Power distribution network fault accurate positioning method, device and system based on traveling wave principle

Abstract

The invention relates to the technical field of power system fault positioning, in particular to a power distribution network fault accurate positioning method, device and system based on the traveling wave principle, and the method comprises the steps: deploying traveling wave detection equipment at two ends of a certain section of line of a power distribution network, and enabling the traveling wave detection equipment to be used for synchronously collecting potential fault traveling wave signals; analyzing based on the acquired potential fault traveling wave signal, and screening out a fault traveling wave; in the time union set of the local time windows at the two ends, marking the fault traveling wave with the maximum peak value in the single end as a direct wave, analyzing the waveform similarity between the direct wave and the fault traveling wave arriving after the direct wave, and screening out a reflected wave according to the peak value difference; and based on the arrival time of the direct waves and the reflected waves at the two ends, calculating the distance from the fault point to the two ends of the line through a positioning formula to position the fault point. The invention aims to improve the positioning precision of the fault point in the power distribution network by analyzing the distribution characteristics of the pseudo traveling wave signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system fault positioning, in particular to a distribution network fault accurate positioning method, device and system based on the principle of traveling wave. BACKGROUND

[0002] The distribution network is a key channel for realizing the power generation end to the power consumption end. In order to ensure the orderly progress of daily production and life, it is necessary to ensure the safe and stable operation of the distribution network. For the positioning of the daily distribution network fault, it depends on the impedance measurement method and the signal injection method. The impedance measurement method is easily limited by the line load condition and has measurement deviation. The signal injection method needs to be measured when the transmission line is powered off, which interferes with the normal operation of the distribution network. The basic principle of the traveling wave method for realizing line fault positioning is that when the line fails, a traveling wave (transient electromagnetic wave) will be generated at the fault point and transmitted to both ends along the line, so that the accurate positioning of the fault point can be realized by monitoring the arrival time of the traveling wave signal, and the overall positioning accuracy is high and the universality is strong.

[0003] In some existing research on traveling wave fault positioning, a method is proposed to realize accurate positioning of the wave head by decomposing and enhancing the high frequency of the traveling wave signal, and the positioning error is small in the result analysis of the simulation. However, in the actual process, the towers and branch points on the distribution line may produce reflection and refraction of the traveling wave signal, so that the monitored traveling wave has multiple pseudo traveling wave signals, which will interfere with the analysis of the real fault traveling wave signal. If the fault traveling wave is not accurately identified, it will cause deviation in the positioning of the distribution network fault point. SUMMARY

[0004] In order to solve the above technical problems, the purpose of the present application is to provide a distribution network fault accurate positioning method, device and system based on the principle of traveling wave, and the technical solution is as follows: In the first aspect, the present application provides a distribution network fault accurate positioning method based on the principle of traveling wave, which comprises the following steps: Deploy traveling wave detection devices at both ends of a certain line of the distribution network for synchronous acquisition of potential fault traveling wave signals; Use the main frequency energy proportion in the frequency domain response of the potential fault traveling wave signal and the range of all envelope energy intensity proportions to construct the frequency domain noise point estimation of the potential fault traveling wave signal, and combine the rising edge time in the potential fault traveling wave signal to calculate the traveling wave accuracy; use the traveling wave accuracy to screen out the fault traveling wave in the preset local time window of the potential fault traveling wave signal; In the time and centralization of the two ends of the local time window, mark the fault traveling wave with the largest peak value in the single end as a direct wave, and analyze the waveform similarity and peak difference of the direct wave and the fault traveling wave arriving after it to screen out the reflected wave; Based on the arrival time of the direct wave and the reflected wave at both ends, the distance from the fault point to both ends of the line is calculated by a positioning formula to locate the fault point.

[0005] Preferably, the judgment method of the potential fault traveling wave signal is: Obtaining the baseline of the signal received by the single detection end; Taking the electrical signal greater than the baseline at continuous multiple sampling time points as the fluctuation signal; Taking two fluctuation signals with a time interval less than a preset time period as a potential fault traveling wave signal.

[0006] Preferably, the frequency domain noise point estimate is negatively correlated with the extreme difference of the main frequency energy and the envelope energy intensity proportion.

