CN116979492A - Single-shot cable network inner loop closed loop operation grid structure and self-healing method thereof - Google Patents

Abstract

The invention belongs to the field of network architecture, and specifically relates to a single-radiation cable network internal loop-loop operating network frame structure and a self-healing method thereof. The network frame structure includes a main line and four ring networks. The main line includes four main line ring network units, which are located at 1/5 at the end of the main line, 2/5 at the end of the main line, and 2/5 at the beginning of the main line. 5, 1/5 of the first end of the main line; the four main line ring network units and the inner ring branch ring network units respectively form four inner rings; the first circuit breaker (1) of the main line ring network unit is connected to the superior equipment , the second circuit breaker (2) is connected to the lower-level equipment; the invention proposes a distribution network closing mode in which ring network units communicate with the main line at different intervals to form a ring, forming a single-radiator cable network inner ring wiring network architecture, and supporting single-radiator network differential protection The self-healing solution integrated with the ring network longitudinal difference protection enables millisecond-level on-site self-healing of all line faults in the medium-voltage distribution network and rapid power restoration in non-faulty areas.

Description

A single-shot cable network inner loop operating grid structure and its self-healing method

Technical field

The invention belongs to the field of network architecture, and specifically relates to a single-radiation cable network inner loop operation network frame structure and a self-healing method thereof.

Background technique

With the continuous development of the power system, the focus of innovative technologies has gradually extended downwards. The demand for uninterrupted power supply by urban users has made the power supply reliability of the 10kV medium-voltage distribution network increasingly important. At present, Beijing's distribution network still adopts the "single-radiator network" power supply mode of "closed-loop design, open-loop operation" to solve the problem of load transfer when the distribution network lines operate abnormally. However, short-term power supply caused by switching operation still exists. Frequent power outages cannot meet the important load demands in the core area of the city.

Distribution automation uses automation devices or systems to monitor the operating status of the distribution network. It plays a core role in the field of self-healing of the current distribution network and plays an irreplaceable role in fault location, isolation and restoration of power supply in non-faulty areas. At this stage, Beijing’s distribution network protection self-healing model is mainly “differential + main station centralized”. Restricted by the 500ms fault isolation time limit of the substation outlet switch and the inherent action time of the line switch, traditional distribution networks mostly adopt the "substation outlet-large branch line-user" secondary protection level difference configuration mode. After the upstream switch in the fault area trips, the main station collects line terminals Report fault information, carry out analysis and judgment of fault areas, and complete fault isolation and load transfer through automatic remote control or manual means. However, due to factors such as the manufacturing process of switchgear, the different life spans of primary and secondary equipment, and the loose installation process of CT and other collection units, the centralized self-healing strategy of the master station often fails due to inaccurate judgment of the fault interval, causing the line circuit breaker protection interval to further expand. Expansion, fault interval isolation and other problems such as more customers.

Contents of the invention

The present invention proposes a single-shot cable network inner loop operation network frame structure and its self-healing method to solve the problem that the master station centralized self-healing strategy in the prior art often fails due to inaccurate fault interval judgment and easily causes line disconnection. The issue of further expansion of the device protection zone.

In order to achieve the above objects, the present invention proposes the following technical solutions:

A single-shot cable network inner loop closed loop operation network frame structure, including a main line and a number of inner loop branch ring network units. The main line includes four main line ring network units, which are located at 1/5 of the end of the main line. 2/5 at the end of the main line, 2/5 at the first end of the main line, 1/5 at the first end of the main line;

The trunk ring network units at the end 1/5 of the trunk line, the end 2/5 of the trunk line, the first end of the trunk line 2/5, and the first end 1/5 of the trunk line are connected to several inner ring branch ring network units respectively. , forming four inner rings;

The main line ring network unit and the inner ring branch ring network unit each include a first circuit breaker, a second circuit breaker, a third circuit breaker and a fourth circuit breaker;

Among them, the first circuit breaker of the main line ring network unit is connected to the upper-level equipment, and the second circuit breaker is connected to the lower-level equipment;

In a ring network, the third circuit breaker of the main line ring network unit is connected to the first circuit breaker of the inner ring branch at the beginning of the ring network, and the fourth circuit breaker of the main line ring network unit is connected to the inner ring branch at the end of the inner ring. The second circuit breaker of the ring network unit, the inner ring branch ring network units on the inner ring are connected through the first circuit breaker and the second circuit breaker, wherein the first circuit breaker of the inner ring branch ring network unit is connected to the previous one. The second circuit breaker of the inner ring branch ring network unit on the inner ring of one stage is connected to the first circuit breaker of the inner ring branch ring network unit on the inner ring of the next level.

