CN114280418B - 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 power transmission line fault positioning method and a positioning device based on traveling wave frequency, wherein the method comprises the following steps: the frequency spectrum of an original current traveling wave head at each end of the line is respectively obtained, and the frequency spectrum is corrected by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line; acquiring the arrival time of the traveling wave head at each end of the line respectively, and 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; according to the frequency dependent characteristic and the traveling wave head frequency of each end of the line, determining the traveling wave speed of each end of the line; 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, in particular relates to a fault positioning technology of a power system, and more particularly relates to a power transmission line fault positioning method based on traveling wave frequency.
Background
At present, a fault locating method of a power transmission line based on fault traveling waves, particularly fault traveling wave frequency, has been widely used. When traveling waves are transmitted on the transmission line, due to loss of the line and refraction and reflection phenomena 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 location based on the traveling wave frequency at the bus is reduced, and the overhaul and recovery of faults are affected.
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 are used for correcting the traveling wave frequency through a loop iteration method and improving fault positioning accuracy.
In order to achieve the above purpose, the power transmission line fault positioning method provided by the invention is realized by adopting the following technical scheme:
the utility model provides a transmission line fault location method based on travelling wave frequency, which is characterized in that the method comprises the following steps:
the frequency spectrum of an original current traveling wave head at each end of the line is respectively obtained, and the frequency spectrum is corrected by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
acquiring the arrival time of the traveling wave head at each end of the line respectively, and 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;
according to the frequency dependent characteristic and the traveling wave head frequency of each end of the line, determining the traveling wave speed of each end of the line;
determining a fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
correcting the frequency spectrum by adopting a cyclic iteration method to obtain a corrected traveling wave head frequency spectrum of each end of the line, wherein the method comprises the following steps:
(a) Calculating the correction current for the nth iteration
n is the iteration number;for the correction spectrum obtained in the nth iteration, define +.>To correct the frequency spectrum->A corresponding correction current; />The system impedance and the line wave impedance at the nth iteration are respectively according to +.>Determining; i.e bus (f bus ) Is the original current traveling wave head, f bus The frequency spectrum of the original current traveling wave head;
(b) Based on correction currentObtain the corresponding correction spectrum->
(c) Calculating the spectral error of the nth iteration
(d) Let n=n+1;
(e) Judging whether or not to meetOr N > N 1 If so, the cycle is ended and the +.>Determining the frequency spectrum of the corrected traveling wave head; otherwise, returning to (a); Δf thr Is a preset error threshold value, N 1 Is the preset maximum iteration number.
In order to achieve the purpose of the invention, the power transmission line fault positioning device provided by the invention is realized by adopting the following technical scheme:
a transmission line fault locating 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, correcting the frequency spectrum by adopting a cyclic iteration method, and acquiring 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 speed acquisition unit is used for 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;
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 is 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 invention also provides an electronic device comprising:
a memory in which a computer program is stored;
and the processor is configured to execute the computer program in the memory to realize the transmission line fault positioning method based on the travelling wave frequency.
Compared with the prior art, the invention has the advantages and positive effects that:
according to the power transmission line fault positioning method and the power transmission line fault positioning device based on the traveling wave frequency, the current traveling wave frequency spectrum is corrected by adopting the loop iteration method, the distorted traveling wave frequency obtained at the bus is recovered to the original traveling wave frequency, then the fault positioning is carried out based on the corrected frequency and the frequency-dependent characteristic, the fault positioning accuracy is improved, and the overhaul recovery speed of the power transmission line fault is further improved.
Other features and advantages of the present invention will become apparent upon review of the detailed description of the invention in conjunction with the drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of one embodiment of a method for locating a fault of a transmission line based on traveling wave frequency according to the present invention;
fig. 2 is a schematic structural diagram of an embodiment of a fault location device for a power transmission line based on traveling wave frequency according to the present invention;
FIG. 3 is a schematic diagram of the architecture of one 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 when the power transmission system of the embodiment of FIG. 4 fails;
fig. 6 is a spectrum diagram of the two terminals when the power transmission system of the embodiment of fig. 4 fails.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples.
