Power transmission line single-end fault positioning method and system

Abstract

The invention relates to the technical field of power system relay protection, in particular to a power transmission line single-end fault positioning method and system. The method comprises the following steps: taking an envelope zero crossing point of an initial transient traveling wave signal as an attenuation ending moment; taking the moment from the occurrence moment of the initial transient traveling wave signal to the attenuation ending moment as an analysis time window; taking the duration of the analysis time window as the attenuation duration of the initial transient traveling wave signal; taking the maximum energy peak value as a resonant frequency identification reference threshold value, searching whether the energy of other frequency peak values greater than the resonant frequency identification threshold value exists or not, and if so, judging whether the initial transient traveling wave signal has resonant interference or not based on the attenuation duration of the initial transient traveling wave signal; if yes, designing a filter for the frequency component, and filtering the initial transient traveling wave signal; and obtaining a fault positioning result of the power transmission line based on the filtered transient traveling wave signal. According to the invention, the single-end fault positioning precision is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of power system automation technology, and in particular to a method and system for locating single-end faults in transmission lines. Background Technology

[0002] After a transmission line fault occurs, quickly and accurately locating the fault point can effectively shorten power outage time, reduce economic losses, and improve power supply reliability. For a long time, transmission line fault location has been considered a key technology for ensuring the safe operation of the power system. In the field of transmission line fault location, the impedance fault location method was initially applied. This method calculates the impedance of the faulty line by measuring the voltage and current at the beginning of the faulty line, and then estimates the fault distance. While the impedance method is simple in principle and low in cost, its location accuracy is affected by factors such as system operating mode and transition resistance, resulting in a relatively large actual error.

[0003] To address the insufficient accuracy of impedance methods, traveling wave fault location technology for transmission lines has emerged. This technology utilizes the transient traveling wave signal generated by the fault to locate the fault, and is further divided into two categories based on the required electrical quantities: the double-ended method and the single-ended method. Currently, the double-ended method is mainly used in practical engineering for traveling wave fault location devices. Its reliability and accuracy basically meet the needs of power systems, but it has significant limitations based on operational experience: Firstly, the double-ended method requires coordinated operation of devices at both ends of the line; if one device malfunctions, fault location will fail directly, necessitating the use of the single-ended method as a backup analysis tool. Secondly, if the end of the line is open or the installation conditions for fault location devices are not available due to management reasons, the double-ended method cannot be implemented. Therefore, the importance of single-ended traveling wave fault location technology is becoming increasingly prominent. This technology utilizes the time difference between the initial traveling wave of the fault and the reflected wave at the fault point or end of the line for location, and is unaffected by communication, time synchronization, or other factors, resulting in higher location accuracy and effectively compensating for the shortcomings of the double-ended method.

[0004] However, single-ended traveling wave fault location still has certain problems in practical applications, with signal resonance being the main defect affecting its location accuracy. In actual fault analysis, high-frequency signal resonance is mainly caused by multiple impedance discontinuities in the line or impedance mismatch in the secondary circuit: impedance discontinuities such as branch lines on transmission lines, series compensation capacitors, or connections between different line types can cause multiple refractions and reflections of the traveling wave signal, forming superimposed resonance; if the impedance matching of the secondary circuit, such as the signal cable connecting the fault location device and the transformer, is unreasonable, its beginning and end will also become impedance discontinuities. When the traveling wave signal propagates at these points, the reflections caused by impedance mismatch will superimpose with the traveling wave in the primary circuit, also causing resonance. The key to single-ended fault location is to accurately identify the reflected wave at the fault point and the reflected wave at the end of the line. However, the false reflected wave generated by resonance is similar in waveform and frequency band to the real reflected wave, making it very easy to be misidentified. This superposition phenomenon between resonance and real reflected wave will directly lead to incorrect identification of reflected wave, seriously affecting the reliability and accuracy of single-ended traveling wave fault location, resulting in poor single-ended fault location accuracy. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing single-end traveling wave fault location, which are poor in single-end fault location due to signal aliasing and false reflected waves caused by signal resonance, which interfere with the accurate identification of the fault point and the real reflected wave at the end of the line.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for locating single-end faults in transmission lines, comprising: Extract the envelope of the initial transient traveling wave signal when the transmission line is faulty, and take the zero-crossing point of the envelope as the end time of the decay of the initial transient traveling wave signal. The time window for analysis is defined as the time from the occurrence of the initial transient traveling wave signal to the end of its decay; the duration of the analysis time window is defined as the decay duration of the initial transient traveling wave signal. The initial transient traveling wave signal is subjected to Fourier transform within the analysis time window to obtain the frequency domain signal amplitude spectrum; Based on the maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window, a resonant frequency identification threshold is set. In the frequency domain signal amplitude spectrum, the frequency component corresponding to the maximum energy peak within the analysis time window is used as the benchmark to determine whether there are other frequency peaks whose energy is greater than the resonant frequency identification threshold, in addition to the benchmark frequency component. If not, the fault location result of the transmission line is obtained based on the initial transient traveling wave signal; If it exists, the initial transient traveling wave signal is judged to have resonant interference based on the decay time of the initial transient traveling wave signal; if resonant interference exists, the frequency component is taken as the resonant frequency; the initial transient traveling wave signal is filtered based on the resonant frequency; the fault location result of the transmission line is obtained based on the filtered transient traveling wave signal; if it does not exist, the fault location result of the transmission line is obtained based on the initial transient traveling wave signal.

