CN117368645A - Power distribution network cable fault point distance measuring method, system, computer equipment and medium - Google Patents
Power distribution network cable fault point distance measuring method, system, computer equipment and medium Download PDFInfo
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Abstract
The invention belongs to the technical field of power distribution networks, and discloses a power distribution network cable fault point distance measuring method, a system, computer equipment and a medium, wherein a transient signal of a wide-area frequency band is generated when a cable is in fault, fault traveling waves contain high-frequency components, and traveling wave line mode components with smaller chromatic dispersion are adopted for detection; decoupling the extracted fault traveling wave signals; when the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current are sharply changed, the traveling wave head can show high-frequency mutation in the time-frequency diagram, and the mutation point is the wave head position; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and then the sampling time corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival time of the fault traveling wave head; and calculating the fault point distance by adopting a double-end ranging algorithm. The distance measurement result has higher precision, and the relative error is not more than 4% compared with the actual fault position.
Description
Technical Field
The invention belongs to the technical field of power distribution networks, and particularly relates to a power distribution network cable fault point distance measuring method, a power distribution network cable fault point distance measuring system, computer equipment and a medium.
Background
At present, with the development of power distribution networks and the promotion of urban construction, power cables gradually replace overhead lines to be thrown and transported in urban power distribution network systems in large quantities. Because the cable is generally laid in an underground cable trench, fault points cannot be found through visual observation after faults, and fault troubleshooting and fault point positioning are difficult, so that the power supply reliability and operation safety of the system are affected. The traditional power cable fault distance measurement is mainly performed by offline measurement, and the biggest problem of the offline method is that part of faults are difficult to reproduce under high-voltage impact, so that distance measurement failure is caused; in addition, multiple injections of high voltage pulses can affect the life of the entire cable. The current cable fault location method applied to reality mainly realizes fault location by stopping a fault cable and then adopting a pulse injection method. The method has poor instantaneity, does not meet the intelligent operation requirement of the power grid line, and is unfavorable for the construction of the intelligent power grid. The traveling wave method is a ranging method based on traveling wave transmission theory, which utilizes the refraction and reflection phenomenon of traveling wave when traveling wave propagates in a line to perform ranging, and adopts the fault traveling wave method to perform cable fault ranging, so that real-time performance can be realized theoretically, and the fault traveling wave generated by a fault point is utilized to perform ranging without adding an additional signal generating device, thereby being convenient and quick. Therefore, the on-line fault traveling wave ranging has the incomparable advantage of off-line fault traveling wave ranging, and is the focus and direction of cable fault ranging research.
The traveling wave method is a ranging method based on the traveling wave transmission theory, and uses the refraction and reflection phenomenon when traveling waves propagate in a line to perform ranging. The accurate calibration of the moment when the traveling wave head reaches the measuring end and the determination of the traveling wave speed are the key of traveling wave ranging, and the current research mainly adopts a wavelet analysis method to extract the fault traveling wave head. However, the wavelet analysis result is affected by factors such as the type of wavelet base, sampling rate and decomposition scale, etc., and the wavelet transformation theoretically has infinite variety of wavelet bases, if the characteristics of the wavelet transformation cannot be analyzed in detail and proper wavelet base functions are selected by combining the characteristics of the travelling wave signals, satisfactory results are difficult to obtain. The empirical mode decomposition (Empirical Mode Decomposition, EMD) method is an adaptive decomposition algorithm capable of effectively analyzing and processing the nonstationary signals, and can effectively separate each frequency component of the nonstationary signals. However, EMD has a problem of modal aliasing, i.e. one Intrinsic Mode Function (IMF) component contains very different characteristic time scales, or similar characteristic time scales are distributed in different IMF components. Therefore, the fault traveling wave head signal identification precision is not high, and the fault point distance measurement error is larger.
Through the above analysis, the problems and defects existing in the prior art are as follows: in the prior art, a traditional empirical mode decomposition algorithm is adopted to easily generate mode aliasing and influence the calibration of the arrival time of a fault traveling wave head, so that the accuracy of algorithm fault ranging is low and the error is larger.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a power distribution network cable fault point distance measuring method, a system, computer equipment and a medium.
