A differential FA initiation method based on 5G communication

Abstract

A differential FA (Fault Actuator) starting method based on 5G communication belongs to the field of relay protection. 5G terminals are configured at each substation, and independent 5G self-healing terminals are configured at each busbar to achieve fault isolation and self-healing functions. When a system fault occurs, the distributed self-healing system based on 5G communication performs comprehensive judgment and decision-making according to a fixed strategy, and converts trip and close commands into specific circuit breaker opening and closing outputs to achieve system self-healing. The differential protection is only used as a fault location module and does not operate at the protection output. The self-healing system issues corresponding control commands based on the location results to isolate the switches on both sides of the fault. Fault location is achieved through differential protection, and the FA system sends switch trip commands based on the location results to achieve fault interval isolation. Based on distribution network FA technology and 5G communication technology, this method improves the speed of FA fault isolation while ensuring the selectivity of switch actions, avoiding cascading trips, and ensuring the accuracy of fault isolation.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection, and particularly relates to a differential FA starting method based on 5G communication for differential protection of distribution networks. Background Technology

[0002] During operation, power distribution networks inevitably experience faults due to equipment, external environmental factors, and other reasons. Power outages after faults occur reduce power supply reliability and impact user experience. Distribution automation aims to quickly locate faults in the distribution network with little or no human intervention, rapidly isolate faulty sections, and restore power to non-faulty areas. Feeder Automation (FA) is the key component of distribution automation.

[0003] With the large-scale access and application of distributed energy, power distribution networks are gradually evolving from radial topologies to closed-loop multi-source power supply topologies.

[0004] Differential protection algorithms, due to their simple principle, can achieve zero-second instantaneous interruption of faulty lines and are unaffected by voltage transformers, gradually demonstrating their advantages in handling distribution line faults. Using current differential protection with full-line high-speed operation in distribution networks can effectively solve the distribution network protection problems under the aforementioned distributed power source integration scenarios.

[0005] As distribution networks continue to develop, their structures become increasingly complex, load types proliferate, and system operation modes become more diverse. This leads to a continuous increase in fault handling time for centralized and localized power distribution networks (FAs), and their fault location and fault tolerance capabilities cannot meet the development needs of distribution networks. Unlike these two types, intelligent distributed FAs benefit from the support of low-latency, high-reliability communication systems, resulting in shorter fault location and isolation times, better accuracy, and stronger adaptability. They provide strong support for achieving self-healing of distribution network faults.

[0006] However, differential protection has high requirements for the horizontal communication medium, and most of them use optical fiber communication. However, the cost of laying optical fiber is high, and it is difficult to implement in old urban areas or old line renovation projects, thus limiting the development of differential protection in distribution networks.

[0007] Current power distribution network self-healing systems primarily employ communication methods such as power line carrier communication, fiber optic communication, and 4G wireless communication. However, for the future energy internet, existing power grid communication technologies struggle to meet the demands of a massive increase in business terminals, refined business management requirements, and new business characteristics such as millisecond-level response times, in terms of security, low latency, high reliability, large bandwidth, and cost-effectiveness.

[0008] Due to its ultra-low latency, high reliability, and multi-connectivity information transmission characteristics, 5G networks can more effectively achieve peer-to-peer communication between terminals, providing a transmission channel for differential protection applications. When a fault occurs in the distribution network, the 5G communication system makes it possible to automatically locate and isolate the fault at the millisecond level, thereby ensuring uninterrupted power supply to non-faulty areas and significantly improving emergency response efficiency.

[0009] With the development of 5G, wireless communication latency has been improved. The end-to-end latency of 5G communication is within 15ms. Based on 5G communication, differential FA can quickly isolate line faults according to differential protection algorithms, which belongs to the fast-acting intelligent distributed FA.

[0010] Researching differential self-healing systems based on 5G communication can provide new solutions and application scenarios for the future development of power distribution automation. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a differential FA start-up method based on 5G communication.

