Feeder terminal control method based on low earth orbit satellite communication and feeder terminal

Abstract

The invention discloses a feeder terminal control method based on low orbit satellite communication and a feeder terminal.The method comprises the steps that preset electric energy parameters at a feeder switch are monitored in real time through the feeder terminal, and when the feeder switch breaks down, the feeder terminal is controlled to conduct communication state detection; if at least one of the mobile network communication, the wired transmission communication and the low-orbit satellite communication of the feeder terminal is normal, judging that the communication state is normal, otherwise, judging that the communication state is abnormal; when the communication state of the feeder terminal is normal, the feeder terminal is controlled to adopt intelligent linkage decision-making feeder automation; when the communication state of the feeder terminal is abnormal, the feeder terminal is controlled to adopt on-site coincident feeder automation; and controlling the feeder terminal to carry out fault type identification and fault area identification according to the preset electric energy parameters of the low-orbit satellite in combination with a preset fault analysis algorithm, and carrying out fault removal according to preset protection action logic.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a feeder terminal control method and feeder terminal based on low-orbit satellite communication. Background Technology

[0002] A feeder terminal is a distribution automation device deployed at locations such as poles and towers of 10kV distribution networks, possessing basic functions such as remote signaling, remote measurement, remote control, and feeder automation. In existing distribution networks, with the support of traditional feeder terminals, the main methods for implementing feeder automation on 10kV overhead lines include local reclosing feeder automation and intelligent linkage decision-making feeder automation.

[0003] Local reclosing feeder automation does not rely on communication for fault handling, but requires multiple reclosing operations to locate and isolate faults and restore power to non-faulty areas. This results in slow power restoration and a poor user experience. Intelligent linkage decision-making feeder automation relies entirely on stable communication for fault handling. If one or more feeder terminals experience communication failures, fault handling becomes impossible. However, current connections between feeder terminals and the main station primarily rely on mobile communication networks and fiber optic transmission. This communication architecture has the following limitations: First, its operational stability is constrained by the geographical coverage of telecom operator base stations, equipment operating status, and power supply reliability; second, the long information transmission path not only increases system uncertainty but also introduces potential data security threats. These factors collectively restrict the overall reliability, operational stability, and geographical applicability of the system.

[0004] Therefore, a new technical solution is urgently needed to solve the technical problem of how to quickly and accurately locate distribution network faults by controlling feeder terminals. Summary of the Invention

[0005] This invention provides a feeder terminal control method and feeder terminal based on low-orbit satellite communication, which solves the technical problem of how to achieve rapid and accurate location of power distribution network faults by controlling the feeder terminal.

[0006] To achieve the above objectives, the present invention provides a feeder terminal control method based on low-Earth orbit satellite communication, comprising:

[0007] The feeder terminal monitors the preset power parameters at the feeder switch in real time. When a fault occurs at the feeder switch, the feeder terminal is controlled to perform communication status detection. If at least one of the feeder terminal's mobile network communication, wired transmission communication, and low-orbit satellite communication is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal.

[0008] When the feeder terminal communication status is normal, the feeder terminal is controlled by intelligent linkage decision-making feeder automation; when the feeder terminal communication status is abnormal, the feeder terminal is controlled by local reclosing feeder automation.

[0009] The control feeder terminal identifies the fault type and fault area based on preset power parameters and preset fault analysis algorithms, and performs fault isolation according to preset protection action logic.

[0010] Preferably, real-time monitoring of preset power parameters at the feeder switch via the feeder terminal includes:

[0011] The phase current, line voltage, zero-sequence current, and zero-sequence voltage at the feeder switch are monitored in real time through the feeder terminal.

[0012] Preferably, fault type identification includes:

[0013] (1) Overcurrent detection

[0014] Overcurrent detection is used to determine whether a phase-to-phase short-circuit fault has occurred, including:

[0015] I max =max(I a ,I b ,I c )

[0016] If I in three consecutive sampling periods max satisfy:

[0017] I max >1.2×I rated

[0018] Then it is determined to be a phase-to-phase short circuit fault, where I rated Rated current; I max This represents the maximum value of the three-phase current; I a I is the phase current; b I is the phase b current; c This represents the current in phase c.

