1 GENERATION TECHNOLOGIES -- Bhanu Bhushan -- (April, 2011)

2 Thermal -- Coal / Lignite Gas turbine / Combined cycle Hydro -- Storage / R-o-R / Pumped Nuclear Wind and other Renewable Captive and Co-generation

3 Process Conversion efficiency Variable cost Peaking capability

4 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

5 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

6 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.

7 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.

8 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.

9 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.

10 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.

11 Nuclear power plants No bulk mining; no bulk transport. No ash; no CO 2 emission. Reactor power controlled by inserting / withdrawing the control rods. The critical parameter for stable reactor control : temperature differential of coolant across the reactor.

12 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.

13 Safe shut down in emergency Turbine speed Bearing lubrication; H 2 sealing Even cooling of turbine casing & rotor Steam temperature & pressure Furnace draft Condenser vacuum Reactor cooling Plant lighting Controls, alarms, fire-fighing.

14 Idukki Generation 10 th November’06

15 Generation/Pumping at Kadamparai 10 th November’06