High-resistance and arc grounding fault diagnosis method and system based on edge calculation

Abstract

According to the edge calculation-based high-resistance arc grounding fault diagnosis method and system, when the sum of zero-sequence current variations calculated by edge calculation equipment in each feeder terminal unit is greater than zero, but main protection of each branch does not act, and the three-phase current unbalance degree of the branch calculated by each edge calculation equipment is greater than a set threshold value, the main protection of the branch does not act; if the current instantaneous value change direction of any phase of the branch is different from the current instantaneous value change directions of the other two phases of the branch, judging that the branch has a high-resistance grounding fault; when the accumulated value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than a set time threshold value, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the temperature rise of the small resistor in the accumulated value of the intermittent arc grounding fault time is not less than a set temperature rise threshold value, the feeder terminal unit sends the arc grounding fault alarm to the main control system. And the equipment terminal unit sends a small resistor overheating alarm to the main control system. The method provided by the invention is a beneficial supplement for relay protection of the small resistor grounding system.

Description

Technical Field

[0001] The present invention relates to the field of new-type power distribution network distributed grounding fault diagnosis and positioning technology, and in particular to a high-resistance, arc grounding fault diagnosis method and system based on edge computing. Background Art

[0002] The distribution system has a complex network structure, various neutral point grounding methods, and a high probability of feeder failure, among which single-phase grounding faults account for the largest proportion. Under different neutral point grounding methods, the distribution network has different detection requirements and processing methods for single-phase grounding faults.

[0003] In the prior art, the neutral point effective grounding distribution network is mainly based on the grounding method through a small resistance. When a single-phase grounding fault with a relatively low resistance occurs, the fault current amplitude is relatively large. At present, zero-sequence current protection is mainly used for rapid fault detection and tripping isolation, and the positive rate is relatively high; while for the neutral point non-effective grounding distribution network, it is mainly based on ungrounding and grounding through arc suppression coils. When a single-phase grounding fault occurs, no obvious power frequency fault current loop is formed. At this time, the steady-state fault current amplitude is small, and the line voltage remains unchanged after the fault, which will not affect the normal power supply on the user side. Therefore, the fault line selection technology is mainly used to identify the fault feeder. The previous operating regulations stipulate that when the grounding current is less than 10A, it can continue to operate with the fault for 2 hours. In recent years, with the extensive use of fault line selection tripping technology based on traveling waves and transient quantities, the positive rate of fault line selection has been significantly improved, especially for metallic or low transition resistance faults, the positive rate can reach more than 90%. The main reason for the occurrence of serious accidents such as electric shock casualties, forest fires, etc. caused by single-phase grounding faults in feeders is that the fault branch is in a high-resistance state, and most of them are also accompanied by the nonlinearity of arc grounding. Therefore, the difficulty of single-phase grounding fault detection is mainly concentrated on arc high-resistance faults. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a high-resistance and arc grounding fault diagnosis method and system based on edge computing, which utilizes a transient analysis method based on sudden changes in current imbalance to effectively identify high-resistance grounding; and adopts an intermittent arc grounding fault accumulation detection method to effectively solve the problem that under intermittent arc grounding faults, the traditional zero-sequence overcurrent protection cannot cut off the fault branch because the single grounding time does not reach the entire group action time limit.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a high-resistance, arc grounding fault diagnosis method based on edge computing. The distribution network includes multiple branches, each branch is equipped with a feeder terminal unit, including: Each feeder terminal unit is configured with an edge computing device; the edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch where it is located is greater than the set threshold, and the direction of change of the instantaneous value of the current of any phase in the branch is different from the direction of change of the instantaneous value of the current of the other two phases, the edge computing device determines that a high-resistance grounding fault occurs in the branch where it is located, and the branch where the edge computing device is located is a high-resistance grounding fault branch, and the phases with different directions of change of the instantaneous value of the current are determined to be high-resistance grounding fault phases; When the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch where it is located, the feeder terminal unit starts intermittent arc grounding fault time detection, and the equipment terminal unit configured on the small resistance side starts small resistance temperature rise detection; when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistance temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the equipment terminal unit sends a small resistance overheating alarm to the main control system.

