Transmission Firsts

AEP has been a leader in the development of transmission technology since the earliest days of its history. AEP energized the first long-distance transmission line connecting a mine-mouth power plant with a major load center in 1917.

Since that time, the company has continued the pursuit of new and better ways to transmit electricity from its efficient fleet of power stations to the cities and industries it serves.

Year Event
1917 First major mine-mouth power plant, Windsor Plant in West Virginia, and long-distance transmission to load center, Canton, Ohio, 55 miles away
1920 First application of carrier-current telephony to transmission lines for system dispatching
1926 Methods developed for transmission line lightning protection
1929 First high-speed carrier-current relaying
1929 First use of automatic frequency and tie-line load control
1935 First ultra-high-speed (one cycle or 1/60th of a second), high-voltage reclosing circuit breaker (138,000 volts)
1937 First sleet melting of transmission line
1947 First extra-high-voltage (EHV) line testing up to 500,000 volts, Tidd Project in Ohio
1948 First aerial inspection of transmission line
1951 First electronic line relay
1953 First EHV transmission line (energized at 330,000 volts), between Sporn and Kanawha River stations in West Virginia
1953 First hot-line maintenance of EHV line
1958 First 345,000-volt interconnection, AEP System and Commonwealth Edison
1960 First large-scale use of helicopters in transmission line construction
1961 First two-cycle, high-voltage air-blast circuit breaker
1961 First bare-hand maintenance of EHV line
1961 First use of guyed-V aluminum tower for transmission line
1961 First EHV transmission line testing up to 775,000 volts, Apple Grove Project in West Virginia
1962 First two-cycle, 345,000-volt air-blast circuit breaker
1965 First field research in use of sodium as transmission conductor
1966 First use of laser beam to monitor transmission line
1969 First 765,000-volt transmission line, between Baker and Marquis stations in Kentucky and Ohio, respectively
1969 First two-cycle, 765,000-volt air blast circuit breaker
1971 First 765,000-volt interconnection, AEP System and Commonwealth Edison
1975 First 3,000 megavolt-ampere transformer bank, Marysville Station in Ohio
1976 First sustained operation of ultra-high-voltage (UHV) line at 2,000,000 volts, AEP/ASEA UHV Research Center at North Liberty, Indiana
1978 First successful testing of transmission current-limiting device
1978 First utility with 100 high-voltage or extra-high-voltage transmission interconnections
1979 First operation of 765,000-volt station using sulfur hexafluoride (SF6) gas, rather than air, as insulation<
1979 First single-phase fault clearing and reclosing of untransposed 765,000-volt transmission line
1980 First application of Static Var System (SVS) to maintain voltage on transmission grid, Beaver Creek Station in Kentucky
1980 First use of microprocessors in substation protective relaying
1984 First live-tank SF6 "puffer" type circuit breaker (765,000-volts), Jefferson Station in Indiana
1986 Nation's highest-capacity transmission network -- more than 2,000 miles of 765,000-volt lines -- in commercial operation
1991 Largest 345,000-volt series capacitor (788 megavolt-amperes) with thyristor control east of Mississippi River, Kanawha River Station in West Virginia
1994 First use of “open loop” shield wire design with gapped insulators on EHV lines to reduce power losses
1998 First Unified Power Flow Controller (UPFC) on transmission system, Inez Station in Kentucky.
1999 First transmission bridge capacitor, Leslie Station in Kentucky
2000 First back-to-back asynchronous voltage-sourced converter, Eagle Pass Station in Texas
2000 First use of 765,000-volt transmission surge arrestors instead of closing resistors in circuit breakers
2001 First dead-tank SF6 circuit breaker (765,000 volts), Orange Station in Ohio
2006 First use of six-conductor phase bundles in U.S. for 765,000-volt line in AEP’s Appalachian service area
2006 First High Temperature Superconducting (HTS) triaxial cable demonstration, Bixby Station in Ohio
2007 First back-to-back HVDC with black start bypass breaker interconnecting AEP Texas and Mexico transmission grids
2007 First Variable Frequency Transformer (VFT) in US and on international border. Second VFT in world.
2010 First application of broadband over power line carrier (BPL) at 69 kV (2007) and 138 kV levels (2010).
Late 2012 First installation of an 800-kV circuit breaker and a 765-kV drop-in control module at Don Marquis Station, Ohio.
November 2012 First installation of an AEP Transmission skid-mounted substation occurs in Ozona, Texas; a second unit went into service in Ohio the next month.
April 9, 2013 First "station in a box," a unique pre-packaged substation designed to cut in half the typical 18-month construction period for a permanent station, is energized at Catarina, Texas.
2014 First installation of AEP Transmission's BOLD (Breakthrough Overhead Line Design) design, featuring an elegant and high capacity design, between Sorenson and Robison Park stations in Fort Wayne, Indiana.
Issues In Electricity


AEP’s historical leadership in transmission engineering has set the stage for its latest transmission initiatives.