[0007] Preferably, the method for obtaining the initial transient traveling wave signal during a transmission line fault includes: Traveling wave sensors installed on power transmission lines are used to collect initial transient traveling wave signals during power transmission line faults.

[0008] Preferably, the method for determining whether there is resonant interference in the initial transient traveling wave signal based on the decay time of the initial transient traveling wave signal includes: Determine whether the decay time of the initial transient traveling wave signal is greater than the decay time threshold. If it is, determine that the initial transient traveling wave signal has resonant interference; otherwise, determine that the initial transient traveling wave signal does not have resonant interference.

[0009] Preferably, the method for setting the resonant frequency identification threshold based on the maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window includes: The maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window is used as the benchmark threshold for resonant frequency identification. Set the peak percentage, and multiply the resonant frequency identification benchmark threshold by the set peak percentage to obtain the resonant frequency identification threshold.

[0010] Preferably, the method for filtering the initial transient traveling wave signal based on the resonant frequency includes: The resonant frequency is set as the center frequency of the band-stop filter, and the initial transient traveling wave signal is filtered by the band-stop filter to obtain the filtered transient traveling wave signal.

[0011] Preferably, obtaining the fault location result of the transmission line based on the filtered transient traveling wave signal includes: The filtered transient traveling wave signal is processed by binary wavelet transform, which decomposes the filtered transient traveling wave signal into low-frequency approximation coefficients and high-frequency detail coefficients; Based on high-frequency detail coefficients, the corresponding modulus maxima sequence is obtained and extracted; Based on the modulus maxima sequence, the time when the filtered transient traveling wave signal arrives at the measurement end is determined; The peak value of the filtered transient traveling wave signal with the largest amplitude after it reaches the measurement end is taken as the reflected wave. By comparing the directions of the reflected wave and the filtered transient traveling wave signal, the type of the reflected wave can be determined. Based on the traveling wave propagation speed, the time when the initial transient traveling wave signal arrives at the measurement end, the time when the reflected wave arrives at the measurement end, and the type of reflected wave, the fault location results of the transmission line are obtained.

[0012] Preferably, the method for determining the type of reflected wave by comparing the directions of the reflected wave and the filtered transient traveling wave signal includes: Determine whether the direction of the reflected wave is consistent with that of the filtered transient traveling wave signal. If they are consistent, the reflected wave is determined to be the reflected wave from the fault point; if they are inconsistent, the reflected wave is determined to be the reflected wave from the other end of the line.

[0013] Preferably, when the reflected wave is a fault point reflected wave, the calculation formula for obtaining the fault location result of the transmission line based on the traveling wave propagation speed, the time when the initial transient traveling wave signal arrives at the measurement end, and the time when the reflected wave arrives at the measurement end is as follows: , in, The distance from the fault point to the measuring end. The time when the reflected wave from the fault point arrives at the measuring end. The time when the initial transient traveling wave signal arrives at the measurement end. This represents the propagation speed of the traveling wave.

[0014] Preferably, when the reflected wave is a reflected wave from the opposite end of the line, the calculation formula for obtaining the fault location result of the transmission line based on the traveling wave propagation speed, the time when the initial transient traveling wave signal arrives at the measurement end, and the time when the reflected wave arrives at the measurement end is as follows: , in, The distance from the fault point to the measuring end. The time when the reflected wave from the opposite end of the line arrives at the measuring end. The time when the initial transient traveling wave signal arrives at the measurement end. For the speed of travel wave propagation, This refers to the total length of the transmission line.

