High-resistance grounding fault detection method and device, equipment and storage medium

Abstract

The invention provides a high-resistance grounding fault detection method, device and equipment and a storage medium, and the method comprises the steps: collecting a three-phase current and voltage signal of a small-resistance grounding system, and carrying out the processing of the three-phase current and voltage signal to obtain a zero-sequence current and a zero-sequence voltage; when the zero-sequence voltage energy characteristic meets a preset condition, calculating fault grounding resistance according to the zero-sequence current, the zero-sequence voltage and system electrical parameters; calculating a transient zero-sequence current characteristic value and a steady-state zero-sequence voltage characteristic value according to the fault grounding resistance, and comparing the characteristic values with a threshold value; and when the two characteristic values are both smaller than the corresponding threshold values, determining that the fault is a high-resistance grounding fault. According to the method, the fault grounding resistance is calculated, the transient state and steady state characteristic criteria are deduced based on the resistance, and the detection basis is converted from direct measurement of the fault current to analysis of the fault resistance characteristics, so that accurate identification of the low-current high-resistance grounding fault which is difficult to detect by a traditional method is realized.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and in particular to a method, apparatus, device, and storage medium for detecting high-resistance grounding faults. Background Technology

[0002] In power systems, low-resistance grounding systems are widely used because they can quickly clear single-phase grounding faults. However, when a high-resistance grounding fault occurs, the fault current is relatively small, and traditional zero-sequence current protection devices often cannot detect it effectively. This is because the amplitude of the zero-sequence current generated by a high-resistance grounding fault is usually lower than the protection setting, causing the protection device to fail to operate, thus allowing the fault to persist in the system for a long time.

[0003] Existing ground fault detection methods mainly rely on zero-sequence current protection, which determines the fault by setting a fixed current threshold. This method works well for detecting low-resistance ground faults, but for high-resistance ground faults, the fault current is small and its characteristics are not obvious, which can easily lead to missed detections and make it impossible to accurately identify the fault type, thus affecting the safe and stable operation of the power system. Summary of the Invention

[0004] The main objective of this invention is to solve the technical problem that high-resistance grounding faults cannot be accurately detected in the prior art due to their small fault current; This invention provides a method for detecting high-resistance grounding faults, 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; The zero-sequence voltage energy characteristics are extracted based on the zero-sequence voltage. When the zero-sequence voltage energy characteristics meet the preset energy conditions, the electrical parameters of the small resistance grounding system are obtained. The fault grounding resistance is calculated based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters. The transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are calculated based on the fault grounding resistance, the zero-sequence voltage, and the electrical parameters, respectively, and the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are compared with the corresponding threshold values. When the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold, it is determined to be a high-resistance grounding fault.

[0005] The present invention also provides a high-resistance grounding fault detection device, the high-resistance grounding fault detection device comprising: The signal acquisition module is used to acquire the three-phase current signal and the three-phase voltage signal of the low-resistance grounding system, and to process the three-phase current signal and the three-phase voltage signal to obtain the zero-sequence current and the zero-sequence voltage. The resistance calculation module is used to extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage, and when the zero-sequence voltage energy characteristics meet the preset energy conditions, to obtain the electrical parameters of the small resistance grounding system, and to calculate the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage and the electrical parameters. The feature calculation module is used to calculate the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value based on the fault grounding resistance, the zero-sequence voltage and the electrical parameters, respectively, and compare the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value with the corresponding threshold values, respectively. The fault determination module is used to determine a high-resistance grounding fault when the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold.

[0006] The present invention also provides a high-resistance grounding fault detection device, comprising: a memory and at least one processor, wherein the memory stores instructions, and the memory and the at least one processor are interconnected via a line; the at least one processor invokes the instructions in the memory to cause the high-resistance grounding fault detection device to perform the steps of the high-resistance grounding fault detection method described above.

[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 high-resistance grounding fault detection method described above.

[0008] The aforementioned high-resistance grounding fault detection method, device, equipment, and storage medium acquire three-phase current and voltage signals from a low-resistance grounding system, process them to obtain zero-sequence current and zero-sequence voltage; when the zero-sequence voltage energy characteristics meet preset conditions, the fault grounding resistance is calculated based on the zero-sequence current, zero-sequence voltage, and system electrical parameters; transient zero-sequence current characteristic values ​​and steady-state zero-sequence voltage characteristic values ​​are calculated based on the fault grounding resistance and compared with thresholds; when both characteristic values ​​are less than the corresponding thresholds, it is determined to be a high-resistance grounding fault. This invention, by calculating the fault grounding resistance and deriving transient and steady-state characteristic criteria based on this resistance, transforms the detection basis from directly measuring the fault current to analyzing the fault resistance characteristics, thereby achieving accurate identification of low-current high-resistance grounding faults that are difficult to detect using traditional methods.

