Space partial discharge source positioning method and system

Abstract

The invention relates to a spatial partial discharge source positioning method and system. The method comprises the following steps: synchronously receiving UHF pulse signals excited by a spatial partial discharge source through a plurality of UWB UHF sensors; performing empirical wavelet decomposition on each UHF pulse signal to obtain a series of corresponding wavelet components with different frequency characteristics; extracting a wavelet component of a specified frequency; solving the phase difference between the wavelet component with the specified frequency and every any two ultra-bandwidth ultrahigh-frequency sensors; calculating the time difference between the wavelet component with the specified frequency and every two random ultra-bandwidth ultrahigh frequency sensors; and calculating the space coordinates of the space partial discharge source by using a time arrival method. The system comprises a plurality of distributed ultra-wideband ultrahigh-frequency sensors and a receiver, and each ultra-wideband ultrahigh-frequency sensor is connected with the receiver through a cable. According to the invention, the effectiveness, accuracy and reliability of spatial partial discharge source positioning can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of live state detection of power equipment, and particularly relates to a spatial partial discharge source positioning method and system based on wavelet phase difference. BACKGROUND

[0002] Partial discharge is the main cause of premature failure of power equipment insulation and is also a representation of equipment insulation deterioration. Monitoring partial discharge can timely find possible insulation defects in power equipment and avoid insulation breakdown accidents. In recent years, the ultra high frequency (UHF) method has become the main means for detecting partial discharge of power equipment due to its high sensitivity, strong anti-interference ability, and ability to identify and locate discharge sources.

[0003] Currently, there are two modes for monitoring partial discharge of substation equipment: single-point monitoring method and centralized monitoring method. The former adopts a "one-to-one" monitoring mode, with each sensor monitoring one power equipment; the latter adopts a "one-to-many" monitoring mode, i.e., one sensor (sensor array) monitors multiple power equipment. Since the insulation failure rate of power equipment is low, implementing full coverage monitoring of all equipment requires a large number of monitoring devices, and the actual usage rate of the devices is low; but not implementing full coverage online monitoring will result in monitoring blind spots, posing risks to power system operation. By receiving UHF pulse signals emitted by different equipment partial discharge through ultra wideband UHF sensors, and using a sensor array composed of multiple UHF sensors to monitor and locate the spatial partial discharge source of all station equipment, the problem equipment can be finely detected and diagnosed after the discharge source is found, which can effectively implement insulation monitoring of all substation power equipment and greatly improve the efficiency of insulation monitoring and diagnosis.

[0004] Locating the discharge source is a prerequisite for conducting insulation diagnosis. Currently, the positioning of spatial discharge sources is mainly based on the time arrival method, i.e., receiving UHF electromagnetic wave signals excited by the same discharge source through multiple UHF sensors, calculating the time difference of the signals reaching different sensors, establishing a time arrival equation set, and solving the spatial coordinates of the discharge source. This method is simple in real time, but its solving accuracy depends on the calculation of the time difference, and when the signal amplitude is small or the signal exists aliasing, it is difficult to extract the nanosecond-level wave head time difference, affecting the final positioning result of the discharge source. SUMMARY

[0005] The technical problem solved by the present application is to provide a spatial partial discharge source positioning method to improve the calculation accuracy of the time difference and thus improve the positioning accuracy of the spatial partial discharge source.

[0006] To solve the above technical problems / achieve the above purposes, the technical scheme adopted by the present application is:

[0007] A space partial discharge source positioning method, comprising the following steps:

[0008] Step 1: synchronously receiving UHF pulse signals excited by a space partial discharge source through a plurality of ultra-wideband UHF sensors;

[0009] Step 2: respectively performing empirical wavelet decomposition on each of the UHF pulse signals to obtain a series of wavelet components with different frequency characteristics corresponding to each of the UHF pulse signals;

[0010] Step 3: extracting wavelet components of a specified frequency from the wavelet components corresponding to each of the UHF pulse signals;

[0011] Step 4: calculating the phase difference of the wavelet components of the specified frequency arriving at each of any two of the ultra-wideband UHF sensors;

[0012] Step 5: calculating the time difference of the wavelet components of the specified frequency arriving at each of any two of the ultra-wideband UHF sensors based on the phase difference of the wavelet components of the specified frequency arriving at each of any two of the ultra-wideband UHF sensors;

[0013] Step 6: calculating the spatial coordinates of the space partial discharge source by using the time arrival method based on the time difference of the wavelet components of the specified frequency arriving at each of any two of the ultra-wideband UHF sensors.

