Thermal power plant security AC power supply automatic switching system

Abstract

The utility model discloses an automatic switching system for a security alternating current power supply of a thermal power plant. A main power supply side switch and a standby power supply side switch are arranged in an automatic power supply switching device; the diesel generating set is provided with a programmable logic controller and is connected to the security PC section bus; the single security PC section bus is connected to at least one security MCC section bus; the security MCC section bus is connected to an automatic power supply switching device through a security MCC section working inlet wire switch and a third power cable; the low-voltage working PCA section bus is connected to the main power supply side switch through a low-voltage working PCA section feeder switch and a fourth power cable, and the low-voltage working PCB section bus is connected to the standby power supply side switch through a low-voltage working PCB section feeder switch and a fifth power cable. According to the utility model, through the arrangement of the security MCC section working incoming line switch, after the commercial power returns to normal, when the commercial power needs to be switched back for power supply, the commercial power and the power supplies at two sides of the diesel engine are ensured to be in the same period.

Description

Technical Field

[0001] The utility model relates to the field of automatic control of low-voltage electrical equipment in a thermal power plant, in particular to an automatic switching system for a safety AC power supply in a thermal power plant. Background Art

[0002] At present, the power load of thermal power plants can be divided into Class 0 load and non-Class 0 load according to its importance to personal safety and equipment safety. Class 0Ⅲ load: In the event of a power outage in the entire plant or when the unit unit loses power supply, in order to ensure the safe shutdown of the unit, or to prevent endangering personal safety, etc., the load should continue to be powered by the AC security power supply during the power outage, that is, the AC security load. The AC security load of a thermal power plant requires the installation of an AC security diesel engine to quickly start the security diesel engine to supply power to the Class 0Ⅲ load of the power plant when the entire plant is out of power.

[0003] The existing security power supply system mainly relies on the security diesel programmable logic controller (PLC) and the power plant distributed control system (distributed) to complete the switch opening and closing of each low-voltage security power supply section and the switching control logic of the security power supply in the accident working condition and the restoration of the city power. The low-voltage security section wiring of the power plant is complex, and a large number of switches need to be controlled by PLC or distributed control, and a large number of switch and analog signals are collected. The system electrical control wiring and control software logic are complex, which makes the diesel engine PLC program compilation and debugging more difficult, and there will be a short power outage during the restoration of the city power.

[0004] Therefore, it is urgent to propose a new solution to solve the above problems. Summary of the invention

[0005] The utility model provides an automatic switching system for the protection of AC power supply in a thermal power plant, which solves the problems that the wiring of the low-voltage protection section of the existing power plant is complicated, a large number of switches requiring PLC or decentralized control, a large number of collected switch and analog signals, and the system electrical control wiring and control software logic are complicated, which makes the diesel engine PLC program compilation and debugging difficult.

[0006] The utility model provides a thermal power plant security AC power automatic switching system, comprising a diesel generator set, a security PC segment bus, a security MCC segment bus, an automatic power switching device, a low-voltage working PCA segment bus, a low-voltage working PCB segment bus and a power plant distributed control system;

[0007] The automatic power switching device is provided with a main power side switch and a backup power side switch;

[0008] The diesel generator set is equipped with a programmable logic controller, and the diesel generator set is connected to the security PC section busbar through the generator outlet circuit breaker, the first power cable and the security PC section incoming switch in sequence;

[0009] A single security PC section busbar is connected to at least one security MCC section busbar in sequence through a security PC section feeder switch, a second power cable, and a security MCC section standby incoming line switch;

[0010] The security MCC section busbar is connected to the automatic power supply switching device through the security MCC section working incoming line switch and the third power cable;

[0011] The low-voltage working PCA section bus is connected to the main power side switch through the low-voltage working PCA section feeder switch and the fourth power cable, and the low-voltage working PCB section bus is connected to the standby power side switch through the low-voltage working PCB section feeder switch and the fifth power cable;

[0012] The power plant distributed control system exchanges signals with the programmable logic controller and the automatic power supply switching device respectively in a communication or hard wiring manner.

[0013] Furthermore, a bus tie switch is provided between the low voltage working PCA segment bus and the low voltage working PCB segment bus.

[0014] Furthermore, the programmable logic controller includes a voltage detection module and an instruction sending module. When the normal mains power is restored, the voltage detection module is used to perform synchronous detection on the voltages on both sides of the working incoming line switch of the security MCC section; the instruction sending module is used to send a closing instruction to the working incoming line switch of the security MCC section after the synchronous detection is passed. After the diesel engine power supply and the mains power run in parallel for 10 to 30 seconds, after confirming that the mains power is stable and fault-free, the power plant distributed control system will issue an opening instruction to the backup incoming line switch of the security MCC section, the feeder switch of the security PC section, the incoming line switch of the security PC section, and the generator output circuit breaker in turn. After all switches are disconnected, the diesel generator set shutdown instruction is issued. According to the above procedures, the uninterrupted mains power recovery after the mains power is received can be realized.

