IEEE 421.5-1992

When the behavior of synchronous machines is to be simulated accurately in power system stability studies, it is essential that the excitation systems of the synchronous machines be modeled in sufficient detail, see [12]. The desired models must be suitable for representing the actual excitation equipment performance for large, severe disturbances as well as for small perturbations. A 1968 IEEE Committee Report (see [6]) provided initial excitation system reference models. It established a common nomenclature, presented mathematical models for excitation systems then in common use, and defined parameters for those models. A 1981 report (see [7]) extended that work. It provided models for newer types of excitation equipment not covered previously as well as improved models for older equipment. This document, based heavily on the 1981 report, is intended to again update the models, provide models for additional control of features, and formalize those models in a recommended practice. To some extent, the model structures presented in this document are intended to facilitate the use of field test data as a means of obtaining model parameters. The models are, however, reduced order models and do not represent all of the control loops on any particular system. In some cases, the model used may represent a substantial reduction, resulting in large differences between the structure of the model and the physical system. The excitation system models themselves do not allow for regulator modulation as a function of system frequency, an inherent characteristic of some older excitation systems. The models are valid for frequency deviations of ±5% from rated frequency and oscillation frequencies up to about 3 Hz. These models would not normally be adequate for use in studies of subsynchronous resonance or other shaft torsional interaction problems. Delayed protective and control functions that may come into play in long term dynamic performance studies are not represented. A sample set of data (not necessarily typical) for each of the models, for at least one particular application, is provided in Appendix . A suffix "A" is used with the version of all models described in this report to differentiate them from previous models.



New IEEE Standard - Superseded. Superseded by IEEE Std 421.5-2005. Excitation system models suitable for use in large scale system stability studies are presented. With these models, most of the excitation systems currently in widespread use on large, system-connected synchronous machines in North America can be represented. They include updates of models published in the IEEE Transactions on Power Apparatus and Systems in 1981 as well as models for additional control features such as discontinuous excitation controls.