Power transmission line double-end traveling wave distance measurement method independent of synchronous time synchronization and related device

Abstract

The invention discloses a power transmission line double-end traveling wave distance measurement method independent of synchronous time synchronization and a related device, and belongs to the technical field of power transmission line traveling wave distance measurement. Carrying out modulus decomposition on the traveling wave electrical quantity to obtain a line mode component and a zero mode component which are independent from each other; calculating line mode wave impedance and zero mode wave impedance based on the frequency change parameters of the power transmission line; calculating to obtain a line-mode inverse traveling wave and a zero-mode inverse traveling wave; discrete wavelet transform is carried out, and the arrival time of a wave head is obtained through detection; for a grounding fault, calculating a fault distance based on a difference value between a line mode wave head arrival time and a zero mode wave head arrival time; for an ungrounded fault, a fault distance is calculated based on a difference value between arrival moments of a traveling wave at the same end and a reflected wave at a fault point. According to the method, the absolute time is replaced by the time difference, the influence of the wave velocity is eliminated through ratio calculation, strict synchronous time synchronization at the two ends is not needed any more for the ground fault and the non-ground fault, and the effectiveness of distance measurement is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of transmission line traveling wave ranging, and particularly relates to a transmission line double-end traveling wave ranging method independent of synchronous time setting and related devices. BACKGROUND

[0002] In the transmission line of the power system, fast and accurate fault location is crucial to shorten the power outage time, reduce economic losses and improve the reliability of the power system. At present, the traveling wave ranging method is widely used in the transmission network, but the traveling wave ranging method faces two major challenges: first, it relies on strict synchronous time setting at both ends, requiring clock error to be less than microseconds, otherwise the ranging error can reach thousands of meters; second, the wave speed is affected by the frequency variation characteristics of the line parameters, and changes with the fault location and environmental factors, making it difficult to accurately obtain the wave speed and affecting the ranging accuracy.

[0003] Therefore, in the current traveling wave ranging in the transmission network, there is a problem that strict synchronous time setting at both ends is relied on, and the ranging error control is insufficient; and the wave speed is affected by the frequency variation characteristics of the line parameters, and changes with the fault location and environmental factors, making it difficult to accurately obtain the wave speed and affecting the ranging accuracy. SUMMARY

[0004] The application provides a transmission line double-end traveling wave ranging method independent of synchronous time setting and related devices, aiming to solve the problem that in the current traveling wave ranging in the transmission network, strict synchronous time setting at both ends is relied on, and the ranging error control is insufficient; and the wave speed is affected by the frequency variation characteristics of the line parameters, and changes with the fault location and environmental factors, making it difficult to accurately obtain the wave speed and affecting the ranging accuracy.

[0005] To achieve the above purpose, the application adopts the following technical scheme: The transmission line double-end traveling wave ranging method independent of synchronous time setting of the application comprises the following steps: S1, collecting the traveling wave electrical quantities at both ends of the transmission line through corresponding sensors; S2, performing modulus decomposition on the collected traveling wave electrical quantities to obtain mutually independent line mode components and zero mode components; S3, calculating the line mode wave impedance and the zero mode wave impedance based on the frequency variation parameters of the transmission line; S4, calculating the line mode counter-traveling wave and the zero mode counter-traveling wave respectively according to the line mode components and the zero mode components, the line mode wave impedance and the zero mode wave impedance; S5, performing discrete wavelet transform on the line mode counter-traveling wave and the zero mode counter-traveling wave to detect the arrival time of the wave head; S6, selecting a ranging model according to the following fault type: If it is a ground fault, the fault distance is calculated based on the difference between the arrival time of the line mode wave head and the arrival time of the zero mode wave head; if it is a non-ground fault, the fault distance is calculated based on the difference between the arrival time of the first wave at the same end and the arrival time of the reflected wave at the fault point; and then the double-end traveling wave distance measurement of the power transmission line is realized without relying on synchronous time.

[0006] In some embodiments, in S2, for a high-voltage direct-current transmission line, the positive and negative polar voltage and current are changed into line zero-mode voltage and current through phase-mode transformation of the following formula: ; ; wherein, and represent the zero-mode and line-mode voltages after phase-mode transformation, respectively, and represent the collected positive and negative polar voltages of the line, respectively; and represent the zero-mode and line-mode currents after phase-mode transformation, respectively, and represent the collected positive and negative polar currents of the line, respectively.