[0007] Preferably, the traveling wave accuracy is negatively correlated with the rising edge time and the frequency domain noise point estimate.

[0008] Preferably, the determination method of the rising edge time is: Obtaining the maximum value of the potential fault traveling wave signal after curve fitting; Obtaining the minimum value closest to the maximum value before the time corresponding to the maximum value in the fitted curve; Taking the time interval between the minimum value and the maximum value as the rising edge time of the potential fault traveling wave signal.

[0009] Preferably, the screening method of the fault traveling wave is: threshold segmentation is performed on the traveling wave accuracy of all potential fault traveling wave signals in a local time window; and the potential fault traveling wave signal with a traveling wave accuracy greater than or equal to the segmentation threshold is marked as a fault traveling wave.

[0010] Preferably, the length of the preset local time window is 5 times the time length of the potential fault traveling wave signal from the single-end transmission of the line to the other-end transmission; and when the number of the fault traveling waves screened in the local time window is less than 3, the local time window is not analyzed.

[0011] Preferably, the screening method of the reflected wave is: Using the waveform similarity and peak difference between the direct wave and the fault traveling wave arriving after the direct wave in the time set of the single end, a reflected wave screening value of each fault traveling wave arriving after the direct wave is constructed; Taking the fault traveling wave with the maximum reflected wave screening value of all the fault traveling waves arriving after the direct wave as the reflected wave.

[0012] In the second aspect, the embodiments of the present application also provide a power distribution network fault accurate positioning device based on the traveling wave principle, the device stores a computer program, and the computer program is executed by a processor to realize the power distribution network fault accurate positioning method based on the traveling wave principle.

[0013] In a third aspect, the embodiments of the present application further provide a power distribution network fault accurate positioning system based on the traveling wave principle, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of the power distribution network fault accurate positioning method based on the traveling wave principle when executing the computer program.

[0014] As can be seen from the above embodiments, the power distribution network fault accurate positioning method, device and system based on the traveling wave principle provided by the embodiments of the present application have at least the following beneficial effects: Compared with the traditional way of realizing fault point positioning by calculating the traveling wave signal based on signal decomposition, the method is prone to deviation in identifying the traveling wave signal caused by the pseudo traveling wave signal generated by the impedance discontinuous point and the electromagnetic noise interference. The present application focuses on the frequency energy distribution and rising edge jump deviation of the traveling wave signal and noise interference, reduces the influence of noise interference, further realizes the screening of the fault traveling wave signal based on the energy attenuation and interference evaluation of the fault traveling wave, obtains the arrival time of the direct wave and reflected wave, and realizes the positioning of the fault point based on the positioning equation set, which can significantly improve the positioning accuracy of the fault point and improve the fault troubleshooting efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0016] Figure 1 The traveling wave fault positioning model provided by one embodiment of the present application is shown in the schematic diagram. Figure 2 The traveling wave transmission model provided by one embodiment of the present application is shown in the schematic diagram. Figure 3 The step flowchart of the power distribution network fault accurate positioning method based on the traveling wave principle provided by one embodiment of the present application is shown in the schematic diagram. Figure 4 The connection point interference model provided by one embodiment of the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0017] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined object, the specific embodiments, structure, features and effects of the method, device and system for accurately locating faults in distribution network based on the principle of traveling wave according to the present application are described in detail as follows in combination with the drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined and limited, such as the term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the circuit structure, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such article or device. Without more limitation, the element limited by the phrase "including one" does not exclude the presence of another identical element in the article or device including the element. In addition, the term "and / or" used herein includes any and all combinations of one or more related listed items. All technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the present application belongs.

[0019] The specific scheme of the method, device and system for accurately locating faults in distribution network based on the principle of traveling wave provided by the present application is described in detail below in combination with the drawings.

[0020] Among the operation faults of the distribution network line, the proportion of short circuit fault can reach 90%, and the short circuit fault is more threatening to the distribution network line, so the fault in the present scheme is mainly the line short circuit fault. When the distribution network line has a short circuit fault, a fault traveling wave will be generated from the fault point and propagate to both ends of the line. When there is a point of impedance discontinuity on the line, refraction and reflected traveling wave signals will be generated, so that the fault point on the distribution network line can be accurately located by detecting the traveling wave signals.