[0007] Preferably, the main protection of the branch includes: longitudinal distance protection and zero-sequence directional protection.

[0008] Preferably, the unbalance degree of the instantaneous value variation of the three-phase current satisfies the following relationship: , In the formula, , are the maximum and minimum values ​​of the instantaneous changes of the three-phase currents, is the average value of the instantaneous value change of the three-phase current; Set the threshold value to be no less than 2.

[0009] Preferably, the cumulative value of the intermittent arc grounding fault time satisfies the following relationship: , In the formula, It is the cumulative value of intermittent arc grounding fault time; is the duration of a single arc grounding fault; The number of intermittent arc grounding faults when the cumulative value of intermittent arc grounding fault time exceeds the limit.

[0010] Preferably, the whole set action time of zero-sequence overcurrent protection is To set the time threshold and set the reliability coefficient , Greater than 1, when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit meets When the relay protection is activated, it disconnects the branch where the high-resistance grounding fault occurs.

[0011] Preferably, according to the provisions of the standard of the neutral point grounding resistance, the allowable temperature rise value of the small resistance within the rated time is determined as the set temperature rise threshold.

[0012] Preferably, the feeder terminal unit synchronously sends the cumulative value of the detected intermittent arc grounding fault time to the equipment terminal unit, and the equipment terminal unit decides whether to send a small resistor overheat alarm to the main control system based on the comparison between the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time and the set temperature rise threshold; when the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time is not less than the set temperature rise threshold, the equipment terminal unit sends a small resistor overheat alarm to the main control system, and the relay protection is activated to disconnect the branch where the high-resistance grounding fault occurs.

[0013] The present invention also proposes a high-resistance, arc grounding fault diagnosis system based on edge computing. The distribution network includes multiple branches, each branch is equipped with a feeder terminal unit, including: A high-resistance grounding fault diagnosis module is used to configure an edge computing device for each feeder terminal unit; the edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch where it is located is greater than the set threshold, and the direction of the instantaneous value change of the current of any phase in the branch is different from the direction of the instantaneous value change of the current of the other two phases, the edge computing device determines that a high-resistance grounding fault occurs in the branch where it is located, and the branch where the edge computing device is located is a high-resistance grounding fault branch, and the phases with different directions of change of the instantaneous value of the current are determined to be high-resistance grounding fault phases; The arc grounding fault diagnosis module is used to start the intermittent arc grounding fault time detection of the feeder terminal unit when the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch where it is located, and the device terminal unit configured on the small resistance side starts the small resistance temperature rise detection; when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistance temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the device terminal unit sends a small resistance overheating alarm to the main control system.

[0014] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0015] A computer-readable storage medium stores a computer program, which implements the steps of the method when executed by a processor.

[0016] The beneficial effects of the present invention are that, compared with the prior art, at least the present invention diagnoses high-resistance and arc grounding faults under the access of distributed power sources to the distribution network based on edge computing, and realizes distributed grounding fault diagnosis and positioning, which not only improves the accuracy of grounding fault positioning, but also improves the operating speed of fault isolation and recovery, and provides strong support for distribution network fault self-healing technology under new power systems.