[0015] The present invention also provides a single-end fault location system for transmission lines, comprising: The timing determination module is used to extract the envelope of the initial transient traveling wave signal when the transmission line is faulty, and the zero-crossing point of the envelope is taken as the end time of the decay of the initial transient traveling wave signal. The decay duration acquisition module is used to take the time from the occurrence of the initial transient traveling wave signal to the end of decay as the analysis time window; and the duration of the analysis time window is used as the decay duration of the initial transient traveling wave signal. The amplitude spectrum acquisition module is used to perform Fourier transform on the initial transient traveling wave signal within the analysis time window to obtain the frequency domain signal amplitude spectrum. The threshold acquisition module is used to set the resonant frequency identification threshold based on the maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window. The positioning module is used to determine, in the frequency domain signal amplitude spectrum, whether there are other frequency peaks whose energy is greater than the resonant frequency identification threshold, based on the frequency component corresponding to the maximum energy peak within the analysis time window. If not, the fault location result of the transmission line is obtained based on the initial transient traveling wave signal; If it exists, the initial transient traveling wave signal is judged to have resonant interference based on the decay time of the initial transient traveling wave signal; if resonant interference exists, the frequency component is taken as the resonant frequency; the initial transient traveling wave signal is filtered based on the resonant frequency; the fault location result of the transmission line is obtained based on the filtered transient traveling wave signal; if it does not exist, the fault location result of the transmission line is obtained based on the initial transient traveling wave signal.

[0016] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: The present invention discloses a method and system for locating single-ended faults in transmission lines. First, an analysis time window is constructed based on the difference in attenuation characteristics between the transient traveling wave and the resonant signal. By extracting the envelope of the initial transient traveling wave signal and taking its zero-crossing point as the attenuation end time, the analysis time window is defined from the initial traveling wave occurrence time to the attenuation end time. At the same time, the duration of the analysis time window is used as the attenuation duration. By utilizing the characteristic of the long attenuation period of the resonant signal, a preliminary judgment of resonant interference is achieved. Through the core difference between the fault traveling wave and the resonant signal in the time-domain attenuation dimension, a solid judgment basis is laid for subsequent interference elimination. Building upon this foundation, for scenarios where resonant interference is identified, this invention further incorporates the difference in frequency domain energy distribution between the two components for precise processing. First, within the analysis time window, a Fourier transform is performed on the initial transient traveling wave signal to obtain the frequency domain signal amplitude spectrum. Then, a resonant frequency identification threshold is set based on the maximum energy peak value within the spectrum, filtering out resonant frequency components exceeding the threshold. This process fully utilizes the characteristics of fault transient traveling waves as broadband signals with energy dispersed across various frequencies, while resonant signals, due to the series and parallel resonance of transmission line inductance and capacitance, concentrate energy at specific frequencies, achieving precise locking of the resonant frequency. Based on the identified resonant frequency, the initial transient traveling wave signal is filtered to specifically remove resonant interference components, avoiding false reflected waves formed by the resonant signal and errors in reflecting wave identification caused by the superposition of the resonant signal and the real fault reflected wave. Finally, fault location is achieved based on the filtered, clean transient traveling wave signal, effectively realizing the precise location of transmission line fault points. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0018] Figure 1 This is a schematic diagram illustrating the effect of signal resonance on the positioning of a single-ended traveling wave.

[0019] Figure 2 This is a flowchart of the steps of a single-end fault location method for power transmission lines according to the present invention.

[0020] Figure 3 This is a flowchart illustrating a single-end fault location method for power transmission lines according to the present invention.

[0021] Figure 4 This is a schematic diagram of time window extraction and analysis based on signal envelope.

[0022] Figure 5 This is a schematic diagram of extracting the resonant frequency within the analysis time window.

[0023] Figure 6 This is a schematic diagram of the waveform after filtering out the resonant signal.

[0024] Figure 7 This is a schematic diagram of the spectrum of the filtered transient traveling wave signal. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0026] like Figure 1 As shown, Figure 1 This is a schematic diagram illustrating the effect of signal resonance on the positioning of a single-ended traveling wave.

[0027] In current engineering practice, in scenarios involving DC lines or near-end faults (fault points close to substations), signal resonance can severely interfere with the identification of reflected waves in single-ended traveling wave localization, thereby reducing the reliability of fault localization. In such cases, it is often necessary to combine data from other devices and use impedance or frequency domain methods to assist in fault localization. However, introducing additional system data not only increases the complexity and delay of data interaction, but also easily leads to uncertainty in the localization results due to the synchronization and compatibility issues of data from multiple devices. At the same time, it also increases the system's operation and maintenance costs.

