Reprint--[Technical Information] 1000MW Unit RUN BACK and Processing

Source: Power Generation Operation Safe House

1. Definition of RB

At least 4 layers of coal feeders are in operation and the load is greater than 55% BMCR, and the rapid load shedding occurs due to the failure of the boiler or steam turbine main auxiliary unit tripping.

2. Types of RB

1. In the COORD mode, one of the two blowers trips when running, and the load is automatically reduced to 500MW.

2. In the COORD mode, one of the two induced draft fans trips when it is running, and the load is automatically reduced to 500MW.

3. In the COORD mode, one of the two primary wind turbines trips when running, and the load is automatically reduced to 500MW.

4. In the COORD mode, one of the two air preheaters trips when it is running, and the load is automatically reduced to 500MW.

5. In COORD mode, one of the two steam pumps trips when running, and the load is reduced to 500MW.

6. Coal mill tripping RB.

3. RB caused by the tripping of the blower or induced draft fan

1. Phenomenon

(1) The corresponding fan trips and the "RB" sound and light alarm on the alarm screen, and the corresponding fan has tripped on the CRT.

(2) A blower (or induced draft fan) in operation trips, and the opposite side induced draft fan (or blower) is tripped.

(3) The unit load command is rapidly reduced to 500MW at a rate of 1000MW/min.

(4) Keep three mills running, and the rest of the mills are interlocking tripping, and the jumping grinding sequence is C, E, F, and the time interval is 10s.

(5) The negative pressure of the furnace fluctuates, the steam flow decreases, and the generator power decreases.

2. Causes

When two blower or induced draft fan are running, one trips.

3. Processing

(1) Confirm that the control mode of the unit is automatically switched to TF.

(2) Confirm that the side induced draft fan (or induced draft fan) corresponding to the tripped blower (or induced draft fan) is interlocked and tripped, and the relevant baffle interlock of the tripped fan is closed normally.

(3) Check the operation of the blower, blower adjustment baffle or moving blade automatically open, pay attention to the current within the rated value, check the furnace negative pressure, boiler total air volume and other parameters.

(4) Due to the tripping of the coal mill and the fluctuation of its coal volume, the primary air volume changes drastically, pay attention to monitoring the changes in the wind pressure of the mother pipe and the operation of the primary fan.

(5) Check the CCS load command to reduce to the corresponding value, and confirm the rapid action of the high-pressure valve adjustment of the steam turbine to maintain the consistency between the main steam pressure and the sliding pressure curve.

(6) Confirm that only three mills are kept running, the other mills have been interlocked and tripped, and the fuel quantity corresponds to the load instruction, pay attention to the changes in the water-fuel ratio and the steam temperature at the outlet of the roof superheater, monitor and adjust the temperature of the main and reheated steam, and prevent the serious imbalance of the water-fuel ratio from causing large fluctuations in steam pressure and steam temperature.

(7) Pay attention to the combustion conditions, and put in the oil gun to support combustion if necessary. If the coal mill B is running, the plasma ignition device can be put into stable ignition.

(8) Check that the desuperheating water regulating valve of the first and second stage superheaters is automatically closed, confirm that the reheating steam temperature adjustment is normal, and monitor the temperature of the main and reheated steam.

(9) Check that the water level adjustment of the deaerator, the steam pressure and temperature of the shaft seal are normal, and the parameters such as the vibration of the host are within the normal range.

(10) When the RB condition occurs, when the load of the unit is 550MW and above, it should be confirmed that the FGD bypass baffle is open normally.

(11) Contact maintenance, find out the cause of the fault as soon as possible, restart the tripping equipment after the fault is eliminated, and restore the normal operation of the unit.

Fourth, a fan tripping causes RB

1. Phenomenon

(1) On the alarm screen, the sound and light alarm of "primary fan tripping" and "RB" will be displayed, and a primary fan will be tripped on the CRT.

(2)机组负荷指令以1000MW/min快速降至500MW。

(3) Keep three mills running, and the other mills are interlocking and tripping, and the jumping grinding sequence is C, E, F, and the time interval is 10s.

