A method and system for automatic switching on and off of power distribution network undervoltage protection

Abstract

The present invention discloses a method and system for automatically switching on and off the undervoltage protection of a distribution network, aiming to solve the technical problems in the prior art that the operation and maintenance workload of the undervoltage protection switching on and off of the distribution network is large and prone to errors. It includes: obtaining a distribution network system, wherein a distributed terminal is configured at each node of the distribution network system; locating the node directly connected to the substation according to the peer-to-peer communication between the distributed terminals in the distribution network system; switching the distributed terminal configured at the node directly connected to the substation into the undervoltage protection function; obtaining the communication message of each distributed terminal; when any distributed terminal has communication abnormality, the entire distribution network system is switched off from the undervoltage protection function. The present invention can realize the automatic switching on and off function of the undervoltage protection of the substation incoming line station in the distribution network, greatly reducing the operation and maintenance workload of the distribution network equipment and improving the stability of the operation of the distribution network system.

Description

Technical Field

[0001] The invention relates to a method and system for automatic switching on and off of voltage loss protection for a distribution network, belonging to the technical field of voltage loss protection for distribution stations. Background Art

[0002] In the distribution network with ring network connection, the configuration of distributed terminal equipment to achieve rapid fault location and isolation and rapid self-healing of non-fault power-off areas has become the mainstream technical solution in recent years. Distributed terminals are secondary devices that can achieve rapid fault location, isolation and rapid power supply restoration in non-fault power-off areas based on the peer-to-peer communication function between terminals when a system failure occurs. However, there is no distributed terminal configured on the substation side. When the substation incoming line loses pressure, the system cannot accurately locate the fault. Therefore, the stations directly connected to the substation and powered by it need to be configured with undervoltage protection, that is, when the incoming line of the first station is in the closed position and pressure state, and changes to the pressure-free state, it will be delayed tripped and wait for the open-loop point switch to close and restore power supply. Due to the complex structure of the distribution network system and the changeable operation mode, the undervoltage protection of each station often needs to be activated and deactivated, which not only has a large workload of operation and maintenance but also is prone to errors. Summary of the invention

[0003] In order to solve the problem that the operation and maintenance workload of pressure protection switching in distribution network in the prior art is large and errors are prone to occur, the present invention proposes a method and system for automatic switching of undervoltage protection of distribution network, which realizes the automatic switching function of undervoltage protection of substation incoming line site in the distribution network based on peer-to-peer communication between distributed terminals, greatly reduces the operation and maintenance workload of distribution network equipment, and improves the stability of distribution network system operation.

[0004] In order to solve the above technical problems, the present invention adopts the following technical means:

[0005] In a first aspect, the present invention proposes a method for automatically switching on and off of a power distribution network undervoltage protection, comprising the following steps:

[0006] Acquire a distribution network system, wherein a distributed terminal is configured at each node of the distribution network system;

[0007] Locate nodes directly connected to substations based on peer-to-peer communication between distributed terminals in the distribution network system;

[0008] The distributed terminal configured at the node directly connected to the substation is put into the undervoltage protection function;

[0009] Obtain communication messages from each distributed terminal;

[0010] When any distributed terminal communication is abnormal, the entire distribution network system will exit the undervoltage protection function.

[0011] In combination with the first aspect, further, distributed terminals are configured step by step in the distribution network system, and each level of node is configured with a distributed terminal. The distributed terminals in the same distribution network system use the same model and program version.

[0012] In combination with the first aspect, further, according to the position of each distributed terminal in the power supply circuit in the distribution network system, a number is configured for each distributed terminal:

[0013] Obtain two nodes directly connected to the substation in the distribution network system, set one of the nodes as the starting point of the power supply loop, and the other node as the end point of the power supply loop;

[0014] The distributed terminal configuration number at each node is sequentially assigned from the starting point to the end point, wherein the distributed terminal number value at the starting point is the smallest, and the distributed terminal number value at the end point is the largest, and the number increases from the starting point to the end point according to a preset step size.