[0028] To address the core issues of signal aliasing and spurious reflected waves caused by signal resonance, refer to Figure 2 , Figure 3As shown in the figure, this embodiment provides a single-end fault location method adapted to transmission lines to solve the problem of insufficient location accuracy caused by the above-mentioned resonant interference. It includes four steps: resonant signal identification and characteristics, resonant frequency filtering, time-frequency signal analysis and reflected wave identification, and single-end fault location calculation. The specific scheme is as follows: Step S1: Extract the envelope of the initial transient traveling wave signal when the transmission line is faulty, and take the zero-crossing point of the envelope as the end time of the decay of the initial transient traveling wave signal. In this embodiment, specifically, the method for obtaining the initial transient traveling wave signal during a transmission line fault includes: Traveling wave sensors installed on power transmission lines are used to collect initial transient traveling wave signals during power transmission line faults.

[0029] In this embodiment, specifically, the envelope of the initial transient traveling wave signal during a transmission line fault is extracted using the Hilbert transform, including: The initial transient traveling wave signal during a transmission line fault is transformed into the frequency domain by performing a Fourier transform. The initial transient traveling wave signal is processed in the frequency domain to suppress negative frequency signals and retain positive frequency signals; Perform an inverse Fourier transform on the processed initial transient traveling wave signal to restore it to the time domain; The envelope of the initial transient traveling wave signal is obtained by taking the modulus of the time-domain complex signal obtained after the inverse Fourier transform.

[0030] Figure 1 The signal shown is subjected to a Hilbert transform, resulting in the signal envelope as follows: Figure 4 As shown.

[0031] Step S2: Use the time from the occurrence of the initial transient traveling wave signal to the end of its decay as the analysis time window; use the duration of the analysis time window as the decay duration of the initial transient traveling wave signal. Step S3: Perform a Fourier transform on the initial transient traveling wave signal within the analysis time window to obtain the frequency domain signal amplitude spectrum; In this invention, the analysis time window is defined by the time from the occurrence of the initial transient traveling wave signal to the end of its decay. On the one hand, compared to the problem that an excessively large time window can easily lead to a relative decrease in the resonance peak value and weakening of characteristics, the analysis time window of this invention focuses on the complete process from the generation of the initial transient traveling wave to the end of its decay. This can effectively avoid the introduction of irrelevant time-domain signals, ensuring that the energy of the resonance signal is concentrated in the frequency domain signal amplitude spectrum, and improving the identification of the resonance characteristic frequency. On the other hand, compared to the defect that an excessively small time window cannot fully reflect the overall resonance characteristics, this analysis time window can completely cover the decay period of the resonance signal at the microsecond level, comprehensively capturing the time-domain evolution characteristics of the resonance signal. This provides a guarantee for obtaining an accurate frequency domain signal amplitude spectrum through Fourier transform within the window, thereby laying a solid foundation for subsequent determination of resonance based on spectral energy thresholds, achieving the accuracy and reliability of resonance identification, and providing strong support for subsequent targeted filtering and fault location.

[0032] Step S4: Based on the maximum energy peak of the frequency domain signal amplitude spectrum within the analysis time window, set the resonant frequency identification threshold, including: The maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window is used as the benchmark threshold for resonant frequency identification. Set the peak percentage, and multiply the resonant frequency identification benchmark threshold by the set peak percentage to obtain the resonant frequency identification threshold.

[0033] There are two scenarios: (1) Signal resonance exists: When a signal is in resonance, a specific frequency increases significantly. This frequency is the resonant frequency. However, in some actual faults, there may be multiple resonances.

[0034] (2) No signal resonance: In the absence of resonance, the signal spectrum exhibits a characteristic of gradually attenuating from the DC component to the high frequency.

[0035] Based on the above principles, the identification criteria are as follows: First, identify the maximum energy peak value. In the absence of resonance, the peak values ​​of other frequencies generally do not exceed 50% of the maximum energy peak value. Therefore, in this embodiment, the peak percentage is 50%.

[0036] Figure 4 The waveform shown has the following spectrum obtained after Fourier transform: Figure 5 As shown, there are multiple frequency peaks from the DC component to the high-frequency band that exceed 50% of the maximum peak value (threshold), indicating the presence of signal resonance. The resonance peak value corresponds to the resonance frequency.

