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									              INSTRUMENTATION

PRESSURE MEASUREMENT:

TWO Nos. PRESSURE TRANSMITTERS PROVIDED IN THE
UPSTREAM OF HP BYPASS PRESSURE CONTROL VALVES, IN
THE MAIN STEAM LINE.
RANGE : 0 TO 200 kg/sq.cm

TEMPERATURE MEASUREMENT:

TWO Nos. K-TYPE DUPLEX THERMOCOUPLES ARE PROVIDED
IN EACH LINE, LOCATED AT THE DOWNSTREAM OF EACH HP
BYPASS PRESSURE CONTROL VALVES.
RANGE : 100 TO 450°C.
                PROCESS MONITORING

PRESSURE / TEMPERATURE MEASUREMENT:


The 4 to 20 mA analog signals received from the Pressure

transmitters and the mV signals received from Thermocouples

are digitally processed in the DCS. These signals are monitored

to generate internal and external digital signals for interlocks

and alarm generation.
          ALARMS, INTERLOCKS and
              PROTECTION
ALARMS:
The following are the main Alarms generated in the system:
• Pressure/Temperature transmitters failure.
• Main steam pressure too high.
• Downstream temperature high/very high.
• Tracking Pressure set point failure.
• Pressure control valves opened more than 2%.
• Pressure control valves closed less than 2%.
• Hydraulic Oil pressure too low.
• Any fast opening criteria operated.
• Any closing criteria operated.
          ALARMS, INTERLOCKS and
              PROTECTION
INTERLOCKS:
The following are the important interlocks provided in the
system:
• When the Pressure control valves are closed less than 2% and
  in Manual mode, a forced close signal is provided to prevent
  the valve from drift open.
• When the Main steam pressure is too high, then the Fast
  opening device is activated.
• Whenever the pressure control valve is opened more than
  2%, then the associated Spray control valve will switchover
  to Auto mode, if it was in Manual mode before.
• When the system is in auto mode and if the process signal is
  failed, then the associated control loop will be switched to
  manual mode.
          ALARMS, INTERLOCKS and
              PROTECTION
PROTECTION:
The following are the important interlocks provided in the
system:

• When the down stream temperature of Pressure control valves
  is too high or when the condenser vacuum is low, then the
  Pressure control valves are closed on priority.

• When the Turbine trips or when the Generator CB is open,
  the opening device is activated to prevent Boiler trip.
  HP / LP BYPASS SYSTEM
                                         HRH

                           MSL




                      BP

           BOILER                         HPT               MPT                 LPT



                                       CRH NRV
                     CRH
                                                 LBP                LPC         CO
                                                                                N

                                 BPE

                                                                          LBP
                                                                          E
                                 BD




                                           BFP
LEGEND
   BP : HP BYPASS VALVE          BD :    HP SPRAY ISOLATION VALVE   CON : CONDENSOR
   LBP: LP BYPASS VALVE          BPE :   HP SPRAY VALVE             LBPE : LP SPRAY VALVE
   BFP: BOILER FEED PUMP         CRH :   COLD REHEAT LINE             LPC : LP COOLER
   HPT: HIGH PRESSURE TURBINE    HRH :   HOT REHEAT LINE              LPT : LOW PR. TURBINE
   MSL: MAIN STEAM LINE          MPT :   MEDIUM PR. TURBINE
HP BYPASS CONTROL SCHEME
            MAIN STEAM LINE         To TURBINE



      P
  =                                          BD
                              TEMPERATURE
                                SET POINT
                                 STATION



            MASTER
                                             BPE
           PRESSURE
          CONTROLLER



PRESSURE
SET POINT                              =         TEMPERATURE
 STATION                           T             CONTROLLER
                    To CRH
Reheater Protection Logic

								
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