[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 high-resistance grounding fault detection method in this invention; Figure 2 This is a schematic diagram of the second embodiment of the high-resistance grounding fault detection method in this invention. Figure 3 This is a schematic diagram of one embodiment of the high-resistance grounding fault detection device of the present invention; Figure 4 This is a schematic diagram of one embodiment of the high-resistance grounding fault detection device in this invention. Figure 5 This is a schematic diagram of the low-resistance grounding method in an embodiment of the present invention; Figure 6 This is a schematic diagram of the zero-sequence equivalent circuit in an embodiment of the present invention; Figure 7 This is a schematic diagram illustrating the change of zero-sequence current in a faulty circuit with transition resistance 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 high-resistance grounding fault detection method disclosed in this invention will first be described in detail. 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, such as Figure 5 As shown, the low-resistance grounding method uses a resistor connected in series between the neutral point and the ground to generate a sufficiently large zero-sequence current when a ground fault occurs, thereby triggering the protection device to operate. In practical applications, current transformers and voltage transformers installed on each line can collect the current and voltage signals of phases A, B, and C in real time. These signals are then converted from analog to digital and transmitted in digital form to the fault detection device for processing.

[0016] It should be noted that the calculation method for zero-sequence current follows the theory of symmetrical components. Zero-sequence current The calculation formula is in, This is the sum of the three-phase currents. In numerical calculations, the acquired phase A current signal will be used. B-phase current signal and C-phase current signal Perform the summation operation to obtain Then, by performing a one-third operation on this sum, the zero-sequence current can be obtained. The one-third calculation here is actually an averaging process of the three-phase currents, reflecting the magnitude of the zero-sequence component when the three phases are unbalanced. For the calculation of the zero-sequence voltage, the symmetrical component method is used. For example... Figure 6 The equivalent circuit model shown illustrates a specific mathematical relationship between the zero-sequence voltage, phase voltage, capacitance to ground, and neutral point grounding resistance under low-resistance grounding conditions. Based on the voltage divider principle, when a ground fault occurs, the phase voltage is distributed among the capacitive reactance formed by the capacitance to ground, the neutral point grounding resistance, and the fault grounding resistance, thus allowing the derivation of the formula for calculating the zero-sequence voltage.

[0017] Based on the voltage divider principle, the zero-sequence voltage can be calculated using the following formula: ; in, Phase voltage, Angular frequency, Capacitance to ground The neutral point grounding resistance, For fault grounding resistance, This represents the line resistance. In the formula... Indicates a parallel relationship, that is With 3 When connected in parallel, they participate in voltage division as a whole. This formula shows that there is a complex-domain proportional relationship between the zero-sequence voltage and the phase voltage. This proportional relationship is determined by the parallel impedance of the capacitor and resistor branches and the total impedance of the fault circuit. This form precisely reflects the voltage divider formula. Similar to the inverse relationship between voltage and impedance in a medium-resistance voltage divider, the magnitude of the zero-sequence voltage depends on the impedance distribution ratio of each branch.

[0018] Furthermore, the zero-sequence voltage amplitude is calculated as follows: ; This formula allows direct calculation of the zero-sequence voltage amplitude from the phase voltage amplitude, avoiding the complexity of complex number operations. Simultaneously, the ground capacitance current can be calculated using the following formula: in, This is the capacitance current to ground. It is the zero-sequence voltage. Angular frequency, This represents the capacitance to ground. The formula reflects the relationship between capacitor current and voltage in an AC circuit. The amplitude of the capacitor current is proportional to the voltage amplitude, angular frequency, and capacitance value, and its phase leads the voltage by 90 degrees.

[0019] The zero-sequence voltage can be derived from the above formula. From phase voltage Starting with parameters such as ground capacitance and neutral point grounding resistance, the zero-sequence voltage is calculated using symmetrical component transformation. The key here is that the formula for calculating the zero-sequence voltage establishes a relationship between the zero-sequence voltage and the phase voltage, and the phase voltage is one of the directly acquired three-phase voltage signals. In practical calculations, the zero-sequence voltage can be calculated by combining the measured A-phase voltage signal (i.e., the phase voltage) with known grid parameters (ground capacitance, neutral point grounding resistance, etc.). This method avoids the errors that may arise from directly measuring the neutral point voltage, utilizing symmetrical component theory to extract the zero-sequence component from the three-phase voltage signal.

[0020] It is worth noting that the acquired current and voltage signals usually contain certain noise and harmonic components. To improve the accuracy of fault detection, the acquired signals can be filtered in practical applications to remove high-frequency noise and harmonic interference. Filtering can be implemented using digital filters, such as low-pass or band-pass filters. The specific filtering parameters need to be determined based on the power grid frequency characteristics and sampling frequency. Calculating the zero-sequence current and zero-sequence voltage using the filtered signal yields more accurate results, thereby improving the reliability of fault identification.

[0021] 102. Extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage. When the zero-sequence voltage energy characteristics meet the preset energy conditions, obtain the electrical parameters of the small resistance grounding system. Calculate the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters. In this embodiment, the electrical parameters include neutral point grounding resistance, system-to-ground capacitance, and zero-sequence reactance.

