A flexible wiring method for power supply in thermal power plants

Abstract

This invention provides a flexible wiring method for auxiliary power in thermal power plants, including the following: 1) If only Unit #1 is operating and undergoes a normal / fault shutdown, the fast-switching device manually or automatically switches to the standby transformer power supply; 2) When Unit #1 starts, if Unit #2 is operating, power is supplied from Unit #2. The DCS is closed first, and then Unit #1 is started according to the procedure, using the common desulfurization substation limestone branch power switch for Unit #2; 3) When Unit #1 starts, if Unit #2 is not operating, power is supplied by the standby transformer for starting. After modification, this invention effectively solves the problem of starting and stopping another unit using the auxiliary power of an operating unit. This not only reduces the need for externally purchased electricity but also enriches the methods of auxiliary power dispatch, changing the traditional requirement that auxiliary power must be purchased externally. With both units mutually supplying their respective auxiliary power, "zero" external purchase of auxiliary power can be achieved, significantly saving production costs. Practical verification shows that this invention has excellent practicality in actual production, and the technical modification has generated significant economic benefits.

Description

[Technical Field]

[0001] This invention belongs to the field of circuit wiring technology, specifically relating to a flexible wiring method for power plant auxiliary power. [Background Technology]

[0002] The 10kV common desulfurization busbar section (section C) of the two high-voltage common desulfurization split transformers in the entire plant has been connected, ensuring operational flexibility. Even when one unit is out of service, the common load and the load of some units located in this section can still operate normally. However, since the 10kV working busbar section of the unit's high-voltage plant service working split transformer only has a high-voltage standby transformer for backup, the load of the 10kV working busbar section needs to be supplied by the high-voltage standby transformer to complete each unit start-up / shutdown. The unit start-up / shutdown can be divided into the following situations: First, one unit is running while the other unit is starting / shutting down; second, both units are shut down while the unit starts up; third, one unit is already shut down while the other unit is shut down under various operating conditions.

[0003] In recent years, many new generating units have adopted the generator outlet connected to GCB (Generator Power Supply Block) method, which provides start-up and shutdown power to the unit's plant service power through the main transformer's reverse power supply. However, for power plants that have been put into operation, GCB is expensive and difficult to retrofit. At present, this method is uneconomical and has a long retrofit cycle.

[0004] Another technical solution to reduce the purchase of plant power can be achieved by increasing the number of generator outlet GCB circuit breakers and increasing the plant high-voltage transformer capacity and interconnection methods. However, such upgrades are expensive, technically complex, and have a long construction period. [Summary of the Invention]

[0005] This invention provides a flexible wiring method for power plant auxiliary power to solve the problem of high costs caused by the traditional requirement to purchase auxiliary power from external suppliers.

[0006] To solve the above technical problems, the present invention adopts the following technical solution:

[0007] A flexible wiring method for power supply in a thermal power plant includes the following:

[0008] For the upgraded 10kV 1A, 1B, 2A, 2B, 1C, and 2C sections, there are three power sources. To simplify the logic, each section retains the original fast-switching device, which is used to switch from the high-voltage plant service transformer power supply to the standby transformer power supply. The standby transformer adopts a hot standby mode. The incoming power supply switches for the 10kV 1A, 1B, 2A, and 2B sections, the incoming power supply switch for the limestone powder station branch power supply of the shared desulfurization transformer of another unit, and the tie switches for the 1C and 2C sections all adopt synchronizing relay detection and synchronizing closing, which is used for manual parallel switching of power supply mutual backup between units during start-up and shutdown, as well as manual switching from the standby transformer power supply back to the power supply of the unit. The working power supply switches for sections A and B of Unit #1 and Unit #2, the incoming power supply switch for the limestone powder station branch power supply of the shared desulfurization transformer of another unit, and the synchronizing relay detection relay for the tie switch of section C are added.

[0009] Based on the unit's start-up and shutdown status, the following operating conditions are defined:

[0010] 1) If only Unit #1 is running and shuts down normally / in case of an accident, the fast-switching device will manually or automatically switch to the standby transformer power supply; if Unit #2 is running normally at the same time, when the load of Unit #1 decreases, the power switch of the limestone branch of the common desulfurization transformer of Unit #2 and the C-section tie switch will be manually closed. The synchronization relay of the limestone branch power switch of the common desulfurization transformer of Unit #2 and the C-section tie switch will detect synchronization. If synchronization fails, the standby transformer will still be used to complete the smooth shutdown of Unit #1.

