CN116520096A - Traveling wave fault positioning method and device based on LMD decomposition - Google Patents

Traveling wave fault positioning method and device based on LMD decomposition Download PDF

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Publication number
CN116520096A
CN116520096A CN202310806102.1A CN202310806102A CN116520096A CN 116520096 A CN116520096 A CN 116520096A CN 202310806102 A CN202310806102 A CN 202310806102A CN 116520096 A CN116520096 A CN 116520096A
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traveling wave
point
fault
module
signal
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单鸣雷
汤祺
眭珊珊
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Changzhou Changchuangli Intelligent Technology Co ltd
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Changzhou Changchuangli Intelligent Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Locating Faults (AREA)

Abstract

The invention provides a traveling wave fault positioning method and device based on LMD decomposition, wherein the method comprises the following steps: collecting traveling wave signals generated when the cable fails at two ends of the cable failure point; carrying out LMD decomposition on the acquired traveling wave signals respectively, and determining the initial moment of the traveling wave signals reaching a measuring end through the instantaneous frequency mutation points; and calculating the distance from the fault point to the measuring end by using the time of the traveling wave signal reaching the measuring point. The device comprises an FPGA module and current transformer modules respectively arranged at measuring ends at two ends of the cable. In the positioning method, the problem of end point effect and modal aliasing existing in the EMD decomposition method is avoided by LMD decomposition, and the arrival time of the traveling wave can be accurately known; on the positioning device, the invention is realized based on an FPGA device, has the advantages of high speed, parallelism and integration, can rapidly process a large amount of data, is flexible and programmable, and has great significance for improving the fault location precision.

Description

Traveling wave fault positioning method and device based on LMD decomposition
Technical Field
The invention belongs to the technical field of power cable fault detection, and particularly relates to a traveling wave fault positioning method and device based on LMD decomposition.
Background
The electric power is basic resource of the relationship national life, and after the power cable fails, if the failure point cannot be rapidly positioned and the failure can be removed in time, the operation safety of the system is seriously affected. When a line breaks down, a fault point can generate voltage and current transient traveling waves which are transmitted to two ends of the fault point, the transient traveling waves can generate reflection and transmission phenomena when encountering discontinuous impedance in the transmission process, and the traveling wave method is to calculate the fault distance by using the writing equations of different moments when the same traveling wave reaches a detection point.
The traveling wave ranging is mainly divided into single-ended traveling wave ranging and double-ended traveling wave ranging. Under many line structures and fault conditions, single-ended ranging cannot be performed, and the single-ended ranging also has the problem of ranging dead zones. The double-end traveling wave ranging method has the advantages of simple principle, high ranging precision, wide application range, higher reliability, no interference of opposite-end reflected waves, no reflection of end points and refraction influence of fault points, smaller energy loss, larger traveling wave amplitude and easy detection, and the detected transient traveling waves reach for the first time. When analyzing fault traveling wave, the common empirical mode decomposition (Empirical Mode Decomposition, EMD) method cannot accurately know the arrival time of the traveling wave head due to the problems of end-point effect and mode aliasing, so that fault positioning deviation is caused.
Disclosure of Invention
In order to solve the problems of the traveling wave fault positioning method based on EMD and further improve the positioning accuracy of traveling wave faults, the invention provides a traveling wave fault positioning method and device based on a local mean decomposition method (Local Mean Decomposition, LMD), and the specific technical scheme is as follows:
a traveling wave fault positioning method based on LMD decomposition comprises the following steps:
s1, collecting traveling wave signals generated when a cable fails at two ends of a cable failure point;
s2, carrying out LMD decomposition on the acquired traveling wave signals respectively, and determining the initial moment when the traveling wave signals reach a measuring end through the instantaneous frequency mutation points;
s3, calculating the distance from the fault point to the measuring end by using the time of the traveling wave signal reaching the measuring point.
