FUNDAMENTAL PRINCIPLES. 13
terminal drop just asif the load were concentrated at its
middle point. Hence, for all practical purposes, by making
this assumption, equations (1), (4), (5) can be used in
calculating the line.
To keep the voltage approximately uniform over a
linear system of distribution is comparatively easy. Inthe
most favorable case, a number of uniform loads moving uni--
formly, the drop is half that met with in the most unfavor-
able distortion of the load, 7. e., bunching at the end of the
line. ‘This latter condition brings the worst possible load
upon the station, barring short circuits. Although long
stretches of uniform conductor often occur in railway prac-
tice it is usual to reinforce the working conductor by feed-
ers variously arranged, as will be shown later. Such feed-
ers were very necessary in the early days when trolley wire
as small as No. 4 was used, but now, when No. oo is very
- g ¢
A i :
BIG: 7.
commonly employed, elaborate feeding systems are less
necessary for linear working. ‘The most important linear
distributions are likely to come in long interurban roads,
which often demand special methods of feeding. What-
ever these may be, the uniform working conductor is of
sufficient importance in every system to warrant this dis-
cussion of its general properties.
As a corollary to this general investigation, it is evi-
dent that in dealing with any linear system such as A B,
Fig. 6, the best point for the power station isat the middle
point of the line, since under the conditions of uniform load
supposed, this point would give the smallest average drop.
Since I, in such case is one-half of its value when the whole
line is fed from A, the total copper by equation (5) is re-
duced to one-fourth the amount for the same loss.
Considering now the branched type of distribution,
shown in Fig. 2, it is best to take it up in the simplest
available form. ‘This, Fig. 7, shows a main line, A B D,