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7/29/2019 Paper 5-CMC Implementation Unchahar
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CMC IMPLEMENTATION IN OBSOLETE
ISKAMATIC TG CONTROL SYSTEM
UNCHAHAR
Parsuram Saha, DGM(C&I)
Neeraj Agarwal,Sr. Supdt.(C&I)
A.K.Goel, Sr. Supdt. (C&I)1
NTPC UNCHAHAR
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SECURING FUEL SUPPLIES
SOARING FUEL PRICES
COAL QUALITY
FUEL
TECHNOLOGICAL OBSOLESCENCE
PERFORMANCE DETERIORATION
LIFE EXTENSION
AGING FLEET
ASH DISPOSAL
CO2 EMMISSION
ENVIRONMENTAL
ISSUES
FINANCIAL HEALTH OF DISCOMs/SEBs
HIGH T&D LOSSES
REDUCTION IN GENERATION COST
COMMERCIAL
ASPECTS
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R&M
Phased process
Huge FinancialImplication
Significantimplementation time
May require long unitshutdowns
In-house Innovations
Bridging the
technological gapbetween old & newsystem
Safety featuresadopted for Inter-panel signalexchange
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1992 - Takeover by NTPC.BFM by design but not commissioned
1998-99 - BFM Implemented
2008-09 - R&M of BOP carried out
2010 CMC Implemented
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Air
Th. Pr.
Load
Fuel
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Air
Th. Pr.
Load
Fuel
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Coordinated system response during
rapid load variations, thus ensuring grid
stability and maintaining critical unit
parameters within safe limits.
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CMC IMPLEMENTATION
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TG Desk(emergency)
TG
Control
Panel(hardware)
CMC
DDCMIS(CMC Logic)
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Generator
PT LT
PC LC
Boiler
Fuel & Air
Control
Turbine Governor
Valve
MW
Generated
Unit LoadController
Unit LoadSet Point
Throttle PressureSet Point
ThrottlePressure
Throttle Pressure
Controller
d/dt+ Time Delay
Turbine
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Non-availability of Iskamatic cards due to obsolescence
System safety involved with inter-panel signal exchange
Spacing in TG Panel for new card & terminations
Reliable coal flow measurement in volumetric Feeders
Poor Boiler response
Control Loop response time of Drum level control,
furnace draft control, air flow control, etc 14
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Identification of hardware changes
Identification of inter-panel signal exchange
Ensuring cards availability & other hardware
Testing of the cards healthiness.
Designing of TG Iskamatic Panel internal wiring changes.
Designing, Implementation & validation of CMC logic in DCS.
Identification of additional monitoring signals in DDCMIS
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Spare channels & blocks of the existing cards were used Some of the cards were arranged from other power plants
Repaired some of the old cards.
Current to Voltage convertor (AIU-12) - 02 no.
Voltage to Current convertor (AUI-12) - 01 no.
MAX / UMS selector (AVB-11) - 02 nos.
NOT Gate (FA-15) - 01 no.
OR Gate (VA-11) - 02 nos.
Set Reset (VS-11) - 01 no.
Relay - 02 nos.
Signal isolator - 04 nos.
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ANALOG INPUTS DIGITAL INPUTS
CMC Load Set Point
CMC Min. Load Set Point
Throttle Pressure Actual
Throttle Pressure Set Point
CMC ON Status
CMC OFF Status
Turbine Follow Mode Selected
Run Back In Action
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ANALOG INPUTS DIGITAL INPUTS
Actual Load
Generator Frequency
EHTC Load Set Point
EHTC Load Reference
TSE Upper Load Margin
TSE Lower Load Margin
CMC ON From ATRS To DCS
IP Mode Selected
LP Mode Selected
Pressure Controller Active
Pressure Controller ON
EHTC Fault
TSE Fault
Turbine Tripped
Frequency Influence ON
LSR operated
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COMMUNICATION FAILURE
IS UNFORESEEN
BUT
CATASTROPHIC
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Three tier protection implemented for taking
care of Load set point signal failure between
DCS & TG controls
MAX
CMC LOAD SET PT
CMC MIN. LOAD SP
EHTC PANEL INTERNAL
FIXED LOAD SP
(6.00 V =150 MW)
EHTC LOAD CONTROLLER
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CMC will be automatically switched OFF in case of :
Any selected transmitter failure
Communication failure
Signal isolator failure
EHTC card failure.
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A separate on/off push button provided atturbine desk, directly hardwired to ATRS panel,
for making CMC ON/OFF in case of
any communication failure,
any hardware failure.
