Handbook of Electrical Engineering

10 HANDBOOK OF ELECTRICAL ENGINEERING

Table 1.10 shows the values of the load factorFiand the overload factorFofor a range of
typical power consumptionsPl. The values ofPgare the site requirements and relate approximately
to the ratings of gas-turbine generators that are available and used in the oil industry i.e. 2.5 to
40.0 MW.

The table was compiled by constrainingFiandFoto be within good practical limits,

66 .7%
Fi
 90 .0%

and
80
Fo
125%

Table 1.10. Selecting generator ratings on the basis ofN−1 capacity with tolerance of overloading

Power
consumption
(MW)Pl

Initial

load factor

(%)

Fi

Number of

installed

generators

N

Generator rating at

site conditions

(MW)

Pg

Turbine ISO ratings

for a site amb. temp

of 40◦C(MW)

Piso40

Final load

factor

(%)

Fo

10 66.7 4 5.0 5.9 100.0

10 74.1 4 4.5 5.3 111.1

10 83.3 4 4.0 4.7 125.0

10 71.4 5 3.5 4.1 95.2

10 83.3 5 3.0 3.5 111.1

10 66.7 6 3.0 3.5 83.3

10 80.0 6 2.5 2.9 100.0

15 66.7 4 7.5 8.8 100.0

15 75.0 5 5.0 5.9 100.0

15 83.3 5 4.5 5.3 111.1

15 66.7 6 4.5 5.3 83.3

15 75.0 6 4.0 4.7 93.8

15 85.7 6 3.5 4.1 107.1

20 66.7 4 10.0 11.8 100.0

20 66.7 5 7.5 8.8 89.9

20 80.0 6 5.0 5.9 100.0

20 88.9 6 4.5 5.3 111.1

25 69.4 4 12.0 14.1 104.2

25 83.3 4 10.5 11.8 125.0

25 83.3 5 7.5 8.8 111.1

25 66.7 6 7.5 8.8 83.3

30 71.4 4 14.0 16.5 107.1

30 83.3 4 12.0 14.1 125.0

30 75.0 5 10.0 11.8 100.0

30 80.0 6 7.5 8.8 100.0

40 66.7 4 20.0 23.5 100.0

40 74.1 4 18.0 21.2 111.1

40 83.3 4 16.0 18.8 125.0

40 71.4 5 14.0 16.5 95.2

40 83.3 5 12.0 14.1 111.1

40 66.7 6 12.0 14.1 83.3