CN108344923B - High-adaptability power transmission line fault location method and system - Google Patents
High-adaptability power transmission line fault location method and system Download PDFInfo
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The invention provides a high-adaptability power transmission line fault location method and a system, comprising the following steps: extracting three-phase current after the power transmission line fails, and carrying out modulus transformation on the three-phase current to obtain line modulus; carrying out multi-scale transformation on the modulus of the lines and positioning fault initial moments at two ends of the power transmission line; calculating time delay according to fault initial moments of two ends of the power transmission line; determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay; identifying fault point reflected waves and/or busbar reflected waves according to forward cross-correlation sequences and reverse cross-correlation sequences at two ends of the power transmission line; and carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave. According to the technical scheme provided by the invention, the success rate of identifying fault points/bus reflected waves is improved through the time-frequency correlation of data at two ends of the line, the length of the line and the time service error are corrected on the basis, and the adaptability and the accuracy of fault distance measurement are improved.
Description
Technical Field
The invention belongs to the field of power transmission line fault location, and particularly relates to a high-adaptability power transmission line fault location method and system.
Background
After the power transmission line breaks down, no matter whether the lines are successfully overlapped or not, line inspection personnel are required to find out fault points, and whether power failure maintenance is required to eliminate hidden danger or not is judged according to the damage degree caused by the faults, so that accurate positioning (commonly also called fault ranging) of the fault points of the power transmission line is an important link for guaranteeing the safety of a power grid. The fault distance measurement of the existing transmission line according to different principles can be divided into: impedance methods, traveling wave methods, fault analysis methods, and the like. Since the 90 s of the last century, the transmission line fault distance measuring device based on the traveling wave principle is widely applied to domestic power systems, and practical operation experience shows that: compared with an impedance method, a fault analysis method and the like, the traveling wave fault location well meets the user requirements in terms of precision and reliability.
According to the difference of the electric quantity, the traveling wave fault location is divided into a single-ended method, a double-ended method, a pulse method and the like, and the basic double-ended method is practically applied on site. The double-end method utilizes an initial traveling wave signal generated by faults, calculates the fault position by calculating the time difference between the initial traveling wave of the faults and the two ends of a line, and calculates the fault distance l according to the following method 1 ：
In the above formula; t is t 1 、t 2 The absolute time of the traveling wave reaching the two ends of the line is respectively, L is the total length of the line, and v is the traveling wave propagation speed. The double-end traveling wave method has the characteristics of simple and reliable principle, but the following factors influencing the ranging accuracy exist in actual engineering: (1) error of two-end time service device: a timing error of 1us would result in a range error of about 150 m. For a put-into-operation device, the time service errors at two ends are one of the most main reasons of failure of the fault distance measurement, and the fault distance measurement failure cases caused by the time service errors are close to 30%. In addition, in actual engineering, when two ends of a line adopt different time service manufacturer systems, fixed time service errors of several microseconds often exist in the devices at the two ends. In the direct current transmission engineering, during the artificial short circuit test, the two-side time service device has a fixed time service error of about 3us, and the fixed distance measurement error of about 400 meters can be caused. (2) line length error: a line error of 1km length may result in a fixed ranging error of about 0.5 km. In actual engineering, the field situation is complex, the design and operation units often estimate the line length according to the geographic position, the construction units generally calculate the line length according to consumable materials, and the two often have differences. In addition, sag differences due to seasonal temperature variations can also affect the line length. For example, in a direct current transmission project with a length of approximately 600km, the difference between the actual measured line length and the design length of a construction unit may reach 4km, sometimes even 20km, which has a great influence on the ranging accuracy, and in general, the difference between the two is within 3%. (3) line structure errors: line structure errors can affect the wave speed setting of the fault distance measuring device. In the construction of power grids in some places, the situation of the existing line reconstruction and expansion is common, and in the reconstruction and expansion process, a line single loop is often changed into a double loop to change the line structure. In the conventional traveling wave ranging method, the wave speed is often estimated according to a line structure, and the wave speed is changed due to the change of the line structure, so that additional errors are generated. Taking 220kV line as an example, a single loop line and a double loop line have a speed error of about 3%, the influence of wave speed on distance measurement accuracy is related to the position of a fault point and the length of the line, and when the fault point is positioned at two ends of the line, the influence of wave speed error is maximized, and the line is 100km For example, the limit impact is around 1.5 km. (4) in-station signal cable length error: similar to transient traveling wave transmission on the line, the CT/PT secondary side signal also has a time delay during the transmission of the signal cable in the station. The early fault distance measuring devices are all installed in the secondary cell in the station, the time delay of signals at two sides is close, and the influence on the distance measuring precision is small. With the development of the on-site secondary device, part of the line side device is installed in the secondary cell, the opposite side device is installed on-site, the secondary signal transmission delay influences the ranging precision, and the signal cable transmission delay of about 300m is about 2us, so that an extra 300m ranging error can be caused.
The single-ended traveling wave method for completing fault location by utilizing the time difference between the initial traveling wave and the reflected wave of the fault point/opposite terminal bus is theoretically not influenced by the length error of the line, the time service device and the cable in the station. Therefore, some researchers propose to use single-ended traveling wave method and double-ended method to reduce the influence of the above factors, but the problem of identifying reflected waves needs to be solved, and the following difficulties are mainly faced in practical application: (1) In theory, the success rate of reflected wave identification can be improved by windowing by a double-end method, but in actual fault analysis, the time window width is difficult to set, and the signal itself resonates so that the problem of reflected wave identification is difficult to solve by single windowing. In addition, due to the influence of factors such as time service errors and the like of double-end accuracy, the auxiliary time window cannot improve the success rate of reflected wave identification. (2) With the increasing number of power grid lines, the problem of interference of reflected waves between lines adjacent to the bus is also solved, and the polarity of the reflected waves between lines adjacent to the bus is the same as that of the reflected waves at the fault point, so that the difficulty of identifying the reflected waves is further increased. (3) wave velocity calculation: when the fault point far away from the measuring end is positioned, compared with the double-end traveling wave method, the transmission distance of the fault point/bus reflected wave in the single-end traveling wave method is longer, so that the influence of the wave speed error is further enlarged.
