Protection method and device based on fault condition pre-identification, equipment and storage medium

Abstract

The invention discloses a protection method, device and equipment based on fault condition pre-identification, and a storage medium, which are applied to the technical field of high-voltage direct-current transmission system protection, and are used for obtaining a current signal and a voltage signal after a fault of a to-be-protected system is detected, and after a fault direction is determined, extracting a one-mode voltage traveling wave fault component according to the voltage signal; and then calculating a waveform maximum value in a preset time window after the one-mode voltage traveling wave fault component reaches a sampling point, if the waveform maximum value is greater than a preset threshold value, performing fault condition identification according to the waveform characteristics of the one-mode voltage traveling wave fault component in the preset time window, determining a corresponding fault condition, and further performing fault diagnosis according to the corresponding fault condition. According to the method, the corresponding protection principle is determined, and the corresponding protection action is executed by using the corresponding protection principle, so that the protection method can give consideration to all fault conditions after the system breaks down, and the protection performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage direct current transmission system protection, and in particular to a protection method, device, equipment and storage medium based on fault condition pre-identification. Background Art

[0002] In high-voltage direct current (HVDC) transmission systems, relay protection is a critical component in ensuring safe and stable system operation. However, traditional protection schemes, often based on a single protection principle (such as traveling wave protection, current differential protection, and directional protection), struggle to fully adapt to complex and diverse fault scenarios. While each protection principle offers unique advantages under specific fault conditions, inherent drawbacks (such as the susceptibility of traveling wave protection to noise interference and the reliance of current differential protection on communication synchronization) often hinder improvements in protection performance.

[0003] Under current circumstances, different fault types (such as intra-zone faults, extra-zone faults, high-resistance faults, etc.) have different sensitivities to protection principles. A single principle is difficult to take into account all situations. Therefore, a method is needed that can take into account all fault situations and improve the overall performance of protection. Summary of the Invention

[0004] In order to solve the above technical problems, the embodiments of the present invention provide a protection method, device, equipment and storage medium based on fault condition pre-identification to solve the technical problem in the prior art that a single protection principle cannot take into account all fault conditions, resulting in reduced overall protection performance.

[0005] A first aspect of an embodiment of the present invention provides a protection method based on fault condition pre-identification, the method comprising:

[0006] Obtain the current signal and voltage signal after the fault of the system to be protected, and obtain the fault direction of the power system based on the polarity comparison of the voltage signal and the current signal;

[0007] Based on the fault direction, the voltage signal is transformed into a phase mode to obtain a single-mode voltage, which is then extracted to obtain a single-mode voltage traveling wave fault component.

[0008] Calculate the maximum value of the single-mode voltage traveling wave fault component within a preset time window after it reaches the sampling point to obtain the waveform maximum value. If the waveform maximum value is greater than a preset threshold, obtain the waveform characteristics based on the single-mode voltage traveling wave fault component within the preset time window. Perform fault condition identification based on the waveform characteristics to obtain an identification result.

[0009] Based on the identification results, the corresponding protection principle is determined, and the corresponding protection action is performed according to the protection principle.

[0010] In a possible implementation of the first aspect, performing phase-mode transformation on the voltage signal based on the fault direction to obtain a single-mode voltage includes:

[0011] If the fault direction is a forward fault, the voltage signal is subjected to phase-mode transformation to obtain a single-mode voltage;

[0012] If the fault direction is a reverse fault, the protection action will be terminated.

[0013] In a possible implementation of the first aspect, calculating a maximum value of a voltage traveling wave fault component within a preset time window after the fault component reaches a sampling point to obtain a waveform maximum value includes:

[0014] According to a preset sampling time interval, multiple single-mode voltage traveling wave fault components within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point are obtained;

[0015] Based on the total number of multiple single-mode voltage traveling wave fault components and the preset sampling time interval, the maximum value of the waveform is calculated using the maximum value calculation formula, where the maximum value calculation formula is:

[0016] Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,……N

[0017]

[0018] Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

[0019] In a possible implementation of the first aspect, identifying a fault condition based on waveform characteristics to obtain an identification result includes:

[0020] If there are significant singular points in the waveform characteristics, the identification result is determined to be that the system to be protected is in the first type of fault condition;

[0021] If the waveform characteristics all show a trend of first rising and then falling, the identification result is determined to be that the system to be protected is in the second type of fault condition;

[0022] If the waveform characteristics all show a monotonically increasing trend, the identification result is determined to be that the system to be protected is in a third type of fault condition.