[0012] The technical solution of this invention is: to provide a differential FA start-up method based on 5G communication, characterized in that:

[0013] 1) While maintaining the existing protection devices and functions, the substation is equipped with 5G terminals, which have the ability to collect data from conventional outgoing protection devices and control their opening and closing, and to interact with data from each 5G self-healing terminal in the ring.

[0014] 2) Each switching station is equipped with an independent 5G self-healing terminal along the busbar to realize the functions of isolation and self-healing switch at the open loop point of the switching station;

[0015] 3) Each 5G self-healing terminal independently completes functions including self-healing system logic judgment and command decision-making;

[0016] 4) When a system fault occurs within the double-ring network connection range, the distributed self-healing system based on 5G communication makes a comprehensive judgment and decision according to a fixed strategy, and converts the trip and close commands into specific circuit breaker opening and closing outputs to realize the system self-healing function.

[0017] 5) When a line fault occurs, the protection and control device of the faulty line detects the fault and transmits multiple instantaneous phasor currents at the time of the fault to the adjacent protection and control device. The protection and control device adopts sampled value differential protection to quickly and accurately make differential protection judgments.

[0018] 6) When the operating current of multiple sampling points meets the differential protection judgment condition at the time of a line fault, it indicates that the fault occurred on the line, and the distribution terminals on both sides of the fault point can quickly locate the fault point.

[0019] 7) The differential protection is used only as a fault location module and does not operate at the protection output. The self-healing system issues corresponding control commands based on the location results to isolate the switches on both sides of the fault.

[0020] 8) Fault location is achieved through differential protection. The FA system sends a switch trip command based on the location result to achieve fault isolation function.

[0021] Specifically, the differential protection judgment conditions include: when the line is operating normally or a fault occurs outside the line, the current flowing through both sides of the line is equal; when a fault occurs inside the line, all components connected to the power supply provide current to the fault point.

[0022] The protection principle is based on the fact that the current flowing into a node or enclosed space is equal to the current flowing out of that node or enclosed space.

[0023] The only condition for a fault criterion to be valid is the existence of an additional branch current flowing out, regardless of the nature of the power source providing the current.

[0024] Furthermore, the external power source providing the current can be a three-phase symmetrical synchronous motor or asynchronous motor, or a distributed power source using a power electronic converter interface.

[0025] Specifically, after the substation self-healing terminal detects a fault, it implements the differential FA startup process based on 5G communication according to the following steps:

[0026] 1) Begin;

[0027] 2) In full-line circuit breaker mode, a fault was detected at the switch station terminal;

[0028] 3) Intelligent distributed FA startup;

[0029] 4) Information exchange between the switching station terminal and the 5G self-healing terminal;

[0030] 5) Determine whether a 5G self-healing terminal fault information is received after the T1 delay;

[0031] 6) If a 5G self-healing terminal fault information is received after a delay of T1, the action exit time will be extended to T2.

[0032] 7) If no 5G self-healing terminal fault information is received after the T1 delay, the action exit will be activated immediately.

[0033] 8) End.

[0034] Furthermore, the differential FA start-up method, in conjunction with parameters including 5G communication delay, 5G differential positioning time, and one-time switch action time, sets parameters T1 and T2 on-site.

[0035] Preferably, the preferred values ​​for the parameters T1 and T2 are as follows: T1 = 40ms, T2 = 300ms.

[0036] Specifically, the differential FA startup method performs correction processing when "out-of-order messages" occur, and the processing flow is as follows:

[0037] (1) When receiving wireless data, it is directly stored in the temporary data buffer in the order of reception;

[0038] (2) Take the received data points and locate the data according to the absolute time scale;

[0039] (3) Perform interpolation calculations for the corresponding data points and store them in the line protection calculation buffer;

[0040] (4) The differential protection calculation program writes data to the data buffer while reading data from the buffer to perform real-time calculation of the differential current. The read pointer lags behind the write pointer by a relatively fixed time.

