A method and device for switching and cleaning a seal filter of a water turbine main shaft

Abstract

A method and apparatus for switching and cleaning a turbine main shaft sealing filter. The method includes: when the turbine generator unit is in stable operation, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to a preset switching pressure difference threshold and the duration is greater than a preset first delay threshold, and the standby second filter is available, the first filter is switched to the second filter; after successful switching, if the inlet and outlet pressure difference of the first filter is greater than or equal to a preset cleaning pressure difference threshold and the duration is greater than a preset second delay threshold, cleaning is performed immediately; otherwise, cleaning is performed when the first filter reaches a preset cleaning time threshold. When the inlet and outlet pressure difference of the currently operating filter is continuously higher than the set threshold, switching is performed directly, saving the manual judgment process; the increased inlet and outlet pressure difference of the filter indicates a blockage fault, and cleaning is performed immediately after confirmation, shortening the fault handling time and improving the safety and reliability of the main shaft sealing system.

Description

Technical Field

[0001] This application relates to the field of control technology for the main shaft sealing system of hydropower stations, specifically to a method and device for switching and cleaning the sealing filter of a turbine main shaft. Background Technology

[0002] With the development and progress of the power industry, "unmanned operation and minimal staffing" has become an important mode of operation and management for modern hydropower stations, placing higher demands on the automation level and reliability of equipment. As the core equipment of a hydropower station, the stable operation of the main shaft sealing system of the turbine generator unit is crucial for ensuring unit safety, preventing major power safety accidents, avoiding unplanned shutdowns, and reducing the workload of operating personnel.

[0003] The existing spindle sealing system draws its main water supply from the production water supply and its backup water supply from the technical water supply. It includes two booster pumps, two coarse filters, and two fine filters, each with one main and one backup. However, the current spindle sealing system has significant shortcomings in handling filter clogging faults. When one of the operating filters triggers an alarm, manual judgment is required to determine if the alarm is caused by filter clogging, followed by manual filter switching. This process is time-consuming, reduces fault handling efficiency, and lowers the safety of the spindle sealing system's water supply.

[0004] Secondly, under manual operation and maintenance mode, the timing of cleaning after filter replacement is often determined by operators based on personal experience, leading to inconsistencies in cleaning decisions. On the one hand, unnecessary cleaning of slightly clogged filters results in wasted resources and additional equipment wear; on the other hand, delayed cleaning of severely clogged filters prevents the removed filters from being restored to a healthy standby state in a timely manner, weakening the backup capability of the spindle sealing system and affecting the operational safety of the spindle sealing system. Summary of the Invention

[0005] This application provides a method and apparatus for switching and cleaning the sealing filter of a turbine main shaft, which can solve the problems of the prior art where filter switching and cleaning decisions rely on human experience, resulting in long troubleshooting time, low efficiency, and arbitrary cleaning judgment, which affect the operational safety and backup reliability of the main shaft sealing system.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for switching and cleaning a turbine main shaft sealing filter, the method comprising: When the hydro-generator unit is in stable operation, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to the preset switching pressure difference threshold and the duration is greater than the preset first delay threshold, and the standby second filter is available, the first filter will be switched to the second filter.

[0007] After a successful switch, if the inlet and outlet pressure difference of the first filter is greater than or equal to the preset cleaning pressure difference threshold and the duration is greater than the preset second delay threshold, cleaning is performed immediately; otherwise, cleaning is performed when the first filter reaches the preset cleaning time threshold.

[0008] Furthermore, in one embodiment, the switching differential pressure threshold is set according to the maximum allowable flow resistance of the filter element.

[0009] The first delay threshold and the second delay threshold are set according to the hydraulic fluctuation cycle of the spindle sealing system.

[0010] The cleaning differential pressure threshold is set based on the effectiveness of the filter element backwashing; the cleaning time threshold is set based on the average clogging cycle of the filter element under given water quality conditions.

[0011] Furthermore, in one embodiment, switching the first filter to the second filter includes: The inlet electric valve of the second filter is opened until the preset third delay threshold is reached, and then the inlet electric valve of the first filter is closed to complete the switching operation.

[0012] The third delay threshold is set based on the settling time of the water flow in the pipes and filters.

[0013] Furthermore, in one embodiment, the criteria for determining successful switching are: opening the inlet electric valve of the second filter and timing, and within a preset switching timeout threshold, satisfying the following conditions: the inlet electric valve of the first filter is closed, the inlet electric valve of the second filter is open, and the pressure difference between the inlet and outlet of the second filter is greater than or equal to the normal operating pressure difference and the duration is greater than a preset fourth delay threshold.

[0014] The switching timeout threshold is set based on the sum of the full stroke time of the second filter inlet electric valve actuator, the time required for hydraulic stabilization, and the time for confirming differential pressure stabilization; the fourth delay threshold is set based on the stabilization time required for the main shaft sealing system to achieve dynamic equilibrium after the switching is completed.

[0015] Furthermore, in one embodiment, if the cumulative running time of the first filter since the last cleaning is greater than or equal to the cleaning time threshold, the first filter is switched to the second filter and cleaning is performed immediately.

[0016] Furthermore, in one embodiment, the cleaning includes: Open the backwash inlet and drain valves of the first filter to flush the filter element using reverse water flow.

[0017] If a single cleaning cycle reaches the preset cleaning time, the backwash water inlet electric valve is closed; the cleaning time is set according to the shortest time required for filter element regeneration determined by the backwash effectiveness test.

[0018] Maintain the sewage discharge electric valve open for a preset sewage discharge delay, and close the sewage discharge electric valve after the sewage discharge delay ends; the sewage discharge delay is set according to the filter cavity volume and the flow capacity of the sewage discharge pipeline.

[0019] Furthermore, in one embodiment, if the inlet and outlet pressure difference of the first filter drops below the switching pressure difference threshold within a preset cleaning effect determination period, and the duration is greater than or equal to a preset fifth delay threshold, the cleaning is determined to be successful, and the cumulative running time of the first filter since the last cleaning is reset to zero.

[0020] The fifth delay threshold is set according to the time required for the hydraulic pressure to stabilize after the filter cleaning is completed.

[0021] Furthermore, in one embodiment, if the water pressure of the spindle sealing system deviates from the preset stable operating range during the cleaning process, the cleaning process is suspended.

