Power distribution network asynchronous double-end traveling wave distance measurement method and device and storage medium

Abstract

This invention provides a method, device, and storage medium for asynchronous two-terminal traveling wave ranging in a distribution network. The method includes: acquiring three-phase voltage signals of the line before and after a fault by using distributed distribution terminals located at feeder branch points and feeder ends, based on a traveling wave ranging request; performing transformation and detail coefficient processing on the three-phase voltage signals; obtaining the overlapping waves of the three-phase voltage signals; normalizing the non-overlapping traveling waves distributed between the two overlapping waves to zero, determining the time difference; further determining the distribution terminal near the fault; determining the fault distance based on the time difference between the near-end distribution terminals, and reporting the fault distance. The advantages of this invention are: accurate measurement of fault distance; the method is unaffected by transition resistance, initial phase angle, or system grounding method; the method does not require two-terminal synchronous communication; and the method offers high ranging accuracy and short time requirements, meeting the requirements of existing distribution network projects.

Description

Technical Field

[0001] This invention relates to the field of distribution network feeder automation technology, and in particular to a method, device and storage medium for asynchronous double-ended traveling wave ranging in distribution networks. Background Technology

[0002] With the expansion of power grids, the coverage area of ​​distribution network systems is becoming increasingly wide, making the reliability of power supply increasingly important. Statistics show that power outages due to distribution network faults account for about half of the average annual power outage time. Therefore, reducing the time spent handling distribution network faults can reduce overall power outage time. The increasing size of distribution network systems also increases the probability of problems such as short circuits caused by foreign objects, external damage, and aging lines. Furthermore, many power grids are located in remote mountainous areas with poor transportation access. When line faults occur due to various reasons, traditional manual line tracing methods not only waste a lot of energy and resources but also a significant amount of maintenance time, resulting in prolonged power outages. Rapidly measuring the fault distance and locating the fault is of great research significance for reducing power system outage time, improving the reliability of distribution network power supply, and reducing economic losses caused by line faults.

[0003] When a power system fault occurs, the line voltage suddenly changes, resulting in a transient process. This process manifests as a traveling wave signal generated at the fault point moving towards both busbars. Most existing methods utilize this traveling wave signal for fault location, primarily categorized as single-ended, double-ended, and multi-ended traveling wave methods. The single-ended traveling wave method records the time difference between the first wavefront generated by the fault and the second reflected wavefront at the fault point on the busbar side. However, in complex distribution networks with short lines, the second reflected wavefront is easily confused with other reflected wavefronts, making identification difficult. The double-ended and multi-ended traveling wave methods utilize synchronization techniques to calculate the fault distance based on the arrival time of the traveling waves at both ends and multiple ends. These methods are affected by synchronization technology; most existing synchronization accuracies are only at the microsecond level, and a 1-microsecond synchronization error can lead to a ranging error of hundreds of meters, making them unsuitable for distribution networks with short lines. On the other hand, in the multi-terminal traveling wave method, each power distribution terminal unit (FTU) needs to communicate with the master station. However, the extremely high sampling frequency required in traveling wave ranging results in a huge amount of sampling data, which places a huge communication burden on the master station. Summary of the Invention

[0004] The main objective of this invention is to propose an asynchronous two-terminal traveling wave ranging method, device, and storage medium for power distribution networks, thereby improving the accuracy of power grid fault identification and reducing ranging consumption.

[0005] The technical solution of this invention discloses, in one aspect, a method for asynchronous two-terminal traveling wave ranging in a distribution network, comprising:

[0006] Based on the traveling wave ranging request, the three-phase voltage signals of the line before and after the fault are collected by distributed distribution terminals set at the feeder branch points and the beginning and end of the feeder.

[0007] After performing Karenbauer transformation on the three-phase voltage signal of the line, the line-mode voltage is obtained. The line-mode voltage is then subjected to Haar wavelet transformation to obtain the wavefront information of the exchanged Haar wavelet of the distribution terminal at both ends of the fault. The exchanged Haar wavelet is then processed for detail coefficients, where both ends include a first end and a second end.

[0008] The first peak values ​​of the three-phase voltage signals of the line at the first end and the three-phase voltage signals of the line at the second end are aligned and normalized to the same time point to determine the first and second overlapping waves. The non-overlapping traveling waves distributed between the first and second overlapping waves after normalization are zeroed out, and the time difference between the first and second overlapping waves is recorded. The time difference is used to characterize the round-trip time from the fault point to the near-end measurement point.

