Alternating current line protection method and system based on rapid extraction of wavefront exponential term coefficient

Abstract

The invention discloses an alternating-current line protection method and system based on wavefront exponential term coefficient rapid extraction, and the method comprises the steps: collecting three-phase voltage and three-phase current of a target line, and carrying out the phase-mode transformation respectively, and obtaining modulus voltage and modulus current; calculating a modulus fault voltage reverse traveling wave based on the modulus voltage and the modulus current; starting line protection based on modulus fault voltage reverse traveling wave; constructing a first data window with a preset length, and adjusting the length of the first data window to obtain a second data window; constructing a fault direction criterion, and determining a fault direction according to the fault direction criterion; when it is determined that the fault direction is a forward fault, a multi-point elimination method is adopted to calculate the wavefront of a first fault voltage traveling wave, and a wavefront index coefficient is obtained; and fault judgment is carried out based on the wavefront index coefficient, and corresponding line protection actions are adopted. According to the invention, a multi-point elimination method is adopted, so that the quick-action requirement of traveling wave protection can be better met, and meanwhile, higher transition resistance resistance is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of AC power transmission line protection, and in particular to an AC line protection method and system based on rapid extraction of wavefront exponential term coefficients. Background Art

[0002] With the transformation of energy structure and the large-scale grid connection of renewable energy, the proportion of fluctuating energy in power supply continues to increase, which poses great challenges to the operation mode and protection strategy of traditional power systems. These new energy sources are often connected to the power grid through a large number of power electronic converters. These devices are not only highly controllable, but also introduce new electrical characteristics, such as weak feedback and increased sensitivity to fault disturbances. Therefore, the grid fault characteristics of new power systems have become more complex and changeable. On the one hand, due to the large-scale application of power electronic equipment, the characteristics of fault currents may be significantly different from those in traditional power grids; on the other hand, the rapid response capability of power electronic equipment may also lead to faster fault propagation, increasing the difficulty of protection. Therefore, the power grid protection system needs to have a higher level of intelligence, be able to quickly and accurately extract fault feature information, and remove the fault in the shortest possible time to ensure the stable operation of the system and the rapid recovery of the fault.

[0003] At present, as an advanced protection technology, traveling wave front protection of AC transmission lines can achieve rapid protection by detecting the traveling wave signal generated by the fault. Traveling wave protection utilizes the propagation characteristics of the voltage or current traveling wave generated when a fault occurs on the transmission line, and can detect abnormalities at the early stage of the fault, thereby providing extremely fast protection action time. However, the existing traveling wave protection principles, especially those constructed based on fitting methods, still have the problem of insufficient speed in practical applications. Although traveling wave protection can theoretically achieve millisecond-level protection action time, it is often difficult to achieve ideal speed in practical applications due to the limitations of signal acquisition, processing and algorithm complexity. Summary of the invention

[0004] In order to overcome the problem of insufficient speed in the existing traveling wave protection technology, the present invention provides an AC line protection method and system based on rapid extraction of wavefront exponential term coefficients.

[0005] In a first aspect, an embodiment of the present invention provides an AC line protection method based on rapid extraction of wavefront exponential term coefficients, comprising:

[0006] Collecting the three-phase voltage and three-phase current of the target line, and performing phase-to-mode transformation on the three-phase voltage and the three-phase current respectively to obtain the modulus voltage and the modulus current;

[0007] Calculating a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current respectively, and calculating a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component;

[0008] Initiate line protection based on the reverse traveling wave of the modulus fault voltage;

[0009] Constructing a first data window of a preset length based on the modulus fault voltage inverse traveling wave, and adjusting the length of the first data window according to the extracted arrival time of the second traveling wave head to obtain a second data window;

[0010] constructing a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determining the fault direction according to the fault direction criterion;

[0011] When the fault direction is determined to be a forward fault, the multi-point elimination method is used to calculate the wavefront of the first fault voltage traveling wave to obtain the wavefront index coefficient;

[0012] A fault judgment is performed based on the wavefront index coefficient, and a corresponding line protection action is taken according to the fault judgment result.

