A power transmission line fault simulation and simulation test method and system

Abstract

A power transmission line fault simulation and simulation test method and system, a transient simulation model of an actual power transmission line is established, and a wave speed is simulated and calculated; a simulation test is carried out on a test line, a fault source is output, a normal current at a power frequency is first output, a lightning impulse is injected at a peak of the normal current at the power frequency, and then a flashover discharge current of an insulator string is output, a duration of the flashover discharge current is calculated according to a lightning fault current set during simulation; if the test is normal, wave head times captured by two fault detection devices are obtained, corresponding two positioning errors are calculated in combination with the wave speed calculated by simulation, if the positioning errors exceed a set error threshold, it is indicated that the fault detection device is unqualified; otherwise, it is qualified, and a fault test is carried out by using the qualified fault detection device. The present application can efficiently carry out a detection test of a power transmission line fault positioning device.

Description

Technical Field

[0001] This invention belongs to the field of high voltage technology of power systems, and more specifically, relates to a method and system for simulating and testing transmission line faults. Background Technology

[0002] Traditional power system fault testing typically employs full-scale testing, which utilizes real power equipment to construct actual overhead or cable distribution networks, simulating various defects or faults to reproduce the real-world environment. Full-scale testing can quickly reproduce real operational and fault scenarios, record complete test phenomena and data, and does not affect user power supply; therefore, it is only suitable for distribution lines. However, for transmission lines, the high cost of real equipment and the large required space limit make it unsuitable.

[0003] Currently, transmission line fault testing is mainly conducted using software simulation and laboratory simulation. Based on EMTDC electromagnetic transient simulation software, a distributed parameter model of the transmission line is built, which can simulate the transient characteristics of different voltage levels and capacities. However, because the power source and load contain power electronic devices with nonlinear characteristics, while the actual model is a simple linear combination and does not consider frequency domain effects, this method has a certain degree of subjectivity and differs from the real power grid model. A high-voltage impulse current source is built in a high-voltage laboratory. High-voltage impulse tests can approximately simulate lightning strikes under ideal conditions by injecting high-voltage pulses into the test line. The test line is a very short cable or overhead conductor, and actual components such as surge arresters and insulators are not considered. The high-frequency response characteristics are not significantly different from those of the actual power system, but the test distance is short, making it unsuitable for long-distance transmission lines in the field.

[0004] With the widespread application of fault monitoring devices in power transmission lines, higher requirements are being placed on their monitoring accuracy and stable and reliable operation. Currently, there are numerous fault monitoring device manufacturers, and some domestic metrology and testing units and provincial power grid companies have carried out environmental testing for grid access, which to some extent ensures the adaptability of the equipment to the field application environment. However, there is a lack of effective testing methods and means to verify core functions such as fault current accuracy, traveling wave current accuracy, and fault location accuracy, resulting in a technical vacuum in the depth and breadth of testing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for simulating and testing transmission line faults.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of this invention proposes a method for simulating and testing transmission line faults, comprising:

[0008] Two towers are selected from the actual transmission line as the starting tower and the ending tower, respectively. One tower is selected from all the towers between the starting tower and the ending tower as the fault tower. A test line with the same parameters as the actual transmission line between the starting tower and the ending tower is also built.

[0009] A transient simulation model of an actual transmission line is established. A predetermined lightning fault current is injected into the location of the faulty tower in the simulation model. Current sensors are installed at both the starting and ending towers in the simulation model. The wave velocity is calculated by the time difference of the wavefront time detected by the two current sensors.

[0010] Simulation tests were conducted on the test line. Two fault monitoring devices were installed on the starting and ending towers of the test line. The fault source was set at the location of the faulty tower. The fault source output first output a normal power frequency current, then injected a lightning pulse at a peak of the normal power frequency current, and then output the flashover discharge current of the insulator string. The duration of the flashover discharge current of the insulator string was calculated based on the lightning fault current set during simulation. The amplitude range of the flashover discharge current of the insulator string was set to include the amplitude range corresponding to all fault types.