[0007] In some embodiments, in S2, for an alternating-current transmission line, the originally dependent three-phase traveling wave modes are converted into independent voltage and current components according to the following formula: ; ; wherein, , , represent the voltage zero-mode, voltage one-mode and voltage two-mode, respectively, , , represent the three-phase voltages of , , , respectively. , , represent the current zero-mode, current one-mode and current two-mode, respectively, , , represent the three-phase currents of , , , respectively.

[0008] In some embodiments, in S3, the wave impedance is calculated through the frequency-variable parameter set by PSCAD: ; ; in, , , , For the line-mode frequency conversion parameters and zero-mode frequency conversion parameters, , These are the line-mode impedance and zero-mode impedance.

[0009] In some implementations, in S4, the line reverse traveling wave is calculated according to the following formula: ; ; in, and These represent linear mode reverse traveling wave and zero mode reverse traveling wave, respectively.

[0010] In some implementations, in S5, the discrete wavelet transform is defined as follows: ; in, Represents continuous wavelet transform, It is the wavelet mother function The complex conjugate function, It is the scaling factor. It is the shift coefficient. Represent the integration field; Discretize the continuous wavelet, and discretize the scaling factor and displacement coefficient: ; The definition of discrete wavelet transform is obtained as follows: ; By decoupling the data into modalities, at a scaling scale of If there exists a point where the derivative of that point is 0, then that point is a local maximum of the modulus, and the time corresponding to that point is the arrival time of the wavefront.

[0011] In some implementations, in S6; The distance measurement of ground faults is performed using the following formula: ; in, and for Arrival time of zero-mode wavefront and arrival time of line-mode wavefront and for Arrival time of zero-mode wavefront and arrival time of line-mode wavefront for The total length of the section of the line, Distance from the fault point Distance between ends; The distance measurement for ungrounded faults is performed using the following formula: ; in, and These are the first and second arrival times of the wavefront of the initial traveling wave at the fault location. The timing of the end detection point and These are the first and second arrival times of the wavefront of the initial traveling wave at the fault location. The timing of the end detection point.

[0012] This invention also provides a time-independent transmission line double-ended traveling wave ranging system. The system is used to execute a time-independent transmission line double-ended traveling wave ranging method. The system includes a data acquisition module, a modulus decomposition module, a wave impedance calculation module, a reverse traveling wave calculation module, an arrival time detection module, and a ranging module, wherein: Data acquisition module: used to acquire traveling wave electrical quantities at both ends of the transmission line through corresponding sensors; Modulus decomposition module: used to perform modulus decomposition on the acquired traveling wave electrical quantities to obtain mutually independent linear mode components and zero mode components; Wave impedance calculation module: used to calculate the line mode wave impedance and zero mode wave impedance based on the frequency-varying parameters of the transmission line; Anti-traveling wave calculation module: used to calculate the line-mode anti-traveling wave and the zero-mode anti-traveling wave based on the line-mode component and the zero-mode component, the line-mode wave impedance and the zero-mode wave impedance, respectively; Arrival Time Detection Module: Used to perform discrete wavelet transform on linear mode back-traveling waves and zero mode back-traveling waves to detect the arrival time of the wavefront; Ranging module: Used to select the ranging model based on the following fault types: If it is a ground fault, the fault distance is calculated based on the difference between the arrival time of the line mode wavefront and the arrival time of the zero mode wavefront; if it is an ungrounded fault, the fault distance is calculated based on the difference between the arrival time of the first traveling wave at the same end and the reflected wave at the fault point; thus realizing double-end traveling wave ranging of transmission lines without relying on synchronization.

[0013] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above method.

[0014] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method described above.

[0015] The application discloses a power transmission line double-end traveling wave distance measurement method independent of synchronous time matching and a related device.

[0016] The application discloses a power transmission line double-end traveling wave distance measurement method independent of synchronous time matching, which adopts a power transmission line double-end traveling wave distance measurement method independent of synchronous time matching and without wave speed selection, and solves a fault distance based on a double-end line and ground modulus traveling wave arrival time difference for a grounding fault, and solves the fault distance based on a double-end first traveling wave and fault point reflection wave arrival time difference for a non-grounding fault. The application eliminates the influence of the wave speed through mathematical change, and only needs to determine the line zero-mode and line-mode traveling wave arrival time difference of each end of the line to complete distance measurement for the grounding fault, and only needs to determine the first traveling wave and fault point reflection wave arrival time difference of each end of the line to complete distance measurement for the non-grounding fault, so that the strict synchronous time matching at both ends is no longer needed, and the accuracy and reliability of distance measurement are improved.