The invention discloses a power distribution network cable fault point distance measuring method, which comprises the following steps:
firstly, generating a transient signal of a wide-area frequency band when a cable fails, wherein a fault traveling wave contains a high-frequency component, and detecting by adopting a traveling wave line mode component with smaller chromatic dispersion; decoupling the extracted fault traveling wave signals;
secondly, when the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and the traveling wave current are subjected to sharp change, the traveling wave head can show high-frequency mutation in a time-frequency diagram, and the mutation point is the position of the wave head; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and then the sampling time corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival time of the fault traveling wave head;
and thirdly, calculating the fault point distance by adopting a double-end ranging algorithm.
Further, the first step specifically includes: and decoupling the extracted fault traveling wave signals, and realizing by adopting the Karenbeol transformation.
The decoupling process is as follows:
in which I a (n)、I b (n)、I c (n) are line three-phase currents, respectively; i 0 (n)、I α (n)、I β (n) the decoupled 0-mode current, alpha-mode current and beta-mode current components, respectively; the alpha mode and the beta mode are both called line mode components, and a wave velocity equation of the traveling wave under different moduli is obtained:
wherein L is 0 、C 0 And L 1 、C 1 The zero mode and the line mode parameters of the cable line are respectively.
Further, the second step specifically includes: identifying a fault traveling wave head, superposing Gaussian white noise on an original signal by adopting an EEMD algorithm, performing EMD (electromagnetic interference cancellation) for a plurality of times, and taking the average value of IMF (intrinsic mode function) components as a final result;
1) Adding a white noise to the signal x (t) being analyzed;
2) Performing EMD (empirical mode decomposition) to decompose the signals after noise addition to obtain each IMF;
3) Repeating steps 1) and 2) but each time the white noise applied is different;
4) Taking the average value of each IMF component obtained by multiple decomposition as a final result.
Further, the second step specifically includes: the calibration of the fault traveling wave head adopts a Hilbert transformation algorithm:
let X (t) be a time sequence and Y (t) be its Hilbert transform, namely:
the inverse transformation is as follows:
obtaining an analytic signal:
Z(t)＝X(t)+iY(t)＝A(t)e iθ(t) ；
wherein: a (t) is the instantaneous amplitude value,
θ (t) is the phase of the phase,the instantaneous frequency is defined as:
i.e. the derivative of the phase of the resolved signal Z (t).
Further, in the second step, EEMD is performed on the collected fault traveling wave signals to obtain a series of natural mode components only containing one vibration mode, and Hilbert transformation is performed on the first IMF component to obtain the instantaneous frequency of the IMF component, wherein the abrupt point of the instantaneous frequency is the wave head of the collected fault traveling wave.
Further, the third step specifically includes: f is a fault point in the double-end ranging algorithm, t1 and t2 are time for fault traveling waves to reach an M end and an N end respectively, L is the total length of a cable, v is the traveling wave speed, and a cable fault positioning equation is deduced:
it is a further object of the present invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the distribution network cable fault point ranging method.
It is a further object of the present invention to provide a computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the power distribution network cable fault point ranging method.
The invention further aims to provide an information data processing terminal which is used for realizing the power distribution network cable fault point distance measuring method.
Another object of the present invention is to provide a power distribution network cable fault point ranging system based on the power distribution network cable fault point ranging method, where the power distribution network cable fault point ranging system includes:
the traveling wave line mode component extraction module is used for extracting fault traveling wave signals from wide-area frequency band transient signals generated when the cable fails, wherein the fault traveling wave contains high-frequency components, and the traveling wave line mode components with smaller chromatic dispersion are adopted for detection; decoupling the extracted fault traveling wave signals;
the fault traveling wave head identification and calibration module is used for detecting the arrival time of the fault traveling wave head. When the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current are sharply changed, the traveling wave head can show high-frequency mutation in the time-frequency diagram, and the mutation point is the wave head position; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and the position of a first frequency mutation point on the time-frequency diagram is the arrival time of a fault traveling wave head;
and the fault point distance calculation module is used for calculating the distance of the fault point in the cable by adopting a double-end ranging algorithm.
In combination with the technical scheme and the technical problems to be solved, the technical scheme to be protected has the following advantages and positive effects:
the cable fault distance measurement method based on the EEMD algorithm is simple and feasible, is basically not influenced by fault resistance, can effectively measure the faults at different positions of the cable, has higher accuracy of a distance measurement result, and has the maximum relative error of not more than 4% compared with the actual fault position.
