A method for automatic switching of backup power in the power supply system of a large hydropower station with multiple generating units.

Abstract

This invention discloses a method for automatic transfer switching of power supply in a large-scale hydropower station with multiple generating units. The method includes backup power source I, backup power source II, backup power source III, a construction power source, six busbars, a main incoming line, a main incoming line circuit breaker 1DL, a circuit breaker, and a circuit breaker switch. The beneficial effects of this invention are that it allows for sequential testing and activation of the three automatic transfer switching methods when the generator is de-energized, enabling the backup power sources to charge and then discharge, ensuring that power supply is not interrupted for an extended period during generator outages. The availability of multiple backup power sources and automatic transfer switching methods guarantees continued power supply and prevents major power supply accidents.

Description

Technical Field

[0001] This invention relates to the field of automatic power supply backup switching technology, and in particular to a method for automatic power supply backup switching of a large hydropower station with multiple generating units. Background Technology

[0002] Currently, conventional automatic transfer switch (ATS) logic cannot meet the requirements of various operating modes, resulting in the inability to automatically switch to backup power after a busbar power failure. Furthermore, the existing ATS designs lack power supply diversity. They cannot guarantee the rapid activation of the ATS to restore system power after a busbar power failure within the power plant.

[0003] Existing automatic transfer switching methods are mostly used in distribution networks and substations, which have complex power supply networks, reliable power sources, diverse power sources, and good stability. However, for power generation systems, especially large hydropower stations, the plant auxiliary power system typically consists of multiple generators connected to a 10kV busbar. A drawback of this system is the lack of an external power source. When a generator or line fault within the power station causes a complete generator outage, the auxiliary power system collapses without external power, plunging the entire station into darkness and posing a significant safety hazard. To address this technical deficiency, this invention proposes an automatic transfer switching method for large hydropower stations with multiple generating units, combining on-site and off-site power supply. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a method for automatic backup power transfer in the power supply system of a large hydropower station with multiple generating units, which can reduce power supply accidents caused by generator shutdowns and avoid problems in activating backup power after generator failure through various automatic backup power transfer methods.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for automatic switching of the power supply system of a large hydropower station with multiple units, which includes a backup power supply I, a backup power supply II, a construction power supply, a busbar I, a busbar II, a busbar III, a main incoming line 1#, a main incoming line circuit breaker 1DL, a right sectional circuit breaker 2DL, a left sectional circuit breaker 4DL, and a construction power supply circuit breaker 5DL.

[0008] Obtain the charging status of backup power supply I, backup power supply II, and construction power supply. When a power supply is fully charged, the corresponding circuit breaker closes.

[0009] When backup power supply I is fully charged, start automatic transfer mode one.

[0010] When backup power supply II is fully charged, start automatic transfer mode II;

[0011] Once the construction power supply is fully charged, activate the third automatic transfer switch.

[0012] As a preferred embodiment of the automatic transfer method for the power supply system of a large hydropower station with multiple units as described in this invention, when in automatic transfer mode 1, after automatic transfer 1 is charged, the status of the busbar is determined. If the busbar is de-energized and there is no current in the No. 1 incoming line, the construction power supply, the right section 2DL, and the left section 4DL, then automatic transfer 1 is activated.

[0013] As a preferred embodiment of the automatic transfer switch method for the power supply system of a large hydropower station with multiple generating units as described in this invention, the method is as follows: When the automatic transfer switch I is started, all bus incoming line switches are tripped. At this time, the bus status is judged. If the bus is de-energized, it is judged whether the automatic transfer switch I meets the conditions required for the I backup power supply to be put into operation. If the I backup meets the conditions required for the I backup power supply to be put into operation, the right section 2DL circuit breaker is closed after a delay of the automatic transfer mode 1, and the I backup operation is completed. If the I backup does not meet the conditions required for the I backup power supply to be put into operation, or the I backup fails and the II backup meets the conditions required for the I backup power supply to be put into operation, and the right section 2DL is in the closed position, then a trip right section 2DL command is issued.

[0014] As a preferred embodiment of the automatic transfer method for the power supply system of a large hydropower station with multiple units as described in this invention, when in automatic transfer mode two, after automatic transfer mode II is charged, the status of main incoming line 1# is judged. If main incoming line 1# has voltage, automatic transfer mode II is activated.

