Optical fiber ultrasonic sensor and detection method for partial discharge detection

Abstract

The present invention relates to the field of discharge detection technology, and in particular to an optical fiber ultrasonic sensor and a detection method for local discharge detection. The present invention determines the basic frequency by the degree of peak multiple distribution and uniform distribution between the frequencies of the sound wave signal to obtain a smooth sound wave signal; determines the change moment of the optical fiber ultrasonic sensor by the distribution of the local amplitude, and determines the discharge start time of the optical fiber ultrasonic sensor in combination with the approximate distribution of the change moment; obtains the desirability of each optical fiber ultrasonic sensor by the degree of correlation of the amplitude change trend; and determines the local discharge position and discharge time by desirability based on three-point positioning combined with the position of the optical fiber ultrasonic sensor and the discharge start time. The present invention smoothes the signal of the optical fiber ultrasonic sensor to determine the time of receiving the local discharge, determines the credibility of each optical fiber ultrasonic sensor by the signal change trend, and adjusts the positioning analysis process to determine a more accurate local discharge position and time.

Description

Technical Field

[0001] The present invention relates to the technical field of discharge detection, and in particular to an optical fiber ultrasonic sensor and a detection method for partial discharge detection. Background Art

[0002] Partial discharge may cause safety accidents such as fire or electric shock, threatening the safety of personnel and equipment. Therefore, accurately locating the location and time of partial discharge is crucial for the safe, stable and efficient operation of equipment. The sound waves generated when partial discharge occurs propagate outward from the discharge source. The fiber optic ultrasonic sensor will receive these sound waves at different times. Generally, the three-point positioning principle (the distance from the sensor to the discharge source = the speed of sound × the time difference between the sensor receiving the signal and the discharge source transmitting the signal) is used to determine the location and time of partial discharge through the time when each sensor receives the signal and the known sensor position.

[0003] The existing technology usually uses the local maximum amplitude method to determine the time when each fiber optic ultrasonic sensor receives the signal to analyze the location of local discharge. However, during local discharge, there are not only ultrasonic waves generated by the change in the density of the medium due to electrical breakdown, but also ultrasonic waves such as additional sound waves caused by mechanical vibrations caused by the tiny displacement of the insulating material due to the electric action caused by the local discharge. In addition, due to external influences such as position distribution, different fiber optic ultrasonic sensors have different deviations in the received signals, and the time when the fiber optic ultrasonic sensor receives the local discharge is not accurately determined. When the deviations of the fiber optic ultrasonic sensors are large, the results of the positioning analysis will also have large deviations, resulting in low accuracy in the detected local discharge position and time. Summary of the invention

[0004] In order to solve the technical problem that the time when the optical fiber ultrasonic sensor receives the partial discharge is not accurately determined in the prior art, when the optical fiber ultrasonic sensor has a large deviation, the positioning analysis result will also have a large deviation, thereby causing the detected partial discharge position and time to have low accuracy, the purpose of the present invention is to provide an optical fiber ultrasonic sensor for partial discharge detection and a detection method, and the technical scheme adopted is as follows:

[0005] The present invention provides a detection method of an optical fiber ultrasonic sensor for partial discharge detection, the method comprising:

[0006] obtaining an acoustic wave signal of each optical fiber ultrasonic sensor;

[0007] In the frequency domain space of the acoustic wave signal of each optical fiber ultrasonic sensor, the basic frequency of each optical fiber ultrasonic sensor is obtained according to the peak value and multiple distribution between frequencies and the uniform distribution degree between the frequencies with peak value and multiple distribution; and a smooth acoustic wave signal of each optical fiber ultrasonic sensor is obtained by smoothing the basic frequency;

[0008] Determine the change time of each optical fiber ultrasonic sensor according to the amplitude distribution in the smoothed sound wave signal of each optical fiber ultrasonic sensor; determine the discharge start time of each optical fiber ultrasonic sensor under a single partial discharge according to the approximate distribution between all the change times in all the optical fiber ultrasonic sensors;

[0009] Under a single partial discharge, the desirability of each optical fiber ultrasonic sensor under a single partial discharge is obtained according to the correlation between the amplitude variation trend of the smoothed acoustic wave signal between each optical fiber ultrasonic sensor and other optical fiber ultrasonic sensors after the discharge start time.

[0010] Under a single partial discharge, the discharge position and discharge time of the single partial discharge are obtained through three-point positioning based on the distribution positions of all fiber optic ultrasonic sensors, the discharge start time and the desirability of each fiber optic ultrasonic sensor.

[0011] Furthermore, the method for obtaining the basic frequency includes:

[0012] Processing the acoustic wave signal of each optical fiber ultrasonic sensor by Fourier transform to obtain a frequency spectrum of each optical fiber ultrasonic sensor;

[0013] For any fiber optic ultrasonic sensor, obtain the peak value in the spectrum diagram of the fiber optic ultrasonic sensor; obtain the possible index of the multiple of each peak value according to the number of integer multiple frequencies between each peak value and other peak values ​​in the spectrum diagram of the fiber optic ultrasonic sensor;

[0014] According to the uniformity of the interval between each peak and other peaks with integer multiple frequencies in the spectrum diagram of the optical fiber ultrasonic sensor, a possible distribution index of each peak is obtained;

[0015] The fundamental frequency possibility of each peak is obtained by combining the multiple possibility index and the distribution possibility index of each peak; the frequency corresponding to the peak of the maximum fundamental frequency possibility is used as the fundamental frequency of the optical fiber ultrasonic sensor.