[0021] The specific traveling wave fault location model is shown in Figure 1 . Wherein when the two ends of the line are MN, if the F point on the distribution network line has a line fault, a fault traveling wave will be generated and propagate to both ends.

[0022] The specific traveling wave transmission model is shown in Figure 2As shown, for the fault traveling wave signal generated at the F point, direct straight waves FM1 and FN1 will be generated to the two ends, and the corresponding arrival times are t1 and t2, respectively. Due to the impedance discontinuity at the end point, corresponding reflected waves will be generated at this time. Taking the M end as an example, the reflected wave generated at the M end, a part of which is directly refracted to the N end through the fault point, is recorded as MN1, and the corresponding arrival time is t3. Due to the impedance discontinuity at the fault point F, a secondary reflected wave traveling wave is generated, which is recorded as FM2, and the corresponding arrival time is t4. Similarly, for the N end, there are corresponding straight traveling waves NM1 and secondary reflected traveling waves FN2, and the corresponding arrival times are t5 and t6, respectively.

[0023] For the traveling waves detected at the two ends, FM1, MN1 and FM2 are the reflected waves and refracted waves of the fault traveling wave from the fault point to the M end, and therefore there is a certain similarity between them. Similarly, FN1, NM1 and FN2 are the reflected waves and refracted waves of the fault traveling wave from the fault point to the N end, and therefore there is a certain similarity between them.

[0024] In addition, the line as a whole is relatively long relative to the line MN at both ends, usually more than 100 km, so there may be line connections, branch points and towers in the middle of the line, which may cause the impedance of the line at these connection points to have certain differences. For these difference points, corresponding traveling wave signals will also be generated, which are called pseudo-traveling waves, which will interfere with the real traveling wave signals generated by the fault point.

[0025] Please refer to Figure 3 which shows the step flowchart of the power distribution network fault accurate positioning method based on the traveling wave principle provided by an embodiment of the application, and the method comprises the following steps: S1: Deploy traveling wave detection devices at both ends of a certain section of the power distribution network for synchronous acquisition of potential fault traveling wave signals.

[0026] In order to accurately locate the fault between the power distribution network, for the two end points of a certain section of the power distribution network, corresponding traveling wave detection devices are deployed, so that the traveling wave signals in the operation process of the power distribution network can be continuously acquired. Since the traveling wave generated by the fault point is actually a transient electromagnetic wave, in order to realize complete acquisition of the traveling wave signal, and since the sampling interval of the traveling wave detection device is ns level, the sampling frequency is set to 1 GHz in this embodiment.

[0027] In addition, in order to realize accurate positioning of the arrival time of the traveling wave, the traveling wave detection devices at both ends of the MN need to be time-synchronized, so that in the present scheme, GNSS is used as a time source, and the time synchronization protocol of hardware and PTP is used to synchronize the traveling wave detection devices at both ends of the power distribution line. Among them, the 4G network transmission module in the traveling wave detection device can transmit the collected traveling wave signal to the fault location system, and analyze the traveling wave signals at both ends of the MN in the cloud fault location system to realize the positioning of the real fault point.

[0028] Further, a single detection end continuously monitors the traveling wave signal on the power distribution network line, but for the fault traveling wave signal, it is actually a transient electromagnetic wave. In an ideal case, when no traveling wave signal arrives, the electrical signal of the detection end is zero. Only when the traveling wave signal arrives, the electrical signal can be detected. The traveling wave signal is reflected to the line by the detection end. When the reflected / refracted fault traveling wave arrives again, the traveling wave electrical signal can be detected.

[0029] However, in the actual process, it is easy to be affected by electromagnetic interference and waveform distortion in the line, so that the electrical signal can be detected when no signal arrives at the detection end, which interferes with the real fault traveling wave. Therefore, it is necessary to analyze the distribution characteristics of the traveling wave signal and the noise interference signal to accurately evaluate the fault traveling wave signal.

