A method, system and device for measuring distance of power cable by traveling wave

Abstract

The present application relates to the technical field of traveling wave ranging, and specifically to a traveling wave ranging method, system and device for power cable, the method comprising: obtaining a traveling wave receiving signal after reflection by transmitting a pulse signal through a traveling wave rangefinder; screening out suspected reflection signals from the traveling wave receiving signal; screening out the suspected reflection signals closest to the position from all ranging points respectively and classifying them into the same category; for any suspected reflection signal of each type of signal, the energy amplitude in different frequency ranges and the rate of change of the propagation path length are used to screen out some types of signals from the suspected reflection signal; and determining the traveling wave fault ranging result of the cable. The present application aims to identify the reflected signal and the interference signal according to the frequency domain attenuation characteristics of the reflected signal, which can effectively avoid the influence of the interference signal on the cable fault location and improve the accuracy of the traveling wave ranging.

Description

Technical Field

[0001] The present application relates to the technical field of traveling wave ranging, and in particular to a method, system and device for traveling wave ranging of a power cable. Background Art

[0002] In the construction of smart grids, power cables are combined with advanced monitoring and control technologies to achieve real-time monitoring and data transmission, improving the management and dispatching capabilities of power systems. State Grid has a wide range of applications in these areas, and has improved the performance and reliability of power cables by continuously introducing new technologies and equipment.

[0003] Traveling wave ranging is a method for locating faults in power cables. It can quickly locate the fault location of the cable and help to quickly repair the power system. It inputs a traveling wave into the cable. When the traveling wave encounters the fault location in the cable, the impedance of the fault location is greater than that of the normal location, so the pulse signal will be reflected at the fault location and a reflected wave will be generated. By collecting the reflected wave at the pulse signal input location and calculating the time difference between transmitting the traveling wave and receiving the reflected wave, the distance from the fault location to the traveling wave input location can be calculated, thereby completing the fault location.

[0004] Although traveling wave ranging can accurately measure the fault location after obtaining the reflected wave, there are always various interference signals in the cable. Unconventional faults such as lightning strikes, wildfires and small fault angles will generate interference signals inside the cable. The interference signals will affect the recognition of the reflected wave, resulting in errors in the recognition of the reflected wave, and then inaccurate measurement of the fault location. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of this application is to provide a power cable traveling wave ranging method, system and device, and the technical solutions adopted are as follows:

[0006] In a first aspect, an embodiment of the present application provides a method for measuring distance of a power cable by traveling waves, the method comprising the following steps:

[0007] At the distance measuring points set at different positions of the cable, a traveling wave rangefinder transmits a pulse signal to obtain a reflected traveling wave receiving signal;

[0008] By segmenting the traveling wave received signal, some signals are filtered out, specifically:

[0009] A1, dividing the traveling wave receiving signal into several signal segments, and screening out the suspected reflection signal;

[0010] A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals closest to the position are respectively selected from all ranging points and classified into the same category;

[0011] A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; obtaining the energy amplitude of each frequency band signal;

[0012] A4, determine the fault position of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal based on the distance between the ranging point where the suspected reflection signal is located and the fault position of the signal in the same type;

[0013] A5, for any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths, and the attenuation slope of any suspected reflection signal in any frequency range is calculated by the energy amplitude in different frequency ranges and the rate of change of the propagation path length, and some types of signals are screened out from the suspected reflection signal using the attenuation slope;

[0014] The traveling wave fault location result of the cable is determined by the attenuation slope distribution of each suspected reflection signal among all the remaining signals after screening.

[0015] Preferably, the suspected reflection signal is obtained by screening the signal energy of all signal segments in the traveling wave received signal.

[0016] Preferably, the signal energy is the average of the absolute values ​​of all elements in the signal segment where the signal energy is located.

[0017] Preferably, the method for obtaining the position of the suspected reflection signal on the cable is:

[0018] Obtain the distance between the time when the maximum value is located and the distance measurement point where the suspected reflected signal to which it belongs is located, and record it as the traveling wave transmission distance;

[0019] The position of the suspected reflected signal on the cable is determined by using the distance and the position of the distance measurement point where the suspected reflected signal is located on the cable.

[0020] Preferably, the method of classifying into the same category is: for any suspected reflection signal in the first ranging point, select the suspected reflection signal closest to the any suspected reflection signal from all other ranging points, and record it as the same category signal of the any suspected reflection signal.

[0021] Preferably, the energy amplitude is the average value of the absolute values ​​of all elements in the signal of the corresponding frequency band.