Secondly, the invention provides an online fault location method for the double-end traveling wave of the distribution network cable based on Ensemble Empirical Mode Decomposition (EEMD), which mainly solves the problems that the conventional empirical mode decomposition algorithm is easy to generate modal aliasing, and accurate identification and calibration of the arrival time of a fault traveling wave head are affected, so that the algorithm fault location accuracy is low and the error is large, and the accurate calibration of the fault traveling wave signal head is realized, and compared with the conventional algorithm, the fault location accuracy is higher and the positioning is more accurate.
Thirdly, the expected benefits and commercial value after the technical scheme of the invention is converted are as follows: with the development of urban processes, the proportion of cables in power distribution networks, especially in urban power distribution networks, is higher and higher, and the problems of cable line fault detection and positioning are also serious. The invention provides a double-end fault location method and a double-end fault location system suitable for a power distribution network cable line, which can be used for directly developing related equipment based on the invention, or can be used for improving the existing fault location equipment by utilizing the technical scheme of the invention, so that the on-site fault location precision can be greatly improved, and the power supply reliability of the system is ensured. The technical scheme is easy to convert, has rich application scenes and large demand, and has wide application space and huge commercial value.
Fourth, based on the distribution network cable fault point distance measurement method provided by the invention, the following is a remarkable technical progress:
1) High accuracy:
by adopting EEMD decomposition and Hilbert transformation technology, the method can more accurately detect the arrival time of the traveling wave head, thereby improving the accuracy of ranging.
2) Fast response:
because the method mainly focuses on high-frequency components, the method can rapidly identify traveling waves generated by fault points, and greatly shortens the time for fault location.
3) And (3) misjudgment is reduced:
by decoupling the fault traveling wave signal and analyzing the high-frequency component, the method can greatly reduce misjudgment caused by external noise or other non-fault factors.
4) Wide area monitoring:
the method has higher sensitivity to transient signals of a wide-area frequency band, so that high-accuracy fault location can be realized for long-distance power distribution network cables.
5) The adaptability is strong:
because the traveling wave line mode component with smaller dispersion is adopted for detection, the method has good adaptability to cables of different types, materials and lengths.
6) And (3) technical integration:
the method allows the combination with other technologies (such as optical fiber temperature measurement technology or digital traveling wave relay technology) to further improve the accuracy and reliability of fault detection and location.
7) The power grid downtime is reduced:
accurate and rapid location to the fault point means that maintenance can be performed faster, thereby reducing downtime of the grid and improving the power supply reliability of the power system.
8) Economic benefit:
by reducing false positives, reducing downtime, and quickly locating faults, the method may save a significant amount of operating and maintenance costs for the power provider.
The power distribution network cable fault point distance measuring method provided by the invention has obvious technical progress, and provides a high-efficiency, accurate and reliable fault positioning tool for a modern power system.
Drawings
Fig. 1 is a flowchart of a power distribution network cable fault point distance measurement method provided by an embodiment of the invention;
FIG. 2 is a flowchart of an EMD decomposition algorithm provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of a double-ended traveling wave ranging scheme provided by an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a distribution network cable fault point ranging system according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a collected fault current waveform provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of an extracted double-ended fault line mode component provided by an embodiment of the present invention;
fig. 7 is a schematic diagram of a head-end sampling point according to an embodiment of the present invention;
fig. 8 is a schematic diagram of an end sampling point according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Based on the distribution network cable fault point distance measurement method provided by the invention, the following two specific embodiments and implementation schemes thereof are as follows:
example 1: implementation scheme based on digital traveling wave relay
1) System configuration:
and configuring digital traveling wave relays at two ends of the cable.
And a high-speed sampling ADC (analog-to-digital converter) is arranged at each traveling wave relay end for signal acquisition.
2) The implementation steps are as follows:
s101: when the cable breaks down, the traveling wave relay immediately starts to collect the high-frequency change signal. The collected signals are filtered by a band-pass filter to remove non-high frequency components, and then decoupling treatment is carried out.
S102: the high frequency signal is decomposed by an EEMD method from which a first IMF component is extracted. Thereafter, a time-frequency diagram is generated using a Hilbert transform. The time corresponding to the first frequency mutation point detected on the time-frequency diagram is the arrival time of the traveling wave head.
S103: and calculating the position of the fault point based on the arrival time of the traveling wave recorded by the traveling wave relays at the two ends by using a double-end ranging algorithm.
