- Bureau of Reclamation's Power Uprating Program
- Summary of Reclamation's Uprating Program to Date
- History of Reclamation's Uprating Program
- Uprate Criteria
- Environmental Considerations
- Present Status of the Power Uprating Program
- Turbine Uprates
- Program Funding
- Uprating Costs
- Problems Encountered
- Future Activities of the Power Uprating Program
Bureau of Reclamation's Power Uprating Program
Reclamation is at the center of the hydropower industry, examining ways to improve hydropower efficiency and use in operating dams and powerplants across the western United States. Uprating hydroelectric generator and turbine units at existing powerplants is one of the most immediate, cost effective, and environmentally acceptable means for developing additional electrical power.
Summary of Reclamation's Power Uprating Program to Date
Reclamation Power Uprating Program
The following tabulation summarizes the accomplishments of the Bureau of Reclamation's Power Uprating Program through July 2000.
Completed Uprates Generator units uprated 58 Added kW 1,782,823 kW Average uprated unit percent increase in capacity 48.1 % Percent of Reclamation total capacity 12 % Existing uprate contracts Generator units under contract 0 Additional capacity 0 kW Total Power Uprating Program to Date Total additional kW 1,782,823 kW Actual contract cost from 1978 to 1995 $112,035,070 Average actual cost per kilowatt from 1978 to 1995 $69 Planned Uprates Total sites 1 Total units 3 Projected capacity increase in kilowatts Boise River Diversion Undetermined Projected dates Undetermined
History of Reclamation's Uprating Program
Following the 1973 oil embargo, a review was made of Reclamation's powerplants to determine if they could be uprated to a higher capacity and to produce more energy. Uprating existing hydroelectric powerplants to fully utilize the available water resource for additional energy and peaking capacity was recognized as one of the better long range additions that could be made to help solve the energy problem. In 1978, the Bureau of Reclamation and the Department of the Interior established, as one of their major program goals, the investigating and implementing of all viable opportunities to improve existing plants by modernizing and uprating the generating equipment. The Western Energy Expansion Study, issued, in 1977, identified several proposals for uprating existing Reclamation hydroelectric units and concluded that uprating of existing units is the most immediate, cost effective, and acceptable means contributing to meeting the Nation's electric capacity and energy needs.
A government Accounting Office study entitled "Power Production at Federal Dams Could Be Increased By Modernizing Turbines and Generators," recommended that Reclamation evaluate opportunities to improve hydropower production and act on those that are economically justified.
|As the average age of Reclamation generator units (Figure 1) was greater than 30 years, many generators were candidates for rewinding and/or uprating.|
Since 1978, beginning with two Shasta Powerplant units, Reclamation initiated a power uprating program to increase the capacity of Reclamation facilities as funding and unit availability allowed. In addition, there have been a number of generator rewinds where no appreciable uprate potential existed but winding condition was poor.
|Figure 2 shows the existing age of Reclamation generator windings.|
Some confusion has existed over the terms rewind and uprating when applied to generators. Reclamation's definitions for rewinds and uprates are as follows:
Rewinds - Many of our older generators were purchased with a continuous overload capability of 15 percent above rated output. Generally, when we "rewind" a generator, we purchase the new winding with a base rating equal to the 115 percent machine level and at the appropriate allowable temperature rise consistent with the insulation class of the new winding. Although the new winding may be capable of operation at higher levels, the machine is still limited to operation at the 115 percent level because the mechanical characteristics of the generator have not been confirmed to be capable of higher loads. Ratings of the bus, transformer, etc. are examined; but a detailed study is not performed.
Uprates - An uprate normally involves an increase in rating of more than 15 percent, which in turn necessitates a review of the capability and limits of all of the power equipment, from the penstock through the turbine, generator, bus, switchgear, transformer, and transmission system. These systems can then either be retained, modified or replaced in order to obtain the optimum uprate level.
A good indicator for considering uprating a generator is when the turbine capability substantially exceeds the generator capability at normal operating heads. Most Reclamation turbines are designed to provide rated output (or nameplate capacity) at rated head. Since the rated head was chosen far enough below the maximum operating head to ensure the generator overload capacity could be utilized, reservoirs often operate at heads much higher than rated and the turbine is usually capable of more mechanical output than the generator can convert to electrical energy. In other situations, increased rating and efficiency can be obtained by runner replacement. For pre-1960 turbines, it is frequently possible to obtain output increases as high as 30 percent and efficiency increases of 1 percent by replacing existing runners with runners of improved design.