Further, in step S1, a current traveling wave analog signal is collected through an electronic current transformer based on a Rogowski coil, and the collected analog signal is converted into a digital signal through a high-speed AD chip, so as to obtain a current traveling wave signal.
Further, in step S2, the LMD decomposition includes the steps of:
s201, obtaining original traveling wave signalsExtreme point +.>And calculates the local mean +.>And envelope estimate +.>；
S202, local mean value is to be calculatedAnd travelling wave signal->Smoothing the broken line connection line of the end point by adopting a sliding average method to obtain a local mean function +.>；
S203, estimating the envelope valueAnd travelling wave signal->Smoothing the broken line of the end points by adopting a sliding average method to obtain an envelope estimation function +.>；
S204, local mean functionFrom the original travelling wave signal->Separating to obtain->And uses the envelope estimation function +.>For->Demodulating to obtain->；
S205, willRepeating the above steps as original traveling wave signal to obtain +.>Corresponding envelope estimation functionJudging->Whether or not to meet->And->If not, repeating the steps S201-S204 until the condition is satisfied, namely +.>And->At this time, there are:
s206, calculating an instantaneous amplitude functionFirst PF componentPF 1 Instantaneous phase->And instantaneous frequency->：
S207, the first PF componentPF 1 From the slaveIs separated from the above to obtain new signal->Will->As a new original signal, the above steps S201 to S206 are repeated, and the loop is repeated k times until +.>As a monotonic function, there are:
traveling wave signalIs decomposed into the sum of k PF components and a single frequency signal:
s208, taking the moment corresponding to the abrupt change point of the instantaneous frequency as the initial moment when the traveling wave signal reaches the measuring point.
Further, in step S201,，/>。
further, LMD decomposition is implemented on the FPGA, including extreme point computation and envelope estimation function computation: firstly, storing a received original signal to be processed into a RAM through an FPGA; and then reading values in the original signal sequence, respectively putting the values into a register ABC, judging a maximum value and a minimum value through a numerical comparison module, and then entering an envelope estimation function calculation module.
Further, in step S3, according to the double-end method, the distance from the fault point to the measuring end is calculated by using the time of the traveling wave signal reaching the measuring end: assume the line length isSThe fault point is F point, the measuring ends at two sides of F point are M end and N end respectively, the time when the traveling wave signal generated at F point reaches M end and N end is respectivelyAnd->And->The following steps are:
from this, the distance from the F point to the M end is found:
in the method, in the process of the invention,indicating wave speed, +.>And->The distances from the F point to the M end and the N end are respectively.
Further, wave velocity，L、CThe inductance value and the capacitance value of the cable per unit length are respectively.
The traveling wave fault positioning device based on LMD decomposition comprises an FPGA module and a mutual inductor module which is respectively arranged at measuring ends at two ends of a cable;
the mutual inductor module comprises a mutual inductor, an AD conversion module and a communication module which are sequentially connected, wherein the mutual inductor is used for collecting travelling wave analog signals, the AD conversion module is used for converting the collected travelling wave analog signals into digital signals to obtain travelling wave signals, and the communication module is in communication connection with the communication module in the FPGA module and is used for transmitting the travelling wave signals to the FPGA module;
the FPGA module further comprises an LMD decomposition module, a wave head detection module and a fault distance calculation module which are connected in sequence, wherein the LMD decomposition module is used for executing an LMD decomposition step in the positioning method on the received traveling wave signal, the wave head detection module is used for determining the initial moment that the traveling wave signal reaches the measuring end through the instantaneous frequency mutation point according to the LMD decomposition result, and the fault distance calculation module is used for executing a distance calculation step in the positioning method and obtaining the distance from the fault point to the measuring end.
Preferably, the transformer adopts an electronic current transformer based on a Rogowski coil, and the AD conversion module adopts a high-speed AD conversion chip.
