Multi-pole full-connection power transformation and distribution system structure and construction method thereof
By adopting a multi-pole fully connected structure in the transformer distribution system, the secondary outgoing line of the transformer is constructed into a multi-pole type, and a fully connected structure is established through the contact switch, which solves the low usage rate and low economic efficiency in the existing technology. Problem, high reliability and high load rate transformer distribution system is realized.
Patent Information
- Application Number
- CN202411782270.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2025-02-07
AI Technical Summary
The existing substation distribution system structure has low usage rate under normal operating conditions, resulting in low initial investment and later operation efficiency, and it is difficult to balance load safety and economy.
Using a multi-pole fully connected transformer distribution system structure, the transformer secondary outgoing line is constructed into a multi-pole type. Each multi-pole branch circuit of each transformer secondary outgoing main circuit is used as the incoming power supply to build a feed bus and pass The contact switch establishes a fully connected structure to form an N+1 or N+n network structure to ensure system redundancy and high load rate.
It improves equipment load rate and system reliability, reduces investment in total transformer capacity, improves operating efficiency, and provides flexible redundant choices to adapt to the needs of different scenarios.
Smart Images
Figure CN119401443A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of power supply and distribution, and in particular to a multi-pole fully connected power transformation and distribution system structure and a construction method thereof. Background Art
[0002] Clause 3.0.1 of Code for Design of Power Supply and Distribution System GB 50052-2009 states: "The high-voltage and low-voltage busbars of distribution stations and substations should adopt single busbar or segmented single busbar connection. When the power supply continuity requirements are very high, the high-voltage busbar can adopt segmented single busbar with bypass busbar or double busbar connection." It explains that there are five types of power distribution system structures that can be used at present, including single busbar, single busbar segmentation, single busbar segmentation with bypass, double busbar, and double busbar segmentation with bypass.
[0003] Article 3.2.5 of "35kV~110kV Substation Design Specifications" GB50059-2011 states: "When a substation is equipped with two or more main transformers, the 6kV~10kV electrical wiring should adopt single bus segmentation. The segmentation method should meet the requirement of load distribution for other main transformers when one of the main transformers is out of service." It explains that the currently available wiring methods include single bus segmentation and a substation and distribution system structure.
[0004] Clause 3.2.1 of GB 50053-2013 "Design Specifications for Substations 20kV and Below": "The high-voltage and low-voltage busbars of distribution stations and substations should adopt single busbar or segmented single busbar connection. When the power supply continuity requirements are very high, the high-voltage busbar can adopt segmented single busbar with bypass busbar or double busbar connection." It explains that there are five types of power distribution system structures that can be used at present, including single busbar, single busbar segmentation, single busbar segmentation with bypass, double busbar, and double busbar with bypass.
[0005] "Design Specifications for Substations 10kV and Below" GB50052-94-Clause 3.2.1: "The high-voltage and low-voltage busbars of distribution stations and substations should adopt single busbar or segmented single busbar connection. When the power supply continuity requirements are very high, the high-voltage busbar can adopt segmented single busbar with bypass busbar or double busbar connection." It explains that there are five types of power distribution system structures that can be used at present, including single busbar, single busbar segmentation, single busbar segmentation with bypass, double busbar, and double busbar with bypass.
[0006] The traditional power distribution system structure is:
[0007] 1) Single busbar;
[0008] 2) Single busbar segmentation;
[0009] 3) Single busbar section with bypass;
[0010] 4) Double busbar;
[0011] 5) Double busbar with bypass.
[0012] The advantages of the single busbar structure are simple structure and good economy, but the disadvantage is no redundancy; the advantages of the single busbar segmentation and single busbar segmentation with bypass structure are simple structure and redundant protection, but the disadvantage is poor flexibility; the advantages of the double busbar segmentation and double busbar with bypass structure are high reliability and flexibility, but the disadvantage is complex structure and poor economy. For important loads, single busbar segmentation, single busbar segmentation with bypass, double busbar, double busbar with bypass structure will be used to achieve redundant protection capability, but they all have a common disadvantage, that is, the utilization rate is the lowest under normal operating conditions, and the maximum can only reach 50%, which has the problem of low economy for both initial investment and later operating efficiency. Summary of the invention
[0013] The purpose of the present invention is to address the deficiencies of the above-mentioned technologies and provide a multi-pole fully connected power distribution system structure and its construction method, which has high reliability and good economy, especially for scenarios where there are balanced requirements for load safety and economy.
