CN114280418A - Transmission line fault positioning method and device based on traveling wave frequency - Google Patents
Transmission line fault positioning method and device based on traveling wave frequency Download PDFInfo
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Abstract
The invention discloses a transmission line fault positioning method and a transmission line fault positioning device based on traveling wave frequency, wherein the method comprises the following steps: respectively obtaining the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line; respectively obtaining the arrival time of the traveling wave head at each end of the line, and determining the frequency of the traveling wave head corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected frequency spectrum of the traveling wave head at each end of the line; determining the traveling wave velocity of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of the traveling wave head; and determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head. The invention corrects the traveling wave frequency by a loop iteration method, and can improve the fault positioning accuracy.
Description
Technical Field
The invention belongs to the technical field of power electronics, particularly relates to a fault positioning technology of a power system, and more particularly relates to a transmission line fault positioning method based on traveling wave frequency.
Background
At present, transmission line fault positioning methods based on fault traveling waves, especially fault traveling wave frequencies, have been widely used. When the traveling wave is transmitted on the power transmission line, due to the loss of the line and the refraction and reflection phenomenon at the bus, the traveling wave frequency reaching the bus is distorted and is different from the initial traveling wave frequency, so that the accuracy of fault positioning based on the traveling wave frequency at the bus is reduced, and the fault maintenance and recovery are influenced.
Disclosure of Invention
The invention aims to provide a power transmission line fault positioning method and a power transmission line fault positioning device based on traveling wave frequency, which correct the traveling wave frequency through a loop iteration method and improve the fault positioning accuracy.
In order to achieve the purpose, the power transmission line fault positioning method provided by the invention is realized by adopting the following technical scheme:
a transmission line fault positioning method based on traveling wave frequency is characterized by comprising the following steps:
respectively obtaining the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
respectively obtaining the arrival time of the traveling wave head at each end of the line, and determining the frequency of the traveling wave head corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected frequency spectrum of the traveling wave head at each end of the line;
determining the traveling wave velocity of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of the traveling wave head;
determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
the method for correcting the frequency spectrum by adopting the loop iteration method to obtain the corrected traveling wave head frequency spectrum of each end of the line comprises the following steps:
(a) calculating the nth iterationCorrection current of generation
n is the number of iterations;
defining the correction spectrum obtained for the nth iteration
To and correct the frequency spectrum
A corresponding correction current;
respectively, the system impedance and line wave impedance at the nth iteration
Determining; i.e. ibus(fbus) For the wave head of the traveling wave of the original current, fbusThe frequency spectrum of the wave head of the original current traveling wave;
(b) based on the correction current
Obtaining a corresponding corrected spectrum
(c) Calculating the spectrum error of the nth iteration
(d) N is n + 1;
(e) and determining whether the conditions are satisfied
Or N > N1If yes, the loop is ended, and the loop is ended
Determining the corrected traveling wave head frequency spectrum; otherwise, returning to (a); Δ fthrIs a predetermined error threshold, N1Is a preset maximum number of iterations.
In order to achieve the purpose, the power transmission line fault positioning device provided by the invention adopts the following technical scheme:
a transmission line fault location device based on traveling wave frequency, the device comprising:
the corrected traveling wave head frequency spectrum acquisition unit is used for acquiring the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
the traveling wave head arrival time acquisition unit is used for respectively acquiring the arrival time of the traveling wave head at each end of the line;
the traveling wave head frequency acquisition unit is used for determining the traveling wave head frequency corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected traveling wave head frequency spectrum at each end of the line;
the traveling wave velocity obtaining unit is used for determining the traveling wave velocity of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of a traveling wave head;
and the fault position determining unit is used for determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head.
The invention also provides a power transmission system which comprises a power transmission line and a converter station which is positioned at the end part of the power transmission line and connected through the power transmission line, and the power transmission system also comprises the power transmission line fault positioning device based on the traveling wave frequency.
The present invention also provides an electronic device, including:
a memory having a computer program stored therein;
a processor configured to execute the computer program in the memory to implement the traveling wave frequency based transmission line fault location method described above.
Compared with the prior art, the invention has the advantages and positive effects that:
according to the power transmission line fault positioning method and device based on the traveling wave frequency, the current traveling wave frequency spectrum is corrected by adopting a cyclic iteration method, the distorted traveling wave frequency obtained at the bus is recovered to the initial traveling wave frequency, fault positioning is carried out based on the corrected frequency and the frequency-dependent characteristic, the fault positioning accuracy is improved, and the maintenance recovery speed of the power transmission line fault is further improved.
Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flow chart of an embodiment of a transmission line fault location method based on traveling wave frequency according to the present invention;
fig. 2 is a schematic structural diagram of an embodiment of the transmission line fault positioning device based on traveling wave frequency according to the present invention;
FIG. 3 is a schematic diagram of an embodiment of an electronic device of the present invention;
fig. 4 is a schematic structural view of an embodiment of the power transmission system of the present invention;
fig. 5 is a simulated waveform of a double-ended current traveling wave in the event of a fault in the power transmission system of the embodiment of fig. 4;
fig. 6 is a spectrum diagram of both ends in the event of a fault in the power transmission system of the embodiment of fig. 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples.
In the prior art, when the fault of the power transmission line is located based on the traveling wave frequency, the traveling wave is lost when being transmitted on the power transmission line, and the traveling wave is refracted and reflected when reaching the bus, so that the traveling wave frequency obtained at the bus is distorted, and is different from the initial traveling wave frequency when the fault occurs. In order to solve the technical problem, the invention creatively provides the method for correcting the traveling wave frequency acquired at the bus to restore the initial traveling wave frequency, thereby improving the precision of fault positioning based on the traveling wave frequency.
Fig. 1 is a schematic flow chart of an embodiment of a transmission line fault location method based on traveling wave frequency according to the present invention, and specifically, is a schematic flow chart of an embodiment of implementing fault location based on traveling wave frequency correction.
As shown in fig. 1, the embodiment uses the following process to locate the transmission line fault.
Step 11: respectively obtaining the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line.
In order to be able to determine the speed of transmission of the travelling wave from the frequency, it is necessary to obtain the travelling wave head frequency, which can be determined from the frequency spectrum of the current travelling wave head. In this embodiment, the spectrum of the original current traveling wave head at each end of the line is first obtained. The frequency spectrum of the original current traveling wave head can be realized by adopting a frequency extraction method based on the original current traveling wave head.
In other preferred embodiments, the frequency spectrum of the original current traveling wave head can be calculated by adopting a HHT (Hilbert-Huang transform) method based on the original current traveling wave head. The specific implementation of calculating the spectrum using HHT may be made using existing techniques and will not be described in further detail herein.
In other embodiments, the desired spectrum may also be obtained using an S-transform method.
As mentioned above, the original current traveling wave head frequency obtained at each end of the line is distorted, and the original traveling wave head frequency needs to be recovered. Therefore, in this embodiment, the frequency spectrum of the original current traveling wave head is corrected by using a loop iteration method, and the corrected traveling wave head frequency spectrum at each end of the line is obtained.
The specific correction method is realized by adopting the following processes:
setting iteration number N and setting iteration number upper limit N1I.e. maximum number of iterations, e.g. setting N1＝10。
(a) Calculating the correction current of the nth iteration
Wherein n is the number of iterations, starting from 1;
defining the correction spectrum obtained for the nth iteration
ibus(fbus) The wave head is an original current traveling wave head and can be directly detected and obtained; f. ofbusFor the frequency spectrum of the wave head of the traveling wave of the original current, according to ibus(fbus) Can be directly calculated;
to and correct the frequency spectrum
A corresponding correction current;
respectively, the system impedance and the line wave impedance at the nth iteration, which are intrinsic parameters of the power transmission system,depending on the structural parameters of the transmission system and the travelling frequency, for a fixed transmission system the two impedances follow the travelling frequency variation, which may be dependent on
The specific determination method is the prior art.
(b) Based on the correction current
Obtaining a corresponding corrected spectrum
Specifically, it is preferable to correct the current
Adopting HHT conversion method to calculate and obtain corresponding correction frequency spectrum
In other embodiments, the corresponding spectrum may also be obtained by using an S transform method.
(c) Calculating the spectrum error of the nth iteration
(d) Let n be n + 1.
(e) And determining whether the conditions are satisfied
Or N > N1If yes, the loop is ended, and the loop is ended
Determining the frequency spectrum of the corrected traveling wave head, wherein the frequency spectrum is basically the frequency spectrum corresponding to the initial traveling wave head when the fault occurs; otherwise, return to (a), continueAnd (5) continuing iteration. Wherein, Δ fthrIs a preset error threshold.
Step 12: and respectively acquiring the arrival time of the traveling wave head at each end of the line, and determining the frequency of the traveling wave head corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected frequency spectrum of the traveling wave head at each end of the line.
The arrival time of the fault traveling wave head can be obtained by adopting the prior art. In a preferred embodiment, the arrival time of the fault traveling wave head is determined according to the amplitude of the fault traveling wave. The specific implementation method comprises the following steps:
calculating and determining whether a second criterion is satisfied: x (t) > c xmax。
And determining the first moment meeting the second criterion as the arrival moment of the fault traveling wave head.
Wherein, x (t) is the fault traveling wave amplitude at the time t, which is a known value, and after the good modulus is selected for the fault traveling wave signal, the corresponding instantaneous value is the fault traveling wave amplitude. x is the number ofmaxIs the peak value of the amplitude of the fault traveling wave in the data window, and is also a known value. c is a known proportionality coefficient, 0 < c < 1. In one specific embodiment, c is 0.5.