[0011] 2) When Unit #1 is started, if Unit #2 is running, power is supplied from Unit #2. The DCS is closed first for the common desulfurization-limestone branch power switch of Unit #2, and then Unit #1 is started according to the procedure.

[0012] If Unit #1 starts successfully, the low-voltage side branch of the high-voltage plant service transformer of Unit #1 will take over the load after the stabilization of the fuel. Parallel switching will be adopted. The low-voltage side branch of the high-voltage plant service transformer of Unit #1, i.e., the power switch of Unit #1, will be manually closed after synchronous detection. Synchronous closing of the C section power supply line is not considered. After the A and B sections of power supply are successfully switched, the C section power supply will be directly switched in parallel.

[0013] 3) If Unit #1 is not running, the power supply from the standby transformer will start the unit.

[0014] Furthermore, the branch power supply incoming line switch for the shared desulfurization and limestone powder station of another unit, plus the C-section interconnection switch, has a total of 9 switches.

[0015] Furthermore, in step 1), the quick-cut device should be manually operated, which corresponds to a normal shutdown.

[0016] Furthermore, in step 1), the quick-cut device automatically shuts down in response to an emergency.

[0017] Furthermore, in step 1), if Unit #2 is operating normally at the same time, when the load of Unit #1 is reduced to below 40%, manually close the power switch of the common desulfurization-limestone branch from Unit #2 and the C-section interconnection switch.

[0018] Furthermore, if the synchronization fails in step 1), the standby transformer will quickly switch over to complete the smooth shutdown of Unit #1.

[0019] Furthermore, in step 2), if #2 is running while #1 is starting, it is necessary to consider operating at a certain output level so that it can simultaneously support the normal load of #2 and the starting load of #1.

[0020] Furthermore, in step 2), the power switch for the common desulfurization and limestone branch of Unit #2 includes a C-section interconnection switch.

[0021] Furthermore, in step 2), if unit #1 fails to start, unit #2 continues to run, and unit #1 is shut down via the emergency power supply and the power supply is manually switched to the standby transformer power supply.

[0022] Furthermore, in step 2), if Unit #1 fails to start and Unit #2 loses power, Unit #2 will be shut down by quickly switching to the backup transformer power supply, and Unit #1 will be shut down by the emergency power supply and the power supply will be manually switched to the backup transformer power supply.

[0023] The present invention has the following beneficial effects:

[0024] This invention effectively solves the problem of starting and stopping another unit using the power supply of the operating unit. This not only reduces the purchase of external power but also enriches the ways of using power supply. It changes the traditional situation where power supply must be purchased externally. The two units can provide each other with power supply, achieving "zero" external purchase of power supply and greatly saving production costs. [Attached Image Description]

[0025] Figure 1 This is the wiring diagram of the power plant's auxiliary power supply before the renovation.

[0026] Figure 2 This is the wiring diagram for the auxiliary power supply of the renovated thermal power plant.

Detailed Implementation Methods

[0027] To facilitate a better understanding of the present invention, the following embodiments are provided. These embodiments are within the scope of protection of the present invention, but do not limit the scope of protection of the present invention.

[0028] The applicant's high-voltage plant auxiliary voltage is 10kV Class I, with two high-voltage split transformers installed per unit. One 60 / 33-33MVA high-voltage plant auxiliary working split transformer connects two 10kV working busbar sections (Sections A and B); the other 75 / 38-38MVA high-voltage common desulfurization split transformer has one branch connecting to a 10kV common desulfurization busbar section (Section C), and the other branch connecting to a 10kV limestone powder station section. The 10kV common desulfurization busbar section (Section C) of each unit is connected to the 10kV common desulfurization busbar section (Section C) of the other unit via a tie switch; the 10kV limestone powder station section is a reserved load with a reserved capacity of 35MVA, but the limestone load has not yet been applied, and the load is zero, so this branch has been idle. A 60 / 33-33MVA split transformer (on-load tap changing) is installed for both units in the plant as a high-voltage start-up / standby transformer. (See...) Figure 1 )

