(c) Size of Sets
Whilst the capital, revenue and manpower cost per
KW of plant installed decreases with increased size of
set, care must be taken to ensure that the size of set
is geared to the maximum and minimum demand of the daily
load curves.
The large sets now being installed throughout the
world have in recent years had a much lower availability (they are less reliable because of high steam pressure and temperature) than the earlier sets of smaller capacity.
The fuel savings have therefore been less than expected
and there is now an even greater financial incentive to
improve availability rather than thermal efficiency.
Low availability of high merit plant also leads to a
thermal efficiency which is less than the design figure
due to the many stops, starts and part loading.
Technical Limit to Maximum Size of Set for System
The CLP system will require additional generating
capacity in 1981 when the expected maximum demand is
about 1800 MW. The system would then be able to
accommodate generating sets of higher rating than the
existing 200 MW sets. However, there is a limit to the
size of set that the system could operationally
accommodate, thus excluding the very large sets that
are currently available.
The power system must be operated with a balance
between generation and demand otherwise the system
frequency changes. If a sudden breakdown of plant
occurs there is a drop of frequency due to the loss of
generation. Providing the loss is not too great the Partly loaded sets running on the system (spinning reserve) would increase their generation to restore
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