Safe Operation Measures after Transforming Frequency Converter Speed ​​of Boiler Suction Fan in Junliangcheng Power Plant
2023-11-30 13:10:21
At the beginning of the late 1990s, the reliability of high-voltage frequency converters has reached a high level, and prices have gradually declined. Among them, frequency converters used for power plant boiler suction fans and blowers account for a large proportion. However, the application of high-voltage frequency converters also brings this problem to the safety of power production. According to investigations, due to inverter faults or other reasons that induce frequency converter tripping, boiler fire extinguishing or limited output of the unit may occur.
First, the transformation program Juntang City Power Plant No. 8 furnace suction fan frequency conversion speed control transformation, through the control system transformation, has adopted a comprehensive protection measures to ensure that the unit can run normally when the inverter fails.
The two suction fans of No. 8 boiler in Junliangcheng Power Plant are originally high and low speed two-speed operation modes. During frequency conversion control transformation, B suction fan still retains the high-speed and low-speed two-speed operation modes, and the A-suction fan is changed to high-voltage inverter for variable-speed operation. the way. A suction fan transformation wiring (Figure 1), the original high-speed switch into the inverter inlet switch (2DL), the original low-speed switch to do bypass switch (lDL), the new converter outlet switch (3DL).
Second, interlock protection measures (1) B suction fan original interlock logic unchanged.
(2) When the frequency converter is faulty, it will jump to the inverter inlet and outlet switches at the same time and alarm. When the frequency converter trips (inverter failure or any inverter trip, outlet switch trip) but the motor is normal, a suction blower automatically closes to a certain position, after a certain delay (4s), automatically close the bypass Switch, suction fan to work frequency, furnace negative pressure manually operated suction fan baffle to adjust.
(3) When the suction blower trips (the inverter and the bypass switch both trip) and the motor also fails, the bypass switch does not close automatically, and the suction fan damper automatically closes.
(4) Boiler suction fan interlocking logic: When the suction blower trips, the suction blower B automatically cuts into high-speed operation; When the suction blower B breaks, the suction blower automatically raises the speed to 100%; shut off the suction blower board.
Third, thermal transformation (1) Boiler normal operation, B suction fan for constant speed operation, a suction fan speed operation, adjust the air volume. (2) The furnace negative pressure auto-adjustment system is changed to the inverter speed regulation as a means to adjust the furnace negative pressure; (3) to retain the remote operation function of the suction baffle of the suction fans A and B; the normal operation is fully open; When adjusting the air volume manually.
Fourth, suction fan baffle opening and operating time When the frequency converter fails, the suction fan baffle opening and the speed before the inverter to determine the suction fan baffle opening. According to the test, when the B suction fan is running at a low speed and the baffle is fully opened, the opening of the baffle suction baffle can be calculated as follows:
When n≥100r/min, k=(a1-a2×n+a3×n2)×100%
When n<300r/min, k=O
Where k is the opening of the suction fan damper, and n is the rotation speed a1, a2, a3 of the inverter before the fault is the fitting coefficient.
The determination of the actuation time of the suction fan damper actuator: from the fault of the inverter to the closing of the bypass switch for about 4 s, the motor needs to run at full speed (3~4) s, in order to offset the increase of the air volume caused by the increase of the motor speed. The baffle should be closed to a predetermined position in almost the same time. Taking into account the volume of the boiler combustion passage, the flap closing time should be controlled at (10~15) s. In order to realize stable operation of quick action and operation adjustment when the fan baffle is faulty, the requirement for the actuator action of the fan baffle is that the action speed is fast in the fault state, and the operation speed is slow in normal operation so as to facilitate adjustment.
V. Operation Effect On March 4, 2004, the frequency converter suddenly failed. Figure 2 shows the operation record after failure. It can be seen from Figure 2 that the suction fan damper command is quickly turned off and the furnace pressure is rapidly negative, but with the suction fan inlet baffle off and back to normal level, the minimum furnace pressure is about -4 OPa.
First, the transformation program Juntang City Power Plant No. 8 furnace suction fan frequency conversion speed control transformation, through the control system transformation, has adopted a comprehensive protection measures to ensure that the unit can run normally when the inverter fails.
The two suction fans of No. 8 boiler in Junliangcheng Power Plant are originally high and low speed two-speed operation modes. During frequency conversion control transformation, B suction fan still retains the high-speed and low-speed two-speed operation modes, and the A-suction fan is changed to high-voltage inverter for variable-speed operation. the way. A suction fan transformation wiring (Figure 1), the original high-speed switch into the inverter inlet switch (2DL), the original low-speed switch to do bypass switch (lDL), the new converter outlet switch (3DL).
Second, interlock protection measures (1) B suction fan original interlock logic unchanged.
(2) When the frequency converter is faulty, it will jump to the inverter inlet and outlet switches at the same time and alarm. When the frequency converter trips (inverter failure or any inverter trip, outlet switch trip) but the motor is normal, a suction blower automatically closes to a certain position, after a certain delay (4s), automatically close the bypass Switch, suction fan to work frequency, furnace negative pressure manually operated suction fan baffle to adjust.
(3) When the suction blower trips (the inverter and the bypass switch both trip) and the motor also fails, the bypass switch does not close automatically, and the suction fan damper automatically closes.
(4) Boiler suction fan interlocking logic: When the suction blower trips, the suction blower B automatically cuts into high-speed operation; When the suction blower B breaks, the suction blower automatically raises the speed to 100%; shut off the suction blower board.
Third, thermal transformation (1) Boiler normal operation, B suction fan for constant speed operation, a suction fan speed operation, adjust the air volume. (2) The furnace negative pressure auto-adjustment system is changed to the inverter speed regulation as a means to adjust the furnace negative pressure; (3) to retain the remote operation function of the suction baffle of the suction fans A and B; the normal operation is fully open; When adjusting the air volume manually.
Fourth, suction fan baffle opening and operating time When the frequency converter fails, the suction fan baffle opening and the speed before the inverter to determine the suction fan baffle opening. According to the test, when the B suction fan is running at a low speed and the baffle is fully opened, the opening of the baffle suction baffle can be calculated as follows:
When n≥100r/min, k=(a1-a2×n+a3×n2)×100%
When n<300r/min, k=O
Where k is the opening of the suction fan damper, and n is the rotation speed a1, a2, a3 of the inverter before the fault is the fitting coefficient.
The determination of the actuation time of the suction fan damper actuator: from the fault of the inverter to the closing of the bypass switch for about 4 s, the motor needs to run at full speed (3~4) s, in order to offset the increase of the air volume caused by the increase of the motor speed. The baffle should be closed to a predetermined position in almost the same time. Taking into account the volume of the boiler combustion passage, the flap closing time should be controlled at (10~15) s. In order to realize stable operation of quick action and operation adjustment when the fan baffle is faulty, the requirement for the actuator action of the fan baffle is that the action speed is fast in the fault state, and the operation speed is slow in normal operation so as to facilitate adjustment.
V. Operation Effect On March 4, 2004, the frequency converter suddenly failed. Figure 2 shows the operation record after failure. It can be seen from Figure 2 that the suction fan damper command is quickly turned off and the furnace pressure is rapidly negative, but with the suction fan inlet baffle off and back to normal level, the minimum furnace pressure is about -4 OPa.
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