A dc power transmission line travelling wave fault location terminal, method and system

Abstract

The application provides a DC transmission line traveling wave fault location terminal, method and system, the traveling wave fault location terminal comprises a non-contact sensor, the method comprises determining a fault feature of the traveling wave fault location terminal, determining a fault type based on the fault feature, and performing traveling wave fault location based on the fault type, the application is based on the transient voltage collected by a plurality of distributed traveling wave fault location terminals, the DC transmission line between adjacent traveling wave fault location terminals is relatively short, the influence of the transient voltage attenuation due to long-distance transmission on the starting reliability of the traveling wave fault location terminal is reduced, the influence of the wave velocity error is reduced, the precision of the DC transmission line fault location is improved, and the application can also normally complete the traveling wave fault location under abnormal conditions of a certain traveling wave fault location terminal, and has high reliability.

Description

Technical Field

[0001] The present invention relates to the field of power system automation, and in particular to a direct current transmission line traveling wave fault location terminal, method and system. Background Art

[0002] In recent years, high-voltage direct current (HVDC) transmission has experienced rapid development in my country. Fault location on DC transmission lines is crucial for rapid troubleshooting, power restoration, and the safety and stability of AC and DC systems. Existing DC transmission lines primarily utilize the DC traveling wave fault location method, based on the two-terminal traveling wave principle. While this method generally meets the requirement for an average distance measurement error of approximately 1 km, it suffers from the following two drawbacks:

[0003] (1) Low reliability: In the existing technology, the traveling wave fault location terminal for DC transmission lines uses the neutral point current of the coupling capacitor (or noise filter) in the converter station to collect transient voltage. Its sampling principle is as follows: Figure 1 The neutral point current of the coupling capacitor corresponds to the voltage change rate (transient quantity) of the DC transmission line rather than the actual voltage, which leads to the following problems:

[0004] 1) It is greatly affected by the length of the DC transmission line and the location of the fault point. Since the high-frequency quantity of transient traveling waves decays rapidly during transmission, it is exponentially related to the length of the DC transmission line. When the fault point is biased towards one side of the DC transmission line, the transient quantity on the side farther away from the fault point is often smaller. In domestic artificial short-circuit tests, the fault point is close to both ends of the DC transmission line. The traveling wave fault ranging terminals on both sides of the DC transmission line collected a large difference in the amplitude of the neutral point current of the coupling capacitor, and the longer the line is, the greater the amplitude difference is. Figure 2 and Figure 3 shown.

[0005] 2) The fault transition resistance has a significant impact on the transient change rate of the DC transmission line. The transient change rate is directly related to the fault transition resistance. When the grounding / short circuit transient transition resistance is large, the transient amplitude is low, which will significantly reduce the voltage change rate of the DC transmission line, thereby reducing the reliability of the fault location terminal.

[0006] (2) Accuracy is significantly affected by line length. The principle of the two-terminal traveling wave method indicates that the influence of the traveling wave velocity is relatively greater when the DC transmission line is longer. Assuming the fault point is close to one side of the DC transmission line, a 1% error between the set velocity and the actual velocity will result in an additional measurement error of approximately 0.5% for the DC transmission line. Furthermore, as the length of the DC transmission line increases and the area covered expands, factors such as sag and earth resistivity will cause errors in both length and velocity to increase, resulting in lower ranging accuracy. Summary of the Invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, such as low reliability and accuracy significantly affected by line length, the present invention provides a traveling wave fault ranging terminal, method and system for DC transmission lines. The terminal includes two non-contact sensors. The method includes determining fault characteristics of the traveling wave fault ranging terminal, determining the fault type based on the fault characteristics, and performing traveling wave fault ranging based on the fault type. This not only greatly improves the reliability of ranging, but also reduces the accuracy affected by line length, thereby improving ranging accuracy.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides a traveling wave fault location terminal for a DC transmission line. The traveling wave fault location terminal is installed on a tower and includes two non-contact sensors;

[0010] The non-contact sensor is connected to the traveling wave fault location terminal via a cable and is used to collect analog voltage signals of the DC transmission line.