[0011] If the test line does not trip within the set time range after the lightning pulse is injected, adjust the tripping threshold of the fault detection device on the test line according to the amplitude range of different fault types, and repeat the above steps starting from the output of the fault source; otherwise, the test is normal. Obtain the wavefront time extracted by the lightning current waveform captured by the two fault detection devices, and calculate the corresponding two positioning errors in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

[0012] Preferably, the establishment of a transient simulation model of the actual transmission line, wherein a predetermined lightning fault current is injected into the location of the faulty tower in the simulation model, specifically includes:

[0013] The transient simulation model is a frequency-dependent electromagnetic transient model. The transient simulation model adopts a dual-power supply topology structure. By adjusting the power angle, the active power and load current are changed to the actual active power and load current. The conductor diameter, split bundle, conductor height, ground wire height and phase spacing adopt the corresponding parameters of the actual transmission line. After the transmission line is running stably, after a set delay, the set lightning fault current is injected.

[0014] Preferably, the lightning fault current is specifically:

[0015] The set lightning fault current is obtained by weighting and summing the 8 / 20μs lightning current and the 10 / 350μs lightning current according to the set weights.

[0016] Preferably, the calculation of wave velocity using the time difference of wavefront time detected by two current sensors specifically involves:

[0017] The wavefront times collected by the two current sensors are obtained, and the location of the fault tower with the midpoint of the transmission line as the reference point is obtained. The wave velocity is obtained by dividing the fault tower location of the reference point by twice the difference between the wavefront times collected by the two current sensors.

[0018] Preferably, the fault source is output, specifically as follows:

[0019] The duration of the fault source's initial output of normal power frequency current ranges from one cycle duration of normal power frequency current to two cycles duration of normal power frequency current.

[0020] The duration of the flashover discharge current of the insulator string is: the peak moment of the 10 / 350μs lightning current minus the peak moment of the 8 / 20μs lightning current plus the cycle duration of a normal power frequency current. The calculated result is multiplied by the difference between the weights of the 10 / 350μs lightning current and the 8 / 20μs lightning current, plus the cycle duration of a normal power frequency current.

[0021] Preferably, adjusting the threshold of the fault detection device on the test line according to the amplitude range of different fault types specifically involves:

[0022] The set time range is between the cycle duration of one normal power frequency current and the cycle duration of two normal power frequency currents.

[0023] Fault types include high-resistance faults, low-resistance faults, and metallic grounding faults;

[0024] The amplitude range of a high-resistance fault is from the first threshold to the second threshold; the amplitude range of a low-resistance fault is from the second threshold to the third threshold.

[0025] The threshold for metallic grounding faults is above the third threshold.

[0026] If the circuit breaker does not trip after two cycles of normal power frequency current following the injection of the lightning pulse, the tripping threshold of the fault detection device is lowered. If the current threshold is greater than the third threshold, it is adjusted to the third threshold. If it is greater than the second threshold but less than or equal to the third threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the first threshold.

[0027] If the circuit breaker trips before reaching a normal power frequency current cycle duration after the lightning pulse is injected, the tripping threshold of the fault detection device is increased. If the current threshold is less than the first threshold, it is adjusted to the first threshold. If it is greater than or equal to the first threshold but less than the second threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the third threshold.

[0028] Preferably, if the amplitude of the flashover discharge current of the current insulator string is within the amplitude range of a high-resistance fault, then a set background noise is superimposed on the flashover discharge current of the insulator string. The set background noise is a hidden current signal or a corona current signal with a set frequency and amplitude.

[0029] Preferably, the calculation of the two positioning errors corresponding to the wave velocity calculated by simulation is specifically as follows:

[0030] Obtain the tower numbers of the starting tower, fault tower, and termination tower on the actual transmission line. Use the product of the starting tower number minus the span length multiplied by the tower number, minus the wavefront time extracted by the fault detection device located on the starting tower and the wave velocity calculated by simulation as the first error.