[0009] The amplitudes of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling wave obtained by the exchange of the power distribution terminals at both ends of the fault section are compared to determine the power distribution terminal near the fault.

[0010] The fault distance is determined by the time difference of the nearby power distribution terminal, and the fault distance is reported.

[0011] According to the aforementioned asynchronous double-ended traveling wave ranging method for distribution networks, the method involves acquiring three-phase voltage signals of the line before and after a fault by using distributed distribution terminals located at feeder branch points and feeder start and end points, including:

[0012] The three-phase voltage signals of the line are acquired by distributed distribution terminals located at feeder branch points and feeder ends for 1 / 4 power frequency cycle before and 1 / 2 power frequency cycle after the fault, wherein the sampling frequency of the three-phase voltage signals is 10MHz.

[0013] According to the aforementioned asynchronous two-terminal traveling wave ranging method for distribution networks, the line-mode voltages are obtained by performing Karenbauer transform on the three-phase voltage signals of the line, and then Haar wavelet transform is performed on the line-mode voltages to obtain the wavefront information of the exchanged Haar wavelets of the distribution terminals at both ends of the fault. The exchanged Haar wavelets are then processed with detail coefficients, including:

[0014] The Karenbauer transform matrix is ​​used as a decoupling method to perform phase-mode transformation on the three-phase voltage signal of the line.

[0015] ,

[0016] in,u α , u β These are the line-mode components that form a circuit through phases AB and AC, respectively. u 0 represents the zero-mode component of the circuit formed by the three phases ABC and ground;

[0017] Furthermore, Haar wavelet transform is used to extract the wavefront information of the traveling wave, thereby obtaining the arrival time of the traveling wave at each measurement point;

[0018] Discrete wavelet analysis is used to extract detail coefficients, and the sampling point interval is reduced to half that of the original signal so that the +1 or -1 pulse can be preserved using Haar wavelets.

[0019] According to the aforementioned asynchronous double-ended traveling wave ranging method for distribution networks, the non-overlapping traveling waves distributed between the first and second overlapping waves after normalization are zeroed out, and the time difference between the first and second overlapping waves is recorded, including:

[0020] The first reference time is determined based on the point where the maximum values ​​of the first wavefronts of the reflected wavefront signals from both ends coincide.

[0021] The second reference time of the reflected wavefront from the fault point to the near-end measurement point is determined based on the second coincident wave after the reflected wavefront signals at both ends are aligned and overlapped.

[0022] Wavefront removal processing is performed on the first and second overlapping waves, including...

[0023] ,

[0024] ,

[0025] ,

[0026] Among them For the detail coefficient signal obtained by wavelet analysis at the upstream endpoint of the fault point, At the downstream end of the fault point, and They are respectively to and The signals obtained by aligning and adding the maxima of the first wavefront and by subtracting the maxima are: This is the overlapping signal after the detail coefficient signals obtained from wavelet analysis at both ends are aligned.

[0027] According to the asynchronous two-terminal traveling wave ranging method for distribution networks, the amplitudes of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling waves exchanged between the distribution terminals at both ends of the fault section are compared to determine the distribution terminal near the fault, including:

[0028] By comparing the second coincidence points , The amplitude of the wavefront is used to determine the near and far ends, including the use of formulas.

[0029]

[0030]

[0031] in, The voltage amplitude at the endpoint. When 'a' represents the voltage value at the near-end terminal, When the value is 'b', it represents the voltage value at the far end. A value of 1 indicates the first overlapping wave. When the value is 2, it represents the second coincident wave. The wave impedance of the traveling wave before it passes through the discontinuity point. The wave impedance after the traveling wave passes through the discontinuity point. , Let be the refraction and reflection coefficient of the voltage traveling wave, and Therefore, based on the wavefront voltage values ​​of the first and second ends, the fault proximal end is determined.

[0032] According to the aforementioned asynchronous two-terminal traveling wave ranging method for distribution networks, determining the fault proximity end based on the wavefront voltage values ​​of the first and second ends includes:

[0033] Through formula

[0034]

[0035] Determine the proximal end and distal end of the first end and the second end, wherein =1 represents the midpoint, where K a2 The amplitude of the wavelet transform coefficients at the first end of the second coincident wave. K b2 The amplitude of the second wavelet transform coefficient of the second coincident wave. K tw This is the ratio of the two.

