A method, apparatus, and power system for accurately locating faults on a power transmission line

Abstract

This invention relates to the field of transmission line fault detection technology, and more particularly to a method, apparatus, and power system for accurately locating faults in transmission lines. The method includes: determining the start time of a fault in the transmission line under test based on first current data collected by the protection winding of a current transformer; collecting second current data of the transmission line under test within a preset time period through the metering winding of the current transformer at the start time; and utilizing undistorted second current data before the metering winding saturates within a preset time period after the fault occurs. This allows for the rapid and accurate determination of the distance between the fault location and the metering winding of the current transformer, achieving precise fault location. Experimental results show that the fault distance error can be reduced to within 50 meters.

Description

Technical Field

[0001] This invention relates to the field of power transmission line fault detection technology, and in particular to a method, apparatus and power system for accurately locating faults in power transmission lines. Background Technology

[0002] Modern production and modern life are inseparable from electricity. A modern power system consists of power plants (thermal power plants, hydropower plants, nuclear power plants, wind power plants, tidal power plants, etc.), power grids (including substations, transmission and distribution lines, power dispatching systems, etc.), and electricity users. The capacity and coverage of power systems are constantly expanding, transmission voltage is continuously increasing, and transmission distances are becoming longer and longer. On the other hand, modern electricity users have increasingly higher requirements for power quality. If the power quality is unsatisfactory or there is a sudden power outage, the resulting losses can be unacceptable or even catastrophic for users. In power system accidents, power line failures account for a significant proportion.

[0003] The importance of power transmission lines to the power system is self-evident. High-voltage transmission lines are the lifeblood of the power system, bearing the heavy responsibility of transmitting electrical energy. At the same time, they are also the places in the power system where faults occur most frequently and are extremely difficult to locate. Therefore, quickly and accurately locating the fault point after a line fault occurs is not only crucial for timely line repair and ensuring reliable power supply, but also plays a vital role in the safe, stable, and economical operation of the power system.

[0004] my country's power transmission lines are subject to complex geographical and climatic influences, as well as human-caused damage, resulting in various line operation failures. Analyzing the causes of these failures and finding reasonable and effective prevention and control measures are essential to ensuring the normal operation of my country's power supply.

[0005] Traditional fault location devices have significant errors in fault identification and fault location. The theoretical fault location may differ from the actual fault location on the line by several kilometers or even tens of kilometers. This makes it very difficult for line inspectors to find the fault, analyze the cause of the fault, and eliminate the fault. This is especially true in mountainous areas and other areas with complex road conditions along the line corridor. It often takes several days to find the fault location and restore power to the line, which has a great impact on people's production and life. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method, apparatus and power system for accurately locating faults in transmission lines, addressing the shortcomings of the prior art.

[0007] The technical solution of the method for accurately locating faults in transmission lines according to the present invention is as follows:

[0008] The starting time of the fault in the transmission line under test is determined based on the first current data of the transmission line under test collected by the current transformer protection winding.

[0009] Based on the second current data of the transmission line under test collected by the current transformer metering winding within a preset time period at the starting moment, the distance between the location of the fault and the current transformer metering winding is determined.

[0010] The beneficial effects of the method for accurately locating faults in transmission lines according to the present invention are as follows:

[0011] This system can simultaneously acquire current data of the transmission line under test through dual channels at high speed using both the protection winding and the metering winding of the current transformer. Utilizing the undistorted second current data from the metering winding of the current transformer before it saturates within a preset time period after a fault occurs, it can quickly and accurately determine the distance between the fault location and the metering winding, achieving precise fault location. Experimental results show that it can improve fault distance accuracy to within 50 meters. This significantly reduces the arduous work of manual line inspection and can also detect faults that are normally difficult to spot.

[0012] Based on the above scheme, the fault detection method for transmission lines of the present invention can be further improved as follows.

[0013] Furthermore, the process of determining the distance between the location of the fault and the metering winding of the current transformer based on the second current data includes:

[0014] Based on the second current data, the location of the fault and the distance between the current transformer metering winding are determined by combining the impedance method and the fault recording analysis method.