[0015] As a preferred embodiment of the automatic transfer method for the power supply system of a large hydropower station with multiple units as described in this invention, when the automatic transfer of II is initiated and enters the trip delay period, 2DL, 5DL, and 4DL trip and the corresponding circuit breakers have no current. If there is no voltage on the bus, the No. 1 main incoming line circuit breaker 1DL closes. At this time, the equipment completes self-recovery and is powered by the No. 1 main incoming line.

[0016] As a preferred embodiment of the automatic transfer method for the power supply system of a large hydropower station with multiple units as described in this invention, wherein: when in automatic transfer mode three, automatic transfer III is fully charged, and automatic transfer I is not charged or neither automatic transfer I nor automatic transfer II meets the conditions required for the I backup power supply to be put into operation, if the busbar is de-energized, the construction incoming line is energized, the No. 1 main incoming line has no current, the construction power supply has no current, the right section 2DL has no current, and the left section 4DL has no current, then automatic transfer III is activated.

[0017] As a preferred embodiment of the automatic transfer method for the power supply system of a large hydropower station with multiple units as described in this invention, when the automatic transfer method III is started, if 2DL, 5DL, and 4DL all trip and the busbar is de-energized while the construction power supply is energized, then the construction power supply circuit breaker 5DL is closed after a delay via the automatic transfer method 3.

[0018] As a preferred embodiment of the multi-channel partial discharge detection device with anti-interference capability described in this invention, when the bus is energized and backup I or backup II meets the conditions for backup I power supply activation, backup I is fully charged after a backup self-activation charging time of 20 seconds.

[0019] When backup power supply I is fully charged, backup mode 2 or backup mode 3 is activated, or the high-voltage circuit breaker trips abnormally or the switch fails to trip. If backup power supply I fails and backup power supply II is not ready or 4DL is closed, or 2DL is closed and enters the charging time while the bus is energized, and both backup power supply I and backup power supply II meet the conditions required for backup power supply I and enter the delay period, and meet the automatic backup transfer conditions, then automatic backup transfer mode 1 charging begins.

[0020] As a preferred embodiment of the multi-channel partial discharge detection device with anti-interference capability described in this invention, when the three phases of the busbar are energized and the No. 1 incoming line 1DL is in the split position, the backup charging is completed after 20 seconds of automatic charging.

[0021] When the II backup charging is complete, the backup automatic transfer will issue a closing command, or 1DL will be in the closed position, or the 1DL of the 1# incoming line will be abnormally tripped, or the 5DL of the construction power supply will be abnormally tripped, or the 2DL of the right section will be abnormally tripped, or the 4DL of the left section will be abnormally tripped, or the device operation status will be abnormal, or the backup automatic transfer signal will be engaged, or the backup transfer mode 2 control word mode pressure plate or function soft pressure plate will not be engaged, then the II backup will discharge.

[0022] As a preferred embodiment of the multi-channel partial discharge detection device with anti-interference capability described in this invention, wherein: when the three phases of the busbar are energized, the construction power supply is energized, and the 5DL switch is in the open position, the backup charging is completed after 20 seconds of automatic charging.

[0023] When the III backup charging is completed, if the construction power supply 5DL switch is in the closed position, or the backup mode 2 is activated, or the 1DL switch of the 1# main incoming line is abnormally tripped, or the construction power supply 5DL switch is abnormally tripped, or the right section 2DL switch is abnormally tripped, or the left section 4DL switch is abnormally tripped, or the device operation status is abnormal, or the backup automatic transfer signal is entered, or the backup mode 3 control word mode pressure plate or function soft pressure plate is not engaged, then the III backup discharge will occur.

[0024] The beneficial effects of this invention are as follows: When the generator is out of power, the invention can test and activate the backup power supply in sequence according to the three automatic transfer modes, so that the backup power supply can be charged and then discharged, ensuring that the power supply will not be interrupted for a long time when the generator is out of power. With multiple backup power supplies and automatic transfer modes, the power supply can continue to be guaranteed, and no major power supply accident will be caused. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 A structural diagram of a multi-unit hydropower station with automatic switching system for auxiliary power supply, illustrating the automatic switching method for auxiliary power supply systems of large hydropower stations with multiple generating units.

[0027] Figure 2 A diagram illustrating an implementation example of an automatic switching method for the auxiliary power system of a large hydropower station with multiple generating units.

[0028] Figure 3 A fully distributed logic diagram of the busbar switch for the automatic transfer switching method of the power supply system of a large hydropower station with multiple units.