[0041] (5) When a message is out of order, the write pointer will jump forward, and the jump step size is the same as the difference between the sent sequence number;

[0042] (6) When the missing frame number is received, the write pointer will turn back to fill it in, so that the data in the entire buffer is continuous again. At this time, the read pointer has not yet reached this point, and the protection program will not lock.

[0043] (7) If the missing frame is not delivered in time, the protection procedure will lock.

[0044] Furthermore, the differential FA startup method, when a "frame loss" occurs, handles the situation according to the following steps:

[0045] Setting: The data packet buffer sequence number is used as the description instance, sequence number 1 is the latest position, sequence number 2 is the position of the previous sampling point, and so on;

[0046] All sampled values ​​on this side are set to be valid. Serial number 1 is the index position of the current sampled value on this side, which is also the position corresponding to the latest sampled value on the last side. Serial number 2 is the last point of the Fourier calculation data window.

[0047] In 5G differential service, the validity of the sample value of sequence number 2 is used to determine whether the communication message is lost.

[0048] If the sampled value flag is 0, it indicates that the data is valid; if the sampled value flag is -1, it indicates that the data is invalid, and the system enters the interlocking protection mode.

[0049] Furthermore, when processing "message frame loss", frame loss is judged using sequence numbers 3, 2, and 1 as examples, and frame loss is calculated based on whether sequence number 2 is valid.

[0050] If a false frame loss occurs, i.e., sequence number 3 and 1 are valid, sequence number 2 is -1, but sequence numbers 3 and 1 are consecutive, no frame loss will be reported in this case, and invalid data will be corrected.

[0051] If frames are dropped a certain number of times consecutively, then a communication delay is set.

[0052] The differential FA start-up method described in this invention adopts an intelligent distributed information interaction mode. The 5G terminal of the substation communicates with the 5G self-healing terminal via 5G to exchange fault information. After the substation self-healing terminal detects a fault, it waits for a delay of T1. If it receives fault information from the self-healing terminal within T1, it extends the action exit time to T2. If it does not receive fault information from the self-healing terminal within T1, it immediately takes action to ensure the differential coordination between the substation and the primary switch station.

[0053] Compared with the prior art, the advantages of the present invention are:

[0054] 1. The technical solution of this invention takes the distributed self-healing system of distribution network based on 5G communication as the research object. Based on the distribution network FA technology and 5G communication technology, and combined with the typical 10kV double-ring network structure topology, a differential FA start-up technology based on 5G communication is proposed.

[0055] 2. Through engineering simulation testing, the startup logic proposed in this technical solution is verified. While improving the speed of FA fault isolation, it ensures the selectivity of switching action, avoids cascading tripping, and ensures the accuracy of fault isolation. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the wiring mode of a typical 10kV double-ring self-healing system.

[0057] Figure 2 This is a schematic diagram of a distributed self-healing system architecture for power distribution networks based on 5G communication.

[0058] Figure 3 This is a schematic diagram of a distributed self-healing system configuration based on 5G communication;

[0059] Figure 4 This is a schematic diagram of the differential principle;

[0060] Figure 5 It is a braking characteristic curve graph;

[0061] Figure 6 This is a schematic diagram of the FA startup process for 5G differential in this invention;

[0062] Figure 7 This is a schematic diagram of message out-of-order processing according to the present invention;

[0063] Figure 8 This is a diagram of a data packet buffer. Detailed Implementation

[0064] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0065] The distribution network plays a crucial role in the power system, connecting the transmission network and power users. With the increasingly pronounced bi-peak characteristics of electricity consumption in megacities and the integration of various distributed energy sources, including new energy sources, under the dual-carbon background, the distribution network exhibits characteristics such as non-unique power flow direction and multiple power sources and transfers within its fixed N-2 grid structure. Under these trends, the traditional single-mode "protection + remote sensing, remote control, and remote operation" approach is no longer suitable for the proactive and intelligent transformation and upgrading of the distribution network when faults occur.

[0066] To achieve rapid fault location, quick isolation of faulty sections, and rapid restoration of power to non-faulty sections, the development of distribution networks is focused on fault self-healing. Distribution automation is the foundation supporting the self-healing of distribution networks, and feeder automation (FA) is the key core of distribution automation.

