Fault detection method, device and equipment of resonant grounding system, medium and product

Abstract

The invention relates to a fault detection method and device for a resonant grounding system, equipment, a medium and a product. The method comprises the following steps: acquiring the current neutral point zero sequence voltage of the resonant grounding system; when it is determined that the resonance grounding system breaks down according to the current neutral point zero-sequence voltage and the zero-sequence voltage starting threshold value, a damping resistor of the resonance grounding system is cut out; the neutral point zero-sequence voltage of the resonance grounding system and the zero-sequence current of each feeder line in the resonance grounding system before and after the damping resistor is cut out are obtained; according to the neutral point zero-sequence voltage of the resonance grounding system before and after the damping resistor is cut out and the zero-sequence current of each feeder line in the resonance grounding system, determining the power frequency zero-sequence active power variation of each feeder line before and after the damping resistor is cut out; and according to each power frequency zero sequence active power variable quantity and the power change threshold value, determining a fault feeder line in each feeder line. By adopting the method, the fault feeder can be accurately identified.

Description

Technical Field

[0001] This application relates to the field of power distribution network fault detection technology, and in particular to a fault detection method, device, equipment, medium and product for a resonant grounding system. Background Technology

[0002] With the continuous advancement of medium-voltage distribution network technology and the widespread use of cable lines, the system's ground capacitance current has gradually increased. This results in a large residual current and difficulty in quickly extinguishing the arc during a single-phase ground fault. Therefore, to effectively limit the ground capacitance current, neutral point resonant grounding technology (i.e., the neutral point is grounded through an arc suppression coil) has emerged. This technology compensates for the fault capacitance current through the arc suppression coil, effectively extinguishing the arc, and is currently widely used in my country's medium-voltage distribution network. However, the electrical characteristics of a resonant grounding system are not obvious after a ground fault occurs, which places higher demands on the reliability of fault detection. In traditional resonant grounding system fault detection, the signal injection method is usually used to handle faults. By injecting a single-frequency or variable-frequency signal and detecting the signal distribution or damping characteristics in the feeder, the fault can be located. However, this method is susceptible to the influence of feeder ground capacitance and transition resistance, and arcing ground faults can interfere with the detection results, making it difficult to accurately identify the faulty feeder. Summary of the Invention

[0003] Therefore, it is necessary to provide a fault detection method, device, equipment, medium, and product for resonant grounding systems to address the above-mentioned technical problems, which can improve the accuracy of high-resistance grounding fault detection in resonant grounding systems and accurately identify faulty feeders.

[0004] In a first aspect, this application provides a fault detection method for a resonant grounding system, comprising:

[0005] Obtain the current neutral point zero-sequence voltage of the resonant grounding system; based on the current neutral point zero-sequence voltage and the zero-sequence voltage initiation threshold, determine if a fault has occurred in the resonant grounding system, and disconnect the damping resistor of the resonant grounding system; obtain the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is disconnected, and the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder in the resonant grounding system after the damping resistor is disconnected; based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder, determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is disconnected; based on the change in power frequency zero-sequence active power and the power change threshold, determine the faulty feeder among each feeder.

[0006] Secondly, this application also provides a fault detection device for a resonant grounding system, comprising: a first acquisition module for acquiring the current neutral point zero-sequence voltage of the resonant grounding system; a second acquisition module for cutting off the damping resistor of the resonant grounding system when a fault is determined to have occurred in the resonant grounding system based on the current neutral point zero-sequence voltage and a zero-sequence voltage initiation threshold; and acquiring the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is cut off, and the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder in the resonant grounding system after the damping resistor is cut off; a first determination module for determining the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder; and a fault determination module for determining the faulty feeder among the feeders based on the change in power frequency zero-sequence active power and a power change threshold.

[0007] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the various method embodiments provided in the first aspect above.

[0008] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the various method embodiments provided in the first aspect above.

[0009] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the various method embodiments provided in the first aspect above.

[0010] The aforementioned fault detection methods, devices, equipment, media, and products for resonant grounding systems acquire the current neutral point zero-sequence voltage of the resonant grounding system, providing a basic electrical quantity for subsequent fault judgment. Furthermore, a zero-sequence voltage initiation threshold is introduced, comparing the current neutral point zero-sequence voltage with the threshold to determine if a fault has occurred in the system, thereby avoiding misjudgments due to voltage fluctuations and improving the accuracy of fault detection from the source. Further, after determining that a fault has occurred in the resonant grounding system, the damping resistor of the resonant grounding system is switched off. Since switching off the damping resistor changes the impedance of the system's zero-sequence loop, the difference in zero-sequence current between the faulty feeder and the non-faulty feeder becomes more pronounced, creating conditions for accurate identification of the faulty feeder. Next, the first and second neutral point zero-sequence voltages before and after the damping resistor is switched off, as well as the first and second zero-sequence currents of each feeder, are acquired, comprehensively collecting the core electrical parameters before and after the resistor switching. This provides comprehensive and accurate data support for calculating power changes, avoiding judgment biases caused by missing data. Based on the collected voltage and current data, the change in zero-sequence active power at the power frequency of each feeder before and after the damping resistor is switched off is calculated. Focusing on the power frequency component can eliminate harmonic interference generated by thyristor operation. Simultaneously, the change in zero-sequence active power at the power frequency can intuitively reflect the difference in electrical characteristics of the feeder before and after the resistor switching, further improving the accuracy of data processing. Furthermore, this solution introduces a power change threshold, comparing the change in zero-sequence active power at the power frequency of each feeder with the threshold to identify faulty feeders. Since the change in zero-sequence active power at the power frequency of a faulty feeder before and after resistor switching is much greater than that of a non-faulty feeder, threshold screening can quickly and accurately pinpoint the faulty feeder, effectively avoiding interference from external noise or non-fault factors, thereby significantly improving the accuracy of faulty feeder identification. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 A flowchart illustrating the fault detection method for the resonant grounding system provided in this application;

[0013] Figure 2 The equivalent circuit diagram of a high-resistance grounding fault in the resonant grounding system provided in this application;

[0014] Figure 3 A flowchart illustrating the process for determining a fault in a resonant grounding system, provided in this application;

[0015] Figure 4 A schematic diagram illustrating the process for determining the adaptive detection threshold provided in this application;

[0016] Figure 5 A flowchart illustrating the determination of the change in zero-sequence active power at power frequency, provided for this application.

[0017] Figure 6 A flowchart illustrating the determination of the change in zero-sequence active power at power frequency, provided for this application.

[0018] Figure 7 (a) in this application is a schematic diagram showing the relationship between the power frequency zero-sequence current and zero-sequence voltage before the damping resistor is removed in the case of overcompensation of the resonant grounding system provided in this application;

[0019] Figure 7 (b) is a schematic diagram showing the relationship between the power frequency zero-sequence current and zero-sequence voltage before the damping resistor is removed in the undercompensated case of the resonant grounding system provided in this application;

[0020] Figure 8 A schematic diagram showing the relationship between the power frequency zero-sequence current and zero-sequence voltage of the resonant grounding system provided in this application after the damping resistor is removed;

[0021] Figure 9 (a) in this application is a schematic diagram showing the relationship between the zero-sequence current and the zero-sequence voltage amplitude of the feeder.

[0022] Figure 9 (b) is a schematic diagram showing the relationship between the zero-sequence current and the phase angle difference of the zero-sequence voltage in the feeder provided in this application;

[0023] Figure 10 A structural block diagram of the fault detection device for the resonant grounding system provided in this application;

[0024] Figure 11 An internal structural diagram of the computer device provided in this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0027] In traditional resonant grounding system fault detection, the signal injection method is commonly used. This involves injecting a single-frequency or variable-frequency signal and detecting the signal distribution or damping characteristics in the feeder to locate the fault. However, this method is susceptible to the influence of feeder-to-ground capacitance and transition resistance, and arcing grounding faults can interfere with the detection results, making it difficult to accurately identify the faulty feeder.

[0028] To address the aforementioned technical problems, an exemplary embodiment provides a fault detection method for a resonant grounding system. This method is applied to a computer device, which can be a server or a terminal. The server can be a standalone physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. The terminal can be, but is not limited to, various personal computers, laptops, smartphones, tablets, etc.

[0029] In one exemplary embodiment, such as Figure 1 As shown, a fault detection method for a resonant grounding system is provided. Taking the application of this method to a server as an example, the method includes the following steps: Wherein:

[0030] S101, obtain the current neutral point zero-sequence voltage of the resonant grounding system.

[0031] The so-called resonant grounding system is a common grounding method in medium-voltage distribution networks. Specifically, it's a system that achieves grounding by connecting an arc-suppression coil between the neutral point and ground. The main purpose of this design is to effectively extinguish the ground fault arc and reduce the risk of accident escalation by compensating for the fault capacitance current through a series arc-suppression coil at the neutral point during a single-phase ground fault. The neutral point refers to the common connection point of the three-phase windings in a three-phase power system. In a resonant grounding system, the neutral point is usually grounded through an arc-suppression coil to control the magnitude and characteristics of the ground fault current. Zero-sequence voltage describes the voltage value under asymmetrical operation or fault conditions in a three-phase system. It can be calculated using the symmetrical component method and is defined as the sum of the three-phase voltages divided by three. Under normal symmetrical operation, the zero-sequence voltage is zero; however, it will be non-zero under ground fault or other asymmetrical conditions. The current neutral point zero-sequence voltage is the zero-sequence voltage value at the neutral point during the current time period. It reflects whether the three-phase voltages of the resonant grounding system are balanced and is a core electrical quantity for determining whether a ground fault has occurred in the resonant grounding system.

[0032] Optionally, the system can actively read the neutral point zero-sequence voltage (i.e., the current neutral point zero-sequence voltage) from the resonant grounding system according to a set period, or it can receive the current neutral point zero-sequence voltage actively reported by the resonant grounding system. The set period can be determined based on empirical values, test values ​​from multiple experiments, and application requirements in actual applications, and is not specifically limited thereto.

[0033] Optionally, a pre-adjusted arc-suppression coil resonant grounding system with series damping resistors can be used.

[0034] S102, when a fault is determined in the resonant grounding system based on the current neutral point zero-sequence voltage and the zero-sequence voltage start-up threshold, the damping resistor of the resonant grounding system is cut off; and, the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is cut off are obtained, and the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder in the resonant grounding system after the damping resistor is cut off are obtained.

[0035] The zero-sequence voltage threshold is a preset voltage threshold for the neutral point zero-sequence voltage. Optionally, when the neutral point zero-sequence voltage exceeds this value, the resonant grounding system is considered to have an anomaly or fault. This threshold can be a fixed threshold set based on empirical values, test values ​​from multiple experiments, and application requirements in practical applications; no specific limitations are imposed here. The damping resistor is a resistive element connected in series in the arc-suppression coil circuit of the resonant grounding system. Its main function is to suppress system resonance and increase the active component in the grounding current, helping to highlight the electrical characteristics of the faulty feeder. Under specific fault conditions, it needs to be temporarily disconnected for fault analysis. The feeder is the power supply line used to transmit electrical energy in the resonant grounding system and is a key object for fault location; its electrical parameters must be monitored one by one to identify the faulty line. The zero-sequence current is the current generated when the phasor sum of the three-phase currents in the resonant grounding system is not zero. It usually occurs when a grounding fault occurs in the resonant grounding system or when the three-phase load is severely unbalanced. The so-called first neutral point zero-sequence voltage is the neutral point zero-sequence voltage of the resonant grounding system before the damping resistor is cut off; the so-called first zero-sequence current is the zero-sequence current of the feeder in the resonant grounding system before the damping resistor is cut off; the so-called second neutral point zero-sequence voltage is the neutral point zero-sequence voltage of the resonant grounding system after the damping resistor is cut off; the so-called second zero-sequence current is the zero-sequence current of the feeder in the resonant grounding system after the damping resistor is cut off.

[0036] For example, the current neutral point zero-sequence voltage is compared with a preset zero-sequence voltage trigger threshold. If the current neutral point zero-sequence voltage exceeds the threshold, a fault is determined to have occurred in the resonant grounding system. After the fault is confirmed, the damping resistor connected in series with the arc suppression coil in the resonant grounding system is disconnected by a control switch (such as a thyristor in the resonant grounding system). At the same time, the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder before the damping resistor is disconnected are collected by voltage and current sensors and other acquisition devices, as well as the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder after the damping resistor is disconnected. This provides complete comparative data for subsequent calculation of power changes and identification of faulty feeders.

[0037] Optionally, the equivalent circuit of a high-resistance grounding fault in a pre-adjusted arc-suppression coil resonant grounding system with series damping resistors after a fault is as follows: Figure 2 As shown. Where R is the damping resistor, L is the arc suppression coil inductance, and C... i R is the capacitance of feeder i to ground. i Let u be the resistance of feeder i to ground. 0f Indicates the zero-sequence voltage at the fault point (i.e., the zero-sequence voltage at the neutral point), i f Indicates the fault point current, i 0L i represents the zero-sequence current at the neutral point. 0i This represents the zero-sequence current of feeder i. This represents the current of the feeder capacitor i. This represents the resistive current of feeder i, and T is an anti-parallel thyristor, which is in the off state during normal system operation and in the on state after a ground fault occurs.

[0038] S103, based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder, determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off.

[0039] The so-called change in zero-sequence active power at power frequency refers to the difference in zero-sequence active power at power frequency for the same feeder before and after the damping resistor is cut off.

[0040] First, the power frequency components are extracted from the first and second neutral point zero-sequence voltages. Simultaneously, the corresponding power frequency components are also extracted from the first and second zero-sequence currents of each feeder. This eliminates interference signals such as harmonics, ensuring the accuracy of electrical quantities used in subsequent calculations. Next, for each feeder, the power frequency zero-sequence active power is calculated before the damping resistor is disconnected, based on the power frequency components of the first neutral point zero-sequence voltage and the first zero-sequence current of that feeder. Similarly, the power frequency zero-sequence active power is calculated after the damping resistor is disconnected, based on the power frequency components of the second neutral point zero-sequence voltage and the second zero-sequence current of that feeder. Finally, for each feeder, based on the zero-sequence active power at the power frequency before and after the damping resistor is cut off, determine the change in zero-sequence active power at the power frequency before and after the damping resistor is cut off. After completing the calculation for a single feeder, repeat the above steps for all feeders to finally obtain the change in zero-sequence active power at the power frequency before and after the damping resistor is cut off for all feeders.

[0041] Because the change in zero-sequence active power at power frequency is minimal before and after the damping resistor is disconnected in a normal feeder, while the zero-sequence loop impedance of a faulty feeder, which is directly connected to the ground fault point, is more significantly affected by the damping resistor, resulting in a significant change in the zero-sequence active power at power frequency. This significant difference is the core basis for subsequent identification of the faulty feeder.

[0042] S104. Based on the change in zero-sequence active power and the power change threshold of each power frequency, determine the faulty feeder in each feeder.

[0043] The so-called power change threshold is a pre-set power difference standard, which can be determined based on distribution network parameters (such as line impedance and capacitor current) and operating experience. The so-called fault feeder is a power supply line that has experienced a ground fault.

[0044] For example, a power change threshold can be determined first. This threshold can be set based on empirical values, test values ​​from multiple experiments, and application requirements in actual applications, without any limitations here. Then, the power frequency zero-sequence active power change of each feeder is compared with the power change threshold one by one. If the power change of a feeder is greater than the power change threshold, it indicates that it is significantly affected by the ground fault, and the feeder is determined to be a faulty feeder. If the power change of a feeder is less than or equal to the power change threshold, it indicates that it is not affected by the fault, and the feeder is determined to be a non-faulty feeder, that is, a healthy feeder. Finally, all comparison results are summarized, the faulty feeder is clearly marked, and the fault location is completed.

[0045] In the aforementioned fault detection method for resonant grounding systems, the current neutral point zero-sequence voltage of the resonant grounding system is acquired to provide a basic electrical quantity for subsequent fault judgment. A zero-sequence voltage initiation threshold is introduced, and the current neutral point zero-sequence voltage is compared with the zero-sequence voltage initiation threshold to determine whether a fault has occurred in the system, thereby avoiding misjudgments caused by voltage fluctuations and improving the accuracy of fault detection from the source. Furthermore, after determining that a fault has occurred in the resonant grounding system, the damping resistor of the resonant grounding system is switched off. Since switching off the damping resistor changes the impedance of the system's zero-sequence loop, the difference in zero-sequence current between the faulty feeder and the non-faulty feeder becomes more significant, creating conditions for accurate identification of the faulty feeder. Next, the first and second neutral point zero-sequence voltages before and after the damping resistor is switched off, as well as the first and second zero-sequence currents of each feeder, are acquired respectively. This complete collection of core electrical parameters before and after the resistor switching provides comprehensive and accurate data support for calculating power changes, avoiding judgment bias caused by missing data. Based on the collected voltage and current data, the change in zero-sequence active power at the power frequency of each feeder before and after the damping resistor is switched off is calculated. Focusing on the power frequency component can eliminate harmonic interference generated by thyristor operation. Simultaneously, the change in zero-sequence active power at the power frequency can intuitively reflect the difference in electrical characteristics of the feeder before and after the resistor switching, further improving the accuracy of data processing. Furthermore, this solution introduces a power change threshold, comparing the change in zero-sequence active power at the power frequency of each feeder with the threshold to identify faulty feeders. Since the change in zero-sequence active power at the power frequency of a faulty feeder before and after resistor switching is much greater than that of a non-faulty feeder, threshold screening can quickly and accurately pinpoint the faulty feeder, effectively avoiding interference from external noise or non-fault factors, thereby significantly improving the accuracy of faulty feeder identification.