[0022] Specifically, the neutral point grounding resistance is a resistor artificially installed between the neutral point and the earth to limit the magnitude of the fault current during a single-phase ground fault. Its resistance value is usually set according to the grid capacity and protection requirements. System-to-ground capacitance refers to the distributed capacitance of the transmission line to the ground, reflecting the capacitive coupling effect between the conductor and the earth. Its value is related to factors such as line length and conductor arrangement. Zero-sequence reactance includes the zero-sequence inductance of the line and the zero-sequence reactance of the transformer, reflecting the inductive characteristics of the zero-sequence circuit.

[0023] Specifically, the zero-sequence voltage energy characteristic is extracted by calculating the zero-sequence voltage difference between adjacent periods. The zero-sequence voltage value at the current moment is obtained. and the zero-sequence voltage value after a one-cycle delay , in The power frequency period is used. The difference between these two voltage values ​​is taken by taking the first step and squaring the result to obtain the zero-sequence voltage energy characteristic. The energy characteristic in the formula reflects the degree of change of the zero-sequence voltage within one power frequency cycle. Synchronous differential sampling is used here instead of adjacent sampling point differential sampling, mainly to filter out the periodic changes of the power frequency component itself, retaining only the non-periodic changes caused by the fault.

[0024] In practical applications, it is necessary to continuously monitor the zero-sequence voltage energy characteristics. The value. When Continuously maintain an energy level below the preset threshold This indicates that the power grid may be in a high-resistance grounding fault state. The determination of energy conditions also requires a comprehensive assessment in conjunction with the zero-sequence voltage amplitude. Based on the zero-sequence voltage amplitude calculation method given in the aforementioned formula, the fault judgment conditions can be obtained: ; in Phase voltage, The voltage threshold is set. The formula gives the relationship between the zero-sequence voltage amplitude and parameters such as fault grounding resistance and neutral point grounding resistance. When the zero-sequence voltage meets this condition, it means that the grounding resistance of the fault point is relatively large, which belongs to a high-resistance grounding fault.

[0025] Furthermore, the step of calculating the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters includes: calculating the total impedance of the zero-sequence loop based on the zero-sequence current and the zero-sequence voltage; calculating the zero-sequence equivalent impedance based on the system-to-ground capacitance, the zero-sequence reactance, and the grid angular frequency; and calculating the fault grounding resistance using the zero-sequence network equation based on the total impedance of the zero-sequence loop, the zero-sequence equivalent impedance, and the neutral point grounding resistance.

[0026] Specifically, such as Figure 6 The zero-sequence equivalent circuit shown illustrates that when a ground fault occurs, the zero-sequence current flows through the fault point, the ground, the ground capacitance, and the neutral point grounding resistance, forming a closed loop. The total impedance of the zero-sequence loop is calculated using measured zero-sequence voltage and current. Since both zero-sequence voltage and current are complex numbers (containing amplitude and phase information), the total impedance of the zero-sequence loop can be obtained by dividing the zero-sequence voltage by the zero-sequence current. This total impedance reflects the comprehensive impedance characteristics of the entire zero-sequence loop as seen from the measurement point, encompassing the effects of all components such as the ground capacitance, neutral point grounding resistance, line resistance, and fault grounding resistance. It is important to note that in actual measurements, the phase relationship between the zero-sequence voltage and zero-sequence current also contains crucial fault information; therefore, phase information must be retained during calculation, employing complex number operations.

[0027] The calculation of zero-sequence equivalent impedance needs to consider the parallel relationship between the ground capacitance branch and the neutral point grounding resistance branch. The ground capacitance exhibits capacitive reactance characteristics in AC circuits, and its impedance can be expressed as... ,in The angular frequency of the power grid. This refers to the system's capacitance to ground. The neutral point grounding resistance is typically used... This is because, in the zero-sequence equivalent circuit, the neutral point grounding resistance needs to be multiplied by 3 to reflect its actual role in the zero-sequence loop. The capacitive reactance of the ground capacitance and the neutral point grounding resistance are connected in parallel to obtain the equivalent impedance after parallel connection. Based on this, the zero-sequence reactance also needs to be considered. The zero-sequence reactance is mainly influenced by the zero-sequence inductance of the transmission line and the zero-sequence leakage reactance of the transformer. By connecting the parallel equivalent impedance in series with the zero-sequence reactance, the final zero-sequence equivalent impedance is obtained. During the calculation, it is necessary to convert components with different properties, such as capacitors, resistors, and inductors, into complex impedance forms before performing the corresponding parallel and series operations.

[0028] Based on the zero-sequence network equations, a mathematical relationship can be established between the total impedance of the zero-sequence loop, the zero-sequence equivalent impedance, the line resistance, and the fault grounding resistance. Based on Kirchhoff's voltage law, the sum of the voltage drops across each component in the zero-sequence loop equals the total zero-sequence voltage. For example, the sum of the voltage drop across the zero-sequence equivalent impedance, the voltage drop across the line resistance, and the voltage drop across the fault grounding resistance should equal the total voltage drop across the total impedance of the zero-sequence loop. Since the voltage drop across each component equals the impedance of that component multiplied by the current flowing through it, and since the components in the zero-sequence loop are connected in series and carry the same current, an additive relationship between impedances can be established. By subtracting the zero-sequence equivalent impedance and the line resistance from the total impedance of the zero-sequence loop, the impedance value corresponding to the fault grounding resistance can be obtained.