[0016] Furthermore, the distribution index of each peak value is obtained based on the uniformity of the interval between each peak value and other peak values ​​with integer multiple frequencies in the spectrum diagram of the optical fiber ultrasonic sensor, including:

[0017] For any peak in the spectrum diagram of the optical fiber ultrasonic sensor, when the remainder of the frequency between the remaining peaks and the peak is zero, the corresponding remaining peak is taken as the frequency-doubled peak of the peak;

[0018] Arrange the frequencies corresponding to the peak value and all the frequency-multiplied peak values ​​in ascending order to obtain a frequency distribution sequence of the peak value;

[0019] The difference between every two adjacent frequencies in the frequency distribution sequence of the peak is calculated as the distribution difference, and the variances of all distribution differences are negatively correlated and mapped as possible indicators of the distribution of the peak.

[0020] Further, obtaining a smoothed acoustic wave signal of each optical fiber ultrasonic sensor by basic frequency smoothing includes:

[0021] In the spectrum diagram of each optical fiber ultrasonic sensor, the basic frequency and its frequency multiples of the optical fiber ultrasonic sensor are retained, and the remaining frequencies are smoothed. The smoothed spectrum diagram is transformed by inverse Fourier transform to obtain the smoothed sound wave signal of each optical fiber ultrasonic sensor.

[0022] Furthermore, the method for obtaining the change time includes:

[0023] For any optical fiber ultrasonic sensor, each moment of traversing the optical fiber ultrasonic sensor is taken as the analysis moment;

[0024] When the sound wave amplitudes at all times within a preset neighborhood range of the analysis time are smaller than the sound wave amplitude at the analysis time, the corresponding analysis time is used as the change time of the optical fiber ultrasonic sensor.

[0025] Furthermore, the method for obtaining the discharge start time includes:

[0026] The number of change moments in each optical fiber sensor is counted as the total number of discharges of each optical fiber sensor; the mode of the total number of discharges of all optical fiber sensors is taken as the number of classifications;

[0027] Based on the approximation of the time, all the change moments in all the fiber optic ultrasonic sensors are clustered, the number of clusters is the number of classifications, and the discharge clusters are obtained;

[0028] The change moment of each optical fiber ultrasonic sensor in each discharge cluster is taken as the discharge start moment of each optical fiber ultrasonic sensor under a single partial discharge.

[0029] Furthermore, the method for obtaining the desirability includes:

[0030] Under a single partial discharge, for any optical fiber ultrasonic sensor, in the smoothed acoustic wave signal of the optical fiber ultrasonic sensor, the acoustic wave amplitudes at a preset number of moments after the discharge start moment are arranged in time sequence to obtain a trend change sequence of the optical fiber ultrasonic sensor;

[0031] Calculating the Pearson correlation coefficient between the trend change series of the optical fiber ultrasonic sensor and each other optical fiber ultrasonic sensor to obtain the correlation between the optical fiber ultrasonic sensor and each other optical fiber ultrasonic sensor;

[0032] The sum of the correlations between the optical fiber ultrasonic sensor and all other optical fiber ultrasonic sensors is normalized to obtain the desirability of the optical fiber ultrasonic sensor.

[0033] Furthermore, under a single partial discharge, based on the distribution positions of all optical fiber ultrasonic sensors, the discharge start time, and the desirability of each optical fiber ultrasonic sensor, the discharge position and discharge time of the single partial discharge are obtained through three-point positioning, including:

[0034] Under a single partial discharge, all the optical fiber ultrasonic sensors are arranged and combined to obtain different optical fiber ultrasonic sensor combinations, each of which contains three different optical fiber ultrasonic sensors; and the distribution position of each optical fiber sensor is obtained;

[0035] Based on the distribution position, discharge start time and sound velocity of each fiber optic ultrasonic sensor in each fiber optic ultrasonic sensor combination, a three-point positioning equation is constructed; the estimated discharge position and estimated discharge time of the local discharge under each fiber optic ultrasonic sensor combination are obtained through the three-point positioning equation;

[0036] The desirability and value of each fiber optic ultrasonic sensor in each fiber optic ultrasonic sensor combination are used as the trust weight of each fiber optic ultrasonic sensor combination; the ratio of the trust weight of each fiber optic ultrasonic sensor combination to the accumulated value of the trust weights of all fiber optic ultrasonic sensor combinations is used as the weighting coefficient of each fiber optic ultrasonic sensor combination;

[0037] The estimated discharge positions of all fiber optic ultrasonic sensor combinations are weighted and averaged by a weighting coefficient to obtain the discharge position of the partial discharge; the estimated discharge time of all fiber optic ultrasonic sensor combinations is weighted and averaged by a weighting coefficient to obtain the discharge time of the partial discharge.

[0038] Furthermore, the expression of the three-point positioning equation is: ;

[0039] In the formula, and It is represented as the estimated discharge position of partial discharge under the i-th fiber optic ultrasonic sensor combination, It is expressed as the estimated discharge time of partial discharge under the i-th fiber optic ultrasonic sensor combination, Expressed as the speed of sound, and It is represented as the distribution position of the first fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the first optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the second fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the second optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the third fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge starting time of the third optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination.