[0014] Preferably, in the step 1, the number of the ultra-wideband UHF sensors is at least four.

[0015] Further preferably, in the step 1, the working frequency band of the ultra-wideband UHF sensor is 300-3000 MHz.

[0016] A preferred embodiment is that in the step 2, the empirical wavelet decomposition of the UHF pulse signals comprises the following steps:

[0017] Step 2-1: determining the scale and scaling parameters for decomposing the UHF pulse signals;

[0018] Step 2-2: decomposing the UHF pulse signals into pre-defined local bandpass signals based on the scale and scaling parameters;

[0019] Step 2-3: performing Hilbert transform on each of the bandpass signals to obtain the corresponding time-frequency diagram;

[0020] Step 2-4: Summation or averaging is performed on the time-frequency diagram according to the local characteristics, and then the empirical wavelet decomposition result of the UHF pulse signal is obtained.

[0021] Further, in step 2-2, the decomposition of the UHF pulse signal is realized by solving the adaptive boundary of the local bandpass signal.

[0022] According to one embodiment of the present application, in step 4, the phase difference of any two UWB sensors is analyzed based on the carrier technology.

[0023] In one embodiment, in step 5, the time difference of the two UWB sensors is calculated using the phase difference of the two UWB sensors and the specified frequency.

[0024] Preferably, in step 6, an equation set is established using the time arrival method, and the spatial coordinates of the spatial partial discharge source are obtained by solving the equation set through iterative calculation.

[0025] The present application also provides a spatial partial discharge source positioning system with high detection accuracy, and the scheme is as follows:

[0026] A spatial partial discharge source positioning system, comprising a plurality of distributed UWB sensors and a receiver, each of the UWB sensors being connected to the receiver through a cable, the UWB sensors being used to synchronously receive UHF pulse signals excited by a spatial partial discharge source and transmit the signals to the receiver, the receiver being used to perform empirical wavelet decomposition on each of the UHF pulse signals to obtain a series of wavelet components with different frequency characteristics corresponding to each of the UHF pulse signals, extract a wavelet component with a specified frequency from the wavelet components corresponding to each of the UHF pulse signals, calculate the phase difference of the wavelet component with the specified frequency arriving at any two of the UWB sensors, calculate the time difference of the wavelet component with the specified frequency arriving at any two of the UWB sensors, and calculate the spatial coordinates of the spatial partial discharge source using the time arrival method. The length of the cable is equal or the length difference of the cable is calibrated.

[0027] Thanks to the above technical solution, the present application has the following advantages compared with the prior art: the present application can improve the effectiveness, accuracy and reliability of spatial partial discharge source positioning. BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a flowchart of the spatial partial discharge source positioning method of the present application. Figure 1 FIG. 2 is a flowchart of the spatial partial discharge source positioning method of the present application.

[0029] FIG. 3 is a schematic diagram of the spatial partial discharge source positioning system of the present application. Figure 2This is a schematic diagram of the space partial discharge power supply positioning system of the present invention receiving UHF pulse signals.