The arrival time of the traveling wave head at each end of the line is determined by adopting the mode, and then the traveling wave head frequency corresponding to the arrival time of the traveling wave head at each end can be determined according to the frequency spectrum of each end.
Step 13: and determining the traveling wave speed of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of the traveling wave head.
The frequency-dependent characteristic of each end of the line is determined according to the structural parameters and the electrical parameters of the power transmission line, and the specific determination method can be realized by adopting the prior art.
As a preferred embodiment, the frequency dependent characteristic of the transmission line is determined by the following method:
calculating complex penetration depth
Where ρ is the earth resistivity, μ is the vacuum permeability, both of known values, j is the imaginary unit, and f is the traveling wave frequency. For earth resistivity, different soils, rocks, etc. have different resistivities, which can generally be approximated by a typical value, for example, ρ ═ 100 Ω m. In one embodiment, the vacuum permeability is selected to be 4 π × 10-7H/m。
A, B, C calculating self-impedance coefficient Z of three-phase wire1(1)、Z1(2)And Z1(3)：
Wherein R is1(1)、R1(2)And R1(3)A, B, C three-phase conductor DC resistance per unit length, h1(1)、h1(2)And h1(3)Height of ABC three-phase wire from ground, GMR1(1)、GMR1(2)And GMR1(3)The equivalent radius of the ABC three-phase conductor, b is the splitting number of the split sub-conductor, r is the radius of the split sub-conductor, and d is the distance between the split sub-conductors. The parameter values are known values and are determined by the line structure parameters, the electrical parameters and the like.
Calculating A, B, C the mutual impedance coefficient Z between three-phase conductors2(1-2)、Z2(2-1)、Z2(1-3)、Z2(3-1)、Z2(2-3)、Z2(3-2)：
Wherein Z is2(1-2)、Z2(2-1)、Z2(1-3)、Z2(3-1)、Z2(2-3)、Z2(3-2)The mutual impedance coefficients between the A phase lead and the B phase lead, between the B phase lead and the A phase lead, between the A phase lead and the C phase lead, between the C phase lead and the A phase lead, between the B phase lead and the C phase lead, and between the C phase lead and the B phase lead, d2(1-2)＝d2(2-1)、d2(1-3)＝d2(3-1)、d2(2-3)＝d2(3-2)Respectively, the space between the A-phase wire and the B-phase wire, the space between the A-phase wire and the C-phase wire, the space between the B-phase wire and the C-phase wire, and D2(1-2)Is the distance between the mirror image of the A-phase conductor and the B-phase conductor, D2(2-1)Is the distance between the mirror image of the B-phase conductor and the A-phase conductor, D2(1-3)Is the distance between the mirror images of the A-phase conductor and the C-phase conductor, D2(3-1)Is the distance between the C-phase conductor and the mirror image of the A-phase conductor, D2(2-3)Is the distance between the mirror images of the B-phase and C-phase conductors, D2(3-2)Is the distance between the C-phase conductor and the mirror image of the B-phase conductor. After the line is determined, the distances are all known values
Further explanation is as follows: z2(1-2)The mutual impedance coefficient between the A-phase lead and the B-phase lead is the mutual impedance coefficient between the A-phase lead and the B-phase lead when the A-phase lead is seen based on the position of the A-phase lead; z2(2-1)The mutual impedance coefficient between the B-phase conductor and the a-phase conductor refers to the mutual impedance coefficient between the a-phase conductor and the B-phase conductor when viewed from the B-phase conductor position. D2(1-2)The distance between the A-phase conductor and the mirror image of the B-phase conductor refers to the distance between the A-phase conductor and the mirror image of the B-phase conductor. The same holds true for the remaining parameters.
Calculating the self-impedance coefficient Z of the lightning conductor3(1)、Z3(2)：
Wherein Z is3(1)And Z3(2)The self-impedance coefficient of the first and second lightning conductor, R3(1)And R3(2)A direct current resistance per unit length of the first lightning conductor and a direct current resistance per unit length of the second lightning conductor, h3(1)And h3(2)The height of the first lightning conductor from the ground and the height of the second lightning conductor from the ground, GMR, respectively3(1)And GMR3(2)Respectively the equivalent radius of the first lightning conductor and the equivalent radius of the second lightning conductor. After the route is determined, R3(1)、R3(2)、h3(1)、h3(2)And GMR3(1)、GMR3(2)Are all known values.