[0013] Preferably, the collecting of the three-phase voltage and the three-phase current of the target line, and performing phase-to-mode transformation on the three-phase voltage and the three-phase current respectively to obtain the modulus voltage and the modulus current, comprises:

[0014] The three-phase voltage and three-phase current of the target line are collected by using a traveling wave voltage sensor;

[0015] Performing phase-mode transformation on the three-phase voltage using a phase-mode transformation matrix to obtain a modulus voltage;

[0016] The phase-to-mode transformation matrix is ​​used to perform phase-to-mode transformation on the three-phase current to obtain the modulus current.

[0017] Preferably, the calculating of the modulus voltage fault component and the modulus current fault component based on the modulus voltage and the modulus current respectively, and calculating the modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component, comprises:

[0018] Subtracting the modulus voltage from the modulus voltage of the target line during normal operation to obtain a modulus voltage fault component;

[0019] Subtracting the modulus current from the modulus current of the target line during normal operation to obtain a modulus current fault component;

[0020] According to the modulus voltage fault component and the modulus current fault component, a modulus fault voltage reverse traveling wave is calculated using a preset formula, wherein the preset formula is as follows:

[0021] Δu b =0.5(Δu-Z c Δi)

[0022] Among them, Δu b represents the modulus fault voltage reverse wave, Δu represents the modulus voltage fault component, Δi represents the modulus current fault component, and Z c Indicates the modal wave impedance of the target line.

[0023] Preferably, the inverse traveling wave starting line protection based on the modulus fault voltage includes:

[0024] It is determined whether the reverse wave of the modulus fault voltage satisfies the protection start condition. If so, the line protection is started. The protection start condition is characterized by the following formula:

[0025]

[0026] Among them, Δu b (k) represents the absolute value of the kth sampling point of the modulus fault voltage reverse wave, Δu b (k+1) represents the absolute value of the k+1th sampling point of the modulus fault voltage reverse wave, Δu b (k+2) represents the absolute value of the k+2th sampling point of the modulus fault voltage reverse wave, Δu set Indicates the protection device action threshold.

[0027] Preferably, adjusting the length of the first data window according to the extracted second traveling wave header arrival time to obtain the second data window includes:

[0028] The wavelet transform modulus maximum method is used to extract the arrival time of the second traveling wave head;

[0029] Determine whether the arrival time of the second traveling wave head is within the first data window. If so, adjust the length of the first data window to the arrival time of the head of the modulus fault voltage reverse traveling wave to the arrival time of the second traveling wave head to obtain the second data window. Otherwise, characterize the first data window as the second data window.

[0030] Preferably, constructing a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determining the fault direction according to the fault direction criterion includes:

[0031] The following formula is used to characterize the fault direction criterion:

[0032]

[0033] Among them, F T1represents the fault direction criterion under the 1-mode fault component, F T2 represents the fault direction criterion under the 2-mode fault component, Δu1(k+j) represents the k+jth sampling point of the 1-mode voltage fault component, Δi1(k+j) represents the k+jth sampling point of the 1-mode current fault component, Δu2(k+j) represents the k+jth sampling point of the 2-mode voltage fault component, Δi2(k+j) represents the k+jth sampling point of the 2-mode current fault component, and N w Indicates the number of sampling points in the second data window.

[0034] Preferably, when the fault direction is determined to be a forward fault, the multi-point elimination method is used to calculate the first fault voltage traveling wave front to obtain the wave front index coefficient, including:

[0035] The wavefront index coefficient is calculated using the following formula:

[0036]

[0037] Where p represents the wavefront index coefficient, n represents the sampling interval, Δt represents the sampling interval, M represents the total number of sampling points, Num[j] represents the numerator corresponding to the jth sampling point, and Den[j] represents the denominator corresponding to the jth sampling point.

[0038] Preferably, the performing fault judgment based on the wavefront index coefficient and taking corresponding line protection actions according to the fault judgment result includes:

[0039] Determine whether the wavefront index coefficient meets the in-zone fault condition, if so, determine that the fault type corresponding to the wavefront index coefficient is an in-zone fault, otherwise, determine that the fault type corresponding to the wavefront index coefficient is an out-of-zone fault;

[0040] Corresponding line protection actions are taken for the in-area fault and the out-area fault respectively. Preferably, the in-area fault condition is characterized by the following formula:

[0041] p≥p set =k rel ×p ser

[0042] Where p represents the wavefront index coefficient, p set represents the setting value of the wavefront index coefficient, k rel represents the reliability coefficient, p ser Indicates the wavefront index coefficient under line end fault.