[0030] Appendix Figure 3 This is a schematic diagram of phase calculation based on a carrier wave in the spatial partial discharge power source positioning method of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] Example 1: Deploying a space local discharge source positioning system for locating space local discharge sources. (See attached diagram) Figure 2 As shown, the system includes multiple distributed ultra-wideband (UHF) sensors and a receiver. The multiple UHF sensors form an UHF sensor array, and each UHF sensor is connected to the receiver via a cable. In this embodiment, there are at least four UHF sensors, numbered 1, 2, ..., N. These UHF sensors are used to synchronously receive UHF pulse signals excited by the space partial discharge source and transmit them to the receiver. Each UHF sensor is connected to the receiver via a coaxial cable, with coaxial cables of equal length selected or the length difference between the coaxial cables calibrated. The receiver performs empirical wavelet decomposition on each UHF pulse signal to obtain a series of wavelet components with different frequency characteristics corresponding to each UHF pulse signal. It extracts wavelet components of a specified frequency from the wavelet components corresponding to each UHF pulse signal, calculates the phase difference of the wavelet components of the specified frequency arriving at any two UHF sensors, calculates the time difference of the wavelet components of the specified frequency arriving at any two UHF sensors, and uses the time-of-arrival method to calculate the spatial coordinates of the space partial discharge source.

[0033] The space partial discharge power source positioning method used in the above-mentioned space partial discharge power source positioning system is shown in the attached figure. Figure 1 As shown, it includes the following steps:

[0034] Step 1: Simultaneously receive the UHF pulse signal (discharge signal) excited by the space partial discharge power source using multiple ultra-wideband ultra-high frequency sensors.

[0035] In this step, the UHF pulse signals excited by the source excitation of partial discharge are synchronously received by an array of N ultra-wideband UHF sensors and sent to the receiver. Each ultra-wideband UHF sensor is required to be omnidirectional in the ultra-wideband frequency range of 300-3000 MHz.

[0036] Step 2: Empirical wavelet decomposition is performed on each UHF pulse signal to obtain a series of wavelet components with different frequency characteristics corresponding to each UHF pulse signal.

[0037] In this step, the UHF pulse signals received by each ultra-wideband UHF sensor need to be decomposed by EWT. EWT (Empirical Wavelet Transform) is an adaptive signal decomposition method based on the signal itself, which can decompose the signal into a series of wavelet components with different frequency characteristics. Taking a certain ultra-wideband UHF sensor as an example, the discharge signal f(t) collected by the sensor is decomposed by EWT as follows:

[0038] f(t) = A1sint + A2sin2t + … + A m sinmt

[0039] The implementation of this step is as follows:

[0040] Step 2-1: Initialization, determine the scaling and scaling parameters for decomposing the UHF pulse signal;

[0041] Step 2-2: Based on the scaling and scaling parameters, decompose the UHF pulse signal into predefined local bandpass signals; specifically, decompose the UHF pulse signal by solving the adaptive boundary of the local bandpass signal;

[0042] Step 2-3: Perform Hilbert transform on each bandpass signal to obtain the corresponding time-frequency graph;

[0043] Step 2-4: Sum or average the local features on the time-frequency graph to obtain the time-frequency graph of the original discharge signal, and then obtain the empirical wavelet decomposition result of the UHF pulse signal, realizing signal decomposition.

[0044] Step 3: Extract the wavelet component with a specified frequency from the wavelet components corresponding to each UHF pulse signal.

[0045] In this step, the decomposed wavelet components corresponding to the signals received by different ultra-wideband UHF sensors form a wavelet component waveform library, and the wavelet signal of a certain frequency in the waveform library is extracted to obtain the wavelet signal base of a certain frequency of the signals received by each ultra-wideband UHF sensor. For example, the wavelet signal set with angular frequency k is extracted as:

[0046] S(t)1=B1sinkt

[0047] S(t)2=B2sinkt

[0048] …

[0049] S(t) N =B N sinkt

[0050] Step 4: Calculate the phase difference between wavelet components of a specified frequency arriving at any two ultra-wideband ultra-high frequency sensors.

