Partial discharge ultrasonic signal time difference estimation method

Abstract

The application discloses a partial discharge ultrasonic signal time difference estimation method, wherein two-channel partial discharge source ultrasonic signals are collected; the two signals are subjected to conjugate multiplication and weighting operation after being subjected to fast Fourier transform into a frequency domain; a zero filling operation, a power operation and an inverse fast Fourier transform are sequentially performed on the obtained discrete sequence; peak value extraction is performed on the obtained signal; if a set condition is met, the operation is exited, otherwise, the series operation of zero filling and power operation is repeated. The application has the advantages of improving the resolution of time difference estimation, fast operation speed, saving hardware cost and the like.

Description

Technical Field

[0001] This invention relates to the field of online monitoring technology for partial discharge in power equipment, and in particular to a method for estimating the time difference of ultrasonic signals for partial discharge. Background Technology

[0002] In the field of online monitoring of partial discharge in power equipment, in addition to detecting traditional characteristic parameters such as the number of discharges and discharge intensity, determining the location of partial discharges is also a crucial operation for the safe operation of power equipment. Locating the source of partial discharge can help quickly detect faults, accurately identify fault types, effectively propose maintenance plans, and assist in decision-making. Among various methods, the location method based on ultrasonic signals of partial discharge is widely used for partial discharge location in power equipment due to its advantages such as being unaffected by the strong electromagnetic environment in which the power equipment is located, strong penetration ability, and high sensitivity.

[0003] For partial discharge localization methods based on ultrasonic signals, TDOA and DOA algorithms are generally used. One essential step in these commonly used methods is estimating the time difference between the arrival of the ultrasonic signal from the partial discharge at the two microphones. Current development trends in ultrasonic partial discharge localization equipment focus on portability and miniaturization. However, for microphone arrays, miniaturization significantly amplifies localization errors, largely due to insufficient device resolution. To maximize signal resolution and reduce errors caused by device resolution, existing solutions involve selecting higher-resolution devices. However, in commercial applications, using high-precision microphones significantly increases costs and places greater demands on data storage and processing capabilities. Therefore, a super-resolution time difference estimation algorithm is urgently needed to overcome the limitations of microphone accuracy.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the shortcomings or defects of the existing technology, a method for estimating the time difference of partial discharge ultrasonic signals is provided. This method resolves the contradiction encountered in the miniaturization of existing partial discharge ultrasonic positioning equipment—namely, the insufficient accuracy of low-resolution devices versus the high cost and complex manufacturing process of high-resolution devices—and enables super-resolution estimation of the time difference of partial discharge ultrasonic signals using low-cost equipment.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] A method for estimating the time difference of partial discharge ultrasonic signals includes,

[0008] Step 1: Microphone a and microphone b respectively acquire the partial discharge ultrasonic signal a(t) and the partial discharge ultrasonic signal b(t) generated by the same partial discharge power source, and initialize variable k = 0;

[0009] Step 2: The partial discharge ultrasonic signal a(t) and the partial discharge ultrasonic signal b(t) are transformed to the frequency domain by fast Fourier transform to obtain A(f) and B(f);

[0010] Step 3: Perform a weighted operation after multiplying the conjugates of A(f) and B(f) to obtain the sequence.

[0011] Step 4: Let variable m = 2 k ;

[0012] Step 5: Insert zeros into the sequence X(f), where m-1 zeros are inserted after each value;

[0013] Step 6: Raise the sequence X(f) to the power of m to obtain X m (f);

[0014] Step 7: For X m (f) Perform an inverse fast Fourier transform to obtain x(t);

[0015] Step 8: Extract the peak value of |x(t)|. When k = 0, only one peak value can be extracted. The peak value time is denoted as Δt. (0) When k>0, 2 are extracted. k The peak value is taken as the one that is numerically closest to Δt. (k-1) The peak time is denoted as Δt. (k) ;

[0016] Step 9: If |Δt (k) -Δt (k-1) If | < ε, and ε is a positive number, then exit the loop; otherwise, let k = k + 1 and return to step 5.

[0017] Step 10: Take the final Δt. (k) The time difference between the two partial discharge ultrasonic signals is denoted as .