[0029] For the foreseeable future, the applicant's project will maintain a single-unit operation mode. The aforementioned 10kV working busbar wiring configuration results in a significant amount of purchased electricity being consumed during each start-up and shutdown of a single unit. Furthermore, the plant auxiliary loads maintaining the unit's standby status also consume purchased electricity after the unit is shut down, representing substantial operating expenses. To reduce or even eliminate purchased electricity, the idle branch of the high-voltage common desulfurization split transformer to the 10kV limestone powder station section of the single unit, with an idle capacity of 38MVA, will be utilized. This branch will be converted into a backup power source for the start-up / shutdown of the 10kV working section of another unit (while this unit is operating), capable of handling the entire working load capacity during start-up and shutdown. In this way, the external power provided by the high-voltage start-up / standby transformer can serve only as the start-up power source when both units are shut down; or as a backup power source for the other unit under various shutdown conditions when one unit is shut down. (See...) Figure 2 )

[0030] like Figure 2 As shown, this invention modifies existing technology and innovatively develops a novel flexible wiring method for power plant auxiliary power, including the following:

[0031] For the upgraded 10kV sections 1A, 1B, 2A, 2B, 1C, and 2C, which have three power sources, to simplify the logic, each section retains its original fast-switching device for switching from the high-voltage plant auxiliary power supply to the standby power supply. The standby power supply adopts a hot standby mode. The incoming power supply switches for sections 1A, 1B, 2A, and 2B, the incoming power supply switch for the limestone powder station branch of the desulfurization substation shared by another unit, and the tie switches for sections 1C and 2C all use synchronizing relays for synchronizing closing. This is used for manual parallel switching of power supply between units during start-up and shutdown, as well as for manually switching back from the standby power supply to the unit's own power supply. Synchronizing relays are added to nine switches: the working power supply switches for sections A and B of units #1 and #2, the incoming power supply switch for the limestone powder station branch of the desulfurization substation shared by another unit, and the tie switch for section C.

[0032] The operating conditions are divided according to the start-up and shutdown status of the unit (taking Unit #1 as an example):

[0033] 1) If only Unit #1 is running and shuts down normally or due to an accident, the fast-switching device manually (for normal shutdown) or automatically (for accident shutdown) switches to the standby transformer power supply. If Unit #2 is running normally at the same time, when the load of Unit #1 drops below 40%, the power switch of the limestone branch of the common desulfurization transformer for Unit #2 and the C-section tie switch are manually closed. The synchronizing relays of the limestone branch power switch of the common desulfurization transformer for Unit #2 and the C-section tie switch are used to check for synchronization. If synchronization fails, the standby transformer will still be used to complete the smooth shutdown of Unit #1 (through fast-switching).

[0034] 2) When Unit #1 starts up, if Unit #2 is running (it needs to be considered that it is running at a certain output level so that it can simultaneously carry the normal load of Unit #2 and the starting load of Unit #1), then power is supplied from Unit #2. The DCS is closed first for the common desulfurization limestone branch power switch of Unit #2 (including the C-section interconnection switch), and then Unit #1 is started according to the procedure.

[0035] If Unit #1 starts successfully, the low-voltage branch of the high-voltage station service transformer for Unit #1 will take over the load after the combustion is stabilized. Parallel switching must be used, and the power switch of Unit #1 will be manually closed after synchronization detection of the low-voltage branch of the high-voltage station service transformer for Unit #1. Synchronization closing is not considered for the incoming power line of Section C. After successful switching of the power supply of Sections A and B, the power supply of Section C will be directly switched in parallel.

[0036] If Unit #1 fails to start, Unit #2 will continue to run, and Unit #1 will be shut down via the emergency power supply and the power supply will be manually switched to the standby transformer power supply.

[0037] If Unit #1 fails to start and Unit #2 loses power, Unit #2 will shut down by quickly switching to the backup transformer power supply, while Unit #1 will shut down by the emergency power supply and the power supply will be manually switched to the backup transformer power supply.

[0038] 3) If Unit #1 is not running, the power supply from the standby transformer will start the unit.

[0039] In thermal power plants, the high volume of electricity purchased due to start-up and shutdown significantly increases operating costs. Most unit start-up and shutdown are completed during the normal operation of a single unit. Utilizing the idle branch capacity of the plant's high-voltage transformer and improving the mutual supply of power to the plant's start-up and shutdown equipment is the best solution to greatly reduce the purchase of electricity. When two units mutually supply power to each other, the plant's power can be "zero" purchased, greatly saving costs.

[0040] Practical verification has shown that the present invention has good practicality in actual production, and the technological transformation has generated great economic benefits, demonstrating significant progress.

[0041] The above-described ideas and implementation schemes are only used to illustrate the technical solutions of the present invention and are not intended to limit it. There are many ways to apply it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art can make several improvements without departing from the principle of the present invention, and such improvements should also be considered within the scope of protection of the present invention.