[0022] The stable operating range is set based on the rated pressure of the spindle sealing system and its allowable percentage fluctuation.

[0023] Furthermore, in one embodiment, during the switching or cleaning process, if the water pressure of the spindle sealing system is lower than a preset water pressure threshold, the current process is paused.

[0024] The water pressure threshold is set according to the minimum water supply pressure required for the safe operation of the spindle sealing device.

[0025] Secondly, this application provides a turbine main shaft seal filter switching and cleaning device, the device comprising: The switching module is used to switch the first filter to the second filter when the hydro-generator unit is in a stable operating state, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to a preset switching pressure difference threshold and the duration is greater than a preset first delay threshold, and the standby second filter is available.

[0026] The cleaning module is used to perform cleaning immediately after a successful switch if the inlet and outlet pressure difference of the first filter is greater than or equal to a preset cleaning pressure difference threshold and the duration is greater than a preset second delay threshold; otherwise, cleaning is performed when the first filter reaches a preset cleaning time threshold.

[0027] The beneficial effects of the technical solutions provided in this application include: This application monitors the inlet and outlet pressure difference of the first filter in real time under stable operation of the hydro-generator unit, and sets a switching pressure difference threshold and a first delay threshold. When the pressure difference exceeds the standard and is continuously confirmed, and the backup filter is available, the switching is performed directly. This eliminates the traditional mode of relying on manual judgment of alarm causes and directly responds based on changes in physical quantities. It effectively solves the problem of time-consuming manual judgment, improves the timeliness and accuracy of fault handling, and thus ensures the continuity of water supply and operational safety of the main shaft sealing system.

[0028] After successful filter switching, a cleaning differential pressure threshold and a second delay threshold are further set, using objective physical quantities as a unified standard for cleaning decisions. For severe blockages that reach the cleaning differential pressure threshold, the cleaning process is executed immediately to ensure the filter quickly returns to a healthy standby state. For minor blockages that do not reach the cleaning differential pressure threshold, cleaning is performed when the preset cleaning time threshold is reached. This avoids over-cleaning caused by inaccurate judgment based on human experience, reducing water waste, sewage discharge burden, and unnecessary equipment wear and tear.

[0029] By linking filter switching and cleaning, this application can directly switch the filter when the inlet and outlet pressure difference of the currently operating filter is continuously higher than the set threshold, saving the process of manual judgment and intervention. At the same time, the cleaning conditions are used to determine the blockage fault of the increased inlet and outlet pressure difference of the filter, and cleaning is started immediately after confirmation, which shortens the overall fault handling time and effectively improves the operating efficiency, safety and backup reliability of the spindle sealing system. Attached Figure Description

[0030] Figure 1 This is a flowchart of the turbine main shaft sealing filter switching and cleaning method according to an embodiment of this application.

[0031] Figure 2 This is a schematic diagram of the spindle sealing system according to an embodiment of this application.

[0032] Figure 3 This is a logic block diagram of the OK condition of the spindle sealing system in an embodiment of this application.

[0033] Figure 4 This is a flowchart of the switching and cleaning process for the coarse filter in Embodiment 1 of this application.

[0034] Figure 5 This is a block diagram of the OK condition logic for the coarse filter in Embodiment 2 of this application.

[0035] Figure 6 This is a flowchart of the coarse filter switching and cleaning process in Embodiment 2 of this application.

[0036] Figure 7 This is a block diagram of the OK condition logic for the coarse filter in Embodiment 1 of this application.

[0037] Figure 8 This is a flowchart of the switching and cleaning process for the fine filter in Embodiment 3 of this application.

[0038] Figure 9 This is a block diagram of the OK condition logic for the fine filter in Embodiment 4 of this application.

[0039] Figure 10 This is a flowchart of the fine filter switching and cleaning process in Embodiment 4 of this application.

[0040] Figure 11 This is a block diagram of the OK condition logic for the fine filter in Embodiment 3 of this application.

[0041] Figure 12 This is a block diagram of the turbine main shaft seal filter switching and cleaning device according to an embodiment of this application. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0043] First, some of the technical terms used in this application will be explained to help those skilled in the art understand this application.

[0044] Main shaft sealing system: Installed below the turbine guide bearing, it consists of two parts: a working seal and a maintenance seal (referred to as an air shroud). The working seal is a hydrostatic self-adjusting axial seal, mainly composed of a sliding ring, sealing block, floating ring, support ring, adjustment device, and water supply device. It allows for inspection, adjustment, and replacement of sealing elements without disassembling the main shaft, turbine guide bearing, or water guide mechanism. The maintenance seal is an air shroud seal, mainly composed of an air shroud, maintenance seal seat, sealing seat, and air supply and exhaust devices. It is put into use when the unit is shut down and preparations are made for maintenance of the working seal. It is a static expansion seal and must be removed before the unit rotates.

[0045] Hydro-generator set: A complete set of power generation equipment consisting of a hydro turbine, a generator, and other auxiliary equipment.

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0047] In a first aspect, embodiments of this application provide a method for switching and cleaning a turbine main shaft sealing filter.

[0048] In one embodiment, see Figure 1 As shown, the above-mentioned method for switching and cleaning the turbine main shaft seal filter includes: S1. When the hydro-generator unit is in stable operation, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to the preset switching pressure difference threshold and the duration is greater than the preset first delay threshold, and the standby second filter is available, the first filter is switched to the second filter.

[0049] S2. After successful switching, if the inlet and outlet pressure difference of the first filter is greater than or equal to the preset cleaning pressure difference threshold and the duration is greater than the preset second delay threshold, cleaning is performed immediately; otherwise, cleaning is performed when the first filter reaches the preset cleaning time threshold.

[0050] The aforementioned stable operating state refers to the unit speed, total inlet water pressure of the main shaft seal, and total inlet water flow rate of the main shaft seal all being within their respective stable ranges. In this embodiment, the speed n ≥ 95% of the rated speed, and the total inlet water pressure P of the main shaft seal is... 总 ≥0.75MPa, total water inlet flow rate of main shaft seal 24m³ 3 ≤Q 总 ≤28m 3 .

