27-07-2012, 03:12 PM
Advantages of 765-kV Technology
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Resource Conservation
1 A single-circuit 765-kV line can carry as much power as three single-circuit 500-kV
lines, three double-circuit 345-kV lines, or six single-circuit 345-kV lines, reducing the
overall number of lines and rights of way required to deliver equivalent capacity.
2 The high capacity of 765-kV can easily facilitate the efficient, economical integration of
large-scale renewable generation projects into the nation’s transmission grid.
3 765-kV projects use a minimum right-of-way width of 200 feet. Standard industry rightof-
way width for 500-kV is also 200 feet, and 150 feet for 345-kV construction. For
equivalent power carrying capability, lower voltages require more lines and as a result
more right-of-way.
4 Typical 765-kV lines have a tower height of approximately 130-140 feet. This is 30-40
feet shorter than a typical double-circuit 345-kV tower.
Performance and Design Efficiency
1 Power losses in a transmission line decrease as voltage increases. Since 765-kV lines
use the highest voltage available in the United States, they experience the least amount
of line loss.
2 The greater transmission efficiency of 765-kV can be attributed mainly to its higher
operating voltage (and thus lower current flow) and larger thermal capacity/low
resistance compared to lower voltage lines. This also allows 765-kV lines to carry power
over significantly longer distances than lower voltages.
3 With up to six conductors per phase, 765-kV lines are virtually free of thermal overload
risk, even under severe operating conditions.
4 By shifting bulk power transfers from the underlying lower-voltage transmission system
to the higher-capacity 765-kV system, overall system losses are reduced significantly.
Minimizing Costs
1 Use of 765-kV technology allows transmission builders to take advantage of economies
of scale. A typical 765-kV line costs approximately $2.6 million/mile. For equivalent
capacity, three 500-kV lines at a cost of $6.9 million/mile or six 345-kV lines at a cost of
$9.0 million/mile would be required. In other words, 765-kV construction is only 29% of
the cost of 345-kV and 38% of the cost of 500-kV for a comparable system.
2 Utilizing 765-kV results in a substantial reduction in system losses. For instance, a loss
reduction of 250 megawatts, equates to saving as much as 200,000 tons of coal, and
500,000 tons of CO2 emissions on an annual basis.
3 The addition of 765-kV systems relieves the stress on underlying, lower voltage
transmission systems, postponing the potential need for upgrades of these networks.
This results in additional savings for end-use customers over time. Our electric intensive
society relies on the reliable delivery of power. By designing bulk power transmission
systems to maximize efficiency and operational functionality, Pioneer Transmission is
working to ensure that we can meet the energy needs of the nation’s electricity users in
a responsible and cost-effective manner.