Arc light ground fault identification method for small resistance grounding system and related equipment

Abstract

The application provides a small-resistance grounding system arc light grounding fault recognition method and related equipment, the method comprises the following steps: collecting three-phase current signals and three-phase voltage signals and processing to obtain zero sequence currents and zero sequence voltages; extracting energy characteristics according to the zero sequence voltages and judging whether the energy judgment condition is met, when the condition is met, extracting amplitude characteristics according to the zero sequence currents and judging whether the current judgment condition is met; when the current judgment condition is met, extracting zero sequence voltage waveform characteristics and calculating waveform similarity with preset arc light waveform characteristics, judging whether the similarity judgment condition is met; when the similarity judgment condition is met, determining as an arc light grounding fault. The application recognizes the fault disturbance through the zero sequence voltage energy characteristics, excludes the low-resistance fault through the zero sequence current amplitude characteristics, confirms the arc light characteristics through the waveform similarity characteristics, and comprehensively judges the three, which can accurately recognize the arc light grounding fault in the high-resistance fault scene of the traditional protection rejection, and improves the protection reliability of the small-resistance grounding system.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and in particular to a method and related equipment for identifying arc grounding faults in low-resistance grounding systems. Background Technology

[0002] In low-resistance grounding systems, when a high-resistance grounding fault occurs, the fault current and zero-sequence voltage amplitudes are relatively small, often rendering traditional zero-sequence current protection and overvoltage protection ineffective. Especially when intermittent arcing occurs at the fault point, the fault current and voltage exhibit intermittent and unstable characteristics, making traditional protection systems more prone to failure to operate.

[0003] In existing technologies, traditional relay protection mainly relies on the zero-sequence current amplitude or zero-sequence voltage amplitude for fault detection. When the grounding resistance is large, the protection setting cannot be triggered, resulting in high-resistance grounding faults not being identified and cleared in time, which affects the safe and reliable operation of the power distribution system. Summary of the Invention

[0004] The main objective of this invention is to solve the technical problem that traditional relay protection cannot effectively identify high-resistance arc grounding faults in low-resistance grounding systems. This invention provides a method for identifying arc grounding faults in a low-resistance grounding system, the method comprising: Collect the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, process the three-phase current signal and three-phase voltage signal to obtain zero-sequence current and zero-sequence voltage; Based on the zero-sequence voltage, the zero-sequence voltage energy characteristics are extracted. When the zero-sequence voltage energy characteristics meet the energy judgment conditions, the zero-sequence current amplitude characteristics are extracted based on the zero-sequence current, and it is determined whether the zero-sequence current amplitude characteristics meet the current judgment conditions. When the zero-sequence current amplitude feature meets the current judgment condition, the zero-sequence voltage waveform feature is extracted, and the waveform similarity is calculated based on the zero-sequence voltage waveform feature and the preset arc waveform feature to determine whether the waveform similarity meets the similarity judgment condition. When the waveform similarity meets the similarity judgment condition, it is determined to be an arc grounding fault.

[0005] The present invention also provides an arc grounding fault identification device for a low-resistance grounding system, the arc grounding fault identification device for a low-resistance grounding system comprising: The data acquisition module is used to acquire the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, and to process the three-phase current signal and three-phase voltage signal to obtain the zero-sequence current and zero-sequence voltage. The feature extraction module is used to extract zero-sequence voltage energy features based on the zero-sequence voltage. When the zero-sequence voltage energy features meet the energy judgment conditions, the module extracts zero-sequence current amplitude features based on the zero-sequence current and determines whether the zero-sequence current amplitude features meet the current judgment conditions. The waveform analysis module is used to extract the zero-sequence voltage waveform features when the zero-sequence current amplitude features meet the current judgment conditions, and to calculate the waveform similarity based on the zero-sequence voltage waveform features and the preset arc waveform features, and to determine whether the waveform similarity meets the similarity judgment conditions. The fault determination module is used to determine an arc grounding fault when the waveform similarity meets the similarity judgment condition.

[0006] The present invention also provides an arc grounding fault identification device for a low-resistance grounding system, comprising: a memory and at least one processor, wherein the memory stores instructions, and the memory and the at least one processor are interconnected by a line; the at least one processor calls the instructions in the memory to cause the low-resistance grounding system arc grounding fault identification device to perform the steps of the above-described low-resistance grounding system arc grounding fault identification method.

[0007] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the steps of the above-described method for identifying arc grounding faults in a low-resistance grounding system.

[0008] The aforementioned method and equipment for identifying arc grounding faults in low-resistance grounding systems acquire and process three-phase current and voltage signals to obtain zero-sequence current and zero-sequence voltage. Energy characteristics are extracted from the zero-sequence voltage to determine if energy judgment conditions are met. If met, amplitude characteristics are extracted from the zero-sequence current to determine if current judgment conditions are met. When current judgment conditions are met, waveform characteristics of the zero-sequence voltage are extracted and compared with preset arc waveform characteristics to calculate waveform similarity, determining if similarity judgment conditions are met. When similarity judgment conditions are met, the system is identified as an arc grounding fault. This invention identifies fault disturbances through zero-sequence voltage energy characteristics, eliminates low-resistance faults through zero-sequence current amplitude characteristics, and confirms arc characteristics through waveform similarity characteristics. By comprehensively judging these three factors, it can accurately identify arc grounding faults in high-resistance fault scenarios where traditional protection fails to operate, thus improving the protection reliability of low-resistance grounding systems.

