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Back in the Dust Bowl days of the 1930s, the Oklahoma state legislature created the Grand River Dam Authority, which built and operates three hydroelectric facilities and two lakes along the river’s system in northeastern Oklahoma.
These facilities, along with a thermal-generation facility, have a total generation capacity of 1,480 MW. The Authority, known by its acronym GRDA, transmits and delivers wholesale electricity across a 24-county service territory.
GRDA’s hydro generation includes the six unit, 125 MW Pensacola Dam, the four unit, 114 MW Robert S. Kerr Dam and the Salina Pumped Storage Project along the Saline Creek arm of Lake Hudson, which feeds into the overall GRDA system.
The Salina Pumped Storage Project (and W.R. Holway Reservoir) was built in two stages. The first stage, consisting of three units, was completed in 1968. The second stage, consisting of three units, was completed in 1971.
In the mid 1960s, GRDA realized more power sources would be needed. Customer demand soon outdistanced the power capabilities of the Authority’s newest hydro facility (Robert S. Kerr Dam and Lake Hudson, which were completed in 1964). Unfortunately, all acceptable dam sites on the Grand River had been used.
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Figure 1. The Salina Pumped Storage Project was left high and dry by drought in Oklahoma in late 2005, keeping its 260 MW of generating capacity from serving the needs of wholesale power customers of the Grand River Dam Authority.
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A pumped-storage project was presented as a solution to GRDA’s future energy needs. Pumped-storage plants had been established in Europe, but at the time only two had been built in the U.S, although many utilities were seriously considering this type of plant. Opponents and critics claimed the facility was experimental and would “break” GRDA. Despite these charges, the decision was made to build the facility.
Stage 1 included an earth and rock fill dam 185 feet high built in the Chimney Rock Hollow creating the reservoir. An 1,850-foot canal lined with six-inch thick reinforced concrete stretched to a 336’ x 60’ forebay structure with openings for steel penstocks, or pipe, 14 feet in diameter. Three penstocks stretched from the forebay to the powerhouse which housed three 64,000 horsepower (hp) reversible pump-turbine generators with a total capacity of 130 MW.
Stage 2 specified rock excavation for three more penstocks and installation of three more pump-turbine generators. This stage doubled the plant’s capacity.
The six units combine for a power capacity of 260 MW. As pumps, the units have 64,000 hp capacity. As generators, each has a 48,000 KVA rating. The pump-turbine rotating speed is 171.4 rpm. The vertical lift to the reservoir is 251 feet and the units’ present pumping capacity is 5,400,000 gallons a minute.
The six hydroelectric pump-turbine units in the Salina powerhouse were constructed by Westinghouse.
Power from Salina is typically dispatched as peaking power, because of the ability to bring the units online relatively quickly. Like GRDA’s other hydroelectric facilities, the Salina units can be remotely operated from the GRDA Energy Control Center, atop Robert S. Kerr Dam. When the reservoir has to be filled, GRDA typically pumps at night, when the cost of power is low (pumping uses about twice as much electricity as generation that the unit will produce). So, the units pump at night and operate as turbines during the day, as needed.
GRDA began draining the W.R. Holway Reservoir in October 2005, to allow for an inspection of the canal area by the Federal Energy Regulatory Commission (FERC) and to allow for some repairs. The water drained into Lake Hudson about the same time that drought conditions were really beginning to take hold across Oklahoma. Work on the project was completed in January 2006. However, because of the drought, and the low water in Lake Hudson, GRDA was unable to pump water back into the reservoir. With drought conditions subsiding and the lake returning to normal levels, pumping was expected to start in late April 2006. Once the reservoir is full (which could take close to a month), GRDA will be able to operate the facility again, likely beginning in early summer 2006. It has simply been off-line from October through the present, and GRDA has been unable to dispatch any power from there during that time.
The main powerhouse project was replacement of some 35 to 40 year old header pipe in the powerhouse basement. As part of the process, the canal had to be drained for an inspection and necessary repairs. GRDA had to install new riprap (25,000 tons of riprap over a 2,800-foot-long area) on the upstream side of the earthen dam. GRDA’s hydro mechanics worked on the facility’s intake structure, repairing and reinforcing trash racks that were in need of repairs. This included sandblasting, epoxy coating and reinforcing with new steel.
Power Engineering May, 2006
Author(s) :
David Wagman
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