The invention has the beneficial effects that: according to the traveling wave fault positioning method based on LMD decomposition, more frequencies and envelope information can be extracted from PF components obtained through LMD decomposition than IMF components obtained through EMD decomposition, the LMD decomposition avoids the phenomenon of unexplained negative frequency generated when instantaneous frequency is calculated due to the problem of Hilbert transformation, meanwhile, the adopted double-end traveling wave ranging method has higher reliability, the detected transient traveling wave arrives for the first time, interference of opposite-end reflected waves is not needed, the influence of reflection of end points and refraction of fault points is avoided, energy loss is small, traveling wave amplitude is large, and detection is easy. The traveling wave fault positioning device provided by the invention is realized based on an FPGA device, has the advantages of high speed, parallelism and integration, can rapidly process a large amount of data, is flexible and programmable, and has great significance in improving fault location precision.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 is a flow chart of a positioning method according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a positioning device module according to an embodiment of the invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The LMD essentially adaptively separates a nonlinear non-stationary signal step by step according to the envelope characteristic of the signal in order of decreasing frequency to obtain the sum of the envelope function products of a plurality of instantaneous frequencies and a pure frequency modulation function, and the instantaneous frequency mutation point is the moment when the traveling wave head reaches the measuring end. As shown in fig. 1, the traveling wave fault positioning method based on LMD decomposition provided by the invention mainly comprises the following steps:
s1, acquisition of traveling wave signals
When a fault occurs at a certain point on the cable, voltage and current traveling wave signals are transmitted to two ends of the line at the same time, the energy contained in the current traveling wave signals is higher than that of the voltage traveling wave signals, the wave speed is stable, various fault types can be generated, and therefore the current traveling wave signals are selected as detection signals for fault location, and the voltage traveling wave signals can be used as a suboptimal choice. If the current traveling wave signal is selected as the detection signal, the current traveling wave signal in fault is acquired through an electronic current transformer based on the Rogowski coil, and meanwhile, a high-speed AD chip (such as THS 1206) is started to perform parallel analog-digital conversion on the acquired data. If the voltage traveling wave signal is selected, the detection signal is acquired through a voltage transformer.
S2, processing travelling wave signals
And carrying out LMD decomposition on the acquired current traveling wave signals to obtain the instantaneous frequency of each product function component (PF component), and determining the moment when the fault initial wave reaches the measuring point through the instantaneous frequency mutation point. The specific steps of LMD decomposition are as follows:
s201, finding out the traveling wave signalExtreme point +.>And calculates the local mean +.>And envelope estimate +.>The calculation formula is as follows:
（1）
（2）
for local mean valueAnd envelope estimate +.>Smoothing by using a moving average method to obtain a local mean functionAnd an envelope estimation function->。
S202, local mean functionFrom the original signal->Separating to obtain->And according to formulas (3) and (4) for +.>Demodulation is performed.
（3）
（4）
Will beRepeating the above steps as original current traveling wave signal to obtain +.>Corresponding envelope estimation functionJudging->Whether or not to meet->And->If not, repeating the above steps until the condition is satisfied, namely +.>And->At this time, there are:
（5）
（6）
s203, calculating instantaneous amplitude function (envelope signal)First PF component of original signal PF 1 And instantaneous phase +.>And instantaneous frequency->。
（7）
（8）
（9）
（10）
S204, the first PF is set 1 Component slavesIs separated to obtain a new signal +.>Will->As a new original signal, the above steps S201 to S203 are repeated, and the loop is repeated k times until +.>As a monotonic function.
（11）
S205, the final original signal is decomposed into the sum of k PF components and a single frequency signal.
（12）
According to the steps, LMD decomposition is realized on the FPGA, and the LMD decomposition comprises two core steps of extreme point calculation and upper and lower envelope line sequence calculation. Firstly, a received original signal sequence to be processed is put into a RAM through an FPGA, then values in the original signal sequence are read, the values are respectively put into a register ABC, the maximum and minimum values are judged through a numerical comparison module, and then the values enter an upper envelope calculation module and a lower envelope calculation module.