[0009] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0010] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the first embodiment of the arc grounding fault identification method for a small resistance grounding system according to the present invention; Figure 2 This is a schematic diagram of the second embodiment of the arc grounding fault identification method for a small resistance grounding system according to the present invention; Figure 3 This is a schematic diagram of one embodiment of the arc grounding fault identification device for a small resistance grounding system according to the present invention; Figure 4 This is a schematic diagram of one embodiment of the arc grounding fault identification device for a small resistance grounding system according to the present invention; Figure 5 This is a schematic diagram of the single-phase grounding zero-sequence equivalent circuit of a small-resistance grounding system in an embodiment of the present invention; Figure 6 This is a schematic diagram of the bus zero-sequence voltage curve when different resistance grounding faults occur on the faulty line in an embodiment of the present invention; Figure 7 This is a schematic diagram comparing the waveforms of the zero-sequence current of the busbar and the zero-sequence current of the capacitor circuit corresponding to a low-resistance grounding fault in the protective grounding wire in an embodiment of the present invention. Figure 8 This is a schematic diagram illustrating how the Tanimoto similarity index distinguishes between arc and non-arc waveforms in an embodiment of the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0014] To facilitate understanding of this embodiment, a detailed description of the arc grounding fault identification method for a low-resistance grounding system disclosed in this invention will be provided first. For example... Figure 1 As shown, this method includes the following steps: 101. Collect the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, process the three-phase current signal and three-phase voltage signal to obtain the zero-sequence current and zero-sequence voltage; In this embodiment, the acquisition of three-phase current signals and three-phase voltage signals of the low-resistance grounding system, and the processing of the three-phase current signals and three-phase voltage signals to obtain zero-sequence current and zero-sequence voltage include: acquiring the A-phase current signal, B-phase current signal, and C-phase current signal, as well as the A-phase voltage signal, B-phase voltage signal, and C-phase voltage signal of each line in the low-resistance grounding system; summing the A-phase current signal, B-phase current signal, and C-phase current signal to obtain the sum of the three-phase currents; performing a one-third operation on the sum of the three-phase currents to obtain the zero-sequence current; and calculating the zero-sequence voltage using the symmetrical component method based on the A-phase voltage signal, B-phase voltage signal, and C-phase voltage signal.

[0015] Specifically, in practical applications, protection devices are typically equipped with current transformers and voltage transformers to collect three-phase electrical signals. Current transformers are installed on each line to collect the three-phase current flowing through that line in real time, while voltage transformers are installed on the bus side to collect the three-phase voltage of the bus. These transformers convert the large current and high voltage on the primary side into small current and low voltage on the secondary side according to a certain transformation ratio, facilitating measurement and processing by the protection device.

[0016] After acquiring the A-phase, B-phase, and C-phase current signals, the protection device sums these signals to obtain the sum of the three-phase currents. Then, it performs a one-third operation on this sum to obtain the zero-sequence current. It can be understood that, according to the principle of symmetrical component method, three-phase electrical quantities can be decomposed into positive-sequence, negative-sequence, and zero-sequence components. The zero-sequence current is defined as the arithmetic mean of the three-phase currents. Under normal operating conditions, the three-phase load is basically balanced, and the sum of the three-phase currents is close to zero; at this time, the zero-sequence current is very small or zero. However, when a ground fault occurs in the distribution network, a current path is formed between the faulty phase and the ground, the three-phase currents become unbalanced, and the sum of the three-phase currents is no longer zero; at this time, the zero-sequence current increases significantly. The zero-sequence current is an important characteristic quantity for judging ground faults.

[0017] Similarly, for voltage signal processing, the protection device calculates the zero-sequence voltage using the symmetrical component method based on the A-phase, B-phase, and C-phase voltage signals. The calculation method for the zero-sequence voltage is similar to that for the zero-sequence current; it is obtained by summing the three-phase voltage signals and taking the average value.

[0018] like Figure 5 As shown, in the zero-sequence equivalent circuit of a low-resistance grounded distribution network, when a single-phase ground fault occurs, a zero-sequence loop is formed between the fault point and the ground through the fault grounding resistance. The zero-sequence current flows from the fault point into the ground and returns to the neutral point through the neutral point grounding resistance. The magnitudes of the zero-sequence voltage and zero-sequence current are closely related to parameters such as the fault grounding resistance, the neutral point grounding resistance, and the capacitance to ground.

[0019] In a low-resistance grounded distribution network, when a high-resistance ground fault occurs, the fault grounding resistance is large, the zero-sequence current amplitude is small, and the zero-sequence voltage is correspondingly low. For example... Figure 6 As shown in the figure, the zero-sequence voltage curves under different grounding resistances indicate that the zero-sequence voltage gradually decreases as the grounding resistance increases. In this case, traditional zero-sequence current protection and zero-sequence voltage protection often fail to operate because the current or voltage amplitude does not reach the protection setting value, thus failing to clear the fault in time.

[0020] 102. Extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage. When the zero-sequence voltage energy characteristics meet the energy judgment conditions, extract the zero-sequence current amplitude characteristics based on the zero-sequence current and determine whether the zero-sequence current amplitude characteristics meet the current judgment conditions. In this embodiment, the step of extracting zero-sequence voltage energy characteristics based on the zero-sequence voltage, and when the zero-sequence voltage energy characteristics meet the energy judgment condition, extracting zero-sequence current amplitude characteristics based on the zero-sequence current, and determining whether the zero-sequence current amplitude characteristics meet the current judgment condition includes: obtaining the current zero-sequence voltage value and the zero-sequence voltage value after a delay of one period based on the zero-sequence voltage; performing a difference operation and squaring the current zero-sequence voltage value and the zero-sequence voltage value after a delay of one period to obtain the zero-sequence voltage energy characteristics; continuously monitoring the zero-sequence voltage energy characteristics; when the zero-sequence voltage energy characteristics are continuously kept below a preset energy threshold, extracting the zero-sequence current amplitude of the transient stage as the zero-sequence current amplitude characteristics based on the zero-sequence current; determining whether the zero-sequence current amplitude characteristics exceed the limit for the first time within a preset time interval; if so, excluding transient grounding faults; when the zero-sequence current amplitude characteristics are less than a preset current threshold, determining that the current judgment condition is met; when the zero-sequence current amplitude characteristics are not less than the current threshold, determining that the current judgment condition is not met.