[0040] The present invention also provides an optical fiber ultrasonic sensor for partial discharge detection, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0041] The present invention has the following beneficial effects:

[0042] The present invention takes into account that local discharge is caused by a sudden change in the electric field intensity, and usually exhibits the characteristics of a periodic pulse phenomenon, which is manifested as a multiple frequency distribution of the fundamental frequency in the frequency domain space and is evenly spaced. Therefore, the basic frequency is determined by the degree to which the acoustic wave signal of the optical fiber ultrasonic sensor is distributed in multiples of peak values ​​between frequencies in the frequency domain space, and the corresponding uniform distribution. The basic frequency and its multiple frequencies can reflect the situation of receiving local discharge in the acoustic wave signal, thereby filtering and smoothing to obtain a smooth acoustic wave signal, thereby improving the accuracy of the subsequent determination of the time when the optical fiber ultrasonic sensor receives the local discharge. When the discharge occurs, a strong sound wave is generated, and a high-amplitude peak is initially generated, and then the energy gradually dissipates. Therefore, the change time of the change in the optical fiber ultrasonic sensor is further determined by the distribution of the local amplitude, and the multiple discharge situations that may exist are considered, and the distribution approximation of the change time is used to distinguish, thereby determining the discharge start time of each optical fiber ultrasonic sensor corresponding to a single local discharge, and providing more accurate data support for the subsequent analysis of the single local discharge situation. In the process of a single local discharge, the possible deviation degree of each fiber optic ultrasonic sensor is analyzed by the correlation degree of the amplitude change trend, and the desirability is obtained to reflect the credibility of each fiber optic ultrasonic sensor, so that the results of subsequent analysis by the corresponding fiber optic ultrasonic sensor are more reliable. Finally, based on three-point positioning, the position of the fiber optic ultrasonic sensor and the start time of the discharge are analyzed, and the desirability of each fiber optic ultrasonic sensor is weighted to obtain a more accurate local discharge position and discharge time. The present invention smoothes the signal of the fiber optic ultrasonic sensor to determine the start time of each local discharge, determines the credibility of each fiber optic ultrasonic sensor by the signal change trend between the fiber optic ultrasonic sensors, and adjusts the positioning analysis process to determine a more accurate local discharge position and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A flow chart of a detection method of an optical fiber ultrasonic sensor for partial discharge detection provided by one embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the installation distribution of an optical fiber ultrasonic sensor provided by one embodiment of the present invention;

[0046] Figure 3 A schematic diagram of an acoustic wave signal of an optical fiber ultrasonic sensor provided by an embodiment of the present invention;

[0047] Figure 4 A flow chart of a method for obtaining a basic frequency provided by an embodiment of the present invention;

[0048] Figure 5 A schematic diagram of a smoothed acoustic wave signal of a fiber optic ultrasonic sensor provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation, structure, features and effects of an optical fiber ultrasonic sensor and a detection method for partial discharge detection proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0050] Unless defined otherwise, 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 invention belongs.

[0051] The following is a detailed description of a fiber optic ultrasonic sensor and a specific method for partial discharge detection provided by the present invention in conjunction with the accompanying drawings.

[0052] The reason why local discharge produces ultrasonic waves is that when the local medium is broken down, the current suddenly increases, causing local heat release and the local volume to increase in a short time. After the discharge ends, the local volume cools and shrinks. This process causes the density of the medium to change and produces ultrasonic waves.

[0053] See also Figure 1, which shows a flow chart of a detection method of a fiber optic ultrasonic sensor for partial discharge detection provided by an embodiment of the present invention, the method comprising the following steps:

[0054] S1: Obtain the acoustic wave signal of each optical fiber ultrasonic sensor.

[0055] In the embodiment of the present invention, a fiber optic ultrasonic sensor is installed every 5 meters on the insulating material to be detected to detect the occurrence of partial discharge. Each fiber optic ultrasonic sensor can collect sound wave signals. It should be noted that the installation of the fiber optic sensor can be adjusted according to the specific implementation scenario and is not limited here. Please refer to Figure 2 , which shows a schematic diagram of the installation distribution of an optical fiber ultrasonic sensor provided by an embodiment of the present invention. Figure 3 , which shows a schematic diagram of an acoustic wave signal of an optical fiber ultrasonic sensor provided by an embodiment of the present invention, wherein the horizontal axis is time and the vertical axis is the acoustic wave amplitude.

[0056] Fiber optic ultrasonic sensors use fiber optic technology to detect sound waves. They can capture all ultrasonic signals within a certain range and convert these signals into electrical signals. However, during partial discharge, there are not only ultrasonic waves generated by changes in the density of the medium due to electrical breakdown, but also mechanical vibrations and additional sound waves caused by the tiny displacement of the insulating material due to the electrical action caused by partial discharge. Therefore, it is necessary to smooth the sound wave signal to remove the interference part to ensure the accuracy of subsequent time determination.

[0057] S2: In the frequency domain space of the acoustic wave signal of each optical fiber ultrasonic sensor, the basic frequency of each optical fiber ultrasonic sensor is obtained according to the peak multiple distribution between frequencies and the uniform distribution degree between the frequencies with peak multiple distribution; and the smooth acoustic wave signal of each optical fiber ultrasonic sensor is obtained by smoothing the basic frequency.

[0058] The frequency domain space can reveal different components in the signal. In the implementation of the present invention, the acoustic wave signal of each optical fiber ultrasonic sensor is processed by Fourier transform to obtain the spectrum diagram of each optical fiber ultrasonic sensor. The spectrum diagram shows the amplitude or power distribution of the signal at different frequencies. The spectrum diagram of the optical fiber ultrasonic sensor corresponds not only to the electrical breakdown frequency, but also to other interference frequencies. It should be noted that the method of obtaining the spectrum diagram by Fourier transform processing is a technical means well known to those skilled in the art and will not be elaborated here.

