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HP Bypass System and Reheater Protection Logic. Supervisory and Monitoring Instrumentation. 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

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HP Bypass System and Reheater Protection Logic

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Hp bypass system and reheater protection logic

HP Bypass System and

Reheater Protection Logic


Hp bypass system and reheater protection logic

Supervisory and

Monitoring

Instrumentation


Hp bypass system and reheater protection logic

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.


Hp bypass system and reheater protection logic

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.


Hp bypass system and reheater protection logic

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.


Hp bypass system and reheater protection logic

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.


Hp bypass system and reheater protection logic

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 bypass system and reheater protection logic

HP / LP BYPASS SYSTEM

HRH

MSL

BP

LPT

BOILER

HPT

MPT

CRH NRV

CRH

LPC

CON

LBP

BPE

LBPE

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

HP BYPASS CONTROL SCHEME

MAIN STEAM LINE

To TURBINE

P

=

BD

TEMPERATURE

SET POINT

STATION

MASTER

PRESSURE

CONTROLLER

BPE

PRESSURE

SET POINT

STATION

TEMPERATURE

CONTROLLER

=

T

To CRH


Hp bypass system and reheater protection logic

Reheater Protection Logic


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