When American Electric Power decided in 1991 that its proposed 765-kV transmission line from West Virginia to Virginia would include the first six-wire bundles in North America, almost 50 years of engineering advances — rarely accomplished easily — were behind the decision. Following are some of AEP's transmission advances.

1946	AEP's first extra-high-voltage (EHV) lab construction was started adjacent to the Tidd Plant near Steubenville, Ohio. AEP's highest voltage transmission lines operated at 138 kV at the time. Tidd lab voltages could be varied between 265 kV and an unheard of 532 kV. Higher-capacity lines were needed to accommodate the larger output of generating units, 150 MW during the 1940s.
1950	AEP concluded that 330 kV (later increased to 345 kV) was the optimal transmission voltage.
1953	The first 345-kV line went into service. Problems with audible noise and radio interference caused operating voltage reduction to the familiar 138 kV. Measures implemented included: strict conductor-handling guidelines being adopted and conductor size increased from a 1.6-inch to 1.75-inch (40.6-mm to 44.4-mm) diameter. Performance improved greatly after several years of weathering.
1958	The first section of bundled two-wire 345-kV lines went into service. Previously, all 345-kV lines had a single wire per phase. AEP built a total of about 3800 circuit miles (4830 km) of 345-kV lines.
1960	A larger transmission test lab at Apple Grove, West Virginia, replaced the Tidd operation. A five-year program was started to test voltages up to 775 kV and combinations of four-wire bundles.
1966	Based on this R&D and the need to accommodate 800-MW units, AEP announced it would build a new network — 1050 circuit miles (1658 km) in five states — of 765-kV transmission lines to overlay its existing grid. (The previous November, Hydro-Québec announced plans to build the world's first 735-kV line, which became Canada's Manic-Boucherville line, completed three years later.)
1969	Problems arose with corona-caused noise in wet conditions, especially at higher elevations. As a stopgap, new lines were operated at lower voltage while the conductors aged. The original 765-kV phase bundle consisted of four 1.165-inch (30-mm)-diameter Rail (954-kcmil ACSR) wires arranged in a square with sides of 18 inches (457 mm).
1972	AEP's originally proposed 1050-mile 765-kV system was essentially completed. The advent of 1300-MW generating units called for additional 765-kV lines.
1974	Subsequent 765-kV system expansion used larger 1.385-inch (35 mm) Dipper (1351.5-kcmil ACSR) conductors. This reduced noise and line losses.
1968 to 1987
	These early 765-kV operational problems spawned five generations of mobile laboratories. Increasingly sophisticated data-gathering vans measured and recorded both corona and electromagnetic phenomena throughout the system.
1985	Completion of 20th century additions to AEP's 765-kV system: 24 years from planning to completion, 2022 miles (3254 km), 5300 steel towers, 2200 aluminum towers, 24,500 miles (39,429 km) of conductor and 2.5 million ceramic insulators.
1990	The need to reinforce the bulk transmission delivery system in southern West Virginia and southwest Virginia led to AEP's proposal to extend its 765-kV system from its Wyoming Station (Oceana, West Virginia) 110 miles (177 km) to its Cloverdale Station (Roanoke, Virginia).
1998	During regulatory proceedings in Virginia, however, the line's destination was changed to Jacksons Ferry Station. The West Virginia Public Service Commission approved the project.
2001	The Virginia State Corporation Commission issued its final order approving the project.
2002	The lead federal agency, the U.S. Forest Service, granted approval to construct the line.
2003 to 2004
	Right-of-way clearing began in December 2003; tower foundation construction started in April 2004; and, the first tower was erected in August 2004.
2006	AEP's Wyoming-Jacksons Ferry 765-kV line was energized in June 2006, the first such line in North America with six-wire bundles. — Chronology supplied by AEP

Elevation		Operation voltage on 765-kV base
(ft)	(m)	1.0 p.u. (dBA)	1.02 p.u. (dBA)	1.04 p.u. (dBA)
800	244	49.0	50.0	51.0
2500	762	50.7	51.7	52.7
3800	1159	52.0	53.0	54.0

Approximate foul-weather mean audible noise levels at the edge of a 200-ft (61-m)-wide right-of-way. (Note: Table shows noise levels as a function of elevation and operation voltages for 765-kV line using 6-Tern design.)