[0051] The prerequisite for implementing the above-mentioned turbine main shaft seal filter switching and cleaning method is that the main shaft sealing system is OK (i.e., the equipment is healthy and usable). See also Figure 2 As shown, Figure 2This is a schematic diagram of the main spindle sealing system. The main spindle sealing system includes a main water source and a backup water source. The main water source is production water, and the backup water source is the unit's technical water supply. The main water source pipeline is sequentially equipped with measuring point 2124 and electric valve DF13, and then connects to the No. 2 coarse filter via measuring point 2124 and electric valve DF15. The backup water source pipeline is sequentially equipped with measuring point 2115 and electric valve DF12, then splits into two paths: one path connects to the No. 1 booster pump via measuring point 2116, and the other path connects to the No. 2 booster pump via measuring point 2117. The two booster pumps are connected in parallel, with measuring points 21YN03 and 2120 connected in parallel between them. The outlet ends are equipped with measuring points 2119 and 2118, respectively, and then converge via measuring points 2121, 2126, and electric valve DF14 to connect to the No. 1 coarse filter. The spindle sealing system includes multiple sets of parallel filters, such as No. 1 coarse filter and No. 2 coarse filter, No. 1 fine filter and No. 2 fine filter. No. 1 coarse filter and No. 2 coarse filter are led to the downstream drainage ditch of the lower layer of the volute. Each set of filters is equipped with a corresponding inlet electric valve, drain electric valve, backwash inlet electric valve, and measuring points. The electric valves include DFFCX01, DFFCX02, DFFCX03, DFFCX04, DF16, DF17, DF18, DF19, DF20, and DF21, and the measuring points include 2128, 2129, 2130, 2131, 2132, 2133, 2134, 2315, 2136, 2138, 2139, and 2140. The drain pipes of each filter are connected to the main drain pipe of the spindle seal water filter. The water outlet of each filter is connected to the main spindle sealing device after passing through measuring points 2141, 2142, 2143 and 2144, and water is supplied to the main spindle sealing device.

[0052] See Figure 3 As shown, Figure 3 The following is the OK condition logic block diagram for the spindle sealing system. The OK condition includes: spindle sealing system inlet water pressure P. 总 >0.75MPa, spindle sealing system inlet water flow meets 24m³ / h 3 ≤Q 总 ≤28m 3The following conditions must be met simultaneously: no faults in the spindle sealing system; the electric valve DF12 at the inlet of the spindle sealing system water tank is fully closed; the electric valve DF13 at the inlet of the spindle sealing system water tank is fully closed; the AC220V power supply to the spindle sealing control cabinet is normal; the DC220V power supply to the spindle sealing control cabinet is normal; the DC24V combined power supply to the spindle sealing control cabinet is normal; the PLC to the spindle sealing control cabinet is normal; a low flow alarm for the spindle sealing system is present; the spindle sealing booster pump #1 is in automatic control mode; the spindle sealing booster pump #2 is in automatic control mode; the electric valves DF12, DF13, DF14, DF15, DF18, and DF19 of the spindle sealing system are all in automatic control mode; the filters #1, #2, #3, and #4 of the spindle sealing system are all in remote control mode; and the communication between the spindle sealing control cabinet and the monitoring system is normal.

[0053] In this embodiment, by real-time monitoring of the inlet and outlet pressure difference and cumulative running time of the operating filter, combined with preset switching pressure difference threshold, cleaning pressure difference threshold and cleaning time threshold, the switching is automatically completed when the pressure difference continuously exceeds the standard and the backup filter is available. The cleaning process is automatically triggered according to the degree of blockage or running time, thereby transforming the passive mode of traditional manual judgment and operation into a closed-loop control based on physical quantity thresholds. This solves the problems of long manual intervention time and arbitrary cleaning, and improves the fault response efficiency and backup reliability of the spindle sealing system.

[0054] Furthermore, in one embodiment, if the immediate cleaning condition in step S2 is not met—that is, if the inlet and outlet pressure difference of the first filter is not simultaneously greater than or equal to a preset cleaning pressure difference threshold and the duration is not greater than a preset second delay threshold—it indicates that the increase in the inlet and outlet pressure difference of the first filter may be due to other reasons. In this case, the spindle sealing system can alert relevant maintenance personnel to troubleshoot other faults through alarms or other means. This method effectively distinguishes between filter blockage faults and non-blockage anomalies, enabling maintenance personnel to quickly screen fault categories and intervene precisely, further saving troubleshooting and processing time, and improving the fault diagnosis efficiency and operational reliability of the spindle sealing system.

[0055] The first and second delay thresholds are set according to the hydraulic fluctuation cycle of the spindle sealing system. In this embodiment, they can be set to 15s. The cleaning pressure difference threshold is set according to the effectiveness of the filter element backwashing. In this embodiment, it can be set to 0.05MPa. The cleaning time threshold is set according to the average clogging cycle of the filter element under given water quality conditions. In this embodiment, it can be set to 72h.

[0056] Furthermore, in one embodiment, the switching differential pressure threshold in step S1 is set according to the maximum allowable flow resistance of the filter element. In this embodiment, it can be 0.03 MPa.

[0057] Furthermore, in one embodiment, in step S1 above, the first filter is switched to the second filter, specifically as follows: The inlet electric valve of the second filter is opened until the preset third delay threshold is reached, and then the inlet electric valve of the first filter is closed to complete the switching operation.

[0058] The third delay threshold is set according to the stabilization time of the water flow in the pipe and filter. In this embodiment, it can be 30 seconds.

[0059] Furthermore, in one embodiment, the criteria for determining a successful switch are: opening the inlet electric valve of the second filter and timing it; within a preset switch timeout threshold, the following conditions are met: the inlet electric valve of the first filter is closed, the inlet electric valve of the second filter is open, and the pressure difference between the inlet and outlet of the second filter is greater than or equal to the normal operating pressure difference and the duration is greater than a preset fourth delay threshold.

[0060] The switching timeout threshold is set based on the sum of the full stroke time of the second filter inlet electric valve actuator, the time required for hydraulic stabilization, and the time for confirming differential pressure stabilization. In this embodiment, it can be set to 2 minutes. The fourth delay threshold is set based on the stabilization time required for the hydraulic system of the main shaft sealing system to reach dynamic equilibrium after the switching is completed. In this embodiment, it can be set to 15 seconds.