[0011] The non-contact sensor includes a sensing electrode, a shielding electrode, a measuring capacitor and a protective cover;

[0012] The protective cover is located on the upper part of the shielding electrode, the sensing electrode is located inside the shielding electrode, the shielding electrode is grounded, one end of the measuring capacitor is connected to the sensing electrode, the other end is connected to the shielding electrode, and the measuring capacitor is connected in parallel with the traveling wave fault ranging device.

[0013] The area of ​​the sensing electrode is greater than or equal to 0.25m 2 , the distance between the sensing electrode and the shielding electrode is greater than 10 cm.

[0014] The traveling wave fault ranging terminal also includes:

[0015] AD conversion module, used to convert the analog voltage signal collected by the non-contact sensor into a digital voltage signal;

[0016] Wireless communication module, used to send digital voltage signals.

[0017] The non-contact sensor maintains a preset safety distance from the DC transmission line.

[0018] In another aspect, the present invention provides a method for direct current transmission line traveling wave fault location, comprising:

[0019] Determine the fault characteristics of the traveling wave fault location terminal based on the voltage signal collected by the traveling wave fault location terminal;

[0020] If the fault voltage amplitudes of the two traveling wave fault location terminals with the largest amplitudes are both greater than the preset transient voltage threshold value, the fault is determined to be a normal fault; otherwise, the fault is determined to be a high-resistance fault;

[0021] Traveling wave fault location based on conventional fault / high resistance fault.

[0022] Determine the fault characteristics of the traveling wave fault location device, including:

[0023] Based on the transient voltage collected by the traveling wave fault location terminal, the wavelet transform method is used to extract the detail coefficients of the wavelet transform;

[0024] Calculate the modulus maximum sequence based on the detail coefficients;

[0025] The fault initial time is determined based on the modulus maximum sequence, and the transient voltage amplitude corresponding to the fault initial time is set as the fault voltage amplitude.

[0026] Common faults include: the transition resistance of the fault is not greater than 300 ohms;

[0027] High resistance faults include: the transition resistance of the fault is greater than 300 ohms.

[0028] Traveling wave fault location based on conventional faults / high-resistance faults, including:

[0029] The traveling wave fault location terminal with the earliest fault initial moment is set as the first traveling wave fault location terminal;

[0030] Traveling wave fault location is performed based on the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal and the corrected wave velocity of the traveling wave.

[0031] Traveling wave fault location measurement is performed based on the distance between the first traveling wave fault location measurement terminal and the nth traveling wave fault location measurement terminal and the corrected wave velocity of the traveling wave, including:

[0032] Determine the distance between the fault point and the first traveling wave fault location terminal according to the following formula:

[0033] l1=d1-(t n -t1)×v / 2

[0034] Where l1 is the distance between the fault point and the first traveling wave fault location terminal, d1 is the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal, and t n is the fault initial time of the nth traveling wave fault location terminal, t1 is the fault initial time of the first traveling wave fault location terminal, and v is the corrected traveling wave velocity.

[0035] Traveling wave fault location based on conventional faults / high-resistance faults, including:

[0036] The distance between the fault point and the traveling wave fault ranging terminal is calculated as follows:

[0037] l n ≈Δl+d1 / 2

[0038] Where, l n is the distance between the fault point and the nth traveling wave fault ranging terminal; Δl is the distance difference between the fault point to the first traveling wave fault ranging terminal and to the nth traveling wave fault ranging terminal, which is determined based on the attenuation coefficient of the transient voltage amplitude.