[0031] The second error is calculated as the product of the fault tower number minus the terminal tower number multiplied by the tower number span minus the wavefront time extracted by the fault detection device located on the terminal tower from the lightning current waveform captured by the fault detection device and the wave velocity calculated by simulation.

[0032] The second aspect of this invention proposes a transmission line fault simulation and test system based on the method described in the first aspect of this invention, comprising a test line construction module, a simulation wave velocity calculation module, a simulation test module, and a test module, specifically:

[0033] Test line construction module: used to select two towers from the actual transmission line as the starting tower and the ending tower respectively, and select one tower from all the towers between the starting tower and the ending tower as the fault tower; and to build a test line with the same parameters as the actual transmission line between the starting tower and the ending tower.

[0034] Simulated wave velocity calculation module: used to establish a transient simulation model of the actual transmission line. In the simulation model, a set lightning fault current is injected into the location of the faulty tower. Current sensors are installed at both the starting and ending towers in the simulation model. The wave velocity is calculated by the time difference of the wavefront time detected by the two current sensors.

[0035] Simulation test module: Used to conduct simulation tests on the test line. Two fault monitoring devices are installed on the starting and ending towers of the test line. The fault source is set at the fault tower location. The fault source outputs first a normal power frequency current, then injects a lightning pulse at a peak of the normal power frequency current, and then outputs the insulator string flashover discharge current. The duration of the insulator string flashover discharge current is calculated based on the lightning fault current set during simulation. The amplitude range of the insulator string flashover discharge current includes the amplitude range corresponding to all fault types.

[0036] Test module: If the test line does not trip within the set time range after the injection of a lightning pulse, the threshold for triggering the tripping of the fault detection device on the test line is adjusted according to the amplitude range of different fault types, and the above steps are repeated starting from the output of the fault source; otherwise, the test is normal. The wavefront time of the lightning current waveform captured by the two fault detection devices is obtained, and the corresponding two positioning errors are calculated in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

[0037] A third aspect of the invention provides an apparatus including a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the method described in the first aspect of the invention.

[0038] A fourth aspect of the present invention provides a computer-readable storage medium on which a computer program is stored, wherein the computer program, when executed by a processor, implements the steps of the method described in the first aspect of the present invention.

[0039] The beneficial effects of this invention are that, compared with the prior art, by combining actual line simulation and physical simulation tests, it effectively improves the accuracy and reliability of transmission line fault detection device testing; its advantages are that it uses simulation calculation to obtain wave velocity and reproduces the full waveform fault signal including power frequency current, lightning pulse and flashover discharge on the test line. By adjusting the fault current amplitude and detection threshold, it can comprehensively cover test scenarios of various fault types such as high resistance, low resistance and metallic grounding. The timing of the flashover discharge signal is combined with the lightning current setting input during simulation, thereby realizing the verification of the fault monitoring device's positioning accuracy. At the same time, the introduction of background noise enhances the realism of the test environment, ensuring the effectiveness and adaptability of the device in practical applications. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the transmission line fault simulation and simulation test method of the present invention;

[0041] Figure 2 It is a dual-power segmented line topology;

[0042] Figure 3 A schematic diagram showing the line parameter settings;

[0043] Figure 4 The current waveforms at each monitoring point in the frequency-dependent model are shown. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0045] like Figure 1 As shown, Embodiment 1 of the present invention proposes a method for simulating and testing transmission line faults, including:

[0046] Two towers are selected from the actual transmission line as the starting tower and the ending tower, respectively. One tower is selected from all the towers between the starting tower and the ending tower as the fault tower. A test line with the same parameters as the actual transmission line between the starting tower and the ending tower is also built.

[0047] A transient simulation model of an actual transmission line is established. A predetermined lightning fault current is injected into the location of the faulty tower in the simulation model. Current sensors are installed at both the starting and ending towers in the simulation model. The wave velocity is calculated by the time difference of the wavefront time detected by the two current sensors.