[0030] Accordingly, the present application first uses a baseline correction algorithm to obtain the baseline of the signal received by a single detection end. If the signal strength at any sampling time in the received signal is greater than the baseline, it indicates that there is an electrical signal at this time. If the electrical signals of the continuous M sampling times are all greater than the baseline, the electrical signals of the continuous M sampling times are regarded as wave signals, indicating that there is obvious signal fluctuation at this time. And if the time interval between the two continuous wave signals is less than a preset time period, it is determined that the two wave signals correspond to a potential fault traveling wave signal. In this embodiment, the preset time period is 30% of the traveling wave signal according to historical experience. At this time, the potential fault traveling wave signal may be a real fault traveling wave, a pseudo traveling wave or noise interference. Therefore, the corresponding potential fault traveling wave signal set is obtained for the detection ends on both sides of the power distribution network. It should be noted that the sampling frequency of the present scheme is high, so the value of M is preferably between 100 and 300. In the preferred embodiment, the value of M is set to 100.

[0031] S2: Analyzing the collected potential fault traveling wave signal to screen out the fault traveling wave.

[0032] When a short-circuit fault occurs in the power distribution line, a traveling wave signal will be generated and transmitted to both ends. When the traveling wave signal reaches the end point, it will be received by the traveling wave detection device. The overall traveling wave signal will exhibit a pulse peak, which will gradually decay when it reaches the peak. However, in actual practice, the electromagnetic noise in the line and waveform distortion may produce false interference signals, which will interfere with the identification of the traveling wave signal. Therefore, the distribution of the traveling wave signal needs to be combined to evaluate the detected traveling wave signal.

[0033] In S201, the main frequency energy proportion in the frequency domain response of the potential fault traveling wave signal and the range of the proportion of all envelope energy intensities are used to construct the frequency domain noise point estimation of the potential fault traveling wave signal.

[0034] For the detected potential fault traveling wave signal, it may be a traveling wave signal or an interference signal formed by noise. If it is a traveling wave signal, it is usually a real traveling wave signal mixed with noise, but the energy intensity of the overall fault traveling wave signal will be significantly stronger than that of the noise signal. If it is an interference noise signal, it will exhibit strong randomness and be affected by white noise, which will make the random interference noise have no obvious frequency distribution, i.e., it exists in each frequency range.

[0035] Based on the above analysis, for a single potential fault traveling wave signal, short-time Fourier transform is performed to obtain the corresponding frequency domain response. In the frequency domain signal, each envelope in the frequency domain response is obtained by envelope extraction. The frequency corresponding to the maximum frequency domain energy intensity in a single envelope is referred to as a frequency component, and the frequency corresponding to the maximum frequency domain energy intensity in all envelopes is referred to as a main frequency. Thus, all frequency components in the entire frequency domain signal and the energy intensities corresponding to the frequency components are obtained.

[0036] Accordingly, the frequency domain noise point estimation of a single potential fault traveling wave signal is constructed. The main frequency energy proportion in the frequency domain response of the potential fault traveling wave signal and the range of the proportion of all envelope energy intensities are used to construct the frequency domain noise point estimation of the potential fault traveling wave signal.

[0037] The frequency domain noise point estimation is negatively correlated with the range of the proportion of the main frequency energy and all envelope energy intensities, respectively.

[0038] It can be understood that a negative correlation means that the dependent variable will decrease as the independent variable increases, and the dependent variable will increase as the independent variable decreases. The actual application determines this, and the present application does not have special limitations.

[0039] Specifically, in this embodiment, the calculation expression of the frequency domain noise point estimation A of a single potential fault traveling wave signal is: In the formula, A represents the frequency domain noise point estimation of a single potential fault traveling wave signal, a ratio of a main frequency energy, a ratio of envelope energy intensity, and a rising edge time of the potential fault traveling wave signal. a range value of a ratio of envelope energy intensity of all envelope energy intensity in a single potential fault traveling wave signal, in %. It is to be noted that the ratio of main frequency energy is obtained by a ratio of main frequency component energy intensity and a sum of energy intensity of all frequency components; the ratio of envelope energy intensity is obtained by a ratio of current envelope energy intensity (integration of all frequencies in the envelope) and all envelope energy intensity.