[0059] The accurate positioning of partial discharge is based only on the electrical breakdown frequency. As for the electrical breakdown frequency, since partial discharge is caused by a sudden change in the electric field strength, it usually manifests as a periodic pulse phenomenon. This periodicity leads to the appearance of regular harmonic components in its spectrum. The frequency usually manifests as the fundamental frequency and its multiples and is evenly spaced. Other interference frequencies, such as mechanical vibration, have various sources and may contain multiple frequency components, which makes its spectrum more complex, irregular and unevenly spaced.

[0060] Therefore, to determine the electrical breakdown frequency, it is necessary to first determine the basic frequency. Generally, the basic frequency in the electrical breakdown frequency is the frequency corresponding to the first significant peak in the spectrum, and the remaining frequencies are integer multiples of the basic frequency. However, due to the existence of other interference frequencies, the frequency of the first peak may not be the basic frequency. However, according to the characteristics of multiple distribution, the basic frequency can be determined by the existence of multiple frequencies. It is also considered that if there is a smaller interference frequency, such as frequency 1, so that all other frequencies are its multiples, it may not be accurate to judge only by multiple analysis. It is possible to further determine the basic frequency in combination with the uniformity of the branch interval.

[0061] Preferably, in the possible implementation method of the embodiment of the present invention, the method for obtaining the basic frequency can be found in Figure 4 , which shows a flow chart of a method for obtaining a basic frequency provided by an embodiment of the present invention, the method comprising the following steps:

[0062] S201: For any fiber optic ultrasonic sensor, obtain peak values ​​in the frequency spectrum of the fiber optic ultrasonic sensor; and obtain a possible index of the multiple of each peak value according to the number of integer multiple frequencies between each peak value and other peak values ​​in the frequency spectrum of the fiber optic ultrasonic sensor.

[0063] In the spectrum diagram, first determine the peak point where the derivative is zero. The peak position is the situation where the signal energy reaches the maximum in frequency, so the basic frequency must exist in the frequency corresponding to the peak, and only the frequency of the peak situation is analyzed. In the embodiment of the present invention, the first-order derivative method can be used, that is, the derivative of the frequency domain signal is calculated, and the point when the first-order derivative is zero is taken as the peak.

[0064] In the embodiment of the present invention, for any peak in the spectrum diagram of the optical fiber ultrasonic sensor, the remainder of the frequency between each remaining peak and the peak is calculated. The number of zero remainders is counted to obtain a possible index of the multiple of the peak. When the remainder is zero, it means that there are integer multiple frequencies. The more integer multiple frequencies there are, the higher the possibility of the basic frequency.

[0065] S202: Obtain a possible distribution index for each peak value according to the uniformity of intervals between each peak value and other peak values ​​having integer multiple frequencies in the frequency spectrum of the optical fiber ultrasonic sensor.

[0066] Considering the uniformity of the electrical breakdown frequency interval, that is, the difference between adjacent multiples should be equal, the more uniform the distribution between adjacent multiples, the higher the possibility that the peak corresponds to the basic frequency.

[0067] In an embodiment of the present invention, for any peak in the spectrum diagram of the fiber optic ultrasonic sensor, when the remainder of the frequency between the remaining peaks and the peak is zero, the corresponding remaining peaks are used as the frequency doubled peaks of the peak, and all frequencies with integer multiples of the peak are screened out for uniformity analysis.

[0068] Further, the frequencies corresponding to the peak value and all the frequency doubling peak values ​​are arranged in order from small to large to obtain the frequency distribution sequence of the peak value, and the difference between each two adjacent frequencies in the frequency distribution sequence of the peak value is calculated as the distribution difference, which reflects the interval degree between each two adjacent frequencies. The variances of all distribution differences are negatively correlated and mapped as possible indicators of the distribution of the peak value. The variance reflects the uniformity of the interval degree. The smaller the variance, the more uniform the interval distribution, and the higher the possibility of the basic frequency. It should be noted that negative correlation mapping is a technical means well known to those skilled in the art, and can adopt inverse proportion or negative exponential power properties, which are not limited here.

[0069] S203: Combining the multiple possibility index and the distribution possibility index of each peak value, obtaining the fundamental frequency possibility of each peak value; taking the frequency corresponding to the peak value of the maximum fundamental frequency possibility as the fundamental frequency of the optical fiber ultrasonic sensor.

[0070] According to the frequency multiplication situation and the uniformity of the interval distribution, when the number of frequency multiplication is greater and the interval distribution is more uniform, the possibility that the frequency corresponding to the peak value is used as the basic frequency of the electrical breakdown frequency is higher. In the embodiment of the present invention, the product of the multiple possibility index and the distribution possibility index of each peak value is used as the basic frequency possibility of each peak value. The maximum value corresponding to the basic frequency possibility reflects that the frequency corresponding to its peak value is the most likely to be the basic frequency, so the frequency corresponding to the peak value of the maximum basic frequency possibility is used as the basic frequency of the optical fiber ultrasonic sensor.

[0071] At this point, the acquisition of the basic frequency of the electrical breakdown frequency is completed. The smoothed sound wave signal of each fiber optic ultrasonic sensor is obtained by smoothing the basic frequency. In the embodiment of the present invention, the basic frequency and its multiples are retained in the spectrum diagram of the fiber optic ultrasonic sensor, and the remaining frequencies are smoothed, such as by filtering and smoothing with a band-stop filter, and finally the smoothed sound wave signal of the fiber optic ultrasonic sensor with other interference frequencies removed is obtained by inverse Fourier transform. Please refer to Figure 5 , which shows a schematic diagram of a smoothed sound wave signal of a fiber optic ultrasonic sensor provided by an embodiment of the present invention.