[0039] On the other hand, the present invention also provides a DC transmission line traveling wave fault location system, comprising:

[0040] A data receiving module is used to receive the voltage signal from the traveling wave fault location terminal;

[0041] A first determining module is configured to determine a fault characteristic of the traveling wave fault ranging terminal based on the voltage signal;

[0042] The second determination module is used to determine that the fault voltage amplitudes of the two traveling wave fault ranging terminals with the largest amplitudes are both greater than the preset transient voltage threshold value as a normal fault; otherwise, the fault is determined to be a high-resistance fault;

[0043] Distance measurement module, used for traveling wave fault distance measurement based on conventional faults / high-resistance faults;

[0044] Fault characteristics include the initial fault moment and fault voltage amplitude.

[0045] Compared with the closest existing technology, the technical solution provided by the present invention has the following beneficial effects:

[0046] The DC transmission line traveling wave fault ranging terminal provided by the present invention is installed on a tower and includes two non-contact sensors. The non-contact sensors are connected to the traveling wave fault ranging terminal via cables and are used to collect analog voltage signals from the DC transmission line. The non-contact sensors are located outside the DC transmission line at a safe distance, enabling live installation.

[0047] In the traveling wave fault location method for a DC transmission line provided by the present invention, the fault characteristics of the traveling wave fault location terminal are determined based on the voltage signal collected by the traveling wave fault location terminal; a fault in which the fault voltage amplitudes of the two traveling wave fault location terminals with the largest amplitudes are both greater than a preset transient voltage threshold value is determined to be a conventional fault; otherwise, the fault is determined to be a high-resistance fault; performing traveling wave fault location based on conventional faults / high-resistance faults not only greatly improves the reliability of the location measurement, but also reduces the impact of line length on the accuracy, thereby improving the location accuracy;

[0048] The present invention is based on transient voltages collected by multiple distributed traveling wave fault ranging terminals. The DC transmission lines between adjacent traveling wave fault ranging terminals are relatively short, which reduces the impact of transient voltage attenuation due to long-distance transmission on the startup reliability of the traveling wave fault ranging terminals.

[0049] The present invention realizes the correction of traveling wave velocity by using the fault initial time collected by multiple distributed traveling wave fault ranging terminals. In addition, the length of the DC transmission line between adjacent traveling wave fault ranging terminals is relatively short, which reduces the influence of wave velocity error and improves the accuracy of DC transmission line fault ranging.

[0050] The present invention can also normally complete traveling wave fault ranging even when a certain traveling wave fault ranging terminal is abnormal, and has high reliability;

[0051] The present invention segments the DC transmission line through multiple distributed traveling wave fault ranging terminals, thereby indirectly shortening the length of the DC transmission line and reducing the influence of the traveling wave velocity by correcting the traveling wave velocity.

[0052] The present invention identifies the fault type and selects corresponding traveling wave fault ranging based on different fault types, has high accuracy, and realizes ranging of high-resistance faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the sampling principle of the traveling wave fault location terminal for DC transmission lines in the prior art;

[0054] Figure 2 This is the current waveform diagram of the side closer to the fault point in the existing technology;

[0055] Figure 3 This is the current waveform diagram at the side farther from the fault point in the prior art;

[0056] Figure 4 This is a flow chart of a traveling wave fault location method for a DC transmission line according to an embodiment of the present invention;

[0057] Figure 5 1 is a side view structural diagram of a non-contact sensor according to an embodiment of the present invention;

[0058] Figure 6 1 is a schematic diagram of a top view of the non-contact sensor according to an embodiment of the present invention;

[0059] Figure 7 1 is a schematic diagram of the traveling wave fault ranging principle of multiple traveling wave fault ranging terminals in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The present invention will be described in further detail below with reference to the accompanying drawings.

[0061] Example 1

[0062] Embodiment 1 of the present invention provides a traveling wave fault location terminal for a DC transmission line. The traveling wave fault location terminal is installed on a tower and includes two non-contact sensors.

[0063] The non-contact sensor is connected to the traveling wave fault location terminal through a cable and is used to collect analog voltage signals of the DC transmission line.