[0022] Preferably, calculating the attenuation slope of any suspected reflection signal in any frequency range by using its energy amplitude in different frequency ranges and the rate of change of the propagation path length, and filtering out part of the interference signal from the suspected reflection signal by using the attenuation slope, comprises:

[0023] The attenuation slope of the vth suspected reflection signal in the uth type signal in the eth frequency range , the expression is: ; In the formula, is the attenuation slope of the vth suspected reflection signal in the eth frequency range, , are the energy amplitudes of the v+1th and vth suspected reflection signals in the eth frequency range, , are the propagation path lengths of the v+1th and vth suspected reflection signals respectively; when and Equal, let is equal to 0;

[0024] When the u-th type signal has an attenuation slope greater than 0, the u-th type signal is screened out.

[0025] Preferably, the attenuation slope distribution of each suspected reflection signal among all types of signals remaining after screening is used to determine the traveling wave fault location result of the cable, including:

[0026] When there are no remaining class signals after screening, the data are recollected for analysis;

[0027] When only one type of signal remains after screening, the fault position of this type of signal on the cable is taken as the traveling wave fault location result;

[0028] Otherwise, for each suspected reflection signal in all the class signals after screening, calculate the degree of confusion of all attenuation slopes of each suspected reflection signal; the maximum degree of confusion corresponds to the fault position on the cable of the class signal to which the suspected reflection signal belongs, which is used as the traveling wave fault ranging result of the cable.

[0029] In a second aspect, an embodiment of the present application provides a power cable traveling wave ranging system, the ranging system comprising:

[0030] The traveling wave data acquisition module is used to acquire the reflected traveling wave receiving signal by transmitting a pulse signal through a traveling wave rangefinder at the distance measurement points set at different positions of the cable;

[0031] The traveling wave identification module is used to filter out some signals by segmenting the traveling wave received signal. Specifically:

[0032] A1, dividing the traveling wave receiving signal into several signal segments, and screening out the suspected reflection signal;

[0033] A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals closest to the position are respectively selected from all ranging points and classified into the same category;

[0034] A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; obtaining the energy amplitude of each frequency band signal;

[0035] A4, determine the fault position of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal based on the distance between the ranging point where the suspected reflection signal is located and the fault position of the signal in the same type;

[0036] A5, for any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths, and the attenuation slope of any suspected reflection signal in any frequency range is calculated by the energy amplitude in different frequency ranges and the rate of change of the propagation path length, and some types of signals are screened out from the suspected reflection signal using the attenuation slope;

[0037] The traveling wave positioning module is used to determine the traveling wave fault location result of the cable through the attenuation slope distribution of each suspected reflection signal among all types of signals remaining after screening.

[0038] In a third aspect, an embodiment of the present application further provides a power cable traveling wave ranging device, the device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of any one of the above-mentioned power cable traveling wave ranging methods when executing the computer program.

[0039] It can be seen from the above embodiments that the power cable traveling wave ranging method, system and device provided in the embodiments of the present application have at least the following beneficial effects:

[0040] When measuring the distance of the cable by traveling waves, there are interference signals caused by unconventional faults, which can easily lead to errors in the location of cable faults. In this regard, the present application sets distance measurement points at different positions of the cable, and obtains the traveling wave receiving signal through the traveling wave rangefinder; the traveling wave receiving signal is preprocessed by the waveform characteristics of the reflected signal to obtain a suspected reflection signal, and the cable position corresponding to the suspected reflection signal is marked on the cable, and the suspected reflection signals with similar marking positions are classified into the same category. For the suspected reflection signals of the same category, the average of their marked positions is taken as the fault position of the suspected reflection signals of the same category to eliminate the measurement error, and the propagation path length from the suspected reflection signal to the fault position is obtained. Further, the frequency domain features of the suspected reflection signals of the same category are extracted to obtain the energy amplitude, which characterizes the energy size of different suspected reflection signals in different frequency domains, so as to further observe the energy attenuation characteristics of the suspected reflection signals; then, for the suspected reflection signals of the same category, the attenuation slope is calculated by the energy amplitude and the propagation path length, and it is observed whether the energy attenuation characteristics of the suspected reflection signals of the same category are consistent with the energy attenuation characteristics of the reflection signals, and some interference signals are preliminarily screened out. Finally, the attenuation slope is used to calculate the attenuation intensity characteristics of the same type of suspected reflection signals, characterize the impedance of the signal reflection position, select the reflection position with the largest impedance as the final fault position, and complete the traveling wave ranging. Since this embodiment identifies the reflection signal and the interference signal according to the frequency domain attenuation characteristics of the reflection signal, it can effectively avoid the influence of the interference signal on the cable fault location and improve the accuracy of the traveling wave ranging. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A flowchart of a method for measuring distance between a power cable and a traveling wave provided in accordance with an embodiment of the present application;

[0043] Figure 2 A schematic diagram of a traveling wave receiving signal provided by an embodiment of the present application;

[0044] Figure 3 A flowchart of a specific process for filtering out some signals provided in one embodiment of the present application;

[0045] Figure 4 A schematic diagram of a suspected reflection signal provided by an embodiment of the present application;

[0046] Figure 5A schematic structural diagram of a power cable traveling wave ranging system provided for one embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of a power cable traveling wave ranging method, system and device proposed in the present application, its specific implementation, structure, features and effects in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0048] Unless otherwise specified and limited, terms such as "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such articles or devices. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the article or device including the element. In addition, the term "and\or" used herein includes any and all combinations of one or more related listed items. All technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application.