[0021] Specifically, the zero-sequence voltage periodic differential energy characteristic can effectively reflect the sudden voltage changes during ground faults. When a ground fault occurs in a distribution network, the voltage at the fault point changes abruptly, and this change manifests as a significant difference between the zero-sequence voltages of adjacent cycles. By calculating the square of this difference, the energy characteristic can be obtained, which has good sensitivity to the occurrence and duration of the fault.

[0022] Specifically, the calculation method for the zero-sequence voltage energy characteristics is as follows: in, For the current moment, The time of one power frequency cycle, This represents the zero-sequence voltage value at the current moment. The zero-sequence voltage value after a one-cycle delay. This refers to the zero-sequence voltage energy characteristic. Under normal operating conditions, the zero-sequence voltage periodic differential energy is very small and remains at a low level. When a fault occurs, the zero-sequence voltage fluctuates significantly, and the periodic differential energy increases significantly. Especially for intermittent arcing faults, the ignition and extinguishing of the arc cause repeated changes in the zero-sequence voltage, resulting in a periodic increase and decrease in the periodic differential energy. This characteristic can be used to determine the intermittency of the fault.

[0023] Under normal operating conditions, the zero-sequence voltage periodic differential energy is very small and remains at a low level. When a fault occurs, the zero-sequence voltage fluctuates significantly, and the periodic differential energy increases significantly. Especially for intermittent arcing faults, the ignition and extinguishing of the arc cause repeated changes in the zero-sequence voltage, resulting in a periodic increase and decrease in the periodic differential energy. This characteristic can be used to determine the intermittency of the fault.

[0024] Furthermore, the protection device continuously monitors the zero-sequence voltage energy characteristic. When the zero-sequence voltage energy characteristic remains below a preset energy threshold, the zero-sequence current amplitude during the transient phase is extracted as the zero-sequence current amplitude characteristic based on the zero-sequence current.

[0025] Understandably, the zero-sequence current amplitude characteristic is used to determine the magnitude of the fault current, thereby distinguishing between low-resistance grounding faults and high-resistance grounding faults. In low-resistance grounding distribution networks, such as... Figure 7 As shown, during a high-resistivity ground fault, the zero-sequence current amplitude is much smaller than the setting value of traditional protection, causing traditional zero-sequence current protection to fail to operate. By extracting the zero-sequence current amplitude during the transient phase, more accurate current characteristics can be obtained in the early stages of the fault.

[0026] The transient phase refers to the brief period following a fault, during which the fault current has not yet reached a steady state but already contains the main characteristic information of the fault. Extracting the current amplitude during this phase can avoid signal attenuation and noise interference that may occur during the steady-state phase.

[0027] After acquiring the zero-sequence current amplitude characteristics, the protection device determines whether the zero-sequence current amplitude characteristics exceed the limit for the first time within a preset time interval. If so, the transient grounding fault is eliminated.

[0028] It should be noted that transient ground faults are usually caused by brief external disturbances, such as tree branches touching the line or birds touching the conductor. These faults are very short-lived, and the power grid can resume normal operation after the fault disappears. For these types of faults, the protection device does not need to trip the line. By judging whether the energy characteristics exceed the limit for the first time, transient faults can be effectively identified, avoiding unnecessary tripping.

[0029] When the zero-sequence current amplitude characteristic is less than a preset current threshold, the current judgment condition is met. This indicates that the fault current is small and falls within the category of high-resistance grounding faults. When the zero-sequence current amplitude characteristic is not less than the current threshold, the current judgment condition is not met. In this case, the fault current is large and may belong to a low-resistance grounding fault. Traditional zero-sequence current protection can operate effectively without entering the arc flash feature identification process.

[0030] 103. When the zero-sequence current amplitude feature meets the current judgment condition, the zero-sequence voltage waveform feature is extracted, and the waveform similarity is calculated based on the zero-sequence voltage waveform feature and the preset arc waveform feature to determine whether the waveform similarity meets the similarity judgment condition. In this embodiment, when the zero-sequence current amplitude feature meets the current judgment condition, extracting the zero-sequence voltage waveform feature includes: determining whether the zero-sequence voltage energy feature remains in a low energy state and determining whether the line zero-sequence current protection action has not been triggered; when the zero-sequence voltage energy feature remains in a low energy state and the line zero-sequence current protection action has not been triggered, performing subsequent waveform extraction steps; monitoring the zero-sequence voltage in real time; when the change amplitude of the zero-sequence voltage exceeds the disturbance identification threshold, determining that the zero-sequence voltage has been disturbed and recording the disturbance time; determining the waveform extraction time period based on the disturbance time, and extracting the zero-sequence voltage sampling data within the time period; normalizing the zero-sequence voltage sampling data and converting it into a waveform vector format to obtain the zero-sequence voltage waveform feature.

[0031] Specifically, a low-energy state means that the zero-sequence voltage periodic differential energy is small, indicating that the voltage change at the fault point is relatively gradual, which is a typical characteristic of high-resistance grounding faults. At the same time, the failure to trigger the line zero-sequence current protection indicates that the fault current is indeed small, and traditional protection devices cannot respond effectively. Only when these two conditions are met is it necessary to proceed to the waveform characteristic analysis stage.