[0029] Figure 4 The backup power supply method for the automatic switching of power systems in large hydropower stations with multiple generating units is shown in the charging logic diagram of backup power supply mode 1.

[0030] Figure 5 The backup power supply mode 1 action logic diagram for the automatic switching method of the power supply system of a large hydropower station with multiple units.

[0031] Figure 6 The backup power supply method 2 charging logic diagram for the automatic switching method of the power supply system of a large hydropower station with multiple units.

[0032] Figure 7 The backup power supply system of a large hydropower station with multiple generating units has a backup power supply mode 2 operation logic diagram.

[0033] Figure 8 The backup power supply method for the automatic transfer method of the power supply system of a large hydropower station with multiple units is shown in the charging logic diagram of the backup power supply mode 3.

[0034] Figure 9 The backup power supply mode 3 action logic diagram for the automatic switching method of the power supply system of a large hydropower station with multiple units. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Example 1

[0039] This is the first embodiment of the present invention. This embodiment provides a method for automatic switching of the power supply system of a large hydropower station with multiple units, which includes a backup power supply I, a backup power supply II, a construction power supply, a busbar I, a busbar II, a busbar III, a main incoming line 1#, a main incoming line circuit breaker 1DL, a right sectional circuit breaker 2DL, a left sectional circuit breaker 4DL, and a construction power supply circuit breaker 5DL.

[0040] Obtain the charging status of backup power supply I, backup power supply II, and construction power supply. When a power supply is fully charged, the corresponding circuit breaker closes.

[0041] When backup power supply I is fully charged, start automatic transfer mode one.

[0042] When backup power supply II is fully charged, start automatic transfer mode II;

[0043] Once the construction power supply is fully charged, activate the third automatic transfer switch.

[0044] Specifically, when in standby automatic transfer mode 1, after the standby automatic transfer I is fully charged, the status of bus I is determined. If bus I is de-energized and there is no current in the No. 1 incoming line, construction power supply, right section 2DL, and left section 4DL, then standby automatic transfer I is activated.

[0045] It should be noted that the positional relationship between the right segment 2DL and the left segment 4DL at this time is referenced. Figure 1 The positional relationships shown are named accordingly.

[0046] Furthermore, when the automatic transfer switch I is activated, all busbar incoming line switches trip. At this time, the status of busbar I is judged. If busbar I is de-energized, it is judged whether the conditions for the activation of the backup power supply I are met. If the conditions for the activation of the backup power supply I are met, the right section 2DL circuit breaker is closed after a delay of backup transfer mode 1, and the backup I operation is completed. If the conditions for the activation of the backup power supply I are not met, or backup I fails and backup II meets the conditions for the activation of backup II, and the right section 2DL is in the closed position, a trip right section 2DL command is issued.

[0047] It should be noted that the conditions required for the backup power supply to be put into operation include: the interconnection switch 5DL with bus II is in the open position, i.e., TWJ is turned on to 1; backup power supply I needs to be powered by 3F, i.e., 3DL is in the closed position and TWJ is turned on to 0; backup power supply bus I needs to have voltage, i.e., the measured voltage is greater than the rated voltage (generally greater than 25% of the rated voltage); auxiliary conditions: the outlet pressure plate is engaged and the protection function pressure plate is engaged.

[0048] Furthermore, when in the standby automatic transfer mode 2, after the standby automatic transfer II is fully charged, the status of main incoming line 1# is determined. If main incoming line 1# has voltage, then standby automatic transfer II is activated.

[0049] Furthermore, when the II standby automatic transfer starts and enters the trip delay period, 2DL, 5DL, and 4DL trip and the corresponding circuit breakers have no current. If the II busbar is without voltage at this time, the 1# main incoming line circuit breaker 1DL closes, and the equipment completes self-recovery and is powered by the 1# main incoming line.

[0050] Furthermore, when in the standby automatic transfer mode three, if standby automatic transfer III is fully charged and standby automatic transfer I is not charged or neither standby automatic transfer I nor standby automatic transfer II meets the conditions required for the standby power supply to be put into operation, if bus III is de-energized, the construction incoming line is energized, the No. 1 main incoming line has no current, the construction power supply has no current, the right section 2DL has no current, and the left section 4DL has no current, then standby automatic transfer III will be activated.

[0051] Furthermore, when the standby automatic transfer switch III is activated, if 2DL, 5DL, and 4DL all trip, and the III busbar is de-energized while the construction power supply is energized, then the construction power supply circuit breaker 5DL will be closed after a delay via standby transfer switch III.

