Design of a Digital Standard Inverse Overcurrent Relay Using Arduino Uno as a Microcontroller

This paