Northern States Power Company Research Articles

An improved algorithm to aid in post-heat storm restoration

Utilities strive to have quick restoration after a power outage. Extreme conditions, such as storms, create difficult restoration challenges because of the large number of tasks necessary to restore power to many affected customers. Restoration efforts can be further hindered when outage report escalation algorithms predict the wrong location for affected devices. This paper describes a modified topological based algorithm that associates trouble calls with each other to provide more accurate information about outages during heat storms. The heat storm algorithm was tested and verified on two feeders using test cases that simulated the heat storm conditions experienced at Northern States Power Company in Minneapolis, Minnesota in July 1995.

Online dynamic security assessment in an EMS

System stability analysis results have been part of electric utilities' operating guidelines for move than a decade. Today, these guidelines are compiled from offline stability studies conducted jointly with other utilities and independently by each utility. The offline study results are adjusted for actual generation patterns and network conditions, based on sensitivity analysis, and presented to operators through the energy management system (EMS). These stability limits tend to be conservative for normal conditions and may indeed be inaccurate following unusual system events. The offline study scope expands each year as more significant variables are identified. Limits derived from the offline studies also require extensive engineering analysis trying to anticipate conditions which may never occur. A better alternative is to compute these limits online, based on actual operating conditions. A dynamic security assessment (DSA) function implemented in an EMS environment would improve reliability, identify additional energy transaction potential and result in better use of engineering resources. This article presents DSA functional features and an implementation of an online DSA function under development at Siemens Power Systems Control under a collaborative sponsorship of EPRI and Northern States Power Company.

Simulating transformer taps for remote cranking operations

This article describes an attempt at simulating a remote cranking operation for the black start of two coal-fired drum-type power generation units at Northern States Power Company, USA. The simulation system uses power flow and generator reactive capability programs in an iterative process to determine the appropriate tap positions for the combustion turbine (CT) unit and auxiliary transformers, the various transformers installed in the steam power plant path, and for controlling a proper voltage level for the generator system bus at the CT plant.

Unit commitment application builds up existing EMS

The unit commitment system (UCS), an integrated set of hardware and software components connected to Northern States Power Company's (NSP's) existing energy management system (EMS) via a hyperchannel network, is described. The objective of the UCS is to provide functional capabilities for the user to study and and economically schedule system resources (generation and transactions) in conjunction with the EMS system. The system design is described. It is based on the philosophy of using modularity and openness, wherever possible, giving the utility flexibility to evolve and expand the system cost-effectively as the requirements or hardware platforms change. The implemented software not only addresses NSP's present need, but also represents a product that fits the evolving open systems environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Lagoons and ponds

Lagoons and ponds

O'Leary confirmed as DOE secretary

On January 21, the U.S. Senate approved the nomination of Hazel R. O'Leary as the new secretary of energy. This vote came just 2 days after O'Leary appeared before the Senate Energy and Natural Resources Committee.O'Leary, 55, has been executive vice president for corporate affairs at the Minnesota‐based Northern States Power Company. During the Carter administration, she worked in a senior position at the Federal Energy Administration.

Erosion/corrosion data handling for reliable NDE

Ruptures in wet-steam and single-phase water lines at fossil and nuclear plants due to erosion/corrosion of of the inside surface have resulted in comprehensive measurement of wall thickness of components prone to failure. The large number of components to be inspected as well as the required resolution to make that inspection require effective management of the large amounts of ultrasonic testing data. Recognizing this need, Northern States Power (NSP) Company initiated compilation and organization of a database which contained inspection history, component type and history, flow conditions in the component along with detailed wall thickness measurements. The database was organized using a commercially available personal computer (PC)-based database management software package. This paper discusses the background of erosion/corrosion (E/C) damage at U.S. utilities; the industry response; NDE approaches to wall thinning examination; and practical techniques used to analyze wall thickness data from components and compare data between inspection intervals. The data were compiled from nuclear and fossil units.

An expert system for security trend analysis of a stability-limited power system

An expert system for dynamic security assessment (DSA) is described in which artificial intelligence techniques are applied to the transient energy function (TEF) method. The effect of contingencies on the security level and its rate of change with changing system conditions and parameters are computed using the results of the TEF sensitivity analysis program. The expert system determines the loading trend and analyzes the data obtained from TEF to compute the trend of the security index. The trend of the control parameters can then be adjusted to maintain the security index within a range of safe values. An example is given using data collected from the Northern States Power Company (NSP) where the expert system correctly computed the security index and suggested adjustments to system parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Authors

Authors

An Approach to Conservation and Load Management Economic Analysis

This paper discusses a technique used by Northern States Power Company (NSP) for the evaluation of conservation and load management alternatives. The technique involves examining the cumulative present worth of the avoided costs net of revenue effects due to proposed programs. The factors considered include annual revenue requirements for generation operation and maintenance, generation capacity, generation fuel inventory, transmission, distribution system, annual production cost, and revenue impact of the strategy being considered. The cumulative present worth of these factors when compared to base case alternatives yields an economic ``figure of merit'' for judging conservation and load management strategies.

Standardized SCADA-AGC System Effect on System Cost, Delivery and Quality

This paper describes a new Northern States Power Company SCADA-AGC system and the effects of being forced, by time and economic constraints to purchase highly standardized vendor hardware and software.