[0015] In combination with the first aspect, further, based on the peer-to-peer communication between the distributed terminals in the distribution network system, the node directly connected to the substation is located, and the method is as follows:

[0016] Using each distributed terminal in the distribution network system to receive a communication message sent outward by other distributed terminals, the communication message includes the distributed terminal number, communication status, protection action information, fault location and isolation information;

[0017] If the number of the current distributed terminal is smaller than the number in all the communication messages it has received, the node where the distributed device terminal is located is the node directly connected to the substation and is recorded as the starting point;

[0018] If the number of the current distributed terminal is greater than the numbers in all the communication messages it has received, the node where the distributed device terminal is located is the node directly connected to the substation and is recorded as the end point.

[0019] In combination with the first aspect, further, when any distributed terminal communication is abnormal, the entire distribution network system exits the undervoltage protection function, the method is:

[0020] Each distributed terminal in the distribution network system counts the number and quantity of distributed terminals communicating with itself according to the communication messages it receives;

[0021] When i The distributed terminal cannot receive the j When the communication message of a distributed terminal or the duration of receiving the communication message exceeds the threshold, the i A distributed terminal and j The communication of the distributed terminal is interrupted. iThe communication status of the distributed terminal communication message is interrupted, and the communication message with the interruption flag is sent out. j The distributed terminal is i Distributed terminals communicating with each other, i =1,2,…, n , j =1,2,…, n ,and i ≠ j , n is the total number of distributed terminals in the distribution network system;

[0022] When i When a distributed terminal cannot receive the communication message of any distributed terminal, it determines i The distributed terminal itself has abnormal communication. i An interrupt flag is set in the communication state of a distributed terminal communication message, and the communication message with the interrupt flag is sent outward;

[0023] When the distributed terminal at the node directly connected to the substation has abnormal communication or receives a communication message with an interruption flag set, the undervoltage protection function is exited.

[0024] In combination with the first aspect, further, the method further includes the following steps:

[0025] When the number of nodes in the distribution network system decreases, the distributed terminals of the reduced nodes are removed from the distribution network system, the remaining distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated;

[0026] When a node is added in the distribution network system, the device number of the distributed terminal on the node is set according to the position of the added node in the power supply circuit, all distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated;

[0027] The distributed terminals directly connected to the substation and with the incoming line switches in the closed position will automatically enter the undervoltage protection function, and other distributed terminals in the distribution network system will automatically exit the undervoltage protection function.

[0028] In combination with the first aspect, further, the nodes in the distribution network system include switch stations, substations, distribution rooms, distribution rooms, and distribution poles.

[0029] In combination with the first aspect, further, the inlet and outlet switches of each node in the distribution network system are defined according to the position of the node in the power supply circuit:

[0030] Set the switch closest to the starting point as switch 1 of the node, and set the switch closest to the end point as switch 2 of the node;

[0031] When the switch 1 position of the node as the starting point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function; when the switch 2 of the node as the end point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function.

[0032] In a second aspect, the present invention proposes a distribution network undervoltage protection automatic switching system, comprising:

[0033] A distributed terminal configuration module, used to configure distributed terminals step by step in the distribution network system;

[0034] A node positioning module is used to locate nodes directly connected to the substation based on peer-to-peer communication between distributed terminals in the distribution network system;

[0035] The undervoltage protection input module is used to put the distributed terminal configured at the node directly connected to the substation into the undervoltage protection function;

[0036] A message collection module is used to obtain communication messages from each distributed terminal;

[0037] The undervoltage protection exit module is used to exit the undervoltage protection function of the entire distribution network system when any distributed terminal communication is abnormal.

[0038] In combination with the second aspect, further, the system also includes a system update module, which is used to synchronously increase or decrease the distributed terminals in the distribution network system when the nodes in the distribution network system increase or decrease, restart the updated distributed terminals, relocate the nodes directly connected to the substation, and activate the undervoltage protection function.

[0039] The following advantages can be obtained by using the above technical means:

[0040] The present invention proposes a method and system for automatically switching on and off the undervoltage protection of a distribution network. Aiming at the characteristics of the complex network structure and changeable operation modes of the distribution network system, the automatic switching on and off function of the undervoltage protection of the substation incoming line site in the distribution network is realized based on peer-to-peer communication between distributed terminals, which greatly reduces the operation and maintenance workload of the distribution network equipment, improves the stability of the operation of the distribution network system, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of the steps of a method for automatic switching on and off of a power distribution network undervoltage protection according to the present invention;

[0042] Figure 2 Schematic diagram of a power distribution network system in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below in conjunction with the accompanying drawings:

[0044] Since the distribution network system under the ring network connection mode has a complex structure and changeable operation modes, the undervoltage protection of each station often needs to be activated and deactivated, which not only has a large workload for operation and maintenance but is also prone to errors. Therefore, the present invention proposes an automatic activation and deactivation method for undervoltage protection of a distribution network. The method of the present invention is suitable for the distribution network of a ring network connection system. The nodes of the system can be switch stations, substations, distribution rooms, distribution rooms, distribution poles, etc. The wiring methods can be ordinary ring type, handle ring type, double-way handle ring type and other ring network wiring methods.

[0045] like Figure 1 As shown, the method of the present invention specifically comprises the following steps:

[0046] Step A: obtain a distribution network system, and configure a distributed terminal at each node of the distribution network system.

[0047] Distributed terminals are configured step by step in the distribution network system. Each level of node is configured with a distributed terminal. The distributed terminals in the same distribution network system use the same model and program version. The system is scalable. A single system supports no less than 8 nodes and no less than 8 cascade levels.

[0048] Distributed terminals can quickly locate and isolate faults and quickly restore power to non-faulty areas. When a fault occurs somewhere in the system, the fault is isolated by external protection or distributed terminal equipment. After confirming that the fault isolation is complete, the distributed terminal closes the open-loop point switch to restore power to non-faulty areas.

[0049] In order to facilitate the positioning of distributed terminals, the method of the present invention needs to configure numbers for each distributed terminal according to the position of each distributed terminal in the power supply circuit in the distribution network system after completing the configuration of the distributed terminal:

[0050] According to the peer-to-peer communication between distributed terminals, two nodes directly connected to the substation in the distribution network system are obtained, and one of the nodes is selected as the starting point of the power supply loop, and the other node is selected as the end point of the power supply loop.

[0051] From the starting point to the end point, the distributed terminal configuration number at each node is given in turn. The number configuration rule is: the distributed terminal number value at the starting point is the smallest, and the distributed terminal number value at the end point is the largest. The number increases from the starting point to the end point according to the preset step size, thereby ensuring that the number of the upstream device in the system must be smaller than the number of the downstream device.

[0052] Step B: Locate the node directly connected to the substation based on the peer-to-peer communication between the distributed terminals in the distribution network system.

[0053] Step B01: Use each distributed terminal in the distribution network system to receive communication messages sent out by other distributed terminals. The communication messages contain the distributed terminal number, communication status, protection action information, fault location and isolation information, etc.

[0054] In the embodiment of the present invention, when the message content of a distributed terminal remains unchanged, the communication message is sent out at a fixed time interval. When the message content changes, the distributed terminal immediately sends the communication message out.

[0055] Step B02: If the number of the current distributed terminal is smaller than the numbers in all the communication messages it has received, the node where the distributed device terminal is located is the node directly connected to the substation and is recorded as the starting point.

[0056] Step B03: If the number of the current distributed terminal is greater than the numbers in all the communication messages it has received, the node where the distributed device terminal is located is a node directly connected to the substation and is recorded as the end point.

[0057] In the embodiment of the present invention, according to the different connection relationships between nodes at various levels in the distribution network, the number of communication messages received by the distributed terminal is also different, which can be distinguished as follows:

[0058] When a distributed terminal can only receive a communication message with one number, it means that the distributed terminals in the system are connected in series, and each distributed terminal only communicates with the distributed terminal of the adjacent node. If the number of the current distributed terminal is smaller than the number of the adjacent distributed terminal, the node where it is located is determined to be the starting point. If the number of the current distributed terminal is larger than the number of the adjacent distributed terminal, the node where it is located is determined to be the end point.

[0059] When a distributed terminal can receive communication messages with more than two numbers, it means that the distributed terminals in the system communicate in a ring network. If the number of the current distributed terminal is the smallest compared with the numbers of all distributed terminals that have received the message, then the node where it is located is determined to be the starting point. If the number of the current distributed terminal is the largest compared with the numbers of all distributed terminals that have received the message, then the node where it is located is determined to be the end point.

[0060] Step C: Enable the voltage loss protection function of the distributed terminal configured at the node directly connected to the substation to facilitate accurate fault location when the substation incoming line loses voltage.

[0061] Step D: Based on the distributed terminals in the distribution network system, the communication messages of each distributed terminal are obtained in real time as a basis for subsequent operations.

[0062] Step E: When any distributed terminal communication is abnormal, the entire distribution network system will exit the undervoltage protection function.

[0063] Step E01: Each distributed terminal in the distribution network system counts the number and quantity of distributed terminals communicating with itself according to the communication messages it receives.

[0064] Step E02: i The distributed terminal cannot receive the j When the communication message of a distributed terminal or the duration of receiving the communication message exceeds the threshold, the i A distributed terminal and j The communication of the distributed terminal is interrupted. i The communication status of the distributed terminal communication message is interrupted, and the communication message with the interruption flag is sent out. j The distributed terminal is i Distributed terminals communicating with each other, i =1,2,…, n , j =1,2,…, n ,and i ≠ j , n is the total number of distributed terminals in the distribution network system.

[0065] Step E03: i When a distributed terminal cannot receive the communication message of any distributed terminal, it determines i The distributed terminal itself has abnormal communication. i An interrupt flag is set in the communication status of a distributed terminal communication message, and the communication message with the interrupt flag is sent outward.

[0066] Step E04: when the distributed terminal at the node directly connected to the substation has a communication abnormality or receives a communication message with an interruption flag set, the undervoltage protection function is exited.

[0067] In the embodiment of the present invention, when the distribution network system is connected as a ring network, information is shared between distributed terminals. If any distributed terminal is abnormal, the distributed terminals at the nodes directly connected to the substation can receive the communication message with the interruption mark set; when the distribution network system is connected in series, the distributed terminal that receives the communication message with the interruption mark needs to forward the interruption mark to other distributed terminals, and ensure that the distributed terminals at the nodes directly connected to the substation can receive the communication message with the interruption mark set by continuous forwarding. Step F: When the system structure changes, the equipment that has been put into operation does not need to be re-adjusted. After the new system establishes communication, it automatically determines the equipment that needs to be put into or out of the undervoltage protection function.

[0068] Step F01: When the number of nodes in the distribution network system decreases, the distributed terminals of the reduced nodes are removed from the distribution network system, the remaining distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated.

[0069] Step F02: When a node is added in the distribution network system, the device number of the distributed terminal on the node is set according to the position of the added node in the power supply circuit, all distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated.

[0070] Step F03: The distributed terminal directly connected to the substation and with the incoming line switch in the closed position is automatically put into the undervoltage protection function, and other distributed terminals in the distribution network system automatically exit the undervoltage protection function, and return to step D.

[0071] In the embodiment of the present invention, the inlet and outlet switches of each node in the power distribution network system are defined according to the position of the node in the power supply circuit.

[0072] Set the switch that is closer to the starting point as switch 1 of the node, and set the switch that is closer to the end point as switch 2 of the node.