[0040] It is to be noted that in the frequency domain noise estimation, in the potential fault traveling wave signal formed by noise, since the noise has no obvious frequency tendency, it has certain energy at each frequency, so the range value of the ratio of main frequency energy and the ratio of envelope energy intensity of the frequency domain response is small. On the contrary, in the potential fault traveling wave signal formed by fault traveling wave, since there is a real fault traveling wave, the fault traveling wave is an impact signal formed by line short circuit, so the energy ratio of the main frequency is high, and the range value of the ratio of envelope energy intensity is large, so the value of the corresponding frequency domain noise estimation is small.

[0041] S202, and combining the rising edge time in the potential fault traveling wave signal, the traveling wave accuracy is calculated.

[0042] In the above analysis, the analysis of the potential fault traveling wave signal is mainly realized based on the frequency domain characteristics of the fault traveling wave and noise interference, so as to evaluate the misjudgment caused by the fault traveling wave and noise interference. In addition, noise of some specific frequencies may be generated due to the influence of external line transmission conditions, such as severe thunderstorm, strong wind disturbance, etc. At this time, directly based on the frequency domain analysis, the noise in the potential fault traveling wave signal may be misjudged as an actual fault traveling wave signal, therefore, the distribution of both needs to be further analyzed.

[0043] For a real fault traveling wave, its essence is a transient signal generated due to line short circuit, so the traveling wave signal can often generate a steep rising edge limited by short circuit, and the rising time is different based on the impedance state of short circuit, and the basic value range is between 10~50us. For noise, the amplitude of high frequency noise is usually small, which cannot cause the signal to generate a steep rising edge, that is, there may be high energy low frequency noise, but the rising time caused by low frequency noise is much larger than that of the fault traveling wave.

[0044] According to the above analysis, the traveling wave accuracy of the potential fault traveling wave signal is constructed by combining the rising edge time in the potential fault traveling wave signal and the frequency domain noise estimation of the potential fault traveling wave signal.

[0045] The traveling wave accuracy is negatively correlated with the rising edge time and the frequency domain noise estimation, respectively.

[0046] The determination method of the rising edge time is that, for a single potential fault traveling wave signal, a fitting curve of the potential fault traveling wave signal is obtained through a curve fitting algorithm, a maximum value of the fitting curve is acquired, and a minimum value closest to the maximum value before the time corresponding to the maximum value in the fitting curve is obtained. The time interval between the minimum value and the maximum value is regarded as the rising edge time of the potential fault traveling wave signal. In the embodiment, the least square method is used for curve fitting of the potential fault traveling wave signal, and the least square method is a known technology and will not be described herein.

[0047] Specifically, in the embodiment, the calculation expression of the traveling wave accuracy B of the single potential fault traveling wave signal is: In the formula, B represents the traveling wave accuracy of the single potential fault traveling wave signal, Tref represents a preset reference rising edge time, and the unit is us. The experience value can be determined through the rising edge time of the historical fault traveling wave. In the embodiment, Tref is set to 0.5 us. , A represents the frequency domain noise point estimation of the single potential fault traveling wave signal, and the unit is dimensionless.

[0048] It should be noted that in the traveling wave accuracy analysis, the deviation of the rising edge time of the potential fault traveling wave signal from the conventional fault traveling wave rising edge is mainly considered. For the low-frequency rising edge formed by noise, a longer rising time is often needed, and the deviation from the reference value is large. Therefore, the value of the traveling wave accuracy obtained is small. On the contrary, for the fault traveling wave signal, the deviation of the corresponding rising edge time from the reference value is small. Therefore, the ratio of the two is closer to 1, and the value of the traveling wave accuracy obtained is large.

[0049] S203, using the traveling wave accuracy to screen the fault traveling wave in the preset local time window of the potential fault traveling wave signal.

[0050] Through the above method, the traveling wave accuracy corresponding to the single potential fault traveling wave signal can be obtained, and the conditions that the potential fault traveling wave signal is noise interference and a real fault traveling wave can be analyzed.

[0051] Since the arrival time of multiple single potential fault traveling wave signals needs to be combined for comprehensive analysis when judging the fault point, in order to avoid that the analysis time window is too long, the potential fault traveling wave signal when analyzing the fault point is limited in a local time window in the application.