[0017] In another aspect, the application discloses a power transmission line double-end traveling wave distance measurement system independent of synchronous time matching, which can accurately and efficiently complete distance measurement and provide effective data support for subsequent processing through systematic data collection, mathematical calculation and determination. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application, illustrate embodiments of the application and explain the application, and do not limit the application.

[0019] Figure 1 FIG. 1 is a flowchart of a power transmission line double-end traveling wave distance measurement method independent of synchronous time matching; Figure 2 FIG. 2 is a schematic diagram of a grounding fault traveling wave modulus in an embodiment of the power transmission line double-end traveling wave distance measurement method independent of synchronous time matching; Figure 3 FIG. 3 is a schematic diagram of a non-grounding fault traveling wave propagation in an embodiment of the power transmission line double-end traveling wave distance measurement method independent of synchronous time matching; Figure 4 FIG. 4 is a schematic diagram of a 600km high-voltage direct current (HVDC) power transmission system in simulation verification of the power transmission line double-end traveling wave distance measurement method independent of synchronous time matching; Figure 5 FIG. 5 is a schematic diagram of a 600km alternating current (AC) power transmission system in simulation verification of the power transmission line double-end traveling wave distance measurement method independent of synchronous time matching; Figure 6 FIG. 6 is a schematic diagram of line parameters in simulation verification of the power transmission line double-end traveling wave distance measurement method independent of synchronous time matching. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0022] It should be noted that, in this document, the terms "comprise", "comprising", or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that includes a list of elements not only includes those elements, but also includes other elements not expressly listed, or inherent to such process, method, article, or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0023] It should be noted that the devices and methods disclosed in the embodiments herein can also be implemented in other ways. The device embodiments described above are only illustrative, for example, the flowcharts and block diagrams in the accompanying drawings show the possible implementation architecture, function and operation of the devices, methods and computer program products according to the embodiments herein. In this regard, each block in the flowchart or block diagram can represent a module, program segment or a part of code, which includes one or more executable instructions for implementing the specified logical function, and which includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different orders from that shown in the accompanying drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and sometimes they can be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0024] In addition, each functional module in each embodiment herein can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0025] As shown in Figure 1 The power transmission line double-end traveling wave distance measurement method not dependent on synchronous time in the application comprises the following steps: S1, collecting traveling wave electrical quantities at both ends of the power transmission line through corresponding sensors; S2, performing modulus decomposition on the collected traveling wave electrical quantities to obtain line-mode components and zero-mode components independent of each other; S3, calculating line-mode wave impedance and zero-mode wave impedance based on frequency-varying parameters of the power transmission line; S4, calculating line-mode counter-traveling wave and zero-mode counter-traveling wave respectively based on the line-mode components and the zero-mode components, the line-mode wave impedance and the zero-mode wave impedance; S5, performing discrete wavelet transform on the line-mode counter-traveling wave and the zero-mode counter-traveling wave to detect the arrival time of the wave head; S6, selecting a distance measurement model according to the following fault types: If it is a grounded fault, the difference between the line-mode wave head arrival time and the zero-mode wave head arrival time is calculated to obtain the fault distance; if it is an ungrounded fault, the difference between the arrival time of the first traveling wave at the same end and the arrival time of the reflected wave at the fault point is calculated to obtain the fault distance; and then the power transmission line double-end traveling wave distance measurement method not dependent on synchronous time is realized.

[0026] The power transmission line double-end traveling wave distance measurement method in the application can improve the problem that the previous method depends on double-end microsecond-level clock synchronization and is affected by the frequency-varying characteristics of wave speed; the difference between the line-mode wave head arrival time and the zero-mode wave head arrival time is used for a grounded fault, and the difference between the arrival time of the first traveling wave at the same end and the arrival time of the reflected wave at the fault point is used for an ungrounded fault; the grounded fault needs to provide the respective difference value at both ends, and the ungrounded fault needs to provide the respective difference value at both ends; the double ends do not need any clock synchronization device, the synchronization accuracy requirement is reduced from the microsecond level to no synchronization, and the double-end synchronous time constraint is eliminated. The fault distance calculation in the application only depends on the time difference ratio, overcomes the kilometer-level error caused by the frequency-varying parameters of the line, and eliminates the influence of wave speed; the line-mode components and the zero-mode components are extracted, the absolute time alignment problem is converted into single-end internal time difference operation by separating the fault characteristic signals, the time difference ratio calculation eliminates the wave speed variable, the double ends do not need any form of time synchronization, the distance measurement accuracy is not affected by the frequency-varying parameters of the line, and the application has a certain applicability by processing grounded and ungrounded faults.

