Traveling wave distance measurement method and module based on online speed measurement

Abstract

The application relates to a kind of online speed measurement based on travelling wave distance measurement method and module, belong to the application field of electric power system automatic control. Including two travelling wave distance measurement modules, each travelling wave distance measurement module is composed of distance measurement CPU, FPGA, double-port RAM, SFP single-mode optical module, AD sampling module, PT / CT conversion module, PWM module, COM communication module. The application has the advantages that: by adopting the hard real-time design without distance measurement CPU participation, the stability of timing time, sampling time and communication delay of two-end travelling wave device is ensured, and the communication delay time is calculated online through the hard real-time algorithm, the distance measurement error caused by time synchronization in the process of double-end travelling wave distance measurement is greatly reduced; by adopting online speed measurement method, the online measurement of different frequency travelling wave velocity is realized, and the distance measurement error caused by inaccurate velocity is reduced; thereby the reliability and accuracy of fault travelling wave distance measurement are improved.

Description

TECHNICAL FIELD

[0001] The application relates to a traveling wave distance measurement method and module based on online speed measurement, and belongs to the field of automatic control of power systems. BACKGROUND

[0002] Traveling wave distance measurement is a method for determining the fault location by using the propagation time of the transient traveling wave generated by the fault on the power line. When a fault occurs in a power system, the fault point will emit traveling waves to both ends of the line, and the traveling waves will propagate on the line at a speed close to the speed of light. By measuring the time difference of the traveling wave reaching the measuring points at both ends of the line, the distance from the fault point to the measuring points at both ends can be calculated, so as to determine the fault location. This method is called double-end distance measurement method. This method needs to determine three data: line length L, traveling wave speed v and time difference △t of the traveling wave reaching the measuring points at both ends. In practical applications, the line length L and the traveling wave speed v are manually set, and the time difference △t is calculated by the time setting function of the global positioning system (GPS). The line length L can be manually measured, but the traveling wave speed v is related to the material, insulating medium, erection mode, environment and traveling wave frequency of the line and is difficult to accurately calculate, which is a main factor affecting the accuracy of traveling wave distance measurement. At the same time, due to the fact that the traveling wave speed v is close to the speed of light, small differences in the time setting of the GPS and the software processing delay of the distance measurement CPU will result in a large fault positioning error. SUMMARY

[0003] In order to solve the two main problems mentioned above, the application provides a traveling wave distance measurement method and module based on online speed measurement for high-voltage transmission lines and important distribution lines with optical fiber communication, especially cable lines that need accurate fault location and mine cable lines that affect personal safety buried deep underground. First, a hard real-time design without the participation of a distance measurement CPU is adopted to ensure the stability of the timing time, sampling time and communication delay of the traveling wave device at both ends, and the communication delay time is calculated online by a hard real-time algorithm. Second, the online speed measurement method is used to realize online real-time measurement of the wave speed of traveling waves of different frequencies.

[0004] In order to achieve the above object, the technical scheme adopted by the present application is as follows: a traveling wave distance measurement module based on online speed measurement, comprising two traveling wave distance measurement modules, each of which is composed of a distance measurement CPU, an FPGA, a dual-port RAM, an SFP single-mode optical module, an AD sampling module, a PT / CT conversion module, a PWM module and a COM communication module; the dual-port RAM realizes data exchange between the distance measurement CPU and the FPGA; the SFP single-mode optical module realizes long-distance optical fiber communication between the two traveling wave distance measurement modules; the AD sampling module realizes traveling wave voltage and current sampling; the PT / CT conversion module realizes traveling wave voltage and current conversion; the PWM module receives a variable frequency pulse wave from the FPGA, realizes pulse wave conditioning and outputs to a voltage transformer used as a power supply; the two traveling wave distance measurement modules are respectively installed in two traveling wave distance measurement devices or two power distribution terminals; the traveling wave distance measurement device or the power distribution terminal provides working power for the traveling wave distance measurement module; and the two traveling wave distance measurement devices or the power distribution terminals are installed at both ends of a power line.

[0005] In a preferred embodiment, the distance measurement CPU and the dual-port RAM are connected through a 16-bit parallel bus, the FPGA and the dual-port RAM are connected through a 16-bit parallel bus, the distance measurement CPU and the COM communication module are connected through a full-duplex serial bus, the FPGA and the AD sampling module are connected through a 16-bit parallel bus, the AD sampling module and the PT / CT conversion module are connected through a high-frequency signal line, the FPGA and the SFP single-mode optical module are connected through a full-duplex differential bus, and the FPGA and the PWM module are connected through a high-speed IO port.

[0006] Further, the FPGA adopts a 100MHz constant temperature crystal oscillator, adopts an AD sampling module with a GSPS high sampling rate, and the AD sampling module is started and sampling data is saved by the FPGA timing, and the sampling frequency is 100MHz; the distance measurement CPU adopts a four-core ARM chip with a main frequency of 1.2GHz or above, and has an algorithmic power of 2TOPS or above.

[0007] In a preferred embodiment, the optical fiber communication between the two traveling wave distance measurement modules adopts a data frame with a uniform format and equal length.

[0008] Specifically, the data frame contains the following data:

[0009] Message type, there are four types: 1-heartbeat sending, 2-heartbeat return, 3-traveling wave distance measurement sending, and 4-traveling wave speed measurement sending;

[0010] This data is valid for message types 1, 3 and 4.

[0011] Opposite side receiving timestamp, this data is valid for message type 2.

[0012] Opposite side sending timestamp, this data is valid for message type 2.

[0013] Local side wave head frequency 1, this data is valid for message type 3, and 0 is filled for other message types;

[0014] Local side wave head time 1, this data is valid for message type 3, and 0 is filled for other message types; ...

[0016] Local side wave head frequency 10, this data is valid for message type 3, and 0 is filled for other message types;

[0017] Local side wave head time 10, this data is valid for message type 3, and 0 is filled for other message types;

[0018] Local side speed measurement wave frequency, this data is valid for message type 4;

[0019] Local side speed measurement wave time, this data is valid for message type 4;

[0020] Frame number, this data is used to judge whether the message is lost or not;

[0021] CRC16, this data is a CRC check code, which is used to judge whether the frame message is correct or not.

[0022] The application also discloses a wave propagation distance measurement method based on online speed measurement, and the calculation of optical fiber communication delay is realized by two wave propagation distance measurement modules.

[0023] A1, the local side FPGA judges whether the timing is 1 minute, if yes, it goes to A2, otherwise it goes to A1;

[0024] A2, the local side FPGA judges whether the local side is sending data, if yes, it goes to A2, otherwise it goes to A3;

[0025] A3, the local side FPGA sends a message of type 1, which contains a local side sending time mark, the local side sending time mark is the 64bit counter value SCount1 of the local side FPGA, and it goes to A4;

[0026] A4, the local side FPGA judges whether a message of type 2 sent by the opposite side is received, if yes, it goes to A5, otherwise if the message is not received within 1 second, it sets a communication exception flag and goes to A1;

[0027] A5, the local side FPGA records the arrival time mark SCount2 of the received message of type 2, and takes the opposite side receiving time mark and the opposite side sending time mark from the message, the opposite side receiving time mark and the opposite side sending time mark are respectively the 64bit counter values PCount1 and PCount2 of the opposite side FPGA, and then the optical fiber communication delay time Tdelay is calculated:

[0028] Tdelay = [(SCount2 - SCount1) - (PCount2 - PCount1)] / 2,

[0029] Calculate the two-end counter deviation value δCnt:

[0030] δCnt = PCount1 - SCount1 - Tdelay,

[0031] Finally update the storage Tdelay and δCnt, and set the communication normal flag to save to the local dual-port RAM, and go to A1.