[0064] The traveling wave fault location terminal also includes:

[0065] AD conversion module, used to convert the analog voltage signal collected by the non-contact sensor into a digital voltage signal;

[0066] Wireless communication module, used to send digital voltage signals.

[0067] The non-contact sensor maintains a pre-set safety distance from the DC transmission line.

[0068] like Figure 5 and Figure 6 As shown, the contactless sensor includes a sensing electrode, a shielding electrode, a measuring capacitor and a protective cover;

[0069] The protective cover is located on the upper part of the shielding electrode, the sensing electrode is located inside the shielding electrode, the shielding electrode is grounded, one end of the measuring capacitor is connected to the sensing electrode, and the other end is connected to the shielding electrode, and the measuring capacitor is connected in parallel with the traveling wave fault ranging device.

[0070] The area of ​​the sensing electrode is greater than or equal to 0.25m 2 , the distance between the sensing electrode and the shielding electrode is greater than 10 cm.

[0071] There is stray capacitance between the sensing electrode and the DC transmission line. When the distance between the non-contact sensor and the DC transmission line is greater than the safe distance, the stray capacitance is mainly related to the size of the sensing electrode due to the isolated conductor effect. When the sensing electrode is circular with a diameter of 0.5m and a safe distance of 10m, the stray capacitance is 2pF. The sensing electrode is not limited to circular or square, and the area is greater than or equal to 0.25m. 2 The shielding electrode is used to shield adjacent polar lines from interference. The spacing between the sensing electrode and the shielding electrode should be greater than 10 cm. The protective cover is designed to protect against water and dust, ensuring the proper functioning of the sensor. The measuring capacitor is used to extract transient voltages. When the voltage divider ratio is 1:1000, the measuring capacitor has a capacitance of 2 uF.

[0072] Each traveling-wave fault-location terminal is connected to two non-contact sensors, one for each positive and negative line. The non-contact sensor, in principle, acts as a capacitive voltage divider, isolating the DC voltage. By using transient measurements, the sampled value of the non-contact sensor approaches zero under normal conditions, while the voltage increases during a fault. Furthermore, the non-contact sensor is installed at a safe distance from the line, enabling live installation of the equipment.

[0073] Example 2

[0074] Embodiment 2 of the present invention provides a method for measuring fault location of a DC transmission line by traveling wave. The specific flow chart is as follows: Figure 4 The specific process is as follows:

[0075] S101: Determine a fault feature of the traveling wave fault ranging terminal based on a voltage signal collected by the traveling wave fault ranging terminal;

[0076] S102: Determine a fault as a normal fault if the fault voltage amplitudes of the two traveling wave fault location terminals with the largest amplitudes are both greater than a preset transient voltage threshold value; otherwise, determine the fault as a high-resistance fault;

[0077] S103: Perform traveling wave fault location based on conventional faults / high-resistance faults.

[0078] Determine the fault characteristics of the traveling wave fault ranging terminal, including:

[0079] Based on the transient voltage collected by the traveling wave fault location terminal, the wavelet transform method is used to extract the detail coefficients of the wavelet transform;

[0080] Calculate the modulus maximum sequence based on the detail coefficients;

[0081] The fault initial time is determined based on the modulus maximum sequence, and the transient voltage amplitude corresponding to the fault initial time is set as the fault voltage amplitude.

[0082] Common faults include: the transition resistance of the fault is not greater than 300 ohms;

[0083] High resistance faults include: the transition resistance of the fault is greater than 300 ohms.

[0084] When the fault is a conventional fault, select the two traveling wave fault location terminals with the earliest initial time (for example, when t1, t nInitially, traveling wave fault location is performed at the initial fault moment of the first traveling wave fault location terminal (1) and the nth traveling wave fault location terminal. The transmission velocity of transient traveling waves on DC transmission lines is related to the line inductance and capacitance parameters, which are also dependent on the environment. Therefore, the line transmission velocity varies within a small range and is not a fixed value. For ultra-long DC transmission lines, even a small deviation in velocity can result in a large fault location error. Therefore, when the fault is a conventional fault, traveling wave fault location is specifically based on the corrected traveling wave velocity.