[0073] When the switch 1 position of the node as the starting point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function; when the switch 2 of the node as the end point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function.

[0074] In order to verify the effect of the method of the present invention, the present invention provides the following examples:

[0075] (1) Obtain the distribution network system, such as Figure 2 As shown, the distribution network in the example is a double-circuit pull-ring type connection, with a total of two ring network systems, each with four station-level nodes, and distributed terminals are configured on bus 1 and bus 2 at the four sites.

[0076] Set a number for each distributed terminal. The increment step from the starting point to the end point can be set to 5. The starting point device number can be set to 100, which is convenient for adding nodes between the substation and the lower-level nodes and between nodes when the system structure changes. Figure 2 In the example, the numbers of the distributed terminal devices from the first-level site to the fourth-level site can be set to 100, 105, 110, and 115 respectively. The open-loop point of the system in the current operating state is switch 105.

[0077] (2) Based on the peer-to-peer communication between the distributed terminals in the distribution network system, locate the nodes directly connected to the substation, and put the distributed terminals configured at the nodes directly connected to the substation into the undervoltage protection function. Figure 2 In the example, the distributed terminal equipment from the first-level site to the fourth-level site is a ring network communication. The first-level site with the smallest number identifies itself as the starting point, and switch 1 (102 is in the closed position); the fourth-level site with the smallest number identifies itself as the starting point, and switch 2 (402 is in the closed position). Therefore, the distributed terminal equipment between the first-level site and the fourth-level site automatically activates its undervoltage protection function.

[0078] (3) Obtain the communication messages of each distributed terminal. When any distributed terminal has communication abnormality or communication interruption, an alarm signal is generated according to the distributed terminal, and the entire distribution network system exits the undervoltage protection function.

[0079] For each distributed terminal, when the message content remains unchanged, the time interval for sending communication messages outward is set to 5 seconds, that is, the message heartbeat time; the threshold for judging the communication terminal is set to 20 seconds, that is, 4 times the message heartbeat time.

[0080] Assuming that the distributed terminal at the secondary site is abnormally unable to send communication messages, and the distributed terminals at the primary site and the fourth site do not receive the communication messages from the distributed terminal at the secondary site after 20 seconds, it is determined that the communication with the distributed terminal at the secondary site is interrupted, and the respective undervoltage protection functions are automatically exited.

[0081] (4) Assuming that a first-level site is added between substation A and the first-level site, the number of the distributed terminal of the newly added site can be set to 95. After the new system establishes communication and re-completes node identification, the undervoltage protection function of the newly added site (95) is activated, and the undervoltage protection function of the original first-level site (100) is deactivated; Assuming that a first-level site is added between the second-level site and the third-level site, the number of the distributed terminal of the newly added site can be set to 107. After the new system establishes communication and re-completes node identification, since the new site is not directly connected to the substation, the activation and deactivation status of the undervoltage protection remains unchanged, and the undervoltage protection function of the newly added site is not activated; Assuming that the first-level site exits the system and re-completes node identification, at this time the second-level site is directly connected to substation A, and the undervoltage protection function of the second-level site is activated.

[0082] The present invention also proposes an automatic switching system for undervoltage protection of a distribution network, comprising a distributed terminal configuration module, a node positioning module, an undervoltage protection switching module, a message collection module, an undervoltage protection switching module and a system update module.

[0083] The distributed terminal configuration module is mainly used to configure distributed terminals step by step in the distribution network system, and to set numbers for the distributed terminals according to their positions in the power supply circuit.

[0084] The node positioning module is mainly used to locate the nodes directly connected to the substation based on the peer-to-peer communication between the distributed terminals in the distribution network system. The specific operation of the node positioning module is consistent with step B of the method of the present invention.

[0085] The undervoltage protection input module is mainly used to put the distributed terminal configured at the node directly connected to the substation into the undervoltage protection function.

[0086] The message collection module is mainly used to obtain the communication messages of each distributed terminal. The communication messages contain the distributed terminal number, communication status, protection action information, fault location and isolation information, etc.