Calculating the mutual impedance coefficient Z between the conducting wire and the lightning conductor4(1-1)、Z4(1-2)、Z4(1-3)、Z4(2-1)、Z4(2-2)、Z4(2-3)：
Wherein Z is4(1-1)、Z4(1-2)、Z4(1-3)、Z4(2-1)、Z4(2-2)、Z4(2-3)The mutual impedance coefficients are respectively between a first lightning conductor and an A-phase lead wire, between the first lightning conductor and a B-phase lead wire, between the first lightning conductor and a C-phase lead wire, between a second lightning conductor and the A-phase lead wire, between the second lightning conductor and the B-phase lead wire and between the second lightning conductor and the C-phase lead wire; d4(1-1)、d4(1-2)、d4(1-3)、d4(2-1)、d4(2-2)、d4(2-3)Between the first lightning conductor and the A-phase conductor, between the first lightning conductor and the B-phase conductor, between the first lightning conductor and the C-phase conductor, between the second lightning conductor and the A-phase conductor, between the second lightning conductor and the B-phase conductor, and between the second lightning conductor and the B-phase conductorSpacing between C-phase conductors, D4(1-1)、D4(1-2)、D4(1-3)、D4(2-1)、D4(2-2)、D4(2-3)The distances between the first lightning conductor and the A-phase conductor image, between the first lightning conductor and the B-phase conductor image, between the first lightning conductor and the C-phase conductor image, between the second lightning conductor and the A-phase conductor image, between the second lightning conductor and the B-phase conductor image and between the second lightning conductor and the C-phase conductor image are respectively. After the wiring is determined, the distances are known.
Calculating the mutual impedance coefficient Z between the lightning conductor and the lightning conductor5(1-2)、Z5(2-1)：
Wherein Z is5(1-2)、Z5(2-1)The mutual impedance coefficients between the first lightning conductor and the second lightning conductor and between the second lightning conductor and the first lightning conductor are respectively set; d5(1-2)＝d5(2-1)For the spacing between the first and second conductor, D5(1-2)Is the distance between the mirror image of the first and second lightning conductor, D5(2-1)The spacing between the second lightning conductor and the mirror image of the first lightning conductor. After the wiring is determined, the distances are known.
Determining an impedance coefficient matrix Z:
wherein the content of the first and second substances,
a, B, C calculating the self-potential coefficient P of three phases1(1)、P1(2)、P1(3)：
Wherein ε represents a vacuum dielectric constant and is a known value.
A, B, C calculating the mutual potential coefficient P between three phases2(1-2)、P2(2-1)、P2(1-3)、P2(3-1)、P2(2-3)、P2(3-2)：
Wherein, P2(1-2)、P2(2-1)、P2(1-3)、P2(3-1)、P2(2-3)、P2(3-2)The mutual potential coefficients are respectively between the A-phase lead and the B-phase lead, between the B-phase lead and the A-phase lead, between the A-phase lead and the C-phase lead, between the C-phase lead and the A-phase lead, between the B-phase lead and the C-phase lead, and between the C-phase lead and the B-phase lead.
Calculating the self-potential coefficient P of the lightning conductor3(1)、P3(2)：
Wherein, P3(1)And P3(2)The self-potential coefficient of the first lightning conductor and the self-potential coefficient of the second lightning conductor are respectively.
Calculating mutual potential coefficient P between the conducting wire and the lightning conductor4(1-1)、P4(1-2)、P4(1-3)、P4(2-1)、P4(2-2)、P4(2-3)：
Wherein, P4(1-1)、P4(1-2)、P4(1-3)、P4(2-1)、P4(2-2)、P4(2-3)The mutual potential coefficients are respectively between the first lightning conductor and the A-phase wire, between the first lightning conductor and the B-phase wire, between the first lightning conductor and the C-phase wire, between the second lightning conductor and the A-phase wire, between the second lightning conductor and the B-phase wire and between the second lightning conductor and the C-phase wire.
Calculating mutual potential coefficient P between the lightning conductor and the lightning conductor5(1-2)、P5(2-1)：
Wherein, P5(1-2)、P5(2-1)The mutual potential coefficients between the first lightning conductor and the second lightning conductor and between the second lightning conductor and the first lightning conductor are respectively.
Determining a potential coefficient matrix P:
determining a capacitance coefficient matrix Y:
Y＝j2πf×P-1；
determining a transmission parameter gamma of the power transmission line according to the impedance coefficient matrix Z and the capacitance coefficient matrix Y:
wherein, both alpha and beta are real numbers.
And finally, determining a frequency-dependent characteristic according to the transmission parameter gamma of the power transmission line:
wherein v is the traveling wave velocity and f is the frequency.
In the frequency-dependent characteristic, β is a known value, and then, after the frequency f is determined, the wave velocity corresponding to the frequency can be determined.
Specifically, the traveling wave head frequency f of each end of the line is obtainedTWkThen the travelling wave speed v of each end of the line can be determinedk：
Wherein f isTWkObtaining the wave head frequency of the traveling wave at the k-th end converter station side by adopting the method in the step 12; v. ofkThe wave speed of the traveling wave at the k-th end converter station side.
