Coal, Hydroelectric

Grand Coulee Dam’s Third Power Plant Undergoes Refurbishment

Issue 10 and Volume 117.

Grand Coulee Dam is the largest hydropower project in North America with a capacity of 6,809 MW.
Grand Coulee Dam is the largest hydropower project in North America with a capacity of 6,809 MW.

The Bureau of Reclamation Commences Major Rehab of Hydropower Project

By Eric Marks, PricewaterhouseCoopers

Grand Coulee Dam on the Columbia River in the state of Washington produces hydroelectric power and provides irrigation. The Dam is immense. To put it in perspective, it was built with enough concrete to build a four lane highway stretching from Los Angeles to New York (over 3,000 miles long).

The U.S. Department of the Interior’s Bureau of Reclamation (BOR) is currently in the midst of a sizable refurbishment project that will take years to complete because of its size and importance as the Reclamation’s Columbia Basin Project in central Washington. It is not only providing flood control, irrigation, recreation, stream flows, and fish and wildlife benefits, its total hydropower production capacity is 6,809 megawatts and supplies an average annual energy output of some 2,300 megawatts, which is enough power to continuously supply Seattle and Boston.

The Grand Coulee Landscape

The dam’s infrastructure comprises three power plants, a pump-generating plant, and three switchyards. There is a power plant on both the left and right sides of the spillway on the downstream face of the dam. There is pumping generation plant on the left abutment of the dam, an 11.95/115-kilovolt switchyard, a 230-kilovolt consolidated switchyard, and a 525-kilovolt Third Power Plant cable-spreading yard and switchyard are located high on the hills west of Grand Coulee Dam. Today much of the reclamation’s focus is on the Third Power Plant because the refurbishment project that is underway has begun with this plant located on the downstream face of the fore bay dam.

The first powerhouse comprises three station service generators rated at 10,000 kW and nine generators rated at 125,000 kW. The second houses nine generators rated at 125,000 kW. The Third Power Plant, which is getting all the attention as the refurbishment project kicks off, comprises six generators (three generators nameplate rated at 600,000 kW but able to operate up to 690,000 kW, and three generators rated at 805,000 kW). The pump-generating plant contains six pump-generators. Individual penstocks supply each of the generators. The Third Power plant has the largest penstock that is approximately 40 feet in diameter and carrying up to 35,000 cubic feet per second of water. One switchyard has 11.95 kilovolt distribution and four 115 kilovolt transmission lines; one switchyard has 230 kilovolt generation (from eighteen 125,000 kW units) and eleven transmission lines; the third switchyard has 525 kilovolt generation and six transmission lines. There are electrical connections through transformers between the 115 and 230 kilovolt switchyards and the 230 and 525 kilovolt switchyards. The main dam contains 11 drum gates, each 135 feet long and 40 outlet tubes with 102-inch ring seal gates for spilling water. The dam complex’s three switchyards transmit electricity into the regional power grid.

Using Advanced Materials, Automation and Technology

The Grand Coulee Dam is the largest hydropower plant in North America. The Bureau of Reclamation’s engineers prudently monitor and control any power supplied to the grid to ensure it is safe and fault tolerant from any possible power anomalies (spikes or dropouts). The current retrofit of the control system for the BOR is in cooperation with the Bonneville Power Administration (BPA), the U.S. Army Corps of Engineers Hydroelectric Design Center (HDC), the project’s system integrator, and RTI Data Distribution Service to ensure a SCADA solution is deployed to be able to remotely monitor and control power operations.

Data acquisition is being conducted with the monitoring of some 40,000 I/O points. The SCADA monitors and controls 30 generators and the transmission switchyard. RTI’s SCADA will communicate with about 55 Linux-based Programmable Logic Controllers (PLCs) on the central control network. Operators will monitor via a Windows-based Human-Machine Interface (HMI) that will display data from other various databases and redundant servers. Based on standard, commercial computing hardware, the system is robust and secure. The plan is to use this same SCADA configuration for twelve dams in total with the Federal Columbia River Power System.

Trelleborg Sealing Solutions is the supplier of hydro bearing material called Orkot TXMM to be used in multiple applications such as the control gate link bushings, operating rings and wicket gate bushings. Progress has already started with three of Grand Coulee’s Third Power Plant units. The Orkot material was selected for its advanced synthetic polymer alloy, which requires a unique manufacturing process to make in order to deliver the high concentration of PTFE in the sliding area while maintaining substantial compressive strength.

Since the PTFE layer is several millimeters thick, it makes the material highly tolerant and won’t wear out. The Orkot also maintains its low friction properties throughout the service life of the bearing, which is another key factor for a project of this size and requirement for advanced, long lasting materials.

The Grand Coulee’s Third Power Plant is in process of being refurbished and the advanced Orkot TXMM Hydro was chosen for this retrofit project especially for its dry running capabilities and tolerance to edge loading and misalignment even with the heaviest loads.

The hydro bearings are well suited to freeze fitting without the danger of shattering, which is a key factor for dam conditions.

In addition, materials to be used in this refurbishment have to not only deliver the highest wear resistance possible but also be dimensionally stable and not swell in water. Trelleborg’s materials were credited through lots of testing by Powertech Labs and received approval by the US Army Corps of Engineers, which further established confidence in the use of Orkot hydro bearings.

Back to the Source: Hydropower

Hydropower makes up almost 80 percent of Grand Coulee’s authorized purposes. However irrigation and flood control make up the additional 20 percent. It is of interest to note that the public’s desire for irrigation was a key driving force behind the dam’s construction.

Having already invested several years in planning for this refurbishment project, all eyes are on the Third Power Plant of the 6,809-MW Grand Coulee project.

The Rehabilitation will start with the retrofit of all six generators, of which three will be uprated. The BOR wants to ensure continued reliable operation of this gravity dam, especially since it is the largest hydroelectric facility in the US.

The state has proclaimed that the 6,809-MW Grand Coulee project on the Columbia River in Washington is a critical component for power generation in the region. The Third Power Plant, which began operating in 1975, has six units that need substantial rehabilitation simply because they have become antiquated.

The Bureau of Reclamation, the plant owner and operator, has set high expectations and have followed through with years of careful planning for this rehab.

This past March, the overhaul on three of the six units has started and is not expected to be completed until September 2017.

The Reclamation will then access the three completed units and work on the remaining three units is then expected to start in January 2018 and will not be finished until December 2022.

The expectation that was set in using state of the art materials and in leveraging the newest in technology advancements whether for polymers, remote monitoring and data acquisition, power generation equipment, etc. to ensure the plant will operate reliably, efficiently and safely for at least another 40 years.

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