[0015] Furthermore, the process of determining the location of the fault and the distance between the current transformer metering winding and using a combination of impedance method and fault recording analysis includes:

[0016] Based on the second current data, the phase correction coefficient corresponding to the second current data is obtained by fault recording analysis.

[0017] The second current data is corrected according to the phase correction coefficient, and the distance between the location of the fault and the metering winding of the current transformer is determined using the impedance method and based on the corrected second current data.

[0018] The beneficial effect of adopting the above-mentioned further scheme is that the second current data is corrected by the phase correction coefficient obtained by the fault recording analysis method, and the distance between the fault location and the metering winding of the current transformer is determined by the impedance method, which further improves the fault location accuracy.

[0019] Furthermore, the preset duration ranges from 1ms to 3ms.

[0020] Furthermore, the preset duration is 3ms.

[0021] The beneficial effects of adopting the above-mentioned further scheme are: within 3ms after a fault occurs in the transmission line, such as a short circuit fault, the current transformer metering winding will maintain linear and transient response characteristics that meet the accuracy requirements. After 3ms after a fault occurs in the transmission line, such as a short circuit fault, the magnetic flux saturation waveform of the current transformer metering winding will be distorted. Therefore, the undistorted waveform data within 3ms after the fault can be used for calculation and analysis, which can improve the positioning accuracy.

[0022] Furthermore, it also includes:

[0023] The fault type is determined based on the first current data.

[0024] The present invention provides a fault detection chip for power transmission lines, wherein the chip performs a fault detection method for power transmission lines as described in any of the preceding claims.

[0025] The technical solution of the fault detection device for power transmission lines of the present invention is as follows:

[0026] It includes a data acquisition device, a current transformer protection winding, a current transformer metering winding, and a fault detection chip for a transmission line as described above.

[0027] The data acquisition device is used to: acquire the first current data through the protection winding of the current transformer, and acquire the second current data through the metering winding of the current transformer, and send the current data and the second current data to the chip.

[0028] The beneficial effects of the fault detection device for power transmission lines of the present invention are as follows:

[0029] This system can simultaneously acquire current data of the transmission line under test through dual channels via the protection winding and metering winding of the current transformer. Utilizing the undistorted second current data wave from the metering winding of the current transformer before it saturates within a preset time period after a fault occurs, it can quickly and accurately determine the distance between the fault location and the metering winding, achieving precise fault location. Experimental results show that it can improve fault distance accuracy to within 50 meters. This significantly reduces the arduous work of manual line inspection and can also detect faults that are normally difficult to spot.

[0030] The present invention provides a power transmission line, including the aforementioned fault detection device for a power transmission line.

[0031] The present invention provides an electric power system comprising the aforementioned transmission line. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating a fault detection method for power transmission lines according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of a fault detection device for a power transmission line according to an embodiment of the present invention;

[0035] Figure 3 Here are schematic diagrams of the voltage and current waveforms;

[0036] Figure 4 for Figure 3 A magnified view of a portion of the image. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 As shown in the figure, a method for accurately locating faults in transmission lines according to an embodiment of the present invention includes the following steps:

[0039] S1. Determine the starting time of the fault in the transmission line under test based on the first current data of the transmission line under test collected by the protection winding of the current transformer.

[0040] The specific installation process of the current transformer protection winding is known to those skilled in the art, and the current data of the transmission line under test can be collected in real time through the current transformer protection winding using a data acquisition device.

[0041] S2. Based on the second current data of the transmission line to be tested collected by the current transformer metering winding within a preset time period at the start moment, determine the location of the fault and the distance between the current transformer metering winding and the fault location.

[0042] The current data of the transmission line under test can also be collected in real time through the metering winding of the current transformer using a data acquisition device. The acquisition frequency of the data acquisition device can be set according to the actual situation so as to obtain as much second current data as possible within a preset time period.