[0087] The undervoltage protection exit module is mainly used to exit the undervoltage protection function of the entire distribution network system when any distributed terminal communication is abnormal. The specific operation of the undervoltage protection exit module is consistent with step E of the method of the present invention.

[0088] The system update module is used to increase or decrease the distributed terminals in the distribution network system synchronously when the nodes in the distribution network system increase or decrease, restart the updated distributed terminals, relocate the nodes directly connected to the substation, and activate the undervoltage protection function. The specific operation of the system update module is consistent with step F of the present invention.

[0089] In view of the complex network structure and changeable operation modes of the distribution network system, the present invention realizes the automatic activation and deactivation function of the voltage loss protection of the substation incoming line site in the distribution network based on the peer-to-peer communication between distributed terminals, which greatly reduces the operation and maintenance workload of the distribution network equipment, improves the stability of the operation of the distribution network system, and has broad application prospects.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for automatically switching on and off for voltage loss protection of a distribution network, characterized in that: The steps include: Acquire a distribution network system, wherein a distributed terminal is configured at each node of the distribution network system; Locate nodes directly connected to substations based on peer-to-peer communication between distributed terminals in the distribution network system; The distributed terminal configured at the node directly connected to the substation is put into the undervoltage protection function; Obtain communication messages from each distributed terminal; When any distributed terminal communication is abnormal, the entire distribution network system will exit the undervoltage protection function; Based on the peer-to-peer communication between distributed terminals in the distribution network system, the nodes directly connected to the substation are located by: Using each distributed terminal in the distribution network system to receive a communication message sent outward by other distributed terminals, the communication message includes the distributed terminal number, communication status, protection action information, fault location and isolation information; If the number of the current distributed terminal is smaller than the number in all the communication messages it has received, the node where the distributed terminal is located is the node directly connected to the substation and is recorded as the starting point; If the number of the current distributed terminal is greater than the numbers in all the communication messages it has received, the node where the distributed terminal is located is the node directly connected to the substation and is recorded as the end point; When any distributed terminal communication is abnormal, the entire distribution network system will exit the undervoltage protection function. The method is: Each distributed terminal in the distribution network system counts the number and quantity of distributed terminals communicating with itself according to the communication messages it receives; When i The distributed terminal cannot receive the j When the communication message of a distributed terminal or the duration of receiving the communication message exceeds the threshold, the i A distributed terminal and j The communication of the distributed terminal is interrupted. i The communication status of the distributed terminal communication message is interrupted, and the communication message with the interruption flag is sent out. j The distributed terminal is i Distributed terminals communicating with each other, i =1,2,…, n , j =1,2,…, n ,and i ≠ j , n is the total number of distributed terminals in the distribution network system; When i When a distributed terminal cannot receive the communication message of any distributed terminal, it determines i The distributed terminal itself has abnormal communication. i An interrupt flag is set in the communication state of a distributed terminal communication message, and the communication message with the interrupt flag is sent outward; When the distributed terminal at the node directly connected to the substation has abnormal communication or receives a communication message with an interruption flag set, the undervoltage protection function is exited.

2. A method for automatic switching on and off of power distribution network undervoltage protection according to claim 1, characterized in that: Distributed terminals are configured step by step in the distribution network system. Each node level is configured with a distributed terminal. The distributed terminals in the same distribution network system use the same model and program version.

3. A method for automatic switching on and off of power distribution network undervoltage protection according to claim 1, characterized in that: According to the position of each distributed terminal in the power supply circuit of the distribution network system, each distributed terminal is assigned a number: Obtain two nodes directly connected to the substation in the distribution network system, set one of the nodes as the starting point of the power supply loop, and the other node as the end point of the power supply loop; The distributed terminal configuration number at each node is sequentially assigned from the starting point to the end point, wherein the distributed terminal number value at the starting point is the smallest, and the distributed terminal number value at the end point is the largest, and the number increases from the starting point to the end point according to a preset step size.