[0014] To achieve the above-mentioned purpose, the present invention involves a multi-pole fully connected power distribution system structure, in which the transformer secondary output is constructed into a multi-pole type, and the multi-pole can be 2, 3, 4, ..., n branch circuits. Each multi-pole branch circuit of the secondary output main circuit of each transformer is used as an incoming power supply to construct a feeder bus. The feeder bus constructed by each branch circuit under each transformer establishes a connection relationship with the feeder bus constructed by a branch circuit of the remaining networked transformers one by one, forming a fully connected structure between all transformers, and the feeder bus is connected to the lower-level load. The number of branches of the transformer secondary output multi-pole type is equal to the total number of networked transformers minus 1. N transformers are networked to form N*(N-1) branch circuits and the same number of feeder buses. The multi-pole fully connected power distribution system structure has two structures: basic type and extended type. The basic structure of the multi-pole fully connected power distribution system is that each feeder bus is connected to a branch circuit of the secondary outgoing line of the transformer through an incoming line switch as the incoming power supply of the feeder bus, and is connected to a feeder bus that is not connected to the secondary outgoing line branch circuit of the transformer through a connecting switch as a connecting line. The feeder bus is connected to the load, and N transformers are networked to form N*(N-1) feeder buses to construct an N+1 networking structure, where N is the total number of networked transformers, and +1 is the capacity of redundant transformers. The N+1 networking structure allows any one of the networked transformers to exit operation, and the remaining transformers take over the power supply load of the out-of-operation transformer; the extended structure of the multi-pole fully connected power distribution system is that each A feeder bus is connected to a branch circuit of a transformer secondary outgoing line through an incoming line switch as a feeder bus incoming power supply, and is connected to a feeder bus connected to a branch circuit of a secondary outgoing line other than the transformer through a connecting switch as a connecting line. A feeder bus connected to a branch circuit of the transformer secondary outgoing line is connected to the feeder bus through a connecting switch as a connecting line. The feeder bus is connected to the load, and N transformers are networked to form N*(N-1) feeder buses to construct an N+n networking structure, where N is the total number of networked transformers, and +n is the capacity of redundant transformers. The N+n networking structure allows any n of the networked transformers to be out of operation at the same time, and the remaining transformers take over the power supply load of the transformers that have been out of operation.
[0015] The state of the feeder bus incoming line switch is determined by whether the incoming line connected to it is energized. When the incoming line power is energized, it is in the closed state, and when the incoming line power is not energized, it is in the open state.
[0016] The feeder busbar contact switch performs standby automatic switching through the live signal on the feeder busbar.
[0017] The connecting switches at both ends of the feeder busbar include at least one short-circuit switch and the other is a circuit breaker or an isolating switch.
[0018] The two incoming line switches and the connecting switch of the feeder busbars with a connecting relationship are provided with interlocking protection, and the switches shall not be in the closed state at the same time.
[0019] The operation method of the multi-pole fully connected power distribution system structure basic form includes the following working conditions:
[0020] 1) Under normal working conditions, the incoming power supply of the feeder bus is energized, the incoming switch is in the closed state, the tie switch is in the open state, and each feeder bus operates separately;
[0021] 2) When the incoming line connected to the feeder bus loses power, the incoming line switch of the lost power feeder bus is opened, and it is detected that the lost power feeder bus is not energized and there is no protection action locking signal, and it is detected whether the feeder bus that is in a communication relationship with the lost power feeder bus is energized. If the feeder bus that is in a communication relationship with it is energized, the connecting switch of the feeder bus is closed, and the load of the lost power feeder bus is transferred to other transformers in the network through the connecting line.