[0027] In some embodiments, the specific steps of the power transmission line double-end traveling wave distance measurement method in the application are as follows: Step 1: Collect the traveling wave electrical quantity of the transmission line through the sensor Step 2: For the transmission line symmetrical at both ends, the line mode transformation is performed on the electrical quantity, and the mode decomposition is performed. 1) For the high-voltage direct-current transmission line, the mutual coupling interference between the positive and negative signals is eliminated, and the positive and negative voltage and current are changed into line zero mode voltage and current through phase mode transformation.

[0028] ; ; Among them, and respectively represent the zero mode voltage and the line mode voltage after phase mode transformation, and respectively represent the collected positive and negative voltages of the line; and respectively represent the zero mode current and the line mode current after phase mode transformation, and respectively represent the collected positive and negative currents of the line.

[0029] In this way, the positive and negative coupling interference is eliminated, the line mode / zero mode independence is ensured, and accurate signals are provided for time difference extraction.

[0030] 2) For the alternating current transmission line, the originally independent three-phase traveling wave mode is converted into independent voltage and current components: ; ; Among them, , , respectively represent the voltage zero mode, the voltage one mode, and the voltage two mode, , , respectively represent , , three-phase voltage; , , , respectively represent the current zero mode, the current one mode, and the current two mode, , , respectively represent , , three-phase current.

[0031] In this way, the three-phase independent mode is decoupled, and the traveling wave aliasing error caused by the multi-phase coupling of the alternating current system is avoided.

[0032] Step 3: Calculate wave impedance through frequency-varying parameter set by PSCAD; ; ; Wherein 、 、 、 are line mode frequency-varying parameters and zero mode frequency-varying parameters, 、 are line mode wave impedance and zero mode wave impedance.

[0033] The application is based on PSCAD frequency-varying parameter accurate modeling, improves the calculation accuracy of the backward wave, and supports the accurate detection of wave head.

[0034] Step 4: Calculate line backward wave: ; ; Wherein, and represent line mode backward wave and zero mode backward wave respectively.

[0035] Step 5: Determine the wave head reaching time through wavelet transform of signal, for continuous signal x(t) , the continuous wavelet transform is defined as follows.

[0036] ; Wherein, represents continuous wavelet transform, is the complex conjugate function of wavelet mother function , is a scaling scale factor, is a shift coefficient, indicates an integral domain.

[0037] Discretize the continuous wavelet, and discretize the scaling scale factor and the shift coefficient: ; Get the discrete wavelet transform definition formula: ; By decoupling the data into modes, when the scaling scale is , if there is a point such that the derivative of the point is 0, then the point is a local mode maximum point, and the time corresponding to the point is the reaching time of the wave head.

[0039] Step 5: Different fault types adopt different ranging methods As shown in Figure 2 , ground fault; Figure 2 wherein, and are the arrival time of the end zero-mode wave head and the arrival time of the line-mode wave head, and are the arrival time of the end zero-mode wave head and the arrival time of the line-mode wave head, are the total length of the line section, is the distance from the fault point to the end; , are the line-mode and zero-mode wave speeds, respectively.

[0040] wherein: ; wherein, is the fault occurrence time, and the two equations can be solved to obtain a distance expression that does not contain : ; Similarly N the distance expression for the end is: ; The two equations can be solved to obtain a distance expression that does not contain the wave speed: ; As can be seen from the above equation, the fault position and the wave speed have no relationship, and the right side of the equation is the distance from the end; the arrival times of the zero-mode and line-mode are subtracted from each other, the end is the same, which means that the two ends do not need to be strictly synchronized, and as long as the time scale of the end is accurate, the fault position can be accurately calculated. As shown in

[0041] , for a non-ground fault, Figure 3 wherein, Figure 3 and are the times at which the wave head of the initial traveling wave of the fault reaches the line end detection point for the first and second times, and are the times at which the wave head of the initial traveling wave of the fault reaches the line end detection point for the first and second times.

[0042] The following relationship can be obtained ; The following relationship can be obtained ; It can be seen that the absolute time​ It was converted into the duration relative to the same end. Then no data synchronization is required.

