Overview

E.C. (Rusty) Bascom, III

Senior Engineer, Power Delivery Consultants, Inc.; Senior
Member, IEEE

A.M.DiGioia, Jr.

President, GAI Consultants, Inc.; Fellow, ASCE; Member, IEEE

D.A.Douglass

Senior Consultant, Transmission, Power Technologies, Inc.;
Fellow, IEEE

I.S.Grant

Executive President, International Operations, Power
Technologies, Inc.; Fellow, IEEE

J.D.Mozer

Technical Supervisor, GAI Consultants, Inc.; Member, ASCE

J.R.Stewart

Consultant, Fellow, IEEE

H.Brian White

Consulting Transmission Line Engineer; Fellow, IEEE

J.A.Williams

Principal Engineer, Power Delivery Consultants, Inc.; Senior
Member, IEEE

14.1 OVERHEAD AC POWER TRANSMISSION

Overhead transmission of electric power remains one of the most important elements of today's electric power system. Transmission systems deliver power from generating plants to industrial sites and to substations from which distribution systems supply residential and commercial service. Those transmission systems also interconnect electric utilities, permitting power exchange when it is of economic advantage and to assist one another when generating plants are out of service because of damage or routine repairs.

Since the beginning of the electrical industry, research has been directed toward higher and higher voltages for transmission. As systems have grown, higher-voltage systems have rarely displaced existing systems, but have instead overlayed them. Economics normally dictate that an overlay voltage should be between 2 and 3 times the voltage of the system it is reinforcing. Thus it is common to see, for example, one system using lines rated 115, 230, and 500 kilovolts (kV). The highest ac voltage in commercial use is 765 kV. Research and...