[0032] In the preferred embodiment, the online measurement method is used to measure the traveling wave speed at different frequencies in real time, and the traveling wave frequency-speed relationship table is generated.

[0033] The specific steps of generating the traveling wave frequency-speed relationship table are as follows:

[0034] B1, the local FPGA initializes the traveling wave frequency ft = 10 kHz, and goes to B2;

[0035] B2, the local FPGA sends a pulse wave with a frequency of ft and a duration of 300 μs, and stores the FPGA clock counter value SCountt of the first rising edge (which serves as the local speed measurement traveling wave time mark), and goes to B3;

[0036] B3, the local FPGA fills the local speed measurement traveling wave frequency Sft = ft, the local speed measurement traveling wave time mark SCountt, and other related data into a type 4 message, and sends it to the opposite traveling wave distance measurement module, and goes to B4;

[0037] B4, the opposite FPGA reads the opposite sampling data PValue, increases the opposite sampling time mark PCount, and writes the opposite sampling data set [PCount, PValue] into the opposite dual-port RAM in a loop; the opposite FPGA determines whether to start the wave recording according to whether the traveling wave mutation variable is greater than the traveling wave threshold value, and if the wave recording is started, generates the traveling wave waveform data (i.e. the three-phase current / voltage traveling wave recording data described below) of 400 μs, including 100 μs before the wave recording is started and 300 μs after the wave recording is started;

[0038] The contralateral distance measurement CPU uses the Karenbauer transform on the latest 400us of three-phase current / voltage traveling wave recording data stored in the contralateral dual-port RAM to obtain the traveling wave line mode component, and then performs Hilbert-Huang Transform (HHT) and differential operation on the line mode component to obtain the amplitude and time relationship of the traveling wave line mode component of different frequencies, wherein PCount is the sampling time corresponding to the PValue of the contralateral sampling data, and PValue is the amplitude of the traveling wave current / voltage collected by the contralateral side; go to B5;

[0039] B5, the contralateral distance measurement CPU judges whether the type 4 message of the ipsilateral side is received, if yes, go to B6, otherwise, B5;

[0040] B6, the contralateral distance measurement CPU analyzes the type 4 message of the ipsilateral side, extracts the speed measurement traveling wave frequency Sft and the time mark SCountt of the ipsilateral side, obtains the time mark SCounttcal corresponding to the speed measurement traveling wave frequency Sft through the relationship between the traveling wave frequency and the time in step B4, and calculates the clock counter difference value ΔCnt1 of the two wave heads:

[0041] ΔCnt1=SCounttcal-(SCountt-δCnt), wherein δCnt is the counter deviation value of both ends obtained in the specific steps of high-precision calculation of the heartbeat signal and the optical fiber communication delay;

[0042] Then, the absolute time difference ΔT1 of the two wave heads is calculated:

[0043] ΔT1=ΔCnt1 / Ffpga, wherein Ffpga is the working frequency of the FPGA (wherein the working frequencies of the FPGA of the ipsilateral side and the contralateral side are equal), and is taken as 100MHz;

[0044] Finally, the traveling wave speed vt is calculated:

[0045] vt=L / ΔT1, wherein L is the length of the line (i.e. the length of the line between the two traveling wave distance measurement modules);

[0046] Go to B7;

[0047] B7, the contralateral distance measurement CPU stores the speed measurement traveling wave frequency Sft and the traveling wave speed vt into the traveling wave frequency-speed relationship table; go to B8;

[0048] B8, the FPGA traveling wave frequency ft of the ipsilateral side is 100kHz, 200kHz, 300kHz, 400kHz, 500kHz, 600kHz, 700kHz, 800kHz, 900kHz in turn, and steps B2-B7 are performed for each traveling wave frequency.

[0049] In a preferred embodiment, the ranging CPUs and the FPGAs of the two traveling wave distance measurement modules cooperatively implement the calculation of the traveling wave distance measurement time.

[0050] The specific steps of the traveling wave distance measurement time calculation are as follows:

[0051] C1, the local FPGA reads the local sampling data SValue, increases the local sampling time mark SCount, and cyclically writes the local sampling data set [SCount, SValue] into the local dual-port RAM1 area, and goes to C2;

[0052] C2, the local FPGA judges whether the traveling wave mutation variable is greater than the traveling wave threshold value, and if yes, the traveling wave recording is started, and goes to C3, otherwise, goes to C1;

[0053] C3, the local FPGA stores the complete traveling wave waveform data of 400 μs before the recording start and 300 μs after the recording start into the local dual-port RAM1 area, stops writing into the local dual-port RAM1 area, and switches to cyclically write the traveling wave data into the local dual-port RAM2 area, and goes to C4;

[0054] C4, the local ranging CPU adopts the Karenbauer transform on the latest 400 μs of three-phase current traveling wave recording data in the local dual-port RAM1 area to obtain the traveling wave line module component, and then performs the Hilbert-Huang Transform (HHT) and differential operation on the traveling wave line module component to obtain the amplitude and time relationship of different frequency traveling wave components; in the 10 frequency bands [10 kHz, 100 kHz), [100 kHz, 200 kHz),..., [900 kHz, 1000 kHz) range, each frequency point with the maximum amplitude and greater than the traveling wave threshold value is found, and the local frequency data set [Sfi, SCountSti] is recorded, where i = 1-10, Sfi is the local frequency value (i.e. the local wave head frequency), and SCountSti is the local wave head time mark, the wave head time mark of the frequency point with the amplitude less than the traveling wave threshold value is cleared to 0, and goes to C5;

[0055] C5, the local ranging CPU fills the data of the local frequency data set into the type 3 message, and sends it to the opposite traveling wave distance measurement module through the local FPGA, and goes to C6;

[0056] C6, the local ranging CPU judges whether the opposite type 3 message is received, and if yes, goes to C7, otherwise, if the message is still not received within 1 second, the ranging time invalid flag is set;

[0057] C7, the opposite side type 3 message is parsed by the local ranging CPU, and the opposite side frequency data set [Pfi, PCountSti] is obtained, compared with the local frequency data set [Sfi, SCountSti], the local wave head time mark SCountSt, the opposite wave head time mark PCountSt and the wave head frequency f are obtained, which are equal in frequency value, minimum in frequency value and different in wave head time mark, the counter difference value of the two wave head time marks is calculated first:

[0058] △Cnt2=SCountSt-(PCountSt-δCnt), wherein δCnt is the counter deviation value of the two ends;

[0059] Then, the absolute time difference △T2 of the two wave heads is calculated:

[0060] △T2=△Cnt2 / Ffpga; wherein Ffpga is the working frequency of FPGA, which is 100MHz;

[0061] Finally, go to C8;

[0062] C8, the local ranging CPU calculates the distance x from the traveling wave module on the local side to the fault point according to the wave head frequency f, and finds the closest traveling wave speed v from the traveling wave frequency-speed relationship table.