[0037] Step S5: In the frequency domain signal amplitude spectrum, using the frequency component corresponding to the maximum energy peak within the analysis time window as a benchmark, determine whether there are other frequency peaks with energy greater than the resonant frequency identification threshold, including: Set a peak percentage, multiply the maximum energy peak of the frequency domain signal amplitude spectrum within the analysis time window by the set peak percentage, and use it as the resonant frequency identification threshold.

[0038] Step S6: If not, obtain the fault location result of the transmission line based on the initial transient traveling wave signal; Step S7: If it exists, determine whether there is resonant interference in the initial transient traveling wave signal based on the decay time of the initial transient traveling wave signal; if there is resonant interference, take the frequency component as the resonant frequency; filter the initial transient traveling wave signal based on the resonant frequency; obtain the fault location result of the transmission line based on the filtered transient traveling wave signal; if it does not exist, obtain the fault location result of the transmission line based on the initial transient traveling wave signal.

[0039] In this embodiment, specifically, determining whether the initial transient traveling wave signal has resonant interference based on the attenuation time of the initial transient traveling wave signal includes: The system determines whether the decay time of the initial transient traveling wave signal is greater than a decay time threshold. If it is, the initial transient traveling wave signal is determined to have resonant interference; otherwise, the initial transient traveling wave signal is determined not to have resonant interference. In this embodiment, the decay time threshold is 100 microseconds.

[0040] In this embodiment, specifically, the method for filtering the initial transient traveling wave signal based on the resonant frequency includes: The resonant frequency is set to the center frequency of the band-stop filter. The initial transient traveling wave signal is filtered by the band-stop filter to obtain the filtered transient traveling wave signal. The filtered transient traveling wave signal is as follows: Figure 6 As shown, the signal spectrum is as follows Figure 7 As shown, after filtering at a specific frequency, the resonant frequency component is significantly reduced, and the difficulty of identifying the initial transient traveling wave signal and the reflected wave signal is significantly reduced.

[0041] In this embodiment, specifically, obtaining the fault location result of the transmission line based on the filtered transient traveling wave signal includes: The filtered transient traveling wave signal is processed by binary wavelet transform. The frequency bands with more obvious non-fault characteristics are selected for analysis based on the amplitude of the wavelet transform detail coefficients. Under a given analysis scale, the filtered transient traveling wave signal is decomposed into low-frequency approximation coefficients and high-frequency detail coefficients, as shown in the following formula: , in, For high-frequency detail coefficients, , For high-frequency detail coefficient index, This represents the total number of high-frequency detail coefficients. These detail coefficients have good time resolution and are suitable for calculating the initial moment of a fault. This invention uses wavelet transform modulus maxima to identify the initial moment of a fault. The steps are as follows: Based on high-frequency detail factor Obtain the corresponding sequence of modulo maxima; Based on the modulus maxima sequence, the time when the filtered transient traveling wave signal arrives at the measurement end is determined; The peak value of the filtered transient traveling wave signal with the largest amplitude after it reaches the measurement end is taken as the reflected wave. By comparing the directions of the reflected wave and the filtered transient traveling wave signal, the type of reflected wave can be determined, including: Determine whether the direction of the reflected wave is consistent with that of the filtered transient traveling wave signal. If they are consistent, the reflected wave is determined to be the reflected wave from the fault point; if they are inconsistent, the reflected wave is determined to be the reflected wave from the other end of the line.

[0042] After completing the identification of the reflected wave at the fault point / line counterpart, a single-ended traveling wave is used to complete the final fault point location. When both the reflected wave at the fault point and the reflected wave at the line counterpart can be identified simultaneously, the reflected wave that is closer in distance (closer to the initial time) is selected to complete the fault location.

[0043] Based on the traveling wave propagation velocity, the arrival time of the initial transient traveling wave signal at the measurement end, the arrival time of the reflected wave at the measurement end, and the type of reflected wave, the fault location results of the transmission line are obtained, including: When the reflected wave is a fault point reflected wave, the calculation formula for obtaining the fault location result of the transmission line, based on the traveling wave propagation velocity, the time when the initial transient traveling wave signal arrives at the measurement end, and the time when the reflected wave arrives at the measurement end, is as follows: , in, The distance from the fault point to the measuring end. The time when the reflected wave from the fault point arrives at the measuring end. The time when the initial transient traveling wave signal arrives at the measurement end. This represents the propagation speed of the traveling wave.

