New IEEE Standard – Superseded.Replaced by 421.1-2004 (SH/SS95244) Abstract: IEEE Std 421.4-1990, IEEE Guide for the Preparation of Excitation System specifications, is intended to be a narrative description of items and functions that should be considered in the preparation of excitation system specifications. This guide applies to excitation systems for synchronous machines rated at 5000 kVA or larger.