[0063] The present application has the advantages that: the present application proposes a traveling wave distance measurement method and module based on online speed measurement for high-voltage transmission lines and important distribution lines with optical fiber communication, especially cable lines buried underground that need accurate fault positioning and mine cable lines that affect personal safety. The stability of the timing time, sampling time and communication delay of the two-end traveling wave device is ensured by using a hard real-time design without the participation of a ranging CPU, and the communication delay time is calculated online by a hard real-time algorithm, which greatly reduces the ranging error caused by time synchronization in the two-end traveling wave distance measurement process. The online measurement of different frequency wave speeds is realized by using the online speed measurement method, which reduces the ranging error caused by inaccurate wave speed. Therefore, the reliability and accuracy of the fault traveling wave distance measurement are improved. Since the two-side devices in the present application can calculate the fault distance independently, there is no need to transmit the traveling wave recording data to the platform for processing, thereby simplifying the system design process and saving costs. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 It is a hardware architecture diagram of the traveling wave distance measurement module based on online speed measurement of the present application;

[0065] Figure 2 It is a communication message format diagram of the present application;

[0066] Figure 3This is a flowchart of the FPGA heartbeat signal and fiber optic communication delay calculation for the present invention;

[0067] Figure 4 This is a flowchart of the online measurement process for traveling wave velocity of the present invention;

[0068] Figure 5 This is a flowchart of the traveling wave ranging calculation of the present invention. Detailed Implementation

[0069] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0070] like Figure 1 The hardware architecture diagram of the traveling wave ranging module based on online speed measurement is shown. It includes two traveling wave ranging modules, each consisting of a dual-end traveling wave ranging motherboard (traveling wave board 1 and traveling wave board 2) and various modules integrated into the dual-end traveling wave ranging motherboard. Each traveling wave ranging module consists of a ranging CPU, FPGA, dual-port RAM, SFP single-mode optical module, AD sampling module, PT / CT conversion module, PWM module, and COM communication module. The dual-port RAM enables large-scale data exchange between the ranging CPU and FPGA. The SFP single-mode optical module enables long-distance fiber optic communication between two traveling wave ranging modules. The AD sampling module performs traveling wave voltage and current sampling, and the PT / CT conversion module performs traveling wave voltage and current conversion. The PWM module receives variable frequency pulse waves from the FPGA, conditions the pulse waves, and outputs them to a voltage transformer used as a power supply (e.g., a phase-to-phase PT or a dedicated PT, installed near the traveling wave ranging module; phase-to-phase PT refers to a voltage transformer between different phases, and dedicated PT refers to a voltage transformer specifically used for the traveling wave ranging module of this invention). After the pulse waves are output to the voltage transformer, they are coupled to the line to generate traveling waves of different frequencies for speed measurement. The COM communication module is used for communication between the ranging CPU and other local boards (such as the power distribution terminal motherboard) or devices (such as monitoring equipment). For example, the power distribution terminal motherboard sends configuration information (including traveling wave threshold value, etc.) to the traveling wave ranging module. The traveling wave ranging module can also send fault traveling wave waveform and other information to the monitoring equipment through the ranging CPU. Two traveling wave ranging modules can be installed in two traveling wave ranging devices or two power distribution terminals (as two ends). The traveling wave ranging devices or power distribution terminals provide operating power to the traveling wave ranging modules. The two traveling wave ranging devices or power distribution terminals are installed at both ends of a power line and are connected by a single-mode optical fiber.

[0071] The phase-to-phase PT or dedicated PT mentioned above is a primary high-voltage PT, while the PT / CT conversion module further transforms the primary high-voltage PT signal into traveling wave voltage and current. The AD sampling module then acquires the traveling wave signal transformed by the PT / CT conversion module and sends it to the FPGA for processing.

[0072] In the present application, the traveling wave is divided into the speed measurement traveling wave sent by the FPGA and the fault traveling wave sent by the fault location. The collection path of the speed measurement traveling wave sent by the FPGA includes: the speed measurement traveling wave (impulse wave) sent by the FPGA on one side - the PWM module on one side - the voltage transformer on one side - the line - the voltage / current transformer on the other side - the PT / CT conversion module on the other side - the AD sampling module on the other side - the FPGA on the other side to save the traveling wave waveform. The collection path of the fault traveling wave sent by the fault location includes: the fault traveling wave sent by the fault location - the line on both sides - the voltage / current transformer on both sides - the PT / CT conversion module on both sides - the AD sampling module on both sides - the FPGA on both sides to save the traveling wave waveform.

[0073] In the present application, the voltage transformer is used for coupling from the low-voltage side to the high-voltage side, and the voltage transformer or the current transformer is used for coupling from the high-voltage side to the low-voltage side.

[0074] In the present application, the two ends include the side and the opposite side.

[0075] The distance measurement CPU (central processing unit) and the dual-port RAM (random access memory) are connected through a 16-bit parallel bus, the distance measurement CPU and the COM communication module are connected through a full-duplex serial bus, the FPGA (field programmable logic gate array processor) and the AD sampling module are connected through a 16-bit parallel bus, the AD (analog-to-digital conversion) sampling module and the PT / CT conversion module (where PT refers to voltage conversion and CT refers to current conversion) are connected through a high-frequency signal line, the FPGA and the SFP single-mode optical module are connected through a full-duplex differential bus, and the FPGA and the PWM (pulse width modulation) module are connected through a high-speed IO port.

[0076] In order to achieve high timing accuracy and stable high sampling rate, the FPGA uses a 100MHz high-precision constant temperature crystal oscillator, a flash type AD sampling module with GSPS high sampling rate, and the FPGA timing starts the AD sampling module to sample and save the sampling data, and the sampling frequency is 100MHz; in order to realize the analysis requirement of the traveling wave recording wave form data, the distance measurement CPU uses a 1.2GHz or above four-core ARM domestic chip with a computing power of 2TOPS (processor operation ability unit) or above.

[0077] Figure 2 The communication message format diagram of the present application, in order to simplify the communication message processing and stabilize the message processing time, the optical fiber communication between the two traveling wave distance measurement modules adopts a uniform format data frame with equal length, and the data frame contains the following data:

[0078] Message type, there are four kinds: 1-Heartbeat sending (as type 1), 2-Heartbeat return (as type 2), 3-traveling wave ranging sending (as type 3), 4-traveling wave speed measurement sending (as type 4);

[0079] Local sending time stamp, this data is valid for message types 1, 3 and 4, if it is other message type, then fill 0 in local sending time stamp;

[0080] Opposite receiving time stamp, this data is valid for message type 2, if it is other message type, then fill 0 in opposite receiving time stamp;

[0081] Opposite sending time stamp, this data is valid for message type 2, if it is other message type, then fill 0 in opposite sending time stamp;

[0082] Local wave head frequency 1, this data is valid for message type 3, if it is other message type, then fill 0 in local wave head frequency 1;

[0083] Local wave head time stamp 1, this data is valid for message type 3, if it is other message type, then fill 0 in local wave head time stamp 1; ...

