The Shoshone Transmission Line was an early and notable

electric power transmission Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This i ...

line, now recorded on the

List of IEEE Milestones The following timeline tables list the discoveries and inventions in the history of electrical and electronic engineering. History of discoveries timeline History of associated inventions timeline List of IEEE Milestones The following l ...

. The line takes its name from the power plant at its west end which generates

hydroelectric power Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined a ...

below the Shoshone Rapids in Glenwood Canyon.Florence Clark, Light and Power for a State
Popular Electricity
Vol. IV, No. 6 (Oct. 1911); pages 481-485, see page 483, right column, for a discussion of the role of the Boulder power plant. The line began service on July 17, 1909, conveying power from the 15 MW

Shoshone Generating Station The Shoshone Generating Station is a hydroelectric power plant on the Colorado River east of Glenwood Springs, Colorado. In addition to its power output, the water rights the plant uses are among the oldest on the Colorado River, and play a major ...

, outside of

Glenwood Springs Glenwood Springs is a home rule municipality that is the county seat of Garfield County, Colorado, United States. The city population was 9,963 at the 2020 United States Census. Glenwood Springs is located at the confluence of the Roaring Fork ...

Denver Denver () is a consolidated city and county, the capital, and most populous city of the U.S. state of Colorado. Its population was 715,522 at the 2020 census, a 19.22% increase since 2010. It is the 19th-most populous city in the United ...

, serving substations in Leadville, Dillon and Idaho Springs. At the east end of the line, it was connected to the utility's Boulder Canyon Hydroelectric Plant powered from the

Barker Meadow Reservoir Barker Reservoir is a water supply reservoir in the Colorado Front Range located near the town of Nederland, Colorado in southwestern Boulder County. Barker Dam provides water to a downstream hydroelectric power generating facility, and its r ...

. In the event of a break in the line, either power plant could supply customers along the line. As originally built, the line was long, crossing the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, no ...

at Hagerman Pass (at altitude ), Fremont Pass (at altitude ) and Argentine Pass (at altitude ). For many years, this was the highest electric power transmission line in the world.Public Service Company of Colorado -- Providing Energy for More than a Century
(undated, but content implies 1976, the

United States Bicentennial The United States Bicentennial was a series of celebrations and observances during the mid-1970s that paid tribute to historical events leading up to the creation of the United States of America as an independent republic. It was a central event ...

); pages 12-13. The

three-phase Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, transmission, and distribution. It is a type of polyphase system employing three wires (or four including an optional neutral r ...

line operated at 90 kV and was supported 1400 steel towers high on an average spacing of . A secondary power line from the backbone of the Shoshone line connected it to a steam generating station at Leadville, as well as to many of the mines in the Leadville region. At Dillon, a secondary line served the numerous gold dredges of the Breckenridge

placer mining Placer mining () is the mining of stream bed ( alluvial) deposits for minerals. This may be done by open-pit (also called open-cast mining) or by various surface excavating equipment or tunneling equipment. Placer mining is frequently used for ...

district. Connections were also made to smaller hydroelectric plants at Dillon and Idaho Springs. In 1951 and 1952, the Public Service Company of Colorado replaced the hemp-cored 6-strand copper cable on the Shoshone line with steel-core aluminum cable. By this time, the Shoshone generating station had been upgraded to 14.4 MW. New towers were installed in the 1970s, with some changes in the path of the line.Sara E. Simonson, Scott Toepfer, et al
Rapid Assessment of a Large-Magnitude Snow Avalanche Event in Colorado
Researchgate.net, Oct. 6, 2014. The severe climate and mountain terrain along the line are a challenge. Within a few years of construction, sleet buildups of as much a had been observed on wires along the line. Several towers were buckled and demolished by wind force alone—wind speeds of over were measured at one point along the line, leading to

metal fatigue In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts o ...

at the points where insulators support the power line. In the vicinity of the high passes, snow depths as great as have been measured.

Avalanche An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and ear ...

s along the line have been known to damage multiple

transmission tower A transmission tower, also known as an electricity pylon or simply a pylon in British English and as a hydro tower in Canadian English, is a tall structure, usually a steel lattice tower, used to support an overhead power line. In electrical ...

s in remote locations. The

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...

has honored the line for its length, and for deployment in difficult terrain and unusually harsh weather patterns.IEEE History Center
/ref>

References

{{reflist Electric power transmission systems in the United States