CONTROL AND PROTECTION -...

CONTROL AND AND

PROTECTION

Protection and Safety Interlocks

Protection – General understanding?

What we already know.

n Operation of the BOILER, TURBINE, GENERATOR are closely coupled

n A trip on any one of the three has a direct impact on the continued operation of the other two causing interruption to power production process

n Why Trip – On occurrence of any unsafe or abnormal operating condition the BOILER, TURBINE, GENERATOR are tripped individually

Protection – General understanding?

What does TRIP mean

n Boiler trip : q Stops fuel feed to Furnaceq Purpose – To clear out combustibles from the Boiler and prevent any

explosive condition from persisting

n Turbine trip : q Close all steam admission valves (ESV, GOV Valves)q Purpose – Stop steam admission to ensure turbine coasts down and

Open all drain lines of steam admission pipes upstream / down stream valves to prevent accumulation of water which may enter the Turbine

n Generator trip : q Opens CB connecting Generator to Grid

n Purpose – Isolate system from faulty generatorq Opens Field Circuit Breaker to cut-off excitation

Signal Voting

A

B

C

A

A B

A

1oo1

1oo2

2oo2

CB

2oo3

A B

A C

B C

Dual SystemsDual SystemsP

roce

ss V

aria

ble

High Pressure Set Point

?Which Signalis Correct ?

1oo2 Config = Shut down

Time

Pro

cess

Var

iabl

e

is Correct ?

TMR SystemsTMR SystemsP

roce

ss V

aria

ble


2oo3 = Continue to operate

High Certainty this is a bad signal

Time

Pro

cess

Var

iabl

e

TMR SystemsTMR SystemsP

roce

ss V

aria

ble


2oo3 = Shut Down

High Certainty these are good signals

Time

Pro

cess

Var

iabl

e

High Certainty this is a BAD signal

TURBINE TRIP CONDITIONS

q TG BEARING OIL PRESSURE LOWq CONDENSER VACUUM LOWq CONDENSER EHWLq HP EXHAUST TEMPERATURE HIGHq 3 OUT OF 4 GOVERNOR VALVES TRIPPEDq 2 OUT OF 2 INTERCEPT VALVES TRIPPED2 OUT OF 2 INTERCEPT VALVES TRIPPEDq EHG FAULTq THRUST WEAR HIGHq STATOR COOLANT FLOW LOWq MAIN STEAM PRESSURE LOWq MAIN STEAM TEMPERATURE LOWq MFT OPERATEDq 86U OPERATED NEXT

86T – TG Bearing oil pressure low

n TG BEARING OIL PRESSURE LOW

Source : Pressure switch (2/3)

Implication: Will result in in-sufficient lubrication in between rotor and bearing journal leading to breaking of between rotor and bearing journal leading to breaking of oil film and resulting in metal to metal rubbing and thus damaging the Turbine

Action: 86T

Turbine Trip Conditions

86T – Condenser Vacuum Low

n Condenser Vacuum Low

Source : Pressure Transmitter (2/3)….. EHG…..

Implication: Will produce undue stress on Turbine blades due to reduction of “available enthalpy” (rise in exhaust conditions). Usually reduction of “available enthalpy” (rise in exhaust conditions). Usually a Trip is preceded by “de-loading of turbine” as per Turbine manufacturer recommendation

Action: 86T


86T – Condenser EHWL

n Condenser EHWL

Source : Level switch (2/3)

Implication: Flooding of the condenser will result in a. limited heat exchange area and hence vacuum will fallb. excessive strain on the condenser neck hanging from LP Turbinefrom LP Turbinec. After EHWL there is no control on the level nor can it be monitored and hence is used as a last stage of protectionb. water may reach LP blades at a later stage

Action: 86T


86T – HP Exhaust Temperature High

n HP Exhaust Tempertaure High

Source : Thermocouple (2/3)…EHG ….

Implication: Deviation in “available enthalpy” across HP Turbine from design value will produce stress on HP blades . This is special from design value will produce stress on HP blades . This is special protection feature for Tubines equipped with HPLP Bypass.

Action: 86T


86T – 3 out of 4 Governor valves tripped

n 3 out of 4 Governor valves tripped

Source : Median Select Controller …EHG ….

