1 generation technologies -- bhanu bhushan -- [email protected] (august, 2011)
TRANSCRIPT
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• Thermal -- Coal / Lignite
• Gas turbine / Combined cycle
• Hydro -- Storage / R-o-R / Pumped
• Nuclear
• Wind and other Renewable
• Captive and Co-generation
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• Process
• Conversion efficiency
• Variable cost
• Peaking capability
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• MCR, under different conditions
• Reactive capability
• Over-loading capability
• Loading restrictions
• Ramp-up / ramp-down rates
• Start-up times -- cold / hot
• Impact of voltage and frequency
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Main parameters to be controlled in a thermal generating unit
1) Turbine speed / MW
2) Steam pressure
3) Steam temperature
4) Drum level
5) Furnace draft
6) Air - fuel ratio
7) Condenser level
8) De-aerator level
9) Voltage / MVAR
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Abnormal situations / contingencies
• Tripping of an auxiliary -- Stand-by should take-over, or run-back / interlocked trip.
• Parameters deviate from normal -- safety valves open, HP / LP bypass, operator intervention on alarms.
• Tripping of a Unit causes thermal shocks and reduces plant life; should be avoided / prevented as long as possible.
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• Coal to electricity efficiency : 30 – 35 %.
• Variable cost : 114 p/kWh, if coal cost (landed) is Rs 1500 / ton, consumption = 0.7 kg / kWh, aux = 8%.
• MCR goes up (down) when circulating water temperature goes down (up).
• Over-load capability: design margins, VWO, short-time over-stressing.
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• Oil support required below about 60% MCR, depending on which mills are operating.
• Turbine blades overheat if load < 20% MCR.
• Start-ups and controlled shut-offs require a few hours each, considerable operator effort & alertness, extra cost and reduce life.
• Daily shut-off not recommended, but Units with high fuel cost can be boxed up by turn.
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Combined cycle power plants
• Gas to electricity efficiency : 45 – 50 %.
• Critical parameter : Firing temp. of GT; direct effect on MW, efficiency, life, cost.
• MCR goes up (down) considerably when ambient temperature goes down (up).
• O/L capability only at the expense of life.
• GT operation at part - load is not desirable; one GT in a module should be switched off.
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• All CCPPs should be preparing for 2 - shift operation; may be Module-wise by turn.
• Gas supply system must have adequate “line - pack”.
• Frequency response only at the expense of life or efficiency. Operated in constant firing temperature mode. No FGMO.
• Full-load trip causes high thermal stresses and reduces GT life by 500 hours.
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Nuclear power plants
• No bulk mining; no bulk transport.
• No ash; no CO2 emission.
• Reactor power controlled by inserting / withdrawing the control rods.
• The critical parameter for stable reactor control : temperature differential of coolant across the reactor.
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Impact of frequency variations on generating stations
• When frequency falls, output capability of plants of all type goes down, due to slowing down of auxiliaries (for thermal & nuclear), and due to slowing down of compressors (for gas turbines).
• Frequency fluctuations have serious implications for Nuclear, but can be safely withstood by plants of other types.
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Safe shut down in emergency
• Turbine speed• Bearing lubrication; H2 sealing• Even cooling of turbine casing & rotor• Steam temperature & pressure• Furnace draft• Condenser vacuum• Reactor cooling• Plant lighting• Controls, alarms, fire-fighing.
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Idukki Generation 10th November’06
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0 2 4 6 8 10 12 14 16 18 20 22 0HRs
MW
48.5
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49.5
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50.5
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51.5
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Generation/Pumping at Kadamparai
10th November’06
-600
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HRs
MW
48.5
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49.5
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51.5
FREQ