In view of the above-mentioned deficiency, in the actual fault analysis of single-ended travelling wave method, rely on the supplementary bi-polar method of traditional single-ended to correct the length, disadvantage in the time service error technology, still rely on the engineering personnel to finish manually.
Disclosure of Invention
The invention discloses a high-adaptability power transmission line fault location method based on time-frequency correlation of signals at two ends.
The invention provides a high-adaptability power transmission line fault location method, which comprises the following steps:
extracting three-phase current after the power transmission line fails, and carrying out modulus transformation on the three-phase current to obtain line modulus;
performing multi-scale transformation on the line modulus, and positioning fault initial moments at two ends of the power transmission line;
calculating time delay according to the fault initial moments of the two ends of the power transmission line;
determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
and carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave.
The method for extracting the three-phase current after the power transmission line fault, and carrying out modulus transformation on the three-phase current to obtain line modulus comprises the following steps:
And carrying out modulus transformation on the three-phase current according to the following formula, and transforming the three-phase current into linear modulus:
wherein I is a 、I b 、I c Is three-phase current; i α Alpha modulus, I, for three-phase current β Beta modulus, I, of a three-phase current 0 Zero modulus for three phase current.
The multi-scale transformation is carried out on the modulus of the lines, and the fault initial time at the two ends of the power transmission line is positioned, comprising the following steps:
carrying out multi-scale transformation on the line modulus by using a binary wavelet, and decomposing the line modulus into an approximate coefficient and a detail coefficient by using the wavelet transformation according to the wavelet transformation scale;
selecting a frequency band with the maximum transient amplitude at two ends of a line for analysis by taking the amplitude mean value of the detail coefficient of the wavelet transformation as a standard;
extracting wavelet transformation detail coefficients of the selected frequency band, and calculating a modular maximum value sequence;
and positioning the fault initial time according to the module maximum value sequence.
Calculating time delay according to the following equation at the fault initial time of the two ends of the power transmission line:
Δt＝t m -t n
wherein Deltat is the time delay, t m And t n The initial time of the fault at the two ends of the line.
And determining forward cross-correlation sequences at two ends of the power transmission line according to the wavelet transformation scale and the time delay following formula:
w(t)＝x m (t)×x n (t+Δt)
wherein w (t) is a forward cross-correlation sequence at two ends of the transmission line, and x m (t) and x n And (t) is the wavelet transformation coefficient at two ends of the power transmission line, and deltat is the time delay.
Determining a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay, wherein the method comprises the following steps:
and calculating analysis data of any one of the two ends of the power transmission line according to the following formula, and transposing the analysis data:
y(t 0 +i)＝x(t 0 +DL－i)
wherein dl=l/v×1/fs
Wherein y (t) is single-ended data of the transmission line after transposition, x (t) is single-ended data of the transmission line before transposition, t 0 I=1, 2..dl, DL is the time window, L is the line full length, v is the wave speed, f s Is the sampling frequency;
substituting the transposed single-ended data of the power transmission line and the non-transposed opposite-end data of the power transmission line into the following data to obtain a reverse cross-correlation sequence at two ends of the power transmission line:
w(t)'＝x m (t)×x n (t+Δt)
wherein w (t)' is a reverse cross-correlation sequence at two ends of the transmission line, and x m (t) and x n And (t) is the wavelet transformation coefficient at two ends of the power transmission line, and deltat is the time delay.
The identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at two ends of the power transmission line comprises the following steps:
and identifying fault point reflected waves and bus reflected waves according to the forward cross-correlation sequence, wherein the conditions comprise:
1) The fault point reflected wave and the bus reflected wave are reflected by negative polarity;
2) Amplitude A of fault point reflected wave and bus reflected wave f Meets the requirement of 0.01 xA is less than or equal to A f ≤0.25×β 1 ×β 2 X A, wherein A is the initial wave head amplitude, beta 1 、β 2 Bus reflection coefficients at two ends of the line respectively; and
3) The fault point reflected wave and the opposite fault point reflected wave satisfy the following equation:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L
wherein t 'is' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 The initial moment of the wave head is L the whole length of the line, and v the wave speed.
Identifying fault point reflected waves and/or bus reflected waves with a reverse cross-correlation sequence, comprising:
the fault point reflected wave or bus reflected wave can be only identified according to the backward cross correlation sequence identification, and the conditions comprise:
1) The fault point reflected wave or the bus reflected wave is reflected by negative polarity;
2) Amplitude A of fault point reflected wave or bus reflected wave f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A。
Performing fault ranging calculation according to the identified fault point reflected wave and the bus reflected wave, including:
if the fault point reflected wave and the bus reflected wave are identified at the same time, carrying out fault distance measurement calculation according to the following formula:
wherein d is the distance value obtained by testing, t' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the full length of the line at the initial moment of the wave head;
after the fault location calculation is completed, the identified reflected waves are respectively corresponding to the single-ended data mode maximum values according to the mode maximum value sequence, and the reflected waves are determined to be fault point reflected waves or bus reflected waves.
If only the fault point reflected wave or the bus reflected wave can be identified, the fault distance measurement calculation is performed according to the following formula:
d＝(t' 1 -t 0 )×v/2
after the fault distance measurement calculation is completed, the identified reflected wave corresponds to the single-end data mode maximum value according to the mode maximum value sequence, and the identified reflected wave is determined to be a fault point or an opposite-end bus reflected wave.