[0017] The present invention aims at the problem that the zero-sequence overcurrent protection of the ground fault of the distribution network under the low-resistance grounding mode of the neutral point has blind spots and protection refusal to operate under high-resistance and intermittent arc grounding faults, and proposes a new transient analysis method based on the sudden change of current imbalance, so as to effectively identify high-resistance grounding; at the same time, the cumulative time detection method of intermittent arc grounding faults and the temperature rise detection method within the cumulative time of the lower resistance are adopted, which can effectively solve the problem that under intermittent arc grounding faults, the traditional zero-sequence overcurrent protection cannot cut off the fault branch because the single grounding time does not reach the whole group action time limit, and the small resistance is burned due to the thermal accumulation effect caused by this. The above protection strategy is effective after simulation verification and can be used as a beneficial supplement to the relay protection of the original low-resistance grounding system. In summary, the new high-resistance grounding and intermittent arc grounding relay protection strategy provides an effective, important and safe protection supplement for the low-resistance system. The practical application of this relay protection strategy can also solve the protection blind spot problem in the low-resistance system, thereby effectively improving the safety and reliability of the operation of the entire low-resistance system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the high-resistance and arc grounding fault diagnosis method based on edge computing proposed in the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0020] The neutral point grounding methods of the distribution network system include resistance grounding, which includes large resistance grounding and small resistance grounding; the neutral point grounding method through large resistance is aimed at limiting the single-phase grounding current, and the resistance value is generally hundreds to thousands of ohms; the system with large resistance grounding can eliminate most of the resonant overvoltage and has a certain limiting effect on the single-phase intermittent arc grounding overvoltage. The single-phase grounding fault current is less than 10A, and the system can continue to operate without interrupting the power supply under the grounding fault condition, but the system equipment insulation requirements are high and the investment is large. For the 6-35kV power transmission and distribution network mainly composed of cables, when the single-phase grounding fault capacitive current is large, the neutral point grounding method through small resistance is adopted, and the resistance value is generally 10-20Ω, and the single-phase grounding fault current is 100-1000A. The fault line can be quickly cut off, and the overvoltage level is low. This grounding method is mainly used for urban distribution networks, power plant power systems, and industrial and mining enterprise distribution systems where cable lines are the main ones, instantaneous single-phase grounding faults are not easy to occur, and the system capacitive current is relatively large.

[0021] Arc high-resistance fault (HIF), the fault branch presents a high-resistance state, and most of them are also accompanied by the nonlinearity of arc grounding. Therefore, the current difficulty of single-phase grounding fault detection is mainly concentrated on the sensitive detection and identification of arc high-resistance fault. For the detection of HIF, whether from the perspective of zero-sequence current protection or fault line selection, the main difficulties are: the amplitude of low-frequency components such as power frequency and harmonics is low during the fault, and the fault characteristics are not obvious; the amplitude of high-frequency electrical quantities such as traveling waves and transients is also low, and they are easily disturbed by disturbances such as noise and arc distortion; in particular, the volatility of related fault characteristic quantities is large, and the threshold is difficult to adjust. This problem is essentially a game problem between reliability and sensitivity. Lowering the action threshold can improve the sensitivity of fault detection, but it will lose a certain degree of reliability; vice versa. In response to the above problems, a series of related fault detection methods have been proposed from different angles. Based on the arc distortion characteristics of HIF, the concave-convex method, volt-ampere characteristic method, harmonic method, etc. are proposed from the perspective of time and frequency domain, but they rely heavily on the accurate modeling of arc distortion characteristics; based on transient and steady-state circuit analysis, active power method, ratio braking method, transient energy method, projection coefficient method, etc. are proposed, but the arc characteristics are not considered in the analysis process; based on the traveling wave method of fault instantaneous mutation, there are certain challenges in accurately identifying the initial wave head; there are also artificial neural networks, expert systems, genetic algorithms and other artificial intelligence methods, but the physical meaning of such methods is unclear and the interpretability is poor. Overall, various detection methods have certain limitations and need to be further sorted out and analyzed.

[0022] The present invention proposes a high-resistance and arc grounding fault diagnosis method based on edge computing. The neutral point of the distribution network is grounded through a small resistor, and a device terminal unit is configured on the small resistor side. Each branch of the distribution station is equipped with a feeder terminal unit, such as Figure 1 As shown, including: Step 1, each feeder terminal unit is configured with an edge computing device; the edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch is greater than the set threshold, and the direction of the instantaneous value change of the current of any phase in the branch is different from the direction of the instantaneous value change of the current of the other two phases, the edge computing device determines that the branch is a high-resistance grounding branch, and determines that the phase with a different direction of the instantaneous value change of the current is a high-resistance grounding fault phase.