[0085] Local wave head frequency 10, this data is valid for message type 3, if it is other message type, then fill 0 in local wave head frequency 10;

[0086] Local wave head time stamp 10, this data is valid for message type 3, if it is other message type, then fill 0 in local wave head time stamp 10;

[0087] Local speed measurement traveling wave frequency, this data is valid for message type 4, if it is other message type, then fill 0 in local speed measurement traveling wave frequency;

[0088] Local speed measurement traveling wave time stamp, this data is valid for message type 4, if it is other message type, then fill 0 in local speed measurement traveling wave time stamp;

[0089] Frame sequence number, each frame message is added by 1 according to sending order, this data is used to judge whether the message is lost or not;

[0090] CRC16, this data is CRC check code, used to judge whether the frame message is correct or not.

[0091] The above local wave head frequency and local wave head time stamp are 10 respectively, corresponding to 10 frequency bands [10kHz, 100kHz), [100kHz, 200kHz),..., [900kHz, 1000kHz) range respectively find the frequency point with maximum amplitude and greater than the traveling wave threshold value, record the frequency data group.

[0092] Figure 3is the FPGA heartbeat signal and fiber communication delay flow chart. In order to improve the precision of timing and communication delay calculation, the hard real-time FPGA clock counter is used to time (FPGA built-in clock counter) and calculate the fiber communication delay time without the participation of the ranging CPU. The specific steps of the traveling wave ranging module FPGA to realize the high-precision calculation of the heartbeat signal and fiber communication delay are as follows:

[0093] A1, the local FPGA determines whether the timing is 1 minute, if yes, go to A2, otherwise go to A1;

[0094] A2, the local FPGA determines whether the local side is sending data, if yes, go to A2, otherwise go to A3;

[0095] A3, the local FPGA sends a message of type 1, which contains the local sending time stamp, i.e. the 64-bit counter value SCount1 of the local FPGA when sending the message of type 1, and goes to A4;

[0096] A4, the local FPGA determines whether it has received the message of type 2 sent by the opposite side, if yes, go to A5, otherwise if the message has not been received within 1 second, set the communication abnormal flag and go to A1;

[0097] A5, the local FPGA records the arrival time stamp SCount2 of the received message of type 2, and takes out the opposite side's receiving time stamp and sending time stamp from the message, which are the 64-bit counter values PCount1 and PCount2 of the opposite FPGA, and then calculates the fiber communication delay time Tdelay:

[0098] Tdelay = [(SCount2-SCount1)-(PCount2-PCount1)] / 2,

[0099] Calculate the counter deviation value δCnt (where the counter refers to the FPGA clock counter of the two traveling wave ranging modules):

[0100] δCnt = PCount1-SCount1-Tdelay,

[0101] Finally, update the storage Tdelay and δCnt, and set the communication normal flag to save to the local dual-port RAM, and go to A1.

[0102] The basic principle is that the local FPGA sends a heartbeat message, and after receiving the heartbeat message sent by the local side, the opposite side FPGA also returns a heartbeat message.

[0103] Wherein step A1 is determined by the local FPGA clock counter whether 1 minute is to (start running, the time is calculated by FPGA clock counter), every 1 minute is performed once above A1-A5 step execution.

[0104] In step A2, it is judged whether data is being sent, specifically, it is judged whether the local side is sending data, and the sent data can be at least one of message types 1, 3 and 4.

[0105] In step A4, 1 second means 1s (including 1s) from the local sending time mark.

[0106] In step A5, the message arrival time mark SCount2 is recorded by the local FPGA clock counter, the opposite side receiving time mark is recorded by the opposite FPGA clock counter, and the opposite side sending time mark is recorded by the opposite FPGA clock counter.

[0107] Wherein Tdelay, δCnt, communication normal flag, communication abnormal flag are saved in the local double-port RAM.

[0108] Figure 4 It is a traveling wave velocity online measurement flow chart. In order to improve the traveling wave distance measurement accuracy, overcome the influence of line differentiation and aging and running environment change on the traveling wave velocity, the online measurement method is used to measure the traveling wave velocity under different frequencies in real time, and the traveling wave frequency-velocity relationship table is generated; this traveling wave velocity online measurement step can be automatically executed once every 0.5-30 days, and the specific steps are as follows:

[0109] B1, the local FPGA initializes the traveling wave frequency ft=10kHz, and goes to B2;

[0110] B2, the local FPGA sends a pulse wave with a frequency of ft and a duration of 300us, and stores the FPGA clock counter value SCountt of the first rising edge (which is the local speed measurement traveling wave time mark), and goes to B3;

[0111] B3, the local FPGA fills the local speed measurement traveling wave frequency Sft=ft, the local speed measurement traveling wave time mark SCountt and other related data into the type 4 message, and sends it to the opposite traveling wave distance measurement module, and goes to B4;

[0112] B4, the opposite FPGA reads the opposite sampling data PValue, increases the opposite sampling time mark PCount, and cyclically writes the opposite sampling data group [PCount, PValue] into the opposite dual-port RAM; the opposite FPGA determines whether to start the wave recording according to whether the traveling wave mutation variable is greater than the traveling wave threshold value, and if the wave recording is started, generates the traveling wave waveform data (i.e., the traveling wave recording data) of 400 μs before the wave recording is started and 300 μs after the wave recording is started, i.e., a total of 400 μs;

[0113] The opposite distance measurement CPU obtains the traveling wave line mode component by using the Karenbauer transform on the latest 400 μs of the traveling wave recording data of the three-phase current / voltage stored in the opposite dual-port RAM, and obtains the amplitude and time relationship of the traveling wave line mode component of different frequencies after the Hilbert-Huang Transform (HHT) and differential operation are performed on the line mode component, wherein PCount is the sampling time corresponding to the opposite sampling data PValue, and PValue is the amplitude of the traveling wave current / voltage collected by the opposite side; go to B5;

[0114] B5, the opposite distance measurement CPU determines whether the local type 4 message is received, and if yes, goes to B6, otherwise, B5;

[0115] B6, the opposite distance measurement CPU analyzes the local type 4 message, extracts the local speed measurement traveling wave frequency Sft and the local speed measurement traveling wave time mark SCountt, obtains the time mark SCounttcal corresponding to the local speed measurement traveling wave frequency Sft through the relationship between the traveling wave frequency and the time in step B4, and first calculates the clock counter difference value ΔCnt1 of the two wave heads:

[0116] ΔCnt1 = SCounttcal - (SCountt - δCnt), wherein δCnt is the two-end counter deviation value obtained in the specific steps of the high-precision calculation of the heartbeat signal and the fiber communication delay;

[0117] Then, the absolute time difference ΔT1 of the two wave heads is calculated:

[0118] ΔT1 = ΔCnt1 / Ffpga, wherein Ffpga is the working frequency of the FPGA (wherein the working frequencies of the FPGA of the local side and the opposite side are equal), and is taken as 100 MHz;

[0119] Finally, the traveling wave speed vt is calculated:

[0120] vt = L / ΔT1, wherein L is the line length (i.e., the length of the line between the two traveling wave distance measurement modules);

[0121] Go to B7;

[0122] B7, the opposite side distance measurement CPU stores the local side velocity measurement wave frequency Sft and wave velocity vt into the wave frequency-velocity relationship table; go to B8;

[0123] B8, the local side FPGA wave frequency ft is sequentially set as 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz and 900 kHz, and the steps B2-B7 are performed for each wave frequency.