The invention provides a high-adaptability power transmission line fault location system, which comprises:
the extraction module is used for extracting three-phase current after the power transmission line faults and carrying out modulus transformation on the three-phase current to obtain line modulus;
the positioning module is used for carrying out multi-scale transformation on the line modulus and positioning fault initial moments at two ends of the power transmission line;
the calculation module is used for calculating time delay according to the fault initial moments of the two ends of the power transmission line;
the correlation sequence module is used for determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
The identification module is used for identifying fault point reflected waves and/or bus reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
and the distance measurement module is used for carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
according to the technical scheme provided by the invention, the success rate of identifying fault points/bus reflected waves is improved through the time-frequency correlation of data at two ends of the line, and the length of the line and the time service error are corrected on the basis, so that the adaptability and the accuracy of fault distance measurement are improved;
according to the technical scheme provided by the invention, fault location is performed by utilizing fault points and/or bus reflected waves, so that the influence of line length errors, time service errors, wave speed errors and in-station cables on the location accuracy is avoided, and the method can be used as a backup correction means under abnormal conditions such as GPS satellite loss and the like;
according to the technical scheme provided by the invention, clutter interference suppression is realized by utilizing the characteristics that the axial symmetry and waveform similarity of reflected waves at two ends are utilized, and interference amounts such as signal resonance, reflected waves of adjacent lines of the same bus and the like are not related to each other, and the forward and reverse cross correlation of two-pole signals is analyzed based on wavelet correlation, so that the most main reflected wave identification problem in single-ended traveling wave ranging is solved;
Compared with the existing single-end/double-end method combined method, the method provided by the invention is not affected by the double-end method ranging error, and the problem of time window width setting is not considered.
Drawings
Fig. 1 is a flow chart of a fault location method of a high-adaptability power transmission line;
fig. 2 is a schematic diagram of time axis symmetry of signals at two ends of a transmission line;
FIG. 3 is a schematic diagram showing delta and transition resistance variation trend in an embodiment of the present invention;
FIG. 4 is a schematic diagram of wavelet transformation at two ends of a circuit in a fourth embodiment of the present invention;
(a) A wavelet transformation coefficient diagram at two ends of a line is shown, and (b) a wavelet transformation mode maximum value sequence diagram at two ends of the line is shown;
FIG. 5 is a schematic diagram of a forward cross-correlation sequence of data at two ends of a circuit in a fourth embodiment of the present invention;
FIG. 6 is a schematic diagram of a reverse cross-correlation sequence of data at two ends of a circuit in a fourth embodiment of the present invention;
FIG. 7 is a schematic diagram of wavelet transformation at two ends of a circuit in a fifth embodiment of the present invention;
(a) A wavelet transformation coefficient diagram at two ends of a line is shown, and (b) a wavelet transformation mode maximum value sequence diagram at two ends of the line is shown;
FIG. 8 is a schematic diagram of a forward cross-correlation sequence of data at two ends of a circuit in a fifth embodiment of the present invention;
fig. 9 is a schematic diagram of a reverse cross-correlation sequence of data at two ends of a circuit in a fifth embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
embodiment 1,
Fig. 1 is a flowchart of a high-adaptability power transmission line fault location method provided by the invention, and as shown in fig. 1, the high-adaptability power transmission line fault location method provided by the invention comprises the following steps:
extracting three-phase current after the power transmission line fails, and carrying out modulus transformation on the three-phase current to obtain line modulus;
performing multi-scale transformation on the line modulus, and positioning fault initial moments at two ends of the power transmission line;
calculating time delay according to the fault initial moments of the two ends of the power transmission line;
determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
and carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave.
The method for extracting the three-phase current after the power transmission line fault, and carrying out modulus transformation on the three-phase current to obtain line modulus comprises the following steps:
and carrying out modulus transformation on the three-phase current according to the following formula, and transforming the three-phase current into linear modulus:
Wherein I is a 、I b 、I c Is three-phase current; i α Alpha modulus, I, for three-phase current β Beta modulus, I, of a three-phase current 0 Zero modulus for three phase current.
The multi-scale transformation is carried out on the modulus of the lines, and the fault initial time at the two ends of the power transmission line is positioned, comprising the following steps:
carrying out multi-scale transformation on the line modulus by using a binary wavelet, and decomposing the line modulus into an approximate coefficient and a detail coefficient by using the wavelet transformation according to the wavelet transformation scale;
selecting a frequency band with the maximum transient amplitude at two ends of a line for analysis by taking the amplitude mean value of the detail coefficient of the wavelet transformation as a standard;
extracting wavelet transformation detail coefficients of the selected frequency band, and calculating a modular maximum value sequence;
and positioning the fault initial time according to the module maximum value sequence.
Calculating time delay according to the following equation at the fault initial time of the two ends of the power transmission line:
Δt＝t m -t n
wherein Deltat is the time delay, t m And t n The initial time of the fault at the two ends of the line.
And determining forward cross-correlation sequences at two ends of the power transmission line according to the wavelet transformation scale and the time delay following formula:
w(t)＝x m (t)×x n (t+Δt)
wherein w (t) is a forward cross-correlation sequence at two ends of the transmission line, and x m (t) and x n And (t) is the wavelet transformation coefficient at two ends of the power transmission line, and deltat is the time delay.
Determining a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay, wherein the method comprises the following steps:
and calculating analysis data of any one of the two ends of the power transmission line according to the following formula, and transposing the analysis data:
y(t 0 +i)＝x(t 0 +DL－i)
wherein dl=l/v×1/fs
Wherein y (t) is single-ended data of the transmission line after transposition, x (t) is single-ended data of the transmission line before transposition, t 0 I=1, 2..dl, DL is the time window, L is the line full length, v is the wave speed, f s Is the sampling frequency;
substituting the transposed single-ended data of the power transmission line and the non-transposed opposite-end data of the power transmission line into the following data to obtain a reverse cross-correlation sequence at two ends of the power transmission line:
w(t)'＝x m (t)×x n (t+Δt)
wherein w (t)' is a reverse cross-correlation sequence at two ends of the transmission line, and x m (t) and x n And (t) is the wavelet transformation coefficient at two ends of the power transmission line, and deltat is the time delay.
The identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at two ends of the power transmission line comprises the following steps:
and identifying fault point reflected waves and bus reflected waves according to the forward cross-correlation sequence, wherein the conditions comprise:
1) The fault point reflected wave and the bus reflected wave are reflected by negative polarity;
2) Amplitude A of fault point reflected wave and bus reflected wave f Meets the requirement of 0.01 xA is less than or equal to A f ≤0.25×β 1 ×β 2 X A, wherein A is the initial wave head amplitude, beta 1 、β 2 Bus reflection systems at two ends of the lineA number; and
3) The fault point reflected wave and the opposite fault point reflected wave satisfy the following equation:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L
wherein t 'is' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 The initial moment of the wave head is L the whole length of the line, and v the wave speed.
