New possibilities in amplitude and phase comparison techniques for loss of excitation and out-of-step relays

This paper points out some new possibilities in multi-input amplitude and phase comparison techniques for the development of static relays to protect a synchronous machine against loss of excitation or out-of-step conditions. The desired discrimination characteristics of the relay are obtained with a simple mode of relay circuitry. Comparator models, which effect either hybrid or phase comparison of relaying signals, are described in block schematic form.