[0049] The specific scheme of a power cable traveling wave ranging method, system and device provided by the present application is described in detail below with reference to the accompanying drawings.

[0050] See also Figure 1 , which shows a flow chart of a method for measuring distance of a power cable by traveling wave provided by an embodiment of the present application, the method comprising the following steps:

[0051] The first step is to transmit a pulse signal through a traveling wave rangefinder at ranging points set at different positions of the cable to obtain the reflected traveling wave receiving signal.

[0052] The present application sets a plurality of distance measurement points on the cable, and performs traveling wave distance measurement on the faulty power cable by means of a traveling wave distance meter.

[0053] Preferably, in this embodiment, the target cable is a cable with a length of 30 kilometers. Starting from the left side of the cable, a ranging point is set every 5 kilometers, and a total of K=7 ranging points are set. In other implementations of the embodiment of the present application, the interval length of the ranging point, the number of ranging points, etc. can be set by yourself.

[0054] At a traveling wave ranging point, a pulse signal is emitted by a traveling wave rangefinder, and the electrical signal reflected back from the cable is collected, which is recorded as a traveling wave receiving signal. In this embodiment, the sampling period of the signal is 0.01 microseconds (us), the speed of the traveling wave in the cable is 0.3 kilometers per microsecond, and the traveling wave receiving signal is a vector with a length of M. In this embodiment, M is 10000, where the mth element represents the signal strength of the traveling wave receiving signal at the mth collection moment.

[0055] In the embodiment of the present application, the schematic diagram of the traveling wave receiving signal is as shown in the attached Figure 2 shown.

[0056] exist Figure 2 In the figure, there is a traveling wave receiving signal, the horizontal axis is time, the unit is us, and the vertical axis is amplitude, the unit is V. There are relatively stable signal segments, and there are also signal segments with large fluctuations. For example, the signals between 0 to 1500 microseconds and 1900 microseconds to 3200 microseconds are stable signals, which usually means that the traveling wave has not encountered an impedance mutation point, that is, it has not encountered a fault point; for example, the signal between 1500 microseconds and 1900 microseconds is a pulse signal with large fluctuations, which is usually caused by reflection after the traveling wave encounters a fault point.

[0057] In this embodiment, data measurement is performed at 7 ranging points. Since some ranging points are in the middle of the cable, these ranging points need to be measured twice. The specific measurement method is as follows:

[0058] When the ranging point number k=1, the traveling wave receiving signal obtained by the traveling wave rangefinder is recorded as the first traveling wave receiving signal.

[0059] When the ranging point number k is an integer from 2 to K-1 (k-1>2), first set a breakpoint on the left side of the ranging point, and obtain the traveling wave receiving signal through the traveling wave rangefinder, which is recorded as the 2*k-2th traveling wave receiving signal; then cancel the breakpoint set on the right side of the ranging point, set a breakpoint on the left side of the ranging point, and obtain the traveling wave receiving signal through the traveling wave rangefinder, which is recorded as the 2*k-1th traveling wave receiving signal.

[0060] The purpose of setting breakpoints twice on the left and right sides of the ranging point is to prevent the detection signal emitted by the traveling wave rangefinder from propagating to the left and right sides of the ranging point at the same time, causing aliasing of the reflected signal and making it difficult to identify the reflected signal.

[0061] When the ranging point number k=K, the traveling wave receiving signal obtained by the traveling wave rangefinder is recorded as the Rth traveling wave receiving signal, where R=2*(k-1).

[0062] At this point, the above method can be used to obtain different ranging points on the cable, and the traveling wave rangefinder transmits a pulse signal to obtain the reflected traveling wave receiving signal.

[0063] The second step is to filter out some signals by segmenting the traveling wave received signal.

[0064] The traveling wave receiving signal includes the reflected signal returned by the transmitted pulse signal after encountering the fault location, as well as the interference signal generated by unconventional faults. It is necessary to accurately identify the reflected signal from the traveling wave receiving signal in order to complete the fault location.

[0065] Compared with the interference signal of unconventional faults, the reflected signal is generated by the reflection of the traveling wave at the fault location. The fault location has the characteristic of high impedance. Therefore, when the traveling wave is reflected, the high-frequency part is more seriously affected by the impedance of the fault location.

[0066] When the reflected signal increases in distance from the measuring point to the fault location, the energy of the reflected signal will gradually decay. Since the high-frequency part of the signal is more seriously affected by the impedance, the high-frequency part of the reflected signal decays faster than the low-frequency part.