[0018] In the aforementioned method for estimating the time difference of partial discharge ultrasonic signals, ε is a positive number that approaches 0 infinitely.

[0019] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0020] This disclosure offers fast computation speed and does not alter the underlying logic of the Fast Fourier Transform and Inverse Fast Fourier Transform, making it highly computer-friendly. For portable partial discharge ultrasonic positioning devices, it can significantly reduce hardware costs while achieving precise positioning.

[0021] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0022] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0023] In the attached diagram:

[0024] Figure 1 This is a flowchart illustrating a method for estimating the time difference of partial discharge ultrasonic signals.

[0025] Figure 2 This is a schematic diagram of the simulated waveforms of ultrasonic signals from the same source acquired by two microphones, which is a method for estimating the time difference of partial discharge ultrasonic signals.

[0026] Figure 3 This is a schematic diagram of the simulation results of a method for estimating the time difference of partial discharge ultrasonic signals from the same source using two microphones, which is a simulation of a method for estimating the time difference of partial discharge ultrasonic signals.

[0027] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0028] The following will refer to the appendix. Figures 1 to 3 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0029] It should be noted that certain terms are used in the specification and claims to refer to predetermined components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0030] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0031] To better understand, such as Figures 1 to 3 As shown, a method for estimating the time difference of partial discharge ultrasonic signals includes,

[0032] Step 1: Microphone a and microphone b respectively acquire the partial discharge ultrasonic signals a(t) and b(t) generated by the same partial discharge power source, and initialize variable k = 0;

[0033] Step 2: Transform a(t) and b(t) to the frequency domain using Fast Fourier Transform to obtain A(f) and B(f);

[0034] Step 3: Perform a weighted summation operation after multiplying the conjugates of A(f) and B(f), i.e.

[0035] Step 4: Let variable m = 2 k ;

[0036] Step 5: Insert zeros into the sequence X(f) according to the rule that m-1 zeros are inserted after each value;

[0037] Step 6: Raise X(f) to the power of m to obtain X m (f);

[0038] Step 7: For X m (f) Perform an inverse fast Fourier transform to obtain x(t);

[0039] Step 8: Extract the peak value of |x(t)|. When k = 0, only one peak value can be extracted, and the peak time is denoted as Δt. (0) When k > 0, 2 can be extracted. k The peak value is taken as the one that is numerically closest to Δt. (k-1) The peak time is denoted as Δt. (k);

[0040] Step 9: If |Δt (k) -Δt (k-1) If | < ε (ε is a positive number that approaches 0 infinitely), then exit the loop; otherwise, let k = k + 1 and return to step 5.

[0041] Step 10: Take the final Δt. (k) This is the time difference between two partial discharge ultrasonic signals.

[0042] In one embodiment, the method includes the following steps:

[0043] Step 1: Microphone a and microphone b respectively acquire the partial discharge ultrasonic signals a(t) and b(t) generated by the same partial discharge power source, and initialize variable k = 0;

[0044] Step 2: Transform a(t) and b(t) to the frequency domain using Fast Fourier Transform to obtain A(f) and B(f);

[0045] Step 3: Perform a weighted summation operation after multiplying the conjugates of A(f) and B(f), i.e.

[0046] Step 4: Let variable m = 2 k ;

[0047] Step 5: Insert zeros into the sequence X(f) according to the rule that m-1 zeros are inserted after each value;

[0048] Step 6: Raise X(f) to the power of m to obtain X m (f);

[0049] Step 7: For X m (f) Perform an inverse fast Fourier transform to obtain x(t);

[0050] Step 8: Extract the peak value of |x(t)|. When k = 0, only one peak value can be extracted, and the peak time is denoted as Δt. (0) When k > 0, 2 can be extracted. k The peak value is taken as the one that is numerically closest to Δt. (k-1) The peak time is denoted as Δt. (k) ;

[0051] Step 9: If |Δt (k) -Δt (k-1) If | < ε (ε is a positive number that approaches 0 infinitely), then exit the loop; otherwise, let k = k + 1 and return to step 5.

[0052] Step 10: Take the final Δt. (k) This is the time difference between two partial discharge ultrasonic signals.