[0043] In a second aspect, an embodiment of the present invention provides an AC line protection system based on rapid extraction of wavefront exponential term coefficients, including:

[0044] A phase-to-mode conversion module is used to collect the three-phase voltage and the three-phase current of the target line, and perform phase-to-mode conversion on the three-phase voltage and the three-phase current to obtain the modulus voltage and the modulus current;

[0045] A voltage reverse traveling wave calculation module, used to calculate a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current, respectively, and calculate a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component;

[0046] A starting protection module, used for starting line protection based on the reverse traveling wave of the modulus fault voltage;

[0047] A data window determination module, configured to construct a first data window of a preset length based on the modulus fault voltage anti-traveling wave, and adjust the length of the first data window according to the extracted arrival time of the second traveling wave head to obtain a second data window;

[0048] A fault direction determination module, configured to construct a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determine the fault direction according to the fault direction criterion;

[0049] A wavefront index coefficient calculation module is used to calculate the first fault voltage traveling wave front by using a multi-point elimination method to obtain a wavefront index coefficient when the fault direction is determined to be a forward fault;

[0050] The line protection module is used to perform fault judgment based on the wavefront index coefficient and take corresponding line protection actions according to the fault judgment result.

[0051] Compared with the prior art, the AC line protection method and system based on rapid extraction of wavefront index term coefficients in the embodiment of the present invention has the beneficial effect that: in the process of extracting the wavefront index coefficients, the multi-point elimination process is not performed, but only the relationship between the wavefront index coefficients and the sampling points is obtained by the multi-point elimination method, so as to directly determine the wavefront index coefficients, which greatly reduces the calculation complexity, realizes the rapid extraction of the wavefront index coefficients, can better meet the speed requirements of traveling wave protection, and has a higher transition resistance resistance capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a flow chart of an AC line protection method based on rapid extraction of wavefront index term coefficients according to an embodiment of the present invention;

[0053] Figure 2 It is a schematic diagram of the process of phase mode transformation according to an embodiment of the present invention;

[0054] Figure 3 It is a schematic diagram of a flow chart of calculating a reverse traveling wave of a modulus fault voltage according to an embodiment of the present invention;

[0055] Figure 4 is a schematic diagram of a process of obtaining a second data window according to an embodiment of the present invention;

[0056] Figure 5 It is a schematic diagram of the flow of fault judgment and protection action in an embodiment of the present invention;

[0057] Figure 6 is a schematic diagram of the topological structure of the AC system according to an embodiment of the present invention;

[0058] Figure 7 It is a schematic diagram of the time domain waveform and wavelet transform result when a phase A grounding fault occurs at a distance of 50 km in the forward direction from the measuring point according to the embodiment of the present invention;

[0059] Figure 8 is a schematic diagram of the results of extracting the exponential coefficient under fault conditions of different fault distances and different transition resistances according to an embodiment of the present invention;

[0060] Fig. 9 It is a structural schematic diagram of an AC line protection system based on rapid extraction of wavefront exponential term coefficients according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0062] In the description of the present invention, it should be understood that the terms "first" and "second" etc. are used in the present invention to distinguish different objects rather than to describe a specific order.

[0063] like Figure 1 As shown, an embodiment of the present invention provides an AC line protection method based on rapid extraction of wavefront index term coefficients, comprising the steps of:

[0064] S1, collecting the three-phase voltage and three-phase current of the target line, and performing phase-to-mode transformation on the three-phase voltage and the three-phase current respectively to obtain the modulus voltage and the modulus current;

[0065] Specifically, Figure 2 As shown, step S1 includes:

[0066] S101, collecting three-phase voltage and three-phase current of the target line using a traveling wave voltage sensor;

[0067] The traveling wave voltage sensor is used to collect the a, b, c phase voltages and a, b, c phase currents of the target line.

[0068] S102, using a phase-mode transformation matrix to perform phase-mode transformation on the three-phase voltage to obtain a modulus voltage;

[0069] The phase transformation matrix is ​​used to perform phase transformation on the a, b, and c phase voltages to obtain 0, 1, and 2 mode voltages.

[0070] S103, using a phase-to-mode transformation matrix to perform phase-to-mode transformation on the three-phase current to obtain a modulus current.