[0046] Based on the above embodiments, in an exemplary embodiment, the determination of a fault in the resonant grounding system in S102 is further refined. Optionally, such as Figure 3 As shown, the following steps may be included:

[0047] S301, determine the adaptive detection threshold based on the basic parameters.

[0048] The basic parameters include the system parameters of the resonant grounding system and the expected value of its ability to withstand transition resistance.

[0049] The adaptive detection threshold is a value that can be dynamically adjusted based on the actual operating state and requirements of the resonant grounding system using fundamental parameters. The fundamental parameters are the data used to calculate the adaptive detection threshold and mainly include two types of key information: the system parameters of the resonant grounding system and the expected value of its transition resistance withstand capability. System parameters refer to the inherent electrical and structural parameters of the resonant grounding system, such as the system-to-ground capacitance. The expected transition resistance withstand capability is a pre-set performance target for the resonant grounding system, specifically the maximum allowable value of the transition resistance at the fault point when accurately detecting a ground fault in the resonant grounding system, reflecting the system's required detection capability for high-resistance ground faults.

[0050] Optionally, in a resonant grounding system with an arc-suppression coil connected in series with a damping resistor, the damping resistor suppresses the neutral point voltage after a ground fault to some extent. This makes it particularly difficult for traditional zero-sequence voltage initiation methods to accurately detect faults, especially in the case of high-resistance ground faults. To address this, this step proposes measuring the neutral point offset voltage caused by asymmetry during normal operation of the resonant grounding system and setting an adaptive zero-sequence voltage initiation threshold that avoids the maximum offset voltage during normal operation. This overcomes the limitation of traditional high-resistance fault detection criteria, which are constrained by high fixed thresholds and thus have low sensitivity.

[0051] For example, the actual system parameters of the resonant grounding system are obtained through a monitoring device or database to ensure that the system parameters accurately reflect the current state of the resonant grounding system. Next, the expected value of the transition resistance capability required for this test is determined. This value can be determined by combining the safe operation requirements of the distribution network, past fault statistics, and maintenance goals. For example, if it is necessary to improve the detection capability of high-resistance faults, a higher expected value of the transition resistance capability can be set. Then, based on the system parameters and the expected value of the transition resistance capability, the influence weight of both on the detection threshold is analyzed through algorithms (such as simulation calculations, empirical formula derivations, etc.), and an adaptive detection threshold that adapts to the current state of the resonant grounding system and the detection requirements is dynamically generated. Finally, this adaptive detection threshold is output for subsequent fault judgment, ensuring that the threshold accurately matches the actual situation of the resonant grounding system. This avoids misjudgments or omissions when the system parameters change due to a fixed threshold, improving the flexibility and accuracy of the detection.

[0052] S302, obtain the effective value of the neutral point zero-sequence voltage during normal operation of the resonant grounding system.

[0053] The so-called effective value of the neutral point zero-sequence voltage refers to the effective value of the voltage between the neutral point and the ground when the resonant grounding system is operating normally. It is further calculated from the current neutral point zero-sequence voltage (instantaneous value).

[0054] Optional, can be achieved through This formula determines the effective value of the neutral point zero-sequence voltage, where, This represents the instantaneous value of the neutral point zero-sequence voltage during normal operation of the resonant grounding system. Angular frequency, For time, This represents the effective value of the neutral point zero-sequence voltage during normal operation of the resonant grounding system. This is the maximum offset voltage during normal operation of the resonant grounding system.

[0055] S303 determines the zero-sequence voltage start-up threshold based on the effective value of the neutral point zero-sequence voltage and the adaptive detection threshold.

[0056] Optionally, the effective value of the neutral point zero-sequence voltage and the adaptive detection threshold can be multiplied to obtain the zero-sequence voltage initiation threshold. For example, the zero-sequence voltage initiation threshold can be determined based on the following formula (1):

[0057] (1)

[0058] in, The zero-sequence voltage start-up threshold; This is an adaptive detection threshold.

[0059] S304: If the current neutral point zero-sequence voltage is greater than the zero-sequence voltage start-up threshold, a fault is determined to have occurred in the resonant grounding system.

[0060] Optionally, the current neutral point zero-sequence voltage is compared with the zero-sequence voltage initiation threshold. If the current neutral point zero-sequence voltage is greater than the zero-sequence voltage initiation threshold, it is determined that a high-resistance grounding fault has occurred in the resonant grounding system. If the current neutral point zero-sequence voltage is less than or equal to the zero-sequence voltage initiation threshold, it is determined that a high-resistance grounding fault has not occurred in the resonant grounding system.

[0061] The above steps dynamically generate an adaptive detection threshold that matches the current operating state of the system and the required detection capabilities, based on the system parameters and expected transition resistance of the resonant grounding system. This ensures that the threshold is no longer fixed but can be flexibly adjusted according to changes in system parameters and actual detection needs. This fundamentally avoids the potential for misjudgments or missed judgments that may occur when system parameters change with a fixed threshold, significantly improving the flexibility and accuracy of the detection.

[0062] Furthermore, the obtained effective value of the neutral point zero-sequence voltage is multiplied by the dynamically generated adaptive detection threshold to obtain the zero-sequence voltage activation threshold. This process allows the zero-sequence voltage activation threshold to be closely combined with the current voltage level of the system and the dynamically adjusted detection sensitivity requirements, realizing personalized and precise threshold setting, rather than using a general fixed value that is detached from actual operating conditions.

[0063] By comparing the current neutral point zero-sequence voltage with a precisely calculated zero-sequence voltage trigger threshold, a fault is determined to have occurred when the zero-sequence voltage exceeds the threshold, and otherwise, no fault is determined. This judgment mechanism, based on dynamically adapted thresholds and real-time electrical quantity data, can effectively identify high-resistance grounding faults, reducing false alarms and missed alarms caused by system parameter drift, changes in operating conditions, or improper fixed threshold settings. This significantly improves the accuracy and reliability of high-resistance grounding fault judgment in resonant grounding systems, ensuring the safe and stable operation of the system.

[0064] Based on the above embodiments, in an exemplary embodiment, the determination of the adaptive detection threshold in S301 is further refined. Optionally, as... Figure 4 As shown, the following steps may be included:

[0065] S401, based on system parameters, determine the first range of values ​​for the adaptive detection threshold.

[0066] Optionally, the system parameters of the resonant grounding system include the power frequency detuning rate, power frequency damping rate, three-phase asymmetry, and total capacitance to ground of the resonant grounding system before the damping resistor is cut off.

[0067] The so-called power frequency detuning rate refers to the ratio of the difference between the inductive current of the arc suppression coil and the system-to-ground capacitive current in a resonant grounding system at the power frequency to the system-to-ground capacitive current. It is used to quantify the compensation effect of the inductive current of the arc suppression coil on the capacitive current of the system. The smaller the detuning rate, the better the compensation effect, and the easier it is to extinguish the arc during a ground fault.

[0068] The term "power frequency damping ratio" refers to the parameter describing the ability of damping components (such as damping resistors) in a resonant grounding system to attenuate oscillations at power frequency. It reveals the relative relationship between resistive and capacitive currents in the system. A higher damping ratio results in faster oscillation attenuation after disturbance, effectively suppressing resonant overvoltages and improving the stability of the system. The term "three-phase asymmetry" refers to the degree of difference in amplitude and phase between the three-phase power frequency voltages or currents in a resonant grounding system. It is commonly measured by the ratio of the difference between the maximum and minimum voltages (or currents) to the average value. It reflects the imbalance of the system's three-phase parameters (such as line impedance and load). Excessive asymmetry may lead to abnormal equipment operation. The term "total capacitance to ground" refers to the sum of the capacitances to ground of all lines and equipment (such as cables and transformers) in a resonant grounding system. It directly affects the magnitude of the system's capacitance current to ground and is a key basis for selecting the arc suppression coil capacity and calculating compensation parameters. It also influences the fault characteristics during grounding faults.

[0069] For example, the lower limit of the first value range is calculated based on the power frequency detuning rate, power frequency damping rate and three-phase asymmetry of the resonant grounding system before the damping resistor is cut off; the upper limit of the first value range is calculated based on the power frequency detuning rate, power frequency damping rate and total capacitance to ground of the resonant grounding system before the damping resistor is cut off; and then the first value range of the adaptive detection threshold can be determined based on the lower limit and the upper limit.

[0070] Optionally, the first value range should be between the neutral point offset voltage during normal system operation and the power frequency phasor amplitude of the zero-sequence voltage after a fault. For example, as shown in the following formula (2), the first value range can be expressed as:

[0071] (2)

[0072] In equation (2), k is the effective value of the three-phase asymmetry of the resonant grounding system; v is the power frequency detuning degree; and d is the power frequency damping rate. Total capacitance to ground; R f denoted as the grounding resistance; j is an imaginary number.