Implication: Failure of HP Gov valves stops steam admission to HP Turbine. Admission of steam thru’ single Gov valve will result in non Turbine. Admission of steam thru’ single Gov valve will result in non uniform temperature distribution within the Turbine which may result in distortion of blades , rotor.

Action: 86T


86T – 2 out of 2 Intercept valves closed

n 2 out of 2 Intercept valves closed

Source : Median Select Controller …EHG ….

Implication: Failure of IP Intercept valves stops steam admission to IP & LP Turbine. This will disturb the HP IP Implication: Failure of IP Intercept valves stops steam admission to IP & LP Turbine. This will disturb the HP IP work ratio.

Action: 86T


86T – EHG FAULT

n EHG Fault

Source : Speed sensed thru’ eddy current probe…EHG ….

Implication: Failure of governing system as basic input on the basis of which governing occurs is not availableof which governing occurs is not availableEHG fault signifies either channel failure or speed sensor failure

Action: 86T


86T – Thrust Wear High

n Thrust Wear High

Source : Eddy Current Probe…TSE ….

Implication: Indicates axial shift of rotor with respect to stator in the axial direction and may result in fixed and moving blades fouling . axial direction and may result in fixed and moving blades fouling . The reference point of rotor located with the stator will shift as a result of wear on the thrust pads / collar.

Action: 86T


86T – Stator Coolant Flow Low

n Stator Coolant Flow Low

Source : Flow switch (2/3) + timer….

Implication: Will result in heating up of the hollow conductors in generator as little or no cooling medium is present and lead to insulation failure. This has been purposely introduced under Turbine insulation failure. This has been purposely introduced under Turbine protection rather than generator protection due to implications in house load operation.

Action: 86T


86T – Main Steam Pressure Low

n Main Steam Pressure Low

Source : Pressure transmitter (2/3) ….EHG….

Implication: Will produce undue stress on Turbine blades due to reduction of “available enthalpy” (reduction in input conditions). reduction of “available enthalpy” (reduction in input conditions). Usually a Trip is preceded by an “de-loading of turbine” as per Turbine manufacturer recommendation.

Action: 86T


86T – Main Steam Temperature Low

n Main Steam Temperature LowSource : Temperature transmitter (2/3) ….DCS….

Implication: Will produce undue stress on Turbine Implication: Will produce undue stress on Turbine blades due to reduction of “available enthalpy” (reduction in input conditions).

Action: 86T

86T – Main Steam Temperature Low Logic


Effects on Turbine Trip

n Runback of Turbine via EHG

n Generator/Electrical Protection operates

n Preferential Tripping of MILLS

Quick Opening of HP Bypass valve if Load> n Quick Opening of HP Bypass valve if Load> 22 %

n De-aerator and Heaters NRV closes

n Turbine and Heater drain valves open


Boiler

ØProtection and Safety Interlocks

Situations Causing Explosive conditions?

Numerous situations can arise in connection with the operation of a boiler furnace that will produce explosive conditions.

q Interruption of Fuel or air supply or ignition energy to the burners.

q Fuel Leakage into an idle furnace and the ignition of the accumulation accumulation

q Repeated Unsuccessful attempts to light up without appropriate purging

q The Accumulation of an explosive mixture of fuel and air as a result of a complete furnace flameout

Requirement

Multiple burner boilers require two independent control systems.

q One to control steam production i.e. Boiler q One to control steam production i.e. Boiler Control System and

q One to control the fuel burning equipment i.e. Burner Management System

BMS - What are the basic Functions?

The BMS shall be designed to perform the following functions:

n Prevent firing unless a satisfactory furnace purge has first been completed.

n Prohibit start-up of the equipment unless certain permissive interlocks have first been completed.

Monitor and control the correct component sequencing during start-up and shut-n Monitor and control the correct component sequencing during start-up and shut-down of the equipment.

n Provide component condition feedback to the operator and, if so equipped, to the plant control systems and/or data loggers.

n Provide automatic supervision when the equipment is in service and provide means to make a Master Fuel Trip (MFT) should certain unacceptable firing conditions occur.

n Execute a MFT upon certain adverse unit operating conditions.

