the amplitude differences of echo signal segment C(i,k) is recorded as the second difference average value. The larger the second difference average value, the larger the echo signal amplitude of echo signal segment C(i,k) compared to echo signal segments formed within the same time range.

[0085] The mean of the second difference of the echo signal segment C(i,k) is mapped to a positive number. The ratio of the mean of the first difference of the echo signal segment C(i,k) to the positive number is used as the impurity interference coefficient of the echo signal segment C(i,k), which characterizes the degree of interference of the echo signal segment C(i,k) with impurities in the transformer oil conservator compared to echo signal segments formed within the same time range. The mean of the impurity interference coefficients of all echo signal segments of the denoised echo signal C(i) is used as the impurity interference degree of the i-th ultrasonic level sensor, which is used to evaluate the degree of interference of the echo signal received by the i-th ultrasonic level sensor with impurities in the transformer oil conservator. The greater the impurity interference degree, the lower the reliability of the initial acoustic wave transmission time measured by the i-th ultrasonic level sensor. Therefore, when performing weighted averaging on all the initial acoustic wave transmission times, the weight of the initial acoustic wave transmission time of the i-th ultrasonic level sensor should be smaller. The purpose of mapping the second difference mean to a positive number is to avoid a denominator of 0. There are many ways to map data to a positive number, and this application does not impose any special restrictions on this. In this embodiment, the purpose of mapping the second difference mean to a positive number is achieved by using the second difference mean as the exponent of an exponential function with the natural constant as the base. A schematic diagram of the process for obtaining the impurity interference degree is shown below. Figure 3 As shown.

[0086] The impurity interference degree of the remaining ultrasonic level sensors is calculated using the same calculation method as that used for the i-th ultrasonic level sensor.

[0087] Step S3: Calculate the oil level in the oil tank using the impurity interference level and the initial sound wave transmission time.

[0088] By weighting and fusing the initial acoustic wave propagation times of the high-frequency pulse acoustic wave signals transmitted by all ultrasonic level sensors based on the impurity interference levels of each sensor, the comprehensive acoustic wave propagation time of all high-frequency pulse acoustic wave signals is obtained, expressed as:

[0089] In the formula, T represents the combined acoustic transmission time of all high-frequency pulse acoustic signals; M represents the number of ultrasonic level sensors; the impurity interference degree of each ultrasonic level sensor is mapped 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 level sensor; t(i) represents the initial acoustic transmission time of the high-frequency pulse acoustic signal sent by the i-th ultrasonic level sensor. 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 impose any special restrictions on this. In this embodiment, the purpose of mapping the second difference mean to a positive number is achieved by using the impurity interference degree as the exponent of an exponential function with the natural constant as the base.

[0090] In this embodiment, the Softmax function is used to obtain the normalized value of the reciprocal.

[0091] The oil level in the tank is calculated using the combined sound wave transmission time. The formula for calculating the oil level is a well-known technique and will not be elaborated upon in this application.

[0092] Based on the same inventive concept as the above method, this application also provides a transformer oil conservator oil level measuring device, comprising:

[0093] The signal acquisition module is used to acquire the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal.

[0094] The signal analysis module is used to obtain the intrinsic mode functions (EMFs) of each echo signal. By analyzing the correlation between each EMF and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, the characteristic factors of each EMF are obtained. Based on the distribution of the characteristic factors of all EMFs of each echo signal, the denoised echo signal of each echo signal is reconstructed.

[0095] The endpoint detection algorithm is used 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 distribution of each echo signal segment of the other denoised echo signals, the corresponding echo signal segments of the given echo signal segment are obtained.

[0096] By analyzing the differences in signal distribution complexity and amplitude between each echo signal segment and its corresponding control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained.

[0097] The impurity interference degree of each ultrasonic level sensor is obtained by analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor.

[0098] The oil level calculation module is used to calculate the oil level height in the oil tank by using the impurity interference degree and the initial sound wave transmission time.

[0099] Based on the same inventive concept as the above method, this application embodiment also provides a transformer oil tank level measurement 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, it implements the steps of any one of the above-described transformer oil tank level measurement methods.

[0100] In summary, this application preprocesses the echo signal 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 pulse acoustic signal, and calculating the characteristic factor of the intrinsic mode function of the echo signal. Compared with the direct use of existing signal denoising algorithms, this method can effectively filter out noise and irrelevant clutter signals in the echo signal received by each ultrasonic level sensor, and reduce the impact of noise and irrelevant clutter signals on the subsequent evaluation of the degree of interference of the echo signal by impurities.

[0101] This application evaluates the degree of interference from impurities in the transformer oil conservator by analyzing the amplitude differences and signal distribution complexity differences between echo signal segments generated within the same time range. Based on the evaluation results, the initial acoustic wave transmission time obtained by all ultrasonic level sensors is weighted, and the oil level height in the oil conservator is calculated using the weighted processing result. Compared with the existing method of directly using the acoustic wave transmission time obtained by the ultrasonic level sensor to calculate the oil level height in the transformer oil conservator, this method can effectively reduce the influence of impurities in the oil conservator on the oil level measurement results and improve the accuracy of the oil level measurement results in the transformer oil conservator.

[0102] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than that shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in 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 description, and 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 reverse order, depending on the functions involved. Each block in a block diagram and / or flowchart, and combinations of blocks in a block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0103] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from its essential characteristics. Therefore, the embodiments described above should be considered exemplary and non-limiting in all respects.