[0048] Simulation tests were conducted on the test line. Two fault monitoring devices were installed on the starting and ending towers of the test line. The fault source was set at the location of the faulty tower. The fault source output first output a normal power frequency current, then injected a lightning pulse at a peak of the normal power frequency current, and then output the flashover discharge current of the insulator string. The duration of the flashover discharge current of the insulator string was calculated based on the lightning fault current set during simulation. The amplitude range of the flashover discharge current of the insulator string was set to include the amplitude range corresponding to all fault types.

[0049] If the test line does not trip within the set time range after the lightning pulse is injected, adjust the tripping threshold of the fault detection device on the test line according to the amplitude range of different fault types, and repeat the above steps starting from the output of the fault source; otherwise, the test is normal. Obtain the wavefront time extracted by the lightning current waveform captured by the two fault detection devices, and calculate the corresponding two positioning errors in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

[0050] In this preferred embodiment, the establishment of a transient simulation model of the actual transmission line, and the injection of a predetermined lightning fault current at the location of the faulty tower in the simulation model, specifically involves:

[0051] The transient simulation model is a frequency-dependent electromagnetic transient model, and the transient simulation model adopts the following... Figure 2 As shown, the dual-power supply topology changes the active power and load current to the actual active power and load current by adjusting the power angle, such as... Figure 3 As shown, the parameters such as conductor diameter, split bundle, conductor height, ground wire height, and phase spacing are adopted from the corresponding parameters of the actual transmission line; after the transmission line is running stably, the set lightning fault current is injected after a set delay period.

[0052] Specifically, the active power of the dual-power supply topology for:

[0053]

[0054] in, , The equivalent potential at both ends of the transmission line, for and The phase difference between two potentials is denoted as the power angle. for and The equivalent reactance between them.

[0055] Specifically, the simulation step size is set to 500 ns, the simulation duration is set to 60 ms, and the delay time is set to 10 ms.

[0056] It should be noted that the current waveforms of the current sensors on each tower in the transient simulation model are as follows: Figure 4 As shown, this embodiment only uses the current waveforms of the current sensors of the starting tower and the ending tower. The tower numbers of the starting tower, the faulty tower and the ending tower selected for the test line are recorded in the test line ledger. The tower numbers of the starting tower, the faulty tower and the ending tower in the simulation model are the same as those in the ledger of the corresponding test line.

[0057] In this preferred embodiment, the lightning fault current specifically comprises:

[0058] The set lightning fault current is obtained by weighting and summing the 8 / 20μs lightning current and the 10 / 350μs lightning current according to the set weights.

[0059] Specifically, lightning fault current The formula is:

[0060]

[0061]

[0062]

[0063] in, , The lightning currents are 8 / 20μs and 10 / 350μs, respectively. The peak value of the lightning current is set to 1000A in this embodiment. For a specific moment; , The weights are respectively for 8 / 20μs lightning current and 10 / 350μs lightning current;

[0064] In this preferred embodiment, the calculation of wave velocity based on the time difference of wavefront times detected by two current sensors specifically involves:

[0065] The wavefront times collected by the two current sensors are obtained, and the location of the fault tower with the midpoint of the transmission line as the reference point is obtained. The wave velocity is obtained by dividing the fault tower location of the reference point by twice the difference between the wavefront times collected by the two current sensors.

[0066] The formula is:

[0067]

[0068] in, The wave velocity calculated in the simulation; Location of the faulty tower; , These are the wavefront times acquired by the two current sensors.

[0069] In this preferred embodiment, the fault source is output, specifically as follows:

[0070] The duration of the fault source's initial output of normal power frequency current ranges from one cycle duration of normal power frequency current to two cycles duration of normal power frequency current.

[0071] The duration of the flashover discharge current of the insulator string is: the peak moment of the 10 / 350μs lightning current minus the peak moment of the 8 / 20μs lightning current plus the cycle duration of a normal power frequency current. The calculated result is multiplied by the difference between the weights of the 10 / 350μs lightning current and the 8 / 20μs lightning current, plus the cycle duration of a normal power frequency current.

