Western Area Power Administration Research Articles

Fault location using the distributed parameter transmission line model

Earlier work at Texas A&M University led to the development of transmission line fault location algorithms that were based on synchronized sampling of the voltage and current data from the two ends of the line. The line models used in the algorithms were based on lumped parameter models for electrically short lines, or lossless distributed parameter models for electrically long lines. In this paper, the lossless line model is modified to account for the series losses in the line. The line model equations are then solved in the time domain to accurately locate the fault. Testing of the modified algorithm is performed on a power system belonging to the Western Area Power Administration. Extensive EMTP based simulations are used to generate data that are supplied as inputs to the fault location algorithm. To make the testing as realistic as possible, detailed models of instrument transformers are used in the simulation of the various fault cases.

Operation of the unified power flow controller (UPFC) under practical constraints

The UPFC is the most versatile and complex power electronic equipment that has emerged for the control and optimization of power flow in electrical power transmission systems. It offers major potential advantages for the static and dynamic operation of transmission lines, but it brings with it major design challenges, both in the power electronics and from the perspective of the power system. As the UPFC transitions from concept to full-scale power system implementation, the control and protection of this sophisticated equipment are of primary concern. This paper describes the basic control, sequencing and protection philosophies that govern the operation of the UPFC, subject to the practical constraints encountered in an actual high power installation. The operation of the UPFC is illustrated with representative results from a TNA study, undertaken jointly by the Electric Power Research Institute (EPRI), Western Area Power Administration (WAPA) and Westinghouse Science and Technology Center (STC).

INDEXED SEQUENTIAL HYDROLOGIC MODELING FOR HYDROPOWER CAPACITY ESTIMATION1

ABSTRACT: The indexed sequential hydrologic modeling (ISM) methodology is utilized by the Western Area Power Administration as the basis for risk‐based estimation of project‐dependable hydropower capacity for several federally owned/operated projects. ISM is a technique based on synthetic generation of a series of overlapping short‐term inflow sequences obtained directly from the historical record. The validity of ISM is assessed through application to the complex multireservoir hydropower system of the Colorado River basin for providing risk estimates associated with determination of reliable hydrogeneration capacity. Performance of ISM is compared with results from stochastically generated streamflow input data to the Colorado River Simulation System (CRSS). Statistical analysis and comparison of results are based on monthly power capacity, energy generation, and downstream water deliveries. Results indicate that outputs generated from ISM synthetically generated sequences display an acceptable correspondence with those obtained from stochastically generated hydrologic data for the Colorado River Basin.

Consensus-Building for Integrated Resources Planning

Recently, integrated resources planning (IRP) has begun to be used in evaluating water supply options for large populations experiencing water scarcity. Traditionally employed to make decisions in the energy sector about different energy mixes, integrated resources planning is a technical methodology for forecasting needs, delineating alternative supply options, and choosing among different supply combinations (Goodman and Edwards, 1992; Western Area Power Administration, 1994). When used in water planning, the IRP approach lacks an important component seldom required in energy planning: processes for building a political consensus among water managers, producers, and consumers. The need for consensus-building processes in resources management generally is growing. Agencies at all governmental levels are beginning to manage resources collectively rather than individually so that ecosystems can be protected as a whole (Cortner and Moote, 1994). This shift to ecosystems management requires collaboration between many decision makers (Grumbine, 1994; Slocombe, 1993). In this article, we describe an IRP consensus process used by the Metropolitan Water District (referred to as Metropolitan or MWD) of Southern California. Metropolitan offers many lessons because it is dealing with a wide array of water issues. In terms of population served, MWD is the largest water management district in the world, and its decision makers represent areas that are diverse geographically and politically. The district invests in local water resource development as well as securing imported water, and its programs include not only supply but also conservation, reclamation, and storage. The Politics of Water Integrated resources planning needs a consensus-building component because water is typically a much more controversial issue than energy. In the latter, decisions about supply combinations are seldom made by the energy producers themselves. Rather, decision makers are usually in a position of selecting from among several types of energy resources (petroleum, hydro-electric, etc.) from several producers. In this situation, it is fairly straightforward to determine the most cost-effective resource mix. Admittedly, questions about reliability and other factors still require nontechnical, political judgments, but these judgments are not directly linked to the decision-makers' self-interest. In contrast, water production and water consumption are usually bound together geographically, economically, and politically. In any given region for which a group of decision makers is providing water, choices about water sources will have differential effects for different parts of the region and different political jurisdictions, depending on their existing water resources.(1) Consequently, consideration must be given not merely to technical questions of cost but also to equity across the region. Certainly, this was the case with MWD. Metropolitan is an umbrella agency covering southern California from Los Angeles to San Diego, a region that includes over 15 million people, 145 cities, and 94 unincorporated communities. The annual water needs of the region are roughly 4 million acre-feet. Sources of water include investment in local ground water, surface water and reuse of waste water, and importation of water from the Colorado River, northern California, and Owens Valley and Mono Basin. Metropolitan was formed in 1928 to provide imported water to meet the needs of cities, counties, districts, and other water suppliers serving consumers with retail or wholesale water. Twenty-seven pre-existing suppliers (cities, counties, and special districts), each covering a different geographical area and having a different mix of water resources, came together to establish MWD under state enabling legislation (Metropolitan Water District Act, 1969, chap. 209). Within Metropolitan's governance structure, these water suppliers are called Member Agencies. …

Design, implementation and validation of a real-time digital simulator for protection relay testing

This paper presents implementation details describing a new design of a real-time digital simulator for relay testing. The simulator is developed under requirements to utilize, as much as possible, low cost commercial computer hardware and system software support. The other requirements ask for a three-terminal support with extensive graphical user interface (GUI) and a simulation time step as low as 50 /spl mu/s. Such a design has been built for Western Area Power Administration (WAPA), USA, and fully validated using a model of an actual WAPA power system section. The simulator was delivered to WAPA in March 1994.