Step 14: and determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head.
The specific implementation of this step can adopt the existing technology.
As a preferred implementation mode, the distance between a fault point and one end of the off-line is determined according to the traveling wave speed and the arrival time of the traveling wave head, and the fault is positioned. Specifically, the fault location is calculated according to the following formula:
wherein l is the distance between the fault and the M end of the line, vMAnd vNTravelling wave velocity, t, of line M and N ends respectivelyMAnd tNRespectively the arrival time of the traveling wave heads at the M end and the N end of the line; and L is the total length of the transmission line between the end M of the line and the end N of the line and is a known value.
By adopting the method of the embodiment and the preferred embodiment thereof, the power transmission line fault positioning method and the positioning device based on the traveling wave frequency, the current traveling wave frequency spectrum is corrected by adopting a cycle iteration method, the distorted traveling wave frequency acquired at the bus is recovered to the initial traveling wave frequency, and then the fault positioning is carried out based on the corrected frequency and the frequency-dependent characteristic, so that the fault positioning accuracy is improved, and the maintenance recovery speed of the power transmission line fault is further improved.
Fig. 2 is a schematic structural diagram of an embodiment of the transmission line fault location device based on traveling wave frequency according to the present invention.
As shown in fig. 2, the device of this embodiment includes the structural units, the functions of the structural units, and the connection relationship among the structural units, which are described in detail below.
The apparatus of this embodiment comprises:
and the corrected traveling wave head frequency spectrum obtaining unit 21 is configured to obtain a frequency spectrum of the original current traveling wave head at each end of the line, and correct the frequency spectrum by using a cyclic iteration method to obtain a corrected traveling wave head frequency spectrum at each end of the line.
And a traveling wave head arrival time acquiring unit 22, configured to acquire arrival times of traveling wave heads at each end of the line respectively.
The traveling wave head frequency obtaining unit 23 is configured to determine a traveling wave head frequency corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected traveling wave head frequency spectrum at each end of the line obtained by the corrected traveling wave head frequency spectrum obtaining unit 21 and the arrival time of the traveling wave head obtained by the traveling wave head arrival time obtaining unit 22.
And a traveling wave velocity obtaining unit 24, configured to determine a traveling wave velocity at each end of the line according to the frequency-dependent characteristic at each end of the line and the traveling wave head frequency obtained by the traveling wave head frequency obtaining unit 23.
And a fault position determining unit 25, configured to determine a fault position according to the traveling wave speed of each end of the line acquired by the traveling wave speed acquiring unit 24 and the arrival time of the traveling wave head acquired by the traveling wave head arrival time acquiring unit 22.
The fault location device of the embodiment runs a corresponding software program, realizes the fault location of the power transmission line according to the process of the embodiment of the method of fig. 1 and the preferred embodiment of the method thereof, and achieves the same technical effect as the embodiment of the method.
The power transmission line fault positioning device of the embodiment is applied to a power transmission system, the power transmission system comprises a power transmission line and a converter station which is arranged at the end part of the power transmission line and connected through the power transmission line, faults occurring on the power transmission line can be positioned, and the distance between the faults occurring on the power transmission line and the converter station is determined.
Fig. 3 shows a schematic structural diagram of an embodiment of the electronic device of the present invention. The electronic device comprises a memory 31, a processor 32 and a computer program 311 stored on the memory 31, wherein the processor is configured to execute the computer program 311, so as to implement the power transmission line fault location method of the embodiment of fig. 1 and the preferred embodiment thereof, and achieve the same technical effects as the method embodiment.
Fig. 4 is a schematic structural diagram of an embodiment of the power transmission system of the present invention. As shown in fig. 4, in this embodiment, the power transmission system includes two converter stations, i.e., an M-terminal converter station and an N-terminal converter station, respectively, and F is a fault point, which is a typical fault occurring on the power transmission line between the two-terminal bus bars. ZSM、ZSNSystem impedance of M terminal and end side, ZTMIs the line wave impedance between the fault points F and M, ZTNLine wave impedance at fault point F and NM、iNThe current of the M terminal and the current of the N terminal are respectively.
Fig. 5 is a simulated waveform of a double-ended current traveling wave at a typical fault in the power transmission system of fig. 4. Wherein (a) is a traveling wave form at a fault point F, and iFM、iFNRespectively are current traveling wave waveforms transmitted from a fault point F to an M end and an N end; (b) the current traveling wave waveform at the double-end bus is shown.