Preferably, the main line ring network unit and the inner ring branch ring network unit are magnetically controlled circuit breaker type ring network units.

Preferably, a ring network unit is configured at the end 1/5 of the feeder trunk line and the t1 action delay is set;

Configure the ring network unit at the end 2/5 of the feeder trunk line and set the t2 action delay;

Configure the ring network unit at the head end 2/5 of the feeder trunk line and set the t3 action delay;

Configure the ring network unit at the first 1/5 of the feeder trunk line and set the t4 action delay;

Said t1<t2<t3<t4.

Preferably, the t1, t2, t3 and t4 are set to 100ms, 200ms, 300ms and 400ms respectively.

Preferably, the main line adopts the centralized self-healing mode of the main station based on 5-level 100ms differential protection.

Preferably, the main line ring network unit and the inner ring branch ring network unit are equipped with distributed DTU modules.

Preferably, the main line ring network unit and the inner ring branch ring network unit are equipped with network switches to realize the GOOSE information exchange of the circuit breakers in the cabinet;

Signal transmission occurs between each inner ring branch ring network unit through optical fiber channels;

The circuit breakers inside the main line ring network unit and the inner ring branch ring network unit are based on the IEC61850 protocol for GOOSE information exchange.

A self-healing method for a single-shot cable network inner loop closed loop operation network frame structure. When a fault occurs somewhere between the inner loop branch ring network units on the network frame structure, the fault is located on the upper level inner loop branch. The second circuit breaker of the ring network unit and the first circuit breaker of the next-level inner ring branch ring network unit at the fault location trip through the longitudinal differential protection action;

When the inner ring branch ring network unit fails, the first circuit breaker on the faulty inner ring branch ring network unit detects a fault signal, and the remaining circuit breakers do not detect the fault signal. The first circuit breaker sends a fault signal to the remaining circuit breakers inside the faulty inner loop branch ring network unit through GOOSE communication, and all internal circuit breakers of the faulty inner loop branch ring network unit trip;

When the user branch line of the inner ring branch ring network unit fails, the user demarcation circuit breaker in the inner ring branch ring network unit trips due to the overcurrent protection action, completing local isolation of the fault;

When a fault occurs between the main line ring network units, the second circuit breaker of the main line ring network unit at the upper level of the fault point detects the fault and performs an action trip according to its own action delay. After the fault point is detected, the next level circuit breaker The trip isolates the fault locally, and the contact circuit breaker located at the end of the main line operates and closes to restore power to the non-fault area;

When the user branch line of the main line ring network unit fails, the user boundary circuit breaker of the main line ring network unit trips due to the overcurrent protection action, completing local isolation of the fault;

When the busbar of the main line ring network unit on the inner ring fails, the first circuit breaker of the faulty main line ring network unit detects a fault signal, and the remaining circuit breakers do not detect the fault signal. All circuit breakers of the main line ring network unit operate and trip. The contact circuit breaker on the inner ring where the failed main line ring network unit is located closes to restore power to the non-faulty area;

Preferably, when the main line fails, the master station centralized self-healing mode is adopted.

Preferably, when a fault occurs inside the inner ring, distributed self-healing is performed relying on the distributed DTU module inside the ring network unit.

The benefits of the present invention are:

It proposes a distribution network closing mode in which ring network units communicate with busbars at different intervals to form a ring, forming a ring wiring network structure within a single-radiator cable network. It also proposes a self-healing solution that integrates the single-radiator network step difference protection and the ring network vertical difference protection to achieve The medium-voltage distribution network can perform on-site self-healing within milliseconds for all line faults and quickly restore power to non-faulty areas.