[0029] By following the above calculation process, the fault grounding resistance can be deduced from the measured zero-sequence voltage and zero-sequence current, combined with known electrical parameters. This resistance value reflects the contact state of the fault point and the resistivity of the grounding medium. When the fault grounding resistance is in the range of several hundred ohms to several thousand ohms, it can usually be identified as a high-resistance grounding fault; while if the resistance value is in the range of several ohms to tens of ohms, it may be a low-resistance or metallic grounding fault.

[0030] 103. Calculate the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value based on the fault grounding resistance, the zero-sequence voltage, and the electrical parameters, and compare the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value with the corresponding threshold values, respectively; In this embodiment, the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value reflect the electrical characteristics of a high-resistance grounding fault at different time stages. The transient zero-sequence current characteristic value describes the current response at the initial stage of the fault, while the steady-state zero-sequence voltage characteristic value reflects the voltage level after the fault stabilizes.

[0031] The calculation of the transient zero-sequence current characteristic value requires comprehensive consideration of factors such as fault grounding resistance, zero-sequence voltage amplitude, ground capacitance, and grid angular frequency. When a high-resistance grounding fault occurs, the current flowing through the fault point is significantly limited due to the large fault grounding resistance. Simultaneously, ground capacitance generates capacitive current in the initial stage of the fault; the magnitude of this current is proportional to the product of the ground capacitance and the grid angular frequency. Converting the fault grounding resistance to conductance and combining it with the susceptance generated by the ground capacitance yields an intermediate parameter reflecting the transient current characteristics. Multiplying this parameter by the zero-sequence voltage amplitude gives the transient zero-sequence current characteristic value. This characteristic value reflects the theoretically expected transient zero-sequence current level under a given fault grounding resistance condition.

[0032] The calculation of the steady-state zero-sequence voltage characteristic value focuses on the voltage distribution after the fault enters a steady state. Under steady-state conditions, the transient components have completely decayed, and the zero-sequence voltage is mainly determined by the voltage division relationship between the fault grounding resistance, the neutral grounding resistance, and the capacitance to ground. By calculating the ratio between the fault grounding resistance and the neutral grounding resistance, a coefficient reflecting the resistive voltage division characteristics can be obtained. This coefficient, combined with the influence of the capacitance to ground and the grid angular frequency, forms the voltage attenuation factor. This attenuation factor reflects the degree of attenuation of the zero-sequence voltage relative to the grid phase voltage under steady-state conditions. Multiplying the voltage attenuation factor by the grid phase voltage yields the steady-state zero-sequence voltage characteristic value.

[0033] After calculating the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value, they need to be compared with their corresponding thresholds. The transient current threshold is usually set based on the current-limiting capability of the neutral grounding resistance and the operating current of the protection device; for example, it can be set as a certain percentage of the zero-sequence current protection setting. The steady-state voltage threshold is determined based on the rated voltage of the power grid and the acceptable voltage deviation range, typically set to 10% to 20% of the rated phase voltage. By comparing the calculated characteristic values ​​with these thresholds, it can be determined whether the fault belongs to the high-resistance grounding type.

[0034] 104. When the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold, it is determined to be a high-resistance grounding fault.

[0035] In this embodiment, a dual criterion of transient zero-sequence current characteristic value and steady-state zero-sequence voltage characteristic value is used to identify high-resistance grounding faults, mainly based on the two core characteristics of high-resistance grounding faults.

[0036] From a transient perspective, high-resistance grounding faults, due to their higher grounding resistance, result in a significantly lower fault current than normal metallic grounding faults. Traditional zero-sequence current protection often uses 20A as its protection setting, while the transient zero-sequence current generated by a high-resistance grounding fault may only be a few amperes or even lower, far less than the protection setting. This is why it's necessary to determine whether the transient zero-sequence current characteristic value is less than the transient current threshold. When the transient zero-sequence current characteristic value is less than the threshold, it indicates that even considering the charging current of the ground capacitance during the transient process, the fault current is still small, which is a typical characteristic of high-resistance grounding. If the transient zero-sequence current characteristic value exceeds the threshold, it indicates that the grounding resistance at the fault point is small and does not fall under the category of high-resistance grounding.

[0037] From a steady-state perspective, the zero-sequence voltage of a high-resistance ground fault exhibits significant attenuation after entering steady state. This is because a voltage division occurs in the zero-sequence loop among the fault grounding resistance, line resistance, and neutral grounding resistance. In a high-resistance ground fault, the fault grounding resistance accounts for a larger proportion of this voltage division, resulting in a relatively low zero-sequence voltage distributed across the ground capacitance. When the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold, it indicates that the zero-sequence voltage has attenuated to a low level, reflecting the fact that the fault grounding resistance is relatively high. Conversely, if the steady-state zero-sequence voltage characteristic value is high, it indicates that the fault point is well grounded, belonging to low-resistance or metallic grounding.