[0032] Furthermore, the protection device monitors the zero-sequence voltage in real time. When the change in the zero-sequence voltage exceeds the disturbance identification threshold, it determines that the zero-sequence voltage has been disturbed and records the disturbance time.

[0033] Understandably, when an arcing ground fault occurs, the ignition of the arc causes a significant sudden change in the zero-sequence voltage. This sudden change can be detected by setting a disturbance identification threshold. The selection of the disturbance identification threshold needs to comprehensively consider the voltage fluctuation level during normal operation and the voltage change amplitude during a fault, ensuring that it can effectively capture fault disturbances without causing misjudgments due to normal fluctuations.

[0034] Specifically, the protection device can calculate the voltage difference between adjacent sampling points, and consider a disturbance to have occurred when the absolute value of the difference exceeds the disturbance identification threshold. Accurate recording of the disturbance moment is crucial for extracting effective waveform features, because the characteristic waveforms of arc faults are often concentrated in the time period before and after the disturbance occurs.

[0035] After recording the disturbance time, the protection device determines the waveform extraction time period based on the disturbance time and extracts the zero-sequence voltage sampling data within the time period.

[0036] In one specific implementation, the waveform extraction time period can be set to several power frequency cycles before and after the disturbance moment, such as two cycles before and after. This allows for the complete capture of the zero-sequence voltage variation characteristics during the arc ignition process. Arc faults undergo different stages during their occurrence, including ignition, stable combustion, and extinction, each with distinct waveform characteristics. Extracting the complete waveform encompassing these stages provides sufficient information for similarity calculation.

[0037] After extracting the zero-sequence voltage sampling data, the protection device normalizes the zero-sequence voltage sampling data and converts it into a waveform vector format to obtain the zero-sequence voltage waveform characteristics.

[0038] It's important to note that normalization is used to eliminate the influence of voltage amplitude differences under different fault scenarios, allowing waveform feature comparisons to focus more on waveform shape rather than amplitude magnitude. Normalization methods can employ maximum value normalization or mean-variance normalization to map waveform data to a uniform numerical range. Converting to waveform vector format means arranging the time-series sampled data into a vector form according to the sampling order, where each element corresponds to the voltage value of a sampling point. For example, if the sampling frequency is 64 points per cycle, and waveforms from 4 cycles are extracted, then the dimension of the waveform vector is 256.

[0039] After obtaining the zero-sequence voltage waveform characteristics, the protection device calculates the similarity between it and preset arcing waveform characteristics to determine whether the waveform similarity meets the similarity judgment condition. The preset arcing waveform characteristics may include multiple standard waveforms, each corresponding to different types or stages of arcing faults. The protection device calculates the similarity between the measured waveform and each standard waveform. When any similarity meets the judgment condition, the fault can be determined to have arcing characteristics.

[0040] 104. When the waveform similarity meets the similarity judgment condition, it is determined to be an arc grounding fault.

[0041] In this embodiment, after obtaining the zero-sequence voltage waveform characteristics, the protection device performs a similarity calculation between it and the preset arcing waveform characteristics. The preset arcing waveform characteristics are standard waveforms extracted from a large amount of arcing fault test data, representing the waveform characteristics of typical arcing faults.

[0042] The similarity calculation uses the Tanimoto coefficient method, which measures the degree of similarity between the measured waveform vector and the standard waveform vector by calculating the Tanimoto similarity coefficient. The Tanimoto coefficient ranges from 0 to 1, with a larger coefficient indicating greater similarity between the two waveforms.

[0043] The protection device compares the calculated Tanimoto similarity coefficient with a similarity threshold. When the similarity coefficient is greater than the similarity threshold, the waveform similarity is determined to meet the similarity judgment condition, and thus it is determined to be an arcing ground fault. The similarity threshold needs to be determined based on statistical analysis of a large amount of experimental data to ensure effective identification of arcing faults while avoiding misjudging non-arcing faults as arcing faults.

[0044] like Figure 8 As shown, the Tanimoto similarity index can effectively distinguish between arcing waveforms and non-arcing waveforms. Through this waveform similarity-based identification method, protection devices can accurately determine whether arcing characteristics exist in high-resistance grounding faults, thereby enabling timely implementation of appropriate protection measures.

[0045] In this embodiment, zero-sequence current and zero-sequence voltage are obtained by acquiring and processing three-phase current and three-phase voltage signals. Energy characteristics are extracted from the zero-sequence voltage, and it is determined whether the energy judgment condition is met. If met, amplitude characteristics are extracted from the zero-sequence current, and it is determined whether the current judgment condition is met. When the current judgment condition is met, waveform characteristics of the zero-sequence voltage are extracted and waveform similarity is calculated with preset arc waveform characteristics to determine whether the similarity judgment condition is met. When the similarity judgment condition is met, it is determined to be an arc grounding fault. This invention identifies fault disturbances through zero-sequence voltage energy characteristics, eliminates low-resistance faults through zero-sequence current amplitude characteristics, and confirms arc characteristics through waveform similarity characteristics. By comprehensively judging these three factors, it can accurately identify arc grounding faults in high-resistance fault scenarios where traditional protection fails to operate, thus improving the protection reliability of low-resistance grounding systems.