[0073] S402, Based on the reliability coefficient, adjust the lower limit of the first value range to obtain the second value range.

[0074] Optionally, different adaptive detection thresholds will result in varying sensitivity for high-resistance fault detection in resonant grounding systems. Choosing an adaptive detection threshold close to the neutral point offset voltage during normal system operation will increase the sensitivity but also make the system more susceptible to disturbances, reducing reliability. To ensure reliability, the lower limit of the first value range should be multiplied by a reliability coefficient. The formula is:

[0075] (3)

[0076] In equation (3), For reliability coefficient. Optionally, since the neutral point voltage deviation is small during normal system operation, to improve fault detection sensitivity, we can take... .

[0077] S403, with the second value range as a constraint, solve the objective function based on the expected value of the transition resistance capability to obtain the adaptive detection threshold.

[0078] The objective function describes the relationship between the expected value of the transition resistance tolerance and the adaptive detection threshold.

[0079] In a given distribution network, the total capacitance to ground, power frequency damping rate, and power frequency detuning rate of the resonant grounding system remain unchanged before and after a ground fault. Therefore, the value of THR determines the expected value of the high-resistance fault detection capability to withstand transition resistance. Expected value of the ability to withstand transition resistance The function (i.e., the objective function) between the adaptive detection threshold THR and the target threshold is expressed as follows:

[0080] (4)

[0081] In equation (4), The main resonant frequency.

[0082] High-resistance fault detection withstand transition resistance expected value The higher the setting, the higher the threshold. The smaller the value, the less redundancy it has with the normal-state zero pressure (and its fluctuations), making it more prone to false detection. Therefore, an adaptive detection threshold... To ensure sensitivity to high-resistance grounding faults while also having a certain degree of redundancy, the threshold value selected in equation (3) can be expressed as follows:

[0083] (5)

[0084] The above steps, by comprehensively considering core parameters such as the power frequency detuning rate, power frequency damping rate, three-phase asymmetry, and total capacitance to ground of the system before the damping resistor is cut off, calculate the first range of adaptive detection threshold values. This range is strictly limited to the neutral point offset voltage during normal system operation and the power frequency phasor amplitude of the zero-sequence voltage after a fault, effectively avoiding misjudgments or missed judgments due to improper fixed threshold settings. Specifically, the lower limit value is calculated using the three-phase asymmetry, power frequency detuning rate, and power frequency damping rate to ensure that the threshold is higher than the disturbance level during normal operation; the upper limit value is calculated using the power frequency detuning rate, power frequency damping rate, and total capacitance to ground to ensure that the threshold is lower than the characteristic voltage level after a fault occurs, thus laying the foundation for accurate fault detection.

[0085] Based on the first value range, a reliability coefficient is introduced to correct the lower limit, resulting in a second value range. This correction mechanism effectively addresses uncertainties and disturbances in system operation. Choosing a higher reliability coefficient increases the adaptive detection threshold, reduces malfunctions caused by disturbances, and enhances system reliability. Conversely, while ensuring basic reliability, selecting an empirical value such as ρ=1.5 improves fault detection sensitivity (especially for high-resistance faults) while maintaining sufficient anti-interference capability, thus achieving an optimal balance between fault detection sensitivity and system reliability.

[0086] By constraining the second value range and combining it with the expected value of the transition resistance tolerance, the final adaptive detection threshold is determined by solving the objective function. Given fixed distribution network parameters (total capacitance to ground, power frequency damping rate, power frequency detuning rate), the adaptive detection threshold directly determines the highest transition resistance value that the resonant grounding system can reliably detect. This allows for precise setting of the threshold based on the specific expectations for transition resistance tolerance in actual engineering projects, maximizing the transition resistance tolerance of the resonant grounding system under specific reliability and sensitivity requirements. It is particularly suitable for scenarios with stringent requirements for high-resistance grounding fault detection.

[0087] The core of the above steps lies in its "adaptive" characteristic, meaning the detection threshold is not a fixed value but can be dynamically calculated and adjusted based on the real-time or current key parameters of the resonant grounding system (power frequency detuning rate, power frequency damping rate, three-phase asymmetry, and total capacitance to ground). When the operating conditions of the resonant grounding system change (such as changes in total capacitance to ground due to line switching, changes in three-phase load imbalance, etc.), the adaptive detection threshold can be automatically updated accordingly, ensuring that it is always within the optimal value range. This adaptive capability makes this method widely applicable to resonant grounding systems with different structures, parameter configurations, and operating conditions, greatly enhancing its engineering practicality and system robustness.

[0088] Based on the above embodiments, in an exemplary embodiment, the determination of the change in zero-sequence active power at power frequency in S104 is further refined. Optionally, such as Figure 5 As shown, the following steps may be included:

[0089] S501, determine the first characteristic information based on the first neutral point zero-sequence voltage and each first zero-sequence current.

[0090] The first characteristic information includes the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, the first power frequency zero-sequence current amplitude coefficient and the first power frequency zero-sequence current phase angle coefficient for each feeder.

[0091] The so-called first characteristic information refers to the set of key features obtained from the voltage and current signals before the damping resistor is cut off. This is used for subsequent comparison with the features after the damping resistor is cut off, assisting in fault diagnosis. The so-called first power frequency zero-sequence voltage amplitude coefficient is the amplitude coefficient obtained after calculating the amplitude of the power frequency component of the first neutral point zero-sequence voltage, reflecting the magnitude characteristic of the power frequency zero-sequence voltage before the damping resistor is cut off. The so-called first power frequency zero-sequence voltage phase angle coefficient is the phase angle parameter obtained after performing phase analysis on the power frequency component of the first neutral point zero-sequence voltage, reflecting the phase state characteristic of the power frequency zero-sequence voltage before the damping resistor is cut off. The so-called first power frequency zero-sequence current amplitude coefficient / phase angle coefficient: For each feeder, the amplitude coefficient and phase angle parameter are calculated separately for the power frequency component of its first zero-sequence current. The former reflects the amplitude characteristic of the feeder's power frequency zero-sequence current before the damping resistor is cut off, and the latter reflects its phase characteristic.

[0092] For example, the obtained first neutral point zero-sequence voltage and the first zero-sequence current of each feeder can be decomposed using methods such as Fourier transform to obtain the power frequency component and harmonic components of the first neutral point zero-sequence voltage, as well as the power frequency component and harmonic components of the first zero-sequence current of each feeder. Further, the power frequency components of the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder are extracted. The amplitude coefficient and phase angle coefficient of the first power frequency zero-sequence voltage are determined based on the power frequency component of the first neutral point zero-sequence voltage. Similarly, the amplitude coefficient and phase angle coefficient of the first power frequency zero-sequence current of each feeder are determined based on the power frequency component of the first zero-sequence current of each feeder. Finally, the amplitude coefficient and phase angle coefficient of the first power frequency zero-sequence voltage, and the amplitude coefficient and phase angle coefficient of the first power frequency zero-sequence current of all feeders are summarized to form complete first feature information.

[0093] S502, determine the second characteristic information based on the second neutral point zero-sequence voltage and each second zero-sequence current.

[0094] The second characteristic information includes the second power frequency zero-sequence voltage amplitude coefficient, the second power frequency zero-sequence voltage phase angle coefficient, the second power frequency zero-sequence current amplitude coefficient and the second power frequency zero-sequence current phase angle coefficient for each feeder.

[0095] The so-called second feature refers to the set of key features obtained from the voltage and current signals after the damping resistor is cut off, used for subsequent comparison with the features before the damping resistor is cut off to assist in fault diagnosis. The so-called second power frequency zero-sequence voltage amplitude coefficient is the amplitude coefficient obtained after calculating the amplitude of the power frequency component of the second neutral point zero-sequence voltage, reflecting the magnitude characteristic of the power frequency zero-sequence voltage after the damping resistor is cut off. The so-called second power frequency zero-sequence voltage phase angle coefficient is the phase angle parameter obtained after performing phase analysis on the power frequency component of the second neutral point zero-sequence voltage, reflecting the phase state characteristic of the power frequency zero-sequence voltage after the damping resistor is cut off. The so-called second power frequency zero-sequence current amplitude coefficient / phase angle coefficient: For each feeder, the amplitude coefficient and phase angle parameter are calculated separately for the power frequency component of its second zero-sequence current. The former reflects the amplitude characteristic of the feeder's power frequency zero-sequence current after the damping resistor is cut off, and the latter reflects its phase characteristic.

