A Numerical Relay Implementation for Overcurrent Protection Based on ARM Cortex – M4 Microprocessor

Numerical overcurrent protection relays are the most extensively used devices to safeguard the power system from detrimental faults which might lead to a catastrophe. This paper presents a practical implementation of a numerical overcurrent protection relay based on ARM Cortex – M4 microcontroller embedded with a floating-point unit which has ability to perform complex calculation operations with a great accuracy for real-time protection algorithms. In order to implement, the system is designed to capture analog values of input currents by using Hall current sensors, analog conditioning circuits and 12 – bit A/D converters. Based on the measured input current values, a real-time signal processing algorithm for overcurrent protection is applied to produce an inverse - time characteristic according to the IEEE Standard C37.112-1996. The experimental results demonstrate that our numerical relay produces great performances in the real-time and has ability to protect electrical components from exceeded current faults satisfying the IEEE standard for overcurrent relays.