CN112865031A - High-voltage direct-current transmission line lightning stroke interference identification method based on current attenuation ratio - Google Patents
High-voltage direct-current transmission line lightning stroke interference identification method based on current attenuation ratio Download PDFInfo
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- CN112865031A CN112865031A CN202110029073.3A CN202110029073A CN112865031A CN 112865031 A CN112865031 A CN 112865031A CN 202110029073 A CN202110029073 A CN 202110029073A CN 112865031 A CN112865031 A CN 112865031A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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Abstract
The invention discloses a high-voltage direct current transmission line lightning stroke interference identification method based on a current attenuation ratio, which comprises the steps of firstly, carrying out phase-mode conversion on positive and negative current signal fault components at a rectifying side in a data window T (usually 0.8-1ms) with a certain length to obtain line-mode current fault components; secondly, sequentially solving the maximum value of the absolute value of the line mode current fault component, the integral of the absolute value of the line mode current fault component and the nominal average value of the line mode current fault component; and finally, calculating the attenuation ratio of the line mode current fault component, comparing the attenuation ratio with a threshold value, and judging lightning stroke interference or faults. The method can accurately identify the lightning stroke interference and improve the reliability of the ultra-high speed transient protection of the direct current line.
Description
Technical Field
The invention belongs to the field of power systems, relates to the field of relay protection of high-voltage direct-current transmission lines, and particularly relates to a high-voltage direct-current transmission line lightning stroke interference identification method based on a current attenuation ratio.
Background
With the gradual depletion of fossil energy and the prominent global climate and environmental problems, clean energy gradually plays an important role in the global energy structure. As a method for effectively solving the problem of clean energy transmission, high-voltage direct-current transmission has the advantages of low line cost, simple structure, large transmission capacity, small loss, long transmission distance and the like, and is widely applied to the aspects of remote transmission of electric energy, asynchronous networking of electric power systems, distributed resource grid connection, urban cable power supply and the like. The protection principle based on the transient quantity only needs single-end fault information and is often used as main protection of a line, but high-frequency signals injected when the line is struck by lightning easily affect the protection based on the transient quantity. For protection of a direct current transmission line, a fast and reliable lightning interference resisting technology is needed, a situation that a fault is caused by lightning is classified into a line fault and a protection action is triggered, and a situation that the fault is not caused by the lightning interference is discriminated and the protection action is not triggered.
At present, the existing achievement aiming at the lightning stroke interference recognition problem is researched from the aspects of numerical values and waveform characteristics on a time domain, energy distribution characteristics on a frequency domain, an artificial intelligence method and the like. The extraction of the waveform characteristics in the time domain needs to be based on a long time window, and is difficult to be matched with ultra-high-speed transient protection. The method of wavelet transformation, HHT and the like is usually adopted in the frequency domain, the interference and fault frequency spectrum energy distribution difference can be effectively extracted, but the selection of the wavelet base and the determination of the parameters have strong experience, and the later has a mode aliasing phenomenon which is difficult to avoid. The artificial intelligence method avoids complex mathematical operation, can achieve the purpose of distinguishing interference and faults by off-line learning of the training set, but has fewer practical examples which can be used as the training set, needs to be based on a large number of simulation results, and the classification standard of the method is not suitable for the practical power system.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a high-voltage direct-current transmission line lightning stroke interference identification method based on a current attenuation ratio, which can quickly and reliably identify the lightning stroke interference, has strong adaptability to the influences of factors such as fault and interference types, lightning current parameters, refracted and reflected traveling waves and the like, and realizes quick identification of the lightning stroke interference in a short data window.