(4) The primary wind pressure fluctuates, the steam flow decreases, and the generator power decreases.

2. Causes

One of the two primary fans trips when it is running.

3. Processing

(1) Confirm that the control mode of the unit is automatically switched to TF.

(2) Confirm that the tripping primary fan outlet baffle and moving blade are closed, and the operating primary fan blade will automatically open large, pay attention to the current is less than the rated value, and check that the primary wind pressure is within the normal range.

(3) Confirm that the three mills are retained, the other mills have been interlocked and tripped and automatically isolated, the amount of fuel corresponds to the load instruction, pay attention to the change of the fuel/water ratio and the outlet steam temperature of the roof superheater, monitor and adjust the temperature of the main and reheat steam, and prevent the serious imbalance of the fuel/water ratio from causing large fluctuations in steam pressure and steam temperature.

(4) Pay attention to the combustion conditions, and put in the oil gun to support combustion if necessary. If the coal mill B is running, the plasma ignition device can be put into stable ignition.

(5) Check that the CCS load command is reduced to the corresponding value, and the steam turbine valve is quickly closed to maintain the main steam pressure and the sliding pressure curve.

(6) Check that the desuperheating water regulating valve of the first and second superheaters is automatically closed. If necessary, close the electric isolation valve for the desuperheating water of the primary and secondary superheaters. Confirm that the reheat steam temperature adjustment is normal.

(7) Check that the water level adjustment of the deaerator, the steam pressure and temperature of the shaft seal are normal, and the parameters such as the vibration of the host are within the normal range.

(8) If the RB condition occurs, when the load of the unit is 550MW and above, it should also be confirmed that the FGD bypass baffle is quick to open.

(9) Contact maintenance, find out the cause of the fault as soon as possible, restart the tripping equipment after the fault is eliminated, and restore the normal operation of the unit.

5. RB caused by air preheater tripping

1. Phenomenon

(1) On the alarm screen, the main motor and standby motor of the faulty air preheater are tripped.

(2) The corresponding side supply and induced draft fan will trip if the cold secondary air contact baffle is closed, otherwise the output force will be automatically reduced; the corresponding side primary fan will trip if the cold primary air contact baffle is closed, otherwise the output force will be automatically reduced.

(3) The secondary air side, the primary air side inlet and outlet baffle of the tripping air preheater are interlocked and closed.

(4) The flue gas inlet baffle and the electrostatic precipitator outlet baffle of the tripping air preheater are interlocked and closed, and the corresponding side of the electrostatic precipitator trips.

(5) Keep three mills running, and the other mills are interlocking and tripping, and the jumping grinding sequence is C, E, F, and the time interval is 10s.

(6) The pressure of the primary and secondary mother pipe decreases, and the outlet pressure of the fan rises.

(7) The negative pressure of the furnace and the fluctuation of the primary wind pressure decrease the steam flow rate and the power of the generator.

2. Processing

(1) Confirm that the control mode of the unit is automatically switched to TF

(2) Confirm the tripping or automatic reduction force of the feeding, induced draft fan and primary fan on the corresponding side of the tripping air preheater, closely monitor the sending and induced draft fan, and the operating conditions of the primary fan, prevent stalling, and pay attention to the wind pressure and negative pressure in the furnace.

(3) Confirm that the tripping air preheater corresponds to the tripping of the electrostatic precipitator, the flue gas inlet baffle, the electrostatic precipitator outlet baffle, and the secondary wind side, the primary wind side inlet and the outlet baffle are interlocked and closed.

(4) Check that the CCS load command is reduced to the corresponding value, and the steam turbine valve is quickly closed to maintain the main steam pressure consistent with the sliding pressure curve.

(5) Confirm that the corresponding coal mill has been interlocked and tripped, keep three mills running, and reduce the load to 500MW. The amount of fuel corresponds to the load directive, pay attention to the change of the fuel/water ratio and the outlet steam temperature of the roof superheater, monitor and adjust the temperature of the main and reheated steam, and prevent the serious imbalance of the fuel/water ratio from causing large fluctuations in steam pressure and steam temperature.