[0023] In a possible implementation of the first aspect, determining a corresponding protection principle based on the identification result includes:

[0024] If the identification result shows that the system to be protected is in the first type of fault condition, the corresponding protection principle is determined to be the first protection principle, wherein the first protection principle is a traveling wave protection principle based on the slope of the traveling wave head;

[0025] If the identification result shows that the system to be protected is in the second type of fault condition, the corresponding protection principle is determined to be the second protection principle, wherein the second protection principle is a setting-free protection principle based on model error comparison;

[0026] If the identification result shows that the system to be protected is in the third type of fault condition, the corresponding protection principle is determined to be the third protection principle, wherein the third protection principle is a protection principle based on the rapid extraction of the coefficient of the traveling wave front exponential term.

[0027] In order to solve the same technical problem, a second aspect of an embodiment of the present invention provides a protection device based on fault condition pre-identification, comprising an acquisition module, a component extraction module, an identification module and an execution module, wherein:

[0028] The acquisition module is used to obtain the current signal and voltage signal after the fault of the system to be protected, and obtain the fault direction of the power system based on the polarity comparison of the voltage signal and the current signal;

[0029] The component extraction module is used to perform phase-mode transformation on the voltage signal based on the fault direction to obtain a single-mode voltage, and extract the single-mode voltage to obtain a single-mode voltage traveling wave fault component;

[0030] The identification module is used to calculate the maximum value of the single-mode voltage traveling wave fault component within a preset time window after it reaches the sampling point, and obtain the waveform maximum value. If the waveform maximum value is greater than a preset threshold, the waveform characteristics are obtained based on the single-mode voltage traveling wave fault component within the preset time window. The fault condition is identified based on the waveform characteristics to obtain an identification result;

[0031] The execution module is used to determine the corresponding protection principle based on the identification result and perform the corresponding protection action according to the protection principle.

[0032] In a possible implementation manner of the second aspect, the component extraction module includes a first judgment unit and a second judgment unit, wherein:

[0033] The first judgment unit is configured to perform phase-mode transformation on the voltage signal to obtain a first-mode voltage if the fault direction is a forward fault;

[0034] The second judgment unit is used to end the protection action if the fault direction is a reverse fault.

[0035] In a possible implementation of the second aspect, the identification module includes a sampling unit and a waveform maximum calculation unit, wherein:

[0036] A sampling unit, configured to obtain, according to a preset sampling time interval, a plurality of single-mode voltage traveling wave fault components within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point;

[0037] The waveform maximum value calculation unit is used to calculate the waveform maximum value based on the total number of multiple single-mode voltage traveling wave fault components and the preset sampling time interval using the maximum value calculation formula, wherein the maximum value calculation formula is:

[0038] Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,……N

[0039]

[0040] Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

[0041] A third aspect of an embodiment of the present invention provides a computer device, including:

[0042] Memory for storing computer programs;

[0043] The processor is configured to implement the steps of the protection method based on pre-identification of fault conditions in the first aspect when executing a computer program.

[0044] A fourth aspect of an embodiment of the present invention provides a storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the protection method based on pre-identification of fault conditions as described in the first aspect are implemented.

[0045] The technical solution of the present invention has the following advantages:

[0046] The protection method based on fault condition pre-identification provided by an embodiment of the present invention obtains the current signal and voltage signal after a fault of the system to be protected and determines the fault direction, extracts a single-mode voltage traveling wave fault component based on the voltage signal, and then calculates the waveform maximum value of the single-mode voltage traveling wave fault component within a preset time window after reaching a sampling point. If the waveform maximum value is greater than a preset threshold, the fault condition is identified based on the waveform characteristics of the single-mode voltage traveling wave fault component within the preset time window to determine the corresponding fault condition. Then, based on the corresponding fault condition, the corresponding protection principle is determined, and the corresponding protection action is executed using the corresponding protection principle. The above method can achieve that when a system fault occurs, the protection method can take all fault conditions into account, thereby improving protection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 Flowchart of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0049] Figure 2 Flowchart of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0050] Figure 3 A system topology diagram of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0051] Figure 4 Graphs showing waveform characteristics under different fault conditions of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0052] Figure 5 The classification of fault conditions and their waveform characteristics in the protection method based on fault condition pre-identification in an embodiment of the present invention;