In the prior art, when the fault of the transmission line is located based on the traveling wave frequency, the traveling wave has loss when transmitted on the transmission line, refraction and reflection are generated when the traveling wave reaches the bus, so that the traveling wave frequency acquired at the bus is distorted, and the traveling wave frequency is different from the initial traveling wave frequency when the fault occurs. In order to solve the technical problem, the invention creatively proposes to correct the traveling wave frequency acquired at the bus to recover 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 fault location method for a power transmission line based on a traveling wave frequency of the present invention, specifically, a schematic flow chart of an embodiment of fault location based on traveling wave frequency correction.
As shown in fig. 1, this embodiment implements transmission line fault location using the following procedure.
Step 11: the frequency spectrum of the original current traveling wave head at each end of the line is obtained respectively, and the frequency spectrum is corrected by adopting a cyclic iteration method, so that the corrected traveling wave head frequency spectrum at each end of the line is obtained.
In order to be able to determine the transmission speed of the traveling wave from the frequency, it is necessary to acquire the traveling wave head frequency, which can be determined from the frequency spectrum of the current traveling wave head. In this embodiment, the spectrum of the original current traveling wave head at each end of the line is first acquired. 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 spectrum of the original current traveling wave head may be calculated using HHT (hilbert-yellow transform) method based on the original current traveling wave head. The specific implementation of calculating the spectrum using HHT may be done using prior art techniques and will not be described in further detail herein.
In other embodiments, the S-transform approach may also be used to obtain the desired spectrum.
As described 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, the embodiment corrects the spectrum of the original current traveling wave head by adopting a cyclic iteration method, and obtains the corrected traveling wave head spectrum at each end of the line.
The specific correction method is realized by the following steps:
setting the iteration number N and setting the iteration number upper limit N 1 I.e. maximum number of iterations, e.g. set N 1 ＝10。
(a) Calculating the correction current for the nth iteration
Wherein n is the iteration number, starting from 1;for the correction spectrum obtained in the nth iteration, define +.>i bus (f bus ) The primary current traveling wave head can be directly detected and obtained; f (f) bus For the spectrum of the original current traveling wave head, according to i bus (f bus ) Can be directly calculated; />To correct the frequency spectrum->A corresponding correction current;the system impedance and the line wave impedance at the nth iteration are the intrinsic parameters of the power transmission system, are related to the structural parameters and the traveling wave frequency of the power transmission system, and can be changed according to the following traveling wave frequency change for a fixed power transmission system>The calculation determination is carried out, and the specific determination method is the prior art.
(b) Based on correction currentObtain the corresponding correction spectrum->In particular, it is preferable to correct the currentCalculating to obtain corresponding correction frequency spectrum +.>In other embodiments, the corresponding spectrum may also be obtained using an S-transform approach.
(c) Calculating the spectral error of the nth iteration
(d) Let n=n+1.
(e) Judging whether or not to meetOr N > N 1 If so, the cycle is ended and the +.>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 a fault occurs; otherwise, returning to (a), and continuing iteration. Wherein Δf thr Is a preset error threshold.
Step 12: the arrival time of the traveling wave head at each end of the line is obtained respectively, and the traveling wave head frequency corresponding to the arrival time of the traveling wave head at each end of the line is determined according to the corrected traveling wave head frequency spectrum at each end of the line.
The arrival time of the fault traveling wave head can be obtained by adopting the prior art. As 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 x max 。
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 moment t, and is a known value, and after the fault traveling wave signal selects a good modulus, the corresponding instantaneous value is the fault traveling wave amplitude. X is x max The peak value of the fault traveling wave amplitude in the data window is also a known value. c is a known proportionality coefficient, 0 < c < 1. In one specific embodiment, c=0.5.
By adopting the mode, the arrival time of the traveling wave head at each end of the line is determined, 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 and the traveling wave head frequency of each end of the line.