[0036] According to the aforementioned asynchronous two-terminal traveling wave ranging method for distribution networks, the method further includes:

[0037] The fault distance is calculated for the near-end distribution terminal using the following formula:

[0038]

[0039] in Let V be the traveling wave velocity of the linear mode component. For the first overlap time, The time of the second overlap wave. This represents the distance between the fault point and the nearest measurement point.

[0040] According to the aforementioned asynchronous two-terminal traveling wave ranging method for distribution networks, the method further includes:

[0041] If a ground fault is detected in the distribution network, the fault section is automatically located and isolated through the feeder, communication is established between the distribution terminals at both ends of the fault section to exchange fault information, the fault distance is calculated based on the fault information exchanged between the terminals at both ends, the fault near end is identified, and the terminal at the fault near end establishes communication with the master station and uploads the fault distance.

[0042] This invention also discloses an asynchronous two-end traveling wave ranging device for power distribution networks, comprising:

[0043] The first module is used to collect the three-phase voltage signals of the line before and after the fault by using distributed distribution terminals set at the feeder branch points and the beginning and end of the feeder, according to the traveling wave ranging request.

[0044] The second module is used to perform Karenbauer transformation on the three-phase voltage signal of the line to obtain the line-mode voltage, perform Haar wavelet transformation on the line-mode voltage to obtain the wavefront information of the exchanged Haar wavelet of the distribution terminal at both ends of the fault, and perform detail coefficient processing on the exchanged Haar wavelet, wherein the two ends include the first end and the second end.

[0045] The third module is used to synchronize and normalize the first peak values ​​of the three-phase voltage signals of the line at the first end and the three-phase voltage signals of the line at the second end to the same time point, and determine the first coincident wave and the second coincident wave; normalize the non-coincident traveling waves distributed between the first coincident wave and the second coincident wave after normalization, and record the time difference between the first coincident wave and the second coincident wave, the time difference being used to characterize the round-trip time from the fault point to the near-end measurement point.

[0046] The fourth module is used to compare the amplitude of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling wave obtained by the exchange of the power distribution terminals at both ends of the fault section, and to determine the power distribution terminal near the fault.

[0047] The fifth module is used to determine the fault distance based on the time difference of the nearby power distribution terminal and to report the fault distance.

[0048] This invention also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium and execute the computer instructions, causing the computer device to perform the methods described above.

[0049] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0050] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0051] Figure 1 This is a flowchart illustrating the method of an embodiment of the present invention.

[0052] Figure 2 This is an equivalent model of the power distribution system in this embodiment of the invention.

[0053] Figure 3 This is a schematic diagram of the wavy reflection at both ends of the fault point in an embodiment of the present invention.

[0054] Figure 4 This is a schematic diagram of the original line mode voltage after the initial traveling waves are superimposed, according to an embodiment of the present invention.

[0055] Figure 5a and Figure 5b These are schematic diagrams comparing the initial traveling waves before and after overlap after wavelet transform according to embodiments of the present invention.

[0056] Figure 6 This is a schematic diagram comparing the non-overlapping waves before and after wavelet transform in an embodiment of the present invention.

[0057] Figure 7 This is a schematic diagram of the second overlap wavefront amplitude comparison in an embodiment of the present invention.

[0058] Figure 8 This is a schematic diagram of the asynchronous double-ended traveling wave ranging device for power distribution networks according to an embodiment of the present invention. Detailed Implementation

[0059] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings. Throughout the description, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves. Therefore, "module," "part," or "unit" can be used interchangeably. Terms such as "first," "second," etc., are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features. In the following description, the consecutive reference numerals for method steps are for ease of review and understanding. Adjusting the implementation order of steps, in conjunction with the overall technical solution of the present invention and the logical relationship between the various steps, will not affect the technical effect achieved by the technical solution of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0060] Terminology Explanation:

[0061] FTU, Power Distribution Terminal.

[0062] refer to Figure 1 It was made public Figure 1 This is a flowchart illustrating the asynchronous two-end traveling wave ranging method for distribution networks according to an embodiment of the present invention, which includes, but is not limited to, steps S100~S500:

[0063] S100, based on the traveling wave ranging request, collects the three-phase voltage signals of the line before and after the fault through distributed distribution terminals set at the feeder branch points and the beginning and end of the feeder.