[0096] For example, the obtained second neutral point zero-sequence voltage and the second zero-sequence current of each feeder can be decomposed using methods such as Fourier transform to obtain the power frequency component and harmonic components of the second neutral point zero-sequence voltage, as well as the power frequency component and harmonic components of the second zero-sequence current of each feeder. Further, the power frequency component of the second neutral point zero-sequence voltage and the power frequency component of the second zero-sequence current of each feeder are extracted. The amplitude coefficient and phase angle coefficient of the second power frequency zero-sequence voltage are determined based on the power frequency component of the second neutral point zero-sequence voltage. Similarly, the amplitude coefficient and phase angle coefficient of the second power frequency zero-sequence current of each feeder are determined based on the power frequency component of the second zero-sequence current of each feeder. Finally, the amplitude coefficient and phase angle coefficient of the second power frequency zero-sequence voltage, as well as the amplitude coefficient and phase angle coefficient of the second power frequency zero-sequence current of all feeders, are summarized to form complete second feature information.

[0097] S503, based on the first characteristic information and the second characteristic information, determine the change in zero-sequence active power of each feeder before and after the damping resistor is cut off.

[0098] For example, the zero-sequence active power of each feeder before the damping resistor is cut off can be determined based on the first feature information, and the zero-sequence active power of each feeder after the damping resistor is cut off can be determined based on the second feature information; then, based on the zero-sequence active power of each feeder before the damping resistor is cut off and the zero-sequence active power of each feeder after the damping resistor is cut off, the change in zero-sequence active power of each feeder before and after the damping resistor is cut off can be determined.

[0099] The above steps, through signal decomposition methods such as Fourier transform, accurately extract the power frequency component from the neutral point zero-sequence voltage and the zero-sequence current of each feeder before and after the damping resistor is cut off. This avoids the interference of harmonic components on the power frequency power calculation, making the calculation of active power change based on the power frequency component purer and more accurate, and effectively improving the accuracy of fault diagnosis.

[0100] Furthermore, by comparing the first and second characteristic information before and after the damping resistor is disconnected, the change in power frequency zero-sequence active power of each feeder is calculated. In a resonant grounding system, the series or parallel connection of the damping resistor to the arc suppression coil increases the active component in the grounding current, causing the zero-sequence current phasor of the faulty feeder to move closer to the negative real axis; while when the damping resistor is removed, the phase of the zero-sequence current of the faulty feeder will move closer to the imaginary axis. This process causes a significant change in the power frequency zero-sequence active power of the faulty feeder before and after the damping resistor is disconnected, and the change is much greater than that of a healthy feeder. It is precisely by utilizing this significant difference between the faulty feeder and the healthy feeder in this characteristic that the faulty feeder can be clearly and accurately identified, thereby achieving reliable grounding fault selection and effectively solving the problem of fault selection in resonant grounding systems.

[0101] By analyzing the changes in zero-sequence active power at power frequency, the method can adapt to the phase characteristic changes of faulty feeders under different compensation states, thereby accurately capturing fault information under various resonant grounding system operating conditions, greatly enhancing the applicability and versatility of this method in different types of resonant grounding systems.

[0102] Based on the above embodiments, in an exemplary embodiment, the determination of the change in zero-sequence active power at power frequency for each feeder before and after the damping resistor is cut off in S503 is further refined. Optionally, such as Figure 6 As shown, the following steps may be included:

[0103] S601, for each feeder, determine the first power frequency zero-sequence active power before the feeder damping resistor is cut off, based on the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, the first power frequency zero-sequence current amplitude coefficient, and the first power frequency zero-sequence current phase angle coefficient of the feeder.

[0104] In one alternative approach, the instantaneous value sequences of the zero-sequence voltage and the zero-sequence current of each feeder under the power frequency component after the damping resistor is cut off can be reconstructed in the time domain using the first power frequency zero-sequence voltage amplitude coefficient and the first power frequency zero-sequence voltage phase angle coefficient. Then, the average value of the product of the instantaneous values ​​of the zero-sequence voltage and the zero-sequence current under the power frequency component within one power frequency cycle is calculated by digital integration. This average value can be used as the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off.

[0105] In another alternative approach, for each feeder, the phase angle difference can be determined based on the phase angle coefficient of the first power frequency zero-sequence voltage and the phase angle coefficient of the first power frequency zero-sequence current of the feeder; the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off can be determined based on the cosine value of the phase angle difference, the amplitude coefficient of the first power frequency zero-sequence current of the feeder, and the amplitude coefficient of the first power frequency zero-sequence voltage.

[0106] Optionally, for each feeder, the phase angle coefficient of the first power frequency zero-sequence voltage and the phase angle coefficient of the first power frequency zero-sequence current of the feeder are subtracted to obtain the phase angle difference; the phase angle difference, the amplitude coefficient of the first power frequency zero-sequence current of the feeder, and the amplitude coefficient of the first power frequency zero-sequence voltage are multiplied to obtain the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off.

[0107] S602, based on the second power frequency zero-sequence voltage amplitude coefficient, the second power frequency zero-sequence voltage phase angle coefficient, and the second power frequency zero-sequence current amplitude coefficient and the second power frequency zero-sequence current phase angle coefficient of the feeder, determine the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off.

[0108] In one alternative approach, the instantaneous values ​​of the zero-sequence voltage and the zero-sequence current of each feeder under the power frequency component before the damping resistor is cut off can be reconstructed in the time domain using the second power frequency zero-sequence voltage amplitude coefficient and the second power frequency zero-sequence voltage phase angle coefficient. Then, the average value of the product of the instantaneous values ​​of the zero-sequence voltage and the zero-sequence current under the power frequency component within one power frequency cycle is calculated by digital integration. This average value can be used as the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off.

[0109] In another alternative approach, for each feeder, the phase angle difference can be determined based on the phase angle coefficient of the second power frequency zero-sequence voltage and the phase angle coefficient of the second power frequency zero-sequence current of the feeder; the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off can be determined based on the cosine value of the phase angle difference, the amplitude coefficient of the second power frequency zero-sequence current of the feeder, and the amplitude coefficient of the second power frequency zero-sequence voltage.

[0110] Optionally, for each feeder, the phase angle coefficient of the second power frequency zero-sequence voltage and the phase angle coefficient of the second power frequency zero-sequence current of the feeder are subtracted to obtain the phase angle difference; the phase angle difference, the amplitude coefficient of the second power frequency zero-sequence current of the feeder, and the amplitude coefficient of the second power frequency zero-sequence voltage are multiplied to obtain the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off.

[0111] S603, based on the first and second power frequency zero-sequence active power corresponding to the feeder, determine the change in power frequency zero-sequence active power of the feeder before and after the damping resistor is cut off.

[0112] Optionally, for each feeder, the difference between the first zero-sequence active power and the second zero-sequence active power at the power frequency corresponding to that feeder can be calculated to obtain the change in the zero-sequence active power at the power frequency of that feeder before and after the damping resistor is cut off.

[0113] Optionally, after a ground fault occurs in a pre-adjusted arc-suppression coil resonant grounding system with series damping resistors, the relationship between the power frequency zero-sequence current and zero-sequence voltage is as follows: Figure 7 As shown, Figure 7(a) shows the relationship between the power frequency zero-sequence current and zero-sequence voltage in an overcompensated system (i.e., an overcompensated resonant grounding system). Figure 7 (b) shows the relationship between the power frequency zero-sequence current and zero-sequence voltage in an undercompensated system (i.e., an undercompensated resonant grounding system). For neutral point current, To ensure the proper zero-sequence current of feeder i, To ensure the sum of the zero-sequence currents in the feeder, The zero-sequence current is for the faulty feeder k. To ensure the optimal difference between the phase angle coefficient of the zero-sequence current and the zero-sequence voltage in the feeder, the maximum value in actual engineering is 88°. This refers to the difference between the phase angle coefficient of the zero-sequence current at power frequency and the zero-sequence voltage of the faulty feeder. In an overcompensated system, the phase angle coefficient of the zero-sequence current at power frequency relative to the zero-sequence voltage is located in the second quadrant. The greater the power frequency detuning degree of the resonant grounding system, the larger the phase angle difference. The closer to the positive imaginary axis, the smaller the power frequency detuning degree of the resonant grounding system, and the smaller the phase angle difference in the fault feeder zero-sequence current phase relative to the zero-sequence voltage in an undercompensated system, which is located in the third quadrant. The closer to the negative imaginary axis.

[0114] Connecting a damping resistor in series or parallel with an arc suppression coil increases the active component of the grounding current, causing the zero-sequence current phasor of the faulted feeder to move closer to the negative real axis. The active current supplied to the damping resistor of the arc suppression coil For superposition Zero-sequence current of the faulty feeder after the fault. The zero-sequence current of the fault feeder after the damping resistor is removed is close to the positive imaginary axis. The smaller the damping resistor value, the larger the resistive current generated, making... The closer to 180°, the greater the change in active power of the faulty feeder before and after the damping resistor is removed, which allows for fault location.

[0115] In this resonant grounding system, various harmonic signals are easily generated during the switching process of the anti-parallel thyristor-controlled damping resistor, which affects the detection and selection of high-resistance grounding faults. Therefore, it is necessary to analyze the distribution patterns of power frequency signals and various harmonic signals during high-resistance faults in the resonant grounding system.