[0067] The basic requirement for a double-ring network power supply mode is normal power supply from "dual power sources" via "dual lines." "Dual power sources" refer to busbars from different substations or different busbars within the same substation, while "dual lines" refer to two independent medium-voltage cable lines connecting two substations or different busbar sections within the same substation. With sufficient and reasonable line division, power restoration is achieved through distribution automation devices, combined with rapid switch action and power switching, isolating faulty sections, minimizing the outage area, and quickly restoring power supply, thus effectively achieving high reliability and fault dispatching. Under the double-ring network connection mode, the grid structure is standardized, effectively saving corridor resources and improving grid adaptability and power grid economy.

[0068] A typical wiring configuration for a 10kV double-ring self-healing system is as follows: Figure 1 As shown in the image.

[0069] As shown in the figure, the typical 10kV double-ring network self-healing system includes three to four KT 2 type switch stations connected in series between two 35kV and above substations, longitudinal differential protection between stations, and point-to-point distributed self-healing system within the stations.

[0070] The diagram shows substations A, B, C, and D on either side, and four 10kV switchyards E, F, G, and H in the middle. During normal operation, there are two chain loops: A1-E1-E2-F1-F2-G2-G1-H2-H1-C1 and B1-E3-E4-F3-F4-G4-G3-H4-H3-D1. In both chain loops, any switch in the series is disconnected as the open loop point. The sectionalizing switches within the substations are in the open position, while all other switches are in the closed position.

[0071] The topology of the distribution network differential self-healing system described in the technical solution of this invention is as follows: Figure 2 As shown in the image.

[0072] 5G self-healing terminals collect and process measurement and control information from local sites and other relevant sites, and complete protection and control decisions and actions through information exchange between 5G self-healing terminals. The 5G self-healing terminals communicate and synchronize time with each other via 5G, and exchange terminal information, topology information, and fault information based on the 5G network. This enables fault perception and alarm functions, automatic topology formation of the power distribution network area, and rapid and accurate fault location and isolation.

[0073] Specifically, while maintaining the existing protection devices and functions, substations are configured with 5G terminals at each station. These terminals possess the capability to acquire data from conventional outgoing line protection devices, control circuit breaker opening and closing, and interact with data from 5G self-healing terminals within the ring. Each switching station is configured with an independent 5G self-healing terminal along its busbar, enabling fault isolation and self-healing functions at the open-loop switch point of that station. Each 5G self-healing terminal independently performs functions such as logical judgment and command decision-making for the self-healing system. When a system fault occurs within the 10kV double-ring network connection range, the distributed self-healing system based on 5G communication should be able to make comprehensive judgments and decisions according to a fixed strategy, and convert tripping and closing commands into specific circuit breaker opening and closing outputs to achieve the system's self-healing function. The configuration of the distributed self-healing system based on 5G communication is as follows: Figure 3 As shown in the image.

[0074] I. Fault location strategy based on differential protection:

[0075] The longitudinal differential protection adopts the phase current phasor differential method. Its protection principle is based on Kirchhoff's current law, that is, the current flowing into a node (or closed space) is equal to the current flowing out of the node (or closed space).

[0076] The only condition for a fault criterion to be valid is the existence of an additional branch current outflow, regardless of the nature of the external power source providing the current. That is, the external power source can be a three-phase symmetrical synchronous motor or asynchronous motor, or a distributed power source using a power electronic converter interface.

[0077] Longitudinal differential protection mainly handles line faults between ring main units. Based on the measurement and control information collected by the protection and control devices, it completes protection and control decisions through information interaction and differential calculation between devices.

[0078] When a line fault occurs, the protection and control device of the faulty line detects the fault and transmits multiple instantaneous phasor currents at the time of the fault to the adjacent protection and control device. Since the sampling frequency of the protection and control device is above 4K, the protection and control device can quickly and accurately make differential protection judgments by using sampled value differential protection.

