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.