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
1917First major mine-mouth power plant, Windsor Plant in West Virginia, and long-distance transmission to load center, Canton, Ohio, 55 miles away.
1920First application of carrier-current telephony to transmission lines for system dispatching.
1926Methods developed for transmission line lightning protection.
1929First high-speed carrier-current relaying.
1929First use of automatic frequency and tie-line load control.
1935First ultra-high-speed (one cycle or 1/60th of a second), 138-kilovolt (kV) high-voltage reclosing circuit breaker.
1937First sleet melting of transmission line.
1947First extra-high-voltage (EHV) line testing up to 500kV, Tidd Project in Ohio.
1948First aerial inspection of transmission line.
1951First electronic line relay.
1953First EHV transmission line (energized at 330kV), between Sporn and Kanawha River stations in West Virginia.
1953First hot-line maintenance of EHV line.
1958First 345-kV interconnection, AEP System and Commonwealth Edison.
1960First large-scale use of helicopters in transmission line construction.
1961First two-cycle, high-voltage air-blast circuit breaker.
1961First bare-hand maintenance of EHV line.
1961First use of guyed-V aluminum tower for transmission line.
1961First EHV transmission line testing up to 775 kilovolts, Apple Grove Project in West Virginia.
1962First two-cycle, 345-kV air-blast circuit breaker.
1965First field research in use of sodium as transmission conductor.
1966First use of laser beam to monitor transmission line.
1969First 765-kV transmission line, between Baker and Marquis stations in Kentucky and Ohio, respectively.
1969First two-cycle, 765-kV air blast circuit breaker.
1971First 765-kV interconnection, AEP System and Commonwealth Edison.
1975First 3,000 megavolt-ampere transformer bank, Marysville Station in Ohio.
1976First sustained operation of ultra-high-voltage (UHV) line at 2,000,000 volts, AEP/ASEA UHV Research Center at North Liberty, Indiana.
1978First successful testing of transmission current-limiting device.
1978First utility with 100 high-voltage or extra-high-voltage transmission interconnections.
1979First operation of 765-kV station using sulfur hexafluoride (SF6) gas, rather than air, as insulation.
1979First single-phase fault clearing and reclosing of untransposed 765-kV transmission line.
1980First application of Static VAR System (SVS) to maintain voltage on transmission grid, Beaver Creek Station in Kentucky.
1980First use of microprocessors in substation protective relaying.
1984First live-tank SF6 "puffer" type circuit breaker (765-kV), Jefferson Station in Indiana.
1984First installation of an Optical Ground Wire (OPGW) in North America (communications between AEP Headquarters and Columbia Center in Columbus, OH).
1985First transmission line surge arrester installation on 138-kV lines.
1986Nation's highest-capacity transmission network — more than 2,000 miles of 765-kV lines — in commercial operation.
1991Largest 345-kV series capacitor (788 megavolt-amperes) with thyristor control east of Mississippi River, Kanawha River Station in West Virginia.
1994First use of “open loop” shield wire design with gapped insulators on extra-high voltage lines to reduce power losses.
1998First Unified Power Flow Controller (UPFC) on transmission system, Inez Station in Kentucky.
1999First transmission bridge capacitor, Leslie Station in Kentucky.
2000First back-to-back asynchronous voltage-sourced converter, Eagle Pass Station in Texas.
2000First use of 765-kV transmission line surge arrestors instead of closing resistors in circuit breakers.
2001First 765-kV dead-tank SF6 circuit breaker, Maliszewski Station in Ohio.
2006First use of six-conductor phase bundles in North America for 765-kV line in AEP’s Appalachian service area.
2006First high temperature superconducting (HTS) triaxial cable demonstration, Bixby Station in Ohio.
2006Industry’s first implementation of virtual digital fault recorders.
2007First variable frequency transformer (VFT) in U.S. and on international border. Second VFT in world.
2008First 765-kV dead tank breaker equipped with closing resistor installed at Hanging Rock Station.
2008First utility in the U.S. to standardize on detailed functional transmission designs across all operating companies system-wide, allowing development and deployment of standard P&C wiring designs at a panel level (in 2008) and at the control building level (in 2011).
2011AEP’s first prefabricated drop-in control module is installed at the West Millersport Station in Ohio.
2014First ultra-high frequency partial discharge online monitoring for extra-high voltage transformers in North America.
2014First prevented catastrophic failure of an extra-high voltage transformer using a full online monitoring package (including partial discharge, dissolved gas analysis, etc.).
2014First North American installation of inter-phase insulators to detune galloping line on the Tanners Creek-Sorenson 345-kV line.
2014First site visit using a variety of virtual tools to allow a core team at the site to collaborate with stakeholders located at multiple physical locations.
2015First installation of modular ballistic and firewall protection for a 765-kV transformer bank at a 765-kV station to enhance physical security of bulk transmission stations.
2015First application of ground study, using fault current flow concepts and strategies dealing with different soil structures, to design a safe and optimized ground grid for 765, 500, and 345-kV yards at the Cloverdale Station.
2015First design of a 1.3 megavolt portable resonant test set in North America for use on 765-kV circuit breakers.
2015First use of common frame 345-kV circuit breaker utilizing full, non-limiting phase spacing. Equipment shipped fully assembled to reduce construction time and improve reliability.
2015The longest live-line reconductoring project of North America involved a pair of 120-mile, 345-kV transmission lines between Corpus Christi, Texas, and the Lower Rio Grande Valley. Project is also the largest installation of the advanced aluminum composite core conductor in the world.
2015First enterprise application of Asset Health Center software across a fleet of transformers, circuit breakers and batteries.
2016First deployment of AEP Transmission's BOLD™ (Breakthrough Overhead Line Design) transmission line is energized, Robison Park–Sorensen line in Fort Wayne, Indiana.
2016First ultra-high frequency partial discharge monitoring of underground transmission cable in North America.
2016First substation in the country with a fully implemented fiber-based protection and control system at the Flag City substation in Findlay, Ohio.
2016First use of factory built, prefabricated station busses at 138-kV East Willard Station in Ohio.
2016First use of integrated design and 4-D modeling during construction of 345-kV Blessing Station.
2017First use of aerial photogrammetry and 4-D modeling for progress reporting and as-built documentation during construction of 138-kV Karl Road Station in Columbus, Ohio.
Issues In Electricity


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