Chapter 5 - Publications, US Army Corps of Engineers

EM 1110-2-1701
31 Dec 1985
obtained over the entire operating range if desired (Figure 5-5). At
other projects, the head range is such that the operating head drops
below the rated head under some operating conditions, with a resulting
decrease in generating capability. Examples of the latter are (a) a
storage project with a large drawdown, where head drops below rated
head at low pool elevations (Figure 5-6), and (b) a pondage project
with a large installed capacity, where the tailwater encroachment at
high plant discharges causes head to fall below rated head. Figure
5-7 illustrates a capacity versus discharge curve for various numbers
of 5 megawatt units at a low head run-of-river project. This figure
shows how output can drop off at the higher discharge levels due to
tailwater encroachment.
MAXIMUM ALLOWABLE HEADOFTU7RBINE
——. -— — ————— — ——— — — —-—— —-— —
.-_— -
PROJECT OPERATING
HEAD RANGE
/
/
/
––_–__.r_7_
/ GENER~~TO~ /’ //
/
~
/ -/
CAPACITY
Figure 5-5. Turbine design from Figure 5-4 as applied
to a project with a narrow operating head range
5-14