[0038] It is important to emphasize that using either the transient current criterion or the steady-state voltage criterion alone can lead to misjudgments. For example, some transient faults may generate small transient currents, but these faults quickly disappear on their own and should not be identified as high-resistance grounding faults. Relying solely on the steady-state voltage criterion may be affected by factors such as grid load fluctuations and voltage regulation. Therefore, this embodiment employs a dual criterion, requiring both the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value to simultaneously meet their respective threshold conditions before identifying it as a high-resistance grounding fault. This dual-criteria design improves the accuracy and reliability of fault identification, effectively distinguishing high-resistance grounding faults from other types of grounding faults or transient disturbances.

[0039] In this embodiment, the three-phase current and voltage signals of a low-resistance grounding system are collected and processed to obtain zero-sequence current and zero-sequence voltage. When the zero-sequence voltage energy characteristics meet preset conditions, the fault grounding resistance is calculated based on the zero-sequence current, zero-sequence voltage, and system electrical parameters. The transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are calculated based on the fault grounding resistance and compared with a threshold. When both characteristic values ​​are less than the corresponding threshold, it is determined to be a high-resistance grounding fault. This invention calculates the fault grounding resistance and derives transient and steady-state characteristic criteria based on this resistance, changing the detection basis from directly measuring the fault current to analyzing the fault resistance characteristics, thereby achieving accurate identification of low-current high-resistance grounding faults that are difficult to detect using traditional methods.

[0040] Please see Figure 2 Another embodiment of the high-resistance grounding fault detection method 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 preset energy conditions, obtain the electrical parameters of the small resistance grounding system. Calculate the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters. 203. Calculate the characteristic value of the transient zero-sequence current based on the amplitude of the zero-sequence voltage, the fault grounding resistance, the system-to-ground capacitance, and the grid angular frequency; In this embodiment, calculating the transient zero-sequence current characteristic value based on the amplitude of the zero-sequence voltage, the fault grounding resistance, the system-to-ground capacitance, and the grid angular frequency includes: calculating the reciprocal of the fault grounding resistance to obtain the conductance value; calculating the product of the system-to-ground capacitance and the grid angular frequency to obtain the susceptance value; summing and taking the square root of the square of the conductance value and the square of the susceptance value to obtain an intermediate calculated value; and multiplying the amplitude of the zero-sequence voltage by the intermediate calculated value to obtain the transient zero-sequence current characteristic value.

[0041] Specifically, such as Figure 7 As shown, the transient zero-sequence current characteristic value reflects the theoretically expected magnitude of the zero-sequence current in the initial stage of a fault, considering the charging effect of ground capacitance. The conductance value is calculated by taking the reciprocal of the fault grounding resistance. The reciprocal of resistance is called conductance in circuit theory, and its unit is Siemens (S). Conductance reflects the ease with which current flows through the resistor; a larger conductance indicates a smaller resistance, making it easier for current to flow. In high-resistance grounding faults, the corresponding conductance value will be relatively small due to the larger fault grounding resistance. By converting resistance to conductance, it is convenient to unify its processing with the susceptance generated by ground capacitance. This is because in AC circuit analysis, both conductance and susceptance fall under the category of admittance, possessing the same dimensions and calculation rules.

[0042] The susceptance is calculated by multiplying the capacitance to ground by the grid angular frequency. Grid angular frequency equal ,in This is the power frequency; for a 50Hz power grid, the angular frequency is approximately 314 radians per second. The capacitance to ground... Multiply by the angular frequency to obtain the susceptance value. Susceptance is the admittance of a capacitor in an AC circuit, reflecting the capacitor's ability to conduct alternating current. A larger susceptance indicates a larger capacitance or a higher frequency, meaning a larger AC current can pass through the capacitor. It's important to note that the susceptance of a capacitor leads the voltage by 90 degrees, exhibiting capacitive characteristics, while the conductance of a resistor is in phase with the voltage.

[0043] Intermediate values ​​are obtained by squaring, summing, and taking the square root of the conductance and susceptance values. Specifically, the squares of the conductance and susceptance are added together, and then the square root of the sum is taken. This calculation method essentially calculates the magnitude of two orthogonal components. Since the conductance and susceptance components are 90 degrees out of phase, their contributions to the total admittance are orthogonal; therefore, the magnitude of the total admittance is equal to the square root of the sum of the squares of the components. This method is similar to the application of the Pythagorean theorem in the complex plane, obtaining the magnitude of the complex number by taking the square root of the sum of the squares of the real and imaginary parts.