[0071] The phase transformation matrix is ​​used to perform phase transformation on the a, b, and c phase currents to obtain 0, 1, and 2 mode currents.

[0072] Specifically, the following formula is used to characterize the phase mode transformation:

[0073]

[0074] in, represents the modulus voltage or modulus current, represents the phase transformation matrix, Indicates three-phase voltage or three-phase current.

[0075] S2, respectively calculating a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current, and calculating a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component;

[0076] Specifically, Figure 3 As shown, step S2 includes:

[0077] S201, subtracting the modulus voltage from the modulus voltage of the target line during normal operation to obtain a modulus voltage fault component;

[0078] S202, subtracting the modulus current from the modulus current of the target line during normal operation to obtain a modulus current fault component;

[0079] S203. Calculate the modulus fault voltage reverse wave using a preset formula according to the modulus voltage fault component and the modulus current fault component.

[0080] Taking the bus pointing circuit as the positive direction, according to the modulus voltage fault component and the modulus current fault component, a preset formula is used to calculate the modulus fault voltage reverse traveling wave, that is, a unidirectional traveling wave without superimposed reflected wave.

[0081] Specifically, the preset formula is as follows:

[0082] Δu b =0.5(Δu-Z c Δi)

[0083] Among them, Δu b represents the modulus fault voltage reverse wave, Δu represents the modulus voltage fault component, Δi represents the modulus current fault component, and Z cIndicates the modal wave impedance of the target line.

[0084] S3, start line protection based on modulus fault voltage reverse traveling wave;

[0085] Determine whether the modulus fault voltage reverse wave meets the protection start condition, and if so, start the line protection.

[0086] Specifically, the following formula is used to characterize the protection start condition:

[0087]

[0088] Among them, Δu b (k) represents the absolute value of the kth sampling point of the modulus fault voltage reverse wave, Δu b (k+1) represents the absolute value of the k+1th sampling point of the modulus fault voltage reverse wave, Δu b (k+2) represents the absolute value of the k+2th sampling point of the modulus fault voltage reverse wave, Δu set Indicates the action threshold of the protection device. Δu set The setting can be done by avoiding voltage fluctuations during normal operation.

[0089] Further, if it is determined that the modulus fault voltage reverse wave does not meet the protection start condition, the process returns to step S1 until the calculated modulus fault voltage reverse wave meets the protection start condition.

[0090] S4, constructing a first data window of preset length based on the modulus fault voltage inverse traveling wave, and adjusting the length of the first data window according to the arrival time of the extracted second traveling wave head to obtain a second data window;

[0091] The first data window only contains the modulus fault voltage reverse wave. Specifically, Figure 4 As shown, step S4 includes:

[0092] S401, extracting the arrival time of the second traveling wave head by using the wavelet transform modulus maximum method;

[0093] The wavelet transform modulus maximum method is used to calibrate the moment when the second traveling wave head reaches the protection measuring point.

[0094] S402, determine whether the second traveling wave head arrival time is within the first data window, if so, adjust the length of the first data window to the time from the wave head arrival time of the modulus fault voltage reverse traveling wave to the time from the wave head arrival time of the second traveling wave to obtain the second data window, otherwise, characterize the first data window as the second data window.

[0095] Determine whether the arrival time of the second traveling wave head is within the first data window. If so, extract the first data window from the arrival time of the head of the modulus fault voltage reverse traveling wave, i.e., the start time to the arrival time of the second traveling wave head, to obtain the second data window. Otherwise, directly characterize the first data window as the second data window.

[0096] S5, constructing a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determining the fault direction according to the fault direction criterion;

[0097] Specifically, the following formula is used to characterize the fault direction criterion:

[0098]

[0099] Among them, F T1 represents the fault direction criterion under the 1-mode fault component, F T2 represents the fault direction criterion under the 2-mode fault component, Δu1(k+j) represents the k+jth sampling point of the 1-mode voltage fault component, Δi1(k+j) represents the k+jth sampling point of the 1-mode current fault component, Δu2(k+j) represents the k+jth sampling point of the 2-mode voltage fault component, Δi2(k+j) represents the k+jth sampling point of the 2-mode current fault component, and N w It indicates the number of sampling points in the second data window. It can be understood that the fault direction includes forward fault and reverse fault.