Monitoring according to the fault positioning method, wherein the arrival time of the fault at the M end and the arrival time at the N end are respectively as follows: t is tM＝1.303s，tN＝1.704s。
Fig. 6 is a spectrum diagram of both ends in the event of a typical fault in the power transmission system of fig. 4. Wherein (a) is the traveling wave frequency spectrum at the fault point F, specifically, FFM、fFNRespectively traveling wave frequency spectrums transmitted to the M end and the N end by the fault point F; (b) is double-endedFrequency spectrum of original current traveling wave head at bus fM、fNRespectively obtaining the frequency spectrums of original current traveling wave heads at the M-end bus and the N-end bus; (c) correcting the frequency spectrum of the travelling wave head at the position of the double-end busM、fNAnd respectively obtaining the corrected traveling wave head frequency spectrums at the M-end bus and the N-end bus.
Monitoring according to the fault positioning method, and monitoring:
the traveling wave head frequencies of the fault point F propagated to the M end and the N end are both FFM＝fFN＝110.3kHz。
When the frequency spectrum is not corrected, the frequencies of the arrival time of the fault traveling wave head at the M-end bus and the N-end bus are respectively fM＝143.8kHz、fN＝156.5kHz。
After the frequency spectrum correction, the frequencies of the arrival time of the fault traveling wave head at the M-end bus and the N-end bus are respectively fM＝101.6kHz、fN110.4 kHz. The frequency obtained after correction is closer to the frequency of the original traveling wave head at the fault point.
The wave velocities of fault traveling waves at the M-end bus and the N-end bus are respectively vM＝298.935km/ms、vM＝298.965km/ms。
And based on the obtained traveling wave speed and the arrival time of the traveling wave head, when the total length of the power transmission line between the M-end bus and the N-end bus is L-300 km, the distance between the fault point F and the M-end bus is L-90.052 km.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (8)
1. A transmission line fault positioning method based on traveling wave frequency is characterized by comprising the following steps:
respectively obtaining the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
respectively obtaining the arrival time of the traveling wave head at each end of the line, and determining the frequency of the traveling wave head corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected frequency spectrum of the traveling wave head at each end of the line;
determining the traveling wave velocity of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of the traveling wave head;
determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
the method for correcting the frequency spectrum by adopting the loop iteration method to obtain the corrected traveling wave head frequency spectrum of each end of the line comprises the following steps:
(a) calculating the correction current of the nth iteration
n is the number of iterations;
defining the correction spectrum obtained for the nth iteration
To and correct the frequency spectrum
A corresponding correction current;
respectively, the system impedance and line wave impedance at the nth iteration
Determining; i.e. ibus(fbus) For the wave head of the traveling wave of the original current, fbusThe frequency spectrum of the wave head of the original current traveling wave;
(b) based on the correction current
Obtaining a corresponding corrected spectrum
(c) Calculating the spectrum error of the nth iteration
(d) N is n + 1;
(e) and determining whether the conditions are satisfied
Or N > N1If yes, the loop is ended, and the loop is ended
Determining the corrected traveling wave head frequency spectrum; otherwise, returning to (a); Δ fthrIs a predetermined error threshold, N1Is a preset maximum number of iterations.
2. The traveling wave frequency-based transmission line fault location method according to claim 1,
the acquiring of the frequency spectrum of the original current traveling wave head at each end of the line specifically includes: acquiring an original current traveling wave head at each end of a line, and calculating the frequency spectrum of the original current traveling wave head by adopting an HHT (Hilbert-Huang transform) method;
based on the correction current
Obtaining a corresponding corrected spectrum
The method specifically comprises the following steps: for the correction current
The corresponding correction frequency spectrum is obtained by calculation by adopting a HHT conversion method
3. The method for positioning the fault of the power transmission line based on the traveling wave frequency according to claim 1, wherein the obtaining of the arrival time of the traveling wave head at each end of the line specifically comprises:
calculating and determining whether a first criterion is satisfied: x (t) > c xmax；
Determining a first moment meeting the first criterion as the arrival moment of the traveling wave head;
wherein x (t) is the traveling wave amplitude at the time t and is a known value; x is the number ofmaxThe peak value of the amplitude value of the traveling wave in the data window is a known value; c is a known proportionality coefficient, 0 < c < 1.
4. The method for positioning the fault of the power transmission line based on the traveling wave frequency according to claim 1, wherein the fault position is determined according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head, and specifically comprises:
the fault location is calculated according to the following formula:
wherein l is the distance between the fault and the M end of the line, vMAnd vNTravelling wave velocity, t, of line M and N ends respectivelyMAnd tNRespectively the arrival time of the traveling wave heads at the M end and the N end of the line; and L is the total length of the transmission line between the end M of the line and the end N of the line and is a known value.