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 following method is used to determine the frequency dependent characteristics of the transmission line:
calculating complex penetration depth
Wherein ρ is earth resistivity, μ is vacuum permeability, both are known values, j is imaginary unit, and f is traveling wave frequency. For earth resistivity, different soils, rocks, etc. have different resistivities, and a typical approximation can be taken, for example, ρ=100 Ω m. In one embodiment, the vacuum permeability takes on the value μ=4pi×10 -7 H/m。
Calculating the self-impedance coefficient Z of A, B, C three-phase conductor 1(1) 、Z 1(2) And Z 1(3) ：
Wherein R is 1(1) 、R 1(2) And R is 1(3) A, B, C three-phase lead direct current resistance per unit length, h 1(1) 、h 1(2) And h 1(3) The heights of the ABC three-phase wires and the ground are respectively, and GMR 1(1) 、GMR 1(2) And GMR 1(3) The equivalent radius of the ABC three-phase wires is respectively, b is the splitting number of the split sub-wires, r is the radius of the split sub-wires, and d is the spacing of the split sub-wires. The values of the parameters are all known values and are determined by the parameters of the circuit structure, the electrical parameters and the like.
Calculating the transimpedance coefficient Z between A, B, C three-phase conductors 2(1-2) 、Z 2(2-1) 、Z 2(1-3) 、Z 2(3-1) 、Z 2(2-3) 、Z 2(3-2) ：
Wherein Z is 2(1-2) 、Z 2(2-1) 、Z 2(1-3) 、Z 2(3-1) 、Z 2(2-3) 、Z 2(3-2) Respectively the mutual impedance coefficients of the A phase wire and the B phase wire, the B phase wire and the A phase wire, the A phase wire and the C phase wire, the C phase wire and the A phase wire, the B phase wire and the C phase wire, the C phase wire and the B phase wire, d 2(1-2) ＝d 2(2-1) 、d 2(1-3) ＝d 2(3-1) 、d 2(2-3) ＝d 2(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, D 2(1-2) Is A phase conductorSpacing between mirror images of phase B conductors, D 2(2-1) D is the distance between the mirror images of the B phase wire and the A phase wire 2(1-3) D is the distance between the mirror images of the A phase wire and the C phase wire 2(3-1) D is the distance between the mirror images of the C phase wire and the A phase wire 2(2-3) D is the distance between the mirror images of the B phase wire and the C phase wire 2(3-2) Is the spacing between the mirror images of the C-phase conductors and the B-phase conductors. After the line is determined, each distance is a known value
Further description: z is Z 2(1-2) The trans-impedance coefficient between the A-phase wire and the B-phase wire refers to the trans-impedance coefficient between the A-phase wire and the B-phase wire based on the position of the A-phase wire; z is Z 2(2-1) The trans-impedance coefficient between the B-phase wire and the A-phase wire refers to the trans-impedance coefficient between the A-phase wire and the B-phase wire based on the position of the B-phase wire. D (D) 2(1-2) The distance between the mirror images of the A phase wire and the B phase wire refers to the distance between the mirror images of the A phase wire and the B phase wire. The same is true of the meaning of the remaining parameters.
Calculating self-impedance coefficient Z of lightning conductor 3(1) 、Z 3(2) ：
Wherein Z is 3(1) And Z 3(2) The self-impedance coefficient of the first lightning conductor and the self-impedance coefficient of the second lightning conductor are respectively R 3(1) And R is 3(2) The first lightning conductor unit length direct current resistor and the second lightning conductor unit length direct current resistor are respectively, h 3(1) And h 3(2) The heights of the first lightning conductor and the second lightning conductor from the ground are respectively GMR 3(1) And GMR 3(2) The equivalent radius of the first lightning conductor and the equivalent radius of the second lightning conductor are respectively. After the line is determined, R 3(1) 、R 3(2) 、h 3(1) 、h 3(2) GMR (GMR) device 3(1) 、GMR 3(2) Are known values.
Calculating the transimpedance coefficient Z between the conductor and the lightning conductor 4(1-1) 、Z 4(1-2) 、Z 4(1-3) 、Z 4(2-1) 、Z 4(2-2) 、Z 4(2-3) ：
Wherein Z is 4(1-1) 、Z 4(1-2) 、Z 4(1-3) 、Z 4(2-1) 、Z 4(2-2) 、Z 4(2-3) The mutual impedance coefficients are respectively between the first lightning conductor and the A-phase lead, between the first lightning conductor and the B-phase lead, between the first lightning conductor and the C-phase lead, between the second lightning conductor and the A-phase lead, between the second lightning conductor and the B-phase lead, and between the second lightning conductor and the C-phase lead; d, d 4(1-1) 、d 4(1-2) 、d 4(1-3) 、d 4(2-1) 、d 4(2-2) 、d 4(2-3) The distances 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, between the second lightning conductor and the C-phase conductor, D 4(1-1) 、D 4(1-2) 、D 4(1-3) 、D 4(2-1) 、D 4(2-2) 、D 4(2-3) The intervals are respectively between the first lightning conductor and the A-phase lead mirror image, between the first lightning conductor and the B-phase lead mirror image, between the first lightning conductor and the C-phase lead mirror image, between the second lightning conductor and the A-phase lead mirror image, between the second lightning conductor and the B-phase lead mirror image and between the second lightning conductor and the C-phase lead mirror image. After the line determination, each of the pitches is a known value.
Calculating the transimpedance coefficient Z between lightning conductor and lightning conductor 5(1-2) 、Z 5(2-1) ：
Wherein Z is 5(1-2) 、Z 5(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; d, d 5(1-2) ＝d 5(2-1) D is the distance between the first lightning conductor and the second lightning conductor 5(1-2) D is the distance between the mirror images of the first lightning conductor and the second lightning conductor 5(2-1) Is the spacing between the second and first lightning conductor mirror images. After the line determination, each of the pitches is a known value.
Determining an impedance coefficient matrix Z:
wherein,
calculating the self potential coefficient P of A, B, C three phases 1(1) 、P 1(2) 、P 1(3) ：
Where ε is the vacuum dielectric constant and is a known value.
Calculating the mutual potential coefficient P between A, B, C three phases 2(1-2) 、P 2(2-1) 、P 2(1-3) 、P 2(3-1) 、P 2(2-3) 、P 2(3-2) ：
Wherein P is 2(1-2) 、P 2(2-1) 、P 2(1-3) 、P 2(3-1) 、P 2(2-3) 、P 2(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 self potential coefficient P of lightning conductor 3(1) 、P 3(2) ：
Wherein P is 3(1) And P 3(2) The self-potential coefficient of the first lightning conductor and the self-potential coefficient of the second lightning conductor are respectively.
Calculating the mutual potential coefficient P between the lead and the lightning conductor 4(1-1) 、P 4(1-2) 、P 4(1-3) 、P 4(2-1) 、P 4(2-2) 、P 4(2-3) ：
Wherein P is 4(1-1) 、P 4(1-2) 、P 4(1-3) 、P 4(2-1) 、P 4(2-2) 、P 4(2-3) The mutual potential coefficients are respectively 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 C-phase conductor.
Calculating the mutual potential coefficient P between lightning conductor and lightning conductor 5(1-2) 、P 5(2-1) ：
Wherein P is 5(1-2) 、P 5(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 transmission parameters gamma of the power transmission line according to the impedance coefficient matrix Z and the capacitance coefficient matrix Y:
wherein, alpha and beta are real numbers.
Finally, determining the frequency-dependent characteristic according to the transmission parameter gamma of the power transmission line:
where v is the traveling wave velocity and f is the frequency.
In the above-described frequency dependent characteristic, β is a known value, and after the frequency f is determined, the wave velocity corresponding to the frequency can be determined.
Specifically, the frequency f of the traveling wave head at each end of the line is obtained TWk The traveling wave velocity v at each end of the line can be determined k ：
Wherein f TWk The frequency of the traveling wave head at the side of the k-th end converter station is obtained by adopting the method in the step 12; v k The traveling wave velocity at the kth 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 may be done using prior art techniques.