[0053] Figure 6 4 is an overall flow chart of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0054] Figure 7 Graph showing the relationship between transition resistance and waveform maximum value of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0055] Figure 8 FIG. 1 is a PSCAD simulation result diagram of a protection method based on fault condition pre-identification in an embodiment of the present invention;

[0056] Figure 9 4 is a structural block diagram of a protection device based on fault condition pre-identification in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0058] The protection method based on fault condition pre-identification provided by the embodiment of the present invention is as follows: Figure 1 As shown, Figure 1 This is a flow chart of a protection method based on fault condition pre-identification, including steps S101 to S104, each of which is specifically as follows:

[0059] S101 : Acquire a current signal and a voltage signal after a fault occurs in a system to be protected, and obtain a fault direction of the power system based on a polarity comparison between the voltage signal and the current signal.

[0060] In this embodiment, the post-fault electrical signals of the protected system are monitored in real time to obtain the current and voltage signals after the fault occurs. The fault direction of the power system is determined by comparing the polarity of the voltage and current signals. Specifically, high-precision voltage transformers (PTs) and current transformers (CTs) are installed at key nodes of the protected system (such as the DC bus and converter outlets) to collect the post-fault voltage and current signals in real time. The sampling frequency must meet the requirements of traveling wave protection (typically ≥100kHz) to capture microsecond transient characteristics.

[0061] It should be noted that the system to be protected can be understood as a modular multilevel converter (MMC) system. The specific implementation of comparing the polarity of the voltage and current signals is prior art and not the core of the present invention. It will not be further elaborated here. Other techniques in the art can also be used to determine the fault direction.

[0062] In one embodiment, based on the fault direction, a phase-mode transformation is performed on the voltage signal to obtain a single-mode voltage, including:

[0063] If the fault direction is a forward fault, the voltage signal is subjected to phase-mode transformation to obtain a single-mode voltage;

[0064] If the fault direction is a reverse fault, the protection action will be terminated.

[0065] In this embodiment, if the fault direction is determined to be a forward fault, the voltage signal is subjected to phase-mode transformation to obtain a first-mode voltage. If the fault direction is determined to be a reverse fault, the protection action is terminated. Figure 2 As shown, Figure 2 For the protection method flow chart, since there are mature technical means for distinguishing the fault conditions of reverse faults, the focus of the present invention is to distinguish forward faults, that is, faults inside and outside the forward zone.

[0066] As an example of this embodiment, take a four-terminal MMC system as an example, its topology is as follows: Figure 3 As shown. Among them, f1, f3, and f5 represent line faults at the MMC exit, f5 represents a busbar fault, and f2 and f6 represent faults at any location on the line other than the MMC exit. f1 to f6 are all forward faults, and only f1 to f3 are intra-zone faults. Since there are mature technical means for distinguishing reverse faults, the focus of this invention is on distinguishing between forward and intra-zone faults. Based on this topology, a simulation model was built in PSCAD, and its fault settings are shown in Table 1. f1, f3, and f5 are line end faults, and their fault locations are fixed; f2 and f6 are line non-end faults, which can represent an infinite number of fault locations. For example, f6 in Table 1 represents 8 fault locations, that is, faults at 10, 30, ..., and 300 km away from f5. For f6, each fault location corresponds to 3 types of transition resistance, so f6 includes 8×3=24 different fault conditions. Table 1 contains a total of 105 different fault conditions, which cover common fault conditions. It should be noted that, since the traveling wave waveform characteristics are similar under positive pole grounding fault, negative pole grounding fault and inter-pole fault, and the design concept of the protection principle is the same, this embodiment only discusses the positive pole grounding fault.

[0067] Table 1 Fault settings in simulation

[0068]

[0069] S102 . Based on the fault direction, perform phase-mode transformation on the voltage signal to obtain a single-mode voltage, extract the single-mode voltage, and obtain a single-mode voltage traveling wave fault component.

[0070] In this embodiment, if the fault direction is a forward fault, the voltage signal is transformed and decoupled to obtain a single-mode component, namely, a single-mode voltage. The single-mode voltage is then extracted to obtain a single-mode voltage traveling wave fault component. Specifically, phase-mode transformations of different dimensions have different forms, and the corresponding transformation method can be selected based on the phase-mode dimension. For example, taking a two-phase phase-mode transformation as an example, the expression is:

[0071]

[0072] Where up 、u n Represents the voltage signals of the positive and negative electrodes respectively, i p 、i n Represent the voltage and current of the positive and negative poles respectively, u0 and u1 represent the 1-mode voltage and 0-mode voltage respectively, i0 and i1 represent the 1-mode current and 0-mode current respectively.