[0061] In this embodiment, by setting a switching timeout threshold and a fourth delay threshold, it is ensured that the spindle sealing system has sufficient time to complete valve operation, hydraulic stabilization, and differential pressure confirmation after the backup filter is put into operation. This avoids misjudgment of switching failure due to valve jamming, water flow disturbance, or instantaneous pressure fluctuations. Once all conditions are met within the specified time, the switching is considered successful, and the process continues. If the conditions are not met after the timeout, the switching is considered a failure, the original operating filter is automatically restored, and an alarm signal is issued. This mechanism effectively ensures the reliability and safety of the switching process, avoids the risk of spindle seal water supply interruption due to switching failure, and further improves the operational stability and automation level of the spindle sealing system.

[0062] Furthermore, in one embodiment, if the cumulative running time of the first filter since the last cleaning is greater than or equal to the cleaning time threshold, regardless of whether its inlet and outlet pressure difference is greater than or equal to the switching pressure difference threshold, the first filter is switched to the second filter and cleaning is performed immediately.

[0063] In this embodiment, a preventative cleaning mechanism based on cumulative operating time is introduced. Before a significant increase in differential pressure is observed in the filter, switching and cleaning are proactively performed based on its average clogging cycle, achieving an upgrade from passive response to proactive prevention in the operation and maintenance mode. This effectively avoids the risk of sudden differential pressure exceeding limits due to the gradual accumulation of filter element clogging, preventing sudden filter failure during operation and ensuring the stability of the spindle seal water supply. Simultaneously, by prioritizing the cleaning time, the filter element is always maintained in an optimal flow state, extending the filter's service life and reducing the need for frequent backwashing and filter element replacement due to severe clogging. This further reduces equipment maintenance costs and the workload of maintenance personnel, comprehensively improving the operational reliability and intelligent operation and maintenance level of the spindle seal system.

[0064] Furthermore, in one embodiment, the cleaning step in step S2 above is as follows: Open the backwash inlet and drain valves of the first filter to flush the filter element using reverse water flow.

[0065] If a single cleaning cycle reaches the preset cleaning time, the aforementioned backwash inlet electric valve is closed. The cleaning time is set based on the minimum time required for filter cartridge regeneration determined by the backwash effectiveness test; in this embodiment, 3 minutes can be used.

[0066] The drain valve is kept open for a preset drain delay. Once the drain delay ends, the drain valve is closed. The drain delay is set according to the filter chamber volume and the flow capacity of the drain pipe; in this embodiment, 30 seconds can be used.

[0067] In this embodiment, the cleaning process is divided into two stages: backwashing and wastewater discharge delay. Cleaning and wastewater discharge delays are set for each stage, enabling precise control of the filter cleaning process. During the backwashing stage, the cleaning time is set based on the minimum time required for filter element regeneration, ensuring effective removal of impurities from the filter element surface while avoiding damage and water waste due to over-rinsing. During the wastewater discharge delay stage, a reasonable discharge delay is set based on the filter chamber volume and the flow capacity of the discharge pipeline, ensuring that the wastewater generated during backwashing is fully discharged, preventing secondary pollution from residual wastewater. This mechanism optimizes the utilization efficiency of cleaning resources and extends the service life of the filter element while ensuring effective cleaning. It also ensures that the cleaned filter can quickly return to a healthy, ready-to-use state, further enhancing the backup capability and operational reliability of the spindle sealing system.

[0068] Furthermore, in one embodiment, if the inlet and outlet pressure difference of the first filter drops below the switching pressure difference threshold within the preset cleaning effect determination period, and the duration is greater than or equal to the preset fifth delay threshold, the cleaning is determined to be successful, and the cumulative running time of the first filter since the last cleaning is completed is reset to zero, and the timing is restarted when the first filter is started again.

[0069] If the conditions for successful cleaning are not met, the cleaning is deemed a failure, a serious filter blockage alarm signal is issued, the cleaning process is terminated, and a filter replacement reminder message is sent.

[0070] The fifth delay threshold is set according to the time required for the hydraulic pressure to stabilize after the filter is cleaned. In this embodiment, it can be set to 15 seconds.

[0071] In this embodiment, a closed-loop verification of the cleaning effect is achieved by setting a cleaning effect judgment period and a fifth delay threshold after cleaning is completed: if the pressure difference between the filter inlet and outlet steadily drops below the switching pressure difference threshold within the judgment period, the cleaning is considered successful and the accumulated running time is reset to ensure that the filter is re-entered into the standby state in a healthy condition; if the pressure difference fails to decrease effectively within the judgment period, the cleaning is considered a failure and a severe filter element blockage alarm is issued, prompting maintenance personnel to replace the filter element in a timely manner. This effectively avoids repeated misjudgments and equipment idling caused by ineffective cleaning, ensuring that only filters that have truly recovered their health can be put back into the standby sequence. At the same time, it provides an objective basis for filter element life management, further improving the reliability of the spindle sealing system's standby guarantee and the accuracy of filter element maintenance.

[0072] Furthermore, in one embodiment, if the water pressure of the spindle sealing system deviates from the preset stable operating range during the cleaning process, the cleaning process is paused, and priority is given to ensuring the stability of the water supply to the spindle sealing system. Once the water pressure of the spindle sealing system returns to normal, the unfinished cleaning process is automatically resumed.

[0073] The stable operating range is set according to the rated pressure of the spindle sealing system and its allowable fluctuation percentage. In this embodiment, ±10% of the rated pressure can be used.

[0074] Furthermore, in one embodiment, if the water pressure of the spindle sealing system is lower than a preset water pressure threshold during the switching or cleaning process, the current process is paused to prioritize the safe and stable operation of the spindle sealing system.

[0075] The water pressure threshold is set according to the minimum water supply pressure required for the safe operation of the spindle sealing device. In this embodiment, it can be 0.5 MPa.

[0076] See Figure 4 As shown, an embodiment of the switching and cleaning process for coarse filter #1 is given, and the specific steps are as follows: A1. Determine whether the hydro-generator unit is operating stably. If not, proceed to step A2; if yes, proceed to step A3.

[0077] A2. Exit process.

[0078] A3. Determine the inlet and outlet pressure difference P of coarse filter #1. 01 If the switching differential pressure threshold P1 is greater than or equal to the preset threshold and the duration is greater than 15 seconds, proceed to step A4 if no, and proceed to step A5 if yes.