In the preferred implementation mode, the distance between the fault point and one end of the offline is determined according to the traveling wave speed and the arrival time of the traveling wave head, so that the fault is positioned. Specifically, the fault location is calculated according to the following formula:
wherein l is the distance from fault to M end of line, v M And v N The traveling wave speeds of the line M end and the line N end are respectively t M And t N The arrival time of the traveling wave heads at the line M end and the line N end respectively; l is the total length of the transmission line between the line M end and the line N end, 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 loop iteration method, the distorted traveling wave frequency obtained at the bus is restored to the original traveling wave frequency, then the fault positioning is carried out based on the corrected frequency and the frequency-dependent characteristic, the fault positioning accuracy is improved, and the overhaul recovery speed of the power transmission line fault is further improved.
Fig. 2 is a schematic structural diagram of an embodiment of a fault location device for a power transmission line based on traveling wave frequency according to the present invention.
As shown in fig. 2, the device of this embodiment includes structural units, functions of the structural units, and connection relationships between the structural units, which are described in detail below.
The apparatus of this embodiment comprises:
the corrected traveling wave head spectrum obtaining unit 21 is configured to obtain a spectrum of an original current traveling wave head at each end of the line, correct the spectrum by using a loop iteration method, and obtain a corrected traveling wave head spectrum at each end of the line.
The traveling wave head arrival time acquisition unit 22 is configured to acquire arrival times of the 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.
The traveling wave velocity obtaining unit 24 is configured to determine the traveling wave velocity of each end of the line according to the frequency dependent characteristic of each end of the line and the traveling wave head frequency obtained by the traveling wave head frequency obtaining unit 23.
The fault location determining unit 25 is configured to determine a fault location according to the traveling wave velocity of each end of the line acquired by the traveling wave velocity 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 locating device of the embodiment runs corresponding software programs, and achieves fault locating of the power transmission line according to the process of the method embodiment of fig. 1 and the preferred method embodiment thereof, and achieves the same technical effects as the method embodiment.
The power transmission line fault positioning device is applied to a power transmission system, the power transmission system 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, 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 can be determined.
Fig. 3 shows a schematic structural diagram of an embodiment of the electronic device of the 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 to implement the transmission line fault locating 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, an M-terminal converter station and an N-terminal converter station, respectively, F being a fault point, and F being a typical fault occurring on the power transmission line between the two terminal buses. Z is Z SM 、Z SN System impedance at M-terminal and at terminal side, Z TM Is the line wave impedance between the fault point F and the M end, Z TN Line wave impedance i for fault point F and N end M 、i N The currents at the M-terminal and the N-terminal, respectively.
Fig. 5 is a simulated waveform of a double-ended current traveling wave when a typical fault occurs in the power transmission system of fig. 4. Wherein (a) is a traveling wave waveform at the fault point F, and i FM 、i FN The current traveling wave waveforms are respectively transmitted from the fault point F to the M end and the N end; (b) is a current traveling wave waveform at the double-ended bus.
Monitoring according to the fault positioning method, wherein the arrival time of the fault reaching the M end and the N end is respectively: t is t M ＝1.303s，t N ＝1.704s。
Fig. 6 is a spectrum diagram of a double ended power transmission system of fig. 4 when a typical fault occurs. Wherein (a) is the traveling wave spectrum at the fault point F, specifically F FM 、f FN The traveling wave spectrums transmitted to the M end and the N end from the fault point F are respectively; (b) Is the frequency spectrum f of the original current traveling wave head at the double-end bus M 、f N The frequency spectrums of the original current traveling wave heads at the M-end bus and the N-end bus are respectively; (c) Correcting the frequency spectrum of the traveling wave head at the position of the double-end bus, f M 、f N And the frequency spectrums of the traveling wave heads after correction are respectively at the M-end bus and the N-end bus.
Monitoring according to the fault locating method, wherein the monitoring is as follows:
the traveling wave head frequency of the fault point F propagating to the M end and the N end is F FM ＝f FN ＝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 f respectively M ＝143.8kHz、f N ＝156.5kHz。
After 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 f respectively M ＝101.6kHz、f N =110.4khz. The frequency obtained after correction is closer to the original traveling wave head frequency at the fault point.