[0124] In this paper, the wave is a current wave or a voltage wave; usually, it is a current wave, and the sampling data and amplitude are current values.

[0125] In this application, the two sides are independent of each other, and the speed measurement wave is sent from one side, and the frequency-velocity table is analyzed and generated on the other side; that is, the wave is sent from the local side, and the frequency-velocity table is generated on the opposite side (see steps B1-B8); similarly, the wave is sent from the opposite side, and the frequency-velocity table is generated on the local side (refer to steps B1-B8).

[0126] In step B2, the stored value SCountt of the local side FPGA counter of the first rising edge in the 300 μs pulse wave is stored.

[0127] In step B3, the relevant data includes the frame number.

[0128] When the wave distance measurement module is started and in use, the AD sampling module realizes real-time sampling of the line wave voltage or wave current under the control of the FPGA. In step B4, the opposite side sampling data PValue is the instantaneous value of the wave current or the instantaneous value of the wave voltage collected by the opposite side (i.e. the wave current / voltage amplitude mentioned above), and the opposite side sampling time PCount is the sampling time corresponding to the opposite side sampling data PValue (counted by the opposite side FPGA clock counter); during real-time sampling, the opposite side sampling data and the opposite side sampling time at different sampling times form the opposite side sampling data set.

[0129] In step B4, the opposite side sampling data PValue is collected by the opposite side AD sampling module and sent to the opposite side FPGA, and the opposite side FPGA determines whether to start recording the wave according to whether the wave mutation is greater than the wave threshold value. The wave threshold value can be 0.2 times the rated current (for example, the wave threshold value can be 1A), and the rated current refers to the rated current of the FPGA on both sides, wherein the rated currents of the FPGAs on both sides are equal. The wave threshold value can be sent to the FPGA by the distance measurement CPU through the dual-port RAM.

[0130] In step B4, the traveling wave mutation variable refers to the difference between the real-time contralateral sampling data PValue and the maximum value of the contralateral sampling data PValue 100 μs before the transmission of the 10 kHz pulse wave of the local speed measurement traveling wave. The maximum value of the contralateral sampling data PValue 100 μs before the transmission of the 10 kHz pulse wave of the local speed measurement traveling wave refers to the maximum value of the contralateral sampling data in 100 μs before the transmission of the 10 kHz pulse wave of the local speed measurement traveling wave without any fault traveling wave or other traveling wave on the line.

[0131] After the local speed measurement traveling wave is transmitted, if the traveling wave mutation variable corresponding to a sampling time at the contralateral side is greater than the traveling wave threshold value (and the premise is that the traveling wave mutation variables of the previous sampling times are not greater than the traveling wave threshold value), the contralateral FPGA starts to record the traveling wave and generates the traveling wave waveform data 400 μs before the start of recording and 300 μs after the start of recording, and then stores the traveling wave waveform data in the contralateral dual-port RAM.

[0132] In step B4, the Karenbauer transform, the Hilbert-Huang transform and the differential operation are all prior art, and the reference (Zhou Zhitong, et al. A Fault Traveling Wave Distance Measurement Method for Transmission Lines Based on Frequency Selection [J]. Electrical Technology, 2024, 25(2): 31-36) is executed. After the local side transmits the 10 kHz, 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz and 900 kHz speed measurement traveling waves, the contralateral FPGA records the 400 μs three-phase current / voltage traveling wave recording data, respectively, and then stores the traveling wave recording data in the contralateral dual-port RAM, and then the contralateral distance measurement CPU obtains the relationship between the amplitude (current amplitude or voltage amplitude) of the traveling wave line mode component at different frequencies and the time (i.e. the wave head time mark); specifically, the contralateral distance measurement CPU obtains the current amplitude or voltage amplitude in the 400 μs three-phase current / voltage traveling wave recording data corresponding to different frequencies and the contralateral sampling time mark (as the wave head time mark) corresponding to the current amplitude or voltage amplitude by Karenbauer transform, Hilbert-Huang transform and differential operation for 10 kHz, 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz and 900 kHz frequencies, respectively.

[0133] In step B5, the contralateral FPGA receives the local side type 4 message and sends the message to the contralateral distance measurement CPU. Then the contralateral distance measurement CPU judges whether the local side type 4 message is received.

[0134] In step B6, SCountt and SCounttcal are two wave head time marks. The time mark SCounttcal is obtained according to the relationship between the wave frequency and time and the local speed measurement wave frequency Sft. Specifically, the wave frequency corresponding to the wave head time mark is found in the wave frequency-time relationship table, and the wave head time mark value is assigned to SCounttcal.

[0135] In step B7, the local speed measurement wave frequency Sft includes 10 kHz, 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, and 900 kHz. For each local speed measurement wave frequency Sft, the corresponding wave velocity vt is calculated by step B6, and then stored in the wave frequency-velocity relationship table, which is generated and stored by the opposite side distance measurement CPU.

[0136] In step B8, when steps B2-B7 are performed for each wave frequency, the wave mutation variable refers to the real-time opposite side sampling data PValue, and the difference between the maximum value of the opposite side sampling data PValue 100 μs before the pulse wave transmission with the local speed measurement wave frequency of 10 kHz. In addition, when steps B2-B7 are performed for all wave frequencies (including 10 kHz), the time range corresponding to the 400 μs three-phase current / voltage wave recording data does not have any repetition, preventing the 400 μs three-phase current / voltage wave recording data corresponding to different frequencies from interfering with each other.

[0137] Figure 5 is a wave distance measurement calculation flowchart. In order to improve the calculation accuracy of the distance measurement time, the hard real-time FPGA clock counter is used to count the sampling value time mark and start and stop the wave recording data storage, and the distance measurement CPU completes the data analysis of the wave recording waveform without strong real-time. The distance measurement CPUs and FPGAs of the two wave distance measurement modules cooperate to realize high-precision calculation of the wave distance measurement time. The following steps are executed continuously in real time after the wave distance measurement module is started, ensuring that the fault distance can be detected as soon as possible after a fault occurs on the line. The specific steps are as follows:

[0138] C1, the local FPGA reads the local sampling data SValue, increases the local sampling time mark SCount, and writes the local sampling data set [SCount, SValue] into the local dual-port RAM1 area in a loop, and goes to C2; wherein SCount is the FPGA counter value (the sampling time corresponding to the local sampling data SValue), and SValue is the local collected wave current / voltage amplitude;

[0139] C2, the local FPGA judges whether the wave mutation variable is greater than the wave threshold value, and if so, the wave recording is started, and goes to C3, otherwise, goes to C1;

[0140] C3, in order to better analyze the traveling wave waveform, while considering the capacity of the local double-port RAM, the local FPGA stores the complete traveling wave waveform data of 400 μs before the recording wave is started and 300 μs after the recording wave is started into the local double-port RAM1 area, stops writing into the local double-port RAM1 area, and switches to cyclically write the traveling wave data (local sampling data SValue, local sampling time mark SCount) into the local double-port RAM2 area, so as to prevent the newly collected traveling wave data from being overwritten, and goes to C4;