[0043] The first current data and the second current data are both sequences that include each acquisition time and the current corresponding to each acquisition time.

[0044] Among them, the current transformer protection winding and the current transformer metering winding are both current transformers, or other current sensing devices capable of collecting current data of the transmission line under test.

[0045] This system can simultaneously acquire current data of the transmission line under test through dual channels at high speed using both the protection winding and the metering winding of the current transformer. Utilizing the undistorted second current data from the metering winding of the current transformer before it saturates within a preset time period after a fault occurs, it can quickly and accurately determine the distance between the fault location and the metering winding, achieving precise fault location. Experimental results show that it can improve fault distance accuracy to within 50 meters. This significantly reduces the arduous work of manual line inspection and can also detect faults that are normally difficult to spot.

[0046] The following explains the reason for "selecting the second current data of the transmission line under test collected within a preset time period at the start moment to determine the distance between the fault location and the metering winding of the current transformer":

[0047] S10. Select the current transformer protection winding and the current transformer metering winding. For example, the accuracy class parameters of the current transformer protection winding are shown in Table 1 below, and the accuracy class parameters of the current transformer metering winding are shown in Table 2 below.

[0048] Table 1:

[0049]

[0050] Table 2:

[0051]

[0052] S11. Select the transmission line to be tested. Specifically, a 35kV transmission line is selected as the transmission line to be tested, and its specifications are shown in Table 3 below.

[0053] Table 3:

[0054]

[0055] S12. Calculate the impact of the current transformer protection winding and the current transformer metering winding on the fault location accuracy, specifically:

[0056] S120. Assuming a short-circuit fault occurs near the end of the transmission line to be tested, the current at the end of the transmission line to be tested is: 35000V / (8.0102954*2 ohms)=2184.68847A; simulation calculations are performed with a voltage of 35KV and a short-circuit current of 2500A, and the data results in Table 4 below are obtained.

[0057] Table 4:

[0058]

[0059] S121. The DC resistance of the conductor of the transmission line to be tested is 0.2496 ohms / km. The data results in Table 5 below are obtained by calculation.

[0060] Table 5:

[0061]

[0062] S122. According to Table 5, 2.5495338 / 0.055977788≈50. The conductor length error caused by the current transformer protection winding is about 50 times that of the current transformer metering winding. In other words, the current transformer protection winding has a greater impact on the fault location accuracy, while the current transformer metering winding has a smaller impact on the fault location accuracy. Therefore, the current data collected by the current transformer metering winding is used for fault location.

[0063] Then, according to the “Calculation error of conductor length caused by CT error” in Table 5, the error of the current transformer protection winding is 55.97 meters. By replacing the current transformer protection winding with one of higher precision, the fault location error can be improved to within 50 meters.

[0064] S123. Perform calculation and analysis using undistorted waveform data within a preset time period after the fault:

[0065] After communicating with the current transformer manufacturer, it was found that within 3ms after a short-circuit fault, the current transformer's metering winding maintains linear and transient response characteristics that meet accuracy requirements. After 3ms, the current transformer's metering winding experiences flux saturation and waveform distortion. Therefore, undistorted waveform data within 3ms after the fault can be used for calculation and analysis. Figure 3 and Figure 4 As shown:

[0066] Figure 3 In the image, from top to bottom, are the first, second, and third voltage waveforms. The fourth and fifth waveforms are the current waveforms for a short circuit between phases A and B. The first, second, and third voltage waveforms are the normal voltage waveforms obtained when there is no fault. When the current waveform for a short circuit between phases A and B is distorted, according to the second current data of the transmission line under test collected by the current transformer metering winding within a preset time of 3ms at the start, the distortion occurs. Figure 4 The location indicated by the small arrow is used for fault location. Therefore, the second current data of the transmission line under test, collected within a preset time (3ms) at the start of the current transformer metering winding, is used. The second current data of the transmission line under test collected within 3ms is... Figure 4 The part between the two dots, that is, the part pointed to by the large arrow.