[0023] The distribution network includes multiple branches, each of which is equipped with a feeder terminal unit, and each feeder terminal unit is equipped with an edge computing device. When judging and locating grounding faults in the distribution network, data is processed by edge computing devices to reduce delays and improve real-time response capabilities, so that data can be quickly analyzed at the moment of the fault, and timely measures can be taken, which is crucial for the reliability and stability of the power system. In addition, combined with the layout of the feeder terminal unit, the edge computing device can be deployed close to the data source. The deployment location of the edge computing device includes but is not limited to: the intelligent circuit breaker side, the current transformer side, and the voltage sensor side, so that various operating parameters of the distribution network, including current, voltage and other information, are collected in real time. Before the data is transmitted to the central control system, the edge computing device can pre-process the data, including filtering, noise reduction, etc., thereby reducing the transmission bandwidth requirements and speeding up the subsequent analysis.

[0024] When a high-resistance grounding fault occurs, due to the weak fault current, the main protection based on longitudinal distance protection and zero-sequence direction protection will have a dead zone and cannot be quickly activated when a fault occurs. Therefore, the high-resistance grounding fault diagnosis method proposed in the present invention is essentially different from the relay protection in principle. First, when the grounding current is not greater than the zero-sequence protection action value, the diagnosis of the high-resistance grounding fault is started according to the relative change of the global zero-sequence current. At this time, the relay protection device cannot quickly calculate and judge the relative change of the global zero-sequence current. The computing performance of the edge computing device can fully meet the above requirements. Therefore, the present invention proposes that when the sum of the zero-sequence current changes calculated by all feeder terminal units is greater than zero but the zero-sequence protection of each branch is not activated, each feeder terminal unit starts the high-resistance grounding fault diagnosis program, that is, starts to calculate the three-phase current imbalance of the branch; and the close device layout characteristics of the edge computing device assist in the positioning of the high-resistance grounding branch, thereby improving the positioning accuracy and reliability.

[0025] When the currents in each branch are in a high-resistance grounding fault, the branch transient current phase asymmetry detection method is used to identify the high-resistance grounding fault.

[0026] In the embodiment, in a neutral point grounding system with a small resistance, when the branch After a single-phase grounding fault occurs, the fault branch The phase current and grounding point current satisfy the following relationship: , In the formula, , , Fault branch The three-phase current; is the grounding point current; , , Fault branch The three-phase load current; , , Fault branch The three-phase capacitive current to ground; It is the neutral point grounding small resistance current; , , They are the sum of the three-phase to ground capacitance currents of all branches.

[0027] Non-fault branch The currents of each phase satisfy the following relationship: , In the formula, , , Non-fault branches The three-phase current; , , Non-fault branches The three-phase load current; , , Non-fault branches The three-phase capacitive current to ground.

[0028] It can be seen from the calculation formula of each phase current of the fault branch and the non-fault branch that when a ground fault occurs, the changes in the three-phase current of the non-fault branch and the non-fault phase current of the fault branch are mainly caused by the change in the phase of the ground capacitance current; and the fault phase current of the fault branch has the largest change due to the influence of the fault point current. The above characteristics show that it is only necessary to judge whether the three-phase current of each branch has a sudden change in balance, and the branch with the largest sudden change in imbalance is the grounded fault branch. In addition, even if high-resistance grounding occurs, the current mutation is still large for the grounded branch and the grounded phase of the grounded branch; and a certain transient process will be generated at the moment of grounding, and the current change of this process is more obvious. Therefore, the three-phase current imbalance can not only be used as a criterion to detect single-phase grounding faults, but also can identify high-resistance grounding faults when the fault current is weak, especially the imbalance of the instantaneous value change of the three-phase current at the moment of grounding fault, to identify the high-resistance grounding fault branch and the fault phase on the high-resistance grounding fault branch.