Relying on the quick-acting magnetic circuit breaker to promote the upgrade of the distribution network protection self-healing mode, the 500ms action delay of the substation outgoing switch can be achieved without changing the 500ms action delay of the distribution line. By promoting the meshing and segmentation of the long-distance cable network Upgrade to significantly improve line fault isolation and location capabilities and improve distribution network reliability.

The single-radiation cable network inner ring wiring mode is fully upgraded based on the current urban distribution network architecture. The main line is equipped with 4 magnetic circuit breaker type ring network units, and up to 4 inner rings can be constructed with the same feeder. Each inner ring line is equipped with at least 3 It has a magnetically controlled circuit breaker type ring network unit, and the number of other equipment can be flexibly configured according to actual needs and current architecture, and has good practicality and implementability.

Description of the drawings

The description and drawings that constitute a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached picture:

Figure 1 is a schematic structural diagram of a single-shot cable network inner loop operation network frame;

Figure 2 is a reference diagram of the case implementation.

In the figure, 1 is the first circuit breaker, 2 is the second circuit breaker, 3 is the third circuit breaker, 4 is the fourth circuit breaker, 11 is the ring network unit No. 1, 12 is the ring network unit No. 2, and 13 is the ring network unit No. 3. Number ring network unit.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

The following detailed description is an exemplary description and is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meanings as commonly understood by those of ordinary skill in the art to which this invention belongs. The terminology used in the present invention is for the purpose of describing specific embodiments only and is not intended to limit the exemplary embodiments according to the present invention.

Example 1:

Referring to Figure 1, the present invention provides a network frame structure for loop operation in a single-radiation cable network. The specific structure is: the main feeder line includes four main line ring network units, each located at the end of the feeder main line 1/5 2/5 at the end of the feeder main line, 2/5 at the first end of the feeder main line, and 1/5 at the first end of the feeder main line; a contact point is configured at the end of the main line and each inner ring to form a "five-point" Section, five contacts” grid.

The main line ring network unit and the inner ring branch ring network unit include a first circuit breaker 1, a second circuit breaker 2, a third circuit breaker 3 and a fourth circuit breaker 4, in which the ring network units on the feeder main line are all The first circuit breaker is connected to the upper-level equipment, and the second circuit breaker is connected to the lower-level equipment.

The main line ring network unit whose feeder is located at 1/5 of the end of the main line, 2/5 of the end of the feeder main line, 2/5 of the first end of the feeder main line, and 1/5 of the first end of the feeder main line is based on the third circuit breaker. 3 and the fourth circuit breaker 4 establish an inner loop. The inner loop includes a main line ring network unit and multiple inner loop branch ring network units. The specific structure is:

The third circuit breaker 3 of the main line ring network unit is connected to the first circuit breaker 1 of the inner ring branch at the head end of the inner ring, and the fourth circuit breaker 4 of the main line ring network unit is connected to the inner ring branch at the end of the inner ring. The second circuit breaker 2 of the ring network unit and the inner ring branch ring network units are connected through the first circuit breaker 1 and the second circuit breaker 2, where the first circuit breaker 1 is connected to the upper level inner ring branch ring of the inner ring. The second circuit breaker 2 of the network unit is connected to the first circuit breaker 1 of the inner ring branch ring network unit at the next level of the inner ring.

The number of inner ring branch ring network units on an inner ring is greater than or equal to 2.

There is no delay in the ring network unit at the end of the feeder main line;

Configure the ring network unit at the end 1/5 of the feeder trunk line and set the t1 action delay;

Configure the ring network unit at the end 2/5 of the feeder trunk line and set the t2 action delay;

Configure the ring network unit at the head end 2/5 of the feeder trunk line and set the t3 action delay;

A ring network unit is configured at the first 1/5 of the feeder trunk line and the t4 action delay is set.

When t1＜t2＜t3＜t4, the protection level difference of the single-shot main line increases step by step, and the fault range is determined based on the protection action information; in implementation, t1, t2, t3 and t4 can be set to 100ms, 200ms, 300ms and 400ms respectively. .

