Phase-comparison carrier-current relaying
A. J. McConnell, T. A. Cramer, H. T. Seeley · Electrical Engineering · 1945
DIFFERENTIAL PROTECTION is recognized as the ideal means of quickly isolating faulty electric equipment. The carrier-current relaying system described herein is a differential system comparing the phase angles, via a carrier-current channel, of the currents entering and leaving a transmission-line section, and is known as phase-comparison carrier-current relaying.