[0022] The operation method of the multi-pole fully connected power distribution system structure expansion mode includes the following working conditions:
[0023] 1) Under normal working conditions, the incoming power supply of the feeder bus is energized, the incoming switch is in the closed state, the tie switch is in the open state, and each feeder bus operates separately;
[0024] 2) When the incoming line connected to the feeder bus loses power, the incoming line switch of the lost power feeder bus is opened, and it is detected that the lost power feeder bus is not energized and there is no protection action locking signal, and it is detected whether the feeder bus connected to the secondary outgoing line branch circuit of the transformer that is in a communication relationship with the lost power feeder bus is energized. If the feeder bus connected to the secondary outgoing line branch circuit of the transformer that is in a communication relationship with the lost power feeder bus is energized, the connecting switch between the lost power feeder bus and the feeder bus connected to the secondary outgoing line branch circuit of the transformer that is in a communication relationship with the lost power feeder bus is closed, and the lost power feeder bus and the feeder bus connected to the secondary outgoing line branch circuit of the transformer that is in a communication relationship with the lost power feeder bus are in a communication state, and other connecting switches of the lost power feeder bus are in an open state, and the load of the lost power bus is transferred to other branch circuits of the transformer outgoing line.
[0025] 3) When the incoming line connected to the feeder bus loses power, the incoming line switch of the lost power feeder bus opens, detects whether the lost power feeder bus is not energized and has no protection action locking signal, detects whether the feeder bus connected to the secondary outgoing line branch circuit of the transformer in contact with the lost power feeder bus is energized, if the feeder bus connected to the secondary outgoing line branch circuit of the transformer in contact with the lost power feeder bus is not energized, then detects whether the feeder bus connected to the secondary outgoing line branch circuit of the non-transformer in contact with the lost power feeder bus is energized, if If the feeder bus connected to the secondary outgoing branch circuit of the non-transformer that is in communication with the lost power feeder bus is energized, the connecting switch between the lost power feeder bus and the feeder bus connected to the secondary outgoing branch circuit of the non-transformer that is in communication with the lost power feeder bus is closed, the lost power feeder bus and the feeder bus connected to the secondary outgoing branch circuit of the non-transformer that is in communication with the lost power feeder bus are in a communication state, other connecting switches of the lost power feeder bus are in an open state, and the load of the lost power bus is transferred to the non-transformer.
[0026] The multi-pole fully connected power distribution system structure and its extended form can select different numbers of networked transformers and redundant numbers according to needs, and the equipment load rates of different system architectures are different. The basic form of the multi-pole fully connected power distribution system structure is preferred to maximize the advantages of improving the equipment load rate. The equipment load efficiency refers to the ratio of the load allowed to be carried by the transformer under normal operating conditions to the rated load of the transformer.
[0027] Table 1 describes the multi-pole fully connected power distribution system structure and its extended form. Equipment load rate data of different system architectures:
[0028]
[0029] Compared with the prior art, the present invention has the following advantages:
[0030] 1) Through the multi-pole structure of the transformer secondary output line and the fully connected structure between the secondary of the networked transformer, the equipment load rate under normal working conditions is improved on the basis of ensuring system redundancy. For the early construction stage, the investment in the total capacity of the transformer can be reduced when the available transformer capacity is the same; for the later operation stage, the high load rate can improve the operating efficiency of the transformer. Compared with the existing technology, the present invention improves the economic efficiency.
[0031] 2) Through the transformer secondary outgoing multi-pole structure and the fully connected structure between the secondary of the networking transformer, different system redundancy capabilities such as N+1, N+2, ..., N+n can be selected to adapt to different scene requirements. Compared with the prior art, the present invention improves flexibility.
[0032] 3) Through the multi-pole structure of the transformer secondary output line and the fully connected structure between the secondary of the networked transformer, a transformer pool group structure is formed, and the transformers in the pool group are all in a peer relationship. Each transformer is a redundant backup of all transformers and also has a redundant backup of all other transformers. Compared with the prior art, the present invention improves reliability. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 This is a system diagram of the multi-pole fully connected power distribution system structure of the present invention, with a total number of transformers being 4 and a redundant capacity number being 1.