Identifying fault point reflected waves and/or bus reflected waves with a reverse cross-correlation sequence, comprising:
the fault point reflected wave or bus reflected wave can be only identified according to the backward cross correlation sequence identification, and the conditions comprise:
1) The fault point reflected wave or the bus reflected wave is reflected by negative polarity;
2) Amplitude A of fault point reflected wave or bus reflected wave f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A。
Performing fault ranging calculation according to the identified fault point reflected wave and the bus reflected wave, including:
if the fault point reflected wave and the bus reflected wave are identified at the same time, carrying out fault distance measurement calculation according to the following formula:
wherein d is the distance value obtained by testing, t' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the full length of the line at the initial moment of the wave head;
after the fault location calculation is completed, the identified reflected waves are respectively corresponding to the single-ended data mode maximum values according to the mode maximum value sequence, and the reflected waves are determined to be fault point reflected waves or bus reflected waves.
If only the fault point reflected wave or the bus reflected wave can be identified, the fault distance measurement calculation is performed according to the following formula:
d＝(t' 1 -t 0 )×v/2
after the fault distance measurement calculation is completed, the identified reflected wave corresponds to the single-end data mode maximum value according to the mode maximum value sequence, and the identified reflected wave is determined to be a fault point or an opposite-end bus reflected wave.
Embodiment II,
Based on the same inventive concept, the invention provides a high-adaptability power transmission line fault location system, which can comprise:
the extraction module is used for extracting three-phase current after the power transmission line faults and carrying out modulus transformation on the three-phase current to obtain line modulus;
the positioning module is used for carrying out multi-scale transformation on the line modulus and positioning fault initial moments at two ends of the power transmission line;
the calculation module is used for calculating time delay according to the fault initial moments of the two ends of the power transmission line;
the correlation sequence module is used for determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
the identification module is used for identifying fault point reflected waves and/or bus reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
and the distance measurement module is used for carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave.
The method for extracting the three-phase current after the power transmission line fault, and carrying out modulus transformation on the three-phase current to obtain line modulus comprises the following steps:
carrying out modulus transformation on the three-phase current to obtain linear modulus;
modulus transformation was performed as follows:
wherein I is a 、I b 、I c Is three-phase current; i α Alpha modulus, I, for three-phase current β Beta modulus, I, of a three-phase current 0 Zero modulus for three phase current.
The multi-scale transformation is carried out on the modulus of the line, and the fault initial time at two ends of the line is positioned, comprising the following steps:
carrying out multi-scale transformation on the line modulus by using a binary wavelet, and decomposing the line modulus into an approximate coefficient and a detail coefficient by using the wavelet transformation according to the wavelet transformation scale;
selecting a frequency band with the largest transient amplitude at two ends of a line for analysis by taking the amplitude mean value of the detail coefficient of wavelet transformation as a standard;
extracting wavelet transformation detail coefficients of the selected frequency band, and calculating a modular maximum value sequence;
and positioning the fault initial time according to the module maximum value sequence.
Calculating time delay according to the following formula at the initial time of faults at two ends of a line:
Δt＝t m -t n
wherein t is m And t n The initial time of the fault at the two ends of the line.
Obtaining forward cross-correlation sequences at two ends of the line according to the wavelet transformation scale and the time delay, wherein the forward cross-correlation sequences comprise:
The forward cross-correlation sequence at both ends of the line is calculated as follows:
w(t)＝x m (t)×x n (t+Δt)
wherein w (t) is the forward cross-correlation sequence at two ends of the line, and x m (t) and x n And (t) is the wavelet transform coefficient at two ends of the line, and deltat is the time delay.
Obtaining a reverse cross-correlation sequence at two ends of the line according to the wavelet transformation scale and the time delay, wherein the reverse cross-correlation sequence comprises the following steps:
the analytical data at either end of the line is transposed as calculated:
y(t 0 +i)＝x(t 0 +DL－i)
wherein dl=l/v×1/fs
Wherein y (t) is single-ended data after transposition, x (t) is single-ended data before transposition, t 0 I=1, 2..dl, DL is the time window, L is the line full length, v is the wave speed, f s Is the sampling frequency;
substituting the transposed single-ended data and the non-transposed line opposite-end data into the following formula to obtain a reverse cross-correlation sequence at two ends of the line:
w(t)'＝x m (t)×x n (t+Δt)
where w (t)' is the reverse cross-correlation sequence at both ends of the line, x m (t) and x n And (t) is the wavelet transform coefficient at two ends of the line, and deltat is the time delay.
The method for identifying fault point reflected waves and/or bus reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at two ends of the line comprises the following steps:
identifying fault point reflected waves and bus reflected waves according to the forward cross-correlation sequence, wherein the following conditions are satisfied:
The fault point reflected wave and the bus reflected wave are reflected by negative polarity;
amplitude A of fault point reflected wave and bus reflected wave f Meets the requirement of 0.01 xA is less than or equal to A f ≤0.25×β 1 ×β 2 X A, wherein A is the initial wave head amplitude, beta 1 、β 2 Bus reflection coefficients at two ends of the line respectively;
the fault point reflected wave and the opposite fault point reflected wave satisfy the following equation:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L
wherein t 'is' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the whole length of the line at the initial moment of the wave head, and v is the wave speed;
if the fault point reflected wave and the bus reflected wave which meet the conditions cannot be identified according to the forward cross-correlation sequence, the backward cross-correlation sequence is used for further identification.
Further identifying fault point reflected waves and/or busbar reflected waves using the reverse cross-correlation sequence, comprising:
according to the backward cross correlation sequence identification, only fault point reflected waves or bus reflected waves can be identified, and the following conditions are required to be met:
the fault point reflected wave or the bus reflected wave is reflected by negative polarity;
amplitude A of fault point reflected wave or bus reflected wave f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A。
Performing fault ranging calculation according to the identified fault point reflected wave and the bus reflected wave, including:
if the fault point reflected wave and the bus reflected wave are identified at the same time, carrying out fault distance measurement calculation according to the following formula:
Wherein d is the distance value obtained by testing, t' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the full length of the line at the initial moment of the wave head;
after the fault location calculation is completed, the identified reflected waves are respectively corresponding to the single-ended data mode maximum values according to the mode maximum value sequence, and the reflected waves are determined to be fault point reflected waves or bus reflected waves.