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CMC mode can be selected from OWS if :
Air master is in Auto
Fuel master is in Auto
Drum Level is in Auto
Boiler Master is in Auto
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LP MODE SELECTED
CMC ON (OWS)
O
R
S-RS
R
CMC ON
(DCS)
DCS
A
N
D
NO EHTC FAULT
TURBINE TRIP
PR CNTLR IN ACTION
IP MODE SELECTED
TFM SELECTED
RUN BACK IN ACTION
BLR MSTR ON AUTO
LOAD DEVN. < 2 %
(CMC SP ~ EHTC SP)
BFM SELECTED
MAN MODE SELECTED
NOT CMC OFF
(DCS)
BOTH HPBP OPEN > 2%
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LOAD CNTLR
IN ACTION
CMC ON
(DCS)
O
R
S-R
S
RCMC ON(TG)
DCS /UCD ATRS
A
N
D
NO EHTC
FAULT
CMC ON PB(TG DESK)
CMC OFF
(DCS)
CMC OFF PB(TG DESK)
LOAD CNTLR
NOT IN ACTION
EHTC FAULT
IP MODESELECTED
(TG DESK)
TFM SELECTED
(OWS)
RUN BACKIN ACTION
O
R
O
R
IP MODE
SELECTED
CMC FAULT
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Load Set Point Generation TSE Upper Load margins, TSE Lower
Load margins, Unit capability & Load gradient governs the final CMC
load set point to Turbine EHTC Controls.
Load SP Tracking CMC and TG desk EHTC load set point tracks
actual Load for smooth change-over when CMC is made ON/ OFF.
Runback scheme If any ID, FD, PA, BFP or Mill trips, then machine
will switch over to Turbine Follow mode and IP mode will be selected.
Pressure & Frequency Infl. correction Load set point to TG is
slightly corrected to counter the changes in Throttle Pressure &
frequency, thus ensuring stability. 30
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Feeder speed pick-up relocated on sprocket of drag chain so
that feeder speed becomes zero in case of drag chain breaks.
CHAIN
BREAKS
Thus coal flow measurement, a vital parameter in CMC loop,
was made more reliable. 34
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ID/FD/PA fan IGV & Blade Pitch Control pneumatic actuatorswere replaced by motorised actuators
Old pnematic actuators had poor reliabilty & sluggishresponse resulting in poor control loop response time.
The new motorised actuators were faster & maintenancefree.
This improved the response time
of air flow, PA hdr. & furnace draft
control loop.
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The signal transducers used for TSE Lower & Upper marginssignals from TSE panel to DCS were :
Non linear
Poor accuracy
Unreliable due to frequent breakdowns
0-1 mA(TSE)
0-100 mV(To DCS mV
I/P card)
+
_
100 ohm Resistor
0-1 mA
(TSE)4-20 mA
(DCS)
Overall accuracy : 5 % Overall accuracy : 0.5 %
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Adaptive Proportional Gain, slow Integrationaction, Small derivative action
Feed Forwards :
Load SP change
Target Steam Flow
Throttle Pressure Set Point Change
Frequency Influence Correction
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Air
Th. Pr.
LOAD
Fuel
Oxygen
-/+3% RAMP FOR 5 MIN
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-/+5% RAMP FOR 5 MIN
Air
Th. Pr.
LOAD
Fuel
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-/+10% RAMP FOR 2 MIN
Air
Th. Pr.
LOAD
Fuel
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Load/ Rate of
Change (% of
MCR per min)
Throttle
Pressure
Deviation
(Kg/cm2)
Flue gas O2Deviation
(%)
Furnace
Pressure
Deviation
(mmWC)
SH Steam
Temperature
Deviation
(deg.C)
RH Steam
Temperature
Deviation
(deg.C)
Drum Level
Deviation
(mmWC)
Steady State +/- 2 +/- 0.4 +/- 3 +/- 3 +/- 5 +/- 15
+/-3% for 5 min. +/- 3 +/- 0.6 +/- 10 +/- 6 +/- 6 +/- 18
+/-5% for 5 min. +/- 3.5 +/- 0.8 +/- 10 +/- 6 +/- 8 +/- 30
+/-10% for 2 min. +/- 4.0 +/- 1.0 +/- 13 +/- 6 +/- 15 +/- 50
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0
5
10
15
20
25
THR. PR. SH TEMP. RH TEMP. HEAT RATE
5
12 12
21
3
6 6
11 BFM
CMC
DEVIAT
ION
(Ksc) (Deg.C) (Deg.C) (Kcal.)
* Data analysis for Load change of 3%/min. for 5 mins.
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Coordinated system response resulted in :
Safe Plant operation
Improved system stability
Enhanced operation flexibility
No temperature excursions during Mill
changeover or load variations
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Increased unit Efficiency
Reduced generation cost
Minimisation of UI losses
Better Control of critical unit parameters
No thermal stresses on turbine due to reduced
cyclic variations
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In todays scenario of fast changing technological
advancements the systems are grappling with problem of
obsolescence.
With innovative approach adopted for In-house modifications,
we can overcome this challenge and that too without being
dependent on OEM for modifying the existing system.
This successful implementation of CMC has demonstrated thatwith the in-house expertise & resources, systems can be
upgraded in sync with the modern technologies to further
strengthen the system requirements.46
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Innovation always beats the limitations by
well planned team perseverance. It is a job
that has no defined end point and there is
always scope for further performance
enhancement.
The journey continues..47
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