D2010_beta - 1 Tracking the Eastern Interconnection...

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1 Abstract -- The Eastern Interconnection frequency governing characteristic, sometimes called Beta, has been tracked by one of the authors for a period of more than 15 years. While there are some errors inherent to the process followed, we believe that the errors do not obscure the overall trend. We have found that Beta has been declining and has reached a level of approximately 25 MW/mHz. This has important implications in system behavior, particularly in situations involving islanding. Study assumptions need to reflect this observed reduction in governing response. Index Terms -- Frequency Governing Characteristic, Combined frequency governing characteristic, Beta, Frequency Response, Generation Governing, Load Governing. I. NOMENCLATURE A. Beta The parameter Beta is the constant of proportionality between the change in generation or load and the resulting frequency change. We will use Beta beginning with an upper case B to represent Beta for the entire interconnection. The same term beginning with a lower case letter would be the same parameter for some part of the interconnection, such as a control area. The upper and lower case Greek letters could well be used, but we have not done so in this paper. B. Units Tenths of Hz have been used in this context in the past; however in our large interconnection we routinely speak now of frequency deviations in milliHertz abbreviated as mHz. We also suggest that milli is a preferred engineering unit prefix, and tenths, or “deci,” is not. The use of milliHertz results in convenient numbers. For example, for typical incident with a loss of 1000 MW and a decline of 31.6 mHz, the resulting Beta is 31.6 MW/mHz. For all these reasons, we will use mHz for frequency changes and MW/mHz as the unit of Beta. C. Time Dates and times of observed events are the trigger times of various PMUs and disturbance recorders which are synchronized using GPS clocks. No offsets have been applied to the UTC time scale obtained. The term we have used for this Time Zone is “Zulu,” represented by the letter “Z” which is the preferred term We believe power system time sequence data should be recorded using Zulu Time Zone. James Ingleson is with RLC Engineering, 402 Bond Road, Altamont, NY 12009 USA. (e-mail: jim.ingleson@rlc-eng.com) Eric Allen is with NERC, 116-390 Village Blvd., Princeton, NJ 08540 USA. (e-mail: eric.allen@nerc.net) D. Eastern Interconnection The Eastern Interconnection is the power system interconnection that includes the areas of United States and Canada which are east of the Rocky Mountains. The state of Texas and province of Quebec are not part of this synchronous interconnection. In this work we will speak of the Eastern Interconnection as simply “the interconnection.” II. INTRODUCTION n the average of somewhat more often than once per day, there occurs a significant decline in frequency on the interconnection because of the sudden loss of a single generating unit or a group of units. Within several seconds, the power system arrives at a new lower frequency, and a new equilibrium state is found.
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This note was uploaded on 07/14/2011 for the course ECE 522 taught by Professor Tomsovic during the Summer '10 term at University of Florida.

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D2010_beta - 1 Tracking the Eastern Interconnection...

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