In order to achieve the purpose, the invention adopts the technical scheme that:
a high-voltage direct-current transmission line lightning stroke interference identification method based on a current attenuation ratio is based on a short data window, has good adaptability to different types of faults and interference, and is not influenced by transition resistance and lightning current parameters, and comprises the following steps:
step 1: the lightning stroke interference recognition system collects positive and negative current signals of a rectifying side at a preset sampling frequency, performs phase-mode conversion on the current signals, and automatically records a line-mode current fault component delta I in a preset length data window T (usually 0.6-1ms) after protection is started;
step 2: the maximum value of the absolute value of the linear mode current fault component in the data window is obtained and recorded as delta Imax；
And step 3: the integral of the absolute value of the linear mode current fault component in the data window is obtained according to the formula (1) and is recorded as SI：
Wherein i is 1,2,3, …, n represents each sampling point in the data window, | Δ i (i) | is the absolute value of the line mode current fault component corresponding to the sampling point i moment, T is the length of the data window, Δ T is the sampling point time interval;
and 4, step 4: obtaining a number according to equation (2)Nominal mean value of current fault component Δ I in line mode within windowavg：
And 5: calculating the attenuation ratio K of the line mode current fault component according to the formula (3)att：
Step 6: judging the ratio KattWhether or not the threshold K is exceededatt_setIf the lightning stroke interference exceeds the preset threshold value, judging the lightning stroke interference, and protecting the resetting; if not, judging the lightning stroke fault or the common short circuit fault, ending the algorithm and protecting the normal outlet.
Preferably, the preset sampling frequency of step 1 is set to 100 kHz.
Preferably, the length of the preset-length data window in step 1 is set to 0.8-1 ms.
Preferably, the threshold K of step 6att_setSet to 0.65.
Compared with the prior art, the invention has the following advantages:
1. the method adopts the numerical characteristics of the time domain waveform as the protection criterion, has the advantages of simple calculation, definite physical quantity meaning, low requirements on calculation precision and storage capacity and the like, and effectively avoids the problems of longer time window, higher sampling frequency requirement, dependence on experience on parameter setting and the like when the waveform characteristics or the frequency domain characteristics are adopted as the protection criterion.
2. The invention can ensure reliable distinguishing of lightning stroke interference and faults when the lightning stroke identification data window length is 0.8ms or more. Therefore, the whole set of ultra-high-speed single-terminal protection scheme can obtain the final result of fault judgment and output a trip signal in the range of 0.8 ms-1 ms, meets the requirement of protection mobility, and has lower requirement on calculation speed.
3. Because the invention adopts the ratio of the electric quantity as the protection criterion, the influence of the absolute amplitude of the electric quantity is avoided, and the invention has good adaptability in the aspects of lightning current parameters and transition resistance.
Drawings
Fig. 1 is an LCC-MMC hybrid dc transmission system topology suitable for use in the method of the invention.
Fig. 2 is a flow chart of a method of implementing the present invention.
Fig. 3(a) and 3(b) show the results of determination as to whether or not lightning interference has occurred, respectively, as to the current line mode component waveform at the time of occurrence of lightning interference.
Fig. 4(a) and 4(b) show the results of determination as to whether or not a lightning interference occurs, respectively, as to the current line mode component waveform at the time of occurrence of a lightning fault.
Fig. 5(a) and 5(b) show the results of determination as to whether or not lightning interference has occurred, respectively, as to the current line mode component waveform at the time of occurrence of a normal short-circuit fault.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Fig. 1 shows a +/-500 kV hybrid high-voltage direct-current transmission system with a transmitting end adopting LCC and a receiving end adopting MMC. The LCC side converter station adopts a twelve-pulse converter, the inversion side adopts a 301-level modular multilevel converter, and the converter station is of a true bipolar structure. The model adopts various parameters of a certain direct current transmission project of +/-500 kV, the rated power is 3000MW, and the whole length of the line is 1000 km.
When the high-voltage direct-current transmission line is struck by lightning at the top of the tower 200km away from the protective installation position at the rectification side, the method provided by the invention can eliminate the lightning interference. The lightning current waveform is 1.2/50 mus, the amplitude is-50 kA, and the line has no fault. The identification scheme comprises the following steps, as shown in fig. 2:
step 1: the lightning stroke interference recognition system collects positive and negative current signals of a rectifying side at a sampling frequency of 100kHz, performs phase-mode conversion on the current signals, and automatically records a line-mode current fault component delta I in a data window T with the length of 0.8ms after protection starting;
the fault components of the phase-mode converted line-mode current waveform in this example are shown in fig. 3 (a).