How do we categorize the different controls

A Boiler Control System shall have the following applications

n Combustion control

n Excess air control

n Steam drum level controln Steam drum level control

A Burner Management System shall have the following applications

n Boiler purge control

n Fuel safety control

n Pre-light up control

n Individual burner control

Boiler Purge ControlWhy: For removing all combustibles from the boiler furnace and replacing them with air to prevent any explosive mixture from remaining in the furnace prior to light up.

When: After a Master Fuel Trip has occurredHow:

A. Ensuring that a predetermined set of fuel and air related permissive conditions are satisfied which shall include

q All fuel valves (Shut-off valves, oil valves) closedq All fuel valves (Shut-off valves, oil valves) closedq Either of one FD Fan & ID Fan running q All Mills and Feeders stopped and Mill discharge valves closedq All PA Fans stopped and PA to Mill inlet dampers closedq All scanners sense no flameq Air flow is not less than 25% - 35 % (multiple burner boilers) of full load air flowq 4 out of 6 secondary air dampers at Purge positionq No MFT conditions presentq MFT relay tripped

Now the Boiler is Ready for Purge

Boiler Purge Control

B. Initiate Boiler Purgeq Dampers are initiated to move to Purge position (air flow 30 to 80 T/hr)q 5 minute purge timer triggersq Boiler purge in progress is indicated

After 5 minutes has elapsed the Purge process is complete and the boiler is ready for firingIf any of the condition mentioned in ‘A’ fails during purging process, purging is interrupted and the timer resets.

Fuel Safety Control

Why: To prevent any explosive condition in the furnace

What: Withdraws fuel feed to the Furnace

When: If any of the predetermined trip conditions has occurred.

ClassificationDepending on the fuels involved the fuel safety control can be made up of the following:q Master fuel tripq Oil fuel trip

Master Fuel Trip

If any of the predetermined master fuel trip condition occurs a master fuel trip is initiated. The first out cause of trip indication is displayed and alarmed. Conditions of a master fuel trip are:

q All FD Fans off

q All ID Fans off

Boiler air flow low for 3 secsq Boiler air flow low for 3 secs

q Loss of all fuel

q Loss of all flame

q Furnace pressure very high/Low

q Drum level very high/low

q Critical Flameout

q Delayed light-up

q Re-heater protection operated

Master Fuel Trip

Some more Conditions of a master fuel trip (continued) :q Loss of HT powerq Loss of UPS powerq Loss of 220V DC powerq Condenser vacuum very lowq MFT hard relay trippedq 2 out of 3 main processors failedq 2 out of 3 main processors failedq Both emergency trip push buttons operatedAny of the above occasions will result in a MFT

MFT can be reset whenq None of the above trip conditions existq Boiler purge is completeq Reset MFT is initiated

NEXT

MFT – all FD fans off

n All FD fans Off

Source : Breaker off signal from both fans

Implication: Will result in in-sufficient air for the combustion process and the fuel cannot burn

Action: MFT

MFT conditions

MFT – all ID fans off

n All ID fans Off

Source : Breaker off signal from all 3 fans

Implication: Will result in an uncontrolled furnace Implication: Will result in an uncontrolled furnace pressurization.

Action: MFT

MFT conditions

MFT – Air flow less than 25%

n Boiler air flow less than < 25% for 3 secs

Source : Flow transmitters at FD suction

Implication: Will result in in-sufficient air for the Implication: Will result in in-sufficient air for the combustion process and the fuel cannot burn completely

Action: MFT

MFT conditions

MFT – Loss of all fuel

n Loss of all fuel

Source : Any oil burner in operation (MFT trip resets)and closure of all burner valves and all Mills ‘off’ and no mill in shutdown mode.

Implication: As no fuel is being fed into the furnace generation of heat for sustenance of combustion and subsequent production of steam cannot take place

Action: MFTMFT conditions

MFT – Loss of all flame

n Loss of all flame

Source : Any oil burner in operation and no scanners see flame.

Implication: Will proactively safeguard all adverse effect due to non burning of fuel (detected from the intensity of flame) being injected into the furnace


MFT – Furnace pressure very high/low

n Furnace pressure very high /low

Source : Pressure switch and transmitter.

