APLICACIÓN DE LA PROPUESTA DE SISTEMA PARA ARMONIZAR LA

9.1 General statement of DEH system

DEH-steam turbine digital electric hydraulic control system adopts the I/A hardware manufactured by FOXBORO company and uses HP fire resistant oil as its hydraulic pressure part, and the governing valve is directly controlled by DEC with electro-hydraulic converter.

9.2 Structure of DEH System

With the operation of OPC solenoid valve and OPC oil way, HP oil system can realize overspeed protection, and with the operation of diaphragm valve and safety oil interface, it can realize valve fast closing as shutdown. That is the DEH system structure.

9.3 DEH operator station is to perform various operations and image operation with the assistance of CRT picture, mouse, and keyboard. The main functions include:

Speed control: the operator realizes synchronous speed via turning speed according to the target value and speed-up rate.

Overspeed protection test: perform OPC overspeed test under the control of DEH, moreover, and it also has load rejection forecasting function.

Load control: after incorporating into network, DEH can realize the control of load and load variation rate.

Automatic quasi-synchronization: At synchronous speed, it receives the increasing and decreasing signal of “Automatic quasi-synchronization” device to accomplish unit paralleling and paralleling off.

Remote control function: it receives the load command of MCS (analog value control) system to realize coordination control.

Other functions: ATC control, valve position limit, lower limit of main steam pressure, high load limit, steam extraction control, primary frequency modulation, and manual control, etc.

9.4 Conditions of steam turbine latching

Starting oil pump and EH oil pump operate normally and oil pressure is normal;

Manual shutdown is on the Reset position;

9.5 DEH Control and Operation

9.5.1 Automatic control mode (OA)

Operator can perform reset by clicking the button “Reset” on manual operation panel, and after steam turbine is reset, main control panel will display “Latched”.

Click button “control mode” on top left of main control panel, and then sub picture of control mode will pop up, here can select a control mode for application. Click the button “OPERATOR AUTO”, afterwards click button “Put-in” within 3S, then auto control mode (OA) is put in, meanwhile, main panel displays equipment being in “OPERATOR AUTO” mode.

Operator click the button “Limit Value” on lower left of main control panel to pop up the sub window, then input valve position limit value, thereupon valve position limit will rising ceaselessly up to valve position limit value.

Click button “Control Set Value” to pop up sub picture, input the target speed (0~3,000rpm/min) into “target value” bar and the speed (0~500rpm/min) in “Speed” bar, afterwards click buttons

“ENTER” and “GO”, thereupon the set value will rise to target rotating speed according to the set speed, then with PID calculating, #1~4 (valve regulating control signal) will come into being that is transmitted to GV card to be transferred into current signal to drive electro hydraulic converter to start the GV, which rotating speed will rise thereupon.

In case of auto mode in on-load stage, operator can set target load (0~135MW) and run up rate (0~50MW/min) on rotating speed control sub picture through operating CRT, after click buttons

“ENTER” and “GO”, load set value will approach the target value step by step according to set load rate, and then vary #1~4 (adjust steam valve control output), and change load can through electro hydraulic converter operating hydraulic servomotor.

No matter it is the speed control stage or load control stage, once operator click button

“Maintain”, the rotary set value or load set value will maintain constant till operator press button

“GO”.

Attention: After latching, valve position limit must be opened before valve being opened.

9.5.2 Synchronization control mode (AS)

In auto mode, as rotating speed is close to 3, 000 r/min and self synchronization condition is met, operator can press the control mode button in top left of main control panel to pop out the sub picture, click synchronous button, afterwards click put-in button within 3s, then control will enter the synchronous mode, meanwhile main panel displays equipment has entered “AS” mode.

Then DEH will rise or decrease pulse according to the command received from electric aspect, turbine set value will change thereupon. Each pulse can rise or decrease the turbine set value by 1r/min, and with internal PID regulator, DEH can control turbine rotating speed to change thereupon, thus makes turbine rotating speed be synchronous with network.

After synchronization, DEH will let turbine load on 5% initial load automatically. In the meanwhile, AS mode will disengage automatically and transfer back to OA mode.

9.5.3 Put-in and trip of power loop (MW IN, MW OUT)

In on load operation, operator can select to put power loop feedback into operation: operator can click the button “Feedback state” on lower left of main control panel to pop up the sub picture, then click button “power loop”, afterwards click “put-in” button within 3S, then control will enter the power loop put-in mode, meanwhile the main panel displays device has entered to “Power loop IN” mode,

After power loop feedback put-in, load signal will enter controller as feedback signal to control load to be identical with set value (undisturbed switch). Prior to power feedback put-in, DEH is in open-loop control, and there is certain difference between load set value and load, which is decided by the current main steam pressure, if main steam pressure is the rated value, load set value will be close to the load value.

Generally, operator shall select the power loop clearing mode in order to ensure the initial steam pressure stable and boiler combustion adjustment stable. That is because after power feedback put-in, when main steam pressure fluctuates, valve opening will vary thereupon to guarantee developed power being identical with the load set value, and that vibration will accelerate vibration of boiler outlet pressure, but in order to guarantee load steady, power loop put-in is necessary.

9.5. 4 Remote control mode (ADS)

In on load OA operation, and the “set value” is close to the “remote control set value”, operator can select to enter remote control mode: operator shall send out DEH remote control request, then press the button “Control mode” on top left of main control panel to pop up the sub picture, click button “Remote control”, afterwards click button “Put-in” within 3S, and then control will enter the ADS mode, meanwhile the main panel displays device has entered to “ADS” mode. At that time, load set value is under the control of CCS (Coordination control) system.