[0029] The unbalance degree of the instantaneous value change of the three-phase current satisfies the following relationship: , In the formula, , are the maximum and minimum values ​​of the instantaneous changes of the three-phase currents, is the average value of the instantaneous value change of the three-phase current; When a single-phase ground fault occurs somewhere in the power system, the balance state of the instantaneous value change of the three-phase current will be broken, that is, the current of the faulty phase will increase significantly, while the currents of the other two phases will be relatively small or unchanged. In this case, it is possible to determine whether a high-resistance ground fault has occurred by measuring the instantaneous value change of the three-phase current and calculating its imbalance. If the imbalance of the instantaneous value change of the three-phase current exceeds the set threshold, it is considered that a high-resistance ground fault may have occurred in the system, and the phase with a different direction of change of the instantaneous value of the current is determined to be the fault phase. In the embodiment, the threshold value is set to be not less than 2.

[0030] The present invention proposes a method of using current unbalance mutation to identify high-resistance grounding faults. It no longer focuses on the absolute amplitude of the operating current, but detects the relative unbalance changes of the currents of each branch, so that the grounding fault branch and the fault phase can be accurately identified. After starting with a small resistance current mutation and identifying the grounding fault, if the steady-state fault current after the small resistance current mutation continues to exist, and the zero-sequence protection of the line cannot operate, it can be judged as high-resistance grounding. The grounding fault branch is tripped after a delay through the relative current unbalance mutation criterion to eliminate the fault.

[0031] In addition, the current imbalance method focuses on detecting the imbalance between the three-phase currents. When a single-phase grounding fault occurs, the current of the faulty phase will increase significantly, resulting in an unbalanced overall current distribution. Conventional methods such as zero-sequence current detection and negative-sequence current detection mainly focus on specific types of currents, such as the presence or absence of zero-sequence current. The current imbalance method usually only requires the use of ordinary current transformers to monitor the currents of each phase, and has low hardware requirements. Conventional methods may require additional sensors or special equipment to detect specific types of currents, such as zero-sequence current transformers. Moreover, the calculation of current imbalance proposed in the present invention is relatively simple, mainly involving basic mathematical operations; while conventional methods such as relay protection technology may involve more complex algorithms and logical judgments to ensure accurate identification of various types of faults.

[0032] Furthermore, in order to avoid the impact of the uncertainty of the output of distributed power sources connected to the distribution network, the edge computing device also performs high-pass filtering on the instantaneous value changes of the three-phase current in the branch where it is located, and extracts the effective three-phase current high-frequency transient change signal through high-frequency filtering with a set cutoff frequency.

[0033] Step 2. When the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch where it is located, the feeder terminal unit starts intermittent arc grounding fault time detection, and the device terminal unit configured on the small resistance side starts small resistance temperature rise detection; when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistance temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the device terminal unit sends a small resistance overheating alarm to the main control system.

[0034] When a high-resistance grounding fault occurs, an intermittent arc grounding fault may occur in the fault branch. Due to multiple instantaneous start-up and recovery, the grounding fault is intermittent and reciprocating, making it impossible for the zero-sequence protection to act in time, and also causing the problem of heat accumulation and burning of the small resistance system. Therefore, the arc grounding fault diagnosis method proposed in the present invention not only sends an arc grounding fault alarm according to the time accumulation strategy of the intermittent arc grounding fault, but also sends a small resistance overheating alarm according to the small resistance body heat accumulation strategy, thereby realizing the auxiliary relay protection system to perform intermittent arc grounding fault protection as soon as possible.