[0019] (2) Zero-sequence voltage over-limit detection

[0020] Zero-sequence voltage over-limit detection is used to determine whether a ground fault has occurred, including:

[0021]

[0022] Where U0 is the zero-sequence voltage; U a U is the voltage of phase a; b This is the voltage of phase b; U c This is the voltage of phase c.

[0023] If the duration is greater than or equal to a preset threshold and accompanied by a sudden increase in zero-sequence current, it is determined to be a ground fault.

[0024] (3) Direction verification

[0025] Directional verification is used to reduce protection malfunctions. By comparing the current directions of the leading and lagging phases, it helps verify the consistency of the fault direction, including:

[0026] I diff =I lead ·e j120° -I lag ·e -j120°

[0027] Among them, I lead For leading phase current; I lag For the lagging phase current, I diff Let I be the difference between the two-phase currents after rotation. If the fault directions are the same, then |I| diff | approaches 0; if |I diff If the value is large, it indicates that the direction verification failed; j is the complex unit; e is the natural base.

[0028] Preferably, fault area identification includes:

[0029] Fault location is achieved through a voltage-current relationship matrix, including:

[0030] Construct a voltage-current relationship matrix before and after fault occurrence:

[0031]

[0032] Calculate the matrix difference ΔZ = Z post -Z pre By separating the voltage and current components in the matrix difference ΔZ, the voltage change ΔV and current change ΔI are obtained. Combined with line parameters, fault location is achieved.

[0033]

[0034] Among them, Z pre This is the voltage-current relationship matrix before the fault occurred; Z post This is the voltage-current relationship matrix after fault clearance; D is the fault distance, i.e., the distance from the measurement point to the fault point; L is the total line length; R is the line resistance.

[0035] Preferred options also include:

[0036] When a phase-to-phase short-circuit fault is identified, after the substation trips, it checks whether the current and voltage in the feeder terminal's operating range are overcurrent or undervoltage. If overcurrent or undervoltage exists, it queries the lower level for communication status detection. If there is no overcurrent or undervoltage, it queries the upper level for communication status detection. If the communication status detection determines that the communication status is normal, it controls the feeder terminal to maintain intelligent linkage decision-making feeder automation. If the communication status detection determines that the communication status is abnormal, it controls the feeder terminal to adopt local reclosing feeder automation.

[0037] Preferred options also include:

[0038] When a ground fault is identified, if the zero-sequence voltage of the line exceeds the limit, the feeder terminal is controlled by a voltage-controlled local reclosing feeder automation system. The voltage-controlled local reclosing feeder automation system includes triggering tripping when the zero-sequence voltage exceeds the threshold.

[0039] Preferably, the preset protection action logic includes:

[0040] If the communication status is determined to be normal:

[0041] When the fault type is a phase-to-phase short circuit fault, after the substation trips, the control feeder terminal detects the overcurrent direction; if it is an overcurrent at this end, it sends an inquiry signal to the lower level; if it is not an overcurrent at this end, it sends an inquiry signal to the upper level; after receiving the response, it coordinates to locate the fault point, and simultaneously trips the switches on both sides of the fault section, and restores power supply to the non-fault area through the tie switch.

[0042] When the fault type is a ground fault, if the zero-sequence voltage exceeds the limit, a zero-sequence current direction check is added to prevent malfunction.

[0043] If the communication status is determined to be abnormal or the zero-sequence voltage exceeds the standard, the feeder terminal adopts local reclosing feeder automation.

[0044] The present invention also provides a feeder terminal for use with the method of the present invention. The feeder terminal includes a main control unit, a communication unit, a data acquisition unit, a power management unit, and an actuator interface.

[0045] The data acquisition unit is used to collect preset power parameters at the feeder switch in real time.

[0046] The main control unit is used to monitor the preset power parameters at the feeder switch in real time. When a fault occurs at the feeder switch, the control unit performs communication status detection. If at least one of the mobile network communication, wired transmission communication and low-orbit satellite communication of the feeder terminal is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal.