[0141] C4, the local distance measurement CPU uses the Karenbauer transform on the latest 400 μs of three-phase current traveling wave recording data (i.e. traveling wave waveform data) in the local double-port RAM1 area to obtain the traveling wave line mode component, and then performs the Hilbert-Huang Transform (HHT) and differential operation on the traveling wave line mode component to obtain the amplitude and time relationship of different frequency traveling wave components; in the 10 frequency bands [10 kHz, 100 kHz), [100 kHz, 200 kHz),..., [900 kHz, 1000 kHz) range, each frequency point with the maximum amplitude (referring to the current amplitude or voltage amplitude) and greater than the traveling wave threshold value is found, and the local frequency data set [Sfi, SCountSti] is recorded, where i = 1-10, Sfi is the local frequency value, and SCountSti is the local wave head time mark (for a certain frequency value, the wave head time mark corresponds to the time when the 400 μs traveling wave recording data amplitude maximum point under the frequency value), and the wave head time mark of the frequency point with the amplitude less than the traveling wave threshold value is 0, and goes to C5;

[0142] C5, the local distance measurement CPU fills the local frequency data set and related data into the type 3 message, and sends it to the opposite traveling wave distance measurement module through the local FPGA, and goes to C6;

[0143] C6, the local distance measurement CPU judges whether the opposite type 3 message is received, if yes, goes to C7, otherwise, if the message is still not received within 1 second, sets the distance measurement time invalid flag;

[0144] C7, the opposite side type 3 message is parsed by the CPU of the local side ranging, and the opposite side frequency data group [Pfi, PCountSti] is obtained, wherein Pfi is the opposite side frequency value, and PCountSti is the opposite side wave head time mark; the opposite side frequency data group [Pfi, PCountSti] is compared with the local side frequency data group [Sfi, SCountSti], and the local side wave head time mark SCountSt, the opposite side wave head time mark PCountSt, and the wave head frequency f (the wave head frequency is the local side frequency value which is equal in frequency value, minimum in frequency value, and not equal to 0 in wave head time mark) are obtained, and the counter difference value △Cnt2 of the two wave head time marks is calculated first:

[0145] △Cnt2=SCountSt-(PCountSt-δCnt), wherein δCnt is the counter deviation value of two ends obtained in the specific steps of high-precision calculation of the heartbeat signal and the optical fiber communication delay;

[0146] Then, the absolute time difference △T2 of the two wave heads is calculated:

[0147] △T2=△Cnt2 / Ffpga; wherein Ffpga is the working frequency of the FPGA, and is 100 MHz;

[0148] Finally, go to C8;

[0149] C8, the local side ranging CPU finds the wave propagation speed v most similar to the wave head frequency f from the wave propagation frequency-speed relationship table stored in the local side ranging CPU (specifically, the wave propagation frequency most similar to the wave head frequency f is found in the wave propagation frequency-speed relationship table first, and then the corresponding vt value is taken as the wave propagation speed v), and the distance x of the fault point to the local side wave propagation ranging module is calculated: x=[L+△T2*v] / 2.

[0150] In the application, when a fault occurs at a certain point in a line, the fault point sends transient traveling waves with very short time to both ends of the line, the ranging modules at both ends detect the traveling waves, the traveling waves sent by the same fault point propagate in two directions, and the frequency components are the same (and contain multiple frequencies); the local side frequency data group [Sfi, SCountSti] and the opposite side frequency data group [Pfi, PCountSti] are obtained by referring to steps C1-C4, and the distance of the fault point to the wave propagation ranging module is calculated by referring to steps C5-C8.

[0151] When the traveling wave distance measurement module is started and in use, the AD sampling module realizes real-time sampling of the line traveling wave voltage or current under the control of the FPGA. In step C1, the local sampling data SValue is collected by the local AD sampling module and sent to the local FPGA. The local sampling data SValue is the instantaneous value of the traveling wave current or voltage collected by the local side (i.e. the amplitude of the traveling wave current / voltage mentioned above), and the local sampling time SCount is the sampling time corresponding to the local sampling data SValue (counted by the local FPGA clock counter). During real-time sampling, the local sampling data and the local sampling time at different sampling times form a local sampling data set.

[0152] In step C2, the local FPGA determines whether to start the traveling wave recording according to whether the traveling wave mutation is greater than the traveling wave threshold. The traveling wave threshold is the same as in step B4. In step C2, the traveling wave mutation refers to the difference between the real-time local sampling data SValue and the maximum value of the opposite sampling data PValue 100 μs before the 10 kHz pulse wave transmission. The maximum value of the opposite sampling data PValue 100 μs before the 10 kHz pulse wave transmission refers to the maximum value of the opposite sampling data in the aforementioned traveling wave speed measurement step, before the local FPGA transmits the 10 kHz traveling wave for speed measurement, and under the condition that the line does not contain any fault traveling wave or other traveling wave.

[0153] When the traveling wave mutation corresponding to a certain sampling time of the local side is greater than the traveling wave threshold (and the prerequisite is that the traveling wave mutation of the previous sampling time is not greater than the traveling wave threshold), the local FPGA starts the traveling wave recording and generates the traveling wave waveform data 100 μs before the start of the traveling wave recording and 300 μs after the start of the traveling wave recording, a total of 400 μs, and then stores the traveling wave waveform data in the local dual-port RAM1.

[0154] The local side dual-port RAM is divided into two areas: local side dual-port RAM 1 area and local side dual-port RAM 2 area, and the opposite side dual-port RAM is also divided into two areas. Since the above steps are continuously executed in real time after the start of the traveling wave distance measurement module, the latest 400 μs of three-phase current traveling wave recording data in the local side dual-port RAM 1 area is switched back to the local side FPGA for cyclic writing of the local side sampling data group [SCount, SValue] by the local side dual-port RAM 1 after the local side distance measurement CPU completes the analysis to obtain the frequency point and the corresponding wave head timestamp data. When the recording condition in step C2 is reached, but the latest 400 μs of three-phase current traveling wave recording data in the local side dual-port RAM 1 area has not been analyzed in the local side distance measurement CPU to obtain the frequency point and the corresponding wave head timestamp data, the updated 400 μs of three-phase current traveling wave recording data is stored in the local side dual-port RAM 2 area, and the traveling wave recording data is also analyzed by the local side distance measurement CPU to obtain the frequency point and the corresponding wave head timestamp data. In actual use, the local side dual-port RAM 1 area and the local side dual-port RAM 2 area are sufficient to cope with the recording condition in step C2. The latest 400 μs of three-phase current traveling wave recording data is stored in the local side dual-port RAM 1 area.

[0155] In this paper, when the traveling wave data is cyclically written into the dual-port RAM, it has formed the traveling wave waveform data. The recording refers to the traveling wave waveform data in a certain time range (400 μs) as a whole for analysis by the distance measurement CPU.