[0100] S6. When the fault direction is determined to be a forward fault, the multi-point elimination method is used to calculate the wavefront of the first fault voltage traveling wave to obtain the wavefront index coefficient;

[0101] Specifically, the wavefront index coefficient is calculated using the following formula:

[0102]

[0103] Where p represents the wavefront index coefficient, n represents the sampling interval, Δt represents the sampling interval, M represents the total number of points, Num[j] represents the numerator corresponding to the jth sampling point, and Den[j] represents the denominator corresponding to the jth sampling point. It can be understood that n represents the sampling interval, that is, one point is selected every n sampling points to participate in the calculation of the index term coefficient; M represents the total number of points, that is, the total number of points involved in the calculation of the index term coefficient.

[0104] Furthermore, the following formulas are used to calculate Num[j] and Den[j] respectively:

[0105] Num[j]=2cos(nω0Δt)Δu p1 (t0+(j+1)nΔt)-Δu p1 (t0+jnΔt)-Δup1 (t0+(j+2)nΔt)

[0106] Den[j]=2cos(nω0Δt)Δu p1 (t0+(j+2)nΔt)-Δu p1 (t0+(j+1)nΔt)-Δu p1 (t0+(j+3)nΔt)

[0107] Among them, ω0 represents the power frequency angular frequency, t0 represents the sampling start time, Δu p1 (·) represents the first fault voltage traveling wave front sampling point.

[0108] It should be noted that this step does not perform the multi-point elimination process during the wavefront index coefficient extraction process, but only uses the multi-point elimination method to obtain the relationship between the wavefront index coefficient and the sampling points, thereby directly determining the wavefront index coefficient, which greatly reduces the calculation complexity and is conducive to the rapid extraction of the wavefront index coefficient.

[0109] S7. Perform fault judgment based on the wavefront index coefficient, and take corresponding line protection actions according to the fault judgment result.

[0110] Specifically, Figure 5 As shown, step S7 includes:

[0111] S701, determining whether the wavefront index coefficient meets the in-zone fault condition, if so, determining the fault type corresponding to the wavefront index coefficient is an in-zone fault, otherwise determining the fault type corresponding to the wavefront index coefficient is an out-of-zone fault;

[0112] Specifically, the following formula is used to characterize the fault conditions in the area:

[0113] p≥p set =k rel ×p ser

[0114] Where p represents the wavefront index coefficient, p set represents the setting value of the wavefront index coefficient, k rel represents the reliability coefficient, p ser Indicates the wavefront index coefficient under line end fault.

[0115] S702. Take corresponding line protection actions for the faults within the area and the faults outside the area respectively.

[0116] When faults occur in the zone, the traveling wave protection device will quickly detect these faults and take corresponding protection actions to isolate the fault area and protect the equipment and personnel safety of the power system.

[0117] Specific protection actions include:

[0118] 1) Tripping action: When a fault is detected in the zone, the traveling wave protection device will quickly issue a tripping command to trip the circuit breaker at the fault point, thereby cutting off the fault current and preventing the fault range from expanding;

[0119] 2) Fault isolation: Through tripping action, the fault area is isolated from the rest of the power system to ensure that the fault does not affect the entire system;

[0120] 3) Alarm and record: The traveling wave protection device sends out an alarm signal and records the fault information so that the operation and maintenance personnel can handle and analyze it in time.

[0121] When a fault occurs outside the zone, the traveling wave protection device cannot take direct action to isolate the fault, and other measures are needed to assist in isolating the fault and protecting the equipment and personnel safety of the power system.

[0122] Specific protection actions include:

[0123] 1) The traveling wave protection device triggers the corresponding alarm or early warning mechanism according to the impact of the fault on the power system;

[0124] 2) The power system takes actions such as automatic switching on of backup power sources and load transfer.

[0125] In order to verify the effectiveness of the AC line protection method based on rapid extraction of wavefront index coefficients, in a specific embodiment, the following is constructed in PSCAD software: Figure 6 The AC system topology shown in the figure, G1~G3 represent AC power supply, rated voltage is 230kV, A~D represent busbar, L b It represents inductance, the measuring point represents the protection installation location, the positive direction is when the bus passes through the measuring point and points to the line, and the sampling interval is 5 microseconds.

