Double relay based sag, swell, over and under voltage protection and detection scheme

This paper proposes a protection scheme against voltage sag, swell, over voltage and under voltage to address the difficulties faced due to voltage fluctuations. Voltage sag and swells in the supply are detected and the relay circuit operates accordingly. This relay circuit along with a simulated graph has been shown. The passage of current through the circuit to be protected is allowed to flow only when no faults are observed. Hence the protective relay circuit prevents the output load from the hazardous effects of overvoltage and under voltage.