156 SECTIONAL ADDRESSES 
capital and maintenance charge of 6-75 per cent. ‘There is 10 per cent. 
drop on full load at power factor 0-8 in the line and transformer windings 
at each end, and core losses are 1-25 per cent. At unity load factor 
the energy loss is directly subtracted from the station output, and must 
be charged at the cost of production, as given in Fig. 1. For lower 
load factors the exact figure to be allowed is not more than this, and is 
probably slightly less, but as the loss is small, the unity load factor value 
for the units loss has been taken all through for the coal stations and for 
FIG. 2. 100 MILE TRANSMISSION 
A. HYDRO-ELECTRIC WITH RESERVOIR 
STEAM STATION 
. PIT HEAD & HYDRO-ELECTRIC 
. GALLOWAY 50 MILES 
PIT HEAD 40 MILES 
B 
iS 
= 
= 
= 
= 
IN= PE NGE 
COST 
ie 
coon 
pao 
Saaoas 
aaa 
LOAD FACTOR 
the £40 hydro-electric station without reservoir. But the station working 
on a reservoir has only a certain amount of energy per annum to sell, 
and the wasted energy is charged at the value for the load factor, which 
increases the cost at low load factors. Below 0-6 there is little difference 
between them. There isa definite minimum at about 0-6, which can be 
shifted to a lower load factor by increasing the load and line loss, if this 
does not cause regulation troubles. There is also shown the cost of 
transmission over 50 miles from the Galloway stations, and the cost over 
40 miles from a pit-head station, which was the distance taken above 
as in the neighbourhood. 
These costs may be compared with the cost of rail and of sea carriage 
of raw coal. Rail transport is in general one penny per ton mile plus 