[0052] Furthermore, when bus I is energized and meets the conditions required for the activation of backup power supply I or backup power supply II, backup power supply I will be fully charged after a 20-second automatic charging time.

[0053] When backup power supply I is fully charged, backup power supply mode 2 or backup power supply mode 3 is activated, or the high-voltage circuit breaker trips abnormally or the switch fails to trip. If backup power supply I fails and backup power supply II is not ready or 4DL is closed, or 2DL is closed and enters the charging time while bus I is energized, the conditions required for the activation of backup power supply I and backup power supply II are met and the delay is entered. If the automatic backup transfer conditions are met, backup automatic transfer mode 1 charging will begin.

[0054] Furthermore, when the three phases of the II busbar are energized and the 1# incoming line 1DL is in the open position, the II standby charging will be completed after 20 seconds of automatic switching charging.

[0055] When the II backup charging is complete, the backup automatic transfer will issue a closing command, or 1DL will be in the closed position, or the 1DL of the 1# incoming line will be abnormally tripped, or the 5DL of the construction power supply will be abnormally tripped, or the 2DL of the right section will be abnormally tripped, or the 4DL of the left section will be abnormally tripped, or the device operation status will be abnormal, or the backup automatic transfer signal will be engaged, or the backup transfer mode 2 control word mode pressure plate or function soft pressure plate will not be engaged, then the II backup will discharge.

[0056] Furthermore, when the three phases of bus III are energized, the construction power supply is energized, and the 5DL switch is in the open position, the backup charging of bus III will be completed after 20 seconds of automatic transfer charging.

[0057] When the III backup charging is completed, if the construction power supply 5DL switch is in the closed position, or the backup mode 2 is activated, or the 1DL switch of the 1# main incoming line is abnormally tripped, or the construction power supply 5DL switch is abnormally tripped, or the right section 2DL switch is abnormally tripped, or the left section 4DL switch is abnormally tripped, or the device operation status is abnormal, or the backup automatic transfer signal is entered, or the backup mode 3 control word mode pressure plate or function soft pressure plate is not engaged, then the III backup discharge will occur.

[0058] In summary, this invention enables the sequential testing and activation of three automatic transfer switching methods when the generator is de-energized, allowing the backup power supply to charge and then discharge, ensuring that power supply will not be interrupted for an extended period when the generator is de-energized. Multiple backup power supplies and automatic transfer switching methods guarantee continued power supply, improving the power plant's fault tolerance and preventing major power supply accidents.

[0059] Example 2

[0060] This is the second embodiment of the present invention, which provides a method for automatic switching of the auxiliary power system of a large hydropower station with multiple units. It includes a symmetrical hydropower station with six hydroelectric generator units (01F to 06F) supplying auxiliary power structures (C1B to C6B). In large hydropower stations, the auxiliary power system is generally arranged in a segmented and regional manner using a 10kV voltage level busbar. The present invention is divided into four symmetrical structural regions: I, II, III, and IV. In actual production sites, these are four different equipment installation locations.

[0061] Specifically, the six busbars form a ring network structure via tie switches 4DL, 5DL, 6DL, 7DL, 14DL, and 15DL. The main incoming power supply for each busbar is provided by the generator set and connected to the busbar via plant transformers 01B to 06B.

[0062] Furthermore, 01F connects to backup power supply I via 1DL, 02F connects to bus II via 2DL, 03F connects to backup power supply II via 3DL, 04F connects to backup power supply I via 11DL, 05F connects to bus III via 12DL, and 06F connects to backup power supply II via 13DL, forming the plant's power supply system.

[0063] Furthermore, to address the issue of power outages affecting the entire plant due to unit shutdowns, an external power supply (construction power supply line) was added and located in areas III and IV. Power was supplied to areas II and III respectively via transformers SGB1 and SGB2, and this construction power supply is referred to as backup power supply III.

[0064] Furthermore, 01F is connected to the main incoming line 1DL with backup power supply I, 02F is connected to the main incoming line 2DL with backup power supply II, and 03F is connected to the main incoming line 3DL with backup power supply II. Each busbar operates in sections.

[0065] Furthermore, when the 2DL main power supply line of Bus II trips, causing a loss of voltage on Bus II, this invention uses the right section as backup power supply I and the left section as backup power supply II for Bus II.