[0073] It should be noted that the 1-mode component is a line mode component that reflects the characteristics of phase-to-phase faults. Other methods of phase mode transformation include Clark transformation or Karenbauer transformation. Since these methods are commonly used in the field, the specific transformation steps will not be repeated here.

[0074] S103. Calculate the maximum value of a single-mode voltage traveling wave fault component within a preset time window after the fault component reaches the sampling point to obtain a waveform maximum value. If the waveform maximum value is greater than a preset threshold, obtain waveform characteristics based on the single-mode voltage traveling wave fault component within the preset time window. Perform fault condition identification based on the waveform characteristics to obtain an identification result.

[0075] In this embodiment, a preset time window is captured starting from the arrival of a single-mode voltage traveling wave fault component at a sampling point. The single-mode voltage traveling wave fault component within the preset time window is then calculated to obtain a waveform maximum. If the waveform maximum is greater than a preset threshold, the waveform characteristics of the single-mode voltage traveling wave fault component within the preset time window are analyzed. The fault condition is then identified based on the waveform characteristics to obtain an identification result. The identification result includes a rough description of the fault area and transition resistance. If the waveform maximum is less than the preset threshold, the protection can be directly locked, i.e.:

[0076] Δu 1.b.max <Δu thre1

[0077] Where Δu 1.b.max is the maximum value of the waveform, Δu threl is the preset threshold.

[0078] Δu threl =K rel Δu 1.b.max.f5_0Ω

[0079] Where K rel is the reliability coefficient, Δu 1.b.max.f5_0Ω Indicates the maximum value within the preset time window under f5 metallic fault.

[0080] It should be noted that the preset time window is a data window of fixed length, preferably 1ms. The reason for choosing 1ms as the data window is to ensure speed while taking into account the accuracy of fault information extraction, because the shorter the time window, the higher the protection speed. According to the characteristic analysis of the fault waveform, a 1ms waveform can make the waveform characteristics more fully presented, so 1ms is selected.

[0081] In one embodiment, calculating the maximum value of a voltage traveling wave fault component within a preset time window after the fault component reaches a sampling point to obtain the waveform maximum value includes:

[0082] According to a preset sampling time interval, multiple single-mode voltage traveling wave fault components within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point are obtained;

[0083] Based on the total number of multiple single-mode voltage traveling wave fault components and the preset sampling time interval, the maximum value of the waveform is calculated using the maximum value calculation formula, where the maximum value calculation formula is:

[0084] Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,......N

[0085]

[0086] Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave. b

[0087] In this embodiment, a voltage traveling wave fault component in a preset time window is acquired according to a preset sampling time interval, and the amount of data in the time window is Where, T w is the preset time window, Δt is the preset sampling time interval, that is, it includes N single-mode voltage traveling wave fault components, and then the maximum value calculation formula is used to calculate to obtain the waveform maximum value, where the maximum value calculation formula is:

[0088] Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,......N

[0089]

[0090] Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

[0091] In one embodiment, fault condition identification is performed based on waveform characteristics to obtain identification results, including:

[0092] If there are significant singular points in the waveform characteristics, the identification result is determined to be that the system to be protected is in the first type of fault condition;

[0093] If the waveform characteristics all show a trend of first rising and then falling, the identification result is determined to be that the system to be protected is in the second type of fault condition;

[0094] If the waveform characteristics all show a monotonically increasing trend, the identification result is determined to be that the system to be protected is in a third type of fault condition.