[0116] Since the power frequency sinusoidal signal and its harmonic signals are independent of each other in the system, the active and reactive power at different frequencies can also be calculated independently. The zero-sequence active power and zero-sequence reactive power of feeder i are defined as the sum of its power frequency sinusoidal component and its harmonic components. The zero-sequence active power and zero-sequence reactive power of feeder i can be expressed as:

[0117] (6)

[0118] In equation (6), This represents the zero-sequence fundamental frequency (power frequency signal) active power of feeder i. This represents the m-th harmonic active power of feeder i. This represents the zero-sequence fundamental reactive power of feeder i. This represents the m-th harmonic reactive power of feeder i. Represents the power frequency zero-sequence voltage amplitude coefficient. This represents the zero-sequence current amplitude coefficient of feeder i at power frequency. This represents the phase angle coefficient difference between the zero-sequence voltage and the zero-sequence current of feeder i at power frequency. This represents the amplitude coefficient of the zero-sequence voltage of the m-th harmonic. Let i be the amplitude coefficient of the zero-sequence current of the feeder under the m-th harmonic. The phase angle coefficient difference between the zero-sequence voltage and the zero-sequence current of feeder i under the m-th harmonic is given.

[0119] For the power frequency component, the series connection of the arc suppression coil increases the active component in the grounding current, causing the phasor of the zero-sequence current in the fault feeder to approach 180°. This is achieved by selecting damping resistors of different values; the larger the resistive current generated, the closer it is to 180°. After a ground fault is detected, the thyristor operates, causing the damping resistor to deactivate. The phase of the zero-sequence current in the fault feeder then moves closer to the imaginary axis, while its projection on the imaginary axis remains unchanged. The relationship between the power frequency zero-sequence current and the zero-sequence voltage is as follows: Figure 8 As shown.

[0120] In a resonant grounding system, considering the influence of harmonics, the definition is... (m>1) indicates the degree of compensation of the inductive current generated by the arc suppression coil for the capacitive current under the m-th harmonic component of the arc suppression. The ratio of resistive current to capacitive current under the m-th harmonic component can be expressed as:

[0121] (7)

[0122] In equation (7), v represents the power frequency detuning degree; d represents the power frequency damping ratio. In equation (7), when m=1, the calculated values ​​are the power frequency detuning degree and the power frequency damping ratio. By definition... and The implication is that the range of damping rate and detuning degree is extended to broadband signals, indicating that the compensation effect of the arc suppression coil and the damping effect of the system are independent of each other for signals of different frequencies.

[0123] The zero-sequence current of each feeder is obtained by superimposing the zero-sequence currents under the power frequency component and harmonic component. The zero-sequence voltage of the neutral point is obtained by superimposing the zero-sequence voltages under the power frequency component and harmonic component. Both the feeder zero-sequence current and zero-sequence voltage at each frequency can be expressed as the steady-state fault current at that frequency multiplied by an amplitude coefficient and then rotated by a certain angle. The multiplier and the rotation angle are respectively represented as the amplitude coefficient. and phase angle coefficient Their essence is the amplitude ratio and phase difference, respectively, and the amplitude coefficient and phase coefficient are different at different frequencies. According to Figure 2 The equivalent circuit of a high-resistance grounding fault in a series-damped resonant grounding system is shown, along with the zero-sequence current of a healthy feeder at different frequencies. Zero-sequence current of faulty feeder Zero-sequence voltage Amplitude coefficient and phase angle coefficient The expressions are shown in Table 1, where, To ensure the optimal ratio of feeder i's capacitance to ground to the total system capacitance, , To ensure the optimal ratio of feeder i's resistance to ground to the total system resistance, . , These are the ratios of the faulty feeder's capacitance to ground to the total system capacitance and the ratio of its resistance to ground to the total system resistance. The main resonant frequency, This represents the total capacitance to ground.

[0124] Table 1 Expressions for Amplitude Coefficient and Phase Coefficient

[0125]

[0126] As shown in Table 1, after a single-phase ground fault occurs, the power frequency zero-sequence voltage of the resonant grounding system is... The expression is:

[0127] (8)

[0128] In the formula, zero-sequence voltage at power frequency amplitude coefficient, zero-sequence voltage at power frequency The phase angle coefficient, The system's power frequency detuning rate, The system's power frequency damping ratio. A sound feeder with power frequency zero-sequence current. The expression is:

[0129] (9)

[0130] In the formula, To improve the feeder i power frequency zero-sequence current amplitude coefficient, To improve the feeder i power frequency zero-sequence current The phase angle coefficient. Faulty feeder k-frequency zero-sequence current meter. The expression is:

[0131] (10)

[0132] In the formula, For the faulty feeder k power frequency zero-sequence current amplitude coefficient, For the faulty feeder k power frequency zero-sequence current The phase angle coefficient.

[0133] From equations (9) to (10), it can be seen that the amplitude coefficient and phase angle coefficient of the faulty feeder and the non-faulty feeder are significantly different. The amplitude coefficient of the faulty feeder is much larger than that of the non-faulty feeder, and the phase angle coefficients are not in the same quadrant. The amplitude coefficient, phase angle coefficient, and power frequency damping ratio of the power frequency zero-sequence signal in the resonant grounding system are related. With detuning rate This is related to the fact that after a single-phase ground fault occurs, the thyristor operates and removes the damping resistor, thus affecting the system's power frequency damping rate. The damping ratio changes before and after the damping resistor is removed. , They can be represented as:

[0134] (11)

[0135] In equation (11), for , , The total resistance to ground, It is a damping resistor.

[0136] After a ground fault occurs, removing the damping resistor will reduce the zero-sequence active power component of the faulty feeder. Before the damping resistor is removed, the zero-sequence active power of the healthy feeder and the faulty feeder is:

[0137] (12)

[0138] After the damping resistor is removed, due to the change in the system damping rate, the zero-sequence active power at power frequency of the healthy feeder and the faulty feeder after the damping resistor is removed can also be calculated. and The differences in zero-sequence active power at power frequency between the healthy and faulty feeders before and after damping is removed are as follows:

[0139] (13)

[0140] The difference in zero-sequence active power at power frequency before and after the damping resistor is removed is much greater for a faulty feeder than for a healthy feeder. Therefore, a single-phase ground fault protection fault selection criterion based on the change in zero-sequence active power can be set, with the following expression:

[0141] (14)

[0142] In the formula, This represents the maximum zero-sequence power change occurring on a non-faulty feeder. To allow for a certain margin when selecting a feeder during a ground fault, this setting is... The reliability coefficient for selecting the line in case of grounding fault can be set to 1.2. The product of these is the power change threshold mentioned above.

[0143] It should be noted that the above process of calculating the active power before and after the damping resistor is removed using damping ratio and detuning degree at different frequencies is a theoretical derivation to prove the difference in active power before and after the damping resistor is removed, and this can be used as a criterion for line selection. In practical applications, however, it can be directly used... Figure 5 and Figure 6 The steps shown directly calculate the change in zero-sequence active power at the power frequency.

[0144] Based on the above embodiments, in an exemplary embodiment, the fault detection method of the resonant grounding system may include the following steps:

[0145] (1) Obtain the current neutral point zero-sequence voltage of the resonant grounding system.

[0146] (2) Determine the first range of values ​​for the adaptive detection threshold based on the system parameters.

[0147] (3) Based on the reliability coefficient, adjust the lower limit of the first value range to obtain the second value range;

[0148] (4) Using the second range of values ​​as a constraint, the objective function is solved according to the expected value of the ability to withstand transition resistance, and the adaptive detection threshold is obtained.

[0149] (5) Obtain the effective value of the neutral point zero-sequence voltage when the resonant grounding system is running normally.

[0150] (6) Determine the zero-sequence voltage start-up threshold based on the effective value of the neutral point zero-sequence voltage and the adaptive detection threshold.

[0151] (7) If the current neutral point zero-sequence voltage is greater than the zero-sequence voltage start-up threshold, it is determined that the resonant grounding system has failed.

[0152] (8) In the event that a fault has occurred in the resonant grounding system, the damping resistor of the resonant grounding system is cut off; and the first neutral point zero-sequence voltage and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is cut off are obtained, and the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder in the resonant grounding system after the damping resistor is cut off are obtained.

[0153] (9) Determine the first characteristic information based on the first neutral point zero-sequence voltage and each first zero-sequence current.

[0154] (10) Determine the second characteristic information based on the second neutral point zero-sequence voltage and each second zero-sequence current.

[0155] (11) For each feeder, determine the first phase angle difference based on the first power frequency zero-sequence voltage phase angle coefficient and the first power frequency zero-sequence current phase angle coefficient of the feeder.

[0156] (12) Determine the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off based on the first phase angle difference, the first power frequency zero-sequence current amplitude coefficient of the feeder, and the first power frequency zero-sequence voltage amplitude coefficient.

