4 Transmission and distribution of electrical energy
Figure 1.2 shows comparative costs of conductors and insulation
for increasing system voltages.
In addition to the cost of equipment there is the provision of land
to consider. The additional bulk of extra-high-voltage gear means
that substations may occupy land areas of hundreds or even thou-
sands of square metres.
In Figure 1.1 we see that major transmission is at 400 kV. Since
the power transmitted from a single power station may be in excess
of 2 000 MW, the high cost of insulation and switchgear is justified
by the considerable reduction in conductor costs. At distribution
level the supply for a single factory or