[0095] In this embodiment, fault conditions are identified based on the waveform characteristics of the single-mode voltage traveling wave fault component to obtain identification results. The waveform characteristics can be used to extract multiple key parameters for fault type identification and evaluation. Through the refined extraction and analysis of the waveform characteristics, multiple waveform characteristics are determined for fault condition determination. Specifically, in order to intuitively understand the reverse traveling wave waveform characteristics within 1ms under various fault conditions, the waveform characteristics under different fault conditions are displayed, as shown in Figure 1. Figure 4 As shown, the solid line is the PSCAD simulation result, and the dotted line is the time domain numerical solution after the frequency domain expression is substituted into the simulation parameters. Figure 4 , the waveform characteristics within 1ms under various fault conditions can be analyzed as follows: The waveform of the f1 fault is as follows Figure 4 As shown in (a), the waveform first rises rapidly and then rises slowly, showing a monotonic trend overall, and the amplitude is negatively correlated with the transition resistance. The waveform of the first line of the f2 fault is as follows Figure 4 As shown in (b), under different transition resistances, the waveforms first rise rapidly and then become flat, and the overall trend is monotonic. The maximum value of the waveform is negatively correlated with the transition resistance. The waveforms of f3, f4, and f5 are as follows Figure 4 (c)~ Figure 4 As shown in (e), the waveform characteristics of the faults f3, f4, and f5 are similar. They rise monotonically at low resistance and rise first and then fall at high resistance. The greater the transition resistance, the more significant the downward trend at the end of the waveform. The maximum value of the waveform is negatively correlated with the transition resistance. The waveform of the first line of the fault f6 is as follows: Figure 4 As shown in (f), under different transition resistances, the waveforms first rise and then fall. Figure 4 (g) Figure 4As shown in (h), due to the influence of catadioptric reflection at the fault point or boundary, the waveform has significant singular points. The waveform of fault f6 near the line boundary has significant singular points due to catadioptric reflection, but the waveform amplitude is extremely small.

[0096] Therefore, combined with the above analysis, we first Figure 3 The typical fault conditions in the system are divided into three categories, and the most appropriate protection principle is configured for each category. The fault conditions included in each category are as follows: Figure 5 As shown, it can be combined Figure 4 The common characteristics of the reverse traveling wave waveforms within 1ms corresponding to the fault conditions included in the same category are summarized. Specifically, the presence of significant singular points in the waveform characteristics corresponds to the first type of fault conditions; the waveform characteristics all show a trend of first rising and then falling, which corresponds to the second type of fault conditions; the waveform characteristics all show a monotonic upward trend, which corresponds to the third type of fault conditions.

[0097] It should be noted that the fault condition can be understood as a combination of fault information during a particular fault, such as the fault distance, transition resistance, fault type, etc. Because there is a certain correspondence between the fault waveform and the fault condition, the fault condition can be estimated from the waveform.

[0098] S104: Based on the identification result, determine the corresponding protection principle, and perform the corresponding protection action according to the protection principle.

[0099] In this embodiment, after the corresponding fault condition is identified, a suitable protection principle is selected according to the identification result, and the corresponding protection action is performed according to the protection principle.

[0100] In one embodiment, determining a corresponding protection principle based on the identification result includes:

[0101] If the identification result shows that the system to be protected is in the first type of fault condition, the corresponding protection principle is determined to be the first protection principle, wherein the first protection principle is a traveling wave protection principle based on the slope of the traveling wave head;

[0102] If the identification result shows that the system to be protected is in the second type of fault condition, the corresponding protection principle is determined to be the second protection principle, wherein the second protection principle is a setting-free protection principle based on model error comparison;

[0103] If the identification result shows that the system to be protected is in the third type of fault condition, the corresponding protection principle is determined to be the third protection principle, wherein the third protection principle is a protection principle based on the rapid extraction of the coefficient of the traveling wave front exponential term.

[0104] In this embodiment, if Figure 5As shown in the figure, when the waveform characteristics are classified as the first type of fault condition, the traveling wave protection principle based on the slope of the traveling wave head is used. To improve the anti-interference ability of the protection, the sum of the first five points of the wave head of the single-mode voltage traveling wave fault component is used as the fault characteristic, and its expression is as follows:

[0105]

[0106] Where S front The sum of the first five points of the wave head, n is the nth single-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δu 1.b is the absolute value of the single-mode voltage traveling wave fault component.

[0107] The protection action criteria are:

[0108] S front >S front.set =K rel S ref

[0109] Among them, K rel is the reliability coefficient, S ref The setting reference value under the first type of fault condition

[0110] When the waveform characteristics are classified as the second type of fault condition, the setting-free protection principle based on model error comparison is used. The frequency domain expressions of the first-mode voltage of f3 and f4 can be simplified as follows:

[0111]

[0112] Where, L b is the inductance of the boundary smoothing reactor, L MMC is the MMC equivalent inductance, Z c0 is the zero mode impedance, Z c1 is the impedance of a single mode wave, which are all known parameters of the system, k a.1 is the attenuation coefficient, τ a.1 is the dispersion coefficient, R f is the transition resistance, b0 is the basic impedance value, b1 is the impedance difference between zero mode and first mode wave, b2 is the impedance sum of zero mode and first mode wave, τ b2 , τ b1 , τ c0 , τ c1 are all time constants, c0 is the proportional coefficient, U N is the standard voltage, s is the complex frequency variable in Laplace transform, L m is the total equivalent inductance of the fault current path.