[0052] For the potential fault traveling wave signal obtained from a single detection end, a preset local time window containing the potential fault traveling wave signal is divided, i.e. a local time window divided before the last sampling time of the potential fault traveling wave signal obtained from the single detection end, and the length of the local time window is set to 5 times the length of the potential fault traveling wave signal propagating from the single detection end to the other end in the embodiment.

[0053] The purpose of dividing the local time window of 5 times the length is that the fault traveling wave will be accompanied by energy attenuation in the process of refraction and reflection in the line, and will be almost masked by noise after three refractions and reflections. Therefore, the analysis in the local time window of 5 times the length can reduce the value range and improve the detection efficiency.

[0054] For the local time window of a certain potential fault traveling wave signal of the current detection end, the traveling wave accuracy corresponding to multiple potential fault signals in the local time window is obtained, and then the threshold segmentation of all traveling wave accuracies in the local time window is obtained by using the Otsu threshold method to perform screening. The potential fault traveling wave with a traveling wave accuracy greater than or equal to the segmentation threshold is marked as a fault traveling wave, and the others are marked as interference traveling waves. The Otsu threshold method is a known technology and will not be described again.

[0055] In addition, if the number of fault traveling waves screened in the local time window of the current potential fault traveling wave signal is less than 3, it indicates that the fault traveling wave is not completely propagated in the line at this time, which is not sufficient for fault location. Therefore, the local time window is not analyzed, and the time is sequentially delayed, the local time window of the next potential fault traveling wave signal is obtained, and the condition is met. At this time, it is indicated that there is indeed a complete propagation of the fault traveling wave signal in the local time window, so as to realize the fault point positioning.

[0056] S3: In the time of the local time window of both ends, the fault traveling wave with the maximum peak value in the single end is marked as a direct wave, and the waveform similarity and peak difference of the direct wave and the fault traveling wave arriving after the direct wave are analyzed to screen out a reflected wave.

[0057] The focus of the analysis process in step S2 is to analyze the misjudgment caused by the fault traveling wave and noise interference, so as to obtain the corresponding fault traveling wave in the local time window. However, in the actual process, there may be a connection point in the line due to the long length of the line, which presents impedance discontinuity at the connection point. At this time, additional reflected traveling waves will be generated. These traveling wave signals generated due to impedance discontinuity are pseudo traveling waves, which need to be identified to avoid interference with fault point positioning.

[0058] In the embodiment, the connection point interference model is as follows Figure 4As shown, there is a connection point P between the MFs, and at the connection point P, a reflected wave FPN is generated due to impedance discontinuity. Similarly, the reflected wave MN1 of the M terminal reaches P, and at this time, a reflected wave PM of P is generated. The reflected waves FPN and PM are both caused by the connection point, and thus are called pseudo-traveling waves.

[0059] In a conventional positioning process, the arrival time of the direct wave and the reflected wave is directly calculated, for example, for the M terminal, to calculate the distance from the M terminal to the fault point. If there is a pseudo-traveling wave at this time, the reflected wave will arrive earlier, thereby interfering with the analysis of the real positioning of the fault point.

[0060] Through the above analysis, the local time window of the potential fault traveling wave signal at the M terminal and the local time window of the potential fault traveling wave signal at the N terminal can be obtained, respectively. Since there is a time difference in the arrival of the fault traveling wave at the two terminals, the time union of the local time windows at the two terminals is obtained. In the time union of the local time windows, there are real fault traveling wave signals and pseudo-traveling wave signals.

[0061] When a short circuit occurs at the fault point, the traveling wave signals transmitted from the fault point to the two terminals differ slightly due to different short circuit conditions. However, for the direct wave of a single side, the energy of the signal is distributed after refraction and reflection, but the overall signal waveform changes little.

[0062] First, for the fault traveling wave of a single side terminal, for example, the M terminal, all fault traveling waves in the time union are obtained. The fault traveling wave with the largest peak value in the fitting curve is marked as the direct wave, and the time corresponding to the largest peak value in the fitting curve is marked as the direct wave arrival time, which is denoted as .

[0063] Secondly, the reflected wave arrival time needs to be screened to exclude the interference of the pseudo-traveling wave.

