CN-116906129-B - Automatic control method for shaft seal system of steam turbine under full-automatic load shedding working condition

Abstract

A control strategy of a steam turbine shaft seal system under a full-automatic load shedding working condition comprises the following steps of A, a shaft seal steam supply regulating valve control strategy, B, a shaft seal overflow valve control strategy, C, a shaft seal steam supply temperature reduction water regulating valve control strategy, and D, a shaft seal main pipe drain gate control strategy, wherein after load shedding or FCB triggering, the shaft seal steam supply regulating valve is firstly opened to a certain opening degree and then the shaft seal pressure is thrown automatically, B, a shaft seal overflow valve control strategy is used for cutting manually and automatically giving an instruction to 0%, C, a shaft seal steam supply temperature reduction water regulating valve control strategy is used for cutting manually and automatically giving an instruction to 0%, and D, a shaft seal main pipe drain gate control strategy is used for automatically cutting open after load shedding or FCB triggering. The invention is successfully applied to millions of units, 75% FCB and 100% full-automatic load shedding test of the units are successful once, and the units after the test is completed have the condition of quick grid connection and load carrying, thereby completely meeting the requirements of safe and stable operation of the units.

Inventors

• LU SHUANGLONG
• ZHANG BIAO
• LIU HAIMING
• LI YANGHAI
• YUE LIANG
• LI LU
• XU YAN

Assignees

• 国网湖北省电力有限公司电力科学研究院

Dates

Publication Date

20260512

Application Date

20230508

Claims (2)

1. 1. The automatic control method of the turbine shaft seal system under the full-automatic load shedding working condition is characterized by comprising the following steps of: A. control strategy of shaft seal steam supply regulating valve After load shedding or FCB triggering, the shaft seal steam supply regulating valve is firstly linked to a certain opening degree, and then the shaft seal throwing pressure is automatic; B. Shaft seal overflow valve control strategy After load shedding or FCB triggering, the shaft seal overflow valve is manually cut, and an instruction is automatically given to 0%; C. Shaft seal steam supply temperature reduction water regulating door control strategy After load shedding or FCB triggering, the shaft seal steam supply and temperature reduction water regulating gate switch is operated manually and automatically to give an instruction to 0%; D. Control strategy for main pipe drain door of shaft seal After load shedding or FCB triggering, the main shaft seal drain door is automatically opened; in the control strategy of the shaft seal steam supply regulating valve, a shaft seal steam supply pressure function is used as a combined opening setting value of the shaft seal steam supply regulating valve; In the control strategy of the shaft seal steam supply regulating valve, the shaft seal steam supply pressure function is obtained in a mode that the machine set is provided with 3-5% of rated load, and the shaft seal main pipe water drain door is fully opened, and on the premise that the normal pressure of the main pipe of the shaft seal system is met, the opening values of the shaft seal steam supply regulating valves corresponding to different shaft seal steam supply pressures are obtained.
2. 2. The automatic control method for the steam turbine shaft seal system under the full-automatic load shedding working condition of claim 1 is characterized in that in a shaft seal steam supply regulating valve control strategy, a shaft seal steam supply regulating valve is always in an automatic control mode, a shaft seal pressure set value is a recommended value of a main engine plant or an empirical value of a unit under the long-time operation working condition, when the FCB is reset, the shaft seal steam supply regulating valve is still in the automatic control mode, and a pressure set value is kept unchanged, and at the moment, the pressure set value is manually modified or cut to a manual control mode.

Description

Automatic control method for shaft seal system of steam turbine under full-automatic load shedding working condition Technical Field The invention relates to the field of control of thermal power generating units, in particular to an automatic control method of a turbine shaft seal system under a full-automatic load shedding working condition. Background FCB (Fast Cut Back) is a scheme provided for the purpose that a unit can be quickly started to be connected after a severe fault of a power grid, and when the power grid has an emergency fault, the unit is quickly disconnected from the power grid and enters a island operation mode, a boiler maintains stable combustion, a steam turbine maintains 3000r/min, and a generator operates with a power load for a plant. When the power grid is recovered to be normal, the power grid can be rapidly connected and supplied to important users of the power grid under the condition of power grid dispatching permission, and the method has very important significance in the aspect of ensuring the safety and stability of the power grid. The FCB test is used as a test item with the greatest risk and highest difficulty of the thermal power generating unit, although the FCB of the thermal power generating unit is successful, the successful cases of the high-load FCB test are not more, the successful cases of the high-load FCB of the million units are less, and 100% of the successful cases of the full-automatic load dump test are not yet seen. The main reason is that when the unit enters the FCB working condition from the normal operation mode, each operation parameter will change drastically, and higher requirements are put forward on the operation of each main auxiliary equipment, so that the test failure is very easy to happen due to a little carelessness, and even equipment damage accidents such as water inlet of a steam turbine, abnormal vibration of the unit, overpressure of a boiler, power consumption loss of a plant, fuel cut-off and tile burning occur. The special requirements of FCB and load shedding test overall process automatic control, which are proposed by some business units, are further increased in test difficulty, and meanwhile, higher requirements are also provided for automatic control strategies of all main and auxiliary equipment. The shaft seal system is an important component part of the steam turbine, and has the main function of providing sealing steam for the shaft seal of the steam turbine, and whether the operation parameters of the shaft seal system are normal or not directly influences the safe and stable operation of the main engine. During normal operation of the unit, the pressure and the temperature of the shaft seal system are not large, and the safety and the economical efficiency of the main engine are not greatly influenced. However, after the unit enters the FCB working condition, the shaft seal steam source is switched to an external steam source for steam supply by self-sealing, at the moment, the shaft seal pressure is greatly fluctuated, the shaft seal temperature is greatly reduced, at the moment, the shaft seal parameters are difficult to be rapidly controlled in a normal range in a short time by a conventional control means, the abnormal phenomena of vacuum reduction, dynamic and static friction, abnormal vibration of the unit, water carrying of a lubricating oil system and the like of the condenser are very easy to occur, and serious accidents such as steam seal abrasion, rotor/journal/blade damage, tile burning and the like of the unit are even caused by the tripping of protective action due to the low vacuum and the large vibration of the condenser. Therefore, the automatic load shedding or FCB test of the thermal power generating unit can be successful, and the automatic control strategy of the turbine shaft seal system is particularly critical. Disclosure of Invention The invention mainly solves the defects existing in the prior art, and provides the automatic control method for the turbine shaft seal system under the full-automatic load shedding working condition, which not only can achieve the aims of automatically controlling the turbine shaft seal system to quickly and stably tend to meet the normal operation of a unit, but also can avoid the risks of accidents such as abnormal vibration, dynamic and static friction and the like of the turbine caused by the excessively low shaft seal temperature, improves the full-automatic load shedding and FCB success rate of the thermal power unit, and provides favorable conditions for quick grid connection of the unit. An automatic control method of a turbine shaft seal system under a full-automatic load shedding working condition comprises the following steps: A. control strategy of shaft seal steam supply regulating valve After load shedding or FCB triggering, the shaft seal steam supply regulating valve is firstly linked to a certain opening degree, and then the shaft seal throwing pre