[0064] In some embodiments, reference Figure 2 The equivalent model of the power distribution system shown illustrates a phase-A ground fault occurring at L6 in the power distribution line. This model is constructed using the electromagnetic transient simulation system PSCAD. Figure 2 A simulation model of a 10kV single-ended radial distribution network. The overhead line parameters are shown in Table 1.

[0065]

[0066] Table 1

[0067] All outgoing lines are Frequency Dependent (Phase) Model overhead lines, and FTU1 to FTU16 are respectively equipped with the feeder control terminal device required by this invention. Figure 3 The following are the sequence parameters of the distribution network lines. The traveling wave propagation speed of the overhead line mode is... v= 2.98507×108 m / s, the lengths of each line segment are respectively L 1 = 3km L 2 = 8.1 km L 3 = 5.1km L 4 = 6km L 5 = 5km L 6 = 7.9km L 7 = 2.8km L 8 = 6km. Assume the system simulation starts at time... t =0s, in t =0.1s line L 6. A single-phase ground fault occurs, and the distance from the fault point is... L 1. Endpoint distance 4.6km L 7. Endpoint 3.3km.

[0068] In some embodiments, each branch point of the feeder and the beginning and end of the feeder are equipped with an FTU having traveling wave detection and processing capabilities, and the FTU is equipped with distributed communication functions between adjacent FTUs to obtain the three-phase voltage signals of the line before and after the fault.

[0069] In some embodiments, the sampling frequency of the voltage waveform acquisition device is set to 10MHz, and the sampling time window length of the voltage measurement device is set to 1 / 4 of the power frequency cycle before the fault and 1 / 2 of the power frequency cycle after the fault.

[0070] S200 performs Karenbauer transformation on the three-phase voltage signal of the line to obtain the line-mode voltage. The line-mode voltage is then subjected to Haar wavelet transformation to obtain the wavefront information of the exchanged Haar wavelet of the distribution terminals at both ends of the fault. The exchanged Haar wavelet is then processed for detail coefficients, where both ends include the first end and the second end.

[0071] For example, the first end and the second end represent the power distribution terminals at both ends of the fault location.

[0072] In some embodiments, after a line fault, 2000 sampling points of 3 / 4 of the power frequency cycles recorded by FTUs at both ends of the fault section are subjected to phase mode transformation and Haar wavelet transform. The first layer after wavelet transform is read, at which point the sampling points are reduced to 1000. Then, the time of the first wave maximum of the first layer wavelet coefficients obtained by exchanging the local and remote ends is normalized to the same time point. After removing non-overlapping wavefronts, the second wavefront overlap time is read.

[0073] For example, FTUs at various points in the distribution network use a 10MHz frequency to collect instantaneous three-phase voltages at local measurement points in real time. u ma , u mb ,u mc After a fault occurs, existing feeder automation technology locates the FTUs at both ends of the fault section. The FTUs at both ends collect three-phase voltage data for the first quarter of the fault cycle and the last half of the fault cycle. At this point, the asynchronous double-ended traveling wave ranging method for distribution networks based on distributed communication of distribution terminals, as described in this invention, is applied. To eliminate the influence of electromagnetic coupling between lines, this invention uses the Karenbauer transformation matrix as a decoupling method. The phase mode transformation formula is as follows:

[0074] (1)

[0075] (1) In the formula, u α , u β These are the line-mode components that form a circuit through phases AB and AC, respectively. u 0 represents the zero-mode component of the circuit formed by the three phases ABC and ground. To avoid ranging errors caused by modulus dispersion, this invention selects linear modulus.

[0076] When a feeder fault occurs, an initial traveling wave signal is generated at the fault point and propagates from the fault point to both ends. When encountering a discontinuity, part of the traveling wave is reflected back to the fault point, while part is refracted and continues to propagate to both ends. This invention uses wavelet transform technology to extract the wavefront information of the traveling wave, thereby obtaining the arrival time of the traveling wave at each measurement point. According to the singularity theory of wavelet transform, the modulus maxima of the wavelet transform correspond one-to-one with the abrupt change points of the transient signal. To better utilize this characteristic, this invention selects a discrete Haar wavelet basis. The Haar wavelet basis is the simplest orthogonal wavelet among all orthogonal wavelets. Its orthogonal set consists of +1 and -1 pulse waveforms. In the discrete wavelet analysis for extracting detail coefficients, the sampling point interval is reduced to half that of the original signal. The wavelet basis only retains +1 or -1 pulses. The retained single-pulse information corresponds well to the abrupt change points of the transient signal, meeting the requirements of the ranging method.

