SUBSTATIONS. 127%
transmission of all the power from some one point with sub-
stations at one or more of the others? .
Of the plans with two generating stations, that with
stations at A and Bis undoubtedly the better since the ter-
minal loads are so considerable. ’The single station at D
requires a little consideration, because the difference in
cost of power between a 500 k.w. station and two 250 k.w.
stations is very material. Of the possible transmission
plants, that comprising a generating plant at one end of
the line and a substation at or near the other is at first
glance the most promising. For the total amount of power
to be transmitted is very moderate and the subdivision of
even this by using two or more substations would only
involve useless expense.
We may now compare more closely the plan calling
for stations at A and B with that for the installation of a
single plant at the point D. On the one hand we have the
economy of the larger station—on the other the cost of
distributing 200 k.w. at a point ten miles from home.
A ' i : B
C D E
BTG /L
Assuming the yearly differences in cost of power be-
tween a 500 k. w. station and two 250 k. w. stations to be
about $o0.4 per kilowatt hour in favor of the former, the
yearly differenceis $14,600. Now for the approximate cost
of feeder copper. If a simple station at D be used we must
practically allow for 400 k. w. delivered at a distance of ten
miles. Using the formula employed in the previous cases
L 42CE m
-
W
and assuming ten per cent drop we have a call for 940 tons
of feeder copper costing about $263,000. Even at twenty
per cent loss the feeder copper would amount to more than
$130,000, exclusive of the nearer distribution. ‘This settles
the matter off hand, for with two stations the average dis-
tance of transmission would be hardly more than three to