[0067] The present application records the characteristics of differential attenuation of different frequency domain energies of the reflected signal as the measurement point and the propagation path length increase as frequency domain attenuation characteristics. The reflected signal can be identified through the frequency domain attenuation characteristics, and interference signals generated by unconventional faults can be eliminated to avoid errors in cable fault location. Preferably, in the embodiment of the present application, the specific process of filtering out some signals is as shown in the attached figure. Figure 3 As shown, specifically:

[0068] A1, divide the traveling wave receiving signal into several signal segments, and filter out the suspected reflection signals.

[0069] The traveling wave received signal is composed of a reflected signal and an interference signal, so it is necessary to mark the time period of the reflected signal and the interference signal to facilitate the subsequent further identification of the reflected signal and the interference signal. Therefore, this embodiment adopts the commonly used technical means in the field of signal processing to perform signal segmentation operations, specifically:

[0070] The reflected signal and the interference signal both appear as signal pulses in the traveling wave receiving signal. Therefore, in this embodiment, the reflected signal and the interference signal are both recorded as signal segments, and the suspected reflected signal is extracted from the traveling wave receiving signal.

[0071] Preferably, this embodiment uses the traveling wave receiving signal of the k-th ranging point as input, and adopts the double sliding window pulse energy detection method for calculation. The necessary parameters are: the signal-to-noise ratio is 15dB, the sliding window length is 32, the energy decision threshold is 10, and the output is a number of signal segments after the traveling wave receiving signal is segmented. The number of signal segments is recorded as S. Finally, the k-th traveling wave receiving signal obtains S signal segments, of which the s-th signal segment is a low-power non-pulse signal or a suspected reflection signal. The double sliding window pulse energy detection method is a common technology in the field of data processing and will not be described in detail in this embodiment. In other implementations of the embodiments of the present application, other time-frequency analysis algorithms such as short-time Fourier transform and wavelet transform may also be used.

[0072] For the s-th signal segment, the absolute value of each element of the signal segment is first calculated, and then the absolute values ​​of all elements in the s-th signal segment are averaged, which is recorded as the signal energy of the s-th signal segment.

[0073] Since non-pulse signals are usually stable signals with low energy, and suspected reflection signals are usually signals with high energy.

[0074] Preferably, this embodiment sets an energy threshold A. If the signal energy of the s-th signal segment is greater than the energy threshold A, the s-th signal segment is considered to be a suspected reflection signal, otherwise it is considered to be a non-pulse signal.

[0075] In other implementations of the embodiments of the present application, the signal energy of all signal segments in the traveling wave received signal may be segmented by adaptive thresholds, and the signal segments corresponding to the signal energy greater than the segmentation threshold are recorded as suspected reflection signals, and vice versa as non-pulse signals. The number of suspected reflection signals in the traveling wave received signal at the kth ranging point is recorded as H.

[0076] Preferably, in this embodiment, the value of the energy threshold A is set to 4, and in other implementations of the embodiments of the present application, it can also be set by the implementer.

[0077] Finally, by analyzing the traveling wave receiving signal at the kth ranging point, H suspected reflection signals can be obtained.

[0078] In the embodiment of the present application, the schematic diagram of the suspected reflection signal is as shown in the attached Figure 4 shown.

[0079] exist Figure 4 The signal in the middle is the traveling wave receiving signal between 1500 milliseconds and 1900 milliseconds. The horizontal axis is time, the unit is us, and the vertical axis is amplitude, the unit is V. This section of the pulse signal with large signal fluctuations is usually caused by reflection after the traveling wave encounters the fault point. After being extracted, it is recorded as a suspected reflection signal.

[0080] A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals with the closest positions are respectively selected from all ranging points and classified into the same category.

[0081] In traveling wave ranging, the time when the reflected signal is the largest is usually recorded as the reflection time of the signal.

[0082] Preferably, in this embodiment, after calculating the absolute values ​​of all elements in the hth suspected reflection signal of the kth ranging point, the time at which the element with the maximum absolute value corresponds is found and recorded as the reflection time of the hth suspected reflection signal. .

[0083] In particular, if the suspected reflection signal has multiple maximum absolute values, the element corresponding to the maximum absolute value on the leftmost side is selected.

[0084] In other implementations of the embodiments of the present application, the element position corresponding to the maximum absolute value on the far right may also be used as the position of the suspected reflection signal on the cable.

[0085] Then, the distance between the time at which the element is located and the distance measurement point at which the suspected reflection signal to which it belongs is located is obtained, and the position of the suspected reflection signal on the cable is obtained in combination with the parity of h.

[0086] The method for obtaining the distance in this embodiment is specifically as follows:

[0087] Assume that the reflection time of the hth suspected reflection signal at the kth ranging point is , then according to the sampling period of 0.01 microseconds and the traveling wave speed of 0.3 kilometers per microsecond, the distance between the kth ranging point and the reflection time can be calculated Kilometers, will It is recorded as the traveling wave transmission distance between the kth ranging point and the reflection moment.