Example 2: implementation scheme based on optical fiber temperature measurement technology
1) System configuration:
a distributed fiber optic temperature measurement system (DTS) is deployed along the cable.
The fiber optic sensor is used to capture temperature changes and other related physical parameter changes caused by cable faults.
2) The implementation steps are as follows:
s101: when a cable fault occurs, the fiber optic sensor captures high frequency temperature and other physical parameter changes. The fault traveling wave signal is extracted from these changes and decoupled using a specific algorithm.
S102: the captured signal is decomposed using the EEMD method, from which the first IMF component is extracted. Thereafter, a time-frequency diagram is generated using a Hilbert transform. The time corresponding to the first frequency mutation point detected on the time-frequency diagram is the arrival time of the traveling wave head.
S103: because the DTS system can accurately measure the position of temperature change, the measured time and the known cable length and traveling wave propagation speed can be directly utilized to calculate the position of the fault point.
Both embodiments provide an effective method for distribution network cable fault point ranging, but the specific choice of which embodiment depends on the actual application scenario, budget and technical requirements.
As shown in fig. 1, the power distribution network cable fault point distance measurement method provided by the embodiment of the invention includes the following steps:
s101: generating a transient signal of a wide-area frequency band when the cable fails, wherein a fault traveling wave contains a high-frequency component, and detecting by adopting a traveling wave line mode component with smaller chromatic dispersion; decoupling the extracted fault traveling wave signals;
s102: when the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current are sharply changed, the traveling wave head can show high-frequency mutation in the time-frequency diagram, and the mutation point is the wave head position; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and the adopted moment corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival moment of the fault traveling wave head;
s103: and calculating the fault point distance by adopting a double-end ranging algorithm.
The power distribution network cable fault point distance measurement method provided by the embodiment of the invention comprises the following steps:
(1) Extraction of line mode components of traveling wave
When the cable fails, a transient signal of a wide area frequency band is generated, and fault traveling waves contain abundant high-frequency components; the traveling wave signals with different moduli and frequencies have different propagation speeds, so that the traveling wave head is distorted in the propagation process, and the accurate calibration of the wave head is affected. The invention adopts the line mode component of the line wave with smaller chromatic dispersion for detection.
The cable three phases have complex electromagnetic coupling relation, so that the fault traveling wave head is distorted in the propagation process, and the ranging accuracy is reduced. Therefore, the extracted fault traveling wave signals are required to be decoupled, and the invention is realized by adopting the Karenbeol transformation.
The decoupling process is as follows:
in which I a (n)、I b (n)、I c (n) are line three-phase currents, respectively; i 0 (n)、I α (n)、I β (n) are the decoupled 0-mode current, alpha-mode current and beta-mode current components, respectively. Where both the alpha and beta modes are referred to as line mode components. The wave velocity equation of the traveling wave at different moduli can be further obtained:
wherein L is 0 、C 0 And L 1 、C 1 The zero mode and the line mode parameters of the cable line are respectively.
(2) Identification and calibration of fault traveling wave head
Wave head identification: when the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current will change sharply, the traveling wave head will show high frequency mutation in the time-frequency diagram, and the mutation point is the wave head position.
Wave head calibration: EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, the first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and the adopted time corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival time of the fault traveling wave head.
EEMD algorithm flow:
the essence of EEMD algorithm is to superimpose Gaussian white noise on the original signal, perform EMD decomposition for many times, and take the mean value of IMF components as the final result.
1) Adding a white noise to the signal x (t) being analyzed;
2) Performing EMD (empirical mode decomposition) to decompose the signals after noise addition to obtain each IMF;
3) Repeating steps 1) and 2) but each time the white noise applied is different;
4) Taking the average value of each IMF component obtained by multiple decomposition as a final result.
As shown in fig. 2, two important parameters of the EEMD algorithm: collective number N and magnitude of the added gaussian white noise. The invention adopts the following steps: in most cases when n=100, the standard deviation of the amplitude of the noise is 0.2 times the standard deviation of the signal.
Hilbert transform algorithm:
let X (t) be a time sequence and Y (t) be its Hilbert transform, namely:
the inverse transformation is as follows:
obtaining an analytic signal:
Z(t)＝X(t)+iY(t)＝A(t)e iθ(t) (6)
wherein: a (t) is the instantaneous amplitude value,
θ (t) is the phase of the phase,the instantaneous frequency can be defined as:
i.e. the derivative of the phase of the resolved signal Z (t).