Further calculation can obtain that the wave velocities of fault traveling waves at the M-end bus and the N-end bus are v respectively M ＝298.935km/ms、v M ＝298.965km/ms。
Based on the obtained traveling wave speed and the arrival time of the traveling wave head, when the total length of the transmission line between the M-end bus and the N-end bus is L=300 km, the distance from the fault point F to the M-end bus is l= 90.052km.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (8)
1. The utility model provides a transmission line fault location method based on travelling wave frequency, which is characterized in that the method comprises the following steps:
the frequency spectrum of an original current traveling wave head at each end of the line is respectively obtained, and the frequency spectrum is corrected by adopting a cyclic iteration method to obtain the corrected traveling wave head frequency spectrum at each end of the line;
acquiring the arrival time of the traveling wave head at each end of the line respectively, and 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;
according to the frequency dependent characteristic and the traveling wave head frequency of each end of the line, determining the traveling wave speed of each end of the line;
determining a fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
correcting the frequency spectrum by adopting a cyclic iteration method to obtain a corrected traveling wave head frequency spectrum of each end of the line, wherein the method comprises the following steps:
(a) Calculating the correction current for the nth iteration
n is the iteration number;for the correction spectrum obtained in the nth iteration, define +.> To correct the frequency spectrum->A corresponding correction current; />The system impedance and the line wave impedance at the nth iteration are respectively according to +.>Determining; i.e bus (f bus ) Is the original current traveling wave head, f bus The frequency spectrum of the original current traveling wave head;
(b) Based on correction currentObtain the corresponding correction spectrum->
(c) Calculating the spectral error of the nth iteration
(d) Let n=n+1;
(e) Judging whether or not to meetOr N > N 1 If so, the cycle is ended and the +.>Determining the frequency spectrum of the corrected traveling wave head; otherwise, returning to (a); Δf thr Is a preset error threshold value, N 1 Is the preset maximum iteration number.
2. The method for locating a fault in an electrical transmission line based on traveling wave frequency as claimed in claim 1, wherein,
the obtaining of the frequency spectrum of the original current traveling wave head at each end of the line specifically comprises the following steps: 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 conversion method;
the correction currentObtain the corresponding correction spectrum->The method specifically comprises the following steps: for the correction currentCalculating to obtain the corresponding correction frequency spectrum by adopting HHT conversion method>
3. The method for locating a fault of a power transmission line based on a traveling wave frequency according to claim 1, wherein obtaining the arrival time of a traveling wave head at each end of the line specifically comprises:
calculating and determining whether a first criterion is satisfied: x (t) > c x max ；
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 moment t and is a known value; x is x max The peak value of the traveling wave amplitude in the data window is a known value; c is a known proportionality coefficient, 0 < c < 1.
4. The method for locating a fault of a power transmission line based on a traveling wave frequency according to claim 1, wherein determining the fault location according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head specifically comprises:
the fault location is calculated according to the following formula:
wherein l is the distance from fault to M end of line, v M And v N The traveling wave speeds of the line M end and the line N end are respectively t M And t N The arrival time of the traveling wave heads at the line M end and the line N end respectively; l is the total length of the transmission line between the line M end and the line N end, and is a known value.
