paper 5-cmc implementation unchahar.pdf

8/17/2019 Paper 5-CMC implementation unchahar.pdf

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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

R CMC 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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CMC LOAD SP

(DCS)

CMC MIN

LOAD SP

(DCS)

ISO-1

ISO-2

I / V

CONV M

A

X

S

E

L 150 MW

UMS

R

L

SEL 2

1

2

LOAD

REFERENCEPR

DCS /UCD ATRS

I / VCONV

2-10 V

4-20 mA

4-20 mA

2-10 V

6.00 V

CMC ON (TG)

A

F

Z

12

A

SB

12

TG MIN. LOAD SP

RL

UMS

SEL 2

1

2ACTUAL LOAD

(0-250 MW)

LOAD SPRAISE/LOWER

(TG DESK)

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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,

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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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Air

Th. Pr.

LOAD

Fuel

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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

D E V I A T

I O N

(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 today’s 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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paper 5-cmc implementation unchahar.pdf

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