Evaluation of transient stability limit using a transient time margin sensitivity approach

This paper addresses the issue of how to evaluate transient stability limit using a transient time margin (TTM) approach and the sensitivity of this m argin to key system variables such as generation and load. This allows fast control decisions to be assessed for a power system on-line control purpos e. The difference between fault clearing time and critical fault clearing t ime, called the TTM, is proposed as a transient stability index. The single machine equivalent system (SMES) is employed to represent the TTM as a fun ction of system parameters such as plant generation and load, and the sensi tivity of the TTM to these parameters is found. The generation or load chan ges that can be made while preserving stability, or the changes that are ne eded to restore stability in dynamically insecure systems, are next derived from this sensitivity. Test results for several real size test power syste ms show that the proposed approach is feasible and promising for on-line co ntrol application. (C) 1999 Elsevier Science S.A. All rights reserved.