[0079] Specifically, when the line is operating normally or a fault occurs outside the line, the current flowing through both sides of the line is equal. When a fault occurs inside the line, all components connected to the power supply supply current to the fault point. The differential protection principle is as follows: Figure 4 As shown:

[0080] The operating current is:

[0081]

[0082] The braking current is:

[0083]

[0084] The operating points corresponding to the operating current and braking current are located above the proportional braking characteristic curve, such as... Figure 5 As shown in the image.

[0085] In this technical solution, the differential protection is used only as a fault location module and does not operate at the protection output. The self-healing system issues corresponding control commands based on the location results to isolate the switches on both sides of the fault.

[0086] In a distribution network, if the operating current of multiple sampling points meets the above conditions at the time of a line fault, it indicates that the fault occurred on that line, and the distribution terminals on both sides of the fault point can quickly locate the fault point.

[0087] II. Startup sequence logic of intelligent distributed FA:

[0088] According to DL / T 1910-2018 "Technical Specification for Distributed Feeder Automation of Distribution Networks", for fast-acting distributed feeder automation systems, the peer-to-peer communication delay should be less than 20ms, the completion time of upstream switch isolation during a fault should not exceed 150ms, and the time for remote signaling to the master station should be less than 3s.

[0089] From the perspective of self-healing system classification, this technical solution achieves fault location through differential protection. The FA system sends a switch trip command based on the location result to achieve fault section isolation. Therefore, from the perspective of self-healing system classification, it belongs to the fast-acting FA type. However, considering the need to accurately isolate the fault before the substation trips in the full-line circuit breaker mode, both the device fault location time and the switch action time must be taken into account.

[0090] The fast-acting FA requires the substation outgoing line setting time to be around 300ms. However, under current conditions of high reliability, such as short line length and low load capacity ratio, the inverse time characteristic curve is difficult to avoid a 300ms delay, making it difficult to guarantee protection selectivity and potentially leading to over-limit protection.

[0091] Therefore, taking advantage of the characteristics of intelligent distributed information interaction, the 5G terminal of the substation communicates with the 5G self-healing terminal via 5G to exchange fault information. After the substation self-healing terminal detects a fault, it waits for a delay of T1. If it receives the fault information from the self-healing terminal within T1, it extends the action exit time to T2. If it does not receive the fault information from the self-healing terminal within T1, it immediately takes action to ensure the differential coordination between the substation and the primary switch station.

[0092] In summary, the differential FA startup process based on 5G communication in this invention is as follows: Figure 6 As shown in the image.

[0093] 1) Begin;

[0094] 2) In full-line circuit breaker mode, a fault was detected at the switch station terminal;

[0095] 3) Intelligent distributed FA startup;

[0096] 4) Information exchange between the switching station terminal and the 5G self-healing terminal;

[0097] 5) Determine whether a 5G self-healing terminal fault information is received after the T1 delay;

[0098] 6) If a 5G self-healing terminal fault information is received after a delay of T1, the action exit time will be extended to T2.

[0099] 7) If no 5G self-healing terminal fault information is received after the T1 delay, the action exit will be activated immediately.

[0100] 8) End.

[0101] III. Optimizations based on 5G communication:

[0102] Out-of-order packet transmission in 5G mainly occurs at the air interface, specifically between the CPE (Customer Premise Equipment, a type of 5G terminal equipment. It receives 5G signals from the operator's base station and converts them into WiFi or wired signals, allowing more local devices (mobile phones, tablets, computers) to access the internet. 5G CPE functions similarly to the "optical network unit" in home fiber broadband access) and the base station. When air interface transmission malfunctions, retransmitted packets interleaving with currently transmitted packets can easily generate out-of-order data packets, thus causing differential protection to be blocked.

[0103] A. Message out-of-order handling:

[0104] The following is an illustration of message out-of-order handling: Figure 7 As shown in the image.