[0015] Furthermore, the voltage level of the low-voltage working PCA segment bus and the low-voltage working PCB segment bus is not greater than 1KV.

[0016] Furthermore, the automatic power switching device can switch from the main power side switch to the backup power side switch within 100ms when the main power side switch loses power.

[0017] Furthermore, the power generation capacity of the diesel generator set is greater than the sum of the loads connected to the multiple security MCC bus sections.

[0018] Compared with the prior art, the beneficial effects of the utility model are:

[0019] 1. Compared with the existing security power supply switching scheme, the utility model saves one line switch of the security MCC section by adopting an automatic power supply switching device, improves the switching speed of the main and standby power supplies of the security MCC section, reduces the power outage time of the system, and reduces the number of switches that need to be controlled by the diesel engine programmable logic controller; at the same time, by setting the working line switch of the security MCC section, when switching back to the mains power supply after the mains power returns to normal, it is ensured that the power supply of the mains power and the diesel engine power supply are synchronized at the same time;

[0020] 2. When the utility model restores the mains power, the diesel engine programmable logic controller only needs to control the working incoming line switch of the security MCC section to complete the synchronization of the mains power and the diesel engine power supply, thereby realizing uninterrupted power switching between the mains power and the diesel engine power supply, reducing the number of switches that the diesel engine programmable logic controller needs to control, and ensuring that when the mains power is restored, the load connected to the security MCC section is not disconnected. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the wiring method in the first embodiment of the utility model;

[0022] Figure 2 This is a schematic diagram of the wiring method in the second embodiment of the utility model;

[0023] Figure numerals: 1. diesel generator set; 11. programmable logic controller; 12. generator output circuit breaker; 13. first power cable; 14. security PC section incoming switch; 2. security PC section bus; 21. security PC section feeder switch; 22. second power cable; 23. security MCC section standby incoming switch; 3. security MCC section bus; 31. security MCC section working incoming switch; 32. third power cable; 4. automatic power switching device; 41. main power side switch; 42. standby power side switch; 5. low-voltage working PCA section bus; 51. low-voltage working PCA section feeder switch; 52. fourth power cable; 6. low-voltage working PCB section bus; 61. low-voltage working PCB section feeder switch; 62. fifth power cable; 7. power plant distributed control system; 8. bus tie switch. DETAILED DESCRIPTION

[0024] In order to further understand the content, features and functions of the utility model, the following embodiments are given, together with the attached Figures 1-2 The detailed instructions are as follows.

[0025] like Figure 1As shown, the first embodiment provides a thermal power plant security AC power automatic switching system, including a diesel generator set 1, a security PC segment bus 2, a security MCC segment bus 3, an automatic power switching device 4, a low-voltage working PCA segment bus 5, a low-voltage working PCB segment bus 6 and a power plant distributed control system 7;

[0026] The automatic power switching device 4 is provided with a main power side switch 41 and a backup power side switch 42;

[0027] The diesel generator set 1 is equipped with a programmable logic controller 11, and the diesel generator set 1 is connected to the security PC section bus 2 through the generator outlet circuit breaker 12, the first power cable 13 and the security PC section incoming switch 14 in sequence;

[0028] The single security PC section bus 2 is connected to a security MCC section bus 3 through the security PC section feeder switch 21, the second power cable 22, and the security MCC section standby incoming line switch 23 in sequence;

[0029] The security MCC section bus 3 is connected to the automatic power supply switching device 4 through the security MCC section working incoming line switch 31 and the third power cable 32;

[0030] The low-voltage working PCA section bus 5 is connected to the main power side switch 41 through the low-voltage working PCA section feeder switch 51 and the fourth power cable 52, and the low-voltage working PCB section bus 6 is connected to the standby power side switch 42 through the low-voltage working PCB section feeder switch 61 and the fifth power cable 62;

[0031] The power plant distributed control system 7 is respectively connected to the programmable logic controller 11 and the automatic power supply switching device 4 in communication, and can also be connected in the form of hard wiring according to actual conditions.

[0032] Compared with the existing security power supply switching scheme, the utility model saves one security MCC section incoming switch by adopting an automatic power supply switching device plus a security MCC section working incoming switch, improves the switching speed of the main and standby power supplies of the security MCC section, reduces the system power outage time, and reduces the number of switches that need to be controlled by the diesel engine programmable logic controller; at the same time, by setting the security MCC section working incoming switch 31, when the city power returns to normal and it is necessary to switch back to the city power supply, it is ensured that the power supplies on both sides of the city power and the diesel engine are synchronized. The so-called synchronization here means that the voltage amplitude and phase sequence must be consistent, and the phase angle difference is within 15 degrees. Otherwise, the power switches on both sides that are not in phase will be closed, which will generate impact current to the low-voltage power supply system.

