CMC IMPLEMENTATION IN OBSOLETE ISKAMATIC TG CONTROL SYSTEM

Transcription

1 UNCHAHAR CMC IMPLEMENTATION IN OBSOLETE ISKAMATIC TG CONTROL SYSTEM NTPC UNCHAHAR Parsuram Saha, DGM(C&I) Neeraj Agarwal, Sr. Supdt.(C&I) A.K.Goel, Sr. Supdt. (C&I) 1

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3 FUEL SECURING FUEL SUPPLIES SOARING FUEL PRICES COAL QUALITY AGING FLEET TECHNOLOGICAL OBSOLESCENCE PERFORMANCE DETERIORATION LIFE EXTENSION ENVIRONMENTAL ISSUES ASH DISPOSAL CO2 EMMISSION COMMERCIAL ASPECTS FINANCIAL HEALTH OF DISCOMs/SEBs HIGH T&D LOSSES REDUCTION IN GENERATION COST 3

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5 R&M Phased process Huge Implication Financial Significant implementation time May require long unit shutdowns In-house Innovations Bridging the technological gap between old & new system Safety features adopted for Interpanel signal exchange 5

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7 2010 CMC Implemented R&M of BOP carried out BFM Implemented Takeover by NTPC. BFM by design but not commissioned 7

8 Load Th. Pr. Air Fuel 8

9 Load Th. Pr. Fuel Air 9

10 Coordinated system response during rapid load variations, thus ensuring grid stability and maintaining critical unit parameters within safe limits. 10

11 CMC IMPLEMENTATION 11

12 DDCMIS (CMC Logic) TG Desk (emergency) TG Control Panel (hardware) CMC 12

13 Unit Load Set Point Fuel & Air Control + d/dt Time Delay Throttle Pressure Set Point Unit Load Controller Throttle Pressure Controller PC LC Throttle Pressure PT MW Generated LT Boiler Turbine Generator Turbine Governor Valve 13

14 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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16 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 16

17 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. 17

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19 ANALOG INPUTS CMC Load Set Point CMC Min. Load Set Point Throttle Pressure Actual Throttle Pressure Set Point DIGITAL INPUTS CMC ON Status CMC OFF Status Turbine Follow Mode Selected Run Back In Action 19

20 ANALOG INPUTS Actual Load Generator Frequency EHTC Load Set Point EHTC Load Reference TSE Upper Load Margin TSE Lower Load Margin DIGITAL INPUTS 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 20

21 COMMUNICATION FAILURE IS UNFORESEEN BUT CATASTROPHIC 21

22 Three tier protection implemented for taking care of Load set point signal failure between DCS & TG controls CMC LOAD SET PT CMC MIN. LOAD SP EHTC PANEL INTERNAL FIXED LOAD SP (6.00 V =150 MW) MAX EHTC LOAD CONTROLLER 22

23 CMC will be automatically switched OFF in case of : Any selected transmitter failure Communication failure Signal isolator failure EHTC card failure. 23

24 A separate on/off push button provided at turbine desk, directly hardwired to ATRS panel, for making CMC ON/OFF in case of any communication failure, any hardware failure. 24

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26 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 26

27 DCS CMC ON (OWS) BLR MSTR ON AUTO LP MODE SELECTED A N D NO EHTC FAULT LOAD DEVN. < 2 % (CMC SP ~ EHTC SP) PR CNTLR IN ACTION S R S-R CMC ON (DCS) IP MODE SELECTED TFM SELECTED BFM SELECTED O R NOT CMC OFF (DCS) MAN MODE SELECTED RUN BACK IN ACTION TURBINE TRIP BOTH HPBP OPEN > 2% 27

28 CMC ON PB (TG DESK) DCS /UCD ATRS CMC ON (DCS) LOAD CNTLR IN ACTION A N D CMC OFF PB (TG DESK) NO EHTC FAULT S R S-R CMC ON (TG) IP MODE SELECTED (TG DESK) CMC OFF (DCS) LOAD CNTLR NOT IN ACTION EHTC FAULT CMC FAULT O R TFM SELECTED (OWS) RUN BACK IN ACTION O R O R IP MODE SELECTED 28

29 DCS /UCD ATRS LOAD SP RAISE/LOWER (TG DESK) R L ACTUAL LOAD (0-250 MW) A S B SEL 2 UMS RL A F Z 12 CMC LOAD SP (DCS) CMC MIN LOAD SP (DCS) ISO-1 ISO ma 4-20 ma I / V CONV I / V CONV 150 MW 2-10 V 2-10 V 6.00 V M A X S E L 1 2 UMS SEL 2 LOAD REFERENCE P R TG MIN. LOAD SP CMC ON (TG) 29

30 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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34 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

35 ID/FD/PA fan IGV & Blade Pitch Control pneumatic actuators were replaced by motorised actuators Old pnematic actuators had poor reliabilty & sluggish response resulting in poor control loop response time. The new motorised actuators were faster & maintenance free. This improved the response time of air flow, PA hdr. & furnace draft control loop. 35

36 The signal transducers used for TSE Lower & Upper margins signals from TSE panel to DCS were : Non linear Poor accuracy Unreliable due to frequent breakdowns 0-1 ma (TSE) 4-20 ma (DCS) 0-1 ma (TSE) 100 ohm Resistor + _ mv (To DCS mv I/P card) Overall accuracy : 5 % Overall accuracy : 0.5 % 36

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38 Adaptive Proportional Gain, slow Integration action, Small derivative action Feed Forwards : Load SP change Target Steam Flow Throttle Pressure Set Point Change Frequency Influence Correction 38

39 LOAD -/+3% RAMP FOR 5 MIN Th. Pr. Oxygen Air Fuel 39

40 LOAD -/+5% RAMP FOR 5 MIN Th. Pr. Air Fuel 40

41 LOAD -/+10% RAMP FOR 2 MIN Th. Pr. Air Fuel 41

42 Load/ Rate of Change (% of MCR per min) Throttle Pressure Deviation (Kg/cm 2 ) Flue gas O 2 Deviation (%) Furnace Pressure Deviation (mmwc) SH Steam Temperature Deviation (deg.c) RH Steam Temperature Deviation (deg.c) Drum Level Deviation (mmwc) Steady State +/- 2 +/ /- 3 +/- 3 +/- 5 +/- 15 +/-3% for 5 min. +/- 3 +/ /- 10 +/- 6 +/- 6 +/- 18 +/-5% for 5 min. +/ / /- 10 +/- 6 +/- 8 +/- 30 +/-10% for 2 min. +/ / /- 13 +/- 6 +/- 15 +/

43 DEVIATION BFM CMC 0 THR. PR. SH TEMP. RH TEMP. HEAT RATE (Ksc) (Deg.C) (Deg.C) (Kcal.) * Data analysis for Load change of 3%/min. for 5 mins. 43

44 Coordinated system response resulted in : Safe Plant operation Improved system stability Enhanced operation flexibility No temperature excursions during Mill changeover or load variations 44

45 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 45

46 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 that with the in-house expertise & resources, systems can be upgraded in sync with the modern technologies to further strengthen the system requirements. 46

47 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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