A Combined Directional and Faulted Phase Selector Element Based on Incremental Quantities

In this paper differential incremental or superimposed voltage and current quantities are used in order to determine directionality of a fault in a network. It is shown that this can be accomplished by performing three scalar products between three voltage and current phasor pairs. The relative levels of these same three scalar products can be furthermore used to identify the faulted phases. While, in ultra-high-speed directional comparison relays, superimposed voltage and current had to be treated in the time domain in order to get speed, in this paper all computations are done in the frequency domain.