5. The method for locating a fault in an electric transmission line based on a traveling wave frequency according to any one of claims 1 to 4, wherein determining the traveling wave velocity 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 includes:
the frequency dependent characteristic is obtained by the following method:
calculating complex penetration depth
Wherein ρ is earth resistivity, μ is vacuum permeability, both are known values, j is imaginary unit, and f is traveling wave frequency;
calculating the self-impedance coefficient Z of A, B, C three-phase conductor 1(1) 、Z 1(2) And Z 1(3) ：
Wherein R is 1(1) 、R 1(2) And R is 1(3) A, B, C three-phase lead direct current resistance per unit length, h 1(1) 、h 1(2) And h 1(3) The heights of the ABC three-phase wires and the ground are respectively, and GMR 1(1) 、GMR 1(2) And GMR 1(3) The equivalent radius of the ABC three-phase wires is respectively, b is the splitting number of the split sub-wires, r is the radius of the split sub-wires, and d is the spacing of the split sub-wires;
calculating the transimpedance coefficient Z between A, B, C three-phase conductors 2(1-2) 、Z 2(2-1) 、Z 2(1-3) 、Z 2(3-1) 、Z 2(2-3) 、Z 2(3-2) ：
Wherein Z is 2(1-2) 、Z 2(2-1) 、Z 2(1-3) 、Z 2(3-1) 、Z 2(2-3) 、Z 2(3-2) Respectively the mutual impedance coefficients of the A phase wire and the B phase wire, the B phase wire and the A phase wire, the A phase wire and the C phase wire, the C phase wire and the A phase wire, the B phase wire and the C phase wire, the C phase wire and the B phase wire, d 2(1-2) ＝d 2(2-1) 、d 2(1-3) ＝d 2(3-1) 、d 2(2-3) ＝d 2(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, D 2(1-2) D is the distance between the mirror images of the A phase wire and the B phase wire 2(2-1) D is the distance between the mirror images of the B phase wire and the A phase wire 2(1-3) D is the distance between the mirror images of the A phase wire and the C phase wire 2(3-1) D is the distance between the mirror images of the C phase wire and the A phase wire 2(2-3) D is the distance between the mirror images of the B phase wire and the C phase wire 2(3-2) Is the spacing between the mirror images of the C phase conductors and the B phase conductors;
calculating self-impedance coefficient Z of lightning conductor 3(1) 、Z 3(2) ：
Wherein Z is 3(1) And Z 3(2) The self-impedance coefficient of the first lightning conductor and the self-impedance coefficient of the second lightning conductor are respectively R 3(1) And R is 3(2) The first lightning conductor unit length direct current resistor and the second lightning conductor unit length direct current resistor are respectively, h 3(1) And h 3(2) The heights of the first lightning conductor and the second lightning conductor from the ground are respectively GMR 3(1) And GMR 3(2) The equivalent radius of the first lightning conductor and the equivalent radius of the second lightning conductor are respectively;
calculating the transimpedance coefficient Z between the conductor and the lightning conductor 4(1-1) 、Z 4(1-2) 、Z 4(1-3) 、Z 4(2-1) 、Z 4(2-2) 、Z 4(2-3) ：
Wherein Z is 4(1-1) 、Z 4(1-2) 、Z 4(1-3) 、Z 4(2-1) 、Z 4(2-2) 、Z 4(2-3) The mutual impedance coefficients are respectively between the first lightning conductor and the A-phase lead, between the first lightning conductor and the B-phase lead, between the first lightning conductor and the C-phase lead, between the second lightning conductor and the A-phase lead, between the second lightning conductor and the B-phase lead, and between the second lightning conductor and the C-phase lead; d, d 4(1-1) 、d 4(1-2) 、d 4(1-3) 、d 4(2-1) 、d 4(2-2) 、d 4(2-3) The distances 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, between the second lightning conductor and the C-phase conductor, D 4(1-1) 、D 4(1-2) 、D 4(1-3) 、D 4(2-1) 、D 4(2-2) 、D 4(2-3) The intervals are respectively between the first lightning conductor and the phase A lead mirror image, between the first lightning conductor and the phase B lead mirror image, between the first lightning conductor and the phase C lead mirror image, between the second lightning conductor and the phase A lead mirror image, between the second lightning conductor and the phase B lead mirror image and between the second lightning conductor and the phase C lead mirror image;
calculating the mutual between lightning conductor and lightning conductorImpedance coefficient Z 5(1-2) 、Z 5(2-1) ：
Wherein Z is 5(1-2) 、Z 5(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; d, d 5(1-2) ＝d 5(2-1) D is the distance between the first lightning conductor and the second lightning conductor 5(1-2) D is the distance between the mirror images of the first lightning conductor and the second lightning conductor 5(2-1) A spacing between the second lightning conductor and the mirror image of the first lightning conductor;