[0077] S300: The first peak value of the three-phase voltage signal of the line at the first end and the first peak value of the three-phase voltage signal of the line at the second end are aligned and normalized to the same time point to determine the first overlapping wave and the second overlapping wave; the non-overlapping traveling wave distributed between the first overlapping wave and the second overlapping wave after normalization is zeroed out, and the time difference between the first overlapping wave and the second overlapping wave is recorded. The time difference is used to characterize the round-trip time from the fault point to the near end measurement point.

[0078] In some embodiments, after voltage data processing, the two FTUs at both ends obtain two sets of signals regarding the reflected wavefront. These reflected wavefront signals are exchanged via the FTU's distributed communication function. At this point, the FTUs at both ends of the fault section will receive both local and peer reflected wavefront signals. The FTU uses the point where the maximum values ​​of the first wavefronts of the reflected wavefront signals from both ends coincide as the reference time point. t 1. The second overlapping wavefront after the two are aligned is the reference time point for the reflected wavefront from the fault point to the near-end measurement point. t 2. When calculating the fault distance using the time difference between the first two overlapping wavefronts, the travel distance of the traveling wave at the measurement point and other endpoints and branch points may be less than the travel distance between the measurement point and the fault point. Other non-overlapping wavefronts will appear between the two overlapping wavefronts. Therefore, these wavefronts need to be removed using the following formula:

[0079] (2)

[0080] (3)

[0081] (4)

[0082] In the formula For the detail coefficient signal obtained by wavelet analysis at the upstream endpoint of the fault point, At the downstream end of the fault point, and They are respectively to and The signals obtained by aligning and adding the maxima of the first wavefront and by subtracting the maxima are: This is the overlapping signal after the detail coefficient signals obtained from wavelet analysis at both ends are aligned.

[0083] S400 compares the amplitude of the Haar wavelet coefficients corresponding to the second overlap time of the traveling wave obtained by the exchange of power distribution terminals at both ends of the fault section to determine the power distribution terminal near the fault.

[0084] In some embodiments, the round-trip time between the near-end measurement point and the fault point can be obtained from the FTUs at both ends of the fault segment, therefore it is also necessary to confirm the near-end measurement point. This embodiment compares the second coincidence points. , The main principle of determining the near and far ends based on the amplitude of the wavefront is as follows:

[0085] (5)

[0086] (6)

[0087] refer to Figure 3 The part marked with red lines, in the above formula The voltage amplitude at the endpoint. When 'a' represents the voltage value at the near-end terminal, When the value is 'b', it represents the voltage value at the far end. A value of 1 indicates the first coincidence wave. A value of 2 indicates the second coincidence wave. The wave impedance of the traveling wave before it passes through the discontinuity point. This is the wave impedance after the traveling wave passes through the discontinuity point. , The reflection and refraction coefficients of the voltage traveling wave can be obtained from (5) and (6), and Therefore, based on the comparison between the wavefront voltage value at this end and the wavefront voltage value at the opposite end, the one with the smaller amplitude is judged to be the one closer to the fault.

[0088] In some embodiments, wherein

[0089] The method for determining the fault location near the source is based on formula (7), yielding the following relationship:

[0090] (7)

[0091] In the formula K a2 The amplitude of the wavelet transform coefficients at end A of the second coincident wave. K b2 The amplitude of the wavelet transform coefficients at the B end of the second overlapping wave. K tw This is the ratio of the two.

[0092] In some embodiments, the FTU at the proximal end calculates the fault distance according to the following formula:

[0093] (8)

[0094] In equation (8) Let V be the traveling wave velocity of the linear mode component. For the first overlap time, The time of the second overlap wave. This represents the distance between the fault point and the nearest measurement point.

[0095] The S500 determines the fault distance based on the time difference of the nearby power distribution terminal and reports the fault distance.

[0096] Figure 3 This is a waveform diagram showing the reflection and refraction of light detected at the two most recent FTUs (A and B terminals) when a single-phase ground fault occurs on line L6. The diagram clearly shows that the lengths of ta1 (ta2), tb1 (tb2), and to1 (to2) are geometrically equal. Figure 4 It can also be seen that the original voltage signal corresponds to the positions of the initial wavefront and the fault reflection wavefront. From Figure 5a and Figure 5b Furthermore, it allows for a clear view of the correspondence between the traveling waves before and after the initial wavefront's first wave maximum value in time.