[0105] When an anomaly occurs in the air interface transmission between the CPE and the base station, retransmitted messages will be sequentially queued to the back of the reporting queue, resulting in out-of-order data packets. The feeder terminal has a sampling counter with a transmission sequence number to check if the data exists: when the transmission sequence number is non-zero, it is considered normal; when the transmission sequence number is less than zero, due to the interval between the protection level pointer and the buffer, it is not immediately considered a data anomaly. When the next transmission sequence number is still less than zero, it is considered a data anomaly, and the differential protection is momentarily blocked.

[0106] Out-of-order messages can easily trigger momentary blocking protection. Furthermore, the probability of out-of-order messages is higher in wireless transmission than in fiber optics. To ensure the normal operation of differential protection, correction processing is performed when out-of-order messages occur. The processing flow is as follows:

[0107] (1) When receiving wireless data, it is directly stored in the temporary data buffer in the order of reception;

[0108] (2) Take the received data points and locate the data according to the absolute time scale;

[0109] (3) Perform interpolation calculations for the corresponding data points and store them in the line protection calculation buffer;

[0110] (4) The differential protection calculation program writes data to the data buffer while reading data from the buffer to perform real-time calculation of the differential current. The read pointer lags behind the write pointer by a relatively fixed time.

[0111] (5) When a message is out of order, the write pointer will jump forward, and the jump step size is the same as the difference between the sent sequence number;

[0112] (6) When the missing frame number is received, the write pointer will turn back to fill it in, so that the data in the entire buffer is continuous again. At this time, the read pointer has not yet reached this point, and the protection program will not lock.

[0113] (7) If the missing frame is not delivered in time, the protection procedure will lock.

[0114] B. Handling message frame loss:

[0115] A diagram of the data packet buffer is shown below. Figure 8 As shown in the image.

[0116] Using the data packet buffer sequence number as a descriptive example, sequence number 1 is the latest position, sequence number 2 is the position of the previous sampling point, and so on.

[0117] All sampled values ​​on this side are set to be valid. Serial number 1 is the index position of the current sampled value on this side, which is also the position corresponding to the latest sampled value on the last side. Serial number 2 is the last point of the Fourier calculation data window.

[0118] In 5G differential service, in order to ensure sufficient time to receive data from the other side, the validity of the sample value of sequence number 2 is used to determine whether the communication message frame is lost. If the sample value flag is 0, it means that the data is valid. If the sample value flag is -1, it means that the data is invalid and enters the blocking protection.

[0119] Taking sequence numbers 3, 2, and 1 as an example, frame loss detection is performed, and the validity of sequence number 2 is used to calculate frame loss. Due to the asynchronous sampling on both sides of the differential protection device, false frame loss may occur, i.e., sequence numbers 3 and 1 are valid, while sequence number 2 is -1, but sequence numbers 3 and 1 are consecutive. In this case, no frame loss is reported, and invalid data correction is performed. If frame loss occurs consecutively a certain number of times, a communication delay is set.

[0120] IV. Engineering Simulation Testing:

[0121] Based on parameters such as 5G communication latency, 5G differential positioning time, and single-switch action time, the parameters T1 and T2 were set on-site: T1 = 40ms, T2 = 300ms.

[0122] The FA startup process for 5G differential is as follows: Figure 6 As shown.

[0123] use Figure 1 The power supply company's dual-ring network line shown is used as a test model to verify the feasibility of the above-mentioned startup timing logic.

[0124] Simulate the startup of the intelligent distributed FA under two different fault locations to verify the correctness of the proposed startup logic.

[0125] 1) Substation outgoing line fault:

[0126] The simulated fault occurs at a point on the A outgoing line of the substation, specifically between switches A1 and E1. The intelligent distributed FA should, after a 40ms delay, not activate its self-healing system, and the substation outgoing line switch A1 should trip.

[0127] After 40ms, the simulated intelligent distributed FA displays the device starting up. Since no fault information was received from the 5G terminal in the substation, the device directly trips the output circuit breaker, and the substation outgoing switch A1 trips, thus isolating the fault.