[0044] The transient zero-sequence current characteristic value is obtained by multiplying the zero-sequence voltage amplitude by an intermediate calculated value. According to a generalized form of Ohm's law, current equals voltage multiplied by admittance. Here, the zero-sequence voltage amplitude refers to the effective or maximum value of the zero-sequence voltage, which can usually be extracted from the zero-sequence voltage calculated in the previous examples. Multiplying the zero-sequence voltage amplitude by the intermediate calculated value yields the amplitude of the transient zero-sequence current, which is the transient zero-sequence current characteristic value in this example. The formula is as follows: ; in, The zero-sequence voltage amplitude, This represents the conductance value of the fault grounding resistance. This is the susceptance value generated by the capacitance to ground. This is the aforementioned intermediate calculated value. This refers to the current setting of the protection device. The formula shows that the transient zero-sequence current should be less than or equal to the protection setting in order to determine a high-resistance grounding fault.

[0045] From a physical perspective, this calculation process comprehensively considers two main current paths in the fault loop. One is the current flowing directly into the ground through the fault grounding resistance; the magnitude of this current is inversely proportional to the fault grounding resistance—the larger the resistance, the smaller the current. The other is the charging current of the ground capacitance; the magnitude of this current is directly proportional to the ground capacitance and the frequency—the larger the capacitance or the higher the frequency, the larger the current. In high-resistance grounding faults, due to the large fault grounding resistance, the current component flowing through the resistance is relatively small, while the charging current of the ground capacitance becomes an important component of the transient zero-sequence current. By vector combining these two current components, the overall transient zero-sequence current characteristic value is obtained.

[0046] 204. Calculate the steady-state zero-sequence voltage characteristic value based on the fault grounding resistance, the neutral point grounding resistance, and the system-to-ground capacitance; In this embodiment, calculating the steady-state zero-sequence voltage characteristic value based on the fault grounding resistance, the neutral point grounding resistance, and the system-to-ground capacitance includes: calculating a resistance ratio coefficient based on the fault grounding resistance and the neutral point grounding resistance; calculating a voltage attenuation factor based on the resistance ratio coefficient, the system-to-ground capacitance, and the grid angular frequency; and calculating the steady-state zero-sequence voltage characteristic value based on the voltage attenuation factor and the grid phase voltage.

[0047] Specifically, the steady-state zero-sequence voltage characteristic value reflects the amplitude level of the zero-sequence voltage after the fault enters a steady state. After the transient process ends, the charging and discharging process of the ground capacitance is basically completed, and the current in the zero-sequence loop is mainly determined by the resistive component. At this time, the distribution of the zero-sequence voltage depends on the voltage division relationship between the fault grounding resistance and the neutral point grounding resistance.

[0048] The calculation of the resistance ratio coefficient involves the relationship between the fault grounding resistance and the neutral point grounding resistance. In the zero-sequence equivalent circuit, the fault grounding resistance appears in the form of 3Rf, while the neutral point grounding resistance also participates in voltage division in the form of 3RN. By calculating the ratio between the fault grounding resistance and the neutral point grounding resistance, a coefficient reflecting the resistive voltage division characteristics can be obtained. This coefficient describes the weight of the fault grounding resistance relative to the neutral point grounding resistance in the zero-sequence loop. When the fault grounding resistance is much larger than the neutral point grounding resistance, this ratio coefficient will be larger, meaning that most of the voltage drop will be distributed across the fault grounding resistance. Conversely, if the fault grounding resistance is small, close to the order of the neutral point grounding resistance, then the ratio coefficient will be close to 1, indicating that the voltage division effect of the two resistors is equivalent.

[0049] The calculation of the voltage attenuation factor requires further consideration of the effects of ground capacitance and grid angular frequency, in addition to the resistance ratio coefficient. Although ground capacitance no longer generates charging and discharging current under steady-state conditions, it still affects the distribution of zero-sequence voltage. This is because ground capacitance is connected in parallel with the neutral point grounding resistance, changing the equivalent impedance of the neutral point branch. By comprehensively calculating the resistance ratio coefficient, ground capacitance, and grid angular frequency, the voltage attenuation factor can be obtained. This attenuation factor reflects the degree of attenuation from phase voltage to zero-sequence voltage, or the proportional relationship between zero-sequence voltage and phase voltage. The value of the voltage attenuation factor is usually less than 1 because there is always voltage loss in the zero-sequence loop. The calculation of the zero-sequence voltage amplitude involves the combined effect of multiple parameters, as follows: As can be seen from the formula, the zero-sequence voltage amplitude Phase voltage Divide by a denominator that includes the resistance ratio and capacitive reactance. The first term in the denominator... This reflects the effect of voltage division by resistors, where This is the core part of the resistance ratio coefficient in this embodiment. The second term in the denominator... This reflects the effect of ground capacitance on voltage distribution. The square root of the entire denominator can be understood as the reciprocal of the voltage attenuation factor.

[0050] The steady-state zero-sequence voltage characteristic value is obtained by multiplying the voltage attenuation factor by the grid phase voltage. The grid phase voltage refers to the nominal phase voltage of the power grid; for a 10kV distribution network, the phase voltage is approximately the line voltage divided by the square root of 3. In practical calculations, the rated phase voltage of the power grid can be used as a reference value. Multiplying the voltage attenuation factor by the phase voltage yields the theoretically expected zero-sequence voltage amplitude under steady-state conditions; this is the steady-state zero-sequence voltage characteristic value. This characteristic value reflects the theoretical level of the steady-state zero-sequence voltage under given fault grounding resistance, neutral grounding resistance, and ground capacitance.