[0046] Please see Figure 2 Another embodiment of the arc grounding fault identification method for low-resistance grounding systems in this application includes: 201. Collect the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, process the three-phase current signal and three-phase voltage signal to obtain the zero-sequence current and zero-sequence voltage; 202. Extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage. When the zero-sequence voltage energy characteristics meet the energy judgment conditions, extract the zero-sequence current amplitude characteristics based on the zero-sequence current and determine whether the zero-sequence current amplitude characteristics meet the current judgment conditions. 203. When the zero-sequence current amplitude characteristic satisfies the current judgment condition, extract the zero-sequence voltage waveform characteristic; In this embodiment, steps 201-203 are similar to steps 101-103 in the first embodiment, and will not be described again here.

[0047] 204. Calculate the waveform similarity by performing a similarity algorithm on the zero-sequence voltage waveform characteristics and the preset arc waveform characteristics; In this embodiment, the step of calculating the waveform similarity based on the zero-sequence voltage waveform features and the preset arc waveform features includes: representing the zero-sequence voltage waveform features as a measured waveform vector and representing the preset arc waveform features as a standard waveform vector; calculating the inner product of the measured waveform vector and the standard waveform vector, the square of the magnitude of the measured waveform vector, and the square of the magnitude of the standard waveform vector; calculating the sum of the square of the magnitude of the measured waveform vector and the square of the magnitude of the standard waveform vector, subtracting the inner product from the sum to obtain the difference, and using the ratio of the inner product to the difference as the waveform similarity.

[0048] Specifically, a waveform vector is a mathematical vector formed by arranging the sampled data of a time series in chronological order. Assume the extracted waveform contains... With sampling points, the measured waveform vector can be represented as: ,in Indicates the first The voltage values ​​at each sampling point. Similarly, the standard waveform vector can be represented as... ,in The standard arc waveform is represented in the first... Voltage values ​​at each sampling point.

[0049] The preset arc flash waveform characteristics are typical waveform data obtained from numerous arc flash fault tests. In practical applications, a standard waveform library containing various arc flash fault types can be established, with each type corresponding to a standard waveform vector. When performing similarity calculations, the protection device can compare the waveform with each standard waveform in the library sequentially, find the standard waveform with the highest similarity, and thus determine the type of the current fault.

[0050] After representing the waveform features as a vector, the protection device calculates the inner product of the measured waveform vector and the standard waveform vector, the square of the magnitude of the measured waveform vector, and the square of the magnitude of the standard waveform vector. Then, the protection device calculates the sum of the squares of the magnitudes of the measured waveform vector and the standard waveform vector, subtracts the inner product from the sum to obtain the difference, and uses the ratio of the inner product to the difference as the waveform similarity. Specifically, this calculation method is the process of calculating the Tanimoto similarity coefficient, as shown below: Among them, molecules The inner product of the measured waveform vector and the standard waveform vector is given by the denominator, which is the sum of the squares of the magnitudes of the two vectors minus the inner product. The inner product reflects the similarity of the two vectors in direction; when the two waveforms are similar in shape and in phase, the inner product is larger. The square of the magnitude represents the energy of the waveform. By introducing this term into the denominator, waveforms with different amplitudes can be normalized.

[0051] Understandably, the Tanimoto similarity coefficient ranges from 0 to 1. When the measured waveform is completely identical to the standard waveform, the inner product equals the square of the two moduli. In this case, the subtraction term in the denominator cancels out one term, making the similarity coefficient close to 1. When the two waveforms are completely unrelated, the inner product is close to 0, and the similarity coefficient is also close to 0.

[0052] In practical applications, due to differences in measurement noise and fault conditions, even a genuine arc fault will not have a waveform that is completely identical to the standard waveform. Therefore, the similarity coefficient is usually between 0.7 and 0.95. By setting an appropriate similarity threshold, the protection device can ensure recognition accuracy while avoiding false positives and false negatives.

[0053] The Tanimoto similarity index can effectively distinguish between arcing and non-arcing waveforms. The waveform of an arcing fault shows significantly higher similarity to a standard arcing waveform than that of a non-arcing fault. Using this waveform identification method based on Tanimoto similarity, protection devices can accurately determine whether arcing characteristics exist in high-resistance grounding faults. Furthermore, before representing the zero-sequence voltage waveform features as a measured waveform vector and the preset arc waveform features as a standard waveform vector, the method further includes: conducting a test on a simulated arc grounding fault and collecting zero-sequence voltage waveform data during the test; extracting features from the zero-sequence voltage waveform data to identify the waveform features of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage; normalizing the waveform features of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage, establishing corresponding standard waveform vectors for each stage, and constructing an arc waveform feature library containing features of multiple stages as the preset arc waveform features.

[0054] Specifically, in order to establish accurate preset arc fault waveform characteristics, it is necessary to obtain typical arc fault waveform data through experiments. Protection devices or testing personnel conduct experiments on simulated arc grounding faults and collect zero-sequence voltage waveform data during the experiment.

[0055] It should be noted that simulated arcing ground fault tests are typically conducted in a laboratory environment or a dedicated test site. The test setup includes an adjustable grounding resistance, an electrode gap device, and data acquisition equipment. By adjusting the distance between the electrode gaps and the magnitude of the grounding resistance, arcing ground faults under different operating conditions can be simulated. During the test, the protection device continuously acquires zero-sequence voltage data at a high sampling frequency (e.g., 64 or 128 points per cycle), recording the complete process of the arc from ignition to extinction.

[0056] After collecting a sufficient amount of experimental data, feature extraction is performed on the zero-sequence voltage waveform data to identify the waveform characteristics of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage.