[0126] Forward faults are set at 50km, 100km, 150km, 200km, 250km, 300km, 350km, 400km, and 450km from the measuring point, and reverse faults are set at 50km, 100km, and 300km on bus A and line AD. The simulation results when the transition resistance is 0Ω and 500Ω are shown in Tables 1 and 2, respectively.

[0127] Table 1 Simulation results under 0Ω transition resistance

[0128]

[0129]

[0130] Table 2 Simulation results under 500Ω transition resistance

[0131]

[0132] It can be seen from Table 1 and Table 2 that under the fault conditions of different fault distances and different transition resistances, the protection can be started normally and the fault direction can be accurately determined. When a single-phase metallic grounding fault occurs on bus B at the end of line AB, the extraction result of the traveling wave front index coefficient is p = 0.872*10 5 , take the reliability coefficient k rel =1.2, then the protection setting value p set =1.046*10 5 The present invention can protect about 85% of the total length of the line at this setting value. For line AB, when a forward fault occurs within 212.5 km, the extraction results of the traveling wave front index coefficient based on multi-point elimination are all greater than the setting value (1.046*10 5 ), the protection is activated, and under high resistance fault, the protection can still operate reliably, indicating that the present invention has a strong ability to withstand transition resistance.

[0133] When a phase A grounding fault occurs 50 km in the forward direction from the measuring point, the protection start-up conditions are met and the protection starts. Figure 7 The time domain waveform and wavelet transform result of the fault are shown. In order to achieve a better visual effect, both waveforms are numerically scaled. Figure 7 It can be seen that the modulus maximum reflects the arrival time of the wave head, where the first modulus maximum in the traveling wave data is the arrival time of the traveling wave, and the second modulus maximum is the arrival time of the first interference traveling wave. The sampling data corresponding to the time period between the two maximum values ​​is taken as the data in the data window. If the data window length is greater than 150 sampling points at this time, the first 150 points are intercepted as the data window. When a phase A grounding fault occurs 50 km away from the measuring point in the forward direction, the fault direction criterion is calculated to be -103.529, which is determined to be a forward fault. The multi-point elimination method is used to calculate the wavefront index coefficient, and the calculation result is 3.294*10 5 , greater than the protection setting value (1.046*10 5 ), to protect reliable action.

[0134] Figure 8 The results of exponential coefficient extraction under fault conditions with different fault distances and different transition resistances are shown. As the fault distance increases, the exponential coefficient gradually decreases. When a fault occurs at the same location far away from the measuring point, different transition resistances have almost no effect on the exponential coefficient extraction results, indicating that the present invention has a strong ability to withstand transition resistance.

[0135] An embodiment of the present invention is an AC line protection method based on rapid extraction of wavefront index term coefficients. In the process of extracting the wavefront index coefficients, the multi-point elimination process is not performed, but only the relationship between the wavefront index coefficients and the sampling points is obtained by the multi-point elimination method, so as to directly determine the wavefront index coefficients, which greatly reduces the calculation complexity and realizes rapid extraction of the wavefront index coefficients. It can better meet the speed requirements of traveling wave protection and has a higher transition resistance capability.

[0136] Based on the above-mentioned AC line protection method based on rapid extraction of wavefront index term coefficients, Fig. 9 As shown, an embodiment of the present invention provides an AC line protection system based on rapid extraction of wavefront exponential term coefficients, including:

[0137] The phase-mode conversion module 1 is used to collect the three-phase voltage and three-phase current of the target line, and perform phase-mode conversion on the three-phase voltage and the three-phase current of the traveling wave protection device to obtain the modulus voltage and the modulus current;

[0138] A voltage reverse traveling wave calculation module 2 is used to calculate the modulus voltage fault component and the modulus current fault component based on the modulus voltage of the traveling wave protection device and the modulus current of the traveling wave protection device, respectively, and calculate the modulus fault voltage reverse traveling wave according to the modulus voltage fault component of the traveling wave protection device and the modulus current fault component of the traveling wave protection device;

[0139] A starting protection module 3, used for starting line protection based on the reverse traveling wave of the fault voltage modulus of the traveling wave protection device;