[0034] like Figure 1 As shown, the total number of transformers is 4, of which the redundant transformer capacity is 1. The secondary outgoing lines of transformers T1, T2, T3, and T4 adopt a three-pole branch circuit structure, which are respectively connected to 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B, and 3C branch circuits, and are respectively connected to the feeder busbars M1A, M1B, M1C, M2A, M2B, M2C, M3A, M3B, and M3C through the incoming line switches Q1A, Q1B, Q1C, Q2A, Q2B, Q2C, Q3A, Q3B, and Q3C, and the feeder busbars are connected to loads. An M1C-M2A interconnection line is connected between the feed bus M1C and the feed bus M2A, and an interconnection switch Q1C2A is provided; an M1B-M3B interconnection line is connected between the feed bus M1B and the feed bus M3B, and an interconnection switch Q1B3B is provided; an M2B-M4B interconnection line is connected between the feed bus M2B and the feed bus M4B, and an interconnection switch Q2B4B is provided; an M2C-M3A interconnection line is connected between the feed bus M2C and the feed bus M3A, and an interconnection switch Q2C3A is provided; an M3C-M4A interconnection line is connected between the feed bus M3C and the feed bus M4A, and an interconnection switch Q3C4A is provided; an M4C-M1A interconnection line is connected between the feed bus M4C and the feed bus M1A, and an interconnection switch Q4C1A is provided.
[0035] like Figure 1 As shown, the status of the feeder bus incoming line switches Q1A, Q1B, Q1C, Q2A, Q2B, Q2C, Q3A, Q3B, Q3C is determined by whether the incoming line is energized. When in normal operation, transformers T1, T2, T3, T4 are operating normally, the transformer secondary is energized, the feeder bus incoming line switches Q1A, Q1B, Q1C, Q2A, Q2B, Q2C, Q3A, Q3B, Q3C are in the closed state, and the tie switches Q1C2A, Q1B3B, Q2B4B, Q2C3A, Q3C4A, Q4C1A are in the open state, and each feeder bus operates separately.
[0036] like Figure 1As shown, when transformer T1 fails and stops running, transformers T2, T3, and T4 run normally, feeder bus incoming switches Q1A, Q1B, and Q1C are disconnected, and tie switches Q4C1A, Q1B2B, and Q1C2A are closed, the M4C-M1A tie line is connected, and feeder bus M4C and feeder bus M1A run in parallel, the M1B-M3B tie line is connected, and feeder bus M1B and feeder bus M3B run in parallel, and the M1C-M2A tie line is connected, and feeder bus M1C and feeder bus M2A run in parallel Operation; When transformer T2 fails and stops operating, transformers T1, T3, and T4 operate normally, feeder bus incoming switches Q2A, Q2B, and Q2C are disconnected, tie switches Q1C2A, Q2B4B, and Q2C3A are closed, M1C-M2A tie line is connected, feeder bus M1C and feeder bus M2A operate in parallel, M2B-M4B tie line is connected, feeder bus M2B and feeder bus M4B operate in parallel, M2C-M3A tie line is connected, feeder bus M2C and feeder bus M3A operate in parallel When transformer T3 fails and stops running, transformers T1, T2, and T4 run normally, feeder bus incoming switches Q3A, Q3B, and Q3C are disconnected, tie switches Q2C3A, Q1B3B, and Q3C4A are closed, M2C-M3A tie line is connected, feeder bus M2C and feeder bus M3A run in parallel, M1B-M3B tie line is connected, feeder bus M1B and feeder bus M3B run in parallel, M3C-M4A tie line is connected, feeder bus M3C and feeder bus M4A run in parallel ; When transformer T4 fails and stops operating, transformers T1, T2 and T3 operate normally, the feeder bus incoming switches Q4A, Q4B and Q4C are disconnected, the contact switches Q3C4A, Q2B4B and Q4C1A are closed, the M3C-M4A contact line is connected, the feeder bus M3C and the feeder bus M4A operate in parallel, the M2B-M4B contact line is connected, the feeder bus M2B and the feeder bus M4B operate in parallel, the M4C-M1A contact line is connected, and the feeder bus M4C and the feeder bus M1A operate in parallel.
[0037] Figure 2 This is a system diagram of a multi-pole fully connected power distribution system structure of the present invention, in which the total number of transformers is N and the number of redundant capacity is 1.