Claims

1. A method for measuring the oil level in a transformer oil conservator, characterized in that, The method includes the following steps: Collect the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal. The intrinsic mode functions (EMFs) of each echo signal are obtained. By analyzing the correlation between each EMF and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, the characteristic factors of each EMF are obtained. The denoised echo signals of each echo signal are reconstructed by the distribution of the characteristic factors of all EMFs of each echo signal. The endpoint detection algorithm is used 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 distribution of each echo signal segment of the other denoised echo signals, the corresponding echo signal segments of the given echo signal segment are obtained. By analyzing the differences in signal distribution complexity and amplitude between each echo signal segment and its corresponding control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained. The impurity interference degree of each ultrasonic level sensor is obtained by analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor. The oil level in the tank is calculated using the impurity interference level and the initial sound wave transmission time. The calculation of the oil level in the oil tank includes: The combined acoustic wave propagation time of all high-frequency pulse acoustic wave signals is calculated using the impurity interference level and the initial acoustic wave propagation time, and the expression is as follows: In the formula, T represents the combined acoustic wave transmission time of all high-frequency pulse acoustic wave signals; M represents the number of ultrasonic level sensors; the impurity interference degree of each ultrasonic level sensor is mapped 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 level sensor; t(i) represents the initial acoustic wave transmission time of the high-frequency pulse acoustic wave signal sent by the i-th ultrasonic level sensor. The oil level in the tank is calculated using the combined sound wave transmission time.

2. The method for measuring the oil level in a transformer oil conservator as described in claim 1, characterized in that, The process of obtaining the feature factors is as follows: The average time-domain signal of all high-frequency pulse acoustic signals was obtained using the coherent averaging method. Calculate the correlation coefficients between each intrinsic mode function and the average time-domain signal; The spectra of each intrinsic mode function and the average time domain signal are obtained by using Fourier transform, and the spectral similarity between the spectra of each intrinsic mode function and the spectrum of the average time domain signal is calculated. The product of the correlation coefficient and the spectral similarity is used as the characteristic factor of each intrinsic mode function.

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

4. The method for measuring the oil level in a transformer oil conservator as described in claim 1, characterized in that, The process of obtaining the reference echo signal segment is as follows: The time of the sampling point with the largest amplitude in each echo signal segment is taken as the echo arrival time of each echo signal segment. From all the denoised echo signals other than the aforementioned denoised echo signal, select the echo signal segment with the shortest time interval between the echo arrival time and the aforementioned echo signal segment, and use it as the reference echo signal segment for the aforementioned echo signal segment.

5. The method for measuring the oil level in a transformer oil conservator as described in claim 1, characterized in that, The process for obtaining the impurity interference coefficient is as follows: Calculate the entropy of each echo signal segment; take the average amplitude 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 corresponding echo signal segment; The average of all the differences in each echo signal segment is denoted as the first difference average. The difference in signal amplitude between each echo signal segment and its corresponding reference echo signal segment is denoted as amplitude difference; the mean of all amplitude differences for each echo signal segment is denoted as second difference mean. By combining the first average difference and the second average difference, the impurity interference coefficient of each echo signal segment is obtained.

6. The method for measuring the oil level in a transformer oil conservator as described in claim 5, characterized in that, The calculation process of the impurity interference coefficient is as follows: the mean of the second difference is mapped to a positive number, and the ratio of the mean of the first difference to the positive number is used as the impurity interference coefficient of each echo signal segment.

7. The method for measuring the oil level in a transformer oil conservator as described in claim 1, characterized in that, The impurity interference degree is the average of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor.

8. A transformer oil conservator oil level measuring device, implementing the method as described in claim 1, characterized in that, The device includes: The signal acquisition module is used to acquire the high-frequency pulse acoustic wave signals sent by each ultrasonic liquid level sensor and the received echo signals, and to obtain the initial acoustic wave transmission time of each high-frequency pulse acoustic wave signal. The signal analysis module is used to obtain the intrinsic mode functions (EMFs) of each echo signal. By analyzing the correlation between each EMF and all high-frequency pulse acoustic signals in the time domain, as well as the similarity of their frequency distributions in the frequency domain, the characteristic factors of each EMF are obtained. Based on the distribution of the characteristic factors of all EMFs of each echo signal, the denoised echo signal of each echo signal is reconstructed. The endpoint detection algorithm is used 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 distribution of each echo signal segment of the other denoised echo signals, the corresponding echo signal segments of the given echo signal segment are obtained. By analyzing the differences in signal distribution complexity and amplitude between each echo signal segment and its corresponding control echo signal segment, the impurity interference coefficient of each echo signal segment is obtained. The impurity interference degree of each ultrasonic level sensor is obtained by analyzing the distribution of the impurity interference coefficients of all echo signal segments corresponding to each ultrasonic level sensor. The oil level calculation module is used to calculate the oil level height in the oil tank by using the impurity interference degree and the initial sound wave transmission time; The calculation of the oil level in the oil tank includes: The combined acoustic wave propagation time of all high-frequency pulse acoustic wave signals is calculated using the impurity interference level and the initial acoustic wave propagation time, and the expression is as follows: In the formula, T represents the combined acoustic wave transmission time of all high-frequency pulse acoustic wave signals; M represents the number of ultrasonic level sensors; the impurity interference degree of each ultrasonic level sensor is mapped 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 level sensor; t(i) represents the initial acoustic wave transmission time of the high-frequency pulse acoustic wave signal sent by the i-th ultrasonic level sensor. The oil level in the tank is calculated using the combined sound wave transmission time.

9. 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, it implements the steps of the transformer oil tank level measurement method as described in any one of claims 1-7.

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