The generator power rating was decided based on several constraints including historical river flows and allowable variations in reservoir levels. Sometimes authorizing legislation included allowable limits on generator size. The former requirement that generators deliver rated output with no more than a 60 degree C temperature rise and the conservative safety factors provided by early generator manufacturers result in the possibility of substantial increases in machine capacity by installing windings using modern insulation technology which can provide increased electrical capacity with the same physical size as earlier manufactured windings. Therefore, it is often possible to increase the capacity of older units by installing new stator windings and improved runners, and by upgrading various auxiliary equipment.
Apart from technical limitations, the economic value of capacity is most important in justifying an uprate. Because many Reclamation projects develop the maximum energy available (without spillway operation) additional energy is not generated after an uprate. Uprate capacity is obtained at the expense of plant factor (more energy can be produced but for a lesser period of time). The practical limit of uprating is reached when the cost of replacing equipment to obtain additional capacity equals the economic worth of that added capacity.
If the turbine and hydraulic conditions are favorable, Reclamation's regional offices undertake an economic study to determine if there is a market for additional capacity and energy and also determine values for these increases. An engineering study of the plant analyzes the effect of uprating on all plant components. From this study various levels of uprate potential are determined. Many economic considerations are included such as lost revenue during outage time and increased power and energy rates to provide for equipment replacement. Regardless of the benefits available, many generator uprates are limited by the spending authorized.
Other considerations to be addressed when conducting a unit uprate study are:
- Water operations
- Power operations
- Environmental considerations
- Contractual obligations
- Coordination and scheduling of the generator outage
The power uprating program is subject to National Environmental Policy Act (NEPA) compliance. This compliance can take one of three forms:
- 1. A categorical exclusion (CE)
- 2. A Finding of No Significant Impact (FONSI)
- 3. An environmental impact statement (EIS)
Each proposed rewinding and/or uprating must be evaluated by the use of a categorical exclusion checklist to determine if it qualifies for the exclusion; if not, an environmental assessment (EA) is prepared and either a FONSI or EIS must be completed before the action is undertaken.
In cases where no change in operation occurs as a result of the actions, a CE will probably be appropriate. However, where flow modifications occur, the U.S. Fish and Wildlife Service and the state game and fish agency along with other interested agencies and organizations must be consulted and allowed to make recommendations on the proposed action. Such changes in flows could necessitate an EA the results of which could be a FONSI or an EIS (if changes result in significant effects).
Present Status of the Power Uprating Program
Under Reclamation's Power Uprating Program uprating studies have been performed on 58 Reclamation generators.
As of July 2000, generator uprates have been completed on 58 units resulting in an increase in Reclamation generator capacity of 1,782,823 kilowatts.
Three 500 kilowatt units at Boise River Diversion Powerplant (a) are the only units presently planned to be uprated in the future. No schedule is set for the uprating of these units. Table 1 (b) shows a summary of the results of the Power Uprating Program beginning in 1978 through the present. This program accounted for an average increase in capacity of the uprated units of 48.1 percent and represents 12 percent of Reclamation's total capacity. Table 2(c) shows the rated capacity and generation produced for all Reclamation powerplants in calendar year 1999. Reclamation's Power Facilities Map (d) shows the location of Reclamation powerplants. Figure 3 (e) shows the capacity added each year of Reclamation's Power Uprating Program, and Figure 4 (f) shows the generator units uprated per year for the same time period. Figure 5 (g) shows the kilowatts added per plant, and Figure 6 (h) shows the percent increase in capacity per plant for the power uprating program. Figure 7 (i) shows the uprating program capacity increase by Reclamation region.
|The turbines were replaced and uprated at three plants as shown in Table 3. The usual reasons for replacement were age or changing operating conditions for the reservoir. The table does not include cases where the replacement was in kind or where there was very little increase in output.|
- Bureau of Reclamation Power Uprating Program funding has been provided by both non-Federal and Federal funds.
- The majority of the individual plant uprates were supported by appropriated Federal funds.
- Other funding sources included Federal funding through one of the power marketing administrations, non-Federal funding in the form of the Hoover replacement fund, and up-front funding by the preference power customers.
- The money invested in the uprate program is completely reimbursed, with interest, through power revenues.