Attention: as entering OA mode, ADS mode will disengage automatically.

9.5.5 Initial steam pressure limit (TPL)

In on load OA operation, and initial steam pressure is higher than 90% rated pressure, operator can select the TPL (initial steam pressure limit) mode: operator can pressure the “Limit value” on lower left of main control panel to pop up the sub picture, then click button “Initial steam pressure

meanwhile the main panel will display the main steam pressure limit is “IN”

In the case of TPL mode, as initial steam pressure being lower than 90% rated pressure, load set value will decrease at a fixed rate. Shut down the control valve hydraulic servomotor can compensate the decrease of main steam, thus avoid initial steam pressure decrease being to large.

TPL mode also can be cleared on limit at sub picture: click the button “initial steam pressure restriction”, afterwards click button “Clear” within 3S, and then control will disengage from TPL mode.

9.5.6 Remote control initial steam pressure limit (RTPL)

In OA operation, and the initial steam pressure is larger than 90% rated pressure, operator can select the RTPL (Remote control initial steam pressure limit) mode: operator shall press the “limit value” on lower left of the main control panel to pop up the sub picture, then click button “Remote control initial steam pressure limit”, afterwards click button “Put-in” within 3S, and then control will enter the RTPL mode, meanwhile, the main panel will display the Remote control initial steam pressure limit being “IN”

In RTPL mode, and the initial steam pressure is lower than 90% rated pressure, load set value will decrease at a fixed rate. Shut down the control valve hydraulic servomotor can compensate the decrease of initial steam, thus avoid initial steam pressure decrease being to large.

RTPL mode also can be cleared on limit sub picture: click button “Initial steam pressure restriction”, afterwards click “Clear” button within 3S, and then control will disengage from TPL mode.

9.5.7 Load limit (HLL) mode

In on-load OA operation, operator also can select high load limit mode: operator can press the button “limit value” on lower left of main control panel to pop up the sub picture, then input the load set value in high load limit mode area, afterwards click button “High load limit”, and click button “Put-in” within 3S, control will enter the high load limit mode thereupon, meanwhile the main panel will display “IN”. In case of high load limit mode, set value will not exceed the load limit value.

High load limit mode also can be tripped on limit value sub picture: click button “High load limit”, and then click button “Clear”, control will disengage from the high load limit mode thereupon.

9.5.8 Valve position limit mode (VPL)

In OA operation, operator also can select the valve position limit mode: operator can click the button “limit value” on lower left of main control panel to pop up the sub picture, click “valve position limit”, then input valve position limit value in valve position limit mode area, afterwards

click button “GO”, here valve limit value will enter the DEH control logic. In case of valve position limit mode, valve command will not exceed the valve position limit value.

9.5.9 Single valve/ sequence valve (SIG/SEQ) mode

In case of OA operation, operator also can select SIGLE (single valve) or SEQ (sequence valve) operation mode: click the button “valve mode” on milled lower part of main control panel to pop up he side picture, click single valve (or sequence valve) and the two switching buttons (press switching button within 3S after clicking single valve button, and it will be effective if the two buttons being red synchronously.

In SIGLE mode, command of all the control valves is the same and all the control valves take part in control synchronously; in SEQ mode, four control valves will operate one after another according to a certain sequence. The switching time between two modes is about 3S so as to guarantee no disturbance of load in the whole switching process.

9.5.10 OPC mode (OPC MODE)

Moreover, there is OPC (overspeed protection control) function set in DEH, in case load of steam turbine is over 30%, and main oil switch of motor trips, at that time, with the function of solenoid valve, all the hydraulic servomotors of control valve will control oil pressure to unload, thereby closing all hydraulic servomotors of governing steams. With the quick close of hydraulic servomotor, rotating speed acceleration will be restrained, and if steam turbine rotating speed is lower than 103% rated speed, and it is already 7.5S after OPC operation, then solenoid valve will lose excitation and hydraulic servomotor will start to maintain normal operation for waiting for synchronization. If steam turbine rotating speed still is larger than 103% after 7.5S, the valve will not open until steam turbine speed is lower than 103%.

9.5.11 Manual (TM) mode

It also can enter the manual control mode in steam turbine operation. Pay attention that in manual operation, operator can change the set value (GVSPT/TVSPT) of control valve and main steam valve directly without the participation of DEH, and this is belonging to open loop operation, which is inappropriate to be used except rotating speed path fault, etc. special situation. The method for entering manual (TM) is as follows: press the manual button on manual control panel, if red lamp lights, that indicates device being in manual operation state, here operator can click the control mode button on top left of main panel to pop up the sub picture, and the manual state bar will display “IN”, meanwhile main panel will display device being in “TM”

mode.

In manual operation, operator can realize the control of steam turbine by controlling control valve set value directly with operating the “GVUP” “GVDN” buttons on manual operation panel, thereby change rotating speed and actual load.

valves.

9.6 Stimulation Test of DEH

DEH has a built-in simulator that can perform closed-loop simulation test to DEH when the turbine is in the state of rest.

It can stimulate control signals such as latching, synchronization, paralleling in and remote control signal, etc. to carry static test to verify the signals or functions and ensure the smoothness of impulsing.

Attention: this test can only be done by related personnel during outage and is forbidden in normal operation of turbine. After the test is finished, all the original parameter must be restored, otherwise a serious result may be caused; it is recommended to do this test in the engineer station.