[0088] The traveling wave transmission distance is the distance that the traveling wave propagates in the cable. Since the traveling wave propagates back and forth between the ranging point and the reflection position, the traveling wave transmission distance multiplied by 0.5 represents the distance between the reflection position and the ranging point where it is located.

[0089] Among them, combined with the parity of h, the specific reason analysis for obtaining the position of the suspected reflection signal on the cable is:

[0090] If the number h of the hth suspected reflection signal is an odd number, then the hth suspected reflection signal is on the right side of the kth ranging point, and its distance from the first ranging point on the cable is km; if the number h is an even number, the hth suspected reflection signal is on the left side of the kth ranging point, and its distance from the first ranging point on the cable is km.

[0091] It should be noted that the odd or even number represents the measurement direction of the signal measurement. When the number is odd, the measurement direction is to the right of the ranging point, otherwise the measurement direction is to the right of the ranging point. Multiply by the distance between the measuring points kilometers, determine the location of the ranging point on the cable; then, add or subtract the distance from the ranging point to the reflection location from the location of the ranging point on the cable , the specific position of the suspected reflected signal on the cable can be obtained.

[0092] In particular, if the position of the hth suspected reflection signal is Between 0 and 30 km, that is, within the actual length of the cable, the first A mark is made at the position of 1 meter, and it is considered that there is a suspected reflection signal at the marked position. If it is not between 0 and 30 km, the suspected reflection signal is considered to be a signal generated after multiple reflections and will not participate in subsequent calculations.

[0093] For the reflection signal generated by the fault position on the cable, it will be identified as a suspected reflection signal at different ranging points, so it is necessary to classify the suspected reflection signals with similar distances into the same type of signals for processing. Therefore, in this embodiment, the suspected reflection signals with the closest position are screened out from all ranging points and classified into the same type. Preferably, the classification method in this embodiment is specifically as follows:

[0094] For any suspected reflection signal in the first ranging point, select the suspected reflection signal closest to the suspected reflection signal from all other ranging points and record it as the same type signal of the suspected reflection signal. The distance between the suspected reflection signals refers to the position difference between the two suspected reflection signals on the cable.

[0095] In this embodiment, only all the suspected reflection signals in the first ranging point are classified into the same type of signals. In other implementations of the embodiments of the present application, the same type of signals can also be classified into the second ranging point, the third ranging point, etc.

[0096] For example, for the first ranging point, all the corresponding suspected reflection signals are obtained. In this embodiment, there are H suspected reflection signals in the first traveling wave received signal. For the h-th suspected reflection signal of the first ranging point, a suspected reflection signal closest to the h-th suspected reflection signal of the first ranging point is selected from all the suspected reflection signals belonging to the second ranging point as a similar signal to the h-th suspected reflection signal of the first ranging point; and so on, the same operation is performed for the third, fourth, fifth, sixth, and seventh ranging points, and a suspected reflection signal closest to the h-th suspected reflection signal of the first ranging point is selected as a similar signal to the h-th suspected reflection signal of the first ranging point.

[0097] Finally, for the first ranging point, H types of signals can be obtained, and there are K suspected reflection signals in the hth type of signal. Each type of signal divides the suspected reflection signals with similar distances into one type, which can characterize the suspected reflection signals near a specific position on the cable. If the position is the fault position, the suspected reflection signals at this position should all be reflection signals, and then these suspected reflection signals should conform to the frequency domain attenuation characteristics of the reflection signal.

[0098] A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; and obtaining the energy amplitude of each frequency band signal.

[0099] For suspected reflected signals, this embodiment identifies reflected signals and interference signals based on the frequency domain attenuation characteristics of the reflected signals, so it is necessary to extract the frequency domain characteristics of the reflected signals; the frequency domain attenuation characteristics are mainly reflected in the energy changes of the suspected reflected signals, so this embodiment analyzes the frequency domain characteristics through the energy amplitude of the suspected reflected signals.

[0100] Preferably, in this embodiment, for the kth suspected reflection signal in the uth type signal, the kth suspected reflection signal is used as input and calculated by a bandpass filter, wherein a total of E types of bandpass filters are used, and their frequency ranges are: 0 to 5kHz, 5kHz to 50kHz, 50kHz to 250kHz, 250kHz to 750kHz, 750kHz to 1.5MHz, 1.5MHz to 2.5MHz, 2.5MHz to 4MHz, 4MHz to 6MHz, and finally E signals are output respectively. Among them, the eth signal is recorded as the eth frequency segment signal of the kth suspected reflection signal in the uth type signal.

[0101] In this embodiment, E takes a value of 8. In other implementations of the embodiments of the present application, a band-stop filter may be used to set a reasonable frequency range, thereby outputting signals in each frequency range.

