An analytical-based method to postpone generator tripping during loss-of-excitation events

There are several practical reports describing that a loss of excited generator (LOEG) can operate as an induction generator for a limited time without exposing any damage. During this period, the generator may be again brought to the normal condition by restoring the excitation system. This paper presents an analytical strategy to postpone generator outage/tripping subsequent to a loss-of-excitation (LOE) event. To do this, various practical limitations of the generator during LOE are formulized and appropriate indices are proposed. These indices are exploited to design a remedial control action (RCA) to preserve the generator during LOE and to postpone generator tripping without any destructive damage to the both generator and power system. Investigating all types of LOE events in single- and multi-machine test systems demonstrate that the proposed approach provides a practical and feasible strategy to continue secure operation of the LOEG to provide an opportunity to restore the excitation system.