[0064] Compared with the real fault point and the connection point, although they are both impedance discontinuity points, they have different specific manifestations. For the real fault point, the overall impedance discontinuity degree is large due to the change in the line structure caused by the short circuit, and the reflection degree is large. For the connection point, the overall impedance discontinuity degree is small due to the connection of the line, and the reflection signal degree is relatively small.

[0065] For the fault traveling wave of the M terminal after the arrival of the direct wave, the waveform similarity and peak difference between the direct wave and the fault traveling wave arriving thereafter are analyzed to screen out the reflected wave, and the arrival time thereof is recorded, so as to screen out the reflected wave of the M terminal after the arrival of the direct wave.

[0066] The screening method of the reflected wave is: using the waveform similarity, peak difference of the direct wave and the fault traveling wave arriving after it in time set, constructing the reflected wave screening value of each fault traveling wave arriving after it; marking the fault traveling wave with the largest reflected wave screening value of all fault traveling waves arriving after it as the reflected wave. And the time corresponding to the maximum peak of the fitting curve of the reflected wave is recorded as the reflected wave arrival time.

[0067] Specifically, in the embodiment, the calculation expression of the reflected wave screening value C of any fault traveling wave arriving after it is: , wherein C represents the reflected wave screening value of any fault traveling wave arriving after it, represents the similarity between the waveform fitting curve of any fault traveling wave arriving after it and the direct wave, , respectively represent the peak of any fault traveling wave arriving after it and the direct wave.

[0068] It should be noted that in the construction of the reflected wave screening value, the waveform similarity and energy attenuation of the current analyzed fault traveling wave are mainly evaluated. For the pseudo traveling wave, the impedance discontinuity such as the connection point causes the difference, but the overall discontinuity difference is small, so the energy intensity of the reflected pseudo traveling wave is low, and it is relatively easy to be disturbed in propagation, at this time, it will show low similarity with the direct wave, and the overall peak ratio is small, and the reflected wave screening value obtained is small.

[0069] Further, for all fault traveling waves arriving after the current direct wave, the fault traveling wave with the largest screening value is marked as the reflected wave, and the time corresponding to the peak point of the fault traveling wave curve is recorded as the reflected wave arrival time, recorded as .

[0070] Similarly, the direct wave and its arrival time corresponding to the N end in time set and the reflected wave and its arrival time are calculated.

[0071] S4: Based on the arrival time of the direct wave and the reflected wave at both ends, the distance from the fault point to both ends of the line is calculated by the positioning formula to locate the fault point.

[0072] The arrival time of the traveling wave signal generated by the fault point at both ends of the direct wave and the reflected wave is obtained by the above-mentioned manner, which can realize the positioning of the fault point. In the process of traveling wave fault location, the positioning of the fault point is mainly realized based on the solution of the equation set, and the specific solution equation set is as follows:

[0073] In the formula, V represents the propagation speed of the traveling wave signal on the distribution network line, unit m / s, and respectively represent the distance from the fault point to the M end and the N end, unit is m, L represents the line distance of the M end and the N end, unit is m, is a known quantity, 、 respectively represent the arrival time of the direct wave of the traveling wave signal at the M end and the arrival time of the reflected wave reflected by the fault point, 、 respectively represent the arrival time of the direct wave of the traveling wave signal at the N end and the arrival time of the reflected wave reflected by the fault point.

[0074] By solving the above equation set, , thus the specific time of positioning the traveling wave signal is substituted into the formula, the corresponding fault point distance is obtained, and thus the accurate positioning of the fault point of the power distribution network is realized.

[0075] Based on the same inventive concept as the above method, the embodiments of the present application also provide a power distribution network fault accurate positioning device based on the traveling wave principle, the device stores a computer program, and the computer program is executed by the processor to realize the power distribution network fault accurate positioning method based on the traveling wave principle.

[0076] Based on the same inventive concept as the above method, the embodiments of the present application also provide a power distribution network fault accurate positioning system based on the traveling wave principle, including a memory, a processor and a computer program stored in the memory and running on the processor, and the processor executes the computer program to realize the steps of the power distribution network fault accurate positioning method based on the traveling wave principle.