[0128] 2) Switch station outgoing line fault:

[0129] The simulated fault occurs at a point on the H outgoing line of the switching station, specifically between H1 and G3. According to the above startup logic, the D outgoing line switch D1 of the substation should not operate, and the H outgoing line switch H4 of the switching station should trip.

[0130] In the fault simulation, after a 40ms delay, the 5G self-healing terminal of substation D receives fault information from switch station H and enters delay T2. During the 300ms delay T2, the output action signal of the 5G self-healing terminal in switch station H acts on the outgoing switch H4 to trip, achieving fault isolation. After fault isolation is achieved, the fault current in the 5G self-healing terminal of substation D disappears, ending the fault handling process.

[0131] Existing intelligent distributed FA start-up mainly relies on protection action criteria and switch change logic. Due to the limitations of the overall reliability of protection devices and switching equipment, the self-healing system has poor independence and anti-interference capabilities.

[0132] The technical solution of this invention takes a distributed self-healing system for distribution networks based on 5G communication as the research object. Based on distribution network FA technology and 5G communication technology, and combined with a typical 10kV double-ring network structure topology, a differential FA start-up technology based on 5G communication is proposed.

[0133] The technical solution of this invention is guided by the need to address the limitations of intelligent distributed power supply (FA) systems. Based on "5G communication," it closely revolves around 5G communication technology and combines it with the network structure of a typical 10kV dual-ring self-healing system. By analyzing and comparing the advantages and disadvantages of common FA start-up triggering conditions, and without sacrificing both speed and sensitivity, it uses differential protection as the fault location module and adds action output timing logic to achieve a distributed self-healing system for distribution networks with good adaptability, high reliability, and fast fault isolation speed. This system meets the requirements of rapid fault location and isolation and reliable power supply restoration in distribution network A or A+ areas.

[0134] Through engineering simulation tests, the startup logic proposed in this technical solution is verified. While improving the speed of FA fault isolation, it ensures the selectivity of switching action, avoids cascading tripping, and ensures the accuracy of fault isolation.

[0135] This invention can be widely used in the operation and management of distributed self-healing systems in power distribution networks.

Claims

1. A differential FA initiation method based on 5G communication, characterized in that: 1) While maintaining the existing protection devices and functions, the substation is equipped with 5G terminals, which have the ability to collect data from conventional outgoing protection devices and control their opening and closing, and to interact with data from each 5G self-healing terminal in the ring. 2) Each substation is equipped with an independent 5G self-healing terminal along the busbar to realize the functions of open-loop switch fault isolation and self-healing switch of the substation; 3) Each 5G self-healing terminal independently completes functions including self-healing system logic judgment and command decision-making; 4) When a system fault occurs within the double-ring network connection range, the distributed self-healing system based on 5G communication makes a comprehensive judgment and decision according to a fixed strategy, and converts the trip and close commands into specific circuit breaker opening and closing outputs to realize the system self-healing function. 5) When a line fault occurs, the protection and control device of the faulty line detects the fault and transmits multiple instantaneous phasor currents at the time of the fault to the adjacent protection and control device. The protection and control device adopts sampled value differential protection to quickly and accurately make differential protection judgments. 6) When the operating current of multiple sampling points meets the differential protection judgment condition at the time of a line fault, it indicates that the fault occurred on the line, and the distribution terminals on both sides of the fault point can quickly locate the fault point. 7) The differential protection is used only as a fault location module and does not operate at the protection output. The self-healing system issues corresponding control commands based on the location results to isolate the switches on both sides of the fault. 8) Fault location is achieved through differential protection. The FA system sends a switch trip command based on the location result to achieve fault isolation function; After detecting a fault, the 5G self-healing terminal implements a differential FA startup process based on 5G communication according to the following steps: 1) Begin; 2) In full-line circuit breaker mode, a fault was detected at the switch station terminal; 3) Intelligent distributed FA startup; 4) Information exchange between the switch station terminal and the 5G self-healing terminal; 5) Determine whether a 5G self-healing terminal fault information is received after the T1 delay; 6) If a 5G self-healing terminal fault information is received after a delay of T1, the action exit time will be extended to T2. 7) If no 5G self-healing terminal fault information is received after the T1 delay, the action exit will be activated immediately; 8) End.