[0053] Appendix Figure 1 Here is an implementation flowchart of one example: Acquire ultrasonic signals from two channels of partial discharge power supply; Perform conjugate multiplication and weighted operation on the two signals after converting them to the frequency domain via Fast Fourier Transform; Perform zero-padding, exponentiation, and inverse Fast Fourier Transform on the obtained discrete sequence in sequence; Extract the peak value of the obtained signal, and exit the operation if the set conditions are met; otherwise, repeat the series of operations such as zero-padding and exponentiation.

[0054] Appendix Figure 2 These represent the partial discharge ultrasonic signals a(t) and b(t) simulated by a double exponential oscillation attenuation signal.

[0055] The expression for the double exponential oscillation decay signal is as follows:

[0056]

[0057] In the formula: A is the signal amplitude; t0 is the initial discharge time; τ c f is the attenuation coefficient; c is the oscillation coefficient; e is the base of the natural logarithm.

[0058] The sampling frequency and resolution of the simulation signal were set to 200kHz and 5μs, respectively. The parameters of the original signals a(t) and b(t) in the simulation are as follows:

[0059]

[0060] Appendix Figure 3 The algorithm of this invention processes signals a(t) and b(t), and then takes the graphs for k = 0, 1, ..., 9. From the graphs, it can be seen that when k = 9, |Δt (9) -Δt (8) |<10 -11 The convergence condition can be considered met, and the final time difference converges to 3.06641μs. Compared with the time difference estimation result of 5μs at the set resolution, it is closer to the true time difference of 3μs, with a time error of only 2.13%. It realizes time difference estimation under super resolution, proving that the algorithm is effective. It breaks the constraint of other methods that the measured time difference is an integer multiple of the sampling time, and improves the measurement accuracy of low-precision equipment.

[0061] This method proposes a super-resolution method for estimating the time difference of ultrasonic signals in partial discharge, resolving the contradiction between insufficient accuracy of low-resolution equipment and high cost and complex manufacturing processes of high-resolution equipment encountered in the miniaturization of existing ultrasonic partial discharge location devices. The main steps of this method are: acquiring ultrasonic signals from two channels of partial discharge sources; performing conjugate multiplication and weighted operations on the two signals after Fast Fourier Transform (FFT) to the frequency domain; sequentially performing zero-padding, exponentiation, and inverse FFT on the resulting discrete sequences; extracting the peak values ​​of the obtained signals, exiting the calculation if a set condition is met, otherwise repeating the zero-padding, exponentiation, and other series of operations. This invention has advantages such as improved resolution of time difference estimation, fast calculation speed, and reduced hardware costs, and has high value in the field of partial discharge detection technology for power equipment (such as transformers and GIS equipment) in power systems for partial discharge location.

[0062] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0063] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for estimating the time difference of partial discharge ultrasonic signals, characterized in that, It includes the following steps, Step 1: Microphone a and microphone b respectively acquire the partial discharge ultrasonic signal a(t) and the partial discharge ultrasonic signal b(t) generated by the same partial discharge power source, and initialize the variable k=0; Step 2: The partial discharge ultrasonic signal a(t) and the partial discharge ultrasonic signal b(t) are transformed to the frequency domain by fast Fourier transform to obtain A(f) and B(f); Step 3: Perform a weighted operation after multiplying the conjugates of A(f) and B(f) to obtain the sequence. ; Step 4: Let variable m = 2 k ; Step 5: Insert zeros into the sequence X(f), where m-1 zeros are inserted after each value; Step 6: Raise the sequence X(f) to the power of m to obtain X m (f); Step 7: For X m (f) Perform an inverse fast Fourier transform to obtain x(t); Step 8: Extract the peak value of |x(t)|. When k=0, only one peak value can be extracted. The peak value time is denoted as Δt. (0) When k > 0, 2 are extracted. k The peak value is taken as the one that is numerically closest to Δt. (k-1) The peak time is denoted as Δt. (k) ; Step 9: If |Δt (k) -Δt (k-1) If | < ε, and ε is a positive number, then exit the loop; otherwise, let k = k + 1 and return to step 5. Step 10: Take the Δt obtained after the last loop exit. (k) The time difference between the two partial discharge ultrasonic signals is denoted as .

2. The method for estimating the time difference of partial discharge ultrasonic signals according to claim 1, characterized in that, ε is a positive number that approaches 0 infinitely.

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