[0102] Furthermore, the energy amplitude of the e-th frequency band signal is calculated by calculating the absolute values ​​of all elements in the e-th frequency band signal, and then calculating the average of the absolute values, which is recorded as the energy amplitude of the e-th frequency band signal The energy amplitude can characterize the energy of the kth suspected reflection signal at different frequencies. In this type of signal, the frequency domain attenuation characteristics of the signal can be observed through the energy amplitude.

[0103] A4, determine the fault location of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal by taking the distance between the ranging point where the signal is located and the fault location of the signal of the same type.

[0104] According to the frequency domain attenuation characteristics of the reflected signal, the energy amplitude of the reflected signal in different frequency domains decreases with the increase of the traveling wave transmission distance, showing a monotonically decreasing characteristic; at the same time, the attenuation strength of the energy amplitude at different frequencies is different. The higher the frequency, the more serious the attenuation of the energy amplitude. As the frequency increases, the energy attenuation of different components in the signal becomes more serious, showing a monotonically decreasing characteristic;

[0105] Most interference signals are generated by factors such as non-fault lightning strikes and wildfires. Such signals are usually not affected by the sudden increase in impedance when propagating in the cable, so their energy attenuation in the frequency domain usually does not show this monotonic decrease characteristic. Therefore, this embodiment further screens out non-reflected signals based on the monotonic decrease characteristic that occurs when the reflected signal attenuates in the frequency domain.

[0106] When obtaining the u-th type of signal, signals with similar distances are classified into one type of signal. However, there are measurement errors between the positions of the K suspected reflection signals on the cable. To eliminate this error, the fault position is calculated for the u-th type of signal.

[0107] Preferably, in this embodiment, for the u-th type signal, positions of K suspected reflection signals on the cable are obtained, and the K positions are averaged and recorded as the fault position of the u-th type signal.

[0108] Furthermore, for the kth suspected reflection signal in the uth type signal, the distance between its ranging point and the fault location of the signal in its category is calculated, which is recorded as the propagation path length of the kth suspected reflection signal in the uth type signal That is, the absolute value of the difference between the position of the distance measurement point where the k-th suspected reflection signal is located on the cable and the fault position of the signal of the same type is calculated to characterize the distance between the k-th suspected reflection signal and the fault position in the u-th signal to which it belongs, so as to evaluate the attenuation characteristic intensity of the reflected signal energy as the propagation distance increases.

[0109] A5. For any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths. The attenuation slope of any suspected reflection signal in any frequency range is calculated based on the energy amplitude in different frequency ranges and the rate of change of the propagation path length. The attenuation slope is used to screen out some types of signals from the suspected reflection signal.

[0110] Finally, for the u-th type of signal, the energy amplitudes of the e-th frequency band signals in the K suspected reflection signals are arranged in ascending order according to the propagation path length of the suspected reflection signals, and a sequence is obtained, which is recorded as the frequency domain feature sequence. The v-th element in the sequence is the energy amplitude of the v-th suspected reflection signal in the e-th frequency range. .

[0111] In other implementations of the embodiments of the present application, the e-th frequency band signal among the K suspected reflection signals may be arranged in descending order of propagation path length.

[0112] When v is equal to K, there is no need to calculate the attenuation slope; when v is less than K, calculate the attenuation slope of the vth suspected reflection signal in the eth frequency range. , the expression is:

[0113]

[0114] In the formula, is the attenuation slope of the vth suspected reflection signal in the eth frequency range, , are the energy amplitudes of the v+1th and vth suspected reflection signals in the eth frequency range, , are the propagation path lengths of the v+1th and vth suspected reflection signals respectively.

[0115] In particular, when and Equal, let Equal to 0, indicating that the propagation path lengths of the vth and v+1th suspected reflection signals are the same, and their energy amplitudes should be the same and will not change with the propagation path length.

[0116] For the u-th signal, there are K suspected reflection signals, each of which has E frequency ranges. Therefore, the u-th signal can be calculated as Attenuation slope. The attenuation slope represents the characteristic that the energy amplitude of the suspected reflection signal decreases as the propagation path length increases. When the attenuation slope is less than or equal to 0, it can be considered that the energy amplitude of the suspected reflection signal is attenuating, and the corresponding kth and k+1th suspected reflection signals may be reflection signals, otherwise they are not reflection signals.

[0117] Therefore, for the u-th signal, its corresponding G attenuation slopes are obtained. If all signals in the u-th signal are reflection signals, the G attenuation slopes should be less than or equal to 0. Otherwise, it is considered that the u-th signal contains interference signals and cannot reflect a specific fault location.

[0118] Furthermore, the attenuation slope can be used to determine whether each type of signal contains interference signals:

[0119] Preferably, in this embodiment, when all attenuation slopes are calculated for the u-th type signal, if there is an attenuation slope greater than 0, it is considered that the u-th type signal contains an interference signal, which does not reflect a specific fault location.