[0157] (13) For each feeder, determine the second phase angle difference based on the second power frequency zero-sequence voltage phase angle coefficient and the second power frequency zero-sequence current phase angle coefficient of the feeder.

[0158] (14) Determine the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off, based on the second phase angle difference, the second power frequency zero-sequence current amplitude coefficient of the feeder, and the second power frequency zero-sequence voltage amplitude coefficient.

[0159] (15) Based on the first power frequency zero-sequence active power and the second power frequency zero-sequence active power corresponding to the feeder, determine the change in power frequency zero-sequence active power of the feeder before and after the damping resistor is cut off.

[0160] (16) Determine the faulty feeder in each feeder based on the change in zero-sequence active power and the power change threshold of each power frequency.

[0161] The specific implementation methods of steps (1) to (16) are the same as those in the above method embodiments, and will not be repeated here.

[0162] This fault detection method for resonant grounding systems addresses the issue of weak high-resistance fault characteristic signals, leading to low accuracy in fault detection results. By setting an adaptive zero-sequence voltage threshold, it avoids the maximum unbalanced voltage of the system, effectively improving the sensitivity of high-resistance fault detection in resonant grounding systems. Considering the influence of system capacitive current, compensation degree, and asymmetry, it is applicable to resonant grounding distribution networks with varying degrees of asymmetry. By decomposing the power frequency signals and harmonic signals of the neutral point voltage and zero-sequence current of each feeder, the fault characteristics of the power frequency zero-sequence signal are independently calculated, clarifying the spatial distribution law of the power frequency component of the zero-sequence signal, and eliminating the influence of harmonics generated by thyristor operation on the line selection results. For the power frequency zero-sequence signal, the series damping resistor of the arc suppression coil increases the active component in the grounding current, causing the phasor of the zero-sequence current of the faulty feeder to move closer to the negative real axis. After a grounding fault occurs, the thyristor operation disconnects the damping resistor, reducing the active component of the zero-sequence current of the faulty feeder and causing it to move closer to the imaginary axis. This method utilizes the maximum change in active power component of the faulty feeder before and after the damping resistor is switched on to accurately identify ground fault lines. The selected characteristic signal is clear, the measurement process is simple and accurate, the threshold setting is simple and reliable, and it is applicable to overhead lines and cable lines of different lengths. Furthermore, this method has strong resistance to transition resistance and is unaffected by ground parameter imbalance and transformer transmission errors. In practical applications, it can effectively utilize the damping resistor of the pre-adjusted arc suppression coil, which has a large adjustable capacity. No additional active grounding device is required, and the calculation and operation process is convenient and quick, greatly reducing the difficulty of engineering applications.

[0163] The following example verifies the fault detection method for this resonant grounding system.

[0164] In a resonant grounding system, ground faults are introduced via different lines and with different transition resistances. By performing a crucial operation after a ground fault occurs—removing the damping resistor—fault line selection in the resonant grounding system can be achieved. This is based on measuring the neutral point zero-sequence voltage and the zero-sequence current of each feeder before and after the damping resistor is removed, and calculating the change in power frequency active power before and after the damping resistor is removed. The power frequency active power change caused by this operation shows a significant difference between the faulty and non-faulty lines: the power change amplitude is much larger on the faulty line. Feeder L3 experiences a 100Ω ground fault in 0.1s, and the damping resistor is removed in 0.2s. The amplitudes of the zero-sequence current and neutral point zero-sequence voltage of each feeder are as follows: Figure 9 As shown in (a), the phase angle difference between the zero-sequence current of each feeder and the zero-sequence current at the neutral point is as follows: Figure 9 As shown in (b) of the diagram.

[0165] observe Figure 9As shown in (a), before the ground fault, the zero-sequence voltage amplitude is relatively small due to the suppression effect of the damping resistor. After the ground fault occurs at 0.1s, the system zero-sequence voltage suddenly increases by 2.94kV, and the zero-sequence current of each feeder also increases accordingly. For normal feeders, since the ground parameters remain unchanged, the zero-sequence current amplitude increases proportionally to the system ground parameters; the zero-sequence current of the faulted feeder is the opposite of the sum of the zero-sequence current of the non-faulted feeder and the neutral point current, and the increase in the zero-sequence current amplitude is much greater than that of the non-faulted feeder. After the damping resistor is removed at 0.2s, due to the loss of the damping resistor's suppression effect, the system resonates and amplifies the system zero-sequence voltage, leading to a sudden increase in the zero-sequence voltage. The zero-sequence current of the normal feeder increases due to the increase in the zero-sequence voltage, while the zero-sequence current of the faulted feeder decreases due to the loss of the resistive current portion provided by the damping resistor. Observation Figure 9 As shown in (b), for a normal feeder, since the line-to-ground parameters remain unchanged, the phase difference between the zero-sequence current and the zero-sequence voltage remains within 86°~90° before and after the damping resistor operates. For a faulty feeder, due to the loss of the resistive component provided by the damping resistor, the phase difference between the zero-sequence current and the zero-sequence voltage changes from 164.7° to 141.3°, gradually approaching the imaginary axis. Before and after the damping resistor is removed, the change in the power frequency active power of the faulty feeder is much greater than that of the healthy feeder. This fault characteristic can be used to accurately identify feeders with ground faults. Table 2 shows the difference in power frequency active power of each feeder before and after the damping resistor is removed and the results of fault feeder identification under different ground fault conditions.

[0166] As shown in Table 2, the simulation results indicate that the change in active power at power frequency of the faulty feeder before and after the damping resistor is removed is significantly greater than that of the healthy feeder. Furthermore, the change decreases with increasing transition resistance value, allowing for accurate identification of the faulty feeder even under a 10kΩ high-resistance grounding fault. When feeder L3 experiences a 10kΩ fault, the difference in active power at power frequency for the faulty feeder reaches 4.31kW, while the maximum difference for the non-faulty feeder is 0.84kW. Based on these criteria, the faulty feeder can be accurately identified.

[0167] Table 2. Fault Location Judgment Results for Power Frequency Active Power Difference

[0168]

[0169] As shown in Table 2, the simulation results demonstrate that, for different transition resistance scenarios, the faulty feeder was accurately selected within the set error range by utilizing the characteristic of the largest change in the power frequency active power of the faulty feeder before and after the damping resistor was removed. With the increase of the transition resistance, the difference in power frequency active power among the feeders all showed a decreasing trend, effectively distinguishing between faulty and non-faulty feeders even in high-resistance grounding faults. These results fully verify the accuracy, reliability, and engineering applicability of the fault detection method for this resonant grounding system in identifying faulty feeders under high-resistance grounding fault conditions.

[0170] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0171] Based on the same inventive concept, this application also provides a fault detection device for a resonant grounding system to implement the fault detection method for the resonant grounding system described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more embodiments of the resonant grounding system fault detection device provided below can be found in the limitations of the resonant grounding system fault detection method described above, and will not be repeated here.

[0172] In one exemplary embodiment, such as Figure 10 As shown, a fault detection device for a resonant grounding system is provided, comprising: a first acquisition module 1010, a second acquisition module 1020, a first determination module 1030, and a fault determination module 1040, wherein: the first acquisition module 1010 is used to acquire the current neutral point zero-sequence voltage of the resonant grounding system; the second acquisition module 1020 is used to cut off the damping resistor of the resonant grounding system when a fault is determined to have occurred in the resonant grounding system based on the current neutral point zero-sequence voltage and a zero-sequence voltage initiation threshold; and to acquire the first neutral point voltage of the resonant grounding system before the damping resistor is cut off. The system includes a zero-sequence voltage at the neutral point and the first zero-sequence current of each feeder in the resonant grounding system, as well as the second zero-sequence voltage at the neutral point and the second zero-sequence current of each feeder after the damping resistor is cut off; a first determining module 1030 is used to determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off, based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder; a fault determining module 1040 is used to determine the faulty feeder in each feeder based on the change in power frequency zero-sequence active power and the power change threshold.

[0173] In one embodiment, the second acquisition module 1020 includes: a first determining unit, configured to determine an adaptive detection threshold based on basic parameters; wherein the basic parameters include system parameters of the resonant grounding system and the expected value of its ability to withstand transition resistance; the system parameters of the resonant grounding system include the power frequency detuning rate, power frequency damping rate, three-phase asymmetry, and total capacitance to ground of the resonant grounding system before the damping resistor is cut off; the first acquisition unit, configured to acquire the effective value of the neutral point zero-sequence voltage during normal operation of the resonant grounding system; the second determining unit, configured to determine a zero-sequence voltage initiation threshold based on the effective value of the neutral point zero-sequence voltage and the adaptive detection threshold; and a fault determining unit, configured to determine that a fault has occurred in the resonant grounding system when the current neutral point zero-sequence voltage is greater than the zero-sequence voltage initiation threshold.