[0051] In this step, based on carrier technology, the phase difference between any two ultra-wideband ultra-high frequency sensors is analyzed, that is, the carrier phase difference at which the discharge signal arrives at each ultra-wideband ultra-high frequency sensor is analyzed and calculated. (See attached...) Figure 3 As shown, assume the phases of the signal with frequency f are Φ1, Φ2, Φ3, ..., Φ4. N And accordingly, calculate the phase difference of the signals received by different ultra-wideband ultra-high frequency sensors. For example, the phase difference ΔΦ between the signals of sensor 1 and sensor 2. 12 =2nπ+(Φ1-Φ2), where n is the integer cycle difference between the signal to sensor 1 and sensor 2.

[0052] Step 5: Based on the phase difference of the wavelet component at the specified frequency arriving at any two UHF sensors, calculate the time difference of the wavelet component at the specified frequency arriving at any two UHF sensors.

[0053] Based on step 4, the time difference between the two ultra-wideband ultra-high frequency (UHF) sensors is calculated using the phase difference and a specified frequency, converting the phase difference of the signals received by different sensors into a time difference. Therefore, the signal time difference between sensor 1 and sensor 2 is: Δt 12 =ΔΦ 12 / 2πf.

[0054] Step 6: Based on the time difference between the arrival times of wavelet components at a specified frequency at any two UHF sensors, calculate the spatial coordinates of the spatial local discharge source using the time arrival method.

[0055] Based on step 5, a system of equations is established using the time arrival method, and then the spatial coordinates of the local discharge source are calculated.

[0056] Assuming the coordinates (x0, y0, z0) of the spatial local discharge source are unknown, and the coordinates of each ultra-wideband ultra-high frequency sensor are (x1, y1, z1), (x2, y2, z2), ..., (x... N ,y N ,z NIt is known that the electromagnetic wave propagation speed is c, then:

[0057]

[0058] …

[0059]

[0060] The above equation set is established to solve the spatial coordinates of the space partial discharge source. In the present scheme, since the integral cycle difference n of the signal arriving at different sensors cannot be determined by calculation in the carrier phase difference calculation process, but the spatial positions of the sensors and the substation equipment are respectively determined, the value range of the integral cycle difference n is determined, and the above equation set has only one solution, so the n value combination can be obtained by iterative calculation of the computer to solve the equation set, and then the spatial coordinates (x0, y0, z0) of the space partial discharge source are solved.

[0061] Based on the above steps, the coordinates of the space partial discharge source can be solved using a wavelet signal base of a certain frequency.

[0062] In order to improve the accuracy of the calculation, the coordinates of the space partial discharge source can also be solved using wavelet signal bases of different frequencies, and the calculation results can be statistically analyzed to obtain the final spatial coordinates of the space partial discharge source. That is, in step 3, multiple wavelet components of specified frequencies are extracted and multiple corresponding spatial coordinates (x0, y0, z0) of the space partial discharge source are calculated, and then the spatial coordinates (x0, y0, z0) of the multiple space partial discharge sources are statistically analyzed to obtain the final spatial coordinates of the space partial discharge source.

[0063] On the basis of solving the spatial coordinates of the space partial discharge source, the positioning results are compared and analyzed with the distribution of the actual equipment in combination with the layout of the substation equipment, and the positioning results are finally output.

[0064] The present scheme converts the calculation of the nanosecond pulse wave head into the calculation of the phase difference of the sinusoidal wave, improves the reliability of the calculation, and obtains the spatial coordinates of the discharge source by empirically decomposing the discharge broadband signal and calculating the phase difference of the wavelet of different frequencies arriving at each sensor.

[0065] The present technical scheme has the following advantages compared with the prior art:

[0066] 1. The present scheme proposes a wavelet phase difference based space partial discharge positioning method for the commonly used discharge source space time difference arrival method, avoids the problems of difficult extraction of the signal wave head and inability to identify the mixed signal, and converts the calculation of the signal wave head time into the calculation of the phase difference of the sinusoidal signal, thereby improving the effectiveness of the calculation.