If only the fault point reflected wave or the bus reflected wave can be identified, the fault distance measurement calculation is performed according to the following formula:
d＝(t' 1 -t 0 )×v/2
after the fault distance measurement calculation is completed, the identified reflected wave corresponds to the single-end data mode maximum value according to the mode maximum value sequence, and the identified reflected wave is determined to be a fault point or an opposite-end bus reflected wave.
Third embodiment,
The invention discloses a high-adaptability power transmission line fault location method based on time-frequency correlation of signals at two ends. Because the fault point/bus reflected wave is irrelevant to the length of the line, the time service device and the signal cable in the station, and the influence of the wave speed error on the ranging precision is reduced by selecting the reflected wave with a shorter transmission distance to finish ranging, the high-adaptability power transmission line fault ranging method focuses on solving the reliable identification of the fault point/bus reflected wave.
The main interference factors in the reflected wave identification of the conventional single-ended traveling wave method are as follows:
1) If the signal resonance is caused by bus end equipment, obvious difference exists between resonance waveforms at two ends of the line and the resonance waveforms are not related to each other; if the resonance is caused by resonance of the fault point equivalent power supply and the line parameters, the resonance waveforms of the signals at the two ends are similar and have the same polarity, so that the problem of the single-ended traveling wave method is to be solved;
2) The reflected waves of the adjacent lines of the same bus are only related to the bus on the side, and the interference amounts in transient traveling wave signals acquired by two ends of the line are not related to each other;
3) Clutter interference caused by actions of power electronic equipment and in-station relays is also uncorrelated with the interference in signals at two ends of a line;
compared with clutter interference, the catadioptric wave generated when the transient traveling wave generated by the power transmission line fault reaches each impedance discontinuity point has time axis symmetry and waveform correlation, as shown in figure 2. The fault point reflected wave at the two ends (M, N ends for short) of the line is axisymmetric and similar in waveform when the fault point reflected wave at the M end is similar to the fault point reflected wave at the N end when the fault point reflected wave at the opposite end is the same as the fault point reflected wave at the N end.
The invention improves the success rate of identifying fault points/bus reflected waves through the time-frequency correlation of the data at the two ends of the line, corrects the length of the line and the time service error on the basis of the success rate, and further improves the adaptability and the accuracy of fault distance measurement.
The invention provides a power transmission line fault location method, which specifically comprises the following steps:
step 1 modulus transformation
When the transmission line fails, the three-phase currents of the non-fault level and the fault level after the fault are extracted, and the three-phase currents are converted into line moduli and then analyzed so as to eliminate the influence of mode mixing. Adopting symmetrical component phase-mode transformation, and selecting alpha modulus as main analysis line mode component, the transformation matrix is as follows:
step 2 wavelet transformation and fault initial time positioning
The invention adopts binary wavelet to carry out multi-scale transformation on the line modulus obtained in the step 1, takes the amplitude mean value of wavelet transformation detail coefficients as a standard, and selects frequency bands (corresponding to analysis scales) with obvious transient characteristics at two ends of a line for analysis.
The wavelet transform includes:
at a given analysis scale a, the wavelet transform decomposes the signal into approximation coefficients (low frequency part) and detail coefficients (high frequency part), as follows.
y(i)＝l(i)+d(i)(2)
In equation 2, d (i) (i=0, 1, once again n) is a detail coefficient, the detail coefficient has better time resolution and is suitable for calculating the fault initial time. The invention adopts wavelet transformation mode maximum value method to identify the fault initial time, and the steps are as follows:
(1) Extracting wavelet transformation detail coefficient d (i) and calculating a modular maximum value sequence;
(2) Positioning the fault initial time according to a mode maximum value method;
the initial moments of the two ends of the line can be obtained by a wavelet mode maximum method respectively as follows: t is t m 、t n Because the two ends of the line are not synchronously sampled, there is generally a time delay between the initial moments of the two end measurements: Δt=t m -t n 。
Step 3 forward translation compensation and cross correlation sequence calculation
When the data at two ends of the power transmission line are regarded as two independent signals, the calculation formula of the wavelet cross-correlation sequence is as follows under the given wavelet transformation scale a and time delay delta t:
w(t)＝x m (t)×x n (t+Δt) (3)
in the above, x m (t) and respectively x n And (t) is a wavelet transformation coefficient of an M end and an N end, if the M end data is taken as a reference, delay compensation is needed to be realized on the shift delta t of the wavelet transformation coefficient of the N end signal, and a forward cross-correlation sequence of signals at two ends can be obtained based on a formula 3.
In the forward cross-correlation sequence of the signals at both ends, since the fault point reflected wave is positive and the bus reflected wave at the opposite end of the line is negative, both the fault point reflected wave and the bus reflected wave are negative in the cross-correlation sequence
Step 4 reverse translation compensation and cross correlation sequence calculation
Similarly to step 3, when the data at two ends of the transmission line are regarded as two independent signals, the same type of reflected waves in the signals at two ends are axially reversed and have similar waveforms, so that the M or N end single-ended data can be transposed:
y(t 0 +i)＝x(t 0 +DL－i)(4)
Wherein y (t) is single-ended data after transposition, t 0 Dl=l/v×1/fs, i=1, 2..dl, DL is the time window, the window size is defined by the line full length L, wave velocity v and sampling frequency f, for the initial moment of the wave head s And (5) determining. Substituting y (t) and line opposite end data x (t) into formula 3 to obtain a reverse cross-correlation sequence of the two-end data.