[0072] The formula is:

[0073]

[0074] in, The duration of the flashover discharge current of the insulator string; The cycle duration of a normal power frequency current; , The peak times are 8 / 20μs and 10 / 350μs, respectively.

[0075] In this preferred embodiment, adjusting the threshold of the fault detection device on the test line according to the amplitude range of different fault types specifically involves:

[0076] The set time range is between the cycle duration of one normal power frequency current and the cycle duration of two normal power frequency currents.

[0077] Fault types include high-resistance faults, low-resistance faults, and metallic grounding faults;

[0078] The amplitude range of a high-resistance fault is from the first threshold to the second threshold; the amplitude range of a low-resistance fault is from the second threshold to the third threshold; and the threshold for a metallic grounding fault is above the third threshold.

[0079] Specifically, the first threshold is 1A, the second threshold is 10A, and the third threshold is 1000A;

[0080] If the circuit breaker does not trip after two cycles of normal power frequency current following the injection of the lightning pulse, the tripping threshold of the fault detection device is lowered. If the current threshold is greater than the third threshold, it is adjusted to the third threshold. If it is greater than the second threshold but less than or equal to the third threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the first threshold.

[0081] If the circuit breaker trips before reaching a normal power frequency current cycle duration after the lightning pulse is injected, the tripping threshold of the fault detection device is increased. If the current threshold is less than the first threshold, it is adjusted to the first threshold. If it is greater than or equal to the first threshold but less than the second threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the third threshold.

[0082] In this embodiment, if the amplitude of the flashover discharge current of the current insulator string is within the amplitude range of a high-resistance fault, then a set background noise is superimposed on the flashover discharge current of the insulator string. The set background noise is a hidden current signal or a corona current signal with a set frequency and amplitude.

[0083] Specifically, in this embodiment, a 0.5-1A level hidden danger current signal of 100kHz or a 5-10mA level corona current of MHz is added.

[0084] In this preferred embodiment, the calculation of the two positioning errors corresponding to the wave velocity calculated by simulation is specifically as follows:

[0085] Obtain the tower numbers of the starting tower, fault tower, and termination tower on the actual transmission line. Use the product of the starting tower number minus the span length multiplied by the tower number, minus the wavefront time extracted by the fault detection device located on the starting tower and the wave velocity calculated by simulation as the first error.

[0086] The second error is calculated as the product of the fault tower number minus the terminal tower number multiplied by the tower number span minus the wavefront time extracted by the fault detection device located on the terminal tower from the lightning current waveform captured by the fault detection device and the wave velocity calculated by simulation.

[0087] The formula is:

[0088]

[0089]

[0090] in, , These are the first error and the second error, respectively. , , These are the tower numbers of the starting tower, the faulty tower, and the ending tower on the actual transmission line, respectively. The span for the tower number; The wave velocity calculated in the simulation; , The fault detection devices for the starting and ending towers respectively capture the wavefront time of the lightning current waveform.

[0091] Specifically, the error threshold in this embodiment is 300m.

[0092] Embodiment 2 of the present invention proposes a transmission line fault simulation and test system based on the method described in Embodiment 1 of the present invention, including a test line construction module, a simulation wave velocity calculation module, a simulation test module, and a test module, specifically as follows:

[0093] Test line construction module: used to select two towers from the actual transmission line as the starting tower and the ending tower respectively, and select one tower from all the towers between the starting tower and the ending tower as the fault tower; and to build a test line with the same parameters as the actual transmission line between the starting tower and the ending tower.

[0094] Simulated wave velocity calculation module: used to establish a transient simulation model of the actual transmission line. In the simulation model, a set lightning fault current is injected into the location of the faulty tower. Current sensors are installed at both the starting and ending towers in the simulation model. The wave velocity is calculated by the time difference of the wavefront time detected by the two current sensors.