The circuit breaker inside the ring network unit transmits information through GOOSE.

The connection between the main feeder line and the inner ring is defined as the exit node. The ring network unit of the feeder main line is located at the exit node. Optical fibers are laid between the ring network units. When a fault occurs, the circuit breakers at both ends of the fault point act instantaneously to complete the isolation.

The ring network unit is configured with a network switch to realize GOOSE information exchange within the cabinet. Based on the IEC61850 protocol, optical fiber channels are used for signal transmission between the ring network units on the inner ring.

The ring network unit is a magnetic circuit breaker type ring network unit.

The ring network unit has a built-in distributed DTU module.

According to the actual situation, the main line can also be configured with standby or loop-out ring network units for high-voltage users or other branch lines.

When the main line fails, the master station centralized self-healing mode is adopted.

When a fault occurs inside the inner ring, distributed self-healing is performed relying on the distributed DTU module inside the ring network unit.

Example 2:

A self-healing method of a single-shot cable network internal loop-loop operating grid structure, based on the single-shot cable network internal loop-loop operating grid structure described in Embodiment 1, specifically including:

When a fault occurs somewhere between the inner ring branch ring network units on the grid structure, the second circuit breaker 2 of the upper level inner ring branch ring network unit at the fault location and the lower level inner loop branch at the fault location The first circuit breaker of the loop network unit trips through the longitudinal differential protection action;

When the inner loop branch ring network unit fails and the first circuit breaker 1 on the faulty inner loop branch ring network unit detects a fault signal but the remaining circuit breakers do not detect the fault signal, the faulty inner loop branch ring network unit The first circuit breaker 1 on the machine sends a fault signal to the remaining circuit breakers inside the faulty inner loop branch ring network unit through GOOSE communication, and all internal circuit breakers of the faulty inner loop branch ring network unit trip;

When the user branch line of the inner ring branch ring network unit fails, the user boundary circuit breaker overcurrent protection trips to complete the fault local isolation;

When a fault occurs between the main line ring network units, the second circuit breaker 2 of the main line ring network unit at the upper level of the fault point detects the fault and performs an action trip according to its own action delay. The circuit breaker at the next level of the fault point detects the fault. After tripping, the fault is isolated locally, and the terminal contact circuit breaker is closed to complete the restoration of power to the non-fault area;

When the user branch line of the ring network unit on the main trunk fails, the user demarcation circuit breaker overcurrent protection trips and completes local fault isolation;

When the busbar of the main line ring network unit participating in the inner ring fails, and the first circuit breaker 1 of the faulty main line ring network unit detects a fault signal but other circuit breakers do not detect the fault signal, all circuit breakers of the ring network unit Action tripping, the contact circuit breaker on the inner ring where the faulty main line ring network unit is located closes to complete the restoration of power to the non-faulty area;

When the main line fails, the master station centralized self-healing mode is adopted.

When a fault occurs within the inner ring, the distributed DTU module pair inside the ring network unit is relied upon for distributed self-healing.

Specifically, according to Figure 2, the No. 1 ring network unit 11 is the fourth-level differential equipment of the main line. The outlet switch CB4 is set with an action delay of 200ms. Its internal partition circuit breaker CB2 and circuit breaker CB3 are used to construct the inner ring wiring, and the inner ring configuration For 3 ring network equipment, only the ring incoming and outgoing distances are shown, and the remaining outgoing line loads are not shown separately.

Ring network unit 12 is the main line end equipment.

The No. 3 ring network unit 13 is other line terminal equipment, the circuit breaker CB7 and the circuit breaker CB8 are the contact switches, the circuit breaker CB7 is in the closing state, and the circuit breaker CB8 is in the opening state. Circuit breaker CB15 is a contact switch, which is in the open state and does not reflect the opposite line. The case proposes 6 different types of faults, named K1-K6 in sequence.

When point K1 fails, switches CB10 and CB11 trip through the longitudinal differential protection action, isolate the fault interval to complete self-healing, and upload the action signal to the master station.