[0113] Among them, the attenuation coefficient and dispersion coefficient are fixed values, which can be determined by simulation and other methods, and the fault distance x is determined to be the full length of the line, and only the transition resistance R f The idea of ​​free setting is to determine which of the two formulas above is more consistent with the fault waveform. First, the transition resistance R is obtained by using the time domain numerical solution and interpolation of the two formulas above. f The relationship with the maximum value of the waveform within 1ms, such as Figure 7 As shown in the curve, it can be seen that under the faults f3 and f4, Δu 1.b.max With R f After the protection is activated, the maximum value of the waveform Δu in the data window is calculated first. 1.b.max ,according to Figure 7 The curves in the figure respectively give the transition resistance R in the fault models f3 and f4. f The specific value of the transition resistor R f The specific values ​​of are substituted into the original formula to obtain its time domain discrete numerical waveform and Then calculate separately and and Δu 1.b The sum of squared differences between :

[0114]

[0115] Where, They are the discrete numerical waveforms in the time domain of the f3 and f4 fault models, Δu 1.b is the absolute value of the single-mode voltage traveling wave fault component.

[0116] When the waveform characteristics are classified as the third type of fault condition, the protection principle based on the rapid extraction of the coefficient of the traveling wave front exponential term is used. This method has high reliability and sensitivity in the case of monotonic waveforms, and its protection action criterion is:

[0117] ρ>ρ set =K rel ρ ref

[0118] Where p is the exponential term coefficient, p set is the set value, K rel is the reliability coefficient, p ref is the setting reference value under the third type of fault condition, and the calculation expression of p is:

[0119]

[0120] Where n is the sampling interval, Δt is the sampling interval, t0 is the sampling start time, M is the total number of sampling points, Δu p1(t0+(j+1)nΔt) is the difference value at time t0+(j+1)nΔt, Δu p1 (t0+(j+2)nΔt) is the difference value at time t0+(j+2)nΔt, Δu p1 (t0+(j+3)nΔt) is the difference value at time t0+(j+3)nΔt.

[0121] Depend on Figure 5 It can be seen that, in the fault conditions of this category, the low resistance f5 outside the zone has only low resistance f4 left because the maximum value of the waveform is greater than the preset threshold. ref The p under the metallic property f4 can be taken.

[0122] As an example of this embodiment, the PSCAD simulation model and 105 groups of fault settings are used to verify the performance of the protection principle proposed by the present invention, and 35 dB Gaussian noise is added to the transformer measurement data. Figure 8 Contains 105 sets of simulation data, with Δu 1.b.max is the horizontal axis, S front The vertical axis is the ordinate, and the classification results are the first type of fault conditions, the second type of fault conditions, the third type of fault conditions and the direct blocking conditions are represented by points of different colors. The fault outside the zone is circled with a thin black dotted circle, and the rest of the points are faults inside the zone. In the protection principle proposed by the present invention, only the fault conditions identified as the first type of fault conditions adopt the slope-based protection principle, while the fault conditions identified by Figure 8 As can be seen, there are no cases of out-of-zone faults directly identified as Class I fault conditions. To prevent the "lockout" waveform from changing its maximum value due to uncertain factors such as noise and catadioptric interference, which could lead to its identification as a Class I fault condition, the setting value for the Class I fault condition is set to avoid the most severe "lockout" condition, which is the "new setting value" shown in the figure. At this point, there are no failures due to in-zone faults. For traditional traveling wave protection, the setting value should avoid the most severe out-of-zone fault condition, resulting in the "old setting value" shown in the figure. This setting value is higher than the "new setting value" and can cause failures due to high-resistance faults in some zones. This shows that this method improves the sensitivity of the protection. The out-of-zone fault between the new and old setting values ​​is a key factor affecting the performance of traditional traveling wave protection. Under the protection principle proposed in this invention, this part of the fault condition is handed over to the protection principles corresponding to the second and third type of fault conditions for zone discrimination, and these two protection principles are just good at handling this part of the fault conditions. The simulation results of the fault conditions with the identification results of the second and third type of fault conditions are shown in Table 2. The setting value p of the protection criterion corresponding to the third type of fault condition is ref Taking 30000, the table shows that the protections corresponding to these two categories can operate correctly and have high sensitivity.

