by the utilities and was used in this study. An LOLP of .1 days/year = -4 3.83 x 10 . Each piece of generating equipment required to meet the loads described in Equations 2.8 and 2.9 must be taken offline sometime during the year for scheduled maintenance. In order that this activity can later be taken into account, it is necessary to break the year up into ''maintenance intervals”. The number of machines in the power pool scheduled to be available does not change during a maintenance interval. In utility practice, the year is broken up into thirteen (13) four week intervals. Because of the double yearly peak assumed for our model load curves, thirteen intervals turned out to be inconvenient; instead fourteen (14) intervals, each 26 days long, were used. Two of these intervals (numbers 1 and 8) are centered about the summer and winter peaks. Four of these intervals (numbers 4, 5, 10 and 11) have one of the days at the end of the interval occurring at one of the two equinoxes, the days when the daily peak is at a minimum. 6t^m is the length of time (hours) during each maintenance interval, £, when the demand for power is between m and m-1 gigawatts. Using equation 2.8 it is possible to calculate the values of 6t^ for each maintenance interval for the three primary power pools. (See Appendix A.) The composite power pool has three major components. Two of the components are power pools (in each power pool, the yearly peak demand for power is 30 GWe) and the third component is a 5 GWe capacity SPS which can feed its output into either power pool as required. The demand for power in each of the power pools as a function of the time- of-day is shown in Figure 2.5. P_ represents a power pool on the East Coast and represents a power pool on the West Coast. The demand for power in P is greater than the demand in P_^_ for t between 0 and 12 hours. The opposite is true for t between 12 and 24 hours. For
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