Step 5 reflected wave identification
The interference sources in the conventional single-ended traveling wave method include: the reflected wave, bus equipment and signal resonance interference of the adjacent lines of the same bus are characterized in that in the cross-correlation sequence, the interference quantity is as follows:
1) The reflected waves of the adjacent lines of the same bus and the interference signals caused by the resonance of bus equipment are mutually uncorrelated, so that the interference signals are restrained in a cross-correlation sequence;
2) In the forward cross-correlation sequence, interference signals caused by resonance of signals at two ends are relatively enhanced, the amplitude is generally higher, and the waveforms are similar and time axis symmetry are positive-polarity reflections; in the reverse cross correlation sequence, the resonance signal is asymmetric, and thus, there is theoretically no interference caused by signal resonance.
In the forward cross correlation sequence, fault points and bus reflected waves are identified according to the following three points:
1) The fault point reflected wave and the bus reflected wave are both reflected with negative polarity.
2) Assuming an initial wave head amplitude of A, the fault point/bus reflected wave amplitude should be approximately equal to A x alpha 0 ×β 0 ×β 1 ×β 2 Let delta be the failure point refractive index alpha 0 And bus refractive index beta 0 Product of beta 1 、β 2 The calculation formulas are shown as follows, wherein the calculation coefficients are M, N end bus reflection coefficients respectively:
β 1 ≈(n 1 －1)/(n 1 +1)β 2 ≈(n 2 －1)/(n 2 +1)(6)
wherein n is 1 、n 2 The number of adjacent lines of M, N ends and buses is equal to Z c1 R is the characteristic impedance of the power transmission line g Is a short-circuit transition resistance. In actual fault analysis, beta 1 、β 2 All are constant values, and the relation between delta and the transition resistance is shown as shown in figure 3, wherein delta is generally not more than 0.25. In order to avoid white noise interference, a lower threshold of 0.01 is set in the actual fault analysis, and white noise interference is considered when the amplitude is smaller than 0.01×a. To sum up the above factors, therefore, the fault point/bus reflected wave amplitude A f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 ×β 2 ×A。
3) The fault point reflected wave and the opposite bus reflected wave meet the constraint condition of line length-wave speed, and the moment of the fault point and bus reflected wave is assumed to be t' 1 、t' 2 Then theoretically t' 2 、t' 3 The conditions are satisfied: (t' 1 -t 0 )×v+(t' 2 -t 0 ) X v=l, but taking into account analytical scale, wave velocity, line error and the actual presence or absence ofMore than 3% error, the screening conditions are as follows:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L (7)
therefore, if two reflected waves can be screened out from the forward reflected wave sequence and the formula 7 is satisfied, the calculation in the step 6 can be directly performed. If the reflected wave combination meeting the above condition cannot be found, the backward cross-correlation sequence is used for further identification.
Compared with the forward mutual sequence, in the backward mutual correlation sequence, the fault points/buses at two ends of the line are positive in reflected wave, and the signal resonance interference approaches zero to facilitate the identification of the reflected wave, but the line length and the wave speed are sensitive, and when errors exist in the line length and the wave speed, the amplitude of the reflected wave is obviously reduced. Since the back cross correlation only identifies the fault point or busbar reflected wave, the reflected wave only needs to be identified according to the following two conditions:
1) The fault point reflected wave and the bus reflected wave are both reflected with negative polarity.
2) Fault point/busbar reflected wave amplitude a f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A。
And after the reflected wave identification is completed, entering a step 6 to complete single-end distance measurement.
Step 6 single-ended fault location
(1) If the fault point and the bus reflected wave are identified at the same time through the step 5, the condition is satisfied by considering the fault point and the bus reflected wave: (t' 1 -t 0 )×v+(t' 2 -t 0 ) X v=l, therefore, to avoid the effects of line length, wave speed errors, the conventional single-ended fault location formula can be modified to:
after the fault distance measurement calculation is completed, the reflected wave corresponds to the maximum value of the single-end data mode, and is determined to be the fault point or the reflected wave of the opposite-end bus.
(2) If only the fault point reflected wave or the bus reflected wave can be identified through the step 5, the fault point calculation is still completed according to the conventional single-ended traveling wave method, as shown in the following formula.
d＝(t' 1 -t 0 )×v/2 (9)
Also, the reflected wave is required to correspond to the single-ended data mode maximum value, and is determined as a fault point or an opposite-end bus reflected wave.
Fourth embodiment,
Analysis is carried out by taking Liaoning electric network 220kV Gangdan 1 line actual fault as an example
The Liaoning electric network has 220kV harbor Dan 1 line fault, and the full length of the line is about 55.48km. In the secondary fault, the fault distance measuring device operated on site gives out a fault result because the GPS loses the star at the first time, and the actual line inspection result is as follows: the fault point is about 16.919km from harbor city and about 38.5km from dandong, which is a typical single-phase earth fault.
Step 1: performing line mode conversion on three-phase current at fault moment;
step 2: wavelet transformation and fault initial moment calculation: the wavelet transform coefficients are obtained after decomposition of the modulus components using the selected spline wavelet and transform scale as shown in fig. 4 (a). The invention adopts a mode maximum value method to identify the fault initial time at two ends of a line, extracts the time delay delta t of the fault initial time, and as shown in fig. 4 (b), after the fault initial time, a large number of clutter interferences exist in the wavelet transformation mode maximum value, and the clutter can influence single-end ranging.
Step 3: forward translation compensation and cross correlation sequence calculation: after forward translation compensation of the data at two ends, the forward cross-correlation sequences at two ends extracted by wavelet transformation are shown in fig. 5, and the clutter interference is effectively inhibited relative to fig. 4 (b), and the circle part in fig. 5 is an actual fault point/line opposite-end busbar reflected wave and is reflected by negative polarity.
Step 4: reverse translation compensation and cross correlation sequence calculation: after the opposite-translation compensation of the two-end data, the opposite-end cross-correlation sequence extracted by wavelet transformation is shown in fig. 6, in which the circle part is the actual fault point and the opposite-end bus reflected wave of the line, and compared with the forward wavelet cross-correlation sequence, the fault point and the opposite-end bus reflected wave of the line are both positive-polarity reflections.