[0067] This method determines the distance between the fault location and the current transformer's metering winding by collecting the second current data of the transmission line under test within a preset time period at the start of the fault. Therefore, it is feasible to calculate fault location using the current data from 3ms before the current transformer's metering winding saturates after a fault. Compared to using the current transformer's protection winding, using the second current data collected by the current transformer's metering winding significantly improves the accuracy of fault location.

[0068] Another data-supported case that "can improve fault location error to within 50 meters" is as follows:

[0069] The impact of sampling AD accuracy on fault location accuracy, taking a data acquisition device with a 16-bit sampling AD as an example:

[0070] When the current transformer enters the data acquisition device, it converts the current signal into a voltage signal, specifically 10A corresponds to 3.53V. The total transformation ratio of the data acquisition device is: 500×10 / 3.53=1416.43. The primary current value corresponding to one sampling AD bit in the 16-bit sampling AD is: 1 / 65536×2×5×1416.43=0.216130066A.

[0071] The standard impedance of the transmission line to be tested is: 10000V / 1500A = 6.666666667Ω;

[0072] The error impedance of the transmission line under test is: 10000V / (1500A+0.216130066A)=6.665706227Ω; 6.6666666667Ω-6.665706227Ω=0.00096044Ω. Therefore, the distance error is 0.00096044Ω / 0.2496Ω / km=0.003847915km. Thus, the fault location error can be improved to within 50 meters.

[0073] Optionally, in the above technical solution, S2, the process of determining the location of the fault and the distance between the current transformer metering winding based on the second current data includes:

[0074] S20. Based on the second current data, the location of the fault and the distance between the current transformer metering winding are determined by combining the impedance method and the fault recording analysis method.

[0075] Optionally, in the above technical solution, S20, the process of determining the location of the fault and the distance between the current transformer metering winding by combining the impedance method and the fault recording analysis method includes:

[0076] S200. Based on the second current data, the phase correction coefficient corresponding to the second current data is obtained through fault recording analysis; specifically:

[0077] Specifically: The fault recording analysis method performs a Fourier transform on the recorded waveform data, i.e., the second current data, to extract the fundamental frequency data, remove harmonic components, and derives a ranging equation based on relevant line parameters and the voltage and current at the fault point, then analyzes and calculates it to obtain the phase correction coefficient;

[0078] S201. Correct the second current data according to the phase correction coefficient, use the impedance method, and determine the location of the fault and the distance between the current transformer metering winding and the current transformer based on the corrected second current data. Specifically:

[0079] In the impedance method, based on R = U / I (time-dependent value), we calculate R1 = U1 / I1, where R1 is the impedance of the measurement point at the time of the fault, U1 is the bus voltage of the substation where the transmission line under test is located at the time of the fault, and I1 is the current of the current transformer metering winding at the time of the fault. We then calculate L = R1 / R0, where L is the distance from the current transformer metering winding to the fault point, and R0 is the unit impedance of the conductor of the transmission line under test. Using the second current data, we substitute it into the impedance method to obtain the distance from the current transformer metering winding to the fault point.

[0080] The second current data is corrected by the phase correction coefficient obtained by the fault recording analysis method, and then the location of the fault and the distance between the current transformer metering winding are determined by the impedance method, which further improves the fault location accuracy.

[0081] Optionally, the above technical solution also includes:

[0082] S3. Determine the fault type based on the first current data.

[0083] Optionally, in the above technical solution, the preset duration ranges from 1ms to 3ms.

[0084] Optionally, in the above technical solution, the preset duration is 3ms.

[0085] Optionally, the above technical solution also includes: determining the fault type based on the first current data of the transmission line under test collected by the current transformer protection winding, wherein the fault type is: single-phase grounding, phase-to-phase short circuit, three-phase short circuit, etc. The specific implementation process is well known to those skilled in the art and will not be described in detail here.

[0086] In the above embodiments, although the steps are numbered S1, S2, etc., they are only specific embodiments given in this application. Those skilled in the art can adjust the execution order of S1, S2, etc. according to the actual situation, which is also within the protection scope of this invention. It can be understood that in some embodiments, some or all of the above embodiments may be included.