[0079] A4. Determine whether the cumulative running time of the No. 1 coarse filter since the last cleaning is greater than or equal to 72 hours. If not, proceed to step A3; if yes, proceed to step A5.

[0080] A5. Determine if the #2 coarse filter meets the OK condition. If not, proceed to step A6; if yes, proceed to step A7.

[0081] See Figure 5 As shown, Figure 5 The following is a logic block diagram of the OK condition for coarse filter #2. The OK conditions include: coarse filter #2 of the spindle seal is fault-free, coarse filter #2 of the spindle seal is under remote control, and coarse filter #2 of the spindle seal communicates normally with the PLC. All of the above conditions must be met simultaneously.

[0082] A6. Issue an alarm signal and exit the process.

[0083] A7. Execute the process of switching from coarse filter #1 to coarse filter #2 and start timing.

[0084] The specific steps for switching from coarse filter #1 to coarse filter #2 are as follows: The spindle sealing system slowly opens the inlet electric valve DF15 of the No. 2 coarse filter. After the No. 2 coarse filter inlet electric valve DF15 is fully open, it delays for 30 seconds and then closes the inlet electric valve DF14 of the No. 1 coarse filter. At the same time, the operating status of the No. 1 coarse filter is marked as pending cleaning. After the No. 1 coarse filter inlet electric valve DF14 is completely closed, the industrial control computer human-machine interface displays a filter switching completion prompt.

[0085] A8. Determine whether, within 2 minutes of opening the inlet electric valve of coarse filter #2, the inlet electric valve of coarse filter #1 is closed, the inlet electric valve of coarse filter #2 is open, and the inlet-outlet pressure difference P of coarse filter #2 is met. 02 If the pressure difference is greater than or equal to the normal operating pressure difference P0 and the duration is greater than 15s, proceed to step A9 if not, and proceed to step A10 if yes.

[0086] A9. Issue a switching timeout alarm signal, exit the process, and automatically resume operation of the No. 1 coarse filter.

[0087] A10. Determine the inlet and outlet pressure difference P of coarse filter #1. 01 If the pressure difference is greater than or equal to the preset cleaning pressure differential threshold P2 and the duration is greater than 15s, proceed to step A11 if no, and proceed to step A13 if yes.

[0088] A11. Determine whether the No. 1 coarse filter has reached the preset cleaning time threshold of 72h. If not, proceed to step A12; if yes, proceed to step A13.

[0089] A12. Continue monitoring the cumulative running time of the No. 1 coarse filter since the last cleaning, and proceed to step A10.

[0090] A13. Perform cleaning on the #1 coarse filter.

[0091] The specific cleaning steps are as follows: The spindle sealing system opens the backwash water inlet electric valve DFFCX01 of the No. 1 coarse filter and the drain electric valve DF16 of the No. 1 coarse filter to flush the filter element impurities using reverse water flow. During the backwashing process, the backwash water flow pressure is controlled to not exceed 1.2 times the normal operating water flow pressure of the spindle sealing system.

[0092] After a single cleaning cycle of the No. 1 coarse filter reaches 3 minutes, the backwash inlet electric valve DFFCX01 of the No. 1 coarse filter is closed, while the drain electric valve DF16 of the No. 1 coarse filter remains open for 30 seconds to remove the residual sewage in the No. 1 coarse filter.

[0093] The spindle sealing system shuts off the drain valve DF16 of the No. 1 coarse filter, and the No. 1 coarse filter is restored to standby status, awaiting the next commissioning.

[0094] A14. Determine the inlet and outlet pressure difference P of the #1 coarse filter within the preset cleaning effect judgment period of 3 minutes. 01 If the voltage drops below the aforementioned switching differential threshold P1 and the duration is greater than or equal to the preset fifth delay threshold of 15 seconds, proceed to step A15 if no, and proceed to step A16 if yes.

[0095] A15. Issue a serious filter blockage alarm signal, exit the cleaning process, and push a filter replacement reminder message.

[0096] A16. The industrial control computer's human-machine interface has been successfully cleaned. Set the cumulative running time of the No. 1 coarse filter to 0 and exit the process.

[0097] See Figure 6 As shown, an embodiment of the switching and cleaning process for coarse filter #2 is given, and the specific steps are as follows: B1. Determine whether the hydro-generator unit is operating stably. If not, proceed to step B2; if yes, proceed to step B3.

[0098] B2. Exit Process.

[0099] B3. Determine the inlet and outlet pressure difference P of coarse filter #2. 02 If the switching differential pressure threshold P1 is greater than or equal to the preset threshold and the duration is greater than 15 seconds, proceed to step B4 if no, and proceed to step B5 if yes.

[0100] B4. Determine whether the cumulative running time of the No. 2 coarse filter since the last cleaning is greater than or equal to 72 hours. If not, proceed to step B3; if yes, proceed to step B5.

[0101] B5. Determine if the #1 coarse filter meets the OK condition. If not, proceed to step B6; if yes, proceed to step B7.

[0102] See Figure 7 As shown, Figure 7 The following is a logic block diagram of the OK condition for coarse filter #1. The OK condition includes: coarse filter #1 of the spindle seal is fault-free, coarse filter #1 of the spindle seal is under remote control, and coarse filter #1 of the spindle seal communicates normally with the PLC. All of the above conditions must be met simultaneously.

[0103] B6. Issue an alarm signal and exit the process.

[0104] B7. Execute the process of switching from coarse filter #2 to coarse filter #1, and start timing.

[0105] The specific steps for switching from coarse filter #2 to coarse filter #1 are as follows: The spindle sealing system slowly opens the inlet electric valve DF14 of the No. 1 coarse filter. After the No. 1 coarse filter inlet electric valve DF14 is fully open, it delays for 30 seconds and then closes the inlet electric valve DF15 of the No. 2 coarse filter. At the same time, the operating status of the No. 2 coarse filter is marked as pending cleaning. After the No. 2 coarse filter inlet electric valve DF15 is completely closed, the industrial control computer human-machine interface displays a filter switching completion prompt.

[0106] B8. Determine whether, within 2 minutes of opening the inlet electric valve of coarse filter #1, the inlet electric valve of coarse filter #2 is closed, the inlet electric valve of coarse filter #1 is open, and the inlet-outlet pressure difference P of coarse filter #1 is met. 01 If the pressure difference is greater than or equal to the normal operating pressure difference P0 and the duration is greater than 15s, proceed to step B9 if not, and proceed to step B10 if yes.