[0123] Table 2 Protection action of the second and third type fault conditions

[0124]

[0125]

[0126] The protection device based on fault condition pre-identification provided by the embodiment of the present invention is as follows: Figure 9 As shown, Figure 9 The device block diagram of the protection device 900 based on fault condition pre-identification includes an acquisition module 901, a component extraction module 902, an identification module 903 and an execution module 904, wherein:

[0127] The acquisition module 901 is used to obtain the current signal and voltage signal after the fault of the system to be protected, compare the polarity of the voltage signal and the current signal, and obtain the fault direction of the power system;

[0128] The component extraction module 902 is used to perform phase-mode transformation on the voltage signal based on the fault direction to obtain a single-mode voltage, and extract the single-mode voltage to obtain a single-mode voltage traveling wave fault component;

[0129] The identification module 903 is used to calculate the maximum value of the single-mode voltage traveling wave fault component within a preset time window after reaching the sampling point to obtain the waveform maximum value. If the waveform maximum value is greater than a preset threshold, the waveform characteristics are obtained based on the single-mode voltage traveling wave fault component within the preset time window. The fault condition is identified based on the waveform characteristics to obtain an identification result.

[0130] The execution module 904 is used to determine the corresponding protection principle based on the identification result and execute the corresponding protection action according to the protection principle.

[0131] In one embodiment, the component extraction module 902 includes a first judgment unit and a second judgment unit, wherein:

[0132] The first judgment unit is configured to perform phase-mode transformation on the voltage signal to obtain a first-mode voltage if the fault direction is a forward fault;

[0133] The second judgment unit is used to end the protection action if the fault direction is a reverse fault.

[0134] In one embodiment, the identification module 903 includes a sampling unit and a waveform maximum calculation unit, wherein:

[0135] A sampling unit, configured to obtain, according to a preset sampling time interval, a plurality of single-mode voltage traveling wave fault components within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point;

[0136] The waveform maximum value calculation unit is used to calculate the waveform maximum value based on the total number of multiple single-mode voltage traveling wave fault components and the preset sampling time interval using the maximum value calculation formula, wherein the maximum value calculation formula is:

[0137] Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,......N

[0138]

[0139] Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

[0140] The specific implementation of the protection device based on fault condition pre-identification is substantially the same as the specific embodiment of the protection method based on fault condition pre-identification described above, and will not be described in detail herein.

[0141] In one embodiment of the present application, a computer device is provided, which includes a memory and a processor, wherein a computer program is stored in the memory, and the above steps are implemented when the processor executes the computer program; the computer device provided in this embodiment has an implementation principle and technical effects similar to those of the above method embodiment, and will not be repeated here.

[0142] In one embodiment of the present application, a computer-readable storage medium is provided, on which a computer program is stored, and the above steps are implemented when the computer program is executed by a processor; the computer-readable storage medium provided in this embodiment has an implementation principle and technical effects similar to those of the above method embodiment, and will not be repeated here.

[0143] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are 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.

[0144] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A protection method based on fault condition pre-identification, characterized in that: include: Obtaining a current signal and a voltage signal after a fault occurs in the system to be protected, comparing the polarities of the voltage signal and the current signal to obtain a fault direction of the power system; Based on the fault direction, performing phase-mode transformation on the voltage signal to obtain a single-mode voltage, and extracting the single-mode voltage to obtain a single-mode voltage traveling wave fault component; Calculating a maximum value of the single-mode voltage traveling wave fault component within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point to obtain a waveform maximum value; if the waveform maximum value is greater than a preset threshold, obtaining a waveform feature based on the single-mode voltage traveling wave fault component within the preset time window; and performing fault condition identification based on the waveform feature to obtain an identification result; Based on the identification result, a corresponding protection principle is determined, and a corresponding protection action is performed according to the protection principle.

2. The protection method based on fault condition pre-identification according to claim 1, characterized in that: The step of performing phase-mode transformation on the voltage signal based on the fault direction to obtain a single-mode voltage includes: If the fault direction is a forward fault, performing phase-mode transformation on the voltage signal to obtain a first-mode voltage; If the fault direction is a reverse fault, the protection action is terminated.