Implication: Will result in explosion or implosion of the furnace resulting in mechanical deformity

Action: MFT

MFT conditions

MFT – Drum level very high/low

n Drum level very high / low

Source : Hydrastep and drum level transmitter

Implication:High: Will result in Flooding of superheaters causing a. carryover of dissolved solids and hence deposition downstream effecting a. carryover of dissolved solids and hence deposition downstream effecting heat transfer b. fall of steam temperature and quenching of Turbine

Low: Will result in starvation of water in the furnace tubes which will lead to tube metal overheating as no cooling medium is present


MFT – Critical flameout

n Critical Flameout

Source : Furnace flame scanners detect 2 out of 3 zones no flame

Implication: Is a consequence of improper combustion in Implication: Is a consequence of improper combustion in pre-identified zones within the furnace resulting in flame instability which may give rise to improper heat distribution


MFT – Delayed light-up

n Delayed light up

Source : MFT reset , LDO shut off valves open and no oil gun in operation (or in other words put into service) within 10 mins of opening of LDO shut-off valves.

Implication: Repeated unsuccessful attempts to light up the boiler with oil gun has resulted in accumulation of un-burnt fuel (oil) in the furnace and hence the furnace requires purging.


MFT – Re-heater protection

n Re-heater protection

Source : All governor valves closed, HP bypass valve < 2% open witha. at least one feeder running from remote or or b. More than 8 out of 12 oil guns in operation

Implication: Damage to tubes that can result from firing in excess of safe limit which will cause overheating of re-heater tubes due to absence of a steam flow through it.

Action: MFT

MFT conditions

MFT – Condenser Vacuum Low

n Condenser Vacuum Very Low

Source : Pressure switch installed at condenser (500 mmHg abs)

Implication: Under turbine tripped condition and bypass in operation steam dumping continues at condenser which can result in steam dumping continues at condenser which can result in pressurization. Under such poor vacuum conditions the condenser is not capable of dissipating the heat load with existing CW flow and with effect the temperature rises.

Action: MFT

MFT conditions

Oil Fuel TripIf any of the predetermined oil fuel trip conditions is exceeded the oil fuel trip is initiated. The first out cause of trip indication is displayed and alarmed. All oil fuel is removed from the boiler and all oil burners are shutdown. Depending on other conditions a master fuel trip may be generated. Conditions of an oil fuel trip are:

q LDO trip valves close commandq LDO trip valves not closed and LDOT condition is presentq LDOT relay fail to trip and LDOT condition is presentq LDO pressure very low for 3 secs and any LDO burner valves not closedq Atomising air pressure very low for 3 secs and any LDO burner valves not closed q LDO trip valve not open within 10 secs of LDOT resetq Any burner valve fail to close despite boiler load being > 50%q Any burner valve fail to close despite boiler load being > 50%q LDOT hard relay tripped

LDOT can be reset whenq None of the above trip conditions existq MFT relay is resetq Trip valve open is initiatedq All LDO burner valves are closed

Mill Trip Conditions

The following conditions shall cause a Mill to tripq LOS or emergency stop pressed

q Mill and feeder running from remote, oil flame not detected with either feeder speed <30 % or coal flame not detected signifying low coal and no ignition source

q Feeder running from remote and coal and oil flame neither detected assuming flame monitoring system is healthy signifying loss of coal flame without ignition flame monitoring system is healthy signifying loss of coal flame without ignition source

q Loading gas pressure very low

q Lub oil pressure very low signifying no lubrication to Mill gear box and bearings

q Both PA fans stopped

q Mill running from remote for >30 secs and PA flow below minimum

q Mill running from remote for >30 secs and Secondary air flow < 45%

q Seal air pressure very low

q MFT or Mill hard relay

Preferential Mill Tripping

Why : To take out certain running Mills out of service as per preference in order to reduce firing and compensate for the furnace conditions prevailing

When :q On Turbine tripq Load rejection >50 %q Single FD or PA fan runningq Single FD or PA fan running

How : It ensures that extreme burners shall tripq Under 4 mill condition

n if Mill D is not in service then Mill A tripsn If Mill A is not in service then Mill D tripsn If both Mill A and Mill D are in service, Mill A trips if Mill D is the single Mill in the rear OR Mill D trips if

Mill A is the single Mill in the frontn If Mill A and Mill D both are not in service then Mill B trips

q Under 5 mill conditionn Mill A and Mill D trips if they are both in service n Mill A and Mill B trips if Mill D is not in servicen Mill B and Mill D trips if Mill A is not in service