[0043] This invention also provides a time-independent transmission line double-ended traveling wave ranging system. The system is used to execute a time-independent transmission line double-ended traveling wave ranging method. The system includes a data acquisition module, a modulus decomposition module, a wave impedance calculation module, a reverse traveling wave calculation module, an arrival time detection module, and a ranging module, wherein: Data acquisition module: used to acquire traveling wave electrical quantities at both ends of the transmission line through corresponding sensors; Modulus decomposition module: used to perform modulus decomposition on the acquired traveling wave electrical quantities to obtain mutually independent linear mode components and zero mode components; Wave impedance calculation module: used to calculate the line mode wave impedance and zero mode wave impedance based on the frequency-varying parameters of the transmission line; Anti-traveling wave calculation module: used to calculate the line-mode anti-traveling wave and the zero-mode anti-traveling wave based on the line-mode component and the zero-mode component, the line-mode wave impedance and the zero-mode wave impedance, respectively; Arrival Time Detection Module: Used to perform discrete wavelet transform on linear mode back-traveling waves and zero mode back-traveling waves to detect the arrival time of the wavefront; Ranging module: Used to select the ranging model based on the following fault types: If it is a ground fault, the fault distance is calculated based on the difference between the arrival time of the line mode wavefront and the arrival time of the zero mode wavefront; if it is an ungrounded fault, the fault distance is calculated based on the difference between the arrival time of the first traveling wave at the same end and the reflected wave at the fault point; thus realizing double-end traveling wave ranging of transmission lines without relying on synchronization.

[0044] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0045] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method described above.

[0046] The effectiveness of the proposed method for determining the distance between two ends of a transmission line without relying on synchronization is verified through simulation.

[0047] like Figures 4-6 As shown, respectively with Figure 4 and Figure 5 Taking a 600km-long AC and DC transmission line as an example, a frequency-varying model based on the electromagnetic transient simulation software PSCAD is established as follows: Figure 1The simulation model shown. The main line parameters of the system are as follows Figure 6 shown.

[0048] Wherein, respectively, ground fault and ungrounded fault simulation. Fault section Length is divided into: 50km, 100km, 150km, 200km.

[0049] After simulation, the following table 1 results: Table 1 DC line ranging results and actual error

[0050] To sum up, the application does not depend on the synchronous time of the power transmission line double-ended traveling wave ranging method and related device, through the single-ended time difference operation of limiting the ground fault wave head time difference and the ungrounded fault wave head time difference, the double-ended clock synchronization requirement is avoided; based on the time difference ratio calculation fault distance, the mathematical calculation eliminates the wave speed variable; through the branch processing ground fault and ungrounded fault, the ground fault uses the line mode and zero mode wave speed difference, the ungrounded fault uses the reflection wave time delay characteristic; combined with the modulus decomposition and the anti-traveling wave calculation, the coupling interference is stripped, the wave head characteristics are ensured to be pure, and the time difference is accurately extracted. The application replaces the absolute time by the time difference, and the wave speed is eliminated by the ratio calculation, optimizes the double-ended traveling wave ranging of the power transmission line, and has certain applicability.

[0051] Finally, it needs to be pointed out that: the above described, only for the preferred embodiments of the present application, not to limit the application in any form; for ordinary skilled in the art can be shown in the specification and the above described and smoothly implement the application, the above disclosed technical content of a little change, modification and evolution, such as equivalent changes, are equivalent embodiments of the present application; at the same time, any equivalent changes of the above embodiments according to the essential technology of the present application, all still belong to the protection scope of the technical solutions of the present application.

Claims

1. A power line double-ended traveling wave distance measurement method independent of synchronization time, characterized in that, The method comprises the following steps: S1, collecting the traveling wave electrical quantity at both ends of the transmission line through a corresponding sensor; S2, performing modulus decomposition on the collected traveling wave electrical quantity to obtain line mode components and zero mode components that are independent of each other; S3, calculating the line mode wave impedance and the zero mode wave impedance based on the frequency-varying parameters of the transmission line; S4, calculating the line mode back-traveling wave and the zero mode back-traveling wave based on the line mode components and the zero mode components, the line mode wave impedance and the zero mode wave impedance; S5, performing discrete wavelet transform on the line mode back-traveling wave and the zero mode back-traveling wave to detect the arrival time of the wave head; S6, selecting a distance measurement model according to the following fault type: If it is a ground fault, the fault distance is calculated based on the difference between the line mode wave head arrival time and the zero mode wave head arrival time; if it is an ungrounded fault, the fault distance is calculated based on the difference between the first traveling wave at the same end and the reflected wave at the fault point; thereby realizing the transmission line double-end traveling wave distance measurement without relying on synchronous time.

2. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S2, for a high-voltage direct current transmission line, the positive and negative voltage and current are changed into line and zero mode voltage and current through the following formula of phase-mode transformation: ； ； wherein, and respectively represent the zero-sequence and line-sequence voltage after phase-mode transformation, and respectively represent the collected line positive and negative voltage; and respectively represent the zero-sequence and line-sequence current after phase-mode transformation, and respectively represent the collected line positive and negative current.

3. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S2, for an alternating current transmission line, the original three-phase traveling wave modulus that is not independent is converted into independent voltage and current components according to the following formula: ； ； wherein, , , respectively represent a voltage zero modulus, a voltage one modulus, a voltage two modulus, , , respectively represent , , of the three-phase voltage; , , , respectively represent a current zero modulus, a current one modulus, a current two modulus, , , respectively represent , , of the three-phase current.

4. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S3, the wave impedance is calculated through the frequency-varying parameters set by PSCAD: ； ； wherein , , , are the line modal frequency-dependent parameters and the zero-modal frequency- dependent parameters, , are the line modal wave impedances and the zero-modal wave impedances.

5. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S4, the line back-traveling wave is calculated according to the following formula: ； ； wherein and represent the line mode backward wave and the zero mode backward wave, respectively.

6. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S5, the discrete wavelet transform is defined as follows: ； wherein represents a continuous wavelet transform, is the complex conjugate of the mother wavelet φ(ω) = φ*(−ω), is a scaling factor, is a shift coefficient, denotes the integration domain; Discretize the scaling factor and the shift factor of the continuous wavelet: ； Get the discrete wavelet transform definition formula: ； By decoupling the data into modes, at a scale of If there exists a point such that the derivative of the point is 0, then the point is a local mode maximum point, and the time corresponding to the point is the arrival time of the wave front.

7. The synchronization-independent power line double-ended traveling wave distance relaying method of claim 1, wherein, In the S6, The distance measurement of the ground fault adopts the following formula: ； wherein and are the arrival time of the end zero mode wave head and the arrival time of the line mode wave head, and are the arrival time of the end zero mode wave head and the arrival time of the line mode wave head, are the total length of the line section, is the distance of the fault point from the end. The distance measurement of the ungrounded fault adopts the following formula: ； wherein, and are the times of the first and second arrival of the wave front of the initial fault traveling wave at the line end detection point, respectively, and are the times of the first and second arrival of the wave front of the initial fault traveling wave at the line end detection point, respectively.

8. A power line double-ended traveling wave distance measurement system independent of synchronization time setting, characterized in that, The system is used to perform the transmission line double-end traveling wave distance measurement method without relying on synchronous time according to any one of claims 1-7, and the system comprises a data acquisition module, a modulus decomposition module, a wave impedance calculation module, a back-traveling wave calculation module, an arrival time detection module and a distance measurement module, wherein: The data acquisition module is used to collect the traveling wave electrical quantity at both ends of the transmission line through a corresponding sensor; The modulus decomposition module is used to perform modulus decomposition on the collected traveling wave electrical quantity to obtain line mode components and zero mode components that are independent of each other; The wave impedance calculation module is used to calculate the line mode wave impedance and the zero mode wave impedance based on the frequency-varying parameters of the transmission line; The back-traveling wave calculation module is used to calculate the line mode back-traveling wave and the zero mode back-traveling wave based on the line mode components and the zero mode components, the line mode wave impedance and the zero mode wave impedance; The arrival time detection module is used to perform discrete wavelet transform on the line mode back-traveling wave and the zero mode back-traveling wave to detect the arrival time of the wave head; The distance measurement module is used to select a distance measurement model according to the following fault type: If it is a ground fault, the fault distance is calculated based on the difference between the line mode wave head arrival time and the zero mode wave head arrival time; if it is an ungrounded fault, the fault distance is calculated based on the difference between the first traveling wave at the same end and the reflected wave at the fault point; thereby realizing the transmission line double-end traveling wave distance measurement without relying on synchronous time.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The computer program is executed by the processor to implement the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 9. The computer program is executed by the processor to implement the steps of the method according to any one of claims 1-7.

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