[0085] Specifically, traveling wave fault location based on conventional faults includes:

[0086] The traveling wave fault location terminal with the earliest fault initial moment is set as the first traveling wave fault location terminal;

[0087] Traveling wave fault location is performed based on the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal and the corrected wave velocity of the traveling wave.

[0088] like Figure 7 As shown in Figure 1, it is assumed that fault location is achieved through n traveling wave fault location terminals, T1-T4 are four traveling wave fault location terminals, F is the fault point, t1-t4 are the initial fault times of the first to fourth traveling wave fault location terminals, respectively.

[0089] Determine the distance between the fault point and the first traveling wave fault location terminal according to the following formula:

[0090] l1=d1-(t n -t1)×v / 2

[0091] Where l1 is the distance between the fault point and the first traveling wave fault location terminal, d1 is the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal, and t n is the fault initial time of the nth traveling wave fault ranging terminal, t1 is the fault initial time of the first traveling wave fault ranging terminal, and v is the corrected traveling wave velocity, which is determined by the following formula:

[0092] v=d n / (t n -t n-1 )

[0093] Where, t n-1 is the initial fault time of the n-1th traveling wave fault location terminal, d n is the distance between the nth traveling wave fault location terminal and the n-1th traveling wave fault location terminal.

[0094] When the fault is a high-resistance fault, select the traveling wave fault location terminal with the largest amplitude (for example: when Uf1 、U fn When it is the largest, the fault initial time and fault voltage amplitude of the first traveling wave fault location terminal and the nth traveling wave fault location terminal are selected for traveling wave fault location.

[0095] Traveling wave fault location based on high-resistance faults, including:

[0096] The distance between the fault point and the traveling wave fault ranging terminal is calculated as follows:

[0097] l n ≈Δl+d1 / 2

[0098] Where, l n is the distance between the fault point and the nth traveling wave fault ranging terminal; Δl is the distance difference between the fault point to the first traveling wave fault ranging terminal and to the nth traveling wave fault ranging terminal, which is determined based on the attenuation coefficient of the transient voltage amplitude, specifically determined as follows:

[0099] Δl=l n -l1=-ln(U fn / U f1 ) / γ

[0100] Where l1 is the distance between the fault point and the first traveling wave fault location terminal, U fn is the fault voltage amplitude of the nth traveling wave fault location terminal, U fn-1 is the fault voltage amplitude of the n-1th traveling wave fault location terminal, γ is the attenuation coefficient, and γ is determined by the following formula:

[0101] γ=-ln(U fn / U fn-1 ) / d n

[0102] Where U fn is the fault voltage amplitude of the n-1th traveling wave fault location terminal.

[0103] Example 3

[0104] Based on the same inventive concept, embodiment 3 of the present invention further provides a traveling wave fault location system for a DC transmission line. The functions of each component are described in detail below:

[0105] A data receiving module, configured to receive a voltage signal from the traveling wave fault location terminal in embodiment 1 of the present invention;

[0106] A first determining module is used to determine a fault feature of the traveling wave fault ranging terminal based on the voltage signal;

[0107] The second determination module is used to determine that the fault voltage amplitudes of the two traveling wave fault ranging terminals with the largest amplitudes are both greater than the preset transient voltage threshold value as a normal fault; otherwise, the fault is determined to be a high-resistance fault;

[0108] Distance measurement module, used for traveling wave fault distance measurement based on conventional faults / high-resistance faults;

[0109] Fault characteristics include the initial fault moment and fault voltage amplitude.