2. The differential FA initiation method based on 5G communication according to claim 1, characterized in that: The differential protection judgment conditions include: when the line is operating normally or a fault occurs outside the line, the current flowing through both sides of the line is equal; when a fault occurs inside the line, all components connected to the power supply provide current to the fault point. The protection principle is based on the fact that the current flowing into a node or enclosed space is equal to the current flowing out of that node or enclosed space. The only condition for a fault criterion to be valid is the existence of an additional branch current flowing out, regardless of the nature of the power source providing the current.

3. The differential FA initiation method based on 5G communication according to claim 2, characterized in that: The external power source providing the current is a three-phase symmetrical synchronous motor or asynchronous motor, or a distributed power source using a power electronic converter interface.

4. The differential FA initiation method based on 5G communication according to claim 1, characterized in that: The differential FA start-up method, in combination with parameters including 5G communication delay, 5G differential positioning time, and one-time switch action time, sets parameters T1 and T2 on site.

5. The differential FA initiation method based on 5G communication according to claim 4, characterized in that: The values ​​of the parameters T1 and T2 are as follows: T1 = 40ms, T2 = 300ms.

6. The differential FA initiation method based on 5G communication according to claim 1, characterized in that: The differential FA startup method described above performs correction processing when "out-of-order messages" occur. The processing flow is as follows: (1) When receiving wireless data, it is directly stored in a temporary data buffer in the order of reception; (2) Take the received data points and locate the data according to the absolute time scale; (3) Perform interpolation calculations for the corresponding data points and store them in the line protection calculation buffer; (4) The differential protection calculation program writes data to the data buffer while reading data from the buffer to perform real-time calculation of the differential current. The read pointer lags behind the write pointer by a relatively fixed time. (5) When a message is out of order, the write pointer will jump forward, and the jump step size is the same as the difference between the sent sequence number; (6) When the missing frame number is received, the write pointer will turn back to fill it in, so that the data in the entire buffer is continuous again. At this time, the read pointer has not yet reached this point, and the protection program will not lock. (7) If the missing frame is not delivered in time, the protection procedure will lock.

7. The differential FA initiation method based on 5G communication according to claim 1, characterized in that: The differential FA startup method described above handles "frame loss" by following these steps: Setting: The data packet buffer sequence number is used as the description instance, sequence number 1 is the latest position, sequence number 2 is the position of the previous sampling point, and so on; All sampled values ​​on this side are set to be valid. Serial number 1 is the index position of the current sampled value on this side, which is also the position corresponding to the latest sampled value on the last side. Serial number 2 is the last point of the Fourier calculation data window. In 5G differential service, the validity of the sample value of sequence number 2 is used to determine whether the communication message is lost. If the sampled value flag is 0, it indicates that the data is valid; if the sampled value flag is -1, it indicates that the data is invalid, and the system enters the interlocking protection mode.

8. The differential FA initiation method based on 5G communication according to claim 7, characterized in that: When processing "message frame loss", frame loss is judged using sequence numbers 3, 2, and 1 as examples, and frame loss is calculated based on whether sequence number 2 is valid. If a false frame loss occurs, i.e., sequence number 3 and 1 are valid, sequence number 2 is -1, but sequence numbers 3 and 1 are consecutive, no frame loss will be reported in this case, and invalid data will be corrected. If frames are dropped a certain number of times consecutively, the communication delay will be reset.

9. The differential FA initiation method based on 5G communication according to claim 1, characterized in that: The differential FA start-up method adopts an intelligent distributed information interaction mode. The substation 5G terminal and the 5G self-healing terminal communicate via 5G to exchange fault information. After the substation self-healing terminal detects a fault, it waits for a delay of T1. If it receives fault information from the self-healing terminal within T1, it extends the action exit time to T2. If it does not receive fault information from the self-healing terminal within T1, it immediately takes action to ensure the differential coordination between the substation and the primary switch station.

Images