C. Turbine-Generator Unit Performance
hydroelectric units. These curves provide basic data for scheduling loading on hydrounits to obtain desired
water releases and electrical generation with optimum efficiency.
Unit performance data for one specific hydraulic head are determined from Gibson or salt-velocity tests
which are usually performed at a new installation as part of the hydrounit acceptance tests. Data for other
hydraulic heads, within a plus or minus 10 percent range of the Gibson or salt-velocity test head, are
computed by extrapolation formulea to provide a family of curves. Since extrapolation for heads beyond a
plus or minus 10 percent range usually produces appreciable error, measurements, are made at other heads
outside this range, to provide additional data from which to extend the head range, using the same
extrapolation method, until the entire operating head range of the unit has been covered.
In lieu of a family of curves, the performance data also can be made available in tabular form as shown in
tables I and II.
In some Operating Areas, personnel have found that the data presented in that form are more convenient
for day-to-day operating purposes.
Reasonable accuracy in the collection of test data and performance of the related extrapolation ordinarily
will produce results within plus or minus 2 percent accuracy for the head range covered, whether the data
are presented in curve or tabular form.
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(FIST 1-3 12/89)