Abstract: Digital overcurrent relay apparatus utilizing sampling, digital conversion and digital comparison techniques is described. The apparatus provides a trip signal after an alternating current in a line being monitored by the apparatus exceeds a preset pick up value for a period of time which is an inverse function of the magnitude of the current expressed in multiples of pick up value.

Abstract: An analog-to-digital converter is described in which a sequence of samples of an analog signal is converted into a sequence of binary numbers which appear at the output terminals of a composite counter comprising a first counter and a second counter. The first and second counters are gated in sequence by gating waveforms to provide for each sample the count corresponding to the logarithm of the sample. The gating waveforms are derived from a charge and discharge cycle of a capacitor to which the sample is supplied. Selected times in the charging and discharging portions of the cycle are utilized for deriving the gating waveforms.