5. The method for positioning the fault of the transmission line based on the traveling wave frequency according to any one of claims 1 to 4, wherein the determining the traveling wave speed of each end of the line according to the frequency-dependent characteristic and the traveling wave head frequency of each end of the line specifically comprises:
the frequency dependent characteristic is obtained by the following method:
calculating complex penetration depth
Wherein rho is earth resistivity, mu is vacuum magnetic conductivity which are known values, j is an imaginary unit, and f is traveling wave frequency;
a, B, C calculating self-impedance coefficient Z of three-phase wire1(1)、Z1(2)And Z1(3)：
Wherein R is1(1)、R1(2)And R1(3)A, B, C three-phase conductor DC resistance per unit length, h1(1)、h1(2)And h1(3)Height of ABC three-phase wire from ground, GMR1(1)、GMR1(2)And GMR1(3)The equivalent radius of the ABC three-phase conductor, b is the splitting number of the split sub-conductor, r is the radius of the split sub-conductor, and d is the distance between the split sub-conductors;
calculating A, B, C the mutual impedance coefficient Z between three-phase conductors2(1-2)、Z2(2-1)、Z2(1-3)、Z2(3-1)、Z2(2-3)、Z2(3-2)：
Wherein Z is2(1-2)、Z2(2-1)、Z2(1-3)、Z2(3-1)、Z2(2-3)、Z2(3-2)The mutual impedance coefficients between the A phase lead and the B phase lead, between the B phase lead and the A phase lead, between the A phase lead and the C phase lead, between the C phase lead and the A phase lead, between the B phase lead and the C phase lead, and between the C phase lead and the B phase lead, d2(1-2)＝d2(2-1)、d2(1-3)＝d2(3-1)、d2(2-3)＝d2(3-2)Respectively, the space between the A-phase wire and the B-phase wire, the space between the A-phase wire and the C-phase wire, the space between the B-phase wire and the C-phase wire, and D2(1-2)Is the distance between the mirror image of the A-phase conductor and the B-phase conductor, D2(2-1)Is the distance between the mirror image of the B-phase conductor and the A-phase conductor, D2(1-3)Is the distance between the mirror images of the A-phase conductor and the C-phase conductor, D2(3-1)Is the distance between the C-phase conductor and the mirror image of the A-phase conductor, D2(2-3)Is the distance between the mirror images of the B-phase and C-phase conductors, D2(3-2)The distance between the C-phase lead and the B-phase lead mirror image is set;
calculating the self-impedance coefficient Z of the lightning conductor3(1)、Z3(2)：
Wherein Z is3(1)And Z3(2)The self-impedance coefficient of the first and second lightning conductor, R3(1)And R3(2)A direct current resistance per unit length of the first lightning conductor and a direct current resistance per unit length of the second lightning conductor, h3(1)And h3(2)The height of the first lightning conductor from the ground and the height of the second lightning conductor from the ground, GMR, respectively3(1)And GMR3(2)Respectively the equivalent radius of the first lightning conductor and the equivalent radius of the second lightning conductor;
calculating the mutual impedance coefficient Z between the conducting wire and the lightning conductor4(1-1)、Z4(1-2)、Z4(1-3)、Z4(2-1)、Z4(2-2)、Z4(2-3)：
Wherein Z is4(1-1)、Z4(1-2)、Z4(1-3)、Z4(2-1)、Z4(2-2)、Z4(2-3)The mutual impedance coefficients are respectively between a first lightning conductor and an A-phase lead wire, between the first lightning conductor and a B-phase lead wire, between the first lightning conductor and a C-phase lead wire, between a second lightning conductor and the A-phase lead wire, between the second lightning conductor and the B-phase lead wire and between the second lightning conductor and the C-phase lead wire; d4(1-1)、d4(1-2)、d4(1-3)、d4(2-1)、d4(2-2)、d4(2-3)Respectively between the first lightning conductor and the A phase conductorThe distance between the lightning conductor and the B-phase conductor, between the first lightning conductor and the C-phase conductor, between the second lightning conductor and the A-phase conductor, between the second lightning conductor and the B-phase conductor, and between the second lightning conductor and the C-phase conductor, D4(1-1)、D4(1-2)、D4(1-3)、D4(2-1)、D4(2-2)、D4(2-3)The distances between a first lightning conductor and the A-phase conductor image, between the first lightning conductor and the B-phase conductor image, between the first lightning conductor and the C-phase conductor image, between a second lightning conductor and the A-phase conductor image, between the second lightning conductor and the B-phase conductor image and between the second lightning conductor and the C-phase conductor image are respectively;
calculating the mutual impedance coefficient Z between the lightning conductor and the lightning conductor5(1-2)、Z5(2-1)：
Wherein Z is5(1-2)、Z5(2-1)The mutual impedance coefficients between the first lightning conductor and the second lightning conductor and between the second lightning conductor and the first lightning conductor are respectively set; d5(1-2)＝d5(2-1)For the spacing between the first and second conductor, D5(1-2)Is the distance between the mirror image of the first and second lightning conductor, D5(2-1)The distance between the second lightning conductor and the first lightning conductor mirror image is set;
determining an impedance coefficient matrix Z:
wherein the content of the first and second substances,
a, B, C calculating the self-potential coefficient P of three phases1(1)、P1(2)、P1(3)：
Wherein ε is a vacuum dielectric constant;
a, B, C calculating the mutual potential coefficient P between three phases2(1-2)、P2(2-1)、P2(1-3)、P2(3-1)、P2(2-3)、P2(3-2)：