[0156] In step C4, the traveling wave waveform data itself is a waveform data composed of multiple frequencies, and the amplitude and time relationship of different frequency (for example, from 1, 2, 3, 4, 5...1000 kHz) traveling wave components are obtained by Karenbauer transformation, Hilbert-Huang transformation and differential operation. The meanings of amplitude and time in the amplitude and time relationship of different frequency traveling wave components are the same as those in step B4. The meaning of the traveling wave threshold in step C4 is the same as that in step C2. Karenbauer transformation, Hilbert-Huang transformation and differential operation are prior art, and the reference literature (Zhou Zhitong, et al. A fault traveling wave distance measurement method for transmission lines based on frequency selection [J]. Electrical Technology, 2024, 25(2): 31-36) is executed.

[0157] In step C5, the relevant data includes the frame sequence number.

[0158] In step C6, since fault location is performed on both sides at the same time, the opposite side also performs and obtains the opposite side frequency data set [Pfi, PCountSti] according to steps C1-C4, and then sends the opposite side frequency data set to the current side. The FPGA of the current side receives the type 3 message of the opposite side, and sends the type 3 message to the current side fault location CPU. Then the current side fault location CPU judges whether the type 3 message of the opposite side is received.

[0159] In step C7, the current side wave head time SCountSt, the opposite side wave head time PCountSt and the wave head frequency f with the minimum frequency value are selected, because the data with the small frequency value has small attenuation, and the fault location calculation is more accurate. In step C7, the frequency value equal means that a frequency value (i.e. frequency point) of the current side frequency data set is equal to a frequency value (i.e. frequency point) of the opposite side frequency data set. The frequency value equal, the frequency value minimum and the wave head time not equal to 0 means that the minimum current side frequency value of the equal frequency values of the current side frequency data set and the opposite side frequency data set, and the wave head time corresponding to the minimum current side frequency value is not equal to 0 (the frequency value is the finally selected current side frequency value), and the wave head time corresponding to the equal opposite side frequency value of the minimum current side frequency value is not equal to 0 (the frequency value is the finally selected opposite side frequency value). The two wave head times means the current side wave head time SCountSt (which is the wave head time corresponding to the finally selected current side frequency value), and the opposite side wave head time PCountSt (which is the wave head time corresponding to the finally selected opposite side frequency value).

[0160] In step C8, L is the length of the line between the two traveling wave fault location modules.

[0161] The above embodiments are only used to illustrate the technical solutions of the present application, and those skilled in the art should understand that the above embodiments do not limit the present application in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A traveling wave ranging module based on online velocity measurement, characterized in that, The system comprises two traveling wave ranging modules. Each module consists of a ranging CPU, FPGA, dual-port RAM, SFP single-mode optical module, AD sampling module, PT / CT conversion module, PWM module, and COM communication module. The dual-port RAM enables data exchange between the ranging CPU and FPGA. The SFP single-mode optical module enables long-distance fiber optic communication between the two traveling wave ranging modules. The AD sampling module samples traveling wave voltage and current. The PT / CT conversion module converts traveling wave voltage and current. The PWM module receives variable frequency pulse waves from the FPGA, conditions the pulse waves, and outputs them to a voltage transformer used as a power supply. The two traveling wave ranging modules are installed in two traveling wave ranging devices or two power distribution terminals, respectively. The traveling wave ranging devices or power distribution terminals provide operating power to the traveling wave ranging modules. The two traveling wave ranging devices or power distribution terminals are installed at both ends of a power line. The fiber optic communication between the two traveling wave ranging modules uses data frames of equal length in a unified format. The data frame contains the following data: There are four message types: 1-heartbeat transmission, 2-heartbeat return, 3-traveling wave ranging transmission, and 4-traveling wave velocity measurement transmission. This side sends a time stamp; this data is valid for message types 1, 3, and 4. The receiving time stamp is valid for message type 2. The other side sends a timestamp; this data is valid for message type 2. The local wavefront frequency is 1. This data is valid for message type 3. For other message types, fill in 0. The local wavefront time stamp is 1. This data is valid for message type 3. For other message types, fill in 0. ... The local wavefront frequency is 10. This data is valid for message type 3. For other message types, fill in 0. The wavefront time stamp is 10. This data is valid for message type 3. For other message types, fill in 0. This side's speed measurement traveling wave frequency, this data is valid for message type 4; This side's velocity traveling wave time stamp, this data is valid for message type 4; Frame sequence number; this data is used to determine whether a message has been lost. CRC16, this data is the CRC checksum, used to determine whether this frame of data is correct.

2. The traveling wave ranging module based on online velocity measurement according to claim 1, characterized in that, The ranging CPU and dual-port RAM, and the FPGA and dual-port RAM are connected via a 16-bit parallel bus. The ranging CPU and the COM communication module are connected via a full-duplex serial bus. The FPGA and the AD sampling module are connected via a 16-bit parallel bus. The AD sampling module and the PT / CT conversion module are connected via a high-frequency signal line. The FPGA and the SFP single-mode optical module are connected via a full-duplex differential bus. The FPGA and the PWM module are connected via a high-speed I / O port.

3. The traveling wave ranging module based on online velocity measurement according to claim 1, characterized in that, The FPGA uses a 100MHz temperature-controlled crystal oscillator and an AD sampling module with a high sampling rate of GSPS. The FPGA starts the AD sampling module at regular intervals to sample and save the sampled data, with a sampling frequency of 100MHz. The ranging CPU uses a quad-core ARM chip with a main frequency of 1.2GHz or higher and has a computing power of more than 2TOPS.

4. A traveling wave ranging method based on online velocity measurement, characterized in that, The calculation of fiber optic communication delay is implemented using an FPGA with two traveling wave ranging modules. The specific steps are as follows: A1. The FPGA on this side determines whether the 1-minute timer has elapsed. If so, proceed to A2; otherwise, proceed to A1. A2. The FPGA on this side determines whether it is sending data. If so, proceed to A2; otherwise, proceed to A3. A3. The local FPGA sends a message of type 1, which contains a local transmission time stamp. The local transmission time stamp is the 64-bit counter value SCount1 of the local FPGA. Go to A4. A4. The local FPGA determines whether it has received a message of type 2 sent by the other side. If so, proceed to A5. Otherwise, if the message is not received within 1 second, set the communication error flag and proceed to A1. A5. The local FPGA records the arrival time stamp SCount2 of the received message of type 2. It extracts the receiving and transmitting timestamps from this message. The receiving and transmitting timestamps are the 64-bit counter values ​​PCount1 and PCount2 of the local FPGA, respectively. Then, it calculates the fiber optic communication delay time Tdelay. Tdelay=[(SCount2-SCount1)-(PCount2-PCount1)] / 2, Calculate the deviation value δCnt between the two counters: δCnt=PCount1-SCount1-Tdelay, Finally, update the storage Tdelay and δCnt, set the communication normal flag and save it to the dual-port RAM on this side, then switch to A1; The data frame contains the following data: There are four message types: 1-heartbeat transmission, 2-heartbeat return, 3-traveling wave ranging transmission, and 4-traveling wave velocity measurement transmission. This side sends a time stamp; this data is valid for message types 1, 3, and 4. The receiving time stamp is valid for message type 2. The other side sends a timestamp; this data is valid for message type 2. The local wavefront frequency is 1. This data is valid for message type 3. For other message types, fill in 0. The local wavefront time stamp is 1. This data is valid for message type 3. For other message types, fill in 0. ... The local wavefront frequency is 10. This data is valid for message type 3. For other message types, fill in 0. The wavefront time stamp is 10. This data is valid for message type 3. For other message types, fill in 0. This side's speed measurement traveling wave frequency, this data is valid for message type 4; This side's velocity traveling wave time stamp, this data is valid for message type 4; Frame sequence number; this data is used to determine whether a message has been lost. CRC16, this data is the CRC checksum, used to determine whether this frame of data is correct.