[0044] When the reflected wave is a reflected wave from the opposite end of the line, the calculation formula for obtaining the fault location result of the transmission line, based on the traveling wave propagation speed, the time when the initial transient traveling wave signal arrives at the measurement end, and the time when the reflected wave arrives at the measurement end, is as follows: , in, The distance from the fault point to the measuring end. The time when the reflected wave from the opposite end of the line arrives at the measuring end. The time when the initial transient traveling wave signal arrives at the measurement end. For the speed of travel wave propagation, This refers to the total length of the transmission line.

[0045] This invention aims to accurately eliminate the interference of specific frequency signal resonance on the location of single-end traveling wave faults in transmission lines. The primary prerequisite is the effective identification of specific frequency resonances. Based on the signal characteristic analysis of the transient process of transmission line faults, signal resonance has the following two quantifiable core characteristics, providing crucial evidence for resonance identification: (1) From the perspective of fault transient mechanism, when a fault occurs in a transmission line, the instantaneous voltage drop and the rapid change in current are similar to step excitation. The transient fault traveling wave excited by this exhibits broadband signal characteristics, and its energy is distributed in a dispersed manner throughout the entire frequency domain. The essence of signal resonance is that the distributed inductance and distributed capacitance (or lumped parameter elements such as series compensation capacitors) of the transmission line form a series or parallel resonant circuit at a specific frequency, which causes electromagnetic energy to accumulate continuously at that frequency. Therefore, the energy of the resonant signal will be highly concentrated on the corresponding resonant frequency component, forming a significant frequency domain energy peak.

[0046] (2) Long attenuation period: From the perspective of time-domain attenuation characteristics, the pulse width of the initial fault traveling wave and the fault point reflected wave is usually in the microsecond range, with fast attenuation speed and short duration; while the attenuation period of the resonant signal is directly related to the damping characteristics of the transmission line. Affected by damping factors such as line resistance and insulation loss, its energy release process is slow, and the attenuation period is usually as long as hundreds of microseconds (the pulse width of a typical lightning fault does not exceed 100 microseconds / the pulse width of a ground fault is generally shorter) and above, far exceeding the pulse width of the fault traveling wave.

[0047] Based on the above two characteristics, the resonance identification criteria established in this embodiment are as follows: 1) The attenuation time of the initial transient traveling wave signal exceeds a preset value; 2) In the spectrum of the initial transient traveling wave signal, there is a specific frequency component with an energy amplitude exceeding a preset threshold. When both criteria are satisfied simultaneously, it can be determined that there is specific frequency resonance interference in the initial transient traveling wave signal.

[0048] This invention identifies resonance based on signal attenuation time and signal spectrum. First, it uses Hilbert transform to extract the signal envelope. Then, it identifies the resonance signal analysis time window based on the zero-crossing point of the signal envelope. Next, within the analysis time window, it identifies the resonance characteristic frequency based on the signal energy. Based on the resonance frequency, it constructs a band-stop filter at a specific frequency to achieve single-ended traveling wave fault location while suppressing the resonance signal, reducing the impact of resonance on reflected wave identification. By using attenuation time and spectral peak values ​​to identify resonance, and then constructing a targeted frequency limiter to filter out the resonance component, the invention effectively achieves reflected wave identification and single-ended fault location based on the filtered, pure traveling wave.

[0049] This invention achieves accurate resonance identification based on signal decay time and signal spectral characteristics. The specific process is as follows: First, the signal envelope is extracted using Hilbert transform, and the analysis time window for the resonant signal is defined based on the zero-crossing point of the signal envelope. Second, within this analysis time window, the resonant characteristic frequency is identified by combining the signal energy distribution, and a band-stop filter of a specific frequency is constructed using this resonant frequency as the core. Finally, based on suppressing resonant signal interference, the single-ended traveling wave fault location process is completed, thereby reducing the adverse effects of resonance on reflected wave identification. This scheme identifies resonance through a dual dimension of "decay time (over 100 microseconds) + spectral peak value (over 50% of the maximum peak value)," then constructs a targeted frequency filter to remove resonant components, and finally, based on the pure traveling wave signal obtained after filtering, achieves accurate identification of reflected waves and single-ended fault location.

