CN114994467B - Cable fault double-end positioning method based on long test pulse - Google Patents
Cable fault double-end positioning method based on long test pulse Download PDFInfo
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- 230000000644 propagated effect Effects 0.000 claims abstract description 4
- 238000005314 correlation function Methods 0.000 claims description 3
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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
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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
- G01R31/088—Aspects of digital computing
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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
- G01R31/11—Locating faults in cables, transmission lines, or networks using pulse reflection methods
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- 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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Abstract
The invention provides a cable fault double-end positioning method based on long test pulse, which comprises the steps of constructing two groups of mutually orthogonal coding pulse strings, respectively distributing the coding pulse strings to the near end and the far end of a fault cable, enabling the fault point of the fault cable to be in an arcing state by adopting a high-voltage flashover method, and arranging traveling wave detection devices and GPS modules at the head end and the tail end of the fault cable; transmitting different coding pulse trains at the near end and the far end of the fault cable simultaneously, and recording a local signal propagated in the fault cable until reaching the end time; predicting a local signal by adopting an encoding pulse string of an opposite terminal, and storing a predicted residual signal; cross-correlating the code pulse trains at the near end and the far end of the fault cable with respective residual signals, and calculating to obtain the time difference between the reflected signals and the transmitted signals; according to the time difference, the position of the fault point of the fault cable is obtained through calculation, the time-wide bandwidth product is effectively improved, the detection dead zones at the two ends of the cable can be eliminated, and the detection accuracy of the cable is improved.
Description
Technical Field
The invention relates to the technical field of cable fault positioning, in particular to a cable fault double-end positioning method based on long test pulses.
Background
The cable in power transmission can have faults after being damaged by external force or aged for a long time, and when the faults occur on the cable, the accurate and rapid finding of the fault occurrence position is particularly important. The most commonly used method at present is a single-ended positioning method, also called a single-ended traveling wave ranging method, the principle of which is as follows: and recording the time of the transient traveling wave reaching the measuring end for the first time and the time of the returning fault point reaching the measuring end after the first reflection by utilizing the characteristic of unchanged traveling wave speed, and calculating the fault position by utilizing a formula.
The existing single-end positioning method has the following two defects:
(1) When the single-end positioning method is adopted, a certain blind area is formed for the fault point which is close to the transmitting end due to short reflection time, the positioning result is influenced, and the reflected signal is very weak for the fault point which is very far away from the transmitting end due to the attenuation characteristic of the traveling wave, so that the positioning precision is also influenced.
(2) When single-end positioning is used, a pulse is injected into the cable, the pulse can generate voltage and current waves close to the speed of light under the action of additional power at a fault point of the cable, but the duration of test pulse transmitted by each test is shorter, the product of the time and the bandwidth cannot reach the optimal value, and the reflected wave is easily interfered by other noise when transmitted in the cable.
Disclosure of Invention
In view of the above, the invention provides a cable fault double-end positioning method based on long test pulses, which can eliminate detection blind areas at two ends of a fault cable and improve the detection accuracy of the cable by transmitting mutually orthogonal coding pulse trains at the two ends of the fault cable.
The technical scheme of the invention is realized as follows:
A cable fault double-end positioning method based on long test pulses comprises the following steps:
S1, constructing two groups of mutually orthogonal coding pulse trains, and respectively distributing the coding pulse trains to the near end and the far end of a fault cable;
S2, adopting a high-voltage flashover method to enable a fault point of a fault cable to be in an arcing state, and arranging a traveling wave detection device and a GPS module at the head end and the tail end of the fault cable;
Step S3, different coding pulse trains are simultaneously sent at the near end and the far end of the fault cable, and a local signal propagated in the fault cable is recorded until reaching the end time;
S4, predicting a local signal by adopting an opposite-end coding pulse string, and storing a predicted residual signal;
s5, performing cross-correlation on the coded pulse trains at the near end and the far end of the fault cable and respective residual signals, and calculating to obtain the time difference between the reflected signals and the transmitted signals;
and S6, calculating to obtain the fault point position of the fault cable according to the time difference.
Preferably, the specific steps of the step S1 are as follows:
Step S11, two groups of mutually orthogonal coding pulses with duration of l and length of k are determined;
Step S12, splicing k coding pulses of each group in the step S11 into a coding pulse string;
Step S13, the code pulse trains are denoted as X 1 and X 2, respectively, and are allocated to the near end and the far end of the faulty cable, respectively.
Preferably, the orthogonality condition satisfied by the coded pulse in step S11 is: for both signals x (x 1,x2,x3,…,xn) and y (y 1,y2,y3,…,yn), if presentThe two signals are considered to be orthogonal signals, where ρ xy is a cross-correlation function.
Preferably, the length of the code pulse train in the step S12 does not exceed L/v, where L is the length of the faulty cable and v is the propagation speed of the electromagnetic wave in the cable.
Preferably, the ending time T end of the step S3 is equal to or more than max (T, 3L/v), wherein T is the duration of the arcing state.
