Electric Power Generation, Transmission, and Distribution

0

500

1000

1500

2000

2500

3000

3500

4000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

Electric energy usage (billion kWh)

0

20

40

60

80

100

120

140

160

180

High-voltage lines (miles



1000)

Annual electric energy usage

High-voltage transmission line miles

FIGURE 16.11 Growth of the US High Voltage Transmission Network and annual electric energy usage over the
past 50 years. In addition to increasing total network size, the network has grown in complexity with introduction of
higher kilovolt-rated lines that subsequently also tend to carry larger GIC flows. (Grid size derived from data in EHV
Transmission Line Reference Book and NERC Electricity Supply and Demand Database; energy usage statistics from
US Department of Energy—Energy Information Agency.)

0.001

0.01

0.1

1

kV Rating

Resistance (

Ω

/km)

115 kV

138 kV

161 kV 230 kV 345 kV 500 kV

765 kV

FIGURE 16.12 Range of transmission line resistance for the major kilovolt-rating classes for transmission lines in
the US electric power grid infrastructure population. Also shown is a trend line of resistance weighted to average.
The lowerRfor the higher voltage lines will also cause proportionately larger GIC flows in this portion of the power
grid. (Derived from data in EHV Transmission Line Reference Book and from US Department of Energy, Energy
Information Agency and FERC Form 1 Database.)