[0140] A data window determination module 4 is used to construct a first data window of a preset length based on the reverse traveling wave of the modulus fault voltage of the traveling wave protection device, and adjust the length of the first data window of the traveling wave protection device according to the extracted arrival time of the second traveling wave head to obtain a second data window;

[0141] A fault direction determination module 5 is used to construct a fault direction criterion based on the traveling wave protection device modulus voltage fault component, the modulus current fault component and the second data window, and determine the fault direction according to the traveling wave protection device fault direction criterion;

[0142] The wavefront index coefficient calculation module 6 is used to calculate the wavefront of the first fault voltage traveling wave by using a multi-point elimination method to obtain a wavefront index coefficient when the fault direction is determined to be a forward fault;

[0143] The line protection module 7 is used to perform fault judgment based on the wavefront index coefficient of the traveling wave protection device, and take corresponding line protection actions according to the fault judgment result.

[0144] It should be noted that each unit in the above-mentioned AC line protection system based on rapid extraction of wavefront index term coefficients can be fully or partially implemented by software, hardware and a combination thereof. The above-mentioned units can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to the above modules. For the specific definition of an AC line protection system based on rapid extraction of wavefront index term coefficients, please refer to the above definition of an AC line protection method based on rapid extraction of wavefront index term coefficients. The two have the same functions and effects, which will not be repeated here.

[0145] In summary, the embodiment of the present invention is an AC line protection method and system based on the rapid extraction of wavefront index term coefficients. In the process of extracting the wavefront index coefficients, the multi-point elimination process is not performed, but only the relationship between the wavefront index coefficients and the sampling points is obtained by the multi-point elimination method, so as to directly determine the wavefront index coefficients, which greatly reduces the calculation complexity and realizes the rapid extraction of the wavefront index coefficients. It can better meet the speed requirements of traveling wave protection and has a higher transition resistance capability.

[0146] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. It should be noted that the technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0147] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. An AC line protection method based on rapid extraction of wavefront index coefficients, characterized in that: include: Collecting the three-phase voltage and three-phase current of the target line, and performing phase-to-mode transformation on the three-phase voltage and the three-phase current respectively to obtain the modulus voltage and the modulus current; Calculating a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current respectively, and calculating a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component; Initiate line protection based on the reverse traveling wave of the modulus fault voltage; Constructing a first data window of a preset length based on the modulus fault voltage inverse traveling wave, and adjusting the length of the first data window according to the extracted arrival time of the second traveling wave head to obtain a second data window; constructing a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determining the fault direction according to the fault direction criterion; When the fault direction is determined to be a forward fault, the multi-point elimination method is used to calculate the wavefront of the first fault voltage traveling wave to obtain the wavefront index coefficient; A fault judgment is performed based on the wavefront index coefficient, and a corresponding line protection action is taken according to the fault judgment result.

2. The AC line protection method according to claim 1, characterized in that: The collecting of the three-phase voltage and the three-phase current of the target line, and performing phase-to-mode transformation on the three-phase voltage and the three-phase current respectively to obtain the modulus voltage and the modulus current, includes: The three-phase voltage and three-phase current of the target line are collected by using a traveling wave voltage sensor; Performing phase-mode transformation on the three-phase voltage using a phase-mode transformation matrix to obtain a modulus voltage; The phase-to-mode transformation matrix is ​​used to perform phase-to-mode transformation on the three-phase current to obtain the modulus current.

3. The AC line protection method according to claim 1, characterized in that: The method of calculating a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current, and calculating a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component, comprises: Subtracting the modulus voltage from the modulus voltage of the target line during normal operation to obtain a modulus voltage fault component; Subtracting the modulus current from the modulus current of the target line during normal operation to obtain a modulus current fault component; According to the modulus voltage fault component and the modulus current fault component, a modulus fault voltage reverse traveling wave is calculated using a preset formula, wherein the preset formula is as follows: Δu b =0.5(Δu-Z c Δi) Among them, Δu b represents the modulus fault voltage reverse wave, Δu represents the modulus voltage fault component, Δi represents the modulus current fault component, and Z c Indicates the modal wave impedance of the target line.

