. K-TYPE DUPLEX THERMOCOUPLES ARE PROVIDED IN EACH LINE. RANGE : 100 TO 450°C.INSTRUMENTATION PRESSURE MEASUREMENT: TWO Nos. . RANGE : 0 TO 200 kg/sq.cm TEMPERATURE MEASUREMENT: TWO Nos. PRESSURE TRANSMITTERS PROVIDED IN THE UPSTREAM OF HP BYPASS PRESSURE CONTROL VALVES. IN THE MAIN STEAM LINE. LOCATED AT THE DOWNSTREAM OF EACH HP BYPASS PRESSURE CONTROL VALVES. .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. . • Pressure control valves closed less than 2%. • Main steam pressure too high.ALARMS. • Downstream temperature high/very high. • Hydraulic Oil pressure too low. • Pressure control valves opened more than 2%. • Any closing criteria operated. • Tracking Pressure set point failure. INTERLOCKS and PROTECTION ALARMS: The following are the main Alarms generated in the system: • Pressure/Temperature transmitters failure. • Any fast opening criteria operated. • When the Main steam pressure is too high. 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. • Whenever the pressure control valve is opened more than 2%. then the Fast opening device is activated. if it was in Manual mode before. . then the associated control loop will be switched to manual mode. • When the system is in auto mode and if the process signal is failed. then the associated Spray control valve will switchover to Auto mode.ALARMS. a forced close signal is provided to prevent the valve from drift open. then the Pressure control valves are closed on priority. . 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. • When the Turbine trips or when the Generator CB is open.ALARMS. the opening device is activated to prevent Boiler trip. TURBINE CON : CONDENSOR LBPE : LP SPRAY VALVE LPC : LP COOLER LPT : LOW PR. TURBINE .HP / LP BYPASS SYSTEM HRH MSL BP BOILER HPT LPT MPT CRH NRV CRH LBP LPC CO N BPE LBP E BD LEGEND BP : HP BYPASS VALVE LBP: LP BYPASS VALVE BFP: BOILER FEED PUMP HPT: HIGH PRESSURE TURBINE MSL: MAIN STEAM LINE BFP BD : HP SPRAY ISOLATION VALVE BPE : HP SPRAY VALVE CRH : COLD REHEAT LINE HRH : HOT REHEAT LINE MPT : MEDIUM PR. . HP BYPASS CONTROL SCHEME MAIN STEAM LINE To TURBINE P = TEMPERATURE SET POINT STATION MASTER PRESSURE CONTROLLER PRESSURE SET POINT STATION BPE = T To CRH BD TEMPERATURE CONTROLLER . Reheater Protection Logic .
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