3. The protection method based on fault condition pre-identification according to claim 1, characterized in that: The calculating the maximum value of the voltage traveling wave fault component of the first mode within a preset time window after the fault component reaches the sampling point to obtain the waveform maximum value includes: According to a preset sampling time interval, a plurality of the first-mode voltage traveling wave fault components within a preset time window after the first-mode voltage traveling wave fault component reaches a sampling point are acquired; Based on the total number of the plurality of single-mode voltage traveling wave fault components and the preset sampling time interval, a maximum value calculation formula is used to calculate to obtain the waveform maximum value, wherein the maximum value calculation formula is: Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2……N Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

4. The protection method based on fault condition pre-identification according to claim 1, characterized in that: The step of identifying the fault condition according to the waveform characteristics to obtain an identification result includes: If there is a significant singular point in the waveform feature, determining that the identification result is that the system to be protected is in a first type fault condition; If the waveform characteristics all show a trend of first rising and then falling, it is determined that the identification result is that the system to be protected is in a second type of fault condition; If the waveform characteristics all show a monotonically increasing trend, it is determined that the identification result is that the system to be protected is in a third type fault condition.

5. The protection method based on fault condition pre-identification according to claim 4, characterized in that: The determining of a corresponding protection principle based on the identification result includes: If the identification result is that the system to be protected is in a first type fault condition, determining that the corresponding protection principle is a first protection principle, wherein the first protection principle is a traveling wave protection principle based on the slope of the traveling wave head; If the identification result shows that the system to be protected is in a second type fault condition, determining that the corresponding protection principle is a second protection principle, wherein the second protection principle is a setting-free protection principle based on model error comparison; If the identification result is that the system to be protected is in a third type fault condition, the corresponding protection principle is determined to be the third protection principle, wherein the third protection principle is a protection principle based on rapid extraction of traveling wave front exponential term coefficients.

6. A protection device based on fault condition pre-identification, characterized in that: It includes an acquisition module, a component extraction module, an identification module and an execution module, wherein: The acquisition module is used to acquire the current signal and voltage signal after the fault of the system to be protected, compare the polarity of the voltage signal and the current signal, and obtain the fault direction of the power system; The component extraction module is used to perform phase-mode transformation on the voltage signal based on the fault direction to obtain a single-mode voltage, and extract the single-mode voltage to obtain a single-mode voltage traveling wave fault component; The identification module is configured to calculate the maximum value of the single-mode voltage traveling wave fault component within a preset time window after the single-mode voltage traveling wave fault component reaches a sampling point to obtain a waveform maximum value. If the waveform maximum value is greater than a preset threshold, a waveform feature is obtained based on the single-mode voltage traveling wave fault component within the preset time window. The fault condition is identified based on the waveform feature to obtain an identification result. The execution module is used to determine a corresponding protection principle based on the identification result, and execute a corresponding protection action according to the protection principle.

7. The protection device based on fault condition pre-identification according to claim 6, characterized in that: The component extraction module includes a first judgment unit and a second judgment unit, wherein: The first judgment unit is configured to perform phase-mode transformation on the voltage signal to obtain a first-mode voltage if the fault direction is a forward fault; The second judgment unit is configured to terminate the protection action if the fault direction is a reverse fault.

8. The protection device based on fault condition pre-identification according to claim 6, characterized in that: The identification module includes a sampling unit and a waveform maximum calculation unit, wherein, The sampling unit is configured to obtain, according to a preset sampling time interval, a plurality of the first-mode voltage traveling wave fault components within a preset time window after the first-mode voltage traveling wave fault component reaches a sampling point; The waveform maximum value calculation unit is configured to calculate the waveform maximum value using a maximum value calculation formula based on the total number of the plurality of single-mode voltage traveling wave fault components and the preset sampling time interval, wherein the maximum value calculation formula is: Δu 1.b.max =max{Δu 1.b (nT n )},n=1,2,......N Where Δu 1.b is the absolute value of the fault component of the first-mode voltage traveling wave, Z cl is the impedance of the first-mode wave, N is the number of data in the preset time window, n is the nth first-mode voltage traveling wave fault component in the preset time window, T n is the sampling interval, Δi1 is the absolute value of the fault component of the first-mode current traveling wave.

9. A computer device, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the protection method based on fault condition pre-identification according to any one of claims 1 to 5 when executing the computer program.

10. A storage medium, characterized in that: The storage medium stores a computer program, which, when executed by a processor, implements the steps of the protection method based on fault condition pre-identification according to any one of claims 1 to 5.

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