- From 1978 to 1995 total contract costs for the Power Uprating Program were
- The uprates performed after 1995 have been funded by the preference power customers.
|Table 4 shows the contract cost and cost per kilowatt increase for 21 Reclamation uprating contracts involving 14 powerplants and 55 generating units. The numbers are actual costs of the contracts and have not been normalized to a specific year or adjusted to reflect normal maintenance costs which would have been incurred had the upratings not been performed.|
Most uprated generators were in need of replacement windings as part of normal generator maintenance. If the cost of performing needed rewinds were subtracted from the uprating costs shown in Table 4, the actual cost per kilowatt increase for uprating would be considerably less than shown. As shown in Table 4, the average cost per kilowatt increase for the Power Uprating Program during the 1978 to 1995 time perion was $69 per kilowatt. This compared to an average cost in 1995 for providing new peaking capacity through oil-fired generator units of over $400 per kilowatt. In addition, operation, maintenance, replacement, and fuel costs are minimal for new hydropower peaking capacity when compared to oil-fired generators.
|Figure 8 (left) shows the contract cost for the upratings performed at each plant participating in the Power Uprating Program during the 1978 to 1995 time period. Figure 9 (right) shows the cost per kilowatt for the capacity additions at each plant participating in the Power Uprating Program during the 1978 to 1995 time period.|
The usual problems encountered involved scheduling. Machines were not available when expected, delays occurred in manufacturing, funding problems stretched out the work, and installations were more complex than expected. With the cooperation of all parties, these scheduling problems were worked through. Some of the more significant technical problems encountered were:
- Difficulty in passing the post-installation high potential tests occurred on one unit. In an attempt to cure the insulation, the stator was enclosed and current was circulated through the windings. The temperature was excessive and the core buckled.
- One winding design resulted in a bar/slot geometry that was incapable of dissipating the heat. The temperature was beyond operating limits and the core and winding had to be redesigned and remanufactured.
- At some of the Hoover units, the original manufacturer used a double spider and rim design. The uprate called for replacement of the rims. The original manufacturer's installation techniques distributed the pole weight between rims. On our reinstallation we did not use the same procedures and it caused some cracking of the rim support ledges. Additional support had to be designed and installed.
- One of the Shasta units was found to have a bad core. The contract had to be delayed while a replacement core was procured.
- On two units, noise and vibration indicated the winding layout was less than optimum. This was corrected by making some reconnections at the pole jumpers and circuit rings.
- The inclusion of static exciters and regulators with the uprated contracts resulted in mixed results. The intent was to have all the work done during one outage with a single responsible contractor. In practice, it was work outside the experience range of most installation crews and most machine manufacturers. The equipment and work was usually subcontracted and coordination was difficult. The checkouts, alignment, and interconnections to the existing plant controls became so difficult that Reclamation personnel eventually performed most of this work.
Future Activities of the Uprating Program
|Presently, three generating units (at one powerplant location) have been identified as candidates for uprating. These consist of 3 units at Boise River Diversion (a) presently rated 500 kilowatts each. The exact increase in capacity that can be gained through uprating the Boise River Diversion units will not be determined until thorough uprating studies are done on the units. Economic factors will also be a determining factor in arriving at the final uprated value. The work on the three units will essentially complete Reclamation's present uprating program. This program has accounted for an increase in Reclamation's generating capacity of almost 1,800,000 kilowatts and when combined with the approximately 15 percent increases in unit capacity from rewound but not uprated units has resulted in an increase of over 2,500,000 kilowatts through winding replacements and/or uprating. Figure 10(b) shows the accumulated capacity added by uprating and rewinding between 1962 and 2000 and Table 5(c) lists the capacity added by plant for uprated units. Table 6 (d) lists all rewind and uprate activity performed on Reclamation units. Approximately 30 percent of Reclamation's generators were determined viable for uprating. The remaining units were either modern design (post mid-1960's) or were not feasible for uprating due to economic or water supply restrictions. Hence, the majority of the generator rehabilitation work that can be foreseen will be rewinds or equipment modernization which may not result in increases in capacity. Several powerplants are so old and outdated that complete equipment replacement or a new facility would be required. In the future, new advances in technology - such as superconductivity - may make further generator uprates possible, much as advances in the insulation system used on generator windings in the 1960s made major capacity increases feasible and economically justifiable on many generators. Figures 11 (e) and 12 (f) show the status of the windings for all Reclamation units, and the percent of total capacity located in each region, respectively.|