[0066] Furthermore, the automatic transfer switch issues a trip command to trip all switches 2DL, SGDL1, 4DL, and 5DL on Bus II. Upon confirming the switch positions are open, it closes the right section 5DL tie switch, restoring Bus II voltage. At this point, Bus II is powered by the backup power supply, completing the backup transfer mode 1I backup operation. The position description of the right section 5DL is based on... Figure 2 The positional relationship is shown.

[0067] It should be noted that when the trip position relay TWJ is 1, the switch position is determined to be open, meaning the switch position is determined by whether the switch position node is connected to the automatic transfer switch. Under normal circumstances, 4DL is in the open position. When the II bus loses power, a trip command is issued again to reconfirm that the 4DL switch is in the open position.

[0068] Furthermore, if the closing process of 5DL fails, it will cause the backup power supply of section I to fail. At this time, if the power supply of the backup power supply of the left section II meets the conditions, the trip command will be issued first to trip the DL, SGDL1, 4DL and 5DL switches, and then the 4DL tie switch of the left section will be closed. The backup power supply of section II will drive the bus II to complete the backup power supply mode 1 II backup operation.

[0069] Furthermore, each of the three busbars serves as a backup for each other. Within the same area, the middle busbar segment (Bus II, Bus III) uses the right segment within the area as backup I and the left segment as backup II. For cross-area (backup II, backup I), the busbar within the same area is used as backup I, and the cross-area busbar is used as backup II.

[0070] It should be noted that the automatic transfer mode 1 is the operating mode when the backup power supply I is put into operation. In the automatic transfer mode 1, it is set to prioritize closing 5DL (prioritize putting into backup power supply I). All opening and closing actions of this automatic transfer mode are completed automatically, and there is no need to manually select the closing.

[0071] In summary, this invention enables all switches to trip when the generator fails, allowing for the detection of the I bus and the I backup power supply. This ensures that the I backup power supply can be activated promptly when the generator fails, resuming power supply and preventing prolonged power outages or major power supply accidents.

[0072] Example 3

[0073] The third embodiment of the present invention provides another method for automatic switching of the power supply system of a large hydropower station with multiple generating units.

[0074] Specifically, when the main incoming line 2DL is not connected to the generator 02F via the generator and the switch status is 4DL or 5DL in the closed position, that is, the main incoming line 2DL is used as a standby and is in the open position.

[0075] Furthermore, once the main incoming power supply of Bus II is restored, i.e., once the 02F generator is energized with C2B, the self-recovery is completed by switching to the standby automatic transfer mode.

[0076] It should be noted that after the I standby is activated, power is supplied from the I power supply after the 5DL circuit breaker is closed. Self-recovery means disconnecting the 5DL circuit breaker and closing the 2DL circuit breaker.

[0077] Furthermore, trip the construction power supply SGDL1, right segment 5DL, and left segment 4DL, then close 2DL to restore segmented operation.

[0078] Furthermore, when the II bus, the I backup power supply, and the II backup power supply all lose voltage, that is, when all generators are de-energized, the right segment 5DL and the left segment 4DL will trip, and then SGDL1 will be closed. The II bus will then be powered by the construction power supply, restoring power to the power station.

[0079] It should be noted that the right segment 5DL and the left segment 4DL here refer to... Figure 2 The positional relationship shown indicates that left and right are distinguished with the busbar as the reference.

[0080] In summary, the power supply between different areas still meets the requirements of three automatic transfer modes. That is, if the construction power supply mode is not put into operation and area I loses power, power can still be supplied through the inter-area interconnection switch 6DL or 7DL, which greatly improves the fault tolerance and reliability of the plant power supply system.