[0067] 2. This scheme uses different frequency wavelet bases to calculate the coordinates of the discharge source respectively, and statistically processes the calculation results. Compared with the single result analysis of the traditional time difference positioning method, the error of positioning calculation can be obviously reduced, and the reliability of positioning can be improved;

[0068] 3. Compared with the traditional space positioning which only analyzes the time domain characteristics of the signal, this patent processes the signal through EWT to obtain the time-frequency characteristics of different frequencies of the discharge, which is helpful to identify and exclude the interference of the substation corona, wireless communication signal and the like, and improves the effectiveness of the discharge monitoring and positioning.

[0069] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for locating a source of spatial partial discharge, the method comprising: The method comprises the following steps: ​ Step 1: synchronously receiving UHF pulse signals excited by a spatial partial discharge source through a plurality of ultra-wideband UHF sensors; Step 2: respectively performing empirical wavelet decomposition on each UHF pulse signal to obtain a series of wavelet components with different frequency characteristics corresponding to each UHF pulse signal; Step 3: extracting a wavelet component with a specified frequency from the wavelet components corresponding to each UHF pulse signal; Step 4: calculating the phase difference of the wavelet component with the specified frequency arriving at any two of the ultra-wideband UHF sensors; Step 5: calculating the time difference of the wavelet component with the specified frequency arriving at any two of the ultra-wideband UHF sensors based on the phase difference of the wavelet component with the specified frequency arriving at any two of the ultra-wideband UHF sensors; Step 6: calculating the spatial coordinates of the spatial partial discharge source by using the time arrival method based on the time difference of the wavelet component with the specified frequency arriving at any two of the ultra-wideband UHF sensors.

2. The method of claim 1, wherein: In the step 1, the number of the ultra-wideband UHF sensors is at least four.

3. The method of claim 1, wherein: In the step 1, the working frequency band of the ultra-wideband UHF sensor is 300-3000 MHz.

4. The method of claim 1, wherein: In the step 2, the empirical wavelet decomposition on the UHF pulse signal comprises the following steps: Step 2-1: determining the scale and scaling parameters for decomposing the UHF pulse signal; Step 2-2: decomposing the UHF pulse signal into predefined local band signals based on the scale and scaling parameters; Step 2-3: performing Hilbert transform on each band signal to obtain a corresponding time-frequency graph; Step 2-4: summing or averaging the local characteristics on the time-frequency graph to obtain the empirical wavelet decomposition result of the UHF pulse signal.

5. The method of claim 1, wherein: In the step 2-2, the decomposition of the UHF pulse signal is realized by solving the adaptive boundary of the local band signal.

6. The method of claim 1, wherein: In the step 4, the phase difference of any two of the ultra-wideband UHF sensors is analyzed based on the carrier wave technology.

7. The method of claim 1, wherein: In the step 5, the time difference of the two ultra-wideband UHF sensors is calculated based on the phase difference of the two ultra-wideband UHF sensors and the specified frequency.

8. The method of claim 1, wherein: In the step 6, an equation set is established by using the time arrival method, and the spatial coordinates of the spatial partial discharge source are obtained by solving the equation set through iteration calculation.

9. A spatial partial discharge source localization system characterized by: The space partial discharge source positioning system comprises a plurality of distributed ultra-wideband UHF sensors and a receiver, each of the ultra-wideband UHF sensors is connected to the receiver through a cable, the ultra-wideband UHF sensor is used for synchronously receiving a UHF pulse signal excited by a space partial discharge source and transmitting to the receiver, the receiver is used for respectively performing empirical wavelet decomposition on each of the UHF pulse signals to obtain a series of wavelet components with different frequency characteristics corresponding to each of the UHF pulse signals, extracting a wavelet component with a specified frequency from the wavelet components corresponding to each of the UHF pulse signals, calculating a phase difference of the wavelet component with the specified frequency reaching any two of the ultra-wideband UHF sensors, calculating a time difference of the wavelet component with the specified frequency reaching any two of the ultra-wideband UHF sensors, and calculating a space coordinate of the space partial discharge source by using a time arrival method.

10. The system for locating partial discharges in space according to claim 9, characterized in that: The lengths of the cables are selected to be equal or the lengths of the cables are calibrated.

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