[0038] like Figure 2As shown, the multi-pole fully connected power distribution system structure of the present invention can be extended to N transformers for networking. The secondary outgoing lines of transformers T1, T2, T3, ..., TN adopt an N-1 pole branch loop structure, and 1A, 1B, ..., 1X, 2A, 2B, ..., 2X, 3A, 3B, ..., 3X, ..., NA, NB, ..., NX branch loops are respectively connected, and feeding busbars M1A, M1B, ..., M1X, M2A, M2B, ..., M2X, M3A, M3B, ..., M3X, ..., MNX are respectively connected through incoming line switches Q1A, Q1B, ..., Q1X, Q2A, Q2B, ..., Q2X, Q3A, Q3B, ..., Q3X, ..., QNX, and the feeding busbars are connected to loads. The feeding busbars of each transformer branch loop are connected to the branch loop feeding busbars of the remaining transformers in the network by connecting lines.
[0039] Figure 3 This is a system diagram of the structure expansion type of the multi-pole fully connected power distribution system of the present invention, with a total number of 5 transformers and 2 redundant capacities.
[0040] like Figure 3As shown, the total number of transformers is 5, of which the redundant transformer capacity is 2. The secondary outgoing lines of transformers T1, T2, T3, T4, and T5 adopt a four-pole branch circuit structure, and are respectively connected to 1A, 1B, 1C, 1D, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, 4A, 4B, 4C, 4D, 5A, 5B, 5C, and 5D branch circuits, respectively through the incoming line switches Q1A, Q1B, Q1C, Q1D, Q2A, Q2B, Q2C, Q2D, and Q3 A, Q3B, Q3C, Q3D, Q4A, Q4B, Q4C, Q4D, Q5A, Q5B, Q5C, Q5D are connected to the feeding bus M1A, M1B, M1C, M1D, M2A, M2B, M2C, M2D, M3A, M3B, M3C, M3D, M4A, M4B, M4C, M4D, M5A, M5B, M5C, M5D, and the feeding bus is connected to the load.The feed bus M1A and the feed bus M5D are connected by an M1A-M5D interconnection line, and an interconnection switch Q1A5D is provided; the feed bus M1B and the feed bus M4B are connected by an M1B-M4B interconnection line, and an interconnection switch Q1B4B is provided; the feed bus M1C and the feed bus M3C are connected by an M1C-M3C interconnection line, and an interconnection switch Q1C3C is provided; the feed bus M1D and the feed bus M2A are connected by an M1D-M2A interconnection line, and an interconnection switch Q1D2A is provided; the feed bus M2B and the feed bus M4C are connected by an M2B-M4C interconnection line, and an interconnection switch Q2B4C is provided ; The feed bus M2C and the feed bus M5C are connected by an M2C-M5C interconnection line, and a interconnection switch Q2C5C is provided; the feed bus M2D and the feed bus M3A are connected by an M2D-M3A interconnection line, and a interconnection switch Q2D3A is provided; the feed bus M3B and the feed bus M4A are connected by an M3B-M4A interconnection line, and a interconnection switch Q3B4A is provided; the feed bus M3D and the feed bus M5B are connected by an M3D-M5B interconnection line, and a interconnection switch Q3D5B is provided; the feed bus M4D and the feed bus M5A are connected by an M4D-M5A interconnection line, and a interconnection switch Q4D5 A; the feeder busbar M1A and the feeder busbar M1B are connected with an M1A-M1B tie line, and a tie switch Q1A1B is provided; the feeder busbar M1C and the feeder busbar M1D are connected with an M1C-M1D tie line, and a tie switch Q1C1D is provided; the feeder busbar M2A and the feeder busbar are connected with an M2A-M2B tie line, and a tie switch Q2A2B is provided; the feeder busbar M2C and the feeder busbar M2D are connected with an M2C-M2D tie line, and a tie switch Q2C2D is provided; the feeder busbar M3A and the feeder busbar M3B are connected with an M3A-M3B tie line, and a tie switch Q3A3B is provided; An M3C-M3D interconnection line is connected between the feeder bus M3C and the feeder bus M3D, and a interconnection switch Q3C3D is provided; an M4A-M4B interconnection line is connected between the feeder bus M4A and the feeder bus M4B, and a interconnection switch Q4A4B is provided; an M4C-M4D interconnection line is connected between the feeder bus M4C and the feeder bus M4D, and a interconnection switch Q4C4D is provided; an M5A-M5B interconnection line is connected between the feeder bus M5A and the feeder bus M5B, and a interconnection switch Q5A5B is provided; an M5C-M5D interconnection line is connected between the feeder bus M5C and the feeder bus M5D, and a interconnection switch Q5C5D is provided.