[0072] At this point, the filtering and smoothing of the acoustic wave signal is completed, and the time when each optical fiber ultrasonic sensor receives the partial discharge can be more accurately determined based on the smoothed acoustic wave signal.

[0073] S3: Determine the change time of each fiber optic ultrasonic sensor according to the amplitude distribution in the smoothed sound wave signal of each fiber optic ultrasonic sensor; determine the discharge start time of each fiber optic ultrasonic sensor under a single partial discharge according to the approximate distribution between all change times in all fiber optic ultrasonic sensors.

[0074] Since partial discharge is usually instantaneous, a strong sound wave will be generated when the discharge occurs. Initially, a high-amplitude peak will be generated, and then the energy will gradually dissipate. Therefore, the time when the partial discharge starts is received, which is also the time corresponding to the analysis of the local maximum amplitude change. Therefore, according to the amplitude distribution in the smoothed acoustic wave signal of each fiber optic ultrasonic sensor, when the amplitudes before and after the moment in the signal are all less than the corresponding amplitude at the moment, the corresponding moment is the maximum peak moment of the partial discharge, and this moment is the moment when the fiber optic ultrasonic sensor receives the change of the partial discharge.

[0075] Preferably, in an embodiment of the present invention, the method for acquiring the change time includes:

[0076] For any fiber optic ultrasonic sensor, each moment of the fiber optic ultrasonic sensor is traversed as an analysis moment, and each moment is analyzed. When the sound wave amplitudes at all moments within the preset neighborhood range of the analysis moment are smaller than the sound wave amplitude at the analysis moment, it indicates that a local maximum amplitude occurs at the moment, and the corresponding analysis moment is taken as the change moment of the fiber optic ultrasonic sensor. In a specific embodiment of the present invention, the preset neighborhood range of the analysis moment is set to a range with a side length of 11 and a center at the analysis moment. The specific range size can be adjusted by the implementer according to the specific implementation scenario and is not limited here.

[0077] Since the fiber optic ultrasonic sensor may receive more than one discharge process, such as Figure 5 There are two partial discharges in the process, and it is necessary to distinguish the partial discharges and determine the single partial discharge for analysis. Although the fiber optic ultrasonic sensor will have an interval of receiving time due to the position distribution, the discharge process occurs at the microsecond level, the interval between different partial discharges is more significant, and the number of discharges received by different fiber optic sensors is consistent. The distribution of the change time between the fiber optic sensors is close, and the change time with close distribution is considered as the corresponding acceptance time of a partial discharge.

[0078] Preferably, in an embodiment of the present invention, the method for obtaining the discharge start time includes:

[0079] First, the number of changing moments in each optical fiber sensor is counted as the total number of discharges for each optical fiber sensor. The mode of the total number of discharges of all optical fiber sensors is taken as the number of categories. The number of changing moments contained in a single optical fiber sensor is also the total number of local discharge processes that can be received. It can be divided by clustering based on the number of local discharges. In order to reduce the impact of errors, the possibility of errors is eliminated by the mode to obtain the number of divided categories.

[0080] Furthermore, based on the approximation of the moments, all the change moments in all the fiber optic ultrasonic sensors are clustered, the number of clusters is the number of classifications, and the discharge clusters are obtained. In the embodiment of the present invention, k-means clustering processing can be used, and the number of clusters is limited to the number of classifications to obtain discharge clusters. Each discharge cluster corresponds to a local discharge, and the change moment in each discharge cluster is the moment when each fiber optic ultrasonic sensor starts to receive under a local discharge. It should be noted that clustering processing is a technical means well known to those skilled in the art, and will not be elaborated or limited here.

[0081] Therefore, the change time of each fiber optic ultrasonic sensor in each discharge cluster is taken as the discharge start time of each fiber optic ultrasonic sensor under a single partial discharge. So far, the determination of the partial discharge acceptance time of the fiber optic ultrasonic sensor is completed.

[0082] S4: Under a single partial discharge, the desirability of each optical fiber ultrasonic sensor under a single partial discharge is obtained according to the correlation between the amplitude variation trend of the smoothed acoustic wave signal between each optical fiber ultrasonic sensor and other optical fiber ultrasonic sensors after the discharge start time.

[0083] Since the distribution position of the fiber optic ultrasonic sensor is fixed, in the three-point positioning process, in order to improve the accuracy of the final partial discharge position and time, the data accuracy of each fiber optic ultrasonic sensor needs to be higher. When there are fiber optic ultrasonic sensors with certain deviations participating in the analysis, due to the consistent contribution rate of the participation, it will interfere with the final result and affect the accuracy. Therefore, it is necessary to analyze the credibility of each fiber optic ultrasonic sensor under a single partial discharge.

[0084] After partial discharge occurs, the wave will propagate in the medium at a certain speed. Therefore, when each fiber optic ultrasonic sensor receives the start of discharge, the amplitude will have a similar change trend. If the start time of discharge obtained by each fiber optic ultrasonic sensor is accurate, the other fiber optic ultrasonic sensors will have the same amplitude change trend, that is, the size is attenuated but the trend is the same. Therefore, the desirability of the fiber optic ultrasonic sensor is determined by the correlation of the amplitude change trend between the fiber optic ultrasonic sensors.