When point K2 fails, switch CB11 detects a fault signal but switches CB12-CB14 do not detect a fault signal. Switch CB11 sends a fault signal to switches CB12-CB14 through GOOSE communication, and thus determines the fault point of the second device in the inner loop. At the busbar, the switches CB11-CB14 trip, complete fault isolation and self-healing, and upload the protection signal to the main station.

When point K3 fails, the user boundary switch CB13 detects the fault, and the over-current protection trips, completing local fault isolation and uploading the protection signal to the master station.

When point K4 fails, switch CB4 detects a short-circuit fault and delays 100ms to trip. The master station performs fault analysis and self-healing. Switch CB5 trips after receiving the action signal and isolates the fault locally. Contact switch CB8 receives the action signal. Closing completes the restoration of power to the non-fault area.

When the K5 point fails, the user boundary switch CB6 detects the fault, and the over-current protection trips, completing local fault isolation and uploading the protection signal to the master station.

When point K6 fails, switch CB1 detects a fault signal but switches CB2-CB4 do not detect a fault signal. Switch CB1 sends a fault signal to switches CB2-CB4 through GOOSE communication, and thus determines that the fault point is the busbar of ring network unit 1. , so the switches CB1-CB4 trip, complete the fault isolation, and upload the protection signal to the master station. Switch CB15 receives the action signal and closes to complete self-healing.

Reference cases are combined with the accompanying drawings to illustrate the present invention. Due to space limitations, only some lines are used as professional reference examples to facilitate understanding of the logic of feeder automation and self-healing solutions. In the field, the current grid characteristics can be used without changing the purpose of the present invention. Flexible application.

It is known from common technical knowledge that the present invention can be implemented by other embodiments without departing from its spirit or essential characteristics. Therefore, the above-disclosed embodiments are in all respects illustrative and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each process and/or block in the flowchart illustrations and/or block diagrams, and combinations of processes and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a use A device for realizing the functions specified in one process or multiple processes of the flowchart and/or one block or multiple blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory that causes a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including the instruction means, the instructions The device implements the functions specified in a process or processes of the flowchart and/or a block or blocks of the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device, causing a series of operating steps to be performed on the computer or other programmable device to produce computer-implemented processing, thereby executing on the computer or other programmable device. Instructions provide steps for implementing the functions specified in a process or processes of a flowchart diagram and/or a block or blocks of a block diagram.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified. Modifications or equivalent substitutions may be made to the specific embodiments, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the invention shall be covered by the scope of the claims of the invention.

Claims (10)