[0097] Figure 6 The waveforms are the first overlapping waves of the traveling wave signals at both ends. The red curve is the signal that was removed by equations (2), (3), and (4). The time of the first overlapping wave in the figure is 0.100002s, and the time of the second overlapping wave is 0.100024s. The two wave heads are 22µs apart. According to equation (7), x = 3.283km is calculated, which is 0.027km different from the set fault location of 3.3km. The error rate is only 0.5%.

[0098] Figure 7 for Figure 6 In the second overlapping wave detail, the absolute value of the amplitude of the wavefront at end A in the figure is 0.058, and the absolute value of the amplitude of the wavefront at end B is 0.04. Since 0.04 < 0.058, according to the above formulas (5) and (6), it is determined that the fault point at end B is near the end. At this time, end B corresponds to the fault point reflection wavefront. At end B, the FTU will upload the calculated fault distance to the main station.

[0099] Refer to Table 2, which provides... Figure 2 Table 2 shows the ranging results for different types of ground faults occurring on different feeders in the power distribution system shown.

[0100]

[0101] Table 2

[0102] As can be seen from Table 2, the ranging method of the present invention has high accuracy in ground fault ranging.

[0103] According to embodiments of the present invention, the technical solution of the present invention has at least the following beneficial effects: it can accurately measure the fault distance; the method is not affected by transition resistance, initial phase angle, or system grounding method; the method does not require dual-end synchronous communication; the method has high ranging accuracy and short time requirement, meeting the requirements of existing distribution network projects.

[0104] As shown in Figure 10, this embodiment of the invention also provides an asynchronous dual-end traveling wave ranging device for power distribution networks, which includes a first module 801, a second module 802, a third module 803, a fourth module 804 and a fifth module 805.

[0105] The system comprises three modules: The first module collects three-phase voltage signals of the line before and after a fault by using distributed distribution terminals located at feeder branch points and feeder ends, based on traveling wave ranging requests; the second module performs Karenbauer transform on the three-phase voltage signals to obtain line-mode voltages, then performs Haar wavelet transform on the line-mode voltages to obtain the wavefront information of the exchanged Haar wavelets at both ends of the fault, and performs detail coefficient processing on the exchanged Haar wavelets, where both ends include the first end and the second end; the third module connects the three-phase voltage signals of the line at the first end with the three-phase voltage signals of the line at the second end. The first peak value of the signal is aligned and normalized to the same time point to determine the first and second coincident waves. The non-coincident traveling waves distributed between the first and second coincident waves after normalization are zeroed out, and the time difference between the first and second coincident waves is recorded. The time difference is used to characterize the round-trip time from the fault point to the near-end measurement point. The fourth module is used to compare the amplitude of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling waves exchanged between the distribution terminals at both ends of the fault section to determine the distribution terminal near the fault. The fifth module is used to determine the fault distance based on the time difference of the near-end distribution terminals and report the fault distance.

[0106] Exemplarily, with the cooperation of the first, second, third, fourth, and fifth modules in the device, the embodiment device can implement any of the aforementioned asynchronous two-terminal traveling wave ranging methods for distribution networks. Specifically, based on the traveling wave ranging request, distributed distribution terminals located at feeder branch points and feeder heads and ends collect the three-phase voltage signals of the line before and after the fault. After performing Karenbauer transform on the three-phase voltage signals, line-mode voltages are obtained. These line-mode voltages are then subjected to Haar wavelet transform to obtain the wavefront information of the exchanged Haar wavelets at both ends of the fault. Detail coefficient processing is then performed on the exchanged Haar wavelets, where both ends include the first... The method involves aligning the first peak values ​​of the three-phase voltage signals at the first and second ends of the line to the same time point, thus determining the first and second overlapping waves. The non-overlapping traveling waves distributed between the first and second overlapping waves are normalized to zero, and the time difference between the first and second overlapping waves is recorded. This time difference characterizes the round-trip time from the fault point to the near-end measurement point. The amplitude of the Haar wavelet coefficients corresponding to the second overlap time of the traveling waves exchanged between the distribution terminals at both ends of the fault section is compared to determine the distribution terminal near the fault. The fault distance is determined based on the time difference between the near-end distribution terminals, and the fault distance is reported. According to embodiments of the present invention, the technical solution of the present invention has at least the following beneficial effects: it can accurately measure the fault distance; the method is not affected by transition resistance, initial phase angle, or system grounding method; the method does not require dual-end synchronous communication; the method has high ranging accuracy and short time requirement, meeting the requirements of existing distribution network projects.