And carrying out LMD function condition verification on the function sequence obtained through calculation. (1) JudgingThe method comprises the steps of carrying out a first treatment on the surface of the (2) Judging the envelope estimation function->Whether or not to meet->. According to the verification result, if the generated sequence meets the LMD condition, inputting the generated sequence to the next stage for later signal processing; otherwise, subtracting the corresponding value from the original function sequence, and repeating the previous operation.
S3, positioning and ranging fault points
According to the double-end method, the distance from the fault point to the measuring end is calculated by utilizing the time of the current traveling wave signal reaching the measuring end: assuming that the fault point is an F point, the measuring ends at two sides of the F point are an M end and an N end respectively, the line length is S (the distance from the M end to the N end), and the moments when the traveling wave signals generated at the F point reach the M end and the N end are respectivelyt M Andt N and (2) andthe following steps are:
（13）
from this, the distance from the F point to the M end is found:
（14）
the line mode component is relatively stable when the influence of frequency is not considered, and the wave speed can be obtained by approximate calculation of line parameters. The line is not damaged, and the parameter frequency correlation is not considered, the wave speed calculation formula is shown as formula (15), wherein L, C is the inductance and the capacitance of the line in unit length respectively.
（15）
As shown in fig. 2, corresponding to the method, the invention also provides a traveling wave fault positioning device based on LMD decomposition, which comprises an FPGA module and transformer modules respectively arranged at measuring ends at two ends of a cable. Wherein:
if the current traveling wave signal is selected as the detection signal, the transformer module comprises an electronic current transformer based on a Rogowski coil, an AD conversion module and a communication module which are sequentially connected. The current transformer is used for collecting current traveling wave analog signals, the AD conversion module is used for converting the collected current traveling wave analog signals into digital signals to obtain the current traveling wave signals, and a high-speed AD conversion chip can be used for carrying out rapid parallel analog-digital conversion. If the voltage traveling wave signal is selected as the detection signal, the current transformer in the transformer module is replaced by a voltage transformer. The communication module is in communication connection with the communication module in the FPGA module and is used for transmitting the current traveling wave signals to the FPGA module.
The FPGA module further comprises an LMD decomposition module, a wave head detection module and a fault distance calculation module which are connected in sequence, wherein the LMD decomposition module is used for executing an LMD decomposition step in the positioning method on the received traveling wave signal, the wave head detection module is used for determining the initial moment that the current traveling wave signal reaches the measuring end through the instantaneous frequency abrupt change point, and the fault distance calculation module is used for executing a distance calculation step in the positioning method and obtaining the distance from the fault point to the measuring end.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the invention, the steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims (8)

1. The traveling wave fault positioning method based on LMD decomposition is characterized by comprising the following steps:
s1, collecting traveling wave signals generated when a cable fails at two ends of a cable failure point;
s2, carrying out LMD decomposition on the acquired traveling wave signals respectively, and determining the initial moment when the traveling wave signals reach a measuring end through the instantaneous frequency mutation points; the LMD decomposition includes the steps of:
s201, obtaining original traveling wave signalsExtreme point +.>And calculates the local mean +.>And envelope estimate +.>；
S202, local mean value is to be calculatedAnd travelling wave signal->Smoothing the broken line connection line of the end point by adopting a sliding average method to obtain a local mean function +.>；
S203, estimating the envelope valueAnd travelling wave signalNumber->Smoothing the broken line of the end points by adopting a sliding average method to obtain an envelope estimation function +.>；
S204, local mean functionFrom the original travelling wave signal->Separating to obtain->And uses the envelope estimation function +.>For->Demodulating to obtain->；
S205, willRepeating the above steps as original traveling wave signal to obtain +.>Corresponding envelope estimation function->Judging->Whether or not to meet->And->If not, repeating the steps S201-S204 until the condition is satisfied, namely +.>And->At this time, there are:
s206, calculating an instantaneous amplitude functionFirst PF componentPF 1 Instantaneous phase->And instantaneous frequency->：
S207, the first PF componentPF 1 From the slaveIs separated from the above to obtain new signal->Will->As a new original signal, the above steps S201 to S206 are repeated, and the loop is repeated k times until +.>As a monotonic function, there are:
traveling wave signalIs decomposed into the sum of k PF components and a single frequency signal:
s208, taking the moment corresponding to the abrupt change point of the instantaneous frequency as the initial moment when the traveling wave signal reaches the measuring point;
s3, calculating the distance from the fault point to the measuring end by using the time of the traveling wave signal reaching the measuring point.
