AN ADAPTIVE OUT-OF-STEP RELAY

The paper describes the development of an adaptive out-of-step relay, from the formulation of its concept to its field implementation at the Florida-Georgia interface. Adaptive relaying seeks to make adjustment s to the relay characteristics as system conditions change, thereby ma king the relay more attuned to the prevailing power system conditions. The work described here began as a theoretical examination of the out -of-step relaying application, its possible shortcomings, and the oppo rtunities to make adaptive improvements. It is shown that for a sq ste m that behaves primarily as a two-machine power system, the out-of-ste p relay could be made more secure by applying the principle of equal a rea criterion. The paper describes the theory of such a relay, its har dware configuration, and the system as it is installed in the field. T he newly developed technology of synchronized phasor measurements play s an important role in the realization of this relay. The paper includ es a summary of the field experience gathered over a period of one yea r.