[0095] Simulation test module: Used to conduct simulation tests on the test line. Two fault monitoring devices are installed on the starting and ending towers of the test line. The fault source is set at the fault tower location. The fault source outputs first a normal power frequency current, then injects a lightning pulse at a peak of the normal power frequency current, and then outputs the insulator string flashover discharge current. The duration of the insulator string flashover discharge current is calculated based on the lightning fault current set during simulation. The amplitude range of the insulator string flashover discharge current includes the amplitude range corresponding to all fault types.

[0096] Test module: If the test line does not trip within the set time range after the injection of a lightning pulse, the threshold for triggering the tripping of the fault detection device on the test line is adjusted according to the amplitude range of different fault types, and the above steps are repeated starting from the output of the fault source; otherwise, the test is normal. The wavefront time of the lightning current waveform captured by the two fault detection devices is obtained, and the corresponding two positioning errors are calculated in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for simulating and testing transmission line faults, characterized in that, include: Two towers are selected from the actual transmission line as the starting tower and the ending tower, respectively. One tower is selected from all the towers between the starting tower and the ending tower as the fault tower. A test line with the same parameters as the actual transmission line between the starting tower and the ending tower is also built. A transient simulation model of the actual transmission line was established. A set lightning fault current was injected into the location of the faulty tower in the simulation model. Current sensors were installed at both the starting and ending towers in the simulation model. Wave velocity is calculated by the time difference between the wavefront times detected by two current sensors. Simulation tests were conducted on the test line. Two fault monitoring devices were installed on the starting and ending towers of the test line. The fault source was set at the location of the faulty tower. The fault source output first output a normal power frequency current, then injected a lightning pulse at a peak of the normal power frequency current, and then output the flashover discharge current of the insulator string. The duration of the flashover discharge current of the insulator string was calculated based on the lightning fault current set during simulation. The amplitude range of the flashover discharge current of the insulator string was set to include the amplitude range corresponding to all fault types. If the test line does not trip within the set time range after the lightning pulse is injected, adjust the tripping threshold of the fault detection device on the test line according to the amplitude range of different fault types, and repeat the above steps starting from the output of the fault source; otherwise, the test is normal. Obtain the wavefront time extracted by the lightning current waveform captured by the two fault detection devices, and calculate the corresponding two positioning errors in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

2. The method for simulating and testing transmission line faults according to claim 1, characterized in that: The establishment of a transient simulation model of the actual transmission line, in which a predetermined lightning fault current is injected at the location of the faulty tower, specifically involves: The transient simulation model is a frequency-dependent electromagnetic transient model. The transient simulation model adopts a dual-power supply topology structure. By adjusting the power angle, the active power and load current are changed to the actual active power and load current. The conductor diameter, split bundle, conductor height, ground wire height and phase spacing adopt the corresponding parameters of the actual transmission line. After the transmission line is operating stably, a set lightning fault current is injected after a set delay period.

3. The method for simulating and testing transmission line faults according to claim 2, characterized in that: The lightning fault current is specifically: The set lightning fault current is obtained by weighting and summing the 8 / 20μs lightning current and the 10 / 350μs lightning current according to the set weights.

4. The method for simulating and testing transmission line faults according to claim 1, characterized in that: The wave velocity is calculated by measuring the time difference between the wavefront times detected by two current sensors, specifically as follows: The wavefront times collected by the two current sensors are obtained, and the location of the fault tower with the midpoint of the transmission line as the reference point is obtained. The wave velocity is obtained by dividing the fault tower location of the reference point by twice the difference between the wavefront times collected by the two current sensors.

5. The method for simulating and testing transmission line faults according to claim 3, characterized in that: The fault source is output as follows: The duration of the fault source's initial output of normal power frequency current ranges from one cycle duration of normal power frequency current to two cycles duration of normal power frequency current. The duration of the flashover discharge current of the insulator string is: the peak moment of the 10 / 350μs lightning current minus the peak moment of the 8 / 20μs lightning current plus the cycle duration of a normal power frequency current. The calculated result is multiplied by the difference between the weights of the 10 / 350μs lightning current and the 8 / 20μs lightning current, plus the cycle duration of a normal power frequency current.