EEMD (ensemble empirical mode decomposition) is carried out on the acquired fault traveling wave signals to obtain a series of natural mode components only containing one vibration mode, hilbert transformation is carried out on the first IMF component to obtain the instantaneous frequency of the IMF component, and the position corresponding to the abrupt change point of the instantaneous frequency is the wave head of the acquired fault traveling wave.
(3) Fault point distance calculating method
The double-end ranging algorithm has the advantages of simple principle and high positioning accuracy. The specific algorithm is shown in fig. 4;
wherein F is a fault point, t1 and t2 are time for fault traveling wave to reach M end and N end respectively, L is total length of cable, and v is traveling wave speed. From this, the cable fault location equation can be deduced:
as shown in fig. 4, the power distribution network cable fault point ranging system provided by the embodiment of the invention includes:
the traveling wave line mode component extraction module is used for extracting fault traveling wave signals from wide-area frequency band transient signals generated when the cable fails, wherein the fault traveling wave contains high-frequency components, and the traveling wave line mode components with smaller chromatic dispersion are adopted for detection; decoupling the extracted fault traveling wave signals;
the fault traveling wave head identification and calibration module is used for detecting the arrival time of the fault traveling wave head. When the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current are sharply changed, the traveling wave head can show high-frequency mutation in the time-frequency diagram, and the mutation point is the wave head position; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and the position of a first frequency mutation point on the time-frequency diagram is the arrival time of a fault traveling wave head;
and the fault point distance calculation module is used for calculating the distance of the fault point in the cable by adopting a double-end ranging algorithm.
The embodiment of the invention has a great advantage in the research and development or use process, and has the following description in combination with data, charts and the like of the test process.
Firstly, a 10kV power distribution network model based on a cable is built by PSCAD/EMTDC software, the cable length is set to be 10km, faults are set to occur at a position which is 2km away from the head end of the cable, A phase grounding faults are set, different transition resistances (0.1 omega, 10 omega and 100 omega) are set for simulation analysis, simulation duration is 0.05s, faults occur at 0.02s, and sampling frequency is 1MHz.
The algorithm implementation flow is as follows:
1) Collecting fault current waveforms as shown in figure 5'
2) Extracting line mode components of double-end fault traveling wave
The phase-mode transformation is carried out on the three-phase current sampled from the two ends to obtain the alpha-mode component of the three-phase current, and the alpha-mode component of the current traveling wave with t= 0.0198 s-0.0204 s is extracted for analysis, as shown in fig. 6;
3) EEMD (EEMD) decomposition is respectively carried out on the extracted line mode components of the double-end fault traveling wave and Hilbert transformation is carried out on the first IMF component; as shown in fig. 7 and 8;
the arrival time of the wave head of the fault traveling wave detected at the head end is 211 th sampling point, the arrival time of the wave head detected at the tail end is 241 th sampling point, the distance between the fault point and the head end 2026.1m can be calculated by the formula (8), the distance between the actual fault point and the head section of the cable is 2000m, and the algorithm relative error is 1.305%.
TABLE 1 ranging results at different fault distances and different transition resistances
The cable fault location method based on the EEMD algorithm is simple and feasible, is basically not influenced by fault resistance, can effectively measure the faults at different positions of the cable, has higher accuracy of the location result, and has the maximum relative error of not more than 4% compared with the actual fault position.
It should be noted that the embodiments of the present invention can be realized in hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or special purpose design hardware. Those of ordinary skill in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such as provided on a carrier medium such as a magnetic disk, CD or DVD-ROM, a programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The device of the present invention and its modules may be implemented by hardware circuitry, such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., as well as software executed by various types of processors, or by a combination of the above hardware circuitry and software, such as firmware.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.
Claims (10)
1. The power distribution network cable fault point distance measurement method is characterized by comprising the following steps of:
firstly, generating a transient signal of a wide-area frequency band when a cable fails, wherein a fault traveling wave contains a high-frequency component, and detecting by adopting a traveling wave line mode component with smaller chromatic dispersion; decoupling the extracted fault traveling wave signals;
secondly, when the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and the traveling wave current are subjected to sharp change, the traveling wave head can show high-frequency mutation in a time-frequency diagram, and the mutation point is the position of the wave head; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and then the sampling time corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival time of the fault traveling wave head;
and thirdly, calculating the fault point distance by adopting a double-end ranging algorithm.