Bundle diameter for 6-Tern		Audible noise reduction below 4-Dipper at 25.5-inch (648-mm) bundle diameter
(inches)	(mm)	(dBA)
25.5	648	4.6
28	711	4.9
30	762	5.1

Audible noise reduction of various 6-Tern bundle diameters, compared with 4-Dipper at a 25.5-inch diameter.

You want to string and tension a six-wire bundle on your latest transmission line project. The device that does this is a tensioner. So you go to your local transmission line building supply store and find the tensioner aisle. There are single-, dual-, triple- and quad-conductor tensioners. But, the six-conductor version seems to be out of stock. No, a stock check reveals the store never ever had them. It's a special order item.

PAR Electrical Contractors (Kansas City, Missouri, U.S.), a division of Quanta Services, was in such a situation when it contacted Lloyd Morgan at Morpac Industries Inc. (Vancouver, Canada) regarding a six-conductor bundle tensioner for AEP's new 765-kV line. The good end to this story is that PAR ordered two machines, and Morgan designed, built and delivered the first unit in 120 days. But, there is, of course, more to the story.

Born in 1918 and still working every day, Lloyd Morgan started as a line contractor in 1956 and subsequently began developing his own line of high-quality line-stringing equipment. Early field experience led Morgan to an important realization: smaller line crews outfitted with the best tools and equipment resulted in safer, more cost-effective and productive line-stringing operations. Founded as Morgan Power Apparatus, and currently doing business as Morpac Industries Inc., the Morgan name has always been associated with state-of-the-art stringing equipment known for exceptional quality and ruggedness.

Morpac has built many tensioners over the decades ranging from one-wire to four-wire configurations, most of which are built to customers' specifications. Never having built a six-wire tensioner, this new design was loosely based on a tensioner that can be configured in several combinations of bullwheel sizes and bundle numbers. But, this machine required mostly custom parts to fit all six pairs of bullwheels and their associated hardware.

As with all Morgan equipment, this tensioner is equipped with both innovative and decades-old, time-tested features. Half of the bullwheels on the tensioner are tilted to allow the conductor to advance to the next groove on the straight bullwheels without having side load on the wire. The side load often generates a twisting force in the wire, which can eventually lead to failure of the pulling line or conductor if not dealt with properly.

The tensioner is also equipped with an ecologically friendly Cummins 130-hp engine. It is run during tensioning as a giant flywheel to eliminate wire oscillations during the stringing operation. It also allows the tensioners to be used for sagging up to 20,000 lbs per wire.

Providing the tensioning force to Morpac's tensioners is a huge water-cooled brake manufactured by Eaton (Cleveland, Ohio). The coolant runs through a gigantic twin-core radiator capable of expelling up to 540 hp worth of heat in the harshest conditions. This brake has a fine and coarse adjustment and each conductor is individually controlled via its own clutch.

Each drive bullwheel has its own expanding-bladder clutch, which allows it to be operated independently for operations such as sagging, leveling the running board while tensioning or steering the running board through angle towers. This clutch, measuring 20.25 inches (51 cm) in diameter and 7 inches (17 cm) wide, was originally developed by B.F. Goodrich for the U.S. Air Force as aircraft wheel brakes, but is now manufactured in-house. Morpac has been using this device as a clutch and brake on reel stands successfully for decades, and has found that the 445 sq inches (2871 sq cm) of braking surface area provides exceptionally smooth conductor payout.

These features are common among many of Morpac's machines and are why many of its machines are still in use after more than 40 years of service. Morpac Industries has, in the decades it's been in business, branched out into other markets, but its core business and the bailiwick of founder has always been high-quality line-stringing equipment.