4. A method for automatically switching on and off of a power distribution network undervoltage protection according to claim 1, characterized in that: The method further comprises the steps of: When the number of nodes in the distribution network system decreases, the distributed terminals of the reduced nodes are removed from the distribution network system, the remaining distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated; When a node is added to the distribution network system, the number of the distributed terminal on the node is set according to the position of the added node in the power supply circuit, all distributed terminals in the distribution network system are restarted, the communication of the distributed terminals is reinitialized, and the nodes directly connected to the substation are relocated; The distributed terminals directly connected to the substation and with the incoming line switches in the closed position will automatically enter the undervoltage protection function, and other distributed terminals in the distribution network system will automatically exit the undervoltage protection function.

5. A method for automatic switching on and off of voltage loss protection in a distribution network according to claim 1, characterized in that: The nodes in the distribution network system include switch stations, substations, distribution rooms, distribution rooms, and distribution poles.

6. A method for automatically switching on and off of a power distribution network undervoltage protection according to claim 1, characterized in that: Define the incoming and outgoing line switches of each node in the distribution network system according to the position of the node in the power supply circuit: Set the switch closest to the starting point as switch 1 of the node, and set the switch closest to the end point as switch 2 of the node; When the switch 1 position of the node as the starting point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function; when the switch 2 of the node as the end point in the distribution network system is in the open position, the distributed terminal at the node is exited from the undervoltage protection function.

7. A distribution network undervoltage protection automatic switching system, characterized in that: include: A distributed terminal configuration module, used to configure distributed terminals step by step in the distribution network system; A node positioning module is used to locate nodes directly connected to the substation based on peer-to-peer communication between distributed terminals in the distribution network system; The undervoltage protection input module is used to put the distributed terminal configured at the node directly connected to the substation into the undervoltage protection function; A message collection module is used to obtain communication messages from each distributed terminal; The undervoltage protection exit module is used to exit the undervoltage protection function of the entire distribution network system when any distributed terminal communication is abnormal; The node location module is configured to: Using each distributed terminal in the distribution network system to receive a communication message sent outward by other distributed terminals, the communication message includes the distributed terminal number, communication status, protection action information, fault location and isolation information; If the number of the current distributed terminal is smaller than the number in all the communication messages it has received, the node where the distributed terminal is located is the node directly connected to the substation and is recorded as the starting point; If the number of the current distributed terminal is greater than the numbers in all the communication messages it has received, the node where the distributed terminal is located is the node directly connected to the substation and is recorded as the end point; The undervoltage protection exit module is configured to: Each distributed terminal in the distribution network system counts the number and quantity of distributed terminals communicating with itself according to the communication messages it receives; When i The distributed terminal cannot receive the j When the communication message of a distributed terminal or the duration of receiving the communication message exceeds the threshold, the i A distributed terminal and j The communication of the distributed terminal is interrupted. i The communication status of the distributed terminal communication message is interrupted, and the communication message with the interruption flag is sent out. j The distributed terminal is i Distributed terminals communicating with each other, i =1,2,…, n , j =1,2,…, n ,and i ≠ j , n is the total number of distributed terminals in the distribution network system; When i When a distributed terminal cannot receive the communication message of any distributed terminal, it determines i The distributed terminal itself has abnormal communication. i An interrupt flag is set in the communication state of a distributed terminal communication message, and the communication message with the interrupt flag is sent outward; When the distributed terminal at the node directly connected to the substation has abnormal communication or receives a communication message with an interruption flag set, the undervoltage protection function is exited.

8. The automatic switching on / off system for voltage loss protection of distribution network according to claim 7, characterized in that: The system also includes a system update module, which is used to synchronously increase or decrease the distributed terminals in the distribution network system when the nodes in the distribution network system increase or decrease, restart the updated distributed terminals, relocate the nodes directly connected to the substation, and activate the undervoltage protection function.

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