2. The power distribution network cable fault point ranging method according to claim 1, wherein the first step specifically comprises: and decoupling the extracted fault traveling wave signals, and realizing by adopting the Karenbeol transformation.
The decoupling process is as follows:
in which I a (n)、I b (n)、I c (n) are line three-phase currents, respectively; i 0 (n)、I α (n)、I β (n) the decoupled 0-mode current, alpha-mode current and beta-mode current components, respectively; the alpha mode and the beta mode are both called line mode components, and a wave velocity equation of the traveling wave under different moduli is obtained:
wherein L is 0 、C 0 And L 1 、C 1 The zero mode and the line mode parameters of the cable line are respectively.
3. The power distribution network cable fault point ranging method according to claim 1, wherein the second step specifically comprises: identifying a fault traveling wave head, superposing Gaussian white noise on an original signal by adopting an EEMD algorithm, performing EMD (electromagnetic interference cancellation) for a plurality of times, and taking the average value of IMF (intrinsic mode function) components as a final result;
1) Adding a white noise to the signal x (t) being analyzed;
2) Performing EMD (empirical mode decomposition) to decompose the signals after noise addition to obtain each IMF;
3) Repeating steps 1) and 2) but each time the white noise applied is different;
4) Taking the average value of each IMF component obtained by multiple decomposition as a final result.
4. The power distribution network cable fault point ranging method according to claim 1, wherein the second step specifically comprises: the calibration of the fault traveling wave head adopts a Hilbert transformation algorithm:
let X (t) be a time sequence and Y (t) be its Hilbert transform, namely:
the inverse transformation is as follows:
obtaining an analytic signal:
Z(t)＝X(t)+iY(t)＝A(t)e iθ(t) ；
wherein: a (t) is the instantaneous amplitude value,
θ (t) is the phase of the phase,the instantaneous frequency is defined as:
i.e. the derivative of the phase of the resolved signal Z (t).
5. The method for measuring the fault point distance of the power distribution network cable according to claim 1, wherein in the second step, a series of natural mode components only including one vibration mode are obtained after EEMD decomposition is performed on the collected fault traveling wave signals, and Hilbert transformation is performed on the first IMF component to obtain the instantaneous frequency of the IMF component, wherein the abrupt change point of the instantaneous frequency is the wave head of the collected fault traveling wave.
6. The power distribution network cable fault point ranging method according to claim 1, wherein the third step specifically comprises: f is a fault point in the double-end ranging algorithm, t1 and t2 are time for fault traveling waves to reach an M end and an N end respectively, L is the total length of a cable, v is the traveling wave speed, and a cable fault positioning equation is deduced:
7. a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the distribution network cable fault point ranging method of any one of claims 1 to 6.
8. A computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the power distribution network cable fault point ranging method of any one of claims 1 to 6.
9. An information data processing terminal, which is characterized in that the information data processing terminal is used for realizing the power distribution network cable fault point distance measuring method according to any one of claims 1 to 6.
10. A distribution network cable fault point ranging system based on the distribution network cable fault point ranging method as claimed in any one of claims 1 to 6, comprising:
the traveling wave line mode component extraction module is used for extracting a fault traveling wave signal from a wide-area frequency band transient signal generated when a cable fails, wherein the fault traveling wave signal contains a high-frequency component and is detected by adopting a traveling wave line mode component with smaller chromatic dispersion; decoupling the extracted fault traveling wave signals;
the fault traveling wave head identification and calibration module is used for detecting the arrival time of the fault traveling wave head. When the traveling wave generated by the fault point reaches the measuring end, the traveling wave voltage and current are sharply changed, the traveling wave head can show high-frequency mutation in the time-frequency diagram, and the mutation point is the wave head position; EEMD (EEMD) decomposition is carried out on the fault traveling wave line mode component, a first IMF component is extracted, hilbert transformation is carried out to obtain a time-frequency diagram of the fault traveling wave line mode component, and then the sampling time corresponding to the position of the first frequency mutation point on the time-frequency diagram is the arrival time of the fault traveling wave head;
the fault point distance calculation module is used for calculating the fault point distance by adopting a double-end ranging algorithm.
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| CN117723893B (en) * | 2024-02-07 | 2024-05-03 | 南方电网数字电网研究院股份有限公司 | RLMD-based fault traveling wave identification method and device and computer equipment |
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