Wherein, P2(1-2)、P2(2-1)、P2(1-3)、P2(3-1)、P2(2-3)、P2(3-2)Mutual potential coefficients between the A-phase lead and the B-phase lead, between the B-phase lead and the A-phase lead, between the A-phase lead and the C-phase lead, between the C-phase lead and the A-phase lead, between the B-phase lead and the C-phase lead, and between the C-phase lead and the B-phase lead are respectively set;
calculating the self-potential coefficient P of the lightning conductor3(1)、P3(2)：
Wherein, P3(1)And P3(2)The self-potential coefficient of the first lightning conductor and the self-potential coefficient of the second lightning conductor are respectively set;
calculating mutual potential coefficient P between the conducting wire and the lightning conductor4(1-1)、P4(1-2)、P4(1-3)、P4(2-1)、P4(2-2)、P4(2-3)：
Wherein, P4(1-1)、P4(1-2)、P4(1-3)、P4(2-1)、P4(2-2)、P4(2-3)Mutual potential coefficients between a first lightning conductor and the A-phase wire, between the first lightning conductor and the B-phase wire, between the first lightning conductor and the C-phase wire, between a second lightning conductor and the A-phase wire, between the second lightning conductor and the B-phase wire and between the second lightning conductor and the C-phase wire are respectively set;
calculating mutual potential coefficient P between the lightning conductor and the lightning conductor5(1-2)、P5(2-1)：
Wherein, P5(1-2)、P5(2-1)Mutual potential coefficients between the first lightning conductor and the second lightning conductor and between the second lightning conductor and the first lightning conductor are respectively set;
determining a potential coefficient matrix P:
wherein the content of the first and second substances,
determining a capacitance coefficient matrix Y:
Y＝j2πf×P-1；
determining a transmission parameter gamma of the power transmission line according to the impedance coefficient matrix Z and the capacitance coefficient matrix Y:
wherein, both alpha and beta are real numbers;
determining the frequency dependent characteristic according to the transmission parameter gamma of the power transmission line:
wherein v is the traveling wave speed and f is the frequency;
obtaining the traveling wave head frequency f of each end of the lineTWkDetermining the traveling wave velocity v of each end of the linek：
Wherein f isTWkIs the wave head frequency v of the traveling wave at the k-th converter station sidekThe wave speed of the traveling wave at the k-th end converter station side.
6. A transmission line fault location device based on traveling wave frequency, the device comprising:
the corrected traveling wave head frequency spectrum acquisition unit is used for acquiring the frequency spectrum of the original current traveling wave head at each end of the line, and correcting the frequency spectrum by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
the traveling wave head arrival time acquisition unit is used for respectively acquiring the arrival time of the traveling wave head at each end of the line;
the traveling wave head frequency acquisition unit is used for determining the traveling wave head frequency corresponding to the arrival time of the traveling wave head at each end of the line according to the corrected traveling wave head frequency spectrum at each end of the line;
the traveling wave velocity obtaining unit is used for determining the traveling wave velocity of each end of the line according to the frequency-dependent characteristic of each end of the line and the frequency of a traveling wave head;
the fault position determining unit is used for determining the fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
the method for correcting the frequency spectrum by adopting the loop iteration method to obtain the corrected traveling wave head frequency spectrum of each end of the line comprises the following steps:
(a) calculating the correction current of the nth iteration
n is the number of iterations;
defining the correction spectrum obtained for the nth iteration
To and correct the frequency spectrum
A corresponding correction current;
respectively, the system impedance and line wave impedance at the nth iteration
Determining; i.e. ibus(fbus) For the wave head of the traveling wave of the original current, fbusThe frequency spectrum of the wave head of the original current traveling wave;
(b) based on the correction current
Obtaining a corresponding corrected spectrum
(c) Calculating the spectrum error of the nth iteration
(d) N is n + 1;
(e) and determining whether the conditions are satisfied
Or N > N1If yes, the loop is ended, and the loop is ended
Determining the corrected traveling wave head frequency spectrum; otherwise, returning to (a); Δ fthrIs a predetermined error threshold, N1Is a preset maximum number of iterations.
7. A power transmission system comprising a power transmission line and a converter station located at an end of the power transmission line and connected thereto via the power transmission line, wherein the power transmission system further comprises the power transmission line fault location apparatus based on traveling wave frequency according to claim 6.
8. An electronic device, characterized in that the electronic device comprises:
a memory having a computer program stored therein;
a processor configured to execute the computer program in the memory to implement the method of travelling wave frequency based power transmission line fault location of any of the preceding claims 1 to 5.
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