IEEE 421.2

Abstract

Foreword&#160;<br>This guide presents dynamic performance criteria, definitions, and test objectives for excitation control systems as applied by electric utilities. It should be specifically noted that the term excitation control system refers to the entire control system including the synchronous machine and power system as well as the excitation system.<br>The Working Group on Excitation Control System Dynamic Performance of the Excitation Systems Subcommittee of the Power Generation Committee adopted many definitions and performance criteria, which are common to all control systems, and derived others specifically related to excitation control systems. In doing this, the material in IEEE Std 421.1-1986, IEEE Standard Definitions for Excitation Systems for Synchronous Machines (ANSI) and IEEE Std 100-1988, IEEE Standard Dictionary of Electrical and Electronics Terms (ANSI) was heavily used. Efforts were made not to conflict with existing definitions and criteria, but to clarify, supplement, and more fully define them as related specifically to excitation control systems. Definitions from these standards, which are reproduced in this standard, are set in italics in Section 3.<br>In preparing this guide, the working group recognized that both factory testing and field testing of excitation control systems and some of their components are costly and often impractical. Alternator-rectifier excitation systems in which the terminals of the exciter may not be available may preclude field testing of the exciter separately. Compound source excitation systems whose power is derived from the generator currents and voltages present special difficulties. Providing a load which reasonably duplicates the generator field characteristics so that regulation effects and proper waveforms can be adequately simulated may not be economically justifiable. Field tests on units under normal operating conditions are constrained to comply with the operating and security requirements of the power system, which often prohibit large excursions of the excitation control system variables. For many applications, it is necessary to devise practical test procedures for individual components and then by analytical means, to verify the total excitation system performance.<br>The need for models that accurately simulate the operation of excitation control systems during system disturbances demands effective test methods. However, the practical limitations on tests make it difficult to measure the parameters required for models. One solution is the collection of more complete data during system disturbances. Present instrumentation practices generally do not include the collection of data from enough excitation control system variables to permit the data to be used for model refinement. Improving the quantity and quality of data collected during system disturbances may be the only practical way to obtain the data required to significantly improve the accuracy of large signal models.<br>This revision incorporates the changes in IEEE Std 421.1-1986, IEEE Standard Definitions for Excitation Systems for Synchronous Machines (ANSI), which substituted a single definition, excitation system nominal response, for several previous definitions that included the phrase &#8220;response ratio.&#8221; Root locus techniques applicable to excitation control system performance evaluation are added in this revision. The material in IEEE Std 421A-1972, IEEE Guide for Identification, Testing, and Evaluation of the Dynamic Performance of Excitation Control Systems (ANSI), pertaining to power system stabilizers is retained. However, the IEEE Tutorial on Power System Stabilization Via Excitation Control (81EH0175-0 PWR) provides substantial supplemental material. The previous material related to synchronizing and damping torques is omitted.<br>The following members of the IEEE Power Generation Committee balloted and approved this guide for submission to the IEEE Standards Board:<br>M. S. Baldwin<br>I. B. Berezowsky<br>L. D. Boydstun<br>G. R. Brockschink<br>J. B. Cannon<br>R. W. Cantrell<br>R. L. Castleberry<br>E. F. Chelotti<br>R. E. Cotta<br>M. L. Crenshaw<br>P. L. Dandeno<br>P. M. Davidson<br>K. J. Dhir<br>D. Diamant<br>G. Engmann<br>W. B. Gish<br>D. I. Gorden<br>R. K. Gupta<br>J. H. Gurney<br>J. D. Hurley<br>J. H. Jones<br>C. E. Kneeburg<br>S. B. Kuznetsov<br>P. Landrieu<br>R. A. Lawson<br>D. C. Lee<br>P. A. Lewis<br>J. E. LeClair<br>J. T. Madill<br>O. S. Mazzoni<br>G. R. Meloy<br>M. W. Migliaro<br>D. H. Miller<br>D. R. McCabe<br>L. G. Ottobre<br>R. E. Penn III<br>C. R. Pope<br>R. J. Reiman<br>J. R. Ribeiro<br>D. E. Roberts<br>E. P. Rothong<br>J. E. Stoner, Jr.<br>L. A. Tauber<br>I. Trebincevic<br>T. R. Whittemore<br>R. Zweigler<br>Members of the Working Group of the Excitation Systems Subcommittee, which formulated the 1978 standard, were:<br>F. W. Keay, Chair<br>K. E. Bollinger<br>R. T. Byerly<br>M. L. Crenshaw<br>P. L. Dandeno*<br>C. W. Drake<br>L. E. Eilts<br>G. T. Heydt<br>R. A. Lawson<br>D. C. Lee<br>J. F. Luini<br>G. R. Meloy<br>R. G. Pillote<br>C. Raczkowski<br>N. W. Simons<br>G. I. Stillman<br>M. Temoshok<br>*Liaison from the Power System Engineering Committee<br>Members of the Working Group of the Excitation Systems Subcommittee, which revised this standard, were:<br>T. R. Whittemore, Chair<br>M. L. Crenshaw<br>P. L. Dandeno*<br>K. J. Dhir<br>R. G. Farmer*<br>W. B. Gish<br>D. I. Gorden<br>J. H. Gurney<br>J. D. Hurley<br>R. A. Lawson<br>D. C. Lee<br>G. R. Meloy<br>D. H. Miller<br>J. R. Ribeiro<br>L. A. Tauber<br>I. Trebincevic<br>*Liaison from the Power System Engineering Committee<br>When the IEEE Standards Board approved this standard on May 31, 1990, it had the following membership:<br>Marco W. Migliaro, Chair<br>James M. Daly, Vice Chair<br>Andrew G. Salem, Secretary<br>Dennis Bodson<br>Paul L. Borrill<br>Fletcher J. Buckley<br>Allen L. Clapp<br>Stephen R. Dillon<br>Donald C. Fleckenstein<br>Jay Forster*<br>Thomas L. Hannan<br>Kenneth D. Hendrix<br>John W. Horch<br>Joseph L. Koepfinger*<br>Irving Kolodny<br>Michael A. Lawler<br>Donald J. Loughry<br>John E. May, Jr.<br>Lawrence V. McCall<br>L. Bruce McClung<br>Donald T. Michael*<br>Stig Nilsson<br>Roy T. Oishi<br>Gary S. Robinson<br>Terrance R. Whittemore<br>Donald W. Zipse<br>Scope<br>This guide includes criteria, definitions, and test objectives for evaluating the dynamic performance of excitation control systems as applied by electric utilities. The term &#8220;excitation control system&#8221; (see Fig 1) is used to distinguish the combined performance of the synchronous machine, power system, and excitation system from that of the excitation system alone (see IEEE Std 100-1988, IEEE Standard Dictionary of Electrical and Electronics Terms (ANSI) [1]¹ and IEEE Std 421.1-1986, IEEE Standard Definitions for Excitation Systems for Synchronous Machines (ANSI) [2]). The primary purpose of this guide is to provide a basis for evaluating closed-loop performance of excitation control systems for both large and small signal disturbances; confirming the adequacy of mathematical models of excitation control systems for use in analytical studies of power systems; identifying objectives for tests of excitation control systems and their components; and preparing excitation system specifications and additional standards. Portions of this guide will also serve as educational material for people who are becoming acquainted with excitation control systems.<br>Traditionally, large signal performance (see 2.1) has been more closely associated with equipment specification and acceptance testing, while small signal performance (see 2.2) has been more closely associated with stability and model studies. Matching actual disturbance data with model simulations requires that both large and small signal performance criteria be considered during design specification and acceptance testing.