1. A single-shot cable network inner loop closed loop operation network frame structure, which is characterized in that it includes a main line and a number of inner loop branch ring network units. The main line includes four main line ring network units, respectively located on the main line. 1/5 at the end, 2/5 at the end of the main line, 2/5 at the first end of the main line, 1/5 at the first end of the main line; The trunk ring network units at the end 1/5 of the trunk line, the end 2/5 of the trunk line, the first end of the trunk line 2/5, and the first end 1/5 of the trunk line are connected to several inner ring branch ring network units respectively. , forming four inner rings; The main line ring network unit and the inner ring branch ring network unit each include a first circuit breaker (1), a second circuit breaker (2), a third circuit breaker (3) and a fourth circuit breaker (4); Among them, the first circuit breaker (1) of the main line ring network unit is connected to the upper-level equipment, and the second circuit breaker (2) is connected to the lower-level equipment; In a ring network, the third circuit breaker (3) of the main line ring network unit is connected to the first circuit breaker (1) of the inner ring branch ring network unit at the first end of the ring network, and the fourth circuit breaker (3) of the main line ring network unit is connected to 4) Connect the second circuit breaker (2) to the inner ring branch ring network unit at the end of the inner ring. The inner ring branch ring network units on the inner ring are connected through the first circuit breaker (1) and the second circuit breaker (2). connection, in which the first circuit breaker (1) of the inner ring branch ring network unit is connected to the second circuit breaker (2) of the inner ring branch ring network unit on the upper inner ring, and the third circuit breaker (2) of the inner ring branch ring network unit is connected. The second circuit breaker (2) is connected to the first circuit breaker (1) of the inner ring branch ring network unit on the next inner ring. 2. A single-radiation cable network inner loop closed loop operation network frame structure as claimed in claim 1, characterized in that the main trunk line ring network unit and the inner loop branch ring network unit are both magnetically controlled circuit breaker types. Ring network unit. 3. A network frame structure for loop operation in a single-shot cable network as claimed in claim 1, characterized in that a ring network unit is configured at the end 1/5 of the feeder trunk line and the t1 action delay is set; Configure the ring network unit at the end 2/5 of the feeder trunk line and set the t2 action delay; Configure the ring network unit at the head end 2/5 of the feeder trunk line and set the t3 action delay; Configure the ring network unit at the first 1/5 of the feeder trunk line and set the t4 action delay; Said t1<t2<t3<t4. 4. A network frame structure for single-radiation cable network internal loop operation as claimed in claim 3, characterized in that the t1, t2, t3 and t4 are respectively set to 100ms, 200ms, 300ms and 400ms. 5. A network frame structure for loop operation in a single-radiation cable network as claimed in claim 4, characterized in that the main line adopts a master station centralized self-healing mode based on 5-level 100ms differential protection. 6. A single-radiation cable network inner loop closed loop operation network frame structure as claimed in claim 1, characterized in that distributed DTU modules are provided inside the main trunk ring network unit and the inner loop branch ring network unit. 7. A single-radiation cable network inner ring closed ring operation network frame structure as claimed in claim 1, characterized in that network switches are configured inside the main trunk ring network unit and the inner ring branch ring network unit to achieve in-cabinet circuit breaking. GOOSE information interaction of the device; Signal transmission occurs between each inner ring branch ring network unit through optical fiber channels; The circuit breakers inside the main line ring network unit and the inner ring branch ring network unit are based on the IEC61850 protocol for GOOSE information exchange. 8. A self-healing method for a single-shot cable network internal loop closed loop operation grid structure, based on a single-shoot cable network internal loop closed loop operation grid structure according to any one of claims 1 to 7, and its characteristics lies in: When a fault occurs somewhere between the inner loop branch ring network units on the grid structure, the second circuit breaker (2) of the inner loop branch ring network unit at the upper level of the fault and the inner loop branch ring network unit at the lower level of the fault are The first circuit breaker of the ring branch ring network unit trips through the longitudinal differential protection action; When the inner loop branch ring network unit fails, the first circuit breaker (1) on the faulty inner loop branch ring network unit detects a fault signal, but the remaining circuit breakers do not detect the fault signal, and the faulty inner loop branch ring network unit The first circuit breaker (1) on the unit sends a fault signal to the remaining circuit breakers inside the faulty inner loop branch ring network unit through GOOSE communication, and all internal circuit breakers of the faulty inner loop branch ring network unit trip; When the user branch line of the inner ring branch ring network unit fails, the user demarcation circuit breaker in the inner ring branch ring network unit trips due to the overcurrent protection action, completing local isolation of the fault; When a fault occurs between the main line ring network units, the second circuit breaker (2) of the main line ring network unit on the upper level of the fault point detects the fault and performs an action trip according to its own action delay. The circuit breaker on the next level of the fault point detects the fault. After the fault occurs, it trips to isolate the fault locally, and the contact circuit breaker located at the end of the main line acts and closes to restore power to the non-fault area; When the user branch line of the main line ring network unit fails, the user boundary circuit breaker of the main line ring network unit trips due to the overcurrent protection action, completing local isolation of the fault; When the busbar of the main line ring network unit on the inner ring fails, the first circuit breaker (1) of the faulty main line ring network unit detects a fault signal, and the remaining circuit breakers do not detect the fault signal. All circuit breakers of the main line ring network unit The contact circuit breaker on the inner ring where the failed main line ring network unit is located closes to restore power to the non-faulty area. 9. A self-healing method for a single-radiation cable network's internal loop-loop operation grid structure as claimed in claim 8, characterized in that when the main line fails, the master station centralized self-healing mode is adopted. 10. A self-healing method for a single-shot cable network inner ring closed ring operation network frame structure as claimed in claim 8, characterized in that when a fault occurs inside the inner ring, it relies on the distributed DTU module inside the ring network unit. Distributed self-healing.