determining an impedance coefficient matrix Z:
wherein,
calculating the self potential coefficient P of A, B, C three phases 1(1) 、P 1(2) 、P 1(3) ：
Wherein epsilon is the vacuum dielectric constant;
calculating the mutual potential coefficient P between A, B, C three phases 2(1-2) 、P 2(2-1) 、P 2(1-3) 、P 2(3-1) 、P 2(2-3) 、P 2(3-2) ：
Wherein P is 2(1-2) 、P 2(2-1) 、P 2(1-3) 、P 2(3-1) 、P 2(2-3) 、P 2(3-2) Mutual potential coefficients between the A-phase conductor and the B-phase conductor, between the B-phase conductor and the A-phase conductor, between the A-phase conductor and the C-phase conductor, between the C-phase conductor and the A-phase conductor, between the B-phase conductor and the C-phase conductor, and between the C-phase conductor and the B-phase conductor, respectively;
calculating self potential coefficient P of lightning conductor 3(1) 、P 3(2) ：
Wherein P is 3(1) And P 3(2) The self-potential coefficient of the first lightning conductor and the self-potential coefficient of the second lightning conductor are respectively;
calculating the mutual potential coefficient P between the lead and the lightning conductor 4(1-1) 、P 4(1-2) 、P 4(1-3) 、P 4(2-1) 、P 4(2-2) 、P 4(2-3) ：
Wherein P is 4(1-1) 、P 4(1-2) 、P 4(1-3) 、P 4(2-1) 、P 4(2-2) 、P 4(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 conductorLei Xian and C-phase conductors;
calculating the mutual potential coefficient P between lightning conductor and lightning conductor 5(1-2) 、P 5(2-1) ：
Wherein P is 5(1-2) 、P 5(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;
determining a potential coefficient matrix P:
wherein,
determining a capacitance coefficient matrix Y:
Y＝j2πf×P -1 ；
determining transmission parameters gamma of the power transmission line according to the impedance coefficient matrix Z and the capacitance coefficient matrix Y:
wherein, 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 velocity and f is the frequency;
acquiring the traveling wave head frequency f of each end of the line TWk Determining the traveling wave velocity v of each end of the line k ：
Wherein f TWk Is the traveling wave head frequency of the kth end converter station side, v k The traveling wave velocity at the kth end converter station side.
6. A transmission line fault locating 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, correcting the frequency spectrum by adopting a cyclic iteration method, and acquiring 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 speed acquisition unit is used for 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;
the fault position determining unit is used for determining a fault position according to the traveling wave speed of each end of the line and the arrival time of the traveling wave head;
correcting the frequency spectrum by adopting a cyclic iteration method to obtain a corrected traveling wave head frequency spectrum of each end of the line, wherein the method comprises the following steps:
(a) Calculating the correction current for the nth iteration
n is the iteration number;for the correction spectrum obtained in the nth iteration, define +.> To correct the frequency spectrum->A corresponding correction current; />The system impedance and the line wave impedance at the nth iteration are respectively according to +.>Determining; i.e bus (f bus ) Is the original current traveling wave head, f bus The frequency spectrum of the original current traveling wave head;
(b) Based on correction currentObtain the corresponding correction spectrum->
(c) Calculating the spectral error of the nth iteration
(d) Let n=n+1;
(e) Judging whether or not to meetOr N > N 1 If so, the cycle is ended and the +.>Determining the frequency spectrum of the corrected traveling wave head; otherwise, returning to (a); Δf thr Is a preset error threshold value, N 1 Is the preset maximum iteration number.
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 by the power transmission line, characterized in that the power transmission system further comprises a power transmission line fault locating device based on travelling wave frequency as claimed in claim 6.
8. An electronic device, the electronic device comprising:
a memory in which a computer program is stored;
a processor configured to execute the computer program in the memory to implement the travelling wave frequency based transmission line fault location method of any one of the preceding claims 1 to 5.
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