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Golden, CO, United States

Xcel Energy Inc. is a utility holding company based in Minneapolis, Minnesota, serving more than 3.3 million electric customers and 1.8 million natural gas customers. It consists of four subsidiaries: Northern States Power-Minnesota, Northern States Power-Wisconsin, Public Service Company of Colorado, and Southwestern Public Service Co.. Benjamin G.S. Fowke III is the Chairman, CEO, and President. Wikipedia.

Gurgur C.Z.,Indiana University | Jones M.,Xcel Energy Inc.
Renewable Energy | Year: 2010

The common practice to calculate wind generation capacity values relies more on heuristic approximations than true system estimations. In this paper we proposed a more accurate method. In the first part of our analysis, a Monte Carlo simulation was created based on Markov chains to provide an independent estimate of the true behavior of wind farm capacity value as a function of system penetration. With this curve as a baseline, a technique for using beta distributions to model the input variables was adopted. A final step to increase accuracy involved the use of numerical convolution within the program to eliminate summation estimates. © 2010 Elsevier Ltd.

McBee K.D.,Tesla Power Engineers , LLC | McBee K.D.,Xcel Energy Inc. | Simoes M.G.,Colorado School of Mines
IEEE Transactions on Smart Grid | Year: 2014

Smart grid technology has enhanced the ability to monitor numerous aspects of the distribution system for improving system performance and reducing system losses. One benefit is the continuous assessment of insulation degradation within distribution transformers, which is commonly referred to as a loss of life assessment. Calculating the expended life of a transformer consists of determining its winding hotspot temperature, which fluctuates with customer demand, ambient temperature, and cooling characteristics. Most residential transformers in service today do not possess the ability to connect to a smart grid communication system for continuous monitoring; therefore, they rely upon fusing for protection against extreme loading conditions. Smart meters can provide utility companies with the information required to identify distribution transformers that are experiencing higher than rated losses that can ultimately reduce their expected life. The research presented in this paper defines the smart meter functions required to accurately assess the aging of distribution transformers according to IEEE Std C57.91 and C57.110. To establish general accuracy guidelines, transformer loading indices were developed to evaluate acute excessive loading, long-term excessive loading, and excessive loading due to harmonics. Metering functions evaluated included power factor, harmonic demand, and ambient temperature. © 2014 IEEE.

Novosel D.,Quanta | Bartok G.,RLC Engineering | Henneberg G.,NV Energy | Mysore P.,Xcel Energy Inc. | And 2 more authors.
IEEE Transactions on Power Delivery | Year: 2010

This paper is a summary of the IEEE Power System Relaying Committee report. It describes the performance of protective relays during wide-area stressed power system conditions. First, the behavior of protection functions during dynamic operating conditions is described. Then, the lessons learned from studying recent wide area disturbances, as well as the operational history of protection performance during stressed system conditions, are analyzed. Finally, methods of implementing protective relay functions to prevent further propagation of system-wide disturbances are presented. © 2009 IEEE.

Himelic J.B.,Xcel Energy Inc. | Kreith F.,University of Colorado at Boulder
Journal of Energy Resources Technology, Transactions of the ASME | Year: 2011

Plug-in hybrid electric vehicles (PHEVs) have the potential of substantially reducing petroleum consumption and vehicular CO 2 emissions relative to conventional vehicles. The analysis presented in this article first ascertains the cost-effectiveness of PHEVs from the perspective of the consumer. Then, the potential effects of PHEVs to an electric utility are evaluated by analyzing a simplified hypothetical example. When evaluating the cost-effectiveness of a PHEV, the additional required premium is an important financial parameter to the consumer. An acceptable amount for the additional upfront costs will depend on the future costs of gasoline and the on-board battery pack. The need to replace the on-board battery pack during the assumed vehicle lifetime also affects the allowed premium. A simplified unit commitment and dispatch model was used to determine the costs of energy and the CO 2 emissions associated with PHEVs for different charging scenarios. The results show that electricity can be used to charge PHEVs during off-peak hours without an increase in peak demand. In addition, the combined CO 2 emissions from the vehicles and the electric generation facilities will be reduced, regardless of the charging strategy. © 2011 American Society of Mechanical Engineers.

Howell A.G.,Xcel Energy Inc.
American Society of Mechanical Engineers, Power Division (Publication) POWER | Year: 2014

Combined cycle power plants fueled with natural gas have been increasingly preferred by regulatory agencies for new power generation projects, compared with traditional coal-fired plants. With growing concerns about water resource availability and the environmental impact of wet cooling systems, there has been an increasing trend for new combined cycle projects to incorporate dry cooling, often as a mandate for regulatory approval of the project. There appears to be little consideration given to the impact of less efficient dry cooling systems on unit efficiency, and particularly on increased fuel requirements and therefore carbon dioxide (CO2) emissions for a given power generating output. The trade-off between reduction of water use and increased fuel requirements with dry cooling should be included as part of the decision on the selection of cooling systems for new fossil plant construction. Copyright © 2014 by ASME.

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