[0057] Understandably, arcing ground faults exhibit distinct phases during their occurrence. The ignition phase refers to the moment the arc is just established, at which point the zero-sequence voltage experiences a sudden jump, with the waveform showing a rapid rise or fall of sharp peaks. The stable burning phase is the period when the arc remains stable, during which the zero-sequence voltage is relatively stable, but periodic fluctuations still occur. The arc extinction phase refers to the moment the arc channel breaks, at which point the zero-sequence voltage quickly recovers to a lower level. The reignition phase is a phenomenon unique to intermittent arcing faults, where the arc reignites shortly after extinction, causing another sudden change in the zero-sequence voltage.

[0058] Specifically, feature extraction can employ time-domain analysis methods, identifying abrupt changes, peaks, and plateaus in the waveform to delineate different stages. For instance, when the rate of change of the zero-sequence voltage exceeds a preset threshold, it can be determined as the start of the ignition stage; when the rate of change of voltage decreases to a smaller range and persists for a certain period, it is determined as entering the stable combustion stage; and when the voltage suddenly drops and approaches zero, it is determined as arc extinction. Through the analysis of a large amount of experimental data, typical waveform characteristics of each stage can be extracted.

[0059] After identifying the waveform features of each stage, the waveform features of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage are normalized, and corresponding standard waveform vectors are established respectively. An arc waveform feature library containing features of multiple stages is constructed as the preset arc waveform features.

[0060] It should be noted that the purpose of normalization is to eliminate differences in voltage amplitude under different test conditions, making the standard waveform applicable to various operating conditions. Normalization methods can include maximum value normalization, which divides the waveform data by the maximum absolute value of that segment, mapping all data to the range of -1 to 1. Alternatively, mean-variance normalization can be used, subtracting the mean from the waveform data and then dividing by the standard deviation to ensure the data conforms to a standard normal distribution. Furthermore, for each stage, the waveform features extracted from multiple sets of test data can be used to obtain a representative standard waveform through averaging or clustering.

[0061] 205. Compare the waveform similarity with a similarity threshold. When the waveform similarity is less than the first similarity threshold, it is determined to be an intermittent arc grounding fault. 206. When the waveform similarity is greater than the second similarity threshold, it is determined to be a permanent high-resistance grounding fault.

[0062] In this embodiment, after calculating the waveform similarity, the protection device needs to determine the fault type based on the magnitude of the similarity. The protection device compares the waveform similarity with a similarity threshold. When the waveform similarity is less than a first similarity threshold, it is determined to be an intermittent arcing ground fault; when the waveform similarity is greater than a second similarity threshold, it is determined to be a permanent high-resistance ground fault.

[0063] It should be noted that intermittent arcing ground faults refer to a type of fault where the arc repeatedly switches between ignition and extinguishing. The waveform characteristics of this type of fault are characterized by periodic abrupt changes in zero-sequence voltage, which differs significantly from standard arcing waveforms, resulting in a relatively low similarity coefficient. When the similarity coefficient is less than the first similarity threshold, it indicates that although the measured waveform exhibits arcing characteristics, its stability is poor, consistent with the characteristics of intermittent arcing.

[0064] It is understandable that a permanent high-resistance grounding fault refers to a fault type in which the arc continues to burn stably. The waveform characteristics of this type of fault are relatively stable and have a high similarity to the standard arc waveform. When the similarity is greater than the second similarity threshold, it indicates that the measured waveform is highly consistent with the standard arc waveform, and it can be identified as a permanent arc fault.

[0065] In one specific implementation, the first similarity threshold can be set to 0.7, and the second similarity threshold can be set to 0.9. When the similarity coefficient is between 0.7 and 0.9, other criteria (such as the duration of the zero-sequence voltage periodic differential energy) can be further combined to determine the fault type. This hierarchical judgment method can improve the accuracy of fault identification and avoid misjudgment.

[0066] Furthermore, after determining the fault type, the protection device can take corresponding protective measures. For intermittent arcing ground faults, due to the unstable fault characteristics, the protection device can issue an alarm signal to remind maintenance personnel to pay attention, but will not trip immediately to avoid unnecessary power outages. For permanent high-resistance ground faults, the protection device should promptly issue a trip command to disconnect the faulty line and prevent the arcing from causing further damage to the equipment.

[0067] In this embodiment, zero-sequence current and zero-sequence voltage are obtained by acquiring and processing three-phase current and three-phase voltage signals. Energy characteristics are extracted from the zero-sequence voltage, and it is determined whether the energy judgment condition is met. If met, amplitude characteristics are extracted from the zero-sequence current, and it is determined whether the current judgment condition is met. When the current judgment condition is met, waveform characteristics of the zero-sequence voltage are extracted and waveform similarity is calculated with preset arc waveform characteristics to determine whether the similarity judgment condition is met. When the similarity judgment condition is met, it is determined to be an arc grounding fault. This invention identifies fault disturbances through zero-sequence voltage energy characteristics, eliminates low-resistance faults through zero-sequence current amplitude characteristics, and confirms arc characteristics through waveform similarity characteristics. By comprehensively judging these three factors, it can accurately identify arc grounding faults in high-resistance fault scenarios where traditional protection fails to operate, thus improving the protection reliability of low-resistance grounding systems.