[0033] In this embodiment, a bus tie switch 8 is provided between the low-voltage working PCA segment bus 5 and the low-voltage working PCB segment bus 6. When one of the PC segment busbars and its line fails or loses power, the automatic power supply switching device 4 can promptly switch to another PC segment busbar for power supply, thereby ensuring that the other PC segment busbar normally supplies power to the security MCC segment busbar 3, thereby ensuring that the security MCC segment busbar 3 does not stop powering off; when both PC segments lose power, the power plant distributed control system 7 or the programmable logic controller 11 detects the voltage of the busbar MCC segment 3 in real time. If the voltage is zero, it is determined that the security MCC segment busbar 3 has lost the city power, thereby starting the diesel engine to supply power to the security MCC segment busbar 3.

[0034] In this embodiment, the voltage level of the low-voltage working PCA segment bus 5 and the low-voltage working PCB segment bus 6 is 400V, and can also be used for 690V or other low-voltage power supply systems, and its value is generally not greater than 1KV.

[0035] The utility model of the thermal power plant security AC power automatic switching system is divided into three modes: normal power supply, accident power failure switching and mains power recovery switching. The working processes of the three modes are respectively introduced below.

[0036] When the system is powered normally: the power plant distributed control system 7 sends a closing command to each switch, so that the low-voltage working PCA section feeder switch 51, the low-voltage working PCB section feeder switch 61, the security MCC section working incoming line switch 31, and the main power side switch 41 of the automatic power switching device 4 (ATS) are all in the closed state; while the generator output circuit breaker 12, the security PC section incoming line switch 14, the security PC section feeder switch 21, the security MCC section standby incoming line switch 23, and the standby power side switch 42 of the automatic power switching device 4 (ATS) are all in the open state, and the diesel generator set 1 is in the shutdown standby state. Among them, the main power side switch 41 corresponds to the low-voltage working PCA section bus 5, and the standby power side switch 42 corresponds to the low-voltage working PCB section bus 6.

[0037] Power outage switching: When the low-voltage security MCC section bus voltage loses pressure, the automatic power switching device 4 (ATS) switches from the main power supply state to the backup power supply state within 100ms. When the low-voltage security MCC section bus voltage has not been restored after the automatic power switching device 4 (ATS) switches, the programmable logic controller 11 collects the low-voltage security MCC section bus voltage and the closing and opening position signals of the security MCC section working incoming line switch 31, and comprehensively determines that an accident power outage has occurred in the entire plant. The programmable logic controller 11 starts the diesel generator set 1 after a 2-second delay, and at the same time sends an opening command to the low-voltage security MCC section working incoming line switch 31. After the diesel generator set 1 builds pressure and stabilizes, the programmable logic controller 11 sends a closing command to the generator output circuit breaker 12, the security PC section incoming line switch 14, the security PC section feeder switch 21, and the security MCC section standby incoming line switch 23 in sequence, and the diesel generator set 1 supplies power to the security MCC section bus.

[0038] Mains power recovery switching: When the programmable logic controller 11 detects that there is voltage on the power supply side of the security MCC section working incoming line switch 31, it determines that the whole plant is receiving power, and sends a signal to the power plant distributed control system 7 to remind the operator to perform the power supply switching operation. The operator issues a command to restore the mains power supply to the programmable logic controller 11 through the power plant distributed control system 7 in the control room. After receiving the command to restore the mains power, the programmable logic controller 11 begins to detect the voltage on the power supply side of the security MCC section working incoming line switch 31 and the outlet voltage of the diesel generator set 1. When the voltages on both sides meet the synchronous grid connection conditions, the programmable logic controller 11 automatically issues a closing command to the security MCC section working incoming line switch 31 to close the switch. When the mains power is restored to normal, it is necessary to switch back to the mains power supply. The diesel engine power supply must be synchronously connected to the grid and closed when switching to the mains power. The utility model ensures the synchronous power supply voltage on both sides of the mains power and the diesel engine power supply by setting the security MCC section working incoming line switch 31. The so-called synchronization means that the voltage amplitude and phase sequence must be consistent, and the phase angle difference is less than 15 degrees. Otherwise, when two different power supplies are switched, an impact current will be generated. When the diesel engine power supply and the city power supply are in parallel with the security MCC section and run for 10 to 30 seconds, after confirming that the city power supply is stable and fault-free, the operating personnel in the power plant distributed control system 7 sequentially issue the opening command to the security MCC section standby incoming line switch 23, the sub-security PC section feeder switch 21, the sub-security PC section incoming line switch 14, and the sub-generator outlet circuit breaker 12. After all switches are disconnected, the diesel generator set 1 shutdown command is issued, and the diesel generator set 1 is shut down and restored to the standby state, and the reverse switching of the city power is completed. When the utility model restores the city power, the diesel engine programmable logic controller only needs to control the security MCC section working incoming line switch to complete the synchronization of the power supply on both sides of the city power and the diesel engine power supply, so as to realize the uninterrupted power switching between the power supply city power and the diesel engine power supply, reduce the number of switches that the diesel engine programmable logic controller needs to control, and ensure that when the city power is restored, the load connected to the security MCC section is not uninterrupted.