[0047] The main control unit is also used to control the feeder terminal to adopt intelligent linkage decision-making feeder automation when the feeder terminal communication status is normal; and to control the feeder terminal to adopt local reclosing feeder automation when the feeder terminal communication status is abnormal.

[0048] The main control unit is also used to control the feeder terminal to identify the fault type and fault area based on the preset power parameters and the preset fault analysis algorithm, and to clear the fault according to the preset protection action logic; the preset fault analysis algorithm and the preset protection action logic are both preloaded in the main control unit.

[0049] The power management unit is used to supply power to the feeder terminal; the actuator interface is used to execute intelligent linkage decision-making feeder automation or local reclosing feeder automation according to the instructions sent by the main control unit.

[0050] The present invention has the following beneficial effects:

[0051] This invention provides a feeder terminal control method based on low-Earth orbit satellite communication. It switches between intelligent linkage decision-making feeder automation and local reclosing feeder automation based on the communication status between terminals, effectively utilizing the advantages of existing intelligent linkage decision-making feeder automation or local reclosing feeder automation. Through the coordinated use of mobile network communication, wired transmission communication, and low-Earth orbit satellite communication, the reliability of feeder terminals can be significantly improved in remote areas or complex environments with weak communication infrastructure. This invention enables rapid location and accurate judgment of distribution network faults, improving the efficiency and reliability of distribution network fault handling. The method based on this invention can handle single-phase grounding and phase-to-phase short-circuit faults.

[0052] The feeder terminal of the present invention, used in the method of the present invention, has the same beneficial effects as the method of the present invention.

[0053] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0054] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0055] Figure 1 This is a flowchart illustrating a preferred embodiment of the present invention.

[0056] Figure 2 This is a schematic diagram illustrating an implementation example of the dynamic switching mode in a preferred embodiment of the present invention. Detailed Implementation

[0057] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0058] See Figure 1 In a preferred embodiment of the present invention, a feeder terminal control method based on low-Earth orbit satellite communication is provided, comprising:

[0059] A1. The preset power parameters at the feeder switch are monitored in real time through the feeder terminal. When a fault occurs at the feeder switch, the feeder terminal is controlled to perform communication status detection. If at least one of the mobile network communication, wired transmission communication and low-orbit satellite communication of the feeder terminal is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal.

[0060] In a preferred embodiment of the present invention, real-time monitoring of preset power parameters at the feeder switch via the feeder terminal includes:

[0061] The phase current, line voltage, zero-sequence current, and zero-sequence voltage at the feeder switch are monitored in real time through the feeder terminal. Specifically, the voltage and current data of the voltage transformers (PTs) and current transformers (TAs) installed on the feeder are collected, and zero-sequence monitoring is performed simultaneously.

[0062] In a preferred embodiment of the present invention, after the feeder terminal is started, it first monitors the communication status with adjacent feeder terminals and the master station in real time through its built-in communication unit. The main control unit inside the feeder terminal dynamically evaluates the communication status based on the DSP chip. When a communication anomaly is detected (packet loss rate > 5% or latency > 50ms), it sends a command to the communication unit to immediately activate low-orbit satellite communication and achieve seamless switching of the communication path through nanosecond-level electronic switching technology. If communication fails further, the communication status is determined to be abnormal; otherwise, the communication status is determined to be normal.

[0063] In a preferred embodiment of the present invention, when using low-Earth orbit satellite communication, locally collected telemetry data (such as phase current and zero-sequence voltage) is converted into the protocol format corresponding to the low-Earth orbit satellite, and AES-256 encryption is enabled to ensure transmission security. To adapt to scenarios without mains power, the standby power consumption of the communication unit is strictly limited to below 1W, and the full-power mode is activated only when a fault is triggered.

[0064] A2. When the feeder terminal communication status is normal, the feeder terminal is controlled to adopt intelligent linkage decision-making feeder automation; when the feeder terminal communication status is abnormal, the feeder terminal is controlled to adopt local reclosing feeder automation.