[0085] Preferably, in some possible implementation methods of the embodiments of the present invention, the method for obtaining desirability includes:

[0086] Under a single partial discharge, for any fiber optic ultrasonic sensor, in the smoothed acoustic wave signal of the fiber optic ultrasonic sensor, the acoustic wave amplitudes at a preset number of moments after the discharge start moment are arranged in time sequence to obtain a trend change sequence of the fiber optic ultrasonic sensor, reflecting the distribution change of the amplitude. In the embodiment of the present invention, the preset number can be set to 20, which can be adjusted by the implementer and is not limited here.

[0087] Furthermore, the Pearson correlation coefficient between the trend change sequence of the fiber optic ultrasonic sensor and each other fiber optic ultrasonic sensor is calculated to obtain the correlation between the fiber optic ultrasonic sensor and each other fiber optic ultrasonic sensor. The Pearson correlation coefficient is a statistic used to reflect the strength and direction of the linear relationship between two variable sequences. The larger the Pearson correlation coefficient, the stronger the positive correlation between the sequences, and the more consistent the sequences are.

[0088] Therefore, the sum of the correlations between the fiber optic ultrasonic sensor and all other fiber optic ultrasonic sensors is normalized to obtain the desirability of the fiber optic ultrasonic sensor. The greater the correlation between the fiber optic ultrasonic sensor and other fiber optic ultrasonic sensors, the smaller the deviation of the fiber optic ultrasonic sensor and the smaller the possibility of error influence. Therefore, the higher the credibility, the greater the desirability.

[0089] It should be noted that normalization processing is a technical means well known to those skilled in the art, and the normalization options may be linear normalization or standard normalization, etc. The specific normalization method is not limited here.

[0090] At this point, the analysis of the credibility of each fiber optic ultrasonic sensor is completed, and the desirability is obtained to adjust the contribution of subsequent different fiber optic ultrasonic sensors involved in the analysis.

[0091] S5: Under a single partial discharge, based on the distribution positions of all fiber optic ultrasonic sensors, the discharge start time, and the desirability of each fiber optic ultrasonic sensor, the discharge position and discharge time of the single partial discharge are obtained through three-point positioning.

[0092] Three-point positioning is a technology commonly used in measurement and navigation. Its basic principle is to determine the location of the target point through the information of three known fiber optic ultrasonic sensors. The detection process of partial discharge is to obtain the arrival time difference and time of the ultrasonic wave generated at the partial discharge position to the three fiber optic ultrasonic sensors, and determine the location and time of partial discharge through the time difference degree and position distribution difference.

[0093] Since the distance from each fiber optic ultrasonic sensor to the local discharge position is equal to the speed of sound multiplied by the propagation time difference, a three-variable linear equation can be formed for each fiber optic ultrasonic sensor. Because there are three unknowns, any combination of three fiber optic ultrasonic sensors can be used to locate the position and time of the start of local discharge.

[0094] Preferably, in the embodiment of the present invention, under a single partial discharge, all the optical fiber ultrasonic sensors are arranged and combined to obtain different optical fiber ultrasonic sensor combinations, each of which contains three different optical fiber ultrasonic sensors. For m optical fiber ultrasonic sensors, they can be divided into Combination of Expressed as a permutation and combination problem, the number of combinations that can be selected by randomly selecting 3 fiber optic ultrasonic sensors from m fiber optic ultrasonic sensors without considering the order.

[0095] The distribution position of each optical fiber sensor is obtained and represented by two-dimensional coordinates, that is, the distribution position of each optical fiber sensor is represented as (x, y). Based on the distribution position, discharge start time and sound speed of each optical fiber ultrasonic sensor in each optical fiber ultrasonic sensor combination, a three-point positioning equation is constructed. In an embodiment of the present invention, the three-point positioning equation expression of the i-th optical fiber ultrasonic sensor combination represented by a three-variable linear equation is: ;

[0096] In the formula, and It is represented as the estimated discharge position of partial discharge under the i-th fiber optic ultrasonic sensor combination, It is expressed as the estimated discharge time of partial discharge under the i-th fiber optic ultrasonic sensor combination, Expressed as the speed of sound, and It is represented as the distribution position of the first fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the first optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the second fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the second optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the third fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge starting time of the third optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination.

[0097] The estimated discharge position and estimated discharge time of local discharge under each fiber optic ultrasonic sensor combination are obtained through the three-point positioning equation. The three-point positioning equation of each fiber optic ultrasonic sensor combination can be solved to obtain an estimated discharge position and estimated discharge time of local discharge, and then the solution results of all combinations can be combined to obtain the final result.

[0098] Considering the different trustworthy conditions of contributions of different fiber optic sensors, the desirability and value of each fiber optic ultrasonic sensor in each fiber optic ultrasonic sensor combination are used as the trustworthy weight of each fiber optic ultrasonic sensor combination to reflect the overall trustworthy condition of the combination. The ratio of the trustworthy weight of each fiber optic ultrasonic sensor combination to the accumulated trustworthy weight of all fiber optic ultrasonic sensor combinations is used as the weighting coefficient of each fiber optic ultrasonic sensor combination, and the weighting coefficient is obtained by normalizing the trustworthy conditions of all combinations.

[0099] Finally, the estimated discharge positions of all fiber optic ultrasonic sensor combinations are weighted and averaged by weighting coefficients to obtain the discharge position of the partial discharge. As an example, the expression for obtaining the discharge position of the partial discharge is: ; ;

[0100] In the formula, and It represents the discharge position of partial discharge. and It is represented as the estimated discharge position of partial discharge under the i-th fiber optic ultrasonic sensor combination, Expressed as the weighting coefficient of the i-th fiber optic ultrasonic sensor combination, Expressed as the total number of fiber optic ultrasonic sensor combinations.