[0050] Compared with existing single-ended fault location methods, this invention has stronger anti-harmonic interference capabilities. By identifying the attenuation period and characteristic frequency of the resonant signal and limiting the resonant signal, the influence of the resonant signal can be suppressed, avoiding false reflections caused by resonance and errors in the identification of reflected waves due to the superposition of the resonant signal and the reflected wave. Furthermore, it is simple to implement in engineering. Compared with single-ended location methods that require other auxiliary quantities, the algorithm described in this patent only requires data from the traveling wave fault location device itself, without needing to introduce data from other systems, making it relatively simple to implement in engineering.

[0051] This second embodiment provides a single-end fault location system for transmission lines, including: The timing determination module is used to extract the envelope of the initial transient traveling wave signal when the transmission line is faulty, and the zero-crossing point of the envelope is taken as the end time of the decay of the initial transient traveling wave signal. The decay duration acquisition module is used to take the time from the occurrence of the initial transient traveling wave signal to the end of decay as the analysis time window; and the duration of the analysis time window is used as the decay duration of the initial transient traveling wave signal. The amplitude spectrum acquisition module is used to perform Fourier transform on the initial transient traveling wave signal within the analysis time window to obtain the frequency domain signal amplitude spectrum. The threshold acquisition module is used to set the resonant frequency identification threshold based on the maximum energy peak value of the frequency domain signal amplitude spectrum within the analysis time window. The location module is used to determine, in the frequency domain signal amplitude spectrum, whether there are other frequency peaks whose energy is greater than the resonant frequency identification threshold, based on the frequency component corresponding to the maximum energy peak within the analysis time window; if not, it obtains the fault location result of the transmission line based on the initial transient traveling wave signal. If it exists, the initial transient traveling wave signal is judged to have resonant interference based on the decay time of the initial transient traveling wave signal; if resonant interference exists, the frequency component is taken as the resonant frequency; the initial transient traveling wave signal is filtered based on the resonant frequency; the fault location result of the transmission line is obtained based on the filtered transient traveling wave signal; if it does not exist, the fault location result of the transmission line is obtained based on the initial transient traveling wave signal.

[0052] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0053] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0054] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0055] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0056] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for single-ended fault location of a power transmission line, characterized in that, The method comprises the following steps: extracting an envelope of an initial transient traveling wave signal at the time of a fault of a power transmission line, and taking a zero-crossing point of the envelope as an end time of attenuation of the initial transient traveling wave signal; taking a time from an occurrence time of the initial transient traveling wave signal to the end time of attenuation as an analysis time window, and taking a length of the analysis time window as an attenuation length of the initial transient traveling wave signal; performing Fourier transform on the initial transient traveling wave signal in the analysis time window to obtain a frequency domain signal amplitude spectrum; setting a resonance frequency identification threshold based on a maximum energy peak value of the frequency domain signal amplitude spectrum in the analysis time window; in the frequency domain signal amplitude spectrum, taking a frequency component corresponding to the maximum energy peak value in the analysis time window as a reference, and judging whether energy of other frequency peak values is greater than the resonance frequency identification threshold except for the reference frequency component; if not, obtaining a fault positioning result of the power transmission line based on the initial transient traveling wave signal; if yes, judging whether the initial transient traveling wave signal has resonance interference based on the attenuation length of the initial transient traveling wave signal; if yes, taking the frequency component as a resonance frequency; filtering the initial transient traveling wave signal based on the resonance frequency; obtaining the fault positioning result of the power transmission line based on the filtered transient traveling wave signal; if not, obtaining the fault positioning result of the power transmission line based on the initial transient traveling wave signal.

2. A single-ended fault location method for a power transmission line according to claim 1, characterized in that, The method for obtaining the initial transient traveling wave signal at the time of the fault of the power transmission line comprises the following steps: collecting the initial transient traveling wave signal at the time of the fault of the power transmission line through a traveling wave sensor installed on the power transmission line.

3. The method of claim 1, wherein, The method for judging whether the initial transient traveling wave signal has resonance interference based on the attenuation length of the initial transient traveling wave signal comprises the following steps: judging whether the attenuation length of the initial transient traveling wave signal is greater than an attenuation length threshold, and if yes, determining that the initial transient traveling wave signal has resonance interference; otherwise, determining that the initial transient traveling wave signal does not have resonance interference.

4. The method of claim 1, wherein, The method for setting the resonance frequency identification threshold based on the maximum energy peak value of the frequency domain signal amplitude spectrum in the analysis time window comprises the following steps: taking the maximum energy peak value of the frequency domain signal amplitude spectrum in the analysis time window as a resonance frequency identification reference threshold; setting a peak percentage, and multiplying the resonance frequency identification reference threshold by the set peak percentage to obtain the resonance frequency identification threshold.