[0081] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0082] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0083] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for automatic switching of backup power in a large hydropower station with multiple generating units, characterized in that: include, Backup power supply I, backup power supply II, backup power supply III, construction power supply, 6 busbars, main incoming line, main incoming line circuit breaker 1DL, circuit breaker, and circuit breaker switch; Obtain the charging status of backup power supply I, backup power supply II, and construction power supply. When a power supply is fully charged, the corresponding circuit breaker closes. When backup power supply I is fully charged, start automatic transfer mode one. When backup power supply II is fully charged, start automatic transfer mode II; Once the construction power supply has finished charging, activate the third automatic transfer mode. The six busbars form a ring network structure via tie switches 4DL, 5DL, 6DL, 7DL, 14DL, and 15DL; The three automatic switching methods are tested and activated in sequence to charge and discharge the backup power supply. To address the issue of power outages caused by unit shutdowns within the power plant, external construction power supplies were added and located in areas III and IV. These power supplies were supplied to areas II and III via transformers SGB1 and SGB2, respectively, through SGDL1 and SGDL2. This construction power supply is referred to as backup power supply III. When in standby automatic transfer mode three, if standby automatic transfer III is fully charged and standby automatic transfer I is not charged or neither standby automatic transfer I nor standby automatic transfer II meets the conditions required for the standby power supply to be put into operation, if bus III is de-energized and the construction incoming line is energized, and the No. 1 main incoming line, the construction power supply, the right section 2DL, and the left section 4DL are de-energized, then standby automatic transfer III will be activated. When bus I is energized and meets the conditions for the activation of backup power supply I or backup power supply II, backup power supply I will be fully charged after 20 seconds of automatic charging. When backup power supply I is fully charged, backup power supply mode 2 or backup power supply mode 3 is activated, or the high-voltage circuit breaker trips abnormally or the switch fails to trip. Simultaneously, backup power supply II is not ready or 4DL is closed, or 2DL is closed and enters the charging time while backup bus is energized. At the same time, the conditions required for backup power supply I and backup power supply II to be put into operation are met and the delay is entered. The automatic backup transfer conditions are also met, and backup automatic transfer mode 1 charging begins. When the three phases of bus III are energized, the construction power supply is energized, and the 5DL switch is in the open position, the backup charging of bus III will be completed after 20 seconds of automatic transfer charging. When the III backup charging is completed, if the construction power supply 5DL switch is in the closed position, or the backup mode 2 is activated, or the 1DL switch of the 1# main incoming line is abnormally tripped, or the construction power supply 5DL switch is abnormally tripped, or the right section 2DL switch is abnormally tripped, or the left section 4DL switch is abnormally tripped, or the device operation status is abnormal, or the backup automatic transfer signal is entered, or the backup mode 3 control word mode pressure plate or function soft pressure plate is not engaged, then the III backup discharge will occur.

2. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 1, characterized in that: When in standby automatic transfer mode 1, after the standby automatic transfer I is fully charged, the status of bus I is determined. If bus I is de-energized and there is no current in incoming line #1, construction power supply, right section 2DL, and left section 4DL, then standby automatic transfer I is activated.

3. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 2, characterized in that: When the automatic transfer switch I is activated, all incoming bus switches will trip. At this time, the status of bus I is judged. If bus I is de-energized, it is judged whether the conditions for the backup power supply I are required to be activated are met. If the conditions for the backup power supply I are required to be activated are met, the right section 2DL circuit breaker is closed after a delay of backup transfer mode 1, and the backup I operation is completed. If the conditions for the backup power supply I are not met, or backup I fails and backup II meets the conditions for the backup power supply II to be activated, and the right section 2DL is in the closed position, a trip right section 2DL command is issued.

4. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 3, characterized in that: When in standby automatic transfer mode 2, after standby automatic transfer mode 2 is fully charged, the status of main incoming line 1# is judged. If main incoming line 1# has voltage, standby automatic transfer mode 2 is activated.

5. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 4, characterized in that: When the II standby automatic transfer starts and enters the trip delay period, 2DL, 5DL, and 4DL trip and the corresponding circuit breakers have no current. If the II busbar is without voltage at this time, the 1# main incoming line circuit breaker 1DL closes. At this time, the equipment completes self-recovery and is powered by the 1# main incoming line.

6. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 1, characterized in that: When the standby automatic transfer switch III is activated, if 2DL, 5DL, and 4DL all trip, and the III busbar is de-energized while the construction power supply is energized, then the construction power supply circuit breaker 5DL will be closed after a delay via standby transfer mode 3.

7. The method for automatic switching of backup power in a large hydropower station with multiple generating units as described in claim 1, characterized in that: When the three phases of bus II are energized and the No. 1 incoming line 1DL is in the open position, the backup charging of bus II will be completed after 20 seconds of automatic transfer charging. When the II backup charging is complete, the backup automatic transfer will issue a closing command, or 1DL will be in the closed position, or the 1DL of the 1# incoming line will be abnormally tripped, or the 5DL of the construction power supply will be abnormally tripped, or the 2DL of the right section will be abnormally tripped, or the 4DL of the left section will be abnormally tripped, or the device operation status will be abnormal, or the backup automatic transfer signal will be engaged, or the backup transfer mode 2 control word mode pressure plate or function soft pressure plate will not be engaged, then the II backup will discharge.

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