[0107] B9. Issue a switching timeout alarm signal, exit the process, and automatically resume operation of the #2 coarse filter.

[0108] B10. Determine the inlet and outlet pressure difference P of coarse filter #2. 02 If the pressure difference is greater than or equal to the preset cleaning pressure difference threshold P2 and the duration is greater than 15s, proceed to step B11 if no, and proceed to step B13 if yes.

[0109] B11. Determine whether the #2 coarse filter has reached the preset cleaning time threshold of 72 hours. If not, proceed to step B12; if yes, proceed to step B13.

[0110] B12. Continue monitoring the cumulative running time of the No. 2 coarse filter since the last cleaning, and proceed to step B10.

[0111] B13. Perform cleaning on the #2 coarse filter.

[0112] The specific cleaning steps are as follows: The spindle sealing system opens the backwash inlet electric valve DFFCX02 of the No. 2 coarse filter and the drain electric valve DF17 of the No. 2 coarse filter to flush the filter element impurities using reverse water flow. During the backwashing process, the backwash water pressure is controlled to not exceed 1.2 times the normal operating water pressure of the spindle sealing system.

[0113] After a single cleaning cycle of the No. 2 coarse filter reaches 3 minutes, the backwash inlet electric valve DFFCX02 of the No. 2 coarse filter is closed, while the drain electric valve DF17 of the No. 2 coarse filter remains open for 30 seconds to remove the residual sewage in the No. 2 coarse filter.

[0114] The spindle sealing system shuts off the drain valve DF17 of the No. 2 coarse filter, and the No. 2 coarse filter is restored to standby status, awaiting the next commissioning.

[0115] B14. Determine the inlet and outlet pressure difference P of the #2 coarse filter within the preset cleaning effect judgment period of 3 minutes. 02 If the voltage drops below the aforementioned switching differential threshold P1 and the duration is greater than or equal to the preset fifth delay threshold of 15 seconds, proceed to step B15 if no, and proceed to step B16 if yes.

[0116] B15. Issues a serious filter blockage alarm signal, exits the cleaning process, and sends a filter replacement reminder message.

[0117] B16. The industrial control computer's human-machine interface has been successfully cleaned. Set the cumulative running time of the No. 2 coarse filter to 0 and exit the process.

[0118] See Figure 8 As shown, an embodiment of the switching and cleaning process for the No. 3 fine filter is given, and the specific steps are as follows: C1. Determine whether the hydro-generator unit is operating stably. If not, proceed to step C2; if yes, proceed to step C3.

[0119] C2. Exit process.

[0120] C3. Determine the inlet and outlet pressure difference P of the No. 3 fine filter. 03 If the switching differential pressure is greater than or equal to the preset switching differential pressure threshold P1 and the duration is greater than 15s, proceed to step C4 if no, proceed to step C4 if yes.

[0121] C4. Determine whether the cumulative running time of the No. 3 fine filter since the last cleaning is greater than or equal to 72 hours. If not, proceed to step C3; if yes, proceed to step C5.

[0122] C5. Determine if the #4 fine filter meets the OK condition. If not, proceed to step C6; if yes, proceed to step C7.

[0123] See Figure 9 As shown, Figure 9 The following is a logic block diagram for the OK condition of the No. 4 fine filter. The OK conditions include: the No. 4 fine filter of the spindle seal is fault-free, the No. 4 fine filter of the spindle seal is under remote control, and the No. 4 fine filter of the spindle seal communicates normally with the PLC. All of the above conditions must be met simultaneously.

[0124] C6. Issue an alarm signal and exit the process.

[0125] C7. Execute the process of switching from fine filter #3 to fine filter #4 and start timing.

[0126] The specific steps for switching from fine filter #3 to fine filter #4 are as follows: The spindle sealing system slowly opens the inlet electric valve DF19 of the No. 4 fine filter. After the No. 4 fine filter inlet electric valve DF19 is fully open, it delays for 30 seconds and then closes the inlet electric valve DF18 of the No. 3 fine filter. At the same time, the operating status of the No. 3 fine filter is marked as pending cleaning. After the No. 3 fine filter inlet electric valve DF18 is completely closed, the industrial control computer human-machine interface displays a filter switching completion prompt.

[0127] C8. Determine whether, within 2 minutes of opening the inlet electric valve of the #4 fine filter, the inlet electric valve of the #3 fine filter is closed, the inlet electric valve of the #4 fine filter is open, and the inlet-outlet pressure difference P of the #4 fine filter is met. 04 If the pressure difference is greater than or equal to the normal operating pressure difference P0 and the duration is greater than 15s, proceed to step C9 if not, and proceed to step C10 if yes.

[0128] C9. Issue a switching timeout alarm signal, exit the process, and automatically resume operation of the No. 3 fine filter.

[0129] C10. Determine the inlet and outlet pressure difference P of the No. 3 fine filter. 03 If the pressure difference is greater than or equal to the preset cleaning pressure difference threshold P2 and the duration is greater than 15s, proceed to step C11 if no, and proceed to step C13 if yes.

[0130] C11. Determine whether the #3 fine filter has reached the preset cleaning time threshold of 72 hours. If not, proceed to step C12; if yes, proceed to step C13.

[0131] C12. Continue monitoring the cumulative running time of the No. 3 fine filter since the last cleaning, and proceed to step C10.

[0132] C13. Perform cleaning on the #3 fine filter.

[0133] The specific cleaning steps are as follows: The spindle sealing system opens the backwash inlet electric valve DFFCX03 of the No. 3 fine filter and the drain electric valve DF20 of the No. 3 fine filter to flush the filter element impurities using reverse water flow. During the backwashing process, the backwash water pressure is controlled to not exceed 1.2 times the normal operating water pressure of the spindle sealing system.

[0134] After a single cleaning cycle of the No. 3 fine filter lasts for 3 minutes, the backwash inlet electric valve DFFCX03 of the No. 3 fine filter is closed, while the drain electric valve DF20 of the No. 3 fine filter remains open for 30 seconds to remove residual wastewater from the No. 3 fine filter.