[0101] Similarly, the estimated discharge time of all fiber optic ultrasonic sensor combinations is weighted and averaged by the weighting coefficient to obtain the discharge time of the partial discharge, and the detection of the partial discharge is completed. In the embodiment of the present invention, by determining the specific location and time of the partial discharge, it can help locate the potential fault situation, facilitate timely maintenance, reduce the risk of equipment failure, and extend the service life. By collecting these data, it also provides a basis for subsequent analysis and research, which helps to understand the performance and aging mechanism of the equipment, and then optimize the design and improve the material selection.

[0102] It should be noted that, in order to facilitate calculation, all indicator data involved in the calculation in the embodiment of the present invention are preprocessed to eliminate the dimension effect. The specific means of eliminating the dimension effect are technical means well known to those skilled in the art and are not limited here.

[0103] The present invention takes into account that local discharge is caused by a sudden change in the electric field intensity, and usually exhibits the characteristics of a periodic pulse phenomenon, which is manifested as a multiple frequency distribution of the fundamental frequency in the frequency domain space and is evenly spaced. Therefore, the basic frequency is determined by the degree to which the acoustic wave signal of the optical fiber ultrasonic sensor is distributed in multiples of peak values ​​between frequencies in the frequency domain space, and the corresponding uniform distribution. The basic frequency and its multiple frequencies can reflect the situation of receiving local discharge in the acoustic wave signal, thereby filtering and smoothing to obtain a smooth acoustic wave signal, thereby improving the accuracy of the subsequent determination of the time when the optical fiber ultrasonic sensor receives the local discharge. When the discharge occurs, a strong sound wave is generated, and a high-amplitude peak is initially generated, and then the energy gradually dissipates. Therefore, the change time of the change in the optical fiber ultrasonic sensor is further determined by the distribution of the local amplitude, and the multiple discharge situations that may exist are considered, and the distribution approximation of the change time is used to distinguish, thereby determining the discharge start time of each optical fiber ultrasonic sensor corresponding to a single local discharge, and providing more accurate data support for the subsequent analysis of the single local discharge situation. In the process of a single local discharge, the possible deviation degree of each fiber optic ultrasonic sensor is analyzed by the correlation degree of the amplitude change trend, and the desirability is obtained to reflect the credibility of each fiber optic ultrasonic sensor, so that the results of subsequent analysis by the corresponding fiber optic ultrasonic sensor are more reliable. Finally, based on three-point positioning, the position of the fiber optic ultrasonic sensor and the start time of the discharge are analyzed, and the desirability of each fiber optic ultrasonic sensor is weighted to obtain a more accurate local discharge position and discharge time. The present invention smoothes the signal of the fiber optic ultrasonic sensor to determine the start time of each local discharge, determines the credibility of each fiber optic ultrasonic sensor by the signal change trend between the fiber optic ultrasonic sensors, and adjusts the positioning analysis process to determine a more accurate local discharge position and time.

[0104] The present invention also provides an optical fiber ultrasonic sensor for partial discharge detection, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0105] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0106] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A detection method of an optical fiber ultrasonic sensor for partial discharge detection, characterized in that: The method comprises: obtaining an acoustic wave signal of each optical fiber ultrasonic sensor; In the frequency domain space of the acoustic wave signal of each optical fiber ultrasonic sensor, the basic frequency of each optical fiber ultrasonic sensor is obtained according to the peak value and multiple distribution between frequencies and the uniform distribution degree between the frequencies with peak value and multiple distribution; and a smooth acoustic wave signal of each optical fiber ultrasonic sensor is obtained by smoothing the basic frequency; Determine the change time of each optical fiber ultrasonic sensor according to the amplitude distribution in the smoothed sound wave signal of each optical fiber ultrasonic sensor; determine the discharge start time of each optical fiber ultrasonic sensor under a single partial discharge according to the approximate distribution between all the change times in all the optical fiber ultrasonic sensors; Under a single partial discharge, the desirability of each optical fiber ultrasonic sensor under a single partial discharge is obtained according to the correlation between the amplitude variation trend of the smoothed acoustic wave signal between each optical fiber ultrasonic sensor and other optical fiber ultrasonic sensors after the discharge start time. Under a single partial discharge, the discharge position and discharge time of a single partial discharge are obtained through three-point positioning based on the distribution positions of all fiber optic ultrasonic sensors, the discharge start time and the desirability of each fiber optic ultrasonic sensor. The method for obtaining the basic frequency includes: Processing the acoustic wave signal of each optical fiber ultrasonic sensor by Fourier transform to obtain a frequency spectrum of each optical fiber ultrasonic sensor; For any fiber optic ultrasonic sensor, obtain the peak value in the spectrum diagram of the fiber optic ultrasonic sensor; obtain the possible index of the multiple of each peak value according to the number of integer multiple frequencies between each peak value and other peak values ​​in the spectrum diagram of the fiber optic ultrasonic sensor; According to the uniformity of the interval between each peak and other peaks with integer multiple frequencies in the spectrum diagram of the optical fiber ultrasonic sensor, a possible distribution index of each peak is obtained; Combining the multiple possible index and the distribution possible index of each peak value, the fundamental frequency possibility of each peak value is obtained; the frequency corresponding to the peak value of the maximum fundamental frequency possibility is used as the fundamental frequency of the optical fiber ultrasonic sensor; The possible distribution index of each peak value is obtained according to the uniformity of the interval between each peak value and other peak values ​​with integer multiple frequencies in the spectrum diagram of the optical fiber ultrasonic sensor, including: For any peak in the spectrum diagram of the optical fiber ultrasonic sensor, when the remainder after dividing each remaining peak by the corresponding frequency between the peak is zero, the corresponding remaining peak is taken as the frequency-doubled peak of the peak; Arrange the frequencies corresponding to the peak value and all the frequency-multiplied peak values ​​in ascending order to obtain a frequency distribution sequence of the peak value; The difference between every two adjacent frequencies in the frequency distribution sequence of the peak is calculated as the distribution difference, and the variances of all distribution differences are negatively correlated and mapped as possible indicators of the distribution of the peak.

