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The characteristics of large-scale unit units are that the machines, electricity, and furnaces form an organic whole in the production process. In addition, there are a large number of complex control systems and devices. Their mutual relations are very close. When some of these links fail, it will affect the safe operation of the entire unit. Serious failures may result in shutdowns and shutdowns, and even endanger equipment and personal safety. The function of the interlock protection of the electromechanical furnace is to connect the machine, the electricity, and the furnace through certain logic. When a certain part of the furnace fails, other parts will respond accordingly. The following figure shows the principle block diagram of the electromechanical furnace interlock protection system. 
Results after MFT operation: stop powder supply, backup power supply
Stop 1 #, 2 # powder remover
Interconnection superheater desuperheating water electric total door
Reheater desuperheating water electric total door
Reheater accident sprinkler electric total door 
Stop 1#--16# to powder machine
1#--16# primary air damper
Associated OFT protection action Accident handling after fire suppression in boiler MFT operation:
Because the 7#, 8#, and 9# (all 200MW) units of this plant have adopted the operation mode of the jumper generator after the boiler MFT operation (excluding the high boiler water level). 
Therefore, measures should be taken to ensure the safety of steam turbines and generators in the event of a boiler fire extinguishing accident. Generally, the following measures should be taken:
1. Boiler Fire Protection After the MFT is actuated, the boiler watcher shall immediately check and confirm that the switches for the pulverizing system and the oil system are in normal positions. 
2. The turbine operator should quickly and manually reduce the load to about 5 MW, and the generator should not be subject to reverse power. 
3. The electric watchman quickly pours the power from the factory to the backup power supply to ensure that the 6KVA and B sections do not lose power. 
4. Boiler watchers should immediately de-list the feedwater automatically and control the water level of the steam drum to ensure that the steam turbine is not damaged due to the high steam drum water level or the protection against steam flooding. The water level of the steam drum is low and a large amount of water is added to cause the steam drum. The temperature difference between the upper and lower walls increases. 
5. Boiler watchers should immediately check whether each water-reduction door is closed, otherwise it will be closed immediately. In order to slow down the main steam temperature and reheat steam temperature drop rate, if the main reheat steam temperature drops sharply within 50 minutes or more than 50 degrees C or the main reheat steam temperature drops to 450 degrees C, it cannot be recovered in time (indicated by the machine side single pipe Quasi-precision, and refer to the furnace side corresponding meter), should immediately perform a fault shutdown. 
6. The steam turbine operator should switch the steam supply from the shaft seal to the standby steam source, and exit the high steam turbine side to operate. 
7. Adjust the water level of the deaerator and condenser to normal. Check that the feed pump recirculation door is opened to ensure that the feed pump does not vaporize and does not switch off. 
8. Keep the generator seal oil pressure and hydrogen pressure normal. 
9. Keep the condenser vacuum normal. 
10. Find out the cause of the fire and eliminate it. After the furnace has been purged for 5 minutes, take a long command and restart the ignition. If the failure can not be eliminated, the unit is normally shut down for processing. 
Advantages of non-joint jumper generator after Boiler MFT operation:
1. The boiler shall take measures immediately after extinguishing the fire, using the waste heat of the boiler to generate steam to maintain the unit to maintain a lower load operation, and to resume the operation of the unit in a short period of time to avoid a shutdown accident. 
2. After the boiler MFT is actuated, it takes about 10 minutes from the identification of the cause to the recovery of the ignition, from the re-generation of the main steam to the main steam pressure, the temperature of the main steam, and the restoration of the operation before the accident.
What is RB(runback)?
When a part of the main auxiliary equipment of the boiler (such as induced draft fan, blower, feed pump, etc.) fails, in order to enable the unit to continue safe operation, the load of the boiler and the gas turbine generator must be quickly reduced. This method of dealing with faults is called the boiler's fast load shedding protection, that is, RB (runback). 
What this article says is the extension of RB. When the boiler MFT is extinguished, the jumper generator is not connected, which is the key issue to be discussed. 
At present, the interlocking protection design of many 200MW and 300MW coal-fired units in China is as follows: when the boiler MFT acts to extinguish the fire, it is connected with a gas-jumping machine to disassemble the generator. This design is relatively safe, but it is not conducive to the rapid recovery of the unit and has a great impact on the economic efficiency of the power generating unit. For this reason, some domestic 200MW, 300MW generating units modified the logic of the interlocking protection of the furnace, changed to: when the boiler MFT action fire extinguishing after the jump turbine, but quickly reduce the generator load, so that the unit in the boiler After the fire extinguishing, the operation of the lower load is maintained, and it is decided whether or not to disengage the generator set or the boiler with rapid ignition and load according to the fire-extinguishing condition of the boiler. It is understood that the power plants for the interlocking protection of turbines and furnaces are: Taiyuan No. 2 Thermal Power Plant (200MW), Henan Anyang Power Plant (300MW), Zhangjiakou Power Plant (300MW), Changchun No. 2 Thermal Power Plant (200MW), Henan Jiaozuo Power Generation (200MW) Factory, Xinxiang Power Plant and so on. 
In response to the issue of whether the boiler MFT acted after the fire extinguishing, the production technology department of the State Power Corporation once organized the relevant leaders, the Ministry of Health and Technology, the Safety Supervision Department, the North China Electric Power Design Institute, the Douhe Power Plant, the Qinhuangdao Thermal Power Plant, and Dagang Power Generation. Plants and other units discussed the issue; in September 2003, Datang Group Company convened power plants under the supervision of Zhengzhou, Henan Province to discuss and analyze the issue. The results of the two conference discussions all considered that: After a boiler fire is extinguished in the operation of the unit, the load is quickly reduced to maintain the low-load operation of the gas turbine generator set, and it is feasible to take measures to quickly restore the normal operation of the generator set. Many of the aforementioned power plants have modified the interlock protection of the furnace and have extensive experience in dealing with such accidents. A lot of facts prove that if the MFT action of the boiler is extinguished, if the accident is dealt with in time, the measures are perfect, and the operation is reasonable, not only can the unit's safety be guaranteed, but also the normal operation of the unit can be resumed relatively quickly. The following takes the Taiyuan No. 2 Thermal Power Plant as an example and combines practical explanations. Boiler MFT action is not associated with the reality of the jumper generator after extinguishing the fire. 
Thermal fire extinguishing protection MFT action is as follows:
In the following cases, the MFT action does not stop:
1. Loss all flames 2. Loses all fuels 3. Loses all induced draught fans 4. Loses all blowers 5. Furnace pressure is high in value 2. Furnace pressure is low in binary values ​​7. Drum water level is low in binary values ​​8. Manual MFT action
Under the following conditions, the MFT action will stop
The state takes about 15 minutes. It takes about 25 minutes to handle the entire accident. 
3, boiler fire extinguishing without jumper generator greatly reduced the operation of the turbine watchman. 
4. Because the time is short in the process, the influence of the thermal stress on the gas turbine body is less. 
5. It can reduce the various economic losses caused by the factory's shutdown due to fire. 
6. Extinguishing the machine without jumping can reduce the impact on the grid due to the accident. 
The conclusion is that the interlocking protection of the boiler and furnace is complex, and the actual conditions of each power generating unit are also different. Therefore, each power generating unit should be properly treated according to the actual situation, seriously handle the problems of interlock protection of the furnace, and ensure the safety of the unit and maximize the interests of the first power plant. .
Machine stove interlock concept: Drum water level high-value MFT operation stops the furnace at the same time to issue a "fail-to-stop" signal to the turbine to stop the steam turbine.