[0077] Each of the embodiments in the present application is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment mainly explains the difference from other embodiments.

[0078] It should be noted that, unless otherwise specified and limited, terms such as "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the circuit structure, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such article or device. Without more limitation, the element limited by the statement "including a" does not exclude the existence of another same element in the article or device including the element. In addition, the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0079] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

[0080] It should be understood that the application is not limited to the precise construction and compositions described above and shown in the attached drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application.

Claims

1. A method for accurate fault location in a power distribution network based on the traveling wave principle, characterized in that, The method comprises the following steps: Deploying traveling wave detection equipment at both ends of a certain section of the power distribution network for synchronously collecting potential fault traveling wave signals; Using the main frequency energy proportion in the frequency domain response of the potential fault traveling wave signal and the range of all envelope energy intensity proportions to construct a frequency domain noise point estimate of the potential fault traveling wave signal, and combining the rising edge time in the potential fault traveling wave signal to calculate the traveling wave accuracy; using the traveling wave accuracy to screen out fault traveling waves in a preset local time window of the potential fault traveling wave signal; In the time set of the two ends of the local time window, marking the fault traveling wave with the largest peak value in the single end as a direct wave, and analyzing the waveform similarity and peak difference between the direct wave and the fault traveling wave arriving thereafter to screen out a reflected wave; Based on the arrival times of the direct wave and the reflected wave at both ends, calculating the distance from the fault point to both ends of the line through a positioning formula to locate the fault point.

2. The method for precise fault location in power distribution systems based on traveling wave theory as claimed in claim 1, wherein, The judgment method of the potential fault traveling wave signal is: Obtaining the baseline of the signal received by a single detection end; Taking the electrical signals greater than the baseline at continuous multiple sampling times as fluctuation signals; Taking two fluctuation signals with a time interval less than a preset time period as a potential fault traveling wave signal.

3. The method of claim 1, wherein the method further comprises: The frequency domain noise point estimate is negatively correlated with the range of the main frequency energy and all envelope energy intensity proportions.

4. The method of claim 1, wherein the method further comprises: The traveling wave accuracy is negatively correlated with the rising edge time and the frequency domain noise point estimate.

5. The method of claim 4, wherein the method further comprises: The determination method of the rising edge time is: Obtaining the maximum value of the potential fault traveling wave signal after curve fitting; Obtaining the minimum value closest to the maximum value before the time corresponding to the maximum value in the fitted curve; Taking the time interval between the minimum value and the maximum value as the rising edge time of the potential fault traveling wave signal.

6. The method of claim 1, wherein the method further comprises: The screening method of the fault traveling wave is: threshold segmentation is performed on the traveling wave accuracy of all potential fault traveling wave signals in the local time window; the potential fault traveling wave signal with a traveling wave accuracy greater than or equal to the segmentation threshold is marked as a fault traveling wave.

7. The method of claim 6, wherein the method further comprises: The length of the preset local time window is 5 times the propagation time of the potential fault traveling wave signal from the single end of the line to the other end; when the number of fault traveling waves screened out in the local time window is less than 3, the local time window is not analyzed.

8. The method of claim 1, wherein the method further comprises: determining a fault location on the power distribution network based on the time difference between the first and second time instances. The screening method of the reflected wave is: Using the waveform similarity and peak difference between the direct wave and the fault traveling wave arriving thereafter in the single end in the time set to construct a reflected wave screening value of each fault traveling wave arriving thereafter; Marking the fault traveling wave with the largest reflected wave screening value of all fault traveling waves arriving thereafter as a reflected wave.

9. A power distribution network fault accurate positioning device based on the principle of traveling wave, the device stores a computer program, characterized in that, The computer program, when executed by a processor, implements the power distribution network fault precise positioning method based on the traveling wave principle as claimed in any one of claims 1 to 8.

10. A power distribution network fault pinpointing system based on the traveling wave principle, comprising a memory, a processor and a computer program stored in the memory and running on the processor, characterized in that, The processor, when executing the computer program, implements the steps of the power distribution network fault precise positioning method based on the traveling wave principle as claimed in any one of claims 1 to 8.

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