86G86U

Open GCB

GCB Not open

&

O/S Bolt operated

Condenser vacuum V.Low

Turbine trip condn

Open GCBOpen FCB

GCB Not open

&LBB 2

132KV diffl protnBus Zone Trip

Reverse powerLoss of excitation

Excitation Trip

Trip condn for 86G

Other Fault conditions

86T

MFR

Boiler trip condn

Reheater protn

&

Low Forward power

FCB Closed

LBB 1

&

Governor Vv closedFiring rate highBypass < 2%

&Turbine Trip Conditions

Control & Instrumentation in Thermal Power Plant

PRIMARYCRUSHER

COAL & PRIMARY

AIR

WAGON

RAILWAYTRACK

COAL

BUNKER

S U P E R

H E A T E R

DRUM

TURBINE GENERATOR

ID FAN

ESP

CHIMNEY

GOVERNER VALVE

TRANSFORMER

TO DISTRIBUTION

SYSTEM

COAL STOCK

ELECTRICITY

STEAMAPH

DRY ASH SILO

TO AMBUJA FOR PPC

CEMENT

HCSS

EXPORT OF ASH TO

BANGLADESH

GENERATOR

FEEDER

SECONDARYCRUSHER

ISH

COAL MILL

PA FAN

FD FAN

TURBINE GENERATOR

CONDENSER

CONDENSER COOLING WATER SYSTEM

FORE BAY

COOLING TOWER

CW PUMP

DM PLANT

RAW WATER TREATMENT

INTAKE PUMPS

RIVER GANGES

COAL ELECTRICITY

BOILER

FEED WATER

APH

AIR PRE HEATER

MAKE UP WATER SYSTEM

ZERO DISCHARGE

SYSTEM

BOTTOM ASH

BOTTOM ASH

HOPPER

BFP

SECON-DARY AIR

GENERATOR

CEPLPHD/A

HPHAIR INTAKE

Process schematic

Control System for Processes

OutputInput

- DCS

- PLC

- EHG

- AVR

- AV6 (for Bypass)

Input Devices

-Transmitters

- Switches

-Transducers

Output Devices

- Actuators

- Drives

- Indicators

Controlled Parameters

Most commonly controlled parameters in Industry are:

1. Flow

2. Level2. Level

3. Temperature

4. Pressure

5. Speed (RPM)

6. Position

FLOWn Measured with

q Orifice, Nozzle

n Pressure drop measured with

q DP Transmitter

n Flow ∞ K √DPInput

DCS

DP

FLOW

Input

Processor

Output

4 to 20 mA signal

Valve

Actuator

4 to 20 mA signal

LEVEL

n Measured using

q Constant Head Unit

n Pressure difference measured with

q DP Transmitter

n Level ∞ HeadInput

DCS

Level ∞ HeadInput

Processor

Output

4 to 20 mA signal

Valve

Actuator

4 to 20 mA signal

DP

TANK

CHU

TEMPERATURE

n Measured byn RTD (Pt 100)

q Output Resistance (ohms)

q At 0°C value is 100 ohms

q Change is 0.385 ohm / °C (Linear)

TEMPERATURE

n Measured byn Thermocouple

q Output mVq Types: J,K,T,S….

• Temperature TransmitterOutput 4 to 20 mAn Output 4 to 20 mA

Controlling Devices

n Most common final control devices are:

1. Pneumatic actuators – modulating type

2. Pneumatic actuators – On/ Off type2. Pneumatic actuators – On/ Off type

3. Motorised actuators – On/ Off type

4. Hydraulic actuators – servo operated

5. Variable frequency drives

6. Servo motors

WHAT IS AUTOMATION?

What is in a Automation System?