5. The method of claim 1, wherein, The method for filtering the initial transient traveling wave signal based on the resonance frequency comprises the following steps: setting the resonance frequency as a center frequency of a band-stop wave limiter, and filtering the initial transient traveling wave signal through the band-stop wave limiter to obtain the filtered transient traveling wave signal.

6. The method of claim 1, wherein, The method for obtaining the fault positioning result of the power transmission line based on the filtered transient traveling wave signal comprises the following steps: performing binary wavelet transform processing on the filtered transient traveling wave signal, and decomposing the filtered transient traveling wave signal into low-frequency approximation coefficients and high-frequency detail coefficients; obtaining a corresponding modulus maximum value sequence based on the high-frequency detail coefficients; determining a time when the filtered transient traveling wave signal reaches a measurement end based on the modulus maximum value sequence; taking a signal peak value with the largest amplitude after the time when the filtered transient traveling wave signal reaches the measurement end as a reflected wave; comparing directions of the reflected wave and the filtered transient traveling wave signal to confirm a type of the reflected wave; The fault positioning result of the power transmission line is obtained based on the traveling wave propagation speed, the time when the initial transient traveling wave signal reaches the measurement end, the time when the reflected wave reaches the measurement end, and the type of the reflected wave.

7. A single-ended fault location method for a power transmission line according to claim 6, characterized in that, The method for confirming the type of the reflected wave by comparing the directions of the reflected wave and the filtered transient traveling wave signal comprises: determining whether the directions of the reflected wave and the filtered transient traveling wave signal are consistent, and if yes, determining that the reflected wave is the fault point reflected wave, and if not, determining that the reflected wave is the line opposite end reflected wave.

8. A single-ended fault location method for a power transmission line according to claim 7, characterized in that, When the reflected wave is the fault point reflected wave, the calculation formula for obtaining the fault positioning result of the power transmission line based on the traveling wave propagation speed, the time when the initial transient traveling wave signal reaches the measurement end, and the time when the reflected wave reaches the measurement end is: ， wherein, is the distance of the fault point from the measurement end, is the time of arrival of the reflected wave from the fault point at the measurement end, is the time of arrival of the initial transient traveling wave signal at the measurement end, is the traveling wave propagation speed.

9. The method of claim 7, wherein, When the reflected wave is the line opposite end reflected wave, the calculation formula for obtaining the fault positioning result of the power transmission line based on the traveling wave propagation speed, the time when the initial transient traveling wave signal reaches the measurement end, and the time when the reflected wave reaches the measurement end is: ， wherein, is the distance of the fault point from the measurement end, is the time of arrival of the reflected wave from the opposite end of the line at the measurement end, is the time of arrival of the initial transient traveling wave signal at the measurement end, is the traveling wave propagation speed, is the full length of the transmission line.

10. A single-ended fault location system for a power transmission line, characterized in that, comprises: a time determination module configured to extract an envelope of an initial transient traveling wave signal at the time of a fault of a power transmission line, and take a zero-crossing point of the envelope as an attenuation end time of the initial transient traveling wave signal; an attenuation time length acquisition module configured to take a time from an occurrence time of the initial transient traveling wave signal to the attenuation end time as an analysis time window, and take a time length of the analysis time window as an attenuation time length of the initial transient traveling wave signal; an amplitude spectrum acquisition module configured to perform Fourier transform on the initial transient traveling wave signal in the analysis time window to obtain a frequency domain signal amplitude spectrum; a threshold acquisition module configured to set a resonance frequency identification threshold based on a maximum energy peak value of the frequency domain signal amplitude spectrum in the analysis time window; a positioning module configured to, in the frequency domain signal amplitude spectrum, take a frequency component corresponding to the maximum energy peak value in the analysis time window as a reference, and determine whether there is another frequency peak value whose energy is greater than the resonance frequency identification threshold except the reference frequency component; if not, obtaining a fault positioning result of the power transmission line based on the initial transient traveling wave signal; if yes, determining whether there is resonance interference in the initial transient traveling wave signal based on the attenuation time length of the initial transient traveling wave signal; if yes, taking the frequency component as a resonance frequency; filtering the initial transient traveling wave signal based on the resonance frequency; obtaining the fault positioning result of the power transmission line based on the filtered transient traveling wave signal; if not, obtaining the fault positioning result of the power transmission line based on the initial transient traveling wave signal.

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