Abstract— This paper presents a novel hybrid power system
overcurrent protection relay based on rotating magnetic field
principle. The device is directly connected into the regular
current transformer (CT) secondary circuit and consists of an
electromagnetic component with rotating magnetic field and an
electronics circuit employed to generate a low-level analog
output, which is directly proportional to the magnitude of the
input current signal. The relay output is produced without using
numerical signal algorithms by the hybrid physical system.
Moreover, the relay provides galvanic isolation from the
secondary CT circuit and is capable of auto-correcting the input
current waveform distortions introduced by CT saturation.