[0135] The spindle sealing system shuts off the drain valve DF20 of the No. 3 fine filter, and the No. 3 fine filter is restored to standby status, awaiting the next commissioning.

[0136] C14. Determine the inlet and outlet pressure difference P of the #3 fine filter within the preset cleaning effect judgment period of 3 minutes. 03 If the voltage drops below the aforementioned switching differential threshold P1 and the duration is greater than or equal to the preset fifth delay threshold of 15 seconds, proceed to step C15 if no, and proceed to step C16 if yes.

[0137] C15. Issues a severe filter blockage alarm signal, exits the cleaning process, and sends a filter replacement reminder message.

[0138] C16. The industrial control computer's human-machine interface has been successfully cleaned. Set the cumulative running time of the No. 3 fine filter to 0 and exit the process.

[0139] See Figure 10 As shown, an embodiment of the switching and cleaning process for a No. 4 fine filter is given, and the specific steps are as follows: D1. Determine whether the hydro-generator unit is operating stably. If not, proceed to step D2; if yes, proceed to step D3.

[0140] D2. Exit process.

[0141] D3. Determine the inlet and outlet pressure difference P of the No. 4 fine filter. 04 If the switching differential pressure is greater than or equal to the preset switching differential pressure threshold P1 and the duration is greater than 15s, proceed to step D4 if no, proceed to step D4 if yes.

[0142] D4. Determine whether the cumulative running time of the No. 4 fine filter since the last cleaning is greater than or equal to 72 hours. If not, proceed to step D3; if yes, proceed to step D5.

[0143] D5. Determine whether the #3 fine filter meets the OK condition. If not, proceed to step D6; if yes, proceed to step D7.

[0144] See Figure 11 As shown, Figure 11 The following is a logic block diagram for the OK condition of the No. 3 fine filter. The OK conditions include: the No. 3 fine filter of the spindle seal is fault-free, the No. 3 fine filter of the spindle seal is under remote control, and the No. 3 fine filter of the spindle seal communicates normally with the PLC. All of the above conditions must be met simultaneously.

[0145] D6. Issue an alarm signal and exit the process.

[0146] D7. Execute the process of switching from fine filter #4 to fine filter #3 and start timing.

[0147] The specific steps for switching from fine filter #4 to fine filter #3 are as follows: The spindle sealing system slowly opens the inlet electric valve DF18 of the No. 3 fine filter. After the No. 3 fine filter inlet electric valve DF18 is fully open, it delays for 30 seconds and then closes the inlet electric valve DF19 of the No. 4 fine filter. At the same time, the operating status of the No. 4 fine filter is marked as pending cleaning. After the No. 4 fine filter inlet electric valve DF19 is completely closed, the industrial control computer human-machine interface displays a filter switching completion prompt.

[0148] D8. Determine whether, within 2 minutes of opening the inlet electric valve of the #3 fine filter, the inlet electric valve of the #4 fine filter is closed, the inlet electric valve of the #3 fine filter is open, and the inlet-outlet pressure difference P of the #3 fine filter is met. 03 If the pressure difference is greater than or equal to the normal operating pressure difference P0 and the duration is greater than 15s, proceed to step D9 if not, and proceed to step D10 if yes.

[0149] D9. Issue a switching timeout alarm signal, exit the process, and automatically resume operation of the #4 fine filter.

[0150] D10. Determine the inlet and outlet pressure difference P of the No. 4 fine filter. 04 If the pressure difference is greater than or equal to the preset cleaning differential threshold P2 and the duration is greater than 15s, proceed to step D11 if no, and proceed to step D13 if yes.

[0151] D11. Determine whether the #4 fine filter has reached the preset cleaning time threshold of 72h. If not, proceed to step D12; if yes, proceed to step D13.

[0152] D12. Continue monitoring the cumulative running time of the No. 4 fine filter since the last cleaning, and proceed to step D10.

[0153] D13. Perform cleaning on the #4 fine filter.

[0154] The specific cleaning steps are as follows: The spindle sealing system opens the backwash inlet electric valve DFFCX04 of the No. 4 fine filter and the drain electric valve DF21 of the No. 4 fine filter to flush the filter element impurities using reverse water flow. During the backwashing process, the backwash water pressure is controlled to not exceed 1.2 times the normal operating water pressure of the spindle sealing system.

[0155] After a single cleaning cycle of the No. 4 fine filter lasts for 3 minutes, the backwash inlet electric valve DFFCX04 of the No. 4 fine filter is closed, while the drain electric valve DF21 of the No. 4 fine filter remains open for 30 seconds to remove residual wastewater from the No. 4 fine filter.

[0156] The spindle sealing system shuts off the drain valve DF21 of the No. 4 fine filter, and the No. 4 fine filter is restored to standby status, awaiting the next commissioning.

[0157] D14. Determine the inlet and outlet pressure difference P of the #4 fine filter within the preset cleaning effect judgment period of 3 minutes. 04 If the voltage drops below the aforementioned switching differential threshold P1 and the duration is greater than or equal to the preset fifth delay threshold of 15 seconds, proceed to step D15 if no, and proceed to step D16 if yes.

[0158] D15. Issues a severe filter blockage alarm signal, exits the cleaning process, and sends a filter replacement reminder message.

[0159] D16. The industrial control computer's human-machine interface has been successfully cleaned. Set the cumulative running time of the #4 fine filter to 0 and exit the process.

[0160] Secondly, embodiments of this application also provide a switching and cleaning device for a turbine main shaft sealing filter.

[0161] In one embodiment, see Figure 12As shown, the aforementioned turbine main shaft seal filter switching and cleaning device includes a switching module and a cleaning module, specifically: The switching module is used to switch the first filter to the second filter when the hydro-generator unit is in a stable operating state, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to a preset switching pressure difference threshold and the duration is greater than a preset first delay threshold, and the standby second filter is available.

[0162] The cleaning module is used to perform cleaning immediately after a successful switch if the inlet and outlet pressure difference of the first filter is greater than or equal to a preset cleaning pressure difference threshold and the duration is greater than a preset second delay threshold; otherwise, cleaning is performed when the first filter reaches a preset cleaning time threshold.