[0120] Finally, all U-type signals are judged, and various types of signals without interference signals are further screened out. In particular, if all U-type signals are considered to contain interference signals, it is considered that the interference with the measurement data is too serious, and the traveling wave ranging cannot be completed, and the data needs to be collected again.

[0121] The third step is to determine the cable traveling wave fault location result by distributing the attenuation slope of each suspected reflection signal among all the remaining types of signals after screening.

[0122] When it is determined through the attenuation monotonic characteristics of step A5 that only one type of signal does not contain an interference signal, the corresponding fault position is used as the final traveling wave fault distance measurement result.

[0123] When the interference signal is generated by factors such as a small fault angle, since it is also an interference signal caused by impedance change, this part of the interference signal also satisfies the attenuation monotonic feature and cannot be distinguished from the reflection signal by the attenuation monotonic feature. Therefore, this example calculates the attenuation strength feature. The larger the attenuation strength feature, the greater the impedance of the signal reflection position, and the more likely it is the fault position rather than the small fault angle.

[0124] Preferably, in this embodiment, for the u-th type signal remaining after screening, the standard deviation of all attenuation slopes of its v-th suspected reflection signal is obtained, which is recorded as the attenuation intensity feature of the v-th suspected reflection signal. In other implementations of the embodiments of the present application, the variance of all attenuation slopes of the v-th suspected reflection signal can also be used as the attenuation intensity feature of its corresponding v-th suspected reflection signal.

[0125] It should be understood that the greater the attenuation intensity feature is, and the more obvious the feature that the attenuation slope decreases with increasing frequency is, the greater the impedance of the corresponding signal reflection position is, and the more likely it is a fault position rather than a small fault angle.

[0126] Finally, among all types of signals judged to contain no interference signals, the signal type with the suspected reflection signal with the largest attenuation intensity characteristic is selected, and the fault position of this type of signal is used as the final traveling wave fault ranging result to complete the traveling wave ranging.

[0127] Since this embodiment distinguishes the reflected signal from the interference signal according to the frequency domain attenuation characteristics of the reflected signal, and completes the positioning through the reflected signal, the problem of positioning errors caused by interference signals in cable fault positioning is solved.

[0128] In this embodiment, the traveling wave ranging system of the power cable includes: a traveling wave data acquisition module, a traveling wave identification module, and a traveling wave positioning module.

[0129] The traveling wave data acquisition module is used to obtain traveling wave receiving signals at multiple ranging points, the traveling wave identification module is used to identify the reflected signal of the fault position in the traveling wave receiving signal, and the traveling wave positioning module locates the fault position according to the reflected signal to complete the traveling wave ranging.

[0130] See also Figure 5 , Figure 5 is a schematic diagram of the structure of a power cable traveling wave ranging system provided in an embodiment of the present application. In this embodiment, each unit included in the terminal is used to execute each step in an embodiment corresponding to a power cable traveling wave ranging method. Figure 5 , the power cable traveling wave ranging system includes:

[0131] The traveling wave data acquisition module is used to acquire the reflected traveling wave receiving signal by transmitting a pulse signal through a traveling wave rangefinder at the distance measurement points set at different positions of the cable;

[0132] The traveling wave identification module is used to filter out some signals by segmenting the traveling wave received signal. Specifically:

[0133] A1, dividing the traveling wave receiving signal into several signal segments, and screening out the suspected reflection signal;

[0134] A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals closest to the position are respectively selected from all ranging points and classified into the same category;

[0135] A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; obtaining the energy amplitude of each frequency band signal;

[0136] A4, determine the fault position of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal based on the distance between the ranging point where the suspected reflection signal is located and the fault position of the signal in the same type;

[0137] A5, for any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths, and the attenuation slope of any suspected reflection signal in any frequency range is calculated by the energy amplitude in different frequency ranges and the rate of change of the propagation path length, and some types of signals are screened out from the suspected reflection signal using the attenuation slope;

[0138] The traveling wave positioning module is used to determine the traveling wave fault location result of the cable through the attenuation slope distribution of each suspected reflection signal among all types of signals remaining after screening.

[0139] Based on the same inventive concept as the above method, an embodiment of the present application also provides a power cable traveling wave ranging device, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above-mentioned power cable traveling wave ranging methods are implemented.

[0140] The various embodiments in the present application are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0141] It should be noted that, unless otherwise specified and limited, terms such as "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, an element defined by the sentence "including one..." does not exclude the existence of other identical elements in the article or device including the element. In addition, the term "and\or" used herein includes any and all combinations of one or more related listed items.

[0142] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not invented by the present application.

