CHARACTERISTICS

The location of power transmission lines often does not optimize power delivery efficiency. This may be due to normal changes in customer demand, shifting of demand centers, or attempts to avoid installation of new facilities. However, proper placement of new transmission lines–especially in populated areas–may achieve significant reductions in transmission losses, and allow for trading of electricity from systems that may have excess capacity to those with capacity shortfalls.

Lowering transmission losses results in reduced generation requirements, with subsequent reductions in GHG emissions.

New transmission lines between utility systems allow excess capacity in one system, which may be more efficient and produce less GHG, to be made available to other systems with capacity shortages or more carbon-intensive fueled generation. Energy consumption for spinning reserves may also be reduced. New transmission line capacity connecting utility systems is generally required to achieve these results.

SIZE:
Alternating current transmission lines operating at voltages from 110 kV up to 765 kV.

FEATURES:
Design of lines to provide greater reliability, reduced resistance losses, reduced leakage currents and improved lightning performance.

COST:
Increase total line construction costs by 10% to 25%.

CURRENT USAGE:
Transmission line designs use composite silicon-based insulators, more precise design calculations of shielding angles, and economic conductor selection.

POTENTIAL USAGE:
Improved relaying with high speed re-closing, improved insulation to reduce Corona and pollution losses, and high phase order (six phase) transmission lines. Also some potential for use of Gas Insulated Transmission and solid dielectric insulated cable systems.

ISSUES ASSOCIATED WITH IMPLEMENTING ACTION

• Inter-utility transmission lines may not be considered "used and useful" by regulators, and could possibly be excluded from the utility rate base.
• Competitive opportunities may be created when electricity users have transmission alternatives.
• The regulatory process for the routing and permitting of transmission line projects can be a deterrent.
• Public opposition and concern with EMF and the construction of new transmission lines can increase the difficulties in undertaking new projects.
• Underground transmission lines are expensive.

CLIMATE CHANGE IMPACT

EMISSION EFFECT:
    

CONDITIONS FOR EMISSIONS MITIGATION:

• Emissions are avoided when generation is shifted from lower-emitting sources to meet demand that would otherwise be met by higher-emitting source. For example, installing a new line to transport power generated by a natural-gas burning facility instead of adding capacity at a coal-fired power plant.

EMISSION ESTIMATE:
N/A

COST-EFFECTIVENESS:
N/A

SECONDARY EFFECTS:
N/A

RESOURCES

• U.S. Office of Technology Assessment; Electric Power Wheeling and Dealing; Technological Consideration for Increasing Competition; OTA-E0409; Washington D.C.; U.S. Government Printing Office, May, 1989.

CONTACTS

ABB Power T&D
Henry Chao
Raleigh, NC
Tel: (919) 856-2394
http://www.abb.se/pow/home.htm

Electric Power Research Institute
Mark Wilhelm
Director, Power Delivery Group
Palo Alto, CA
Tel: (650) 855-2771
mwilhelm@epri.com
http://www.epri.com/pdg/trans

Harza Engineering
Peter Donalek
Electric Power Systems Department
Chicago, IL
Tel: (312) 831-3170
Fax: (312) 831-3999
Pdonalek@harza.com
http://www.harza.com