[0035] In the existing relay protection strategy, when intermittent arc grounding occurs, the time of each arc grounding is short and the interval is close, which cannot reach the action time of the entire group of zero-sequence current overcurrent protection, thus causing the protection to fail to operate. Therefore, for the short time of a single arc grounding, when intermittent arc grounding exists for a long time, a fault accumulation strategy can be adopted as the protection criterion for intermittent arc grounding. In the embodiment, the feeder terminal unit on the high-resistance grounding fault branch uses the action criterion and time setting value consistent with the intermittent arc grounding protection, so as to avoid affecting the correctness of the relay protection action, wherein the cumulative value of the intermittent arc grounding fault time satisfies the following relationship: , In the formula, It is the cumulative value of intermittent arc grounding fault time; is the duration of a single arc grounding fault; The number of intermittent arc grounding faults when the cumulative value of intermittent arc grounding fault time exceeds the limit.

[0036] The whole set action time of zero sequence overcurrent protection To set the time threshold and set the reliability coefficient , Greater than 1, when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit meets When the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system. The alarm signal corresponds to the branch where the high-resistance grounding fault occurs. Therefore, the feeder terminal unit sends an arc grounding fault alarm to the main control system to assist in fault line selection, ensure the correctness of the protection action, and improve the reliability of distribution network operation.

[0037] Moreover, according to the provisions of the standard of the neutral point grounding resistance, the allowable temperature rise value of the small resistor within the rated time is determined as the set temperature rise threshold. In the embodiment, the rated time and allowable temperature rise value of the neutral point grounding resistance in the IEEE-32 standard are shown in Table 1: Table 1 Rated time and allowable temperature rise of neutral point grounding resistance in IEEE-32 standard The feeder terminal unit synchronously sends the cumulative value of the detected intermittent arc grounding fault time to the equipment terminal unit, and the equipment terminal unit decides whether to send a small resistor overheat alarm to the main control system based on the comparison between the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time and the set temperature rise threshold; when the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time is not less than the set temperature rise threshold, the equipment terminal unit sends a small resistor overheat alarm to the main control system, and the relay protection is activated to disconnect the branch where the high-resistance grounding fault occurs, thereby protecting the small resistor from damage. Therefore, the small resistor overheat alarm proposed by the present invention is a supplementary signal of the arc grounding fault alarm that meets the protection requirements of the small resistor body, and because the small resistor overheat alarm here is obtained by judging the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time, it is different from the principle of conventional small resistor overheat protection.

[0038] The present invention also proposes a high-resistance, arc grounding fault diagnosis system based on edge computing. The distribution network includes multiple branches, each branch is equipped with a feeder terminal unit, including: A high-resistance grounding fault diagnosis module is used to configure an edge computing device for each feeder terminal unit; the edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch where it is located is greater than the set threshold, and the direction of the instantaneous value change of the current of any phase in the branch is different from the direction of the instantaneous value change of the current of the other two phases, the edge computing device determines that a high-resistance grounding fault occurs in the branch where it is located, and the branch where the edge computing device is located is a high-resistance grounding fault branch, and the phases with different directions of change of the instantaneous value of the current are determined to be high-resistance grounding fault phases; The arc grounding fault diagnosis module is used to start the intermittent arc grounding fault time detection of the feeder terminal unit when the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch where it is located, and the device terminal unit configured on the small resistance side starts the small resistance temperature rise detection; when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistance temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the device terminal unit sends a small resistance overheating alarm to the main control system.

[0039] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0040] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the above. The computer-readable storage medium used herein is not to be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0041] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0042] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect through the Internet). In some embodiments, by using the state information of the computer-readable program instructions to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit may execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A high-resistance, arc-ground fault diagnosis method based on edge computing, wherein the distribution network includes multiple branches, each branch is equipped with a feeder terminal unit, characterized in that: include: Each feeder terminal unit is equipped with an edge computing device; The edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch where it is located is greater than the set threshold, and the direction of the instantaneous value change of the current of any phase in the branch is different from the direction of the instantaneous value change of the current of the other two phases, the edge computing device determines that a high-resistance grounding fault occurs in the branch where it is located, and the branch where the edge computing device is located is a high-resistance grounding fault branch, and the phases with different directions of change of the instantaneous value of the current are determined to be high-resistance grounding fault phases; When the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch, the feeder terminal unit starts intermittent arc grounding fault time detection, and the device terminal unit configured on the low-resistance side starts low-resistance temperature rise detection; When the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistor temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the equipment terminal unit sends a small resistor overheating alarm to the main control system.

2. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 1 is characterized in that: The main protection of the branch includes: longitudinal distance protection and zero-sequence directional protection.

3. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 1 is characterized in that: The unbalance degree of the instantaneous value change of the three-phase current satisfies the following relationship: ， In the formula, , are the maximum and minimum values ​​of the instantaneous changes of the three-phase currents, is the average value of the instantaneous value change of the three-phase current; Set the threshold value to be no less than 2.

4. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 1 is characterized in that: The cumulative value of intermittent arc grounding fault time satisfies the following relationship: ， In the formula, It is the cumulative value of intermittent arc grounding fault time; is the duration of a single arc grounding fault; The number of intermittent arc grounding faults when the cumulative value of intermittent arc grounding fault time exceeds the limit.

5. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 4 is characterized in that: The whole set action time of zero sequence overcurrent protection To set the time threshold and set the reliability coefficient , Greater than 1, when the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit meets When the high-resistance ground fault occurs, the relay protection will be activated to disconnect the branch.

6. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 4 is characterized in that: According to the provisions of the standard for neutral point grounding resistance, the allowable temperature rise value of the small resistor within the rated time is determined as the set temperature rise threshold.

7. The high-resistance and arc grounding fault diagnosis method based on edge computing according to claim 6 is characterized in that: The feeder terminal unit synchronously sends the cumulative value of the detected intermittent arc grounding fault time to the equipment terminal unit, and the equipment terminal unit decides whether to send a small resistor overheat alarm to the main control system based on the comparison between the small resistor temperature rise value within the cumulative value of the intermittent arc grounding fault time and the set temperature rise threshold; When the temperature rise of the small resistor is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the equipment terminal unit sends a small resistor overheat alarm to the main control system, and the relay protection is activated to disconnect the branch where the high-resistance grounding fault occurs.

8. A high-resistance, arc-ground fault diagnosis system based on edge computing, wherein the distribution network includes multiple branches, each branch is equipped with a feeder terminal unit, characterized in that: include: High-resistance ground fault diagnosis module, used for each feeder terminal unit to configure edge computing equipment; The edge computing device in each feeder terminal unit obtains the instantaneous value change of the three-phase current of the branch where it is located to calculate the zero-sequence current change of the branch; when the sum of all calculated zero-sequence current changes is greater than zero but the main protection of each branch is not activated, each edge computing device calculates the three-phase current imbalance of the branch where it is located. When the calculated three-phase current imbalance of the branch where it is located is greater than the set threshold, and the direction of the instantaneous value change of the current of any phase in the branch is different from the direction of the instantaneous value change of the current of the other two phases, the edge computing device determines that a high-resistance grounding fault occurs in the branch where it is located, and the branch where the edge computing device is located is a high-resistance grounding fault branch, and the phases with different directions of change of the instantaneous value of the current are determined to be high-resistance grounding fault phases; The arc grounding fault diagnosis module is used for the feeder terminal unit to start intermittent arc grounding fault time detection when the edge computing device of the feeder terminal unit determines that a high-resistance grounding fault occurs in the branch where the feeder terminal unit is located, and the device terminal unit configured on the small resistance side starts the small resistance temperature rise detection; When the cumulative value of the intermittent arc grounding fault time detected by the feeder terminal unit is not less than the set time threshold, the feeder terminal unit sends an arc grounding fault alarm to the main control system, or when the small resistor temperature rise is not less than the set temperature rise threshold within the cumulative value of the intermittent arc grounding fault time, the equipment terminal unit sends a small resistor overheating alarm to the main control system.

9. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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