Claims

1. A flexible wiring method for power supply in a thermal power plant, characterized in that, The 10kV busbar systems corresponding to Units #1 and #2 of the thermal power plant will be upgraded. The 10kV busbars corresponding to Unit #1 include working busbars 1A and 1B, and a common desulfurization busbar 1C. The 10kV busbars corresponding to Unit #2 include working busbars 2A and 2B, and a common desulfurization busbar 2C. After the upgrade, each of the 10kV busbars 1A, 1B, 2A, 2B, 1C, and 2C will be equipped with three switchable power supplies: the working power supply for the current unit, the backup power supply for the start-up transformer, and the mutual backup power supply for the other unit. To simplify the switching logic, each busbar retains its original fast-switching device, which is used to switch from the unit's working power supply to the standby transformer's backup power supply. The standby transformer adopts a hot standby mode. The unit's working power supply incoming switches for the 10kV 1A, 1B, 2A, and 2B working busbars, the branch power supply incoming switches for the desulfurization substation limestone powder station shared by the other unit, and the tie switches for the 1C and 2C busbars are all equipped with synchronizing relays. Synchronizing closing is achieved through synchronizing relay detection. This is used for manual parallel switching of power supply mutual backup between the two units during unit start-up and shutdown, as well as for manually switching from the standby transformer's backup power supply back to the unit's working power supply. The unit's working power supply switches for the A and B working busbars of Unit #1 and Unit #2, the branch power supply incoming switches for the desulfurization substation limestone powder station shared by the other unit, and the tie switches for the 1C and 2C sections are all equipped with synchronizing detection relays. Based on the unit's start-up and shutdown status, the following operating conditions are defined: 1) If only Unit #1 is running and shuts down under normal / fault conditions, the power supply to the standby transformer will be switched manually or automatically via the fast-switching device. If Unit #2 is running normally at the same time, when the load on Unit #1 decreases, the power supply from the limestone branch power switch of the common desulfurization transformer for Unit #2 and the 1C and 2C section tie switches will be manually closed. Synchronization will be checked by the synchronization relay configured on the limestone branch power switch of the common desulfurization transformer for Unit #2 and the 1C and 2C section tie switches. If synchronization fails, the standby transformer will still complete the smooth shutdown of Unit #1. 2) When starting Unit #1, if Unit #2 is in operation, Unit #2 will provide starting power to Unit #1. First, close the common desulfurization-limestone branch power switch of Unit #2 through the DCS system, and then start Unit #1 according to the procedure. If Unit #1 starts successfully, the low-voltage side branch of the high-voltage plant service transformer of Unit #1 will take over the load after the unit is stabilized. The parallel switching method will be adopted. The low-voltage side branch of the high-voltage plant service transformer of Unit #1, i.e. the working power switch of Unit #1, will be manually closed after synchronization detection. Synchronization closing is not considered for the power supply line of Section 1C. After the power supply of Sections 1A and 1B is successfully switched, the power supply of Section 1C will be directly switched in parallel. 3) If Unit #2 is not running, Unit #1 will be started by power supply from the standby transformer.

2. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, The other unit has a total of 9 power supply incoming line switches for the desulfurization and limestone powder station branch, plus the C-section interconnection switch.

3. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, In step 1), the quick-cut device should be manually operated, which corresponds to a normal shutdown.

4. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, In step 1), the quick-cut device automatically shuts down in response to an emergency.

5. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, If Unit #2 is operating normally in step 1), when the load of Unit #1 is reduced to below 40%, manually close the power switch of the common desulfurization-limestone branch from Unit #2 and the C-section interconnection switch.

6. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, If synchronization fails in step 1), the standby transformer will quickly switch over to complete the smooth shutdown of Unit #1.

7. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, In step 2), if unit #1 starts up and unit #2 is running, it is necessary to consider operating at a certain output level so that it can simultaneously support the normal load of unit #2 and the starting load of unit #1.

8. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, In step 2), the common desulfurization and limestone branch power switch for Unit #2 includes the C-section interconnection switch.

9. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, If Unit #1 fails to start in step 2), Unit #2 continues to run, and Unit #1 is shut down via the emergency power supply and the power supply is manually switched to the standby transformer power supply.

10. The flexible wiring method for power plant auxiliary power supply according to claim 1, characterized in that, If Unit #1 fails to start and Unit #2 loses power in step 2), Unit #2 will be shut down by quickly switching to the backup transformer power supply, and Unit #1 will be shut down by the emergency power supply and the power supply will be manually switched to the backup transformer power supply.

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