(6) If the RB condition occurs, when the load of the unit is 550MW and above, it should also be confirmed that the FGD bypass baffle is open normally.

(7) Confirm that the LCS sector plate of the tripping air preheater has retreated to the highest position, and the rest will be treated as the air preheater stops.

(8) Contact the maintenance, find out the cause of the air preheater failure as soon as possible, and restart the tripping equipment after the fault is eliminated.

6. "RB caused by feed pump tripping"

1. Phenomenon

(1) The pump trips and "RB" sound and light alarm on the alarm screen, and the corresponding pump trips is displayed on the CRT.

(2) The coal mill retains three units of operation, and the other mills are interlocked and tripped, and the jumping grinding sequence is C, E, F, and the time interval is 10s.

(3) The negative pressure of the furnace, the primary air pressure, the main and reheat steam temperature and other parameters fluctuate, and the steam flow decreases.

2. Causes

Two running feedwater pumps, one tripped

3. Processing

(1) Confirm that the unit controls the automatic switching to TF mode.

(2) Confirm that the interlocking action of the tripping pump is correct and the speed of the small machine decreases;

(3) Pay attention to the changes in the fuel/water ratio and the outlet steam temperature of the roof superheater, monitor and adjust the temperature of the main and reheated steam to prevent the serious imbalance of the fuel/water ratio from causing large fluctuations in steam pressure and steam temperature.

(4) Check that the CCS load command is reduced to the corresponding value, and the steam turbine valve is quickly closed to maintain the main steam pressure consistent with the sliding pressure curve.

(5) Check that the desuperheating water regulating valve of the first and second superheaters is automatically closed, and if necessary, close the electric isolation valves of the desuperheating water of the primary and secondary superheaters. Confirm that the reheat steam temperature adjustment is normal.

(6) Check that the vibration, axial displacement, oil temperature and other parameters of the main engine bearing are within the normal range.

(7) Check that the water level of the deaerator, the steam parameters of the shaft seal, the sealing water system of the steam pump and other parameters are normal.

(8) When the RB condition occurs, it should also be confirmed that the FGD bypass baffle is opening normally.

(9) Contact the maintenance, find out the cause of the fault, restart the tripping equipment after the fault is eliminated, and restore the normal operation of the unit.

7. RB caused by coal mill tripping

When three mills are running and the unit load ≥ 400MW, one of the mills trips with a load of 400MW.

When the load of the four mill operation units ≥ 600MW, one of the mills trips with a load of 600MW.

When the load of the five mill running units ≥ 800MW, one of the mills trips with a load of 800MW.

1. Phenomenon

(1) On the alarm screen, the coal mill trips and the "RB" sound and light alarm, and the corresponding coal mill trips are displayed on the CRT.

(2) If the operation mode of the unit is in COORD mode, the load command will be quickly reduced to the corresponding value at 1000MW/min.

(3) The steam flow decreases and the generator power decreases.

2. Causes

The corresponding running coal mill tripped.

3. Processing

(1) Check that the CCS load command is reduced to the corresponding value, and the steam turbine valve is quickly closed to maintain the main steam pressure consistent with the sliding pressure curve.

(2) Confirm that the tripping mill has been automatically isolated, and the operating mill parameters are normal.

(3) Pay attention to the changes in the combustion conditions of the boiler, the water-fuel ratio, and the outlet steam temperature of the roof superheater, and monitor and adjust the temperature of the main and reheated steam.

(4) Check that the desuperheating water regulating valve of the first and second superheaters is automatically closed. If necessary, close the electric isolation valve for the desuperheating water of the primary and secondary superheaters. Confirm that the reheat steam temperature adjustment is normal.

(5) Check that the water level adjustment of the deaerator, the steam pressure and temperature of the shaft seal are normal,

(6) Check that the vibration, axial displacement and other parameters of the host are within the normal range.

(7) Contact maintenance, find out the cause of the fault as soon as possible, restart the tripping equipment after confirming that the fault is eliminated, and restore the normal operation of the unit.