6. The method for simulating and testing transmission line faults according to claim 5, characterized in that: The specific steps for adjusting the threshold of the fault detection device on the test line according to the amplitude range of different fault types are as follows: The set time range is between the cycle duration of one normal power frequency current and the cycle duration of two normal power frequency currents. Fault types include high-resistance faults, low-resistance faults, and metallic grounding faults; The amplitude range of a high-resistance fault is from the first threshold to the second threshold; the amplitude range of a low-resistance fault is from the second threshold to the third threshold. The threshold for metallic grounding faults is above the third threshold. If the circuit breaker does not trip after two cycles of normal power frequency current following the injection of the lightning pulse, the tripping threshold of the fault detection device is lowered. If the current threshold is greater than the third threshold, it is adjusted to the third threshold. If it is greater than the second threshold but less than or equal to the third threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the first threshold. If the circuit breaker trips before reaching a normal power frequency current cycle duration after the lightning pulse is injected, the tripping threshold of the fault detection device is increased. If the current threshold is less than the first threshold, it is adjusted to the first threshold. If it is greater than or equal to the first threshold but less than the second threshold, it is adjusted to the second threshold. Otherwise, it is adjusted to the third threshold.

7. The method for simulating and testing transmission line faults according to claim 6, characterized in that: If the amplitude of the flashover discharge current of the current insulator string is within the amplitude range of a high-resistance fault, then a set background noise is superimposed on the flashover discharge current of the insulator string. The set background noise is a hidden current signal or a corona current signal with a set frequency and amplitude.

8. The method for simulating and testing transmission line faults according to claim 1, characterized in that: The two positioning errors corresponding to the wave velocity calculated by the simulation are as follows: Obtain the tower numbers of the starting tower, fault tower, and termination tower on the actual transmission line. Use the product of the starting tower number minus the span length multiplied by the tower number, minus the wavefront time extracted by the fault detection device located on the starting tower and the wave velocity calculated by simulation as the first error. The second error is calculated as the product of the fault tower number minus the terminal tower number multiplied by the tower number span minus the wavefront time extracted by the fault detection device located on the terminal tower from the lightning current waveform captured by the fault detection device and the wave velocity calculated by simulation.

9. A transmission line fault simulation and test system based on the method of any one of claims 1-8, comprising a test line construction module, a simulation wave velocity calculation module, a simulation test module, and a test module, characterized in that: Test line construction module: used to select two towers from the actual transmission line as the starting tower and the ending tower respectively, and select one tower from all the towers between the starting tower and the ending tower as the fault tower; and to build a test line with the same parameters as the actual transmission line between the starting tower and the ending tower. Simulation wave velocity calculation module: used to establish a transient simulation model of the actual transmission line, inject a set lightning fault current into the location of the fault tower in the simulation model, and install current sensors at the starting tower and the ending tower in the simulation model. Wave velocity is calculated by the time difference between the wavefront times detected by two current sensors. Simulation test module: Used to conduct simulation tests on the test line. Two fault monitoring devices are installed on the starting and ending towers of the test line. The fault source is set at the fault tower location. The fault source outputs first a normal power frequency current, then injects a lightning pulse at a peak of the normal power frequency current, and then outputs the insulator string flashover discharge current. The duration of the insulator string flashover discharge current is calculated based on the lightning fault current set during simulation. The amplitude range of the insulator string flashover discharge current includes the amplitude range corresponding to all fault types. Test module: If the test line does not trip within the set time range after the injection of a lightning pulse, the threshold for triggering the tripping of the fault detection device on the test line is adjusted according to the amplitude range of different fault types, and the above steps are repeated starting from the output of the fault source; otherwise, the test is normal. The wavefront time of the lightning current waveform captured by the two fault detection devices is obtained, and the corresponding two positioning errors are calculated in combination with the wave velocity calculated by simulation. If there is a positioning error exceeding the set error threshold, the fault detection device is unqualified; otherwise, it is qualified, and the qualified fault detection device is used for fault testing.

10. An apparatus comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

11. A computer-readable storage medium storing a computer program thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 8.

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