Step 5: and (3) reflected wave identification: firstly, the forward cross-correlation sequence is analyzed, and the reflected waves are screened according to the polarity and amplitude conditions, so that two reflected waves can be identified. The time difference between the two reflected waves and the initial traveling wave is respectively as follows: (t' 1 -t 0 )＝72，(t' 2 -t 0 ) =163, combined with 220kV double-circuit line wave speed of about 295m/us, satisfying the line length-wave speed constraint (t' 1 -t 0 )×v+(t' 2 -t 0 ) X v=l, the calculation can be completed by directly proceeding to step 6.
Step 6: single-ended traveling wave fault location: will (t' 1 -t 0 )，(t' 2 -t 0 ) Substituting formula 8, d=The calculated fault points are: 16.998km, which is 79m different from the actual fault point, the absolute time scale provided by the GPS is not needed in the calculation process of the whole algorithm, the fault location can be completed under the condition of double-end time scale abnormality, the fault location is based on a single-end method, the fault location is not influenced by the length of a cable in a station, and the influence of the length and the structure of the cable is relatively reduced.
Fifth embodiment (V),
Taking the Liaoning power grid 220kV element neutral line actual fault as an example for analysis
The full length of the line in the 220kV element central line of the Liaoning power grid is about 79.91km, the fault causes about 1.5km measurement error due to the abnormality of the time service device, and the actual line inspection result after the fault is as follows: the fault point is about 37.375km from the Yuanlong, about 42.53km from the Zhongzhai, and the secondary fault is close to a metallic short-circuit fault.
Step 1: and performing line mode transformation on the three-phase current acquired at the fault moment, and transforming the phase component into a line mode component by adopting a symmetrical transformation matrix.
Step 2: wavelet transformation and fault initial moment calculation: the wavelet transform coefficients obtained by decomposing the modulus components using the selected spline wavelet and transform scale are shown in fig. 7 (a). The invention adopts a mode maximum value method to identify the fault initial time at two ends of the line and extracts the time delay delta t of the fault initial time, as shown in fig. 7 (b).
Step 3: forward translation compensation and cross correlation sequence calculation: after forward translation compensation of the data at two ends, the forward cross-correlation sequence at two ends extracted by wavelet transformation is shown in fig. 8, and clutter interference is effectively inhibited relative to fig. 7, but because the secondary fault is close to a metallic fault, the bus reflected wave at the opposite end of the line is weaker, and therefore, no obvious fault point/bus reflected wave exists in the forward cross-correlation sequence.
Step 4: reverse translation compensation and cross correlation sequence calculation: after the opposite-end data is subjected to reverse translation compensation, the opposite-end reverse cross-correlation sequence extracted by wavelet transformation is shown in fig. 9, and compared with the forward cross-correlation sequence, fault point reflection waves in the reverse cross-correlation sequence are relatively enhanced, as shown by red circles, and are positive-polarity reflection.
Step 5: and (3) reflected wave identification: in the forward cross-correlation sequence analysis, two reflection wave combinations meeting the conditions are not found; therefore, according to the backward cross-correlation sequence, the maximum amplitude reflected wave is screened out according to the polarity and amplitude principle as shown in fig. 9.
Step 6: single-ended traveling wave fault location: substituting the possible reflected wave into equation 9 for calculation, (t' 1 -t 0 ) =158, combined with 220kV single-loop wave speed 293m/us to obtain a fault point as follows: 37.035m, 340m from the actual fault point.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of protection thereof, although the present application is described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: various changes, modifications, or equivalents may be made to the particular embodiments of the application by those skilled in the art after reading the present application, but such changes, modifications, or equivalents are within the scope of the claims appended hereto.
Claims (8)
1. The high-adaptability power transmission line fault location method is characterized by comprising the following steps of:
extracting three-phase current after the power transmission line fails, and carrying out modulus transformation on the three-phase current to obtain line modulus;
performing multi-scale transformation on the line modulus, and positioning fault initial moments at two ends of the power transmission line;
calculating time delay according to the fault initial moments of the two ends of the power transmission line;
determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
performing fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave;
the identifying fault point reflected waves and/or busbar reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at two ends of the power transmission line comprises the following steps:
and identifying fault point reflected waves and bus reflected waves according to the forward cross-correlation sequence, wherein the conditions comprise:
1) The fault point reflected wave and the bus reflected wave are reflected by negative polarity;
2) Amplitude A of fault point reflected wave and bus reflected wave f Meets the requirement of 0.01 xA is less than or equal to A f ≤0.25×β 1 ×β 2 X A, wherein A is the initial wave head amplitude, beta 1 、β 2 Bus reflection coefficients at two ends of the line respectively; and
3) The fault point reflected wave and the opposite fault point reflected wave satisfy the following equation:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L
wherein t 'is' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the whole length of the line at the initial moment of the wave head, and v is the wave speed;
identifying fault point reflected waves and/or bus reflected waves with a reverse cross-correlation sequence, comprising:
the fault point reflected wave or bus reflected wave can be only identified according to the backward cross correlation sequence identification, and the conditions comprise:
1) The fault point reflected wave or the bus reflected wave is reflected by negative polarity;
2) Amplitude A of fault point reflected wave or bus reflected wave f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A；
Performing fault ranging calculation according to the identified fault point reflected wave and the bus reflected wave, including:
if the fault point reflected wave and the bus reflected wave are identified at the same time, carrying out fault distance measurement calculation according to the following formula:
wherein d is the distance value obtained by testing, t' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the full length of the line at the initial moment of the wave head;
after the fault location calculation is completed, the identified reflected waves are respectively corresponding to the single-ended data mode maximum values according to the mode maximum value sequence, and the reflected waves are determined to be fault point reflected waves or bus reflected waves.
2. The high-adaptability transmission line fault location method as claimed in claim 1, wherein the extracting three-phase current after transmission line fault, and performing modulus transformation on the three-phase current to obtain line modulus, comprises:
and carrying out modulus transformation on the three-phase current according to the following formula, and transforming the three-phase current into linear modulus:
wherein I is a 、I b 、I c Is three-phase current; i α Alpha modulus, I, for three-phase current β Beta modulus, I, of a three-phase current 0 Zero modulus for three phase current.
