About 32 POWER-GEN International attendees took a special hard hat tour of the Hoover Dam power plant on Dec. 11. The hydroelectric plant that straddles the states of Nevada and Arizona has a rated capacity of 2,078 MW, but because Lake Mead is about 90 ft. below normal levels, the plant is running at about 70 to 80 percent. It is operated by the Bureau of Reclamation under the U.S. Department of the Interior.
The plant uses 17 Francis generators, with eight on the Nevada side and nine on the Arizona side of the dam, that produce up to 4.5 billion kWh of electricity per year. The generators were installed between 1936 and 1961. The original turbines were replaced during an uprate project between 1986 and 1993.
The power is distributed through long-term power contracts to the Arizona Power Authority in Arizona; the Colorado River Commission and Boulder City, both in Nevada; and the Metropolitan Water District of Southern California, Southern California Edison and ten cities in California.
Each generator has an intake tower that feeds water to it, and a governor on the generators controls the water flow. Penstocks also help feed water to the turbines and wicket gates control the flow of water.
Major repairs happen every 20 years, and there are two cranes on site that can move up to 150 tons. Since the rotor itself weighs more than 300 tons, it takes both cranes to lift them when it is time for repairs. There is also a machine shop on site so workers can do their own repairs, and the dam also hosts an apprenticeship program to help train workers.
The plant also uses diversion tunnels to move water from Lake Mead through the power plant that then empties into the Colorado River.
The dam also produces its own internal electricity using four, 2.4 MW station service units using Pelton water wheels on site. It can withstand an earthquake up to a magnitude 8.6 and it is an arch-gravity dam, so it in not attached to the canyon wall, but wedged in instead and thins toward the top.
Fun fact: More than 115 movies have been filmed at Hoover Dam.