A Screening Model for Utility Strategic Planning

This paper describes an integrated set of computer models called The Screening System which is designed for utility strategic planning in Northern States Power Company. The Screening System consists of a Control System and five application models, viz., the Generation and Fuel Model (GAF), the Gas Supply and Cost Model (GSC), the Capital Expenditure and Recovery Model (CER), the Subsidiary and Acquisition Model (SAQ), and the Financial Impact and Reporting Model (FIR). This System is interactive and extremely fast to execute so that a large number of scenarios and alternatives can be evaluated quickly. Thus, it can be used to study many system planning and financial planning issues in order to select a limited number of alternatives for more accurate comparisons using detailed models. The experience of Northern States Power Company with the Screening System is also reported in this paper.

Heating Greenhouses in Northern Climates with Power Plant Reject Heat

Abstract Since 1970, Northern States Power Company (NSP) has been investigating beneficial uses of the heat energy available in condenser cooling water at electric generating plants. The concept of utilizing condenser cooling water for agricultural heating applications proposed initially by researchers at Oak Ridge National Laboratory (ORNL) in the late 1960’s was of particular interest to NSP, since new generating plants were then in the planning stages that would utilize closed-cycle cooling systems. Close-cycle cooling system designs result in condenser outlet water temperatures of generally not less than 85° F during the winter heating season. With this knowledge, Northern States Power Company approached the University of Minnesota Agricultural Experiment Station and requested their assistance to determine the best potential application for utilizing condenser cooling waters in agricultural applications. After extensive investigation into the field of waste heat utilization and several visits to waste heat related projects, the University of Minnesota advised that the concept of utilizing this waste heat for greenhouse heating appeared to have near-term potential.

The measurement of substation ground resistance and its use in determining protection for metallic communication circuits

The increased use of metallic communication circuits in electric substations requires that adequate protection be provided for personnel and equipment during fault conditions. The design of such protection requires a knowledge of the behavior of ground systems, ground rise calculations, and communication techniques. This paper discusses the problem in three parts: I. A development of the characteristics of and measurement techniques for groundbeds and a discussion of how interconnections affect the measurement problem. A new measurement technique is developed which is capable of accurately measuring the resistive part of the grounding impedance of interconnected groundbeds. II. A discussion of the proper use of fault study and ground resistance information for the calculation of ground potential rise. III. A description of the metallic communication circuit protection techniques used by Northern States Power Company.

Switching Surges on Northern States Power Company's 345-kV Circuits

This paper reports the results of field tests conducted on the Northern States Power Company's 345-kV transmission system which investigated the effects of various system switching operations on transient overvoltages. Following the field tests a transient network analyzer was used to duplicate the field tests and then explore the maximum switching transients which system parameters could produce.

Application of Statistical Methods in the Design and Uprating of Wood-Pole Transmission Lines

The electrical insulation design of a proposed Northern States Power Company 345-kV wood-pole transmission line was examined, using statistical methods employed in the METIFOR program [1], introduced in 1964. These techniques, when incorporated with other methods of analysis, gave a predicted outage performance evaluation for this new line, which would interconnect Minneapolis-St. Paul, Minn., with Milwaukee, Wis., and Chicago, Ill. The techniques employed also afford a more comprehensive analysis of the performance of existing lines when uprated to a higher voltage class.

115-Kv Bus Switching Surges

In 1955, at the Black Dog Steam Station of Northern States Power Company (NSP), a 97-kv lightning arrester on the 115-2.4-kv reserve auxiliary transformer failed while de-energizing the 115-kv transfer bus with an air-break switch. The replacement of this arrester failed in 1957 when the 115-kv transfer bus was being energized through an air-break switch. These two arresters were not manufactured by the companies with which the authors are associated. Considering these failures as more than coincidental, a thorough investigation was initiated by NSP to attempt to explain how this transfer bus switching influenced the arrester failures. Analytical and Anacom (General Purpose Transient Analyzer) studies supplemented by field tests indicated sufficiently high overvoltages could be created by the transfer bus switch operation, due to a prestrike or restrike, to cause the lightning arrester to operate.

Operation of a Combined Steam and Hydro System: A Discussion of Operating Problems of the Northern States Power Company’s System Located in Minnesota and Wisconsin

Operation of a Combined Steam and Hydro System: A Discussion of Operating Problems of the Northern States Power Company’s System Located in Minnesota and Wisconsin

Discussion: “Operation of a Combined Steam and Hydro System: A Discussion of Operating Problems of the Northern States Power Company’s System Located in Minnesota and Wisconsin” (Colvin, James A., 1929, Trans. ASME, 51(3), pp. 177–181)

Discussion: “Operation of a Combined Steam and Hydro System: A Discussion of Operating Problems of the Northern States Power Company’s System Located in Minnesota and Wisconsin” (Colvin, James A., 1929, Trans. ASME, 51(3), pp. 177–181)

Improvement in Distribution Methods

The object of this paper is to point out how protective measures which have been applied to a low-voltage distribution network can be utilized to improve the operating characteristics of the entire distribution system, as well as materially lower its installation cost. Many of the developments herein described are novel departures from more generally recognized practises. They have all, however, withstood the test of time and usage. The common neutral system of distribution described has steadily increased in its application since first developed by the author for use in Toronto, Canada, about 16 years ago. It is at present the standard system with a number of large utilities with an aggregate capacity of some 300,000 kw. The particular system described is that of the Northern States Power Company in the Minneapolis territory, representing about 60,000 km., or about one-half the total output of this widespread organization. The heavy duty a-c. underground network and the remote-control multiple street lighting systems described are both later developments that are more or less inter-related with this common neutral development.