2. The method for locating a traveling wave fault based on LMD decomposition according to claim 1, wherein in step S1, a current traveling wave analog signal is collected by an electronic current transformer based on Rogowski coil, and the collected analog signal is converted into a digital signal by a high-speed AD chip, so as to obtain the current traveling wave signal.
3. A traveling wave fault location method based on LMD decomposition according to claim 1, wherein in step S201,，/>。
4. the traveling wave fault location method based on LMD decomposition according to claim 1, wherein the LMD decomposition is implemented on an FPGA, including extreme point calculation and envelope estimation function calculation: firstly, storing a received original signal to be processed into a RAM through an FPGA; and then reading values in the original signal sequence, respectively putting the values into a register ABC, judging a maximum value and a minimum value through a numerical comparison module, and then entering an envelope estimation function calculation module.
5. The method for locating a traveling wave fault based on LMD decomposition according to claim 1, wherein in step S3, a distance from a fault point to a measurement end is calculated according to a double-ended method by using a time of arrival of a traveling wave signal at the measurement end: assume the line length isSThe fault point is F point, the measuring ends at two sides of F point are M end and N end respectively, the time when the traveling wave signal generated at F point reaches M end and N end is respectivelyAnd->And->The following steps are:
from this, the distance from the F point to the M end is found:
in the method, in the process of the invention,indicating wave speed, +.>And->The distances from the F point to the M end and the N end are respectively.
6. The method for locating a traveling wave fault based on LMD decomposition of claim 5, wherein the wave velocity is，L、CThe inductance value and the capacitance value of the cable per unit length are respectively.
7. The traveling wave fault positioning device based on LMD decomposition is characterized by comprising an FPGA module and mutual inductor modules respectively arranged at measuring ends at two ends of a cable;
the mutual inductor module comprises a mutual inductor, an AD conversion module and a communication module which are sequentially connected, wherein the mutual inductor is used for collecting travelling wave analog signals, the AD conversion module is used for converting the collected travelling wave analog signals into digital signals to obtain travelling wave signals, and the communication module is in communication connection with the communication module in the FPGA module and is used for transmitting the travelling wave signals to the FPGA module;
the FPGA module further comprises an LMD decomposition module, a wave head detection module and a fault distance calculation module which are connected in sequence, wherein the LMD decomposition module is used for executing an LMD decomposition step in the positioning method according to claim 1 or 3 on the received traveling wave signal, the wave head detection module is used for determining the initial moment that the traveling wave signal reaches the measuring end through the instantaneous frequency abrupt change point according to the LMD decomposition result, and the fault distance calculation module is used for executing a distance calculation step in the positioning method according to claim 5 or 6 and obtaining the distance from the fault point to the measuring end.
8. The LMD decomposition based traveling wave fault locating device of claim 7 wherein said transformer is a Rogowski coil based electronic current transformer and said AD conversion module is a high speed AD conversion chip.
CN202310806102.1A 2023-07-04 2023-07-04 Traveling wave fault positioning method and device based on LMD decomposition Pending CN116520096A (en)

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Application publication date: 20230801