[0051] From a physical perspective, the steady-state zero-sequence voltage characteristic value of a high-resistance grounding fault is relatively low. This is because in a high-resistance grounding fault, the fault grounding resistance is large, occupying a large proportion of the voltage division in the zero-sequence loop. According to the voltage division principle, the larger the resistance, the higher the voltage distributed. After a large voltage is distributed across the fault grounding resistance, the remaining voltage distributed to the ground capacitance and neutral point grounding resistance branches is relatively small, resulting in a decrease in the zero-sequence voltage amplitude. This voltage attenuation phenomenon is an important characteristic of high-resistance grounding faults. Conversely, in the case of metallic or low-resistance grounding, the fault grounding resistance is very small, producing almost no voltage division effect, and the zero-sequence voltage will remain at a higher level.

[0052] It is important to emphasize that the steady-state zero-sequence voltage characteristic value may differ from the actual measured zero-sequence voltage. This difference may stem from factors such as estimation errors of electrical parameters, the influence of load current, and the function of voltage regulation devices. However, the steady-state zero-sequence voltage characteristic value remains a reliable basis for identifying high-resistance grounding faults. By comparing the steady-state zero-sequence voltage characteristic value with the steady-state voltage threshold, it can be determined whether the fault belongs to the high-resistance grounding type. When the steady-state zero-sequence voltage characteristic value is significantly smaller than the steady-state voltage threshold, combined with the judgment result of the transient zero-sequence current characteristic value, a high-resistance grounding fault can be accurately identified.

[0053] 205. Compare the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value with the corresponding threshold values ​​respectively; 206. When the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold, it is determined to be a high-resistance grounding fault.

[0054] In this embodiment, the three-phase current and voltage signals of a low-resistance grounding system are collected and processed to obtain zero-sequence current and zero-sequence voltage. When the zero-sequence voltage energy characteristics meet preset conditions, the fault grounding resistance is calculated based on the zero-sequence current, zero-sequence voltage, and system electrical parameters. The transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are calculated based on the fault grounding resistance and compared with a threshold. When both characteristic values ​​are less than the corresponding threshold, it is determined to be a high-resistance grounding fault. This invention calculates the fault grounding resistance and derives transient and steady-state characteristic criteria based on this resistance, changing the detection basis from directly measuring the fault current to analyzing the fault resistance characteristics, thereby achieving accurate identification of low-current high-resistance grounding faults that are difficult to detect using traditional methods.

[0055] The high-resistance grounding fault detection method in the embodiments of the present invention has been described above. The high-resistance grounding fault detection device in the embodiments of the present invention is described below. Please refer to [link to relevant documentation] for details on this high-resistance grounding fault detection device. Figure 3 One embodiment of the high-resistance grounding fault detection device of the present invention includes: The signal acquisition module 301 is used to acquire the three-phase current signal and the three-phase voltage signal of the low-resistance grounding system, and process the three-phase current signal and the three-phase voltage signal to obtain the zero-sequence current and the zero-sequence voltage. The resistance calculation module 302 is used to extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage, and when the zero-sequence voltage energy characteristics meet the preset energy conditions, to obtain the electrical parameters of the small resistance grounding system, and to calculate the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage and the electrical parameters. The feature calculation module 303 is used to calculate the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value according to the fault grounding resistance, the zero-sequence voltage and the electrical parameters, respectively, and compare the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value with the corresponding threshold values ​​respectively; The fault determination module 304 is used to determine a high-resistance grounding fault when the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold.

[0056] In this embodiment of the invention, the high-resistance grounding fault detection device operates the aforementioned high-resistance grounding fault detection method. The device acquires three-phase current and voltage signals from a low-resistance grounding system, processes them to obtain zero-sequence current and zero-sequence voltage. When the zero-sequence voltage energy characteristics meet preset conditions, the fault grounding resistance is calculated based on the zero-sequence current, zero-sequence voltage, and system electrical parameters. The transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are calculated based on the fault grounding resistance and compared with threshold values. When both characteristic values ​​are less than the corresponding threshold values, a high-resistance grounding fault is identified. This invention calculates the fault grounding resistance and derives transient and steady-state characteristic criteria based on this resistance, transforming the detection basis from directly measuring the fault current to analyzing the fault resistance characteristics, thereby achieving accurate identification of low-current high-resistance grounding faults that are difficult to detect using traditional methods.

[0057] above Figure 3 The high-resistance grounding fault detection device in the embodiments of the present invention will be described in detail from the perspective of unitized functional entities. The high-resistance grounding fault detection equipment in the embodiments of the present invention will be described in detail from the perspective of hardware processing.

[0058] Figure 4 This is a schematic diagram of a high-resistance grounding fault detection device 400 provided in an embodiment of the present invention. The high-resistance grounding fault detection device 400 can vary significantly due to different configurations or performance characteristics. 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 high-resistance grounding fault detection 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 high-resistance grounding fault detection device 400 to implement the steps of the above-described high-resistance grounding fault detection method.