[0163] The technical solution of this application can produce the following technical effects: It achieves intelligent identification and automatic switching of filter blockage faults. By monitoring the inlet and outlet pressure difference and duration in real time, combined with the self-check of the backup filter's OK condition, it automatically switches filters when the pressure difference continues to exceed the standard, avoiding the subjectivity and lag of manual judgment, reducing the fault response time from hours to minutes, and ensuring the continuity of the main shaft's sealed water supply.

[0164] A dual cleaning trigger mechanism based on the degree of clogging and operating time was constructed. It differentiates between immediate cleaning and timed cleaning strategies based on the degree of differential pressure exceeding the limit. This not only restores filter performance immediately when the filter is severely clogged, but also prevents gradual clogging accumulation through preventative cleaning based on accumulated operating time. This upgrades the operation and maintenance mode from passive response to proactive prevention, extends filter life, and reduces maintenance costs.

[0165] A closed-loop safety management system for the switching and cleaning processes has been established. By setting switching timeout protection, multiple judgments for successful switching, cleaning effect verification, and automatic recovery mechanisms, it is ensured that the system can automatically return to a safe state under any abnormal circumstances, avoiding the risk of water supply interruption due to switching failure. At the same time, through real-time water pressure monitoring and priority protection strategies, the stability of the spindle seal water supply is always the top priority during the cleaning process.

[0166] It enables precise management and predictive maintenance of filter cartridge life. Through a cumulative running time reset mechanism and cleaning effect assessment, a digital archive of filter cartridge health status is established, providing objective data support for filter cartridge replacement; when cleaning cannot restore filter cartridge performance, a replacement reminder is automatically pushed, avoiding resource waste caused by over-cleaning or sudden failures caused by filter cartridge failure.

[0167] This approach enhances the overall automation and intelligence level of the main shaft sealing system in hydropower stations. The integrated method can automatically control the entire process of filter switching, cleaning, and verification, reducing the workload of maintenance personnel, eliminating the risk of human error, and enabling the main shaft sealing system to possess self-sensing, self-diagnosis, self-decision-making, self-execution, and self-adaptive capabilities, aligning with the development direction of smart hydropower station construction.

[0168] It should be noted that the sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0169] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0170] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0171] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0172] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0173] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device to execute the methods described in the various embodiments of this application.

[0174] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for switching and cleaning a turbine main shaft sealing filter, characterized in that, The method includes: When the hydro-generator unit is in stable operation, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to the preset switching pressure difference threshold and the duration is greater than the preset first delay threshold, and the standby second filter is available, the first filter will be switched to the second filter. After a successful switch, if the inlet and outlet pressure difference of the first filter is greater than or equal to the preset cleaning pressure difference threshold and the duration is greater than the preset second delay threshold, cleaning is performed immediately; otherwise, cleaning is performed when the first filter reaches the preset cleaning time threshold.

2. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, The switching differential pressure threshold is set according to the maximum allowable flow resistance of the filter element; The first delay threshold and the second delay threshold are set according to the hydraulic fluctuation period of the spindle sealing system; The cleaning differential pressure threshold is set based on the effectiveness of the filter element backwashing; the cleaning time threshold is set based on the average clogging cycle of the filter element under given water quality conditions.

3. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, The step of switching the first filter to the second filter includes: The inlet electric valve of the second filter is opened until the preset third delay threshold is reached, and the inlet electric valve of the first filter is closed to complete the switching operation. The third delay threshold is set based on the settling time of the water flow in the pipes and filters.

4. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, The criteria for determining a successful switch are: opening the inlet electric valve of the second filter and timing it; within the preset switch timeout threshold, the following conditions are met: the inlet electric valve of the first filter is closed, the inlet electric valve of the second filter is open, and the pressure difference between the inlet and outlet of the second filter is greater than or equal to the normal operating pressure difference and the duration is greater than the preset fourth delay threshold. The switching timeout threshold is set based on the sum of the full stroke time of the second filter inlet electric valve actuator, the time required for hydraulic stabilization, and the time for confirming differential pressure stabilization; the fourth delay threshold is set based on the stabilization time required for the main shaft sealing system to achieve dynamic equilibrium after the switching is completed.

5. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, If the cumulative running time of the first filter since the last cleaning is greater than or equal to the cleaning time threshold, the first filter is switched to the second filter and cleaning is performed immediately.

6. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, The cleaning includes: Open the backwash inlet electric valve and the drain electric valve of the first filter to flush the filter element using reverse water flow; If a single cleaning cycle reaches the preset cleaning time, the backwash water inlet electric valve is closed; the cleaning time is set according to the shortest time required for filter element regeneration determined by the backwash effectiveness test. Maintain the sewage discharge electric valve open for a preset sewage discharge delay, and close the sewage discharge electric valve after the sewage discharge delay ends; the sewage discharge delay is set according to the filter cavity volume and the flow capacity of the sewage discharge pipeline.

7. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, If, within the preset cleaning effect judgment period, the inlet and outlet pressure difference of the first filter drops below the switching pressure difference threshold and the duration is greater than or equal to the preset fifth delay threshold, the cleaning is determined to be successful, and the cumulative running time of the first filter since the last cleaning is reset to zero. The fifth delay threshold is set according to the time required for the hydraulic pressure to stabilize after the filter cleaning is completed.

8. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, If the water pressure of the spindle sealing system deviates from the preset stable operating range during the cleaning process, the cleaning process shall be suspended. The stable operating range is set based on the rated pressure of the spindle sealing system and its allowable percentage fluctuation.

9. The method for switching and cleaning the turbine main shaft sealing filter as described in claim 1, characterized in that, If the water pressure in the spindle sealing system is lower than the preset water pressure threshold during the switching or cleaning process, the current process is paused. The water pressure threshold is set according to the minimum water supply pressure required for the safe operation of the spindle sealing device.

10. A switching and cleaning device for a turbine main shaft sealing filter, characterized in that, The device includes: The switching module is used to switch the first filter to the second filter when the hydro-generator unit is in a stable operating state, if the inlet and outlet pressure difference of the currently operating first filter is greater than or equal to a preset switching pressure difference threshold and the duration is greater than a preset first delay threshold, and the standby second filter is available. The cleaning module is used to perform cleaning immediately after a successful switch if the inlet and outlet pressure difference of the first filter is greater than or equal to a preset cleaning pressure difference threshold and the duration is greater than a preset second delay threshold; otherwise, cleaning is performed when the first filter reaches a preset cleaning time threshold.

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