[0174] In one embodiment, the first determining unit is specifically used to: determine a first range of values ​​for the adaptive detection threshold based on system parameters; correct the lower limit of the first range of values ​​based on a reliability coefficient to obtain a second range of values; and, using the second range of values ​​as a constraint, solve an objective function based on the expected value of the transition resistance capability to obtain the adaptive detection threshold; wherein the objective function is used to describe the relationship between the expected value of the transition resistance capability and the adaptive detection threshold.

[0175] In one embodiment, the first determining module 1030 includes: a third determining unit, configured to determine first characteristic information based on a first neutral point zero-sequence voltage and each first zero-sequence current; wherein the first characteristic information includes a first power frequency zero-sequence voltage amplitude coefficient, a first power frequency zero-sequence voltage phase angle coefficient, a first power frequency zero-sequence current amplitude coefficient and a first power frequency zero-sequence current phase angle coefficient for each feeder; a fourth determining unit, configured to determine second characteristic information based on a second neutral point zero-sequence voltage and each second zero-sequence current; wherein the second characteristic information includes a second power frequency zero-sequence voltage amplitude coefficient, a second power frequency zero-sequence voltage phase angle coefficient, a second power frequency zero-sequence current amplitude coefficient and a second power frequency zero-sequence current phase angle coefficient for each feeder; and a fifth determining unit, configured to determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off based on the first characteristic information and the second characteristic information.

[0176] In one embodiment, the fifth determining unit includes: a first determining subunit, configured to determine, for each feeder, the first power frequency zero-sequence active power before the damping resistor is cut off, based on the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, and the first power frequency zero-sequence current amplitude coefficient and the first power frequency zero-sequence current phase angle coefficient of the feeder; a second determining subunit, configured to determine the second power frequency zero-sequence active power of the feeder after the damping resistor is cut off, based on the second power frequency zero-sequence voltage amplitude coefficient, the second power frequency zero-sequence voltage phase angle coefficient, and the second power frequency zero-sequence current amplitude coefficient and the second power frequency zero-sequence current phase angle coefficient of the feeder; and a third determining subunit, configured to determine the change in power frequency zero-sequence active power of the feeder before and after the damping resistor is cut off, based on the first power frequency zero-sequence active power and the second power frequency zero-sequence active power corresponding to the feeder.

[0177] In one embodiment, the first determining subunit is specifically used to: determine the phase angle difference based on the phase angle coefficient of the first power frequency zero-sequence voltage and the phase angle coefficient of the first power frequency zero-sequence current of the feeder; and determine the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off based on the phase angle difference, the amplitude coefficient of the first power frequency zero-sequence current of the feeder, and the amplitude coefficient of the first power frequency zero-sequence voltage.

[0178] Each module in the fault detection device of the aforementioned resonant grounding system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0179] In one exemplary embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 11 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores the current neutral-point zero-sequence voltage of the resonant grounding system. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a fault detection method for a resonant grounding system.

[0180] Those skilled in the art will understand that Figure 11 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0181] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the various method embodiments of the fault detection method for the resonant grounding system described above.

[0182] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the various method embodiments for fault detection of the resonant grounding system described above.

[0183] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the various method embodiments for fault detection of the resonant grounding system described above.

[0184] It should be noted that the data involved in this application (including but not limited to the current neutral point zero-sequence voltage of the resonant grounding system) are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0185] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0186] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0187] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A fault detection method for a resonant grounding system, characterized in that, The method includes: Obtain the current neutral point zero-sequence voltage of the resonant grounding system; If a fault is determined in the resonant grounding system based on the current neutral point zero-sequence voltage and the zero-sequence voltage activation threshold, the damping resistor of the resonant grounding system is switched off; and, Obtain the first neutral point zero-sequence voltage of the resonant grounding system and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is cut off, and the second neutral point zero-sequence voltage and the second zero-sequence current of each feeder in the resonant grounding system after the damping resistor is cut off. Based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder, determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off. Based on the change in zero-sequence active power and the power change threshold of each feeder, the faulty feeder in each feeder is determined.

2. The method according to claim 1, characterized in that, Based on the current neutral point zero-sequence voltage and the zero-sequence voltage initiation threshold, a fault is determined in the resonant grounding system, including: An adaptive detection threshold is determined based on the basic parameters; wherein, the basic parameters include the system parameters of the resonant grounding system and the expected value of its ability to withstand transition resistance; Obtain the effective value of the neutral point zero-sequence voltage during normal operation of the resonant grounding system; The zero-sequence voltage activation threshold is determined based on the effective value of the neutral point zero-sequence voltage and the adaptive detection threshold. If the current neutral point zero-sequence voltage is greater than the zero-sequence voltage activation threshold, it is determined that the resonant grounding system has failed.

3. The method according to claim 2, characterized in that, The system parameters of the resonant grounding system include the power frequency detuning rate, power frequency damping rate, three-phase asymmetry, and total capacitance to ground of the resonant grounding system before the damping resistor is cut off. The step of determining the adaptive detection threshold based on basic parameters includes: Based on the system parameters, determine the first range of values ​​for the adaptive detection threshold; Based on the reliability coefficient, the lower limit of the first value range is adjusted to obtain the second value range; Using the second value range as a constraint, the objective function is solved based on the expected value of the transition resistance capability to obtain the adaptive detection threshold; wherein, the objective function is used to describe the relationship between the expected value of the transition resistance capability and the adaptive detection threshold.

4. The method according to claim 1, characterized in that, The step of determining the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off, based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first and second zero-sequence currents of each feeder, includes: Based on the first neutral point zero-sequence voltage and each of the first zero-sequence currents, first characteristic information is determined; wherein, the first characteristic information includes the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, the first power frequency zero-sequence current amplitude coefficient and the first power frequency zero-sequence current phase angle coefficient of each feeder; The second characteristic information is determined based on the second neutral point zero-sequence voltage and each of the second zero-sequence currents; wherein, the second characteristic information includes the second power frequency zero-sequence voltage amplitude coefficient, the second power frequency zero-sequence voltage phase angle coefficient, the second power frequency zero-sequence current amplitude coefficient and the second power frequency zero-sequence current phase angle coefficient of each feeder; Based on the first feature information and the second feature information, the change in zero-sequence active power at power frequency for each feeder before and after the damping resistor is cut off is determined.

5. The method according to claim 4, characterized in that, The step of determining the change in zero-sequence active power at power frequency for each feeder before and after the damping resistor is cut off, based on the first feature information and the second feature information, includes: For each feeder, the first power frequency zero-sequence active power before the damping resistor of the feeder is cut off is determined based on the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, the first power frequency zero-sequence current amplitude coefficient and the first power frequency zero-sequence current phase angle coefficient of the feeder. The second power frequency zero-sequence active power of the feeder after the damping resistor is cut off is determined based on the second power frequency zero-sequence voltage amplitude coefficient, the second power frequency zero-sequence voltage phase angle coefficient, the second power frequency zero-sequence current amplitude coefficient, and the second power frequency zero-sequence current phase angle coefficient of the feeder. Based on the first power frequency zero-sequence active power and the second power frequency zero-sequence active power corresponding to the feeder, determine the change in power frequency zero-sequence active power of the feeder before and after the damping resistor is cut off.

6. The method according to claim 5, characterized in that, The step of determining the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off, based on the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence voltage phase angle coefficient, and the first power frequency zero-sequence current amplitude coefficient and the first power frequency zero-sequence current phase angle coefficient of the feeder, includes: The phase angle difference is determined based on the first power frequency zero-sequence voltage phase angle coefficient and the first power frequency zero-sequence current phase angle coefficient of the feeder; Based on the phase angle difference, the first power frequency zero-sequence current amplitude coefficient of the feeder, and the first power frequency zero-sequence voltage amplitude coefficient, the first power frequency zero-sequence active power of the feeder before the damping resistor is cut off is determined.

7. A fault detection device for a resonant grounding system, characterized in that, The device includes: The first acquisition module is used to acquire the current neutral point zero-sequence voltage of the resonant grounding system; The second acquisition module is used to cut off the damping resistor of the resonant grounding system when a fault is determined to have occurred in the resonant grounding system based on the current neutral point zero-sequence voltage and the zero-sequence voltage start-up threshold; and to acquire the first neutral point zero-sequence voltage of the resonant grounding system and the first zero-sequence current of each feeder in the resonant grounding system before the damping resistor is cut off, and the second neutral point zero-sequence voltage of the resonant grounding system and the second zero-sequence current of each feeder after the damping resistor is cut off. The first determining module is used to determine the change in power frequency zero-sequence active power of each feeder before and after the damping resistor is cut off, based on the first neutral point zero-sequence voltage, the second neutral point zero-sequence voltage, and the first zero-sequence current and the second zero-sequence current of each feeder. The fault determination module is used to determine the faulty feeder in each feeder based on the change in zero-sequence active power at each power frequency and the power change threshold.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

Images