5. The traveling wave ranging method based on online velocity measurement according to claim 4, characterized in that, The traveling wave velocity at different frequencies was measured in real time using an online measurement method, and a traveling wave frequency-velocity relationship table was generated.

6. The traveling wave ranging method based on online velocity measurement according to claim 5, characterized in that, The specific steps for generating the traveling wave frequency-velocity relationship table are as follows: B1. Initialize the traveling wave frequency of the FPGA on this side to ft=10kHz, then proceed to B2; B2. The FPGA on this side transmits a pulse wave with a frequency of ft and a duration of 300µs, and stores the FPGA clock counter value of the first rising edge as the local velocity measurement traveling wave time stamp SCountt. Proceed to B3. B3. The FPGA on this side fills the local speed measurement traveling wave frequency Sft=ft and the local speed measurement traveling wave time stamp SCountt into a type 4 message and sends it to the traveling wave ranging module on the other side, then proceeds to B4. B4. The FPGA on the opposite side reads the sampled data PValue from the opposite side, increments the sampling time stamp PCount from the opposite side, and writes the sampled data group [PCount, PValue] from the opposite side into the dual-port RAM in a loop. The FPGA on the opposite side determines whether to start waveform recording based on whether the ripple mutation is greater than the ripple threshold. If waveform recording is started, it generates ripple waveform data for 400µs, including 100µs before waveform recording starts and 300µs after waveform recording starts. The CPU on the opposite side uses the Karenbauer transform to obtain the traveling wave line mode components from the latest 400µs three-phase current / voltage traveling wave recording data stored in the dual-port RAM on the opposite side. Then, it performs Hilbert-Huang Transform (HHT) and differentiation operations on the line mode components to obtain the relationship between the amplitude and time of the traveling wave line mode components at different frequencies. Here, PCount is the sampling time corresponding to PValue of the sampling data on the opposite side, and PValue is the amplitude of the traveling wave current / voltage collected on the opposite side; Go to B5; B5. The CPU on the opposite side determines whether it has received a Type 4 message from this side. If so, it proceeds to B6; otherwise, it goes to B5. B6. The CPU on the opposite side parses the Type 4 message on this side, extracts the local speed measurement traveling wave frequency Sft and the local speed measurement traveling wave time stamp SCountt. Through the relationship between the traveling wave frequency and time in step B4, the time stamp SCounttcal corresponding to the local speed measurement traveling wave frequency Sft is obtained. First, the clock counter difference ΔCnt1 between the two wave head time stamps is calculated: △Cnt1=SCounttcal-(SCountt-δCnt), where δCnt is the deviation value of the two counters calculated in claim 4; Then calculate the absolute time difference ΔT1 between the two wavefronts: △T1=△Cnt1 / Ffpga, where Ffpga is the operating frequency of the FPGA, taken as 100MHz; Finally, calculate the traveling wave velocity vt: vt = L / △T1, where L is the line length; Go to B7; B7. The CPU of the opposite side ranging measure stores the traveling wave frequency Sft and traveling wave velocity vt of the local side velocity measurement into the traveling wave frequency-velocity relationship table; go to B8. B8. Set the traveling wave frequency ft of the FPGA on this side to 100kHz, 200kHz, 300kHz, 400kHz, 500kHz, 600kHz, 700kHz, 800kHz, and 900kHz in sequence, and execute steps B2-B7 for each traveling wave frequency.

7. The traveling wave ranging method based on online velocity measurement according to claim 4, characterized in that, The ranging CPU and FPGA of the two traveling wave ranging modules work together to calculate the traveling wave ranging time.

8. The traveling wave ranging method based on online velocity measurement according to claim 7, characterized in that, The specific steps for calculating the traveling wave ranging time are as follows: C1: The FPGA on this side reads the local sampled data SValue, increments the local sampled time stamp SCount, and writes the local sampled data group [SCount, SValue] cyclically into the local dual-port RAM1 area. Then, proceed to C2. C2. When the FPGA on this side determines that the ripple mutation is greater than the ripple threshold, it starts ripple recording and goes to C3; otherwise, it goes to C1. C3. The FPGA on this side stores the complete traveling wave waveform data of 400µs, including 100µs before the start of waveform recording and 300µs after the start, into the dual-port RAM1 area. It then stops writing to the dual-port RAM1 area on this side and switches to writing the traveling wave data to the dual-port RAM2 area on this side in a loop. Go to C4. C4. The local ranging CPU uses Karenbauer transformation on the latest 400µs three-phase current traveling wave recording data in the local dual-port RAM1 area to obtain the traveling wave line mode component. Then, it performs Hilbert-Huang Transform (HHT) and differentiation operations on the traveling wave line mode component to obtain the relationship between the amplitude and time of the traveling wave component at different frequencies. Within the range of 10 frequency bands [10kHz, 100kHz), [100kHz, 200kHz), ..., [900kHz, 1000kHz), it finds the frequency point with the largest amplitude that is greater than the traveling wave threshold value and records the local frequency data group [Sfi, SCountSti], where i=1-10, Sfi is the local frequency value, and SCountSti is the local wavefront time stamp. The wavefront time stamp of the frequency point with the amplitude less than the traveling wave threshold value is cleared to 0, and then the process is switched to C5. C5. The local ranging CPU fills the data of the local frequency data group into a type 3 message and sends it to the traveling wave ranging module on the opposite side via the FPGA, then proceeds to C6. C6. The local ranging CPU determines whether it has received a Type 3 message from the other side. If so, it proceeds to C7. Otherwise, if the message is not received within 1 second, the ranging time invalidation flag is set. C7. The local ranging CPU parses the type 3 message from the opposite side, obtaining the opposite side frequency data group [Pfi, PCountSti]. It compares it with the local side frequency data group [Sfi, SCountSti] to obtain the local side wavefront time stamp SCountSt, the opposite side wavefront time stamp PCountSt, and the wavefront frequency f, which have the same frequency value, the smallest frequency value, and are not equal to 0. First, calculate the counter difference △Cnt2 between the two wavefront time stamps: △Cnt2=SCountSt-(PCountSt-δCnt), where δCnt is the deviation value of the two counters calculated in claim 4; Then calculate the absolute time difference ΔT2 between the two wavefronts: △T2=△Cnt2 / Ffpga; where Ffpga is the operating frequency of the FPGA, taken as 100MHz; Finally, switch to C8; C8. The local ranging CPU finds the closest traveling wave velocity v from the traveling wave frequency-velocity relationship table based on the wavefront frequency f, and calculates the distance x from the fault point to the local traveling wave ranging module: x=[L+△T2*v] / 2.

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