Chapter 5 - Publications, US Army Corps of Engineers

EM 1110-2-1701
31 Dec 1985
record SSR routings to estimate annual energy output and dependable
capacity (see Section 7-6).
(7) &stem Studies. Where a project is operated as a part of a
system, SSR analysis is required to properly model the impact of
system operation on that project’s power output. The only case where
the flow-duration or hybrid method might be used would be in the
examination of a single existing project with no power storage, where
an adequate historical record exists, no changes in project operation
are expected, and no changes in streamflow resulting from the
regulation of upstream projects are expected.
5-5. ine Character~
a. &ner& Certain turbine characteristics, such as efficiency,
usable head range, and minimum discharge, can have an effect on
a hydro project’s energy output. For preliminary ~wer studies, it is
usually sufficient to use a fixed efficiency value and ignore the
minimum discharge constraint and possible head range limitations.
However, for a feasibility level study, these characteristics should
be accounted for in cases where they would have a significant impact
on the results. This section presents some general information on the
turbine characteristics required for making power studies and on the
operating parameters involved in the selection of a specific turbine
design.
(1) A variety of turbine types are available, each of which is
designed to operate in a particular head and flow range. Figure 2-35
illustrates the normal operating ranges for each type. In addition, a
specific turbine is capable of operating within a limited head range.
A horizontal Kaplan unit, for example, has a ratio of maximum head to
minimum head of about 3 to 1. Table 5-1 (Section 5-6i) describes the
usable operating head range for each of the major turbine types.
(2) Where possible, a runner design is selected such that the
turbine can operate satisfactorily over the entire range of expected
heads. This is especially important in the case of storage projects,
where drawdown characteristics may be a major factor in selection of
the type of turbine to be installed. At storage projects with a wide
head range, it is sometimes possible to utilize interchangeable
runners in order to ❑aintain generation over the full head range.
(3) When adding power facilities to projects not originally
designed for power operation, head ranges may exceed the capabilities
of any turbine type. Examples are (a) low head projects where the
5-1o