[0107] This invention also provides a computer-readable storage medium storing a program that is executed by a processor to implement the asynchronous two-terminal traveling wave ranging method for power distribution networks as described above.

[0108] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this invention are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is altered and sub-operations described as part of a larger operation are executed independently.

[0109] This invention also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium and execute the computer instructions, causing the computer device to perform the aforementioned asynchronous two-terminal traveling wave ranging method for power distribution networks.

[0110] Furthermore, although the invention has been described in the context of functional modules, it should be understood that, unless otherwise stated, one or more of the described functions and / or features may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the invention. Rather, given the properties, functions, and internal relationships of the various functional modules in the apparatus disclosed herein, the actual implementation of the module will be understood within the scope of conventional skill of an engineer. Therefore, those skilled in the art can implement the invention as set forth in the claims using ordinary techniques without excessive experimentation. It is also understood that the specific concepts disclosed are merely illustrative and not intended to limit the scope of the invention, which is determined by the full scope of the appended claims and their equivalents.

[0111] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0112] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0113] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0114] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0115] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0116] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0117] The above is a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A power distribution network asynchronous double-end traveling wave distance measurement method, characterized in that, include: Based on the traveling wave ranging request, the three-phase voltage signals of the line before and after the fault are collected by distributed distribution terminals set at the feeder branch points and the beginning and end of the feeder. After performing Karenbauer transformation on the three-phase voltage signal of the line, the line-mode voltage is obtained. The line-mode voltage is then subjected to Haar wavelet transformation to obtain the wavefront information of the exchanged Haar wavelet of the distribution terminal at both ends of the fault. The exchanged Haar wavelet is then processed for detail coefficients, where both ends include a first end and a second end. The first peak values ​​of the three-phase voltage signals of the line at the first end and the three-phase voltage signals of the line at the second end are aligned and normalized to the same time point to determine the first and second overlapping waves. The non-overlapping traveling waves distributed between the first and second overlapping waves after normalization are zeroed out, and the time difference between the first and second overlapping waves is recorded. The time difference is used to characterize the round-trip time from the fault point to the near-end measurement point. The amplitudes of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling wave obtained by the exchange of the power distribution terminals at both ends of the fault section are compared to determine the power distribution terminal near the fault. The fault distance is determined by the time difference of the nearby power distribution terminal, and the fault distance is reported.

2. The power distribution network unsynchronized double-ended traveling wave distance measurement method according to claim 1, characterized in that, The method of collecting three-phase voltage signals of the line before and after a fault through distributed distribution terminals set at feeder branch points and feeder start and end points includes: The three-phase voltage signals of the line are acquired by distributed distribution terminals located at feeder branch points and feeder ends for 1 / 4 power frequency cycle before and 1 / 2 power frequency cycle after the fault, wherein the sampling frequency of the three-phase voltage signals is 10MHz.

3. The power distribution network unsynchronized double-ended traveling wave fault location method according to claim 1, wherein, After performing Karenbauer transform on the three-phase voltage signals of the line, line-mode voltages are obtained. Then, Haar wavelet transform is performed on these line-mode voltages to obtain the wavefront information of the exchanged Haar wavelet at both ends of the fault. Finally, detail coefficient processing is performed on the exchanged Haar wavelet, including: The Karenbauer transform matrix is ​​used as a decoupling method to perform phase-mode transformation on the three-phase voltage signal of the line. ， in, u α , u β These are the line-mode components that form a circuit through phases AB and AC, respectively. u 0 represents the zero-mode component of the circuit formed by the three phases ABC and ground; Furthermore, Haar wavelet transform is used to extract the wavefront information of the traveling wave, thereby obtaining the arrival time of the traveling wave at each measurement point; Discrete wavelet analysis is used to extract detail coefficients, and the sampling point interval is reduced to half that of the original signal so that the +1 or -1 pulse can be preserved using Haar wavelets.

