Electrical Power Systems

414 Electrical Power Systems
\ l 2 = l 2 min = 39.92 Rs/MWhr.
At P g2 = P g2 max = 130 MW
\ l 2 = l 2 max = 0.36 Pg2 max + 32 = 0.36 × 130 +32
\ l 2 = l 2 max = 78.8 Rs/MWhr.
igure 16.6 gives the incremental cost curves of two units.
ig. 16.6: Incremental Cost Curves.
At the bottom point P g1 min (32 MW) > Pg2 min (22 MW), Therefore, Pg1 is fixed at 32 MW and
P g2 is fixed at 22 MW (i.e., P D = 32 + 22 = 54 MW).
Now l 1 min = 46.76 Rs/MWhr, l2 min = 39.92 Rs/MWhr so l2 min < l1 min , therefore as the plant
load increases beyond 54 MW, the load increment will be taken up by unit 2, till both units have
l = 46.76 Rs/MWhr.
At l = l 2 = 46.76 Rs/MWhr,
0.36 P g2 + 32 = 46.76
\ P g2 = 41 MW
Therefore at l = l 1 = l 2 = 46.76 Rs/MWhr,
P D = (32 + 41) = 73 MW.
or 39.92 < l < 46.76
l = 0.36 P g2 + 32 ...(i)
But
P g2 + P g1 min = PD
\ P g2 = P D – 32 ...(ii)
rom eqn. (i) and (ii), we get
\ l = 0.36P D + 20.48 ...(iii)