Real-time digital simulator for protective relay testing

The Western Area Power Administration (WAPA) recognized that real-time testing of protection relays is needed for a full evaluation of different relaying products considered for future use on the WAPA system. In terms of protective relaying, some important sections of the WAPA system have introduced several real challenges in deciding which relaying product will best suit the given application. The relaying applications are quite complex, consisting of parallel lines with series capacitor compensation, MOV protection on the capacitors, and a single-pole reclosing scheme. The authors describe how WAPA implemented a new low-cost, high-performance digital simulator design aimed at providing real-time operation while preserving accuracy and flexibility. >

Managing Lower Colorado River

The lower Colorado River system, which is managed by the Bureau of Reclamation (BuRec), comprises three major dams (Hoover, Davis, and Parker). There is a significant hydroelectric capacity in the southwestern system, but to make optimum use of the resource, it must be integrated with available thermal and nuclear sources. The major competing demands on the system are water supply, flood control, and energy production. BuRec and the Western Area Power Administration have undertaken an effort to explore alternative management strategies for the three dams. A model that incorporates a hierarchy of objectives as well as physical, institutional, and political constraints imposed on the system has been developed. It may be used to provide guidance to support the managers of the system in real time as they make hourly operating decisions over the next week. The model may also be used to explore alternative operating strategies for the lower Colorado. The process of formulating, developing, and implementing the model has affected the evolution of improved operations for the lower Colorado.

Experiences with parallel EHV phase shifting transformers

Phase shifting transformers (PSTs) are used to control unscheduled power flow in interconnected power systems. The authors discuss the application, protection, commissioning, and initial operating history of two sets of parallel, 300 MVA, 345 kV PSTs. The four Western Area Power Administration (WAPA) PSTs were energized in 1989 and are located in northwestern New Mexico in Shiprock and Waterflow substations. The installations are unique because two PSTs, using a series no-load and load tap changer (LTC) design, are operated in parallel at each location. A fault in the main LTC compartment later removed one unit from service, but the installation of parallel units at each location allowed for continued operation and control of the power flow on the two lines. >

Stochastic Analysis of Dependable Hydropower Capacity

Indexed sequential modeling (ISM) has been proposed by the Western Area Power Administration as an alternative approach to developing firm marketable capacity, i.e., project-dependable hydropower capacity (PDC) in contrast with the usual approach of basing PDC on the most adverse period of record. ISM allows a probabilistic analysis of hydropower capacity by extracting a series of overlapping short-term (say, 10 year) inflow sequences directly from the historical record, which includes the most adverse period, and then simulating reservoir operations over this interval for each sequence. As a means of evaluating ISM, the New Melones Reservoir system in the federal Central Valley Project of California was selected as a case study for comparing hydropower output generated from ISM input with use of a multivariate stochastic inflow generation model. A comparison of monthly power and energy output at 95% confidence limits, 10% risk level, and most adverse, showed reasonably good correspondence between the two methods, except for a few months of energy production in the final year of simulation.

Interactive Simulation of Water Resource Systems

Interactive computer simulation is presented as an off‐line decision support tool for training operators of complex water resource systems to define effective operational policy. The ability of the operator or analyst to interact with a system model throughout the simulation process is documented, along with the potential for including intangible aspects of system operation directly into the analysis. Interactive simulators are currently being used by the Western Area Power Administration for training system operation personnel. A case study is also reviewed in which operational guidelines were developed for a three‐reservoir system involving various physical, economic, and legal constraints.

Computer Models in Lower Colorado River Operations

The Lower Colorado Region, U.S. Bureau of Reclamation (Reclamation), is responsible for maintaining and operating Hoover, Davis, and Parker Dams, and the appurtenant reservoirs and powerplants. Operation of this dam and reservoir system is governed by a complex body of congressional acts, a Supreme Court decree, an international treaty, and interstate agreements that have come to be known as the “Law of the River.” Reclamation uses three computer models for decision support purposes ranging from scheduling hourly release rates to planning future monthly and seasonal operations. A computer model called the “24‐month study” is used for planning monthly and seasonal operation of the reservoir and powerplant system. Another model is used to plan and schedule releases for downstream water delivery, energy generation, and flood control requirements on a daily and weekly basis. Finally, Reclamation water schedulers use the Supervisory Control and Data Acquisition (SCADA) computer model of the Western Area Power Administration to automatically control hourly releases for the next 24‐hr day and for same‐day changes at Davis and Parker powerplants.

Medicine Bow Wind Project

The Bureau of Reclamation (Bureau) conducted studies for a wind turbine field of 100 MW at a site near Medicine Bow, Wyoming, one of the windiest areas in the United States. The wind turbine system would be electrically interconnected to the existing Federal power grid through the substation at Medicine Bow. Power output from the wind turbines would thus be integrated with the existing hydroelectric system, which serves as the energy storage system. An analysis based on “willingness to pay” was developed. Based on information from the Department of Energy’s Western Area Power Administration (Western), it was assumed that 90 mills per kWh would represent the “willingness to pay” for onpeak power, and 45 mills per kWh for offpeak power. The report concludes that a 100-MW wind field at Medicine Bow has economic and financial feasibility. The Bureau’s construction of the Medicine Bow wind field could demonstrate to the industry the feasibility of wind energy.