4. The asynchronous double-ended traveling wave ranging method for distribution networks according to claim 3, characterized in that, The step of normalizing the non-overlapping traveling waves distributed between the first and second overlapping waves and recording the time difference between the first and second overlapping waves includes: The first reference time is determined based on the point where the maximum values ​​of the first wavefronts of the reflected wavefront signals from both ends coincide. The second reference time of the reflected wavefront from the fault point to the near-end measurement point is determined based on the second coincident wave after the reflected wavefront signals at both ends are aligned and overlapped. Wavefront removal processing is performed on the first and second overlapping waves, including... ， ， ， Among them For the detail coefficient signal obtained by wavelet analysis at the upstream endpoint of the fault point, At the downstream end of the fault point, and They are respectively to and The signals obtained by aligning and adding the maxima of the first wavefront and by subtracting the maxima are: This is the overlapping signal after the detail coefficient signals obtained from wavelet analysis at both ends are aligned.

5. The asynchronous double-ended traveling wave ranging method for distribution networks according to claim 4, characterized in that, The step of comparing the amplitudes of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling wave obtained by the exchange of the power distribution terminals at both ends of the fault section to determine the power distribution terminal near the fault includes: By comparing the second coincidence points , The amplitude of the wavefront is used to determine the near and far ends, including the use of formulas. in, The voltage amplitude at the endpoint. When 'a' represents the voltage value at the near-end terminal, When the value is 'b', it represents the voltage value at the far end. A value of 1 indicates the first overlapping wave. When the value is 2, it represents the second coincident wave. The wave impedance of the traveling wave before it passes through the discontinuity point. The wave impedance after the traveling wave passes through the discontinuity point. , Let be the refraction and reflection coefficient of the voltage traveling wave, and Therefore, based on the wavefront voltage values ​​of the first and second ends, the fault proximal end is determined.

6. The asynchronous double-ended traveling wave ranging method for distribution networks according to claim 5, characterized in that, The step of determining the fault proximal end based on the wavefront voltage values ​​of the first and second ends includes: Through formula Determine the proximal end and distal end of the first end and the second end, wherein =1 represents the midpoint, where K a2 The amplitude of the wavelet transform coefficients at the first end of the second coincident wave. K b2 The amplitude of the second wavelet transform coefficient of the second coincident wave. K tw This is the ratio of the two.

7. The asynchronous double-ended traveling wave ranging method for distribution networks according to claim 6, characterized in that, The method further includes: The fault distance is calculated for the near-end distribution terminal using the following formula: in Let V be the traveling wave velocity of the linear mode component. For the first overlap time, The time of the second overlap wave. This represents the distance between the fault point and the nearest measurement point.

8. The asynchronous double-ended traveling wave ranging method for distribution networks according to claim 1, characterized in that, The method further includes: If a ground fault is detected in the distribution network, the fault section is automatically located and isolated through the feeder, communication is established between the distribution terminals at both ends of the fault section to exchange fault information, the fault distance is calculated based on the fault information exchanged between the terminals at both ends, the fault near end is identified, and the terminal at the fault near end establishes communication with the master station and uploads the fault distance.

9. A non-synchronous double-ended traveling wave ranging device for power distribution networks, characterized in that, include: The first module is used to collect the three-phase voltage signals of the line before and after the fault by using distributed distribution terminals set at the feeder branch points and the beginning and end of the feeder, according to the traveling wave ranging request. The second module is used to perform Karenbauer transformation on the three-phase voltage signal of the line to obtain the line-mode voltage, perform Haar wavelet transformation on the line-mode voltage to obtain the wavefront information of the exchanged Haar wavelet of the distribution terminal at both ends of the fault, and perform detail coefficient processing on the exchanged Haar wavelet, wherein the two ends include the first end and the second end. The third module is used to synchronize and normalize the first peak values ​​of the three-phase voltage signals of the line at the first end and the three-phase voltage signals of the line at the second end to the same time point, and determine the first coincident wave and the second coincident wave; normalize the non-coincident waves distributed between the first coincident wave and the second coincident wave after normalization, and record the time difference between the first coincident wave and the second coincident wave, the time difference being used to characterize the round-trip time from the fault point to the near-end measurement point. The fourth module is used to compare the amplitude of the Haar wavelet coefficients corresponding to the second coincidence time of the traveling wave obtained by the exchange of the power distribution terminals at both ends of the fault section, and to determine the power distribution terminal near the fault. The fifth module is used to determine the fault distance based on the time difference of the nearby power distribution terminal and to report the fault distance.

10. A computer-readable storage medium, characterized in that, The storage medium stores a program, which is executed by a processor to implement the asynchronous two-end traveling wave ranging method for distribution networks as described in any one of claims 1-8.

Images