4. The AC line protection method according to claim 1, characterized in that: The method of starting line protection based on the reverse traveling wave of the modulus fault voltage comprises: It is determined whether the reverse wave of the modulus fault voltage satisfies the protection start condition. If so, the line protection is started. The protection start condition is characterized by the following formula: Among them, Δu b (k) represents the absolute value of the kth sampling point of the modulus fault voltage reverse wave, Δu b (k+1) represents the absolute value of the k+1th sampling point of the modulus fault voltage reverse wave, Δu b (k+2) represents the absolute value of the k+2th sampling point of the modulus fault voltage reverse wave, Δu set Indicates the protection device action threshold.

5. The AC line protection method according to claim 1, characterized in that: The step of adjusting the length of the first data window according to the extracted second traveling wave header arrival time to obtain the second data window comprises: The wavelet transform modulus maximum method is used to extract the arrival time of the second traveling wave head; Determine whether the arrival time of the second traveling wave head is within the first data window. If so, adjust the length of the first data window to the arrival time of the head of the modulus fault voltage reverse traveling wave to the arrival time of the second traveling wave head to obtain the second data window. Otherwise, characterize the first data window as the second data window.

6. The AC line protection method according to claim 1, characterized in that: The method of constructing a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determining the fault direction according to the fault direction criterion includes: The following formula is used to characterize the fault direction criterion: Among them, F T1 represents the fault direction criterion under the 1-mode fault component, F T2 represents the fault direction criterion under the 2-mode fault component, Δu1(k+j) represents the k+jth sampling point of the 1-mode voltage fault component, Δi1(k+j) represents the k+jth sampling point of the 1-mode current fault component, Δu2(k+j) represents the k+jth sampling point of the 2-mode voltage fault component, Δi2(k+j) represents the k+jth sampling point of the 2-mode current fault component, and N w Indicates the number of sampling points in the second data window.

7. The AC line protection method according to claim 1, characterized in that: When the fault direction is determined to be a forward fault, the multi-point elimination method is used to calculate the first fault voltage traveling wave front to obtain the wave front index coefficient, including: The wavefront index coefficient is calculated using the following formula: Where p represents the wavefront index coefficient, n represents the sampling interval, Δt represents the sampling interval, M represents the total number of sampling points, Num[j] represents the numerator corresponding to the jth sampling point, and Den[j] represents the denominator corresponding to the jth sampling point.

8. The AC line protection method according to claim 1, characterized in that: The performing fault judgment based on the wavefront index coefficient and taking corresponding line protection actions according to the fault judgment result includes: Determine whether the wavefront index coefficient meets the in-zone fault condition, if so, determine that the fault type corresponding to the wavefront index coefficient is an in-zone fault, otherwise, determine that the fault type corresponding to the wavefront index coefficient is an out-of-zone fault; Corresponding line protection actions are taken for the internal fault and the external fault respectively.

9. The AC line protection method according to claim 8, characterized in that: The following formula is used to characterize the fault conditions in the area: p≥pset=krel×pser Where p represents the wavefront index coefficient, p set represents the setting value of the wavefront index coefficient, k rel represents the reliability coefficient, p ser Indicates the wavefront index coefficient under line end fault.

10. An AC line protection system based on rapid extraction of wavefront index coefficients, characterized in that: include: A phase-to-mode conversion module is used to collect the three-phase voltage and the three-phase current of the target line, and perform phase-to-mode conversion on the three-phase voltage and the three-phase current to obtain the modulus voltage and the modulus current; A voltage reverse traveling wave calculation module, used to calculate a modulus voltage fault component and a modulus current fault component based on the modulus voltage and the modulus current, respectively, and calculate a modulus fault voltage reverse traveling wave according to the modulus voltage fault component and the modulus current fault component; A starting protection module, used for starting line protection based on the reverse traveling wave of the modulus fault voltage; A data window determination module, configured to construct a first data window of a preset length based on the modulus fault voltage anti-traveling wave, and adjust the length of the first data window according to the extracted arrival time of the second traveling wave head to obtain a second data window; A fault direction determination module, configured to construct a fault direction criterion based on the modulus voltage fault component, the modulus current fault component and the second data window, and determine the fault direction according to the fault direction criterion; A wavefront index coefficient calculation module is used to calculate the first fault voltage traveling wave front by using a multi-point elimination method to obtain a wavefront index coefficient when the fault direction is determined to be a forward fault; The line protection module is used to perform fault judgment based on the wavefront index coefficient and take corresponding line protection actions according to the fault judgment result.

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