UR-FAS-RELE

An out-of-step relay for an alternating potential electric power transmission line is disclosed wherein the decision to trip is determined by the rate of change of the phase relationship of the voltages at the remote and local ends of the transmission line as well as by the magnitude of the phase difference of the remote and local voltages. More particularly, there is described a pair of AND networks which provide two timing signals proportional to the phase difference of the voltages and a pair of timing devices; one of said devices timing the difference in the time of the two timing signals to establish the rate of change of the phase relationship and the other of said devices timing the sum of the two timing signals to establish a signal which is representative of the magnitude of the phase relationship.