3. The high-adaptability transmission line fault location method as claimed in claim 1, wherein the multi-scale transformation of line modulus is performed to locate the fault initiation time at both ends of the transmission line, comprising:
carrying out multi-scale transformation on the line modulus by using a binary wavelet, and decomposing the line modulus into an approximate coefficient and a detail coefficient by using the wavelet transformation according to the wavelet transformation scale;
selecting a frequency band with the maximum transient amplitude at two ends of a line for analysis by taking the amplitude mean value of the detail coefficient of the wavelet transformation as a standard;
extracting wavelet transformation detail coefficients of the selected frequency band, and calculating a modular maximum value sequence;
and positioning the fault initial time according to the module maximum value sequence.
4. The high-adaptability transmission line fault location method as claimed in claim 1, wherein the time delay is calculated according to the following equation from the initial moments of faults at both ends of the transmission line:
Δt＝t m -t n
Wherein Deltat is the time delay, t m And t n The initial time of the fault at the two ends of the line.
5. The high-adaptability transmission line fault location method according to claim 1, wherein the forward cross-correlation sequences at two ends of the transmission line are determined according to a wavelet transformation scale and the time delay following formula:
w(t)＝x m (t)×x n (t+Δt)
wherein w (t) is a forward cross-correlation sequence at two ends of the transmission line, and x m (t) and x n (t)The wavelet transformation coefficients are respectively at two ends of the power transmission line, and deltat is the time delay.
6. The high-adaptability transmission line fault location method as claimed in claim 1, wherein determining the reverse cross-correlation sequence at both ends of the transmission line according to the wavelet transformation scale and the time delay comprises:
and calculating analysis data of any one of the two ends of the power transmission line according to the following formula, and transposing the analysis data:
y(t 0 +i)＝x(t 0 +DL－i)
wherein dl=l/v×1/fs
Wherein y (t) is single-ended data of the transmission line after transposition, x (t) is single-ended data of the transmission line before transposition, t 0 I=1, 2..dl, DL is the time window, L is the line full length, v is the wave speed, f s Is the sampling frequency;
substituting the transposed single-ended data of the power transmission line and the non-transposed opposite-end data of the power transmission line into the following data to obtain a reverse cross-correlation sequence at two ends of the power transmission line:
w(t)'＝x m (t)×x n (t+Δt)
Wherein w (t)' is a reverse cross-correlation sequence at two ends of the transmission line, and x m (t) and x n And (t) is the wavelet transformation coefficient at two ends of the power transmission line, and deltat is the time delay.
7. The high-adaptability transmission line fault location method as claimed in claim 3, wherein if only the fault point reflected wave or the bus reflected wave can be identified, the fault location calculation is performed as follows:
d＝(t 1 '-t 0 )×v/2
after the fault distance measurement calculation is completed, the identified reflected wave corresponds to the single-end data mode maximum value according to the mode maximum value sequence, and the identified reflected wave is determined to be a fault point or an opposite-end bus reflected wave.
8. A high adaptability transmission line fault location system, comprising:
the extraction module is used for extracting three-phase current after the power transmission line faults and carrying out modulus transformation on the three-phase current to obtain line modulus;
the positioning module is used for carrying out multi-scale transformation on the line modulus and positioning fault initial moments at two ends of the power transmission line;
the calculation module is used for calculating time delay according to the fault initial moments of the two ends of the power transmission line;
the correlation sequence module is used for determining a forward cross-correlation sequence and a reverse cross-correlation sequence at two ends of the power transmission line according to the wavelet transformation scale and the time delay;
The identification module is used for identifying fault point reflected waves and/or bus reflected waves according to the forward cross-correlation sequences and the reverse cross-correlation sequences at the two ends of the power transmission line;
the distance measuring module is used for carrying out fault distance measurement calculation according to the identified fault point reflected wave and/or bus reflected wave;
the identification module is specifically configured to:
and identifying fault point reflected waves and bus reflected waves according to the forward cross-correlation sequence, wherein the conditions comprise:
1) The fault point reflected wave and the bus reflected wave are reflected by negative polarity;
2) Amplitude A of fault point reflected wave and bus reflected wave f Meets the requirement of 0.01 xA is less than or equal to A f ≤0.25×β 1 ×β 2 X A, wherein A is the initial wave head amplitude, beta 1 、β 2 Bus reflection coefficients at two ends of the line respectively; and
3) The fault point reflected wave and the opposite fault point reflected wave satisfy the following equation:
0.97×L≤(t' 1 -t 0 )×v+(t' 2 -t 0 )×v≤1.03×L
wherein t 'is' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the whole length of the line at the initial moment of the wave head, and v is the wave speed;
identifying fault point reflected waves and/or bus reflected waves with a reverse cross-correlation sequence, comprising:
the fault point reflected wave or bus reflected wave can be only identified according to the backward cross correlation sequence identification, and the conditions comprise:
1) The fault point reflected wave or the bus reflected wave is reflected by negative polarity;
2) Amplitude A of fault point reflected wave or bus reflected wave f The following conditions should be satisfied: a is more than or equal to 0.01 xA f ≤0.25×β 1 XA or 0.01 XA.ltoreq.A f ≤0.25×β 2 ×A；
Performing fault ranging calculation according to the identified fault point reflected wave and the bus reflected wave, including:
if the fault point reflected wave and the bus reflected wave are identified at the same time, carrying out fault distance measurement calculation according to the following formula:
wherein d is the distance value obtained by testing, t' 1 For the moment of reflection of the fault point, t' 2 Time t is the moment of reflected wave of bus 0 L is the full length of the line at the initial moment of the wave head;
after the fault location calculation is completed, the identified reflected waves are respectively corresponding to the single-ended data mode maximum values according to the mode maximum value sequence, and the reflected waves are determined to be fault point reflected waves or bus reflected waves.
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| CN111123033B (en) * | 2019-12-23 | 2022-07-29 | 贵州电网有限责任公司 | Distribution line potential fault identification method |
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| CN118347393B (en) * | 2024-06-18 | 2024-09-10 | 国网江西省电力有限公司电力科学研究院 | Power transmission line sag detection method based on inherent noise of power line |
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