[0065] In a preferred embodiment of the present invention, the principle of local reclosing feeder automation includes:

[0066] Standard local reclosing feeder automation is suitable for interrupting faults such as phase-to-phase short circuits. The terminal monitors the phase current in real time, and immediately trips if an overcurrent occurs. If the fault persists after delayed reclosing, it trips again or even blocks the circuit, thus isolating the fault. Multiple reclosing operations determine the fault isolation range. Voltage-controlled local reclosing, on the other hand, is suitable for ground faults; it triggers tripping when the zero-sequence voltage exceeds a threshold.

[0067] In a preferred embodiment of the present invention, the principle of intelligent linkage decision-making feeder automation includes:

[0068] The core mechanism of intelligent linkage decision-making feeder automation is that terminals share fault information through a high-speed communication network and execute linkage decision-making algorithms to achieve rapid and accurate fault location and isolation. This approach avoids multiple overlapping operations, speeds up power restoration, and significantly improves the user's power experience.

[0069] A3. The control feeder terminal identifies the fault type and fault area based on the preset power parameters and the preset fault analysis algorithm, and performs fault isolation according to the preset protection action logic.

[0070] In a preferred embodiment of the present invention, fault type identification includes:

[0071] (1) Overcurrent detection

[0072] Overcurrent detection is used to determine whether a phase-to-phase short-circuit fault has occurred, including:

[0073] I max =max(I a ,I b ,I c )

[0074] If I within three consecutive sampling periods (50ms / period) max satisfy:

[0075] I max >1.2×I rated

[0076] Then it is determined to be a phase-to-phase short circuit fault, where I rated Rated current; I max This represents the maximum value of the three-phase current; I a I is the phase current; b I is the phase b current; c This refers to the c-phase current.

[0077] (2) Zero-sequence voltage over-limit detection

[0078] Zero-sequence voltage over-limit detection is used to determine whether a ground fault has occurred, including:

[0079]

[0080] Where U0 is the zero-sequence voltage; U a U is the voltage of phase a; b This is the voltage of phase b; U c This is the voltage of phase c;

[0081] If the duration is greater than or equal to a preset threshold and accompanied by a sudden increase in zero-sequence current, it is determined to be a ground fault; in a preferred embodiment of the present invention, the preset threshold is preferably 50ms.

[0082] (3) Direction verification

[0083] Direction verification is used to reduce the possibility of protection malfunctions. It helps verify the consistency of fault direction by comparing the current direction of the leading phase and the lagging phase, including:

[0084] I diff =I lead ·e j120° -I lag ·e -j120°

[0085] Among them, I lead For leading phase current; I lag For the lagging phase current, I diff Let I be the difference between the two-phase currents after rotation. If the fault directions are the same, then |I| diff | approaches 0; if |I diff If the value is large, it indicates that the direction verification failed; j is the complex unit; e is the natural base.

[0086] In a preferred embodiment of the present invention, fault area identification includes:

[0087] Fault location is achieved through a voltage-current relationship matrix, including:

[0088] Construct a voltage-current relationship matrix before and after fault occurrence:

[0089]

[0090] Calculate the matrix difference ΔZ = Z post -Z pre By separating the voltage and current components in the matrix difference ΔZ, the voltage change ΔV and current change ΔI are obtained. Combined with line parameters, fault location is achieved.

[0091]

[0092] Among them, Z pre This is the voltage-current relationship matrix before the fault occurred; Z postThis is the voltage-current relationship matrix after fault clearance; D is the fault distance, i.e., the distance from the measurement point to the fault point; L is the total line length; R is the line resistance.

[0093] In a preferred embodiment of the present invention, when the fault is identified as a phase-to-phase short-circuit fault, after the substation trips, it is determined whether the current and voltage in the feeder terminal's operating range are overcurrent or undervoltage. If overcurrent or undervoltage exists, the lower level is queried for communication status detection. If there is no overcurrent or undervoltage, the upper level is queried for communication status detection. If the communication status detection determines that the communication status is normal, the feeder terminal is controlled to maintain intelligent linkage decision-making feeder automation. If the communication status detection determines that the communication status is abnormal, the feeder terminal is controlled to adopt local reclosing feeder automation.