Control Processor

Input to the System

Field Inputs (Transmitters/ Switches / Sensor)

Field Outputs (Valves / Pumps / others)

Input to the system

Systemoutput

INPUT MODULES OUTPUT MODULES

Examples of Boiler Controls

n Boiler Control System comprises the following functions

q Boiler Master Pressure Control

q Fuel Flow Control

q Feeder Speed Control

q Mill Air Flow Control and Temperature Control

q Excess Air Control

q Drum Level control

q Furnace Draft Control

q Super-heater Steam temperature Control

q Various other Pressure, Temperature, Level, Flow , Position Controls

Examples of Turbine Controls

n Turbine Control System comprises the following functions

q Heater Level Control

q Hotwell level Control (Condenser)

q Lub Oil Temperature Control

q BFP Scoop Position Control

q De-aerator Level control

q Governor Control

Control System Hardware

PLC

DCS

What is TMR architecture?

n It means Triple Modular Redundant

n TMR architecture integrates three isolated parallel n TMR architecture integrates three isolated parallel control systems ( as evident in diagram)

n The system uses TWO-OUT-OF-THREE voting to provide high integrity, error free uninterrupted process operation with no single point failure

Hardware - PLC

n EFFECTIVE AND RELIABLE SYSTEM FOR OVERALL SUPERVISION OF BOILER SAFETY IN A POWER PLANT.

n CONTAINS SAFETY GUIDELINES

Transferring control to Fault Tolerant pair and running

self diagnostics

PROGRAMMED INSIDE FOR

– TAKING PREVENTIVE MEASURES

– IN EXTREME CASES TO TAKE THE WHOLE SYSTEM TO STEP-BY-STEP SHUTDOWN.

n IT FORESEES FUTURE ERROR AND GENERATE ALARMS. Running self

diagnostics and monitoring

Chassis with

Processor and I/O

cards

Hardware - PLC

n THE BMS IS A PLC, PROGRAMMED ACCORDING TO USER NEED.n LIKE CONVENTIONAL PLC SYSTEMS THE BMS ALSO CONSISTS

OF THE FOLLOWING PARTS:-1. MOUNTING RACK FOR HOUSING THE WHOLE PLC

SYSTEM.2. POWER SUPPLY FOR SUPPLYING POWER TO THE

PLC SYSTEM.PLC SYSTEM.3. MAIN PROCESSOR THE BRAIN OF THE SYSTEM4. I/O CARDS INTERFACING UNITS BETWEEN

SYSTEM & FIELD5. SPECIAL MODULES COMMUNICATION WITH OTHER

SYSTEMS, ETC.6. SPECIAL FUNCTIONS HIGH SPEED COUNTER,

THERMOCOUPLE SENSORS (NOT IN BBGS)

Distributed Control System (DCS)

n Comprises CLCS ,OLCS and DASq CLCS – Various closed loop controls for process

are incorporated here

OLCS – Various open loop controls for q OLCS – Various open loop controls for unidirectional and bidirectional drives are incorporated here

q DAS – Data for indication purpose, historian, trending, logs, SOE

DCS Hardware

Ø Application processors (File server) - AW

Ø Control Processors - CP

Ø Workstation Processors (Client – user interface) - WP

Stations –Processor modules

Ø Field Bus Modules (FBM) types

Ø 0 to 20 mA input

Ø TC / mV input

Ø RTD input

Ø 0 to 20 mA input / output

Ø Contact/dc input/output main

INPUT / OUTPUT Interfacing modules

DCS Architecture – Bus Topology

Application Processor Workstation Processor

Ethernet IEEE 802.3

Control ProcessorFT

FBMS FOR CLCS/OLCS & DAS

NODE BUS

FIELD BUS

Input & Output

Redundant Switches

DCS SYSTEM ARCHITECTURE - Mesh Network

UNIT-2 AWCSUNIT-1

WP70P

Redundant SwitchesRedundant Switches

24 SFP Port Uplink Switches

1 GBPS 1 GBPS 1 GBPS

AW70P

WP70P

WP70P

WP70P

WP70P

FCP270(FT)

100 MBPS

100 MBPS

100 MBPS

100 MBPS

100 MBPS

100 MBPS100 MBPS

100 MBPS

FCP270(FT)

WP70P

LEGEND:

Engineering cum Operator Station on

Windows XPOperator Station on Windows XP

24 Port Fiber Ethernet Switch

FCP270 in Fault Tolerant Mode

AW70P

WP70P

WP70P

FCP270(FT)

FCP270(FT)

FCP270(FT)

FCP270(FT)

FCP270(FT)

FBMs for Triconex

100 Series FBMs

100 MBPS

100 MBPS

100 MBPS

100 MBPS

100 MBPS

100 MBPS

100 MBPS

DCS Hardware (OLCS)

n Field Inputn DCS Marshalling Rackn IA Enclosure – DCS (Logic)n DCS Relay Rack

INPUT

DCS Relay Rackn DCS Marshalling Rackn MCC Modulen Drive (Motor)