[0059] The high-resistance grounding fault detection device 400 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 4The structure of the high-resistance grounding fault detection device shown does not constitute a limitation on the high-resistance grounding fault detection device provided by the present invention. It may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0060] 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 high-resistance grounding fault detection method.

[0061] 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.

[0062] 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.

[0063] 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 detecting high-resistance grounding faults, characterized in that, The high-resistance grounding fault detection method 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; The zero-sequence voltage energy characteristics are extracted based on the zero-sequence voltage. When the zero-sequence voltage energy characteristics meet the preset energy conditions, the electrical parameters of the small resistance grounding system are obtained. The fault grounding resistance is calculated based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters. The transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are calculated based on the fault grounding resistance, the zero-sequence voltage, and the electrical parameters, respectively, and the transient zero-sequence current characteristic value and the steady-state zero-sequence voltage characteristic value are compared with the corresponding threshold values. When the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold, it is determined to be a high-resistance grounding fault.

2. The high-resistance grounding fault detection method 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 zero-sequence current is obtained by performing a one-third operation on the sum of the three-phase currents. 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 high-resistance grounding fault detection method according to claim 1, characterized in that, The electrical parameters include neutral point grounding resistance, system-to-ground capacitance, and zero-sequence reactance.

4. The high-resistance grounding fault detection method according to claim 3, characterized in that, The calculation of the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage, and the electrical parameters includes: Calculate the total impedance of the zero-sequence loop based on the zero-sequence current and the zero-sequence voltage; Calculate the zero-sequence equivalent impedance based on the system's capacitance to ground, the zero-sequence reactance, and the grid angular frequency. The fault grounding resistance is calculated using the zero-sequence network equation based on the total impedance of the zero-sequence loop, the zero-sequence equivalent impedance, and the neutral point grounding resistance.

5. The high-resistance grounding fault detection method according to claim 3, characterized in that, The calculation of transient zero-sequence current characteristic value and steady-state zero-sequence voltage characteristic value based on the zero-sequence voltage and the electrical parameters includes: The transient zero-sequence current characteristic value is calculated based on the amplitude of the zero-sequence voltage, the fault grounding resistance, the system-to-ground capacitance, and the grid angular frequency. The steady-state zero-sequence voltage characteristic value is calculated based on the fault grounding resistance, the neutral point grounding resistance, and the system-to-ground capacitance.

6. The high-resistance grounding fault detection method according to claim 5, characterized in that, The calculation of the transient zero-sequence current characteristic value based on the amplitude of the zero-sequence voltage, the fault grounding resistance, the system-to-ground capacitance, and the grid angular frequency includes: Calculate the reciprocal of the fault grounding resistance to obtain the conductance value; The susceptance value is obtained by calculating the product of the system's capacitance to ground and the angular frequency of the power grid. The squares of the conductivity and the susceptance are summed and taken to obtain an intermediate calculated value. Multiplying the magnitude of the zero-sequence voltage by the intermediate calculated value yields the characteristic value of the transient zero-sequence current.

7. The high-resistance grounding fault detection method according to claim 5, characterized in that, The step of calculating the steady-state zero-sequence voltage characteristic value based on the fault grounding resistance, the neutral point grounding resistance, and the system-to-ground capacitance includes: Calculate the resistance ratio coefficient based on the fault grounding resistance and the neutral point grounding resistance; Calculate the voltage attenuation factor based on the resistance ratio coefficient, the system capacitance to ground, and the grid angular frequency; Calculate the steady-state zero-sequence voltage characteristic value based on the voltage decay factor and the grid phase voltage.

8. A high-resistance grounding fault detection device, characterized in that, The high-resistance grounding fault detection device includes: The signal acquisition module is used to acquire the three-phase current signal and the three-phase voltage signal of the low-resistance grounding system, and to process the three-phase current signal and the three-phase voltage signal to obtain the zero-sequence current and the zero-sequence voltage. The resistance calculation module is used to extract the zero-sequence voltage energy characteristics based on the zero-sequence voltage, and when the zero-sequence voltage energy characteristics meet the preset energy conditions, to obtain the electrical parameters of the small resistance grounding system, and to calculate the fault grounding resistance based on the zero-sequence current, the zero-sequence voltage and the electrical parameters. The feature calculation module is used to calculate the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value based on the fault grounding resistance, the zero-sequence voltage and the electrical parameters, respectively, and compare the transient zero-sequence current feature value and the steady-state zero-sequence voltage feature value with the corresponding threshold values, respectively. The fault determination module is used to determine a high-resistance grounding fault when the transient zero-sequence current characteristic value is less than the transient current threshold and the steady-state zero-sequence voltage characteristic value is less than the steady-state voltage threshold.

9. A high-resistance grounding fault detection device, characterized in that, The high-resistance grounding fault detection device 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 high-resistance ground fault detection device to perform the steps of the high-resistance ground fault detection method 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 high-resistance grounding fault detection method as described in any one of claims 1-7.

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