Preferably, the specific steps of the step S4 include:
step S41, a first N-order autocorrelation vector A of a local signal and a first N-order cross correlation vector C of a local signal and an opposite end coding pulse string are obtained, wherein N is the order of an FIR filter;
Step S42, expanding the first N-order autocorrelation vector A into a toeplitz matrix Q of N;
step S43, calculating a unit impulse response h=q -1 C of the FIR filter;
Step S44, filtering the local signal with an FIR filter, and obtaining predicted residual signals Y 1 and Y 2.
Preferably, in the step S5, a calculation formula for cross-correlating the coded pulse trains at the near end and the far end of the faulty cable with respective residual signals is as follows:
Wherein R 1 (τ) is a near-end cross-correlation calculation formula, R 2 (τ) is a far-end cross-correlation calculation formula, X 1 and X 2 are code pulse strings, Y 1 and Y 2 are residual signals, and τ is a time delay.
Preferably, in the step S5, a calculation formula for calculating a time difference between the reflected signal and the transmitted signal is as follows:
Preferably, the calculation formula of step S6 is as follows:
wherein v is the propagation speed of electromagnetic waves in the cable, and t is the time difference between the reflected signal and the transmitted signal calculated in step S5.
Compared with the prior art, the invention has the beneficial effects that:
The invention provides a cable fault double-end positioning method based on long test pulses, which is characterized in that orthogonal coded pulse strings are simultaneously transmitted at two ends of a fault cable, and the influence of opposite-end projection waves is eliminated by adopting self-adaptive cancellation, so that the time-width bandwidth product is effectively improved, the detection blind areas at two ends of the fault cable can be eliminated, and the detection accuracy of the cable is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only preferred embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flow chart of a cable fault double-end positioning method based on long test pulses according to the present invention.
Detailed Description
For a better understanding of the technical content of the present invention, a specific example is provided below, and the present invention is further described with reference to the accompanying drawings.
Referring to fig. 1, the cable fault double-end positioning method based on long test pulse provided by the invention comprises the following steps:
S1, constructing two groups of mutually orthogonal coding pulse trains, and respectively distributing the coding pulse trains to the near end and the far end of a fault cable;
The specific steps of the step S1 are as follows:
Step S11, two groups of mutually orthogonal coding pulses with duration of l and length of k are determined;
Both signals in the above encoded pulse group need to satisfy certain orthogonality conditions: for both signals x (x 1,x2,x3,…,xn) and y (y 1,y2,y3,…,yn), if present Wherein ρ xy is a cross-correlation function, the two signals are considered to be orthogonal signals, wherein the value of the two signals can only be 0 or 1 for digital coding, i.e. the signals x and y consist of the numbers 0 and 1.
Step S12, splicing k coding pulses of each group in the step S11 into a coding pulse string;
wherein the length of the code pulse train does not exceed L/v, L is the length of the fault cable, v is the propagation speed of electromagnetic waves in the cable,
Step S13, the code pulse trains are denoted as X 1 and X 2, respectively, and are allocated to the near end and the far end of the faulty cable, respectively.
S2, adopting a high-voltage flashover method to enable a fault point of a fault cable to be in an arcing state, and arranging a traveling wave detection device and a GPS module at the head end and the tail end of the fault cable;
when the cable breaks down, the cable is subjected to equivalent circuit analysis, the fault point can be regarded as an equivalent capacitor, when the equivalent capacitor of the fault cable is charged by using a capacitive high-voltage power supply with breakdown voltage greater than or equal to the equivalent capacitor, the fault point breaks down, and meanwhile, the capacitive high-voltage power supply in the equipment discharges to the cable through a current limiting resistor, so that the cable high-resistance fault maintains an arcing state, and the electric quantity accumulated on the cable flows into the ground.
And traveling wave detection devices and GPS modules are added at the head end and the tail end of the cable to ensure the synchronism of the time at the two ends so as to ensure that the two ends of the fault cable can synchronously receive fault information.
Step S3, different coding pulse trains are simultaneously sent at the near end and the far end of the fault cable, and a local signal propagated in the fault cable is recorded until reaching the end time;
The end time T end is ≡max (T, 3L/v), where T is the duration of the arcing state.
S4, predicting a local signal by adopting an opposite-end coding pulse string, and storing a predicted residual signal;
The method comprises the following specific steps:
step S41, a first N-order autocorrelation vector A of a local signal and a first N-order cross correlation vector C of a local signal and an opposite end coding pulse string are obtained, wherein N is the order of an FIR filter;
Step S42, expanding the first N-order autocorrelation vector A into a toeplitz matrix Q of N;
step S43, calculating a unit impulse response h=q -1 C of the FIR filter;
Step S44, filtering the local signal with an FIR filter, and obtaining predicted residual signals Y 1 and Y 2.
Step S5, performing cross correlation on the coding pulse trains at the near end and the far end of the fault cable and respective residual signals, wherein a calculation formula is as follows:
Wherein R 1 (τ) is a near-end cross-correlation calculation formula, R 2 (τ) is a far-end cross-correlation calculation formula, X 1 and X 2 are code pulse strings, Y 1 and Y 2 are residual signals, and τ is a time delay.