Step 2: calculating the current of the inner line mode of the data windowMaximum absolute value of barrier component, recorded as Δ Imax；
And step 3: the integral of the absolute value of the linear mode current fault component in the data window is obtained according to the formula (1) and is recorded as SI：
Wherein i is 1,2,3, …, n represents each sampling point in the data window, | Δ i (i) | is the absolute value of the line mode current fault component corresponding to the sampling point i moment, T is the length of the data window, Δ T is the sampling point time interval;
and 4, step 4: obtaining the nominal mean value Delta I of linear mode current fault components in the data window according to the formula (2)avg：
And 5: calculating the attenuation ratio K of the line mode current fault component according to the formula (3)att：
In this example, the attenuation ratio K of the line mode current fault component is calculatedatt＝0.93。
Step 6: judging the ratio KattWhether or not the threshold K is exceededatt_setIf the lightning stroke interference exceeds the preset threshold value, judging the lightning stroke interference, and protecting the resetting; if not, judging the lightning stroke fault or the common short circuit fault, ending the algorithm and protecting the normal outlet.
Threshold value K for judging lightning stroke interference and faults set in the embodimentatt_set0.65, ratio KattAnd (3) judging that the lightning interference occurs when the threshold value is exceeded, wherein a judgment result signal is shown in a figure 3(b), wherein 0 represents that the common short circuit fault or the lightning interference occurs, 1 represents that the lightning interference occurs, the algorithm is ended, and the protection is recovered.
In addition, when a lightning stroke occurs at the top of the tower at a distance of 200km from the installation position of the rectifier side protection on the direct current line, the judgment result of whether the lightning stroke interference occurs or not is judged as a lightning stroke fault as shown in fig. 4(a) and 4(b), and a normal outlet is protected. When the positive pole metal grounding short circuit fault occurs in the midpoint of the direct current circuit, the judgment result of the current line module component waveform and whether the lightning stroke interference occurs is shown in fig. 5(a) and fig. 5(b), and the normal outlet is protected.
Claims (4)
1. A high-voltage direct-current transmission line lightning stroke interference identification method based on a current attenuation ratio is characterized by comprising the following steps: based on a short data window, the method has good adaptability to different types of faults and interference, is not influenced by transition resistance and lightning current parameters, and comprises the following steps:
step 1: the lightning stroke interference recognition system collects positive and negative current signals of a rectifying side at a preset sampling frequency, performs phase-mode conversion on the current signals, and automatically records a line mode current fault component delta I in a preset length data window T after protection is started;
step 2: the maximum value of the absolute value of the linear mode current fault component in the data window is obtained and recorded as delta Imax；
And step 3: the integral of the absolute value of the linear mode current fault component in the data window is obtained according to the formula (1) and is recorded as SI：
Wherein i is 1,2,3, …, n represents each sampling point in the data window, | Δ i (i) | is the absolute value of the line mode current fault component corresponding to the sampling point i moment, T is the length of the data window, Δ T is the sampling point time interval;
and 4, step 4: obtaining the nominal mean value Delta I of linear mode current fault components in the data window according to the formula (2)avg：
And 5: according toEquation (3) calculates attenuation ratio K of line mode current fault componentatt：
Step 6: judging the ratio KattWhether or not the threshold K is exceededatt_setIf the lightning stroke interference exceeds the preset threshold value, judging the lightning stroke interference, and protecting the resetting; if not, judging the lightning stroke fault or the common short circuit fault, ending the algorithm and protecting the normal outlet.
2. The method according to claim 1, wherein the preset sampling frequency in step 1 is set to 100 kHz.
3. The method according to claim 1, wherein the length of the preset length data window in step 1 is set to be 0.8-1 ms.
4. The method for identifying the lightning stroke interference of the HVDC line according to claim 1, wherein the threshold K is set in step 6att_setSet to 0.65.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115616332A (en) * | 2022-12-19 | 2023-01-17 | 昆明理工大学 | AC transmission line lightning stroke interference identification method and system based on extension fusion |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115616332A (en) * | 2022-12-19 | 2023-01-17 | 昆明理工大学 | AC transmission line lightning stroke interference identification method and system based on extension fusion |
| CN115616332B (en) * | 2022-12-19 | 2023-03-14 | 昆明理工大学 | AC power transmission line lightning stroke interference identification method and system based on extension fusion |
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