OUTPUT

DCS Hardware (CLCS)

n Field Input (Sensors)n DCS Marshalling Rackn IA Enclosure – DCS (Control loops)n DCS Marshalling Rack

INPUT

OUTPUTDCS Marshalling Rack

n Final Control Element (Actuators)OUTPUT

DCS Software

n The software comprises of mainly

q Operating Systemq Application soft wares for

n display building – creating drawings and display pages n display building – creating drawings and display pages n display configuration – connecting inputs to show in display

page n control configurations – comprises various control blocks , its

connectivity with other blocks to derive a control loopn Pre-trip and Post-trip software – data loggingn Historian software – historical data for analysisn Event recorders – Operator action, process alarms etc

IFL-1 CIN-2 OFL-10 CIN-20 TC02-S CIN-6 INT-04 CO-1

CRT STARTREMOTE

SS IN PUMP INMANUAL

JOP SUCPR LO ELEC TR8

NO MOD INSERV

STOP

CIN-7

MOD INTEST

CIN-17 CIN-1

INT-02

CO-1

ACJOP

STARTSS INLOCAL

LOCAL

AUT STR

STR / STPACJOP

IFL-2

STR / STPACJOP

CIN-2

SS INREMOTE

CRT STOP

CIN-18

AUTO

STOPLOCAL

CIN-19 OFL-11 CIN-2

SS INREMOTE

TRB SPDLT 1000

PUMP IN

TC01-S

JOP SUCPR LO

INT-04

STOP

EXAMPLE : LADDER LOGIC

START / STOP LOGIC

OPEN LOOP CONTROL

SAMA Functional Diagramn SAMA is an acronym standing for Scientific Apparatus Makers Association, referring

to a unique form of diagram used primarily in the power generation industry to document control strategies.

Standard SAMA Symbols

PID Controller

DRUM LEVEL CONTROL

AIN AIN AIN

LT LTLT

DRUM LEVEL LHS

AIN AIN AIN

PT PTPT

AIN AIN AIN

LT LTLT

DRUM PRESSURE DRUM LEVEL RHS

1

∑/2

CALC CALCf(x)

DENSITY COMPENSATED

DRUM LEVEL

DRUM LEVEL CONTROL

AIN AIN AIN

FT FTFT

MAIN STEAM FLOW

AIN AIN

PT PT

AIN AIN AIN

TT TTTT

MAIN STEAM PRESSURE MAIN STEAM TEMP

T

BAD

2

CALC CALC

PRESSURE,TEMP COMPENSATED TOTAL STEAM FLOW

AUXILIARY STEAM FLOW

DRUM LEVEL CONTROL

AIN AIN AIN

FT FTFT

FEED WATER FLOW

AIN AIN AIN

TT TTTT

FEED WATER TEMP

3

CALC

TEMP COMPENSATED FEED WATER FLOW

f(x)

21

Δ

PI

∑

TR

Δ

PI

TR

T

SP

3

ΔPITR

RSP

LC-2 FC

MANSW

Drum Level Main Steam Flow

Feed Water Flow

LC-1

3E

1E1E

+/-T

f(x)

MANSW

AOUT

LLFCV

+/-T

AOUT

FLFCV-1

+/-T

f(x)

AOUT

FLFCV-2

MANSWSEL VLV

MANSW DRUM LEVEL CONTROL

21

Δ

PI

∑

TR

Δ

PI

TR

T

SP

3

ΔPITR

RSP

LC-2 FC

MANSW


Feed Water Flow

LC-1

3E

1E1E

+/-T

f(x)

MANSW

AOUT

LLFCV

+/-T

AOUT

FLFCV-1

+/-T

f(x)

AOUT

FLFCV-2

MANSWSEL VLV


21

Δ

PI

∑

TR

Δ

PI

TR

T

SP

3

ΔPITR

RSP

LC-2 FC

MANSW


Feed Water Flow

LC-1

3E

1E1E

+/-T

f(x)

MANSW

AOUT

LLFCV

+/-T

AOUT

FLFCV-1

+/-T

f(x)

AOUT

FLFCV-2

MANSWSEL VLV


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