2. The detection method of the optical fiber ultrasonic sensor for partial discharge detection according to claim 1, characterized in that: The method of obtaining a smoothed acoustic wave signal of each optical fiber ultrasonic sensor by smoothing the basic frequency includes: In the spectrum diagram of each optical fiber ultrasonic sensor, the basic frequency and its frequency multiples of the optical fiber ultrasonic sensor are retained, and the remaining frequencies are smoothed. The smoothed spectrum diagram is transformed by inverse Fourier transform to obtain the smoothed sound wave signal of each optical fiber ultrasonic sensor.

3. The detection method of the optical fiber ultrasonic sensor for partial discharge detection according to claim 1, characterized in that: The method for obtaining the change time includes: For any optical fiber ultrasonic sensor, each moment of traversing the optical fiber ultrasonic sensor is taken as the analysis moment; When the sound wave amplitudes at all times within a preset neighborhood range of the analysis time are smaller than the sound wave amplitude at the analysis time, the corresponding analysis time is used as the change time of the optical fiber ultrasonic sensor.

4. The detection method of the optical fiber ultrasonic sensor for partial discharge detection according to claim 1, characterized in that: The method for obtaining the discharge start time includes: The number of change moments in each optical fiber sensor is counted as the total number of discharges of each optical fiber sensor; the mode of the total number of discharges of all optical fiber sensors is taken as the number of classifications; Based on the approximation of the time, all the change moments in all the fiber optic ultrasonic sensors are clustered, the number of clusters is the number of classifications, and the discharge clusters are obtained; The change moment of each optical fiber ultrasonic sensor in each discharge cluster is taken as the discharge start moment of each optical fiber ultrasonic sensor under a single partial discharge.

5. The detection method of the optical fiber ultrasonic sensor for partial discharge detection according to claim 1, characterized in that: The method for obtaining the desirability includes: Under a single partial discharge, for any optical fiber ultrasonic sensor, in the smoothed acoustic wave signal of the optical fiber ultrasonic sensor, the acoustic wave amplitudes at a preset number of moments after the discharge start moment are arranged in time sequence to obtain a trend change sequence of the optical fiber ultrasonic sensor; Calculating the Pearson correlation coefficient between the trend change series of the optical fiber ultrasonic sensor and each other optical fiber ultrasonic sensor to obtain the correlation between the optical fiber ultrasonic sensor and each other optical fiber ultrasonic sensor; The sum of the correlations between the optical fiber ultrasonic sensor and all other optical fiber ultrasonic sensors is normalized to obtain the desirability of the optical fiber ultrasonic sensor.

6. The detection method of the optical fiber ultrasonic sensor for partial discharge detection according to claim 1, characterized in that: The method of obtaining the discharge position and discharge time of a single partial discharge by three-point positioning based on the distribution positions of all optical fiber ultrasonic sensors, the discharge start time, and the desirability of each optical fiber ultrasonic sensor under a single partial discharge includes: Under a single partial discharge, all the optical fiber ultrasonic sensors are arranged and combined to obtain different optical fiber ultrasonic sensor combinations, each of which contains three different optical fiber ultrasonic sensors; and the distribution position of each optical fiber sensor is obtained; Based on the distribution position, discharge start time and sound velocity of each fiber optic ultrasonic sensor in each fiber optic ultrasonic sensor combination, a three-point positioning equation is constructed; the estimated discharge position and estimated discharge time of the local discharge under each fiber optic ultrasonic sensor combination are obtained through the three-point positioning equation; The desirability and value of each fiber optic ultrasonic sensor in each fiber optic ultrasonic sensor combination are used as the trust weight of each fiber optic ultrasonic sensor combination; the ratio of the trust weight of each fiber optic ultrasonic sensor combination to the accumulated value of the trust weights of all fiber optic ultrasonic sensor combinations is used as the weighting coefficient of each fiber optic ultrasonic sensor combination; The estimated discharge positions of all fiber optic ultrasonic sensor combinations are weighted and averaged by a weighting coefficient to obtain the discharge position of the partial discharge; the estimated discharge time of all fiber optic ultrasonic sensor combinations is weighted and averaged by a weighting coefficient to obtain the discharge time of the partial discharge.

7. A detection method of an optical fiber ultrasonic sensor for partial discharge detection according to claim 6, characterized in that: The expression of the three-point positioning equation is: ; In the formula, and It is represented as the estimated discharge position of partial discharge under the i-th fiber optic ultrasonic sensor combination, It is expressed as the estimated discharge time of partial discharge under the i-th fiber optic ultrasonic sensor combination, Expressed as the speed of sound, and It is represented as the distribution position of the first fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the first optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the second fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge start time of the second optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination, and It is represented as the distribution position of the third fiber optic ultrasonic sensor in the i-th fiber optic ultrasonic sensor combination, It is represented as the discharge starting time of the third optical fiber ultrasonic sensor in the i-th optical fiber ultrasonic sensor combination.

8. An optical fiber ultrasonic sensor for partial discharge detection, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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