[0143] It should be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A method for measuring distance of a power cable by traveling waves, characterized in that: The method comprises the following steps: At the distance measuring points set at different positions of the cable, a traveling wave rangefinder transmits a pulse signal to obtain a reflected traveling wave receiving signal; By segmenting the traveling wave received signal, some signals are filtered out, specifically: A1, divide the traveling wave receiving signal into several signal segments, and filter out the suspected reflection signal; A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals closest to the position are respectively selected from all ranging points and classified into the same category; A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; and obtaining the energy amplitude of each frequency band signal; A4, determine the fault position of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal based on the distance between the ranging point where the suspected reflection signal is located and the fault position of the signal in the same type; A5, for any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths, and the attenuation slope of any suspected reflection signal in any frequency range is calculated by the energy amplitude in different frequency ranges and the rate of change of the propagation path length, and some types of signals are screened out from the suspected reflection signal using the attenuation slope; The traveling wave fault location result of the cable is determined by the standard deviation of the attenuation slope of each suspected reflection signal among all the remaining signals after screening.

2. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The suspected reflection signal is obtained by screening the signal energy of all signal segments in the traveling wave received signal.

3. A power cable traveling wave ranging method as claimed in claim 2, characterized in that: The signal energy is the average value of the absolute values ​​of all elements in the signal segment where the signal energy is located.

4. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The method for obtaining the position of the suspected reflection signal on the cable is: Obtain the distance between the time when the maximum value is located and the distance measurement point where the suspected reflected signal to which it belongs is located, and record it as the traveling wave transmission distance; The position of the suspected reflected signal on the cable is determined by using the distance and the position of the distance measurement point where the suspected reflected signal is located on the cable.

5. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The method for classifying them into the same category is: for any suspected reflection signal in the first ranging point, select the suspected reflection signal closest to the any suspected reflection signal from all other ranging points, and record it as the same category signal of the any suspected reflection signal.

6. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The energy amplitude is the average value of the absolute values ​​of all elements in the signal of the corresponding frequency band.

7. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The attenuation slope of any suspected reflection signal in any frequency range is calculated by using its energy amplitude in different frequency ranges and the rate of change of the propagation path length, and part of the interference signal is filtered out from the suspected reflection signal by using the attenuation slope, including: The attenuation slope of the vth suspected reflection signal in the uth type signal in the eth frequency range , the expression is: ; In the formula, is the attenuation slope of the vth suspected reflection signal in the eth frequency range, , are the energy amplitudes of the v+1th and vth suspected reflection signals in the eth frequency range, , are the propagation path lengths of the v+1th and vth suspected reflection signals respectively; when and Equal, let is equal to 0; When the u-th type signal has an attenuation slope greater than 0, the u-th type signal is screened out.

8. A power cable traveling wave ranging method as claimed in claim 1, characterized in that: The method of determining the cable traveling wave fault location result by the standard deviation of the attenuation slope of each suspected reflection signal among all types of signals remaining after screening includes: When there are no remaining class signals after screening, the data are recollected for analysis; When only one type of signal remains after screening, the fault position of this type of signal on the cable is taken as the traveling wave fault location result; Otherwise, for each suspected reflection signal in all the class signals after screening, calculate the standard deviation of all attenuation slopes of each suspected reflection signal; the maximum standard deviation corresponds to the fault position of the class signal to which the suspected reflection signal belongs on the cable, which is used as the traveling wave fault ranging result of the cable.

9. A power cable traveling wave ranging system, implementing a power cable traveling wave ranging method as claimed in any one of claims 1 to 8, characterized in that: The ranging system comprises: The traveling wave data acquisition module is used to acquire the reflected traveling wave receiving signal by transmitting a pulse signal through a traveling wave rangefinder at the distance measurement points set at different positions of the cable; The traveling wave identification module is used to filter out some signals by segmenting the traveling wave received signal. Specifically: A1, divide the traveling wave receiving signal into several signal segments, and filter out the suspected reflection signal; A2, using the time at which the maximum value of the absolute values ​​of all elements in the suspected reflection signal is obtained, the position of the suspected reflection signal on the cable is obtained; the suspected reflection signals closest to the position are respectively selected from all ranging points and classified into the same category; A3, dividing each suspected reflection signal in each type of signal into several frequency ranges to obtain several frequency band signals; and obtaining the energy amplitude of each frequency band signal; A4, determine the fault position of the same type of suspected reflection signal based on the average level of the position of the same type of signal on the cable; for any suspected reflection signal in any type of signal, determine the propagation path length of any suspected reflection signal in any type of signal based on the distance between the ranging point where the suspected reflection signal is located and the fault position of the signal in the same type; A5, for any suspected reflection signal of each type of signal, the energy amplitudes of all frequency band signals are sorted according to their corresponding propagation path lengths, and the attenuation slope of any suspected reflection signal in any frequency range is calculated by the energy amplitude in different frequency ranges and the rate of change of the propagation path length, and some types of signals are screened out from the suspected reflection signal using the attenuation slope; The traveling wave positioning module is used to determine the traveling wave fault location result of the cable through the standard deviation of the attenuation slope of each suspected reflection signal among all types of signals remaining after screening.

10. A power cable traveling wave ranging device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the power cable traveling wave ranging method as described in any one of claims 1 to 8 are implemented.

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