[0110] The first determining module is specifically configured to:

[0111] Based on the transient voltage collected by the traveling wave fault location terminal, the wavelet transform method is used to extract the detail coefficients of the wavelet transform;

[0112] Calculate the modulus maximum sequence based on the detail coefficients;

[0113] The fault initial time is determined based on the modulus maximum sequence, and the transient voltage amplitude corresponding to the fault initial time is set as the fault voltage amplitude.

[0114] Common faults include: the transition resistance of the fault is not greater than 300 ohms;

[0115] High resistance faults include: the transition resistance of the fault is greater than 300 ohms.

[0116] The ranging module is specifically used for:

[0117] The traveling wave fault location terminal with the earliest fault initial moment is set as the first traveling wave fault location terminal;

[0118] The traveling wave fault location measurement is performed based on the distance between the first traveling wave fault location measurement terminal and the nth traveling wave fault location measurement terminal and the corrected wave velocity of the traveling wave, specifically including:

[0119] Determine the distance between the fault point and the first traveling wave fault location terminal according to the following formula:

[0120] l1=d1-(t n -t1)×v / 2

[0121] Where l1 is the distance between the fault point and the first traveling wave fault location terminal, d1 is the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal, and t n is the fault initial time of the nth traveling wave fault ranging terminal, t1 is the fault initial time of the first traveling wave fault ranging terminal, and v is the corrected traveling wave velocity, which is determined by the following formula:

[0122] v=d n / (t n -t n-1 )

[0123] Where, t n-1 is the initial fault time of the n-1th traveling wave fault location terminal, d n is the distance between the nth traveling wave fault location terminal and the n-1th traveling wave fault location terminal.

[0124] The ranging module calculates the distance between the fault point and the traveling wave fault ranging terminal according to the following formula:

[0125] l n ≈Δl+d1 / 2

[0126] Where, l n is the distance between the fault point and the nth traveling wave fault ranging terminal; Δl is the distance difference between the fault point to the first traveling wave fault ranging terminal and to the nth traveling wave fault ranging terminal, which is determined based on the attenuation coefficient of the transient voltage amplitude, specifically determined as follows:

[0127] Δl=l n -l1=-ln(U fn / U f1 ) / γ

[0128] Where l1 is the distance between the fault point and the first traveling wave fault location terminal, U fn is the fault voltage amplitude of the nth traveling wave fault location terminal, U fn-1 is the fault voltage amplitude of the n-1th traveling wave fault location terminal, γ is the attenuation coefficient, and γ is determined by the following formula:

[0129] γ=-ln(U fn / U fn-1 ) / d n

[0130] Where U fn is the fault voltage amplitude of the n-1th traveling wave fault location terminal.

[0131] For the convenience of description, the various parts of the terminal are divided into various modules or units according to their functions and described separately. Of course, when implementing this application, the functions of each module or unit can be implemented in the same or multiple software or hardware.

[0132] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0133] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The terminal for the function specified in the box or boxes.

[0134] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction terminal that implements the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Ordinary technicians in the relevant field can still modify or replace the specific implementation methods of the present invention with equivalents by referring to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for fault location in direct current transmission lines using traveling waves, characterized in that: include: Determine the fault characteristics of the traveling wave fault location terminal based on the voltage signal collected by the traveling wave fault location terminal; If the fault voltage amplitudes of the two traveling wave fault location terminals with the largest amplitudes are both greater than the preset transient voltage threshold value, the fault is determined to be a normal fault; otherwise, the fault is determined to be a high-resistance fault; Traveling wave fault location based on conventional fault-high resistance fault; The fault characteristics include the fault initial time and the fault voltage amplitude; Wherein, the traveling wave fault ranging terminal is installed on the tower and includes: two non-contact sensors; The non-contact sensor is connected to the traveling wave fault location terminal via a cable and is used to collect analog voltage signals of the DC transmission line; The traveling wave fault location based on conventional fault-high resistance fault includes: The traveling wave fault location terminal with the earliest fault initial moment is set as the first traveling wave fault location terminal; Traveling wave fault location is performed based on the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal and the corrected wave velocity of the traveling wave.

2. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: Determining the fault characteristics of the traveling wave fault ranging terminal includes: Based on the transient voltage collected by the traveling wave fault location terminal, the wavelet transform method is used to extract the detail coefficients of the wavelet transform; Calculate the modulus maximum sequence based on the detail coefficients; The fault initial time is determined based on the modulus maximum sequence, and the transient voltage amplitude corresponding to the fault initial time is set as the fault voltage amplitude.

3. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: The conventional faults include: the transition resistance of the fault is not greater than 300 ohms; The high resistance fault includes: the transition resistance of the fault is greater than 300 ohms.

4. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: The performing traveling wave fault ranging based on the distance between the first traveling wave fault ranging terminal and the nth traveling wave fault ranging terminal and the corrected wave velocity of the traveling wave includes: Determine the distance between the fault point and the first traveling wave fault location terminal according to the following formula: l1=d1-(t n -t1)×v / 2 Where l1 is the distance between the fault point and the first traveling wave fault location terminal, d1 is the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal, and t n is the fault initial time of the nth traveling wave fault location terminal, t1 is the fault initial time of the first traveling wave fault location terminal, and v is the corrected traveling wave velocity.

5. The method for DC transmission line traveling wave fault location according to claim 4, characterized in that: The traveling wave fault location based on the conventional fault-high resistance fault includes: The distance between the fault point and the traveling wave fault ranging terminal is calculated as follows: the n ≈Δl+d1 / 2 Where, l n is the distance between the fault point and the nth traveling wave fault ranging terminal; Δl is the distance difference between the fault point to the first traveling wave fault ranging terminal and to the nth traveling wave fault ranging terminal, which is determined based on the attenuation coefficient of the transient voltage amplitude.

6. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: The non-contact sensor includes a sensing electrode, a shielding electrode, a measuring capacitor and a protective cover; The protective cover is located on the upper part of the shielding electrode, the sensing electrode is located inside the shielding electrode, the shielding electrode is grounded, one end of the measuring capacitor is connected to the sensing electrode, the other end is connected to the shielding electrode, and the measuring capacitor is connected in parallel with the terminal.

7. The method for DC transmission line traveling wave fault location according to claim 6, characterized in that: The area of ​​the sensing electrode is greater than or equal to 0.25m 2 , the distance between the sensing electrode and the shielding electrode is greater than 10 cm.

8. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: The traveling wave fault ranging terminal also includes: AD conversion module, used to convert the analog voltage signal collected by the non-contact sensor into a digital voltage signal; Wireless communication module, used to send digital voltage signals.

9. The method for DC transmission line traveling wave fault location according to claim 1, characterized in that: The non-contact sensor maintains a preset safety distance from the DC transmission line.

10. A travelling wave fault location system for a DC transmission line, characterized in that: include: A data receiving module, configured to receive a voltage signal from a traveling wave fault ranging terminal as described in any one of claims 1, 6, 7, 8, and 9; A first determining module is configured to determine a fault characteristic of the traveling wave fault ranging terminal based on the voltage signal; The second determination module is used to determine that the fault voltage amplitudes of the two traveling wave fault ranging terminals with the largest amplitudes are both greater than the preset transient voltage threshold value as a normal fault; otherwise, the fault is determined to be a high-resistance fault; A distance measurement module is used to perform traveling wave fault distance measurement based on conventional faults and high-resistance faults; The fault characteristics include the fault initial time and the fault voltage amplitude; The traveling wave fault location based on the conventional fault-high resistance fault includes: The traveling wave fault location terminal with the earliest fault initial moment is set as the first traveling wave fault location terminal; Traveling wave fault location is performed based on the distance between the first traveling wave fault location terminal and the nth traveling wave fault location terminal and the corrected wave velocity of the traveling wave.

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