[0068] The above describes the arc grounding fault identification method for a low-resistance grounding system in an embodiment of the present invention. The following describes the arc grounding fault identification device for a low-resistance grounding system in an embodiment of the present invention. Please refer to [link to device description] for details. Figure 3 One embodiment of the arc grounding fault identification device for a low-resistance grounding system in this invention includes: Data acquisition module 301 is used to acquire three-phase current signals and three-phase voltage signals of a low-resistance grounding system, and process the three-phase current signals and three-phase voltage signals to obtain zero-sequence current and zero-sequence voltage; The feature extraction module 302 is used to extract zero-sequence voltage energy features based on the zero-sequence voltage. When the zero-sequence voltage energy features meet the energy judgment conditions, the module extracts zero-sequence current amplitude features based on the zero-sequence current and determines whether the zero-sequence current amplitude features meet the current judgment conditions. The waveform analysis module 303 is used to extract the zero-sequence voltage waveform features when the zero-sequence current amplitude features meet the current judgment conditions, and to calculate the waveform similarity based on the zero-sequence voltage waveform features and the preset arc waveform features, and to determine whether the waveform similarity meets the similarity judgment conditions. The fault determination module 304 is used to determine an arc grounding fault when the waveform similarity meets the similarity judgment condition.

[0069] In this embodiment of the invention, the arc grounding fault identification device for a low-resistance grounding system operates the aforementioned arc grounding fault identification method for a low-resistance grounding system. The device acquires and processes three-phase current and voltage signals to obtain zero-sequence current and zero-sequence voltage. It extracts energy characteristics based on the zero-sequence voltage and determines whether energy judgment conditions are met. If met, it extracts amplitude characteristics based on the zero-sequence current and determines whether current judgment conditions are met. When current judgment conditions are met, it extracts zero-sequence voltage waveform characteristics and calculates waveform similarity with preset arc waveform characteristics to determine whether similarity judgment conditions are met. When similarity judgment conditions are met, the system is identified as an arc grounding fault. This invention identifies fault disturbances through zero-sequence voltage energy characteristics, eliminates low-resistance faults through zero-sequence current amplitude characteristics, and confirms arc characteristics through waveform similarity characteristics. By comprehensively judging these three factors, it can accurately identify arc grounding faults in high-resistance fault scenarios where traditional protection fails to operate, thereby improving the protection reliability of low-resistance grounding systems.

[0070] above Figure 3 The arc grounding fault identification device for a small resistance grounding system in this embodiment of the invention is described in detail from the perspective of unitized functional entities. The arc grounding fault identification device for a small resistance grounding system in this embodiment of the invention is described in detail below from the perspective of hardware processing.

[0071] Figure 4This is a schematic diagram of the structure of an arc grounding fault identification device for a low-resistance grounding system provided in an embodiment of the present invention. The low-resistance grounding system arc grounding fault identification device 400 can vary considerably due to different configurations or performance. It may include one or more central processing units (CPUs) 410 (e.g., one or more processors) and a memory 420, and one or more storage media 430 (e.g., one or more mass storage devices) storing application programs 433 or data 432. The memory 420 and storage media 430 can be temporary or persistent storage. The program stored in the storage media 430 may include one or more units (not shown in the diagram), each unit may include a series of instruction operations on the low-resistance grounding system arc grounding fault identification device 400. Furthermore, the processor 410 may be configured to communicate with the storage media 430 and execute the series of instruction operations in the storage media 430 on the low-resistance grounding system arc grounding fault identification device 400 to implement the steps of the aforementioned low-resistance grounding system arc grounding fault identification method.

[0072] The arc grounding fault identification device 400 for low-resistance grounding systems may also include one or more power supplies 440, one or more wired or wireless network interfaces 450, one or more input / output interfaces 460, and / or one or more operating systems 431, such as Windows Server, Mac OS X, Unix, Linux, FreeBSD, etc. Those skilled in the art will understand that... Figure 4 The illustrated structure of the arc grounding fault identification device for a low-resistance grounding system does not constitute a limitation on the arc grounding fault identification device for a low-resistance grounding system provided by the present invention. It may include more or fewer components than illustrated, or combine certain components, or have different component arrangements.

[0073] The present invention also provides a computer-readable storage medium, which can be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when the instructions are executed on a computer, cause the computer to perform the steps of the arc grounding fault identification method for a low-resistance grounding system.

[0074] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system, device, or unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0075] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0076] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying arc grounding faults in a low-resistance grounding system, characterized in that, The method for identifying arc grounding faults in low-resistance grounding systems includes: Collect the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, process the three-phase current signal and three-phase voltage signal to obtain zero-sequence current and zero-sequence voltage; Based on the zero-sequence voltage, the zero-sequence voltage energy characteristics are extracted. When the zero-sequence voltage energy characteristics meet the energy judgment conditions, the zero-sequence current amplitude characteristics are extracted based on the zero-sequence current, and it is determined whether the zero-sequence current amplitude characteristics meet the current judgment conditions. When the zero-sequence current amplitude feature meets the current judgment condition, the zero-sequence voltage waveform feature is extracted, and the waveform similarity is calculated based on the zero-sequence voltage waveform feature and the preset arc waveform feature to determine whether the waveform similarity meets the similarity judgment condition. When the waveform similarity meets the similarity judgment condition, it is determined to be an arc grounding fault.

2. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 1, characterized in that, The process of acquiring the three-phase current and three-phase voltage signals of the low-resistance grounding system, and processing the three-phase current and three-phase voltage signals to obtain the zero-sequence current and zero-sequence voltage includes: Collect the A-phase current signal, B-phase current signal, and C-phase current signal, as well as the A-phase voltage signal, B-phase voltage signal, and C-phase voltage signal of each line in the low-resistance grounding system; The summation of the A-phase current signal, B-phase current signal, and C-phase current signal is performed to obtain the sum of the three-phase currents. The sum of the three-phase currents is then divided into three parts to obtain the zero-sequence current. The zero-sequence voltage is calculated using the symmetrical component method based on the phase A voltage signal, phase B voltage signal, and phase C voltage signal.

3. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 1, characterized in that, The step of extracting zero-sequence voltage energy characteristics based on the zero-sequence voltage, and when the zero-sequence voltage energy characteristics meet the energy judgment condition, extracting zero-sequence current amplitude characteristics based on the zero-sequence current, and determining whether the zero-sequence current amplitude characteristics meet the current judgment condition includes: Based on the zero-sequence voltage, obtain the current zero-sequence voltage value and the zero-sequence voltage value after a delay of one period. Perform a difference calculation on the current zero-sequence voltage value and the zero-sequence voltage value after a delay of one period and square it to obtain the zero-sequence voltage energy characteristics. The zero-sequence voltage energy characteristic is continuously monitored. When the zero-sequence voltage energy characteristic remains below a preset energy threshold, the zero-sequence current amplitude during the transient phase is extracted as the zero-sequence current amplitude characteristic based on the zero-sequence current. Determine whether the zero-sequence current amplitude characteristic exceeds the limit for the first time within a preset time interval; if so, then eliminate the transient grounding fault. When the zero-sequence current amplitude characteristic is less than the preset current threshold, the current judgment condition is determined to be met; when the zero-sequence current amplitude characteristic is not less than the current threshold, the current judgment condition is determined not to be met.

4. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 1, characterized in that, When the zero-sequence current amplitude characteristic satisfies the current judgment condition, the extraction of the zero-sequence voltage waveform characteristic includes: Determine whether the zero-sequence voltage energy characteristic remains in a low energy state and whether the line zero-sequence current protection action has not been triggered. When the zero-sequence voltage energy characteristic remains in a low energy state and the line zero-sequence current protection action has not been triggered, execute the subsequent waveform extraction steps. The zero-sequence voltage is monitored in real time. When the change amplitude of the zero-sequence voltage exceeds the disturbance identification threshold, it is determined that the zero-sequence voltage has been disturbed and the disturbance time is recorded. The time period for waveform extraction is determined based on the disturbance time, and zero-sequence voltage sampling data within the time period is extracted. The zero-sequence voltage sampling data is normalized and converted into a waveform vector format to obtain the zero-sequence voltage waveform characteristics.

5. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 1, characterized in that, The step of calculating waveform similarity based on the zero-sequence voltage waveform characteristics and the preset arc waveform characteristics, and determining whether the waveform similarity meets the similarity judgment condition, includes: The waveform similarity is obtained by calculating the similarity between the zero-sequence voltage waveform characteristics and the preset arc waveform characteristics using a similarity algorithm. The waveform similarity is compared with a similarity threshold. When the waveform similarity is less than the first similarity threshold, it is determined to be an intermittent arc grounding fault. When the waveform similarity is greater than the second similarity threshold, it is determined to be a permanent high-resistance grounding fault.

6. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 5, characterized in that, The waveform similarity is calculated by performing a similarity algorithm based on the zero-sequence voltage waveform characteristics and the preset arc waveform characteristics, including: The zero-sequence voltage waveform characteristics are represented as a measured waveform vector, and the preset arc waveform characteristics are represented as a standard waveform vector; Calculate the inner product of the measured waveform vector and the standard waveform vector, the square of the magnitude of the measured waveform vector, and the square of the magnitude of the standard waveform vector; Calculate the sum of the square of the magnitude of the measured waveform vector and the square of the magnitude of the standard waveform vector, subtract the inner product from the sum to obtain the difference, and use the ratio of the inner product to the difference as the waveform similarity.

7. The method for identifying arc grounding faults in a low-resistance grounding system according to claim 6, characterized in that, Before representing the zero-sequence voltage waveform feature as a measured waveform vector and the preset arc waveform feature as a standard waveform vector, the method further includes: A simulated arc grounding fault was tested, and zero-sequence voltage waveform data was collected during the test. Feature extraction is performed on the zero-sequence voltage waveform data to identify waveform features of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage; The waveform features of the arc ignition stage, stable combustion stage, arc extinction stage, and re-ignition stage are normalized, and corresponding standard waveform vectors are established for each stage. An arc waveform feature library containing features of multiple stages is constructed as the preset arc waveform features.

8. A device for identifying arc grounding faults in a low-resistance grounding system, characterized in that, The arc grounding fault identification device for the low-resistance grounding system includes: The data acquisition module is used to acquire the three-phase current signal and three-phase voltage signal of the low-resistance grounding system, and to process the three-phase current signal and three-phase voltage signal to obtain the zero-sequence current and zero-sequence voltage. The feature extraction module is used to extract zero-sequence voltage energy features based on the zero-sequence voltage. When the zero-sequence voltage energy features meet the energy judgment conditions, the module extracts zero-sequence current amplitude features based on the zero-sequence current and determines whether the zero-sequence current amplitude features meet the current judgment conditions. The waveform analysis module is used to extract the zero-sequence voltage waveform features when the zero-sequence current amplitude features meet the current judgment conditions, and to calculate the waveform similarity based on the zero-sequence voltage waveform features and the preset arc waveform features, and to determine whether the waveform similarity meets the similarity judgment conditions. The fault determination module is used to determine an arc grounding fault when the waveform similarity meets the similarity judgment condition.

9. A device for identifying arc grounding faults in a low-resistance grounding system, characterized in that, The arc grounding fault identification device for the low-resistance grounding system includes: a memory and at least one processor, wherein the memory stores instructions; The at least one processor invokes the instructions in the memory to cause the arc grounding fault identification device for a low-resistance grounding system to perform the steps of the arc grounding fault identification method for a low-resistance grounding system as described in any one of claims 1-7.

10. A computer-readable storage medium storing instructions thereon, characterized in that, When the instruction is executed by the processor, it implements the steps of the arc grounding fault identification method for a low-resistance grounding system as described in any one of claims 1-7.

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