[0094] In a preferred embodiment of the present invention, when the fault is identified as a ground fault, if the zero-sequence voltage of the line exceeds the limit, the feeder terminal is controlled to adopt voltage-controlled local reclosing feeder automation; the voltage-controlled local reclosing feeder automation includes triggering tripping when the zero-sequence voltage exceeds the threshold.

[0095] In a preferred embodiment of the present invention, the preset protection action logic includes:

[0096] If the communication status is determined to be normal:

[0097] When the fault type is a phase-to-phase short circuit fault, after the substation trips, the control feeder terminal detects the direction of the overcurrent; if it is an overcurrent at this end, it sends an inquiry signal to the lower level; if it is not an overcurrent at this end, it sends an inquiry signal to the upper level; after receiving the response, it coordinates to locate the fault point, and simultaneously trips the switches on both sides of the fault section, and restores power supply to the non-fault area through the tie switch.

[0098] When the fault type is a ground fault, if the zero-sequence voltage exceeds the limit, a zero-sequence current direction check is added to prevent false tripping.

[0099] If the communication status is determined to be abnormal or the zero-sequence voltage exceeds the standard, the feeder terminal adopts local reclosing feeder automation.

[0100] In a preferred embodiment of the present invention, if local reclosing feeder automation is adopted, the tripping logic is triggered according to the fault type; if intelligent linkage decision-making feeder automation is adopted, the fault is located and isolated in coordination with the nearby feeder terminals, and the communication status is monitored in real time to dynamically switch modes.

[0101] See Figure 2 In a preferred embodiment of the present invention, the implementation examples of the dynamic switching mode include:

[0102] If a fault occurs in the first section F1 of the circuit breaker outgoing line, and S1 has no overcurrent, S1 queries FB for overcurrent. Since there is no communication between S1 and FB, S1 uses voltage-controlled local reclosing feeder automation, tripping due to undervoltage. FB trips after one reclosing, and FB blocks reclosing. S1 is reverse-blocked—the faulty section is isolated. If S2 has no overcurrent, it queries S1. If the query is successful and there is no overcurrent, S2 maintains intelligent linkage decision-making feeder automation, and if the fault does not precede S2, it maintains the closed position. Similarly, S3 and S4 use voltage-controlled local reclosing feeder automation, and S5 uses intelligent linkage decision-making feeder automation.

[0103] This invention provides a feeder terminal control method based on low-Earth orbit satellite communication. It switches between intelligent linkage decision-making feeder automation and local reclosing feeder automation based on the communication status between terminals, effectively utilizing the advantages of existing intelligent linkage decision-making feeder automation or local reclosing feeder automation. Through the coordinated use of mobile network communication, wired transmission communication, and low-Earth orbit satellite communication, the reliability of feeder terminals can be significantly improved in remote areas or complex environments with weak communication infrastructure. This invention enables rapid location and accurate judgment of distribution network faults, improving the efficiency and reliability of distribution network fault handling. The method based on this invention can handle single-phase grounding and phase-to-phase short-circuit faults.

[0104] In a preferred embodiment of the present invention, a feeder terminal is also provided for use in the method of the present invention. The feeder terminal includes a main control unit, a communication unit, a data acquisition unit, a power management unit, and an actuator interface.

[0105] The data acquisition unit is used to collect preset power parameters at the feeder switch in real time. The data acquisition unit collects the voltage and current data of the voltage transformers (PT) and current transformers (TA) installed on the feeder, and performs zero-sequence monitoring at the same time.

[0106] The main control unit is used to monitor the preset power parameters at the feeder switch in real time. When a fault occurs at the feeder switch, the control unit performs communication status detection. If at least one of the mobile network communication, wired transmission communication and low-orbit satellite communication of the feeder terminal is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal.

[0107] The main control unit is also used to control the feeder terminal to adopt intelligent linkage decision-making feeder automation when the feeder terminal communication status is normal; and to control the feeder terminal to adopt local reclosing feeder automation when the feeder terminal communication status is abnormal.