[0087] This invention provides a fault detection chip for power transmission lines, wherein the chip executes any of the above-described fault detection methods for power transmission lines.

[0088] A fault detection device for a transmission line according to an embodiment of the present invention includes a data acquisition device, a current transformer protection winding, a current transformer metering winding, and the aforementioned fault detection chip for a transmission line.

[0089] The data acquisition device is used to: acquire first current data through the protection winding of the current transformer, and acquire second current data through the metering winding of the current transformer, and send the current data and the second current data to the chip.

[0090] This system can rapidly and synchronously acquire current data of the transmission line under test through dual channels of the current transformer's protection winding and metering winding. Utilizing the undistorted second current data wave from the metering winding before it saturates within a preset timeframe after a fault occurs, it can quickly and accurately determine the distance between the fault location and the metering winding, achieving precise fault location and fault type identification. Experimental results show that it can improve fault distance accuracy to within 50 meters. This significantly reduces the arduous work of manual line inspection and can also detect faults that are normally difficult to spot.

[0091] The implementation of the corresponding functions of the fault detection device for transmission lines of the present invention described above can be referred to each embodiment of the fault detection method for transmission lines described above, and will not be repeated here.

[0092] An embodiment of the present invention provides a power transmission line, including the aforementioned fault detection device for a power transmission line.

[0093] An embodiment of the present invention provides a power system including the aforementioned transmission line.

[0094] Those skilled in the art will know that this invention can be implemented as a system, method, or computer program product.

[0095] Therefore, this disclosure can be implemented in the following forms: it can be entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software, generally referred to herein as a "circuit," "module," or "system." Furthermore, in some embodiments, the invention can also be implemented as a computer program product in one or more computer-readable media, the computer-readable medium containing computer-readable program code.

[0096] Any combination of one or more computer-readable media may be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this document, a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0097] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of accurately locating a fault on a power transmission line, characterized by, The method comprises: determining a starting time of a fault of a power transmission line to be detected according to first current data of the power transmission line to be detected collected by a protection winding of a current transformer; determining a distance between a location of the fault and a metering winding of the current transformer according to second current data of the power transmission line to be detected collected by the metering winding of the current transformer within a preset time length at the starting time, the preset time length ranging from 1 ms to 3 ms.

2. A method of accurately locating a fault on a power transmission line as claimed in claim 1, characterised in that, The process of determining the distance between the location of the fault and the metering winding of the current transformer according to the second current data comprises: determining the distance between the location of the fault and the metering winding of the current transformer based on the second current data by means of a combination of an impedance method and a fault recording analysis method.

3. A method of accurately locating a fault on a power transmission line as claimed in claim 2, characterised in that, The process of determining the distance between the location of the fault and the metering winding of the current transformer by means of the combination of the impedance method and the fault recording analysis method comprises: obtaining a phase correction coefficient corresponding to the second current data by means of the fault recording analysis method based on the second current data; correcting the second current data according to the phase correction coefficient, determining the distance between the location of the fault and the metering winding of the current transformer by means of the impedance method, and based on the corrected second current data.

4. A method of accurately locating a fault on a power transmission line as defined in claim 1, wherein, The preset time length is 3 ms.

5. A method of accurately locating a fault on a power line as claimed in any one of claims 1 to 3, characterised in that, The method further comprises: determining a fault type of the fault according to the first current data.

6. An apparatus for accurately locating a fault on a power transmission line, the apparatus comprising: The device comprises a data collection apparatus, a protection winding of a current transformer, a metering winding of the current transformer, and a chip for implementing any one of the methods of claims 1-5. The data collection apparatus is configured to collect the first current data by means of the protection winding of the current transformer, collect the second current data by means of the metering winding of the current transformer, and send the first current data and the second current data to the chip.

7. An electric power system for accurately locating a fault on a power transmission line, characterized by The device of claim 6 is included.

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