[0039] like Figure 2 As shown, as the second embodiment of the utility model, a single security PC section bus 2 is connected to two security MCC section busbars 3 through a security PC section feeder switch 21, a second power cable 22, and a security MCC section standby incoming line switch 23 in sequence, wherein the power generation capacity of the diesel generator set 1 is greater than the sum of the loads connected to the two security MCC section busbars 3 to ensure normal operation.

[0040] The utility model described above only expresses the implementation method of the utility model embodiment, and cannot be understood as limiting the scope of the utility model patent, nor is it any form of limitation on the structure of the utility model embodiment. It should be pointed out that for ordinary technicians in this field, several changes and improvements can be made without departing from the concept of the utility model embodiment, which all belong to the protection scope of the utility model embodiment.

Claims

1. A thermal power plant security AC power automatic switching system, characterized by: It comprises a diesel generator set (1), a security PC segment bus (2), a security MCC segment bus (3), an automatic power supply switching device (4), a low-voltage working PCA segment bus (5), a low-voltage working PCB segment bus (6) and a power plant distributed control system (7); The automatic power supply switching device (4) is provided with a main power supply side switch (41) and a backup power supply side switch (42); The diesel generator set (1) is equipped with a programmable logic controller (11), and the diesel generator set (1) is connected to the security PC section bus (2) in sequence through a generator output circuit breaker (12), a first power cable (13) and a security PC section incoming line switch (14); A single security PC section busbar (2) is connected to at least one security MCC section busbar (3) in sequence through a security PC section feeder switch (21), a second power cable (22), and a security MCC section standby incoming line switch (23); The security MCC section busbar (3) is connected to the automatic power supply switching device (4) via the security MCC section working incoming line switch (31) and the third power cable (32); The low-voltage working PCA section busbar (5) is connected to the main power side switch (41) via the low-voltage working PCA section feeder switch (51) and the fourth power cable (52), and the low-voltage working PCB section busbar (6) is connected to the standby power side switch (42) via the low-voltage working PCB section feeder switch (61) and the fifth power cable (62); The power plant distributed control system (7) exchanges signals with the programmable logic controller (11) and the automatic power supply switching device (4) respectively in a communication or hard wiring manner.

2. The automatic switching system for AC power supply for thermal power plant safety according to claim 1 is characterized by: A bus tie switch (8) is provided between the low-voltage working PCA segment bus (5) and the low-voltage working PCB segment bus (6).

3. The automatic switching system for AC power supply for thermal power plant safety according to claim 1 is characterized by: The programmable logic controller (11) comprises a voltage detection module and an instruction sending module. When the normal mains power is restored, the voltage detection module is used to perform synchronous detection on the voltages on both sides of the security MCC section working incoming line switch (31); the instruction sending module is used to send a closing instruction to the security MCC section working incoming line switch (31) after the synchronous detection is passed. After the diesel engine power supply and the mains power are operated in parallel for 10 to 30 seconds, after confirming that the mains power is stable and has no faults, the power plant distributed control system (7) sequentially issues an opening instruction to the security MCC section standby incoming line switch (23), the security PC section feeder switch (21), the security PC section incoming line switch (14), and the generator output circuit breaker (12). After all switches are disconnected, a shutdown instruction for the diesel generator set (1) is issued.

4. The automatic switching system for AC power supply for thermal power plant safety according to claim 1, characterized in that: The voltage levels of the low-voltage working PCA segment busbar (5) and the low-voltage working PCB segment busbar (6) are not greater than 1KV.

5. The automatic switching system for AC power supply for thermal power plant safety according to claim 1 is characterized by: The automatic power supply switching device (4) can switch from the main power supply side switch (41) to the standby power supply side switch (42) within 100ms when the main power supply side switch (41) loses power.

6. The automatic switching system for AC power supply for thermal power plant safety according to claim 1, characterized in that: The power generation capacity of the diesel generator set (1) is greater than the sum of the loads connected to the multiple sections of the safety MCC busbar (3).

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