[0108] The main control unit is also used to control the feeder terminal to identify fault types and fault areas based on preset power parameters and a preset fault analysis algorithm, and to clear faults according to preset protection action logic; both the preset fault analysis algorithm and the preset protection action logic are pre-loaded in the main control unit. In a preferred embodiment of the present invention, the main control unit uses a DSP chip.

[0109] In a preferred embodiment of the present invention, the communication unit includes, but is not limited to, communication methods such as mobile network communication, RS485, optical fiber, and low-Earth orbit satellite communication. The communication unit preferentially uses mobile network communication, RS485, and optical fiber, and only activates low-Earth orbit satellite communication when the above three fail. The communication unit adopts an omnidirectional high-gain antenna design to improve signal reception capability.

[0110] The power management unit is used to supply power to the feeder terminal. In addition to supporting 220V AC mains power, the power management unit also supports backup power supply and is equipped with charge / discharge protection and automatic undervoltage alarm functions. In a preferred embodiment of the present invention, the standby power consumption of the feeder terminal is below 1W.

[0111] The actuator interface is used to execute intelligent linkage decision-making feeder automation or local reclosing feeder automation according to the instructions sent by the main control unit.

[0112] In a preferred embodiment of the invention, the feeder terminal is deployed at the feeder switch to collect data such as phase current, line voltage, zero-sequence current, and zero-sequence voltage in real time. When an anomaly (such as overcurrent or undervoltage) is detected, it indicates a possible fault. The feeder terminal sends an inquiry signal to neighboring feeder terminals. If the inquiry is successful, communication between the terminals is unimpeded. The feeder terminals share data and perform distributed decision-making: all feeder terminals collaboratively analyze the fault location. Once the fault point is located, the feeder terminal directly trips and isolates the faulty area via remote control, restoring power to the non-faulty area. The entire process is fast and does not require multiple reclosing operations, reducing power outage time.

[0113] The feeder terminal of the present invention, used in the method of the present invention, has the same beneficial effects as the method of the present invention.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A feeder terminal control method based on low-Earth orbit satellite communication, characterized in that, include: The feeder terminal monitors the preset power parameters at the feeder switch in real time. When a fault occurs at the feeder switch, the feeder terminal is controlled to perform communication status detection. If at least one of the feeder terminal’s mobile network communication, wired transmission communication and low-orbit satellite communication is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal. When the feeder terminal communication status is normal, the feeder terminal is controlled by intelligent linkage decision-making feeder automation; when the feeder terminal communication status is abnormal, the feeder terminal is controlled by local reclosing feeder automation. The control feeder terminal identifies the fault type and fault area based on the preset power parameters and the preset fault analysis algorithm, and performs fault isolation according to the preset protection action logic.

2. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 1, characterized in that, The real-time monitoring of preset power parameters at the feeder switch via the feeder terminal includes: The phase current, line voltage, zero-sequence current, and zero-sequence voltage at the feeder switch are monitored in real time through the feeder terminal.

3. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 2, characterized in that, The fault type identification includes: (1) Overcurrent detection Overcurrent detection is used to determine whether a phase-to-phase short-circuit fault has occurred, including: I max =max(I a ,I b ,I c ) If I in three consecutive sampling periods max satisfy: I max >1.2×I rated Then it is determined to be a phase-to-phase short circuit fault, where I rated Rated current; I max This represents the maximum value of the three-phase current; I a I is the phase current; b I is the phase b current; c This refers to the c-phase current. (2) Zero-sequence voltage over-limit detection Zero-sequence voltage over-limit detection is used to determine whether a ground fault has occurred, including: Where U0 is the zero-sequence voltage; U a U is the voltage of phase a; b This is the voltage of phase b; U c This is the voltage of phase c; If the duration is greater than or equal to the preset threshold and accompanied by a sudden increase in zero-sequence current, it is determined to be a ground fault; (3) Direction verification Directional verification is used to reduce protection malfunctions. By comparing the current directions of the leading and lagging phases, it helps verify the consistency of the fault direction, including: I diff =I lead ·e j120° -I lag ·e -j120° Among them, I lead For leading phase current; I lag For the lagging phase current, I diff Let I be the difference between the two-phase currents after rotation. If the fault directions are the same, then |I| diff | approaches 0; if |I diff If the value is large, it indicates that the direction verification failed; j is the complex unit; e is the natural base.

4. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 3, characterized in that, The fault area identification includes: Fault location is achieved through a voltage-current relationship matrix, including: Construct a voltage-current relationship matrix before and after fault occurrence: Calculate the matrix difference ΔZ = Z post -Z pre By separating the voltage and current components in the matrix difference ΔZ, the voltage change ΔV and current change ΔI are obtained. Combined with line parameters, fault location is achieved. Among them, Z pre This is the voltage-current relationship matrix before the fault occurred; Z post This is the voltage-current relationship matrix after fault clearance; D is the fault distance, i.e., the distance from the measurement point to the fault point; L is the total line length; R is the line resistance.

5. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 4, characterized in that, Also includes: When a phase-to-phase short-circuit fault is identified, after the substation trips, it checks whether the current and voltage in the feeder terminal's operating range are overcurrent or undervoltage. If overcurrent or undervoltage exists, it queries the lower level for communication status detection. If there is no overcurrent or undervoltage, it queries the upper level for communication status detection. If the communication status detection determines that the communication status is normal, it controls the feeder terminal to maintain intelligent linkage decision-making feeder automation. If the communication status detection determines that the communication status is abnormal, it controls the feeder terminal to adopt local reclosing feeder automation.

6. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 5, characterized in that, Also includes: When a ground fault is identified, if the zero-sequence voltage of the line exceeds the limit, the feeder terminal is controlled to adopt voltage-controlled local reclosing feeder automation. The voltage-controlled local reclosing feeder automation includes triggering tripping when the zero-sequence voltage exceeds a threshold.

7. The feeder terminal control method based on low-Earth orbit satellite communication according to claim 6, characterized in that, The preset protection action logic includes: If the communication status is determined to be normal: When the fault type is a phase-to-phase short circuit fault, after the substation trips, the control feeder terminal detects the direction of the overcurrent; if it is an overcurrent at this end, it sends an inquiry signal to the lower level; if it is not an overcurrent at this end, it sends an inquiry signal to the upper level; after receiving the response, it coordinates to locate the fault point, and simultaneously trips the switches on both sides of the fault section, and restores power supply to the non-fault area through the tie switch. When the fault type is a ground fault, if the zero-sequence voltage exceeds the limit, a zero-sequence current direction check is added to prevent false tripping. If the communication status is determined to be abnormal or the zero-sequence voltage exceeds the standard, the feeder terminal adopts local reclosing feeder automation.

8. A feeder terminal for use in the method according to any one of claims 1 to 7, characterized in that, The feeder terminal includes a main control unit, a communication unit, a data acquisition unit, a power management unit, and an actuator interface; The data acquisition unit is used to collect preset power parameters at the feeder switch in real time. The main control unit is used to monitor the preset power parameters at the feeder switch in real time. When a fault occurs at the feeder switch, it controls the communication unit to perform communication status detection. If at least one of the mobile network communication, wired transmission communication and low-orbit satellite communication of the feeder terminal is normal, the communication status is determined to be normal; otherwise, the communication status is determined to be abnormal. The main control unit is also used to control the feeder terminal to adopt intelligent linkage decision-making feeder automation when the feeder terminal communication status is normal; and to control the feeder terminal to adopt local reclosing feeder automation when the feeder terminal communication status is abnormal. The main control unit is also used to control the feeder terminal to identify the fault type and fault area according to the preset power parameters and the preset fault analysis algorithm, and to clear the fault according to the preset protection action logic; the preset fault analysis algorithm and the preset protection action logic are both preloaded in the main control unit; The power management unit is used to supply power to the feeder terminal; the actuator interface is used to execute intelligent linkage decision-making feeder automation or local reclosing feeder automation according to the instructions sent by the main control unit.

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