Then calculating the time difference between the reflected signal and the transmitted signal:
s6, calculating to obtain the fault point position of the fault cable according to the time difference Wherein v is the propagation speed of electromagnetic waves in the cable, and t is the time difference between the reflected signal and the transmitted signal calculated in step S5.
The method has the following five advantages:
(1) Compared with the single-end positioning method, the method has the advantages that the double-end positioning method is used, the problem of test blind areas in the single-end positioning method can be effectively solved, meanwhile, the problem of reflection pulse attenuation caused by traveling wave transmission attenuation can be effectively solved, and the overall detection accuracy is improved.
(2) The double-end detection method and the double-end detection device adopt long pulses to detect at the same time, can ensure that at least one end can fully utilize the duration of the large pulses, increase the time-wide bandwidth product under the condition of a certain bandwidth, and can effectively improve the accuracy and the robustness of fault detection.
(3) The invention uses orthogonal coding mode when transmitting pulse, and uses self-adaptive offset to eliminate the influence of the transmitting signal of opposite end on local detection, thus allowing the pulses to overlap each other, effectively distinguishing the transmitting pulse transmitted by opposite end, effectively reducing the influence of using double-end transmitting test pulse at the same time, and effectively improving the accuracy of fault point detection.
(4) The time difference between the reflected signal and the transmitted signal is calculated by adopting a double-end weighting method, so that the estimation of the time difference can be automatically obtained according to the advantages and disadvantages of near-end and far-end detection, and the detection robustness is improved.
(5) The design mode of the orthogonal code pulse string can enable the detection end near the fault point to effectively detect partial orthogonal code pulse even if the detection end can not receive the whole pulse string, thereby providing useful information for correct detection.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (8)
1. The cable fault double-end positioning method based on the long test pulse is characterized by comprising the following steps of:
S1, constructing two groups of mutually orthogonal coding pulse trains, and respectively distributing the coding pulse trains to the near end and the far end of a fault cable;
S2, adopting a high-voltage flashover method to enable a fault point of a fault cable to be in an arcing state, and arranging a traveling wave detection device and a GPS module at the head end and the tail end of the fault cable;
Step S3, different coding pulse trains are simultaneously sent at the near end and the far end of the fault cable, and a local signal propagated in the fault cable is recorded until reaching the end time;
s4, predicting a local signal by adopting an opposite-end coding pulse string, and storing a predicted residual signal, wherein the method specifically comprises the following steps:
step S41, a first N-order autocorrelation vector A of a local signal and a first N-order cross correlation vector C of a local signal and an opposite end coding pulse string are obtained, wherein N is the order of an FIR filter;
Step S42, expanding the first N-order autocorrelation vector A into a toeplitz matrix Q of N;
step S43, calculating a unit impulse response h=q -1 C of the FIR filter;
Step S44, filtering the local signal by using an FIR filter, and obtaining predicted residual signals Y 1 and Y 2;
s5, performing cross-correlation on the coded pulse trains at the near end and the far end of the fault cable and respective residual signals, and calculating to obtain the time difference between the reflected signals and the transmitted signals;
and S6, calculating to obtain the fault point position of the fault cable according to the time difference.
2. The method for locating two ends of a cable fault based on long test pulses according to claim 1, wherein the specific steps of step S1 are as follows:
Step S11, two groups of mutually orthogonal coding pulses with duration of l and length of k are determined;
Step S12, splicing k coding pulses of each group in the step S11 into a coding pulse string;
Step S13, the code pulse trains are denoted as X 1 and X 2, respectively, and are allocated to the near end and the far end of the faulty cable, respectively.
3. The method for locating both ends of cable fault based on long test pulse according to claim 2, wherein the quadrature condition satisfied by the encoded pulse in step S11 is: for both signals x (x 1,x2,x3,…,xn) and y (y 1,y2,y3,…,yn), if presentThe two signals are considered to be orthogonal signals, where ρ xy is a cross-correlation function.
4. The method according to claim 2, wherein the length of the code pulse train in the step S12 does not exceed L/v, where L is the length of the faulty cable and v is the propagation speed of the electromagnetic wave in the cable.
5. The method according to claim 4, wherein the ending time T end of the step S3 is equal to or longer than max (T, 3L/v), wherein T is the duration of the arcing state.
6. The method for locating two ends of a cable fault based on long test pulses according to claim 1, wherein the calculation formula for cross-correlating the coded pulse trains at the near end and the far end of the faulty cable with the respective residual signals in step S5 is as follows:
Wherein R 1 (τ) is a near-end cross-correlation calculation formula, R 2 (τ) is a far-end cross-correlation calculation formula, X 1 and X 2 are code pulse strings, Y 1 and Y 2 are residual signals, and τ is a time delay.
7. The method for locating two ends of cable fault according to claim 1, wherein the calculation formula for calculating the time difference between the reflected signal and the transmitted signal in step S5 is:
8. the method for locating two ends of a cable fault based on long test pulses as claimed in claim 1, wherein the calculation formula in step S6 is:
wherein v is the propagation speed of electromagnetic waves in the cable, and t is the time difference between the reflected signal and the transmitted signal calculated in step S5.
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