[0041] like Figure 3As shown, the status of the feeder bus incoming line switches Q1A, Q1B, Q1C, Q1D, Q2A, Q2B, Q2C, Q2D, Q3A, Q3B, Q3C, Q3D, Q4A, Q4B, Q4C, Q4D, Q5A, Q5B, Q5C, Q5D is determined by whether the incoming line is energized. When in normal operating conditions, transformers T1, T2, T3, T4, T5 are working normally, the transformer secondary is energized, and the feeder bus incoming line switches Q1A, Q1B, Q1C, Q1D, Q2A, Q2B, Q2C, Q2D, Q3A, Q3B, Q3C, Q3D, Q4A, Q4B, Q4C, Q4D, Q5A, Q5B, Q5C, Q5D are in the closed state, and the contactor Switches Q1A5D, Q1B4B, Q1C3C, Q1D2A, Q2B4C, Q2C5C, Q2D3A, Q3B4A, Q3D5B, Q4D5A, Q1A1B, Q1C1D, Q2A2B, Q2C2D, Q3A3B, Q3C3D, Q4A4B, Q4C4D, Q5A5B, and Q5C5D are in the open state, and each feeding bus operates separately.
[0042] Table 2 Figure 3 As shown in the figure, the status of the incoming switch and the connecting switch under abnormal operating conditions.
[0043]
[0044] Figure 4 This is a system diagram of the structure expansion type of the multi-pole fully connected power distribution system of the present invention, with a total number of N transformers and n redundant capacities.
[0045] like Figure 4 As shown, the multi-pole fully connected power distribution system structure expansion type of the present invention can set N transformers for networking, and the number of redundant capacities can be set to 1 to n, thereby realizing a power distribution system architecture with different numbers of transformers and different redundancy capabilities.
Claims
1. A multi-pole fully connected power distribution system structure, characterized by: The secondary of the transformer adopts a multi-pole structure, and the networked transformers are fully connected.
2. The multi-pole structure according to claim 1, characterized in that: The transformer secondary output line is constructed into a multi-pole type, and the multi-pole can be 2, 3, 4, ..., n branch circuits. Each multi-pole branch circuit of the secondary output main circuit of each transformer is used as the incoming power supply to construct a feeding bus.
3. The full connection form according to claim 1, characterized in that: The feeder busbars constructed by each circuit under each transformer establish a connection relationship with the feeder busbars constructed by a certain circuit under the remaining networked transformers one by one, forming a fully connected structure between all transformers.
4. The multi-pole fully connected power distribution system structure according to claim 1 is characterized in that: The multi-pole fully connected power distribution system has two structures: basic type and extended type.
5. The structural foundation of the multi-pole fully connected power distribution system according to claim 4 is characterized in that: Each feeder bus is connected to a branch circuit of the secondary outgoing line of a transformer through an incoming line switch as the incoming power supply of the feeder bus, and is connected to a feeder bus that is not connected to the secondary outgoing line branch circuit of the transformer through a connecting switch as a connecting line. The feeder bus is connected to the load, and N transformers are networked to form N*(N-1) feeder buses, constructing an N+1 networking structure, where N is the total number of networked transformers, and +1 is the capacity of redundant transformers. The N+1 networking structure allows any one of the networked transformers to exit operation, and the remaining transformers take over the power supply load of the transformer that has exited operation.
6. The multi-pole fully connected power distribution system structure expansion type according to claim 4 is characterized in that: Each feeder bus is connected to a branch circuit of the secondary outgoing line of the transformer through an incoming line switch as the incoming power supply of the feeder bus, and is connected to a feeder bus connected to a branch circuit of the secondary outgoing line of a transformer other than the transformer through a connecting switch as a connecting line. A feeder bus connected to a branch circuit of the secondary outgoing line of the transformer is connected to the feeder bus through a connecting switch as a connecting line. The feeder bus is connected to the load, and N transformers are networked to form N*(N-1) feeder buses to construct an N+n networking structure, where N is the total number of networked transformers, and +n is the capacity of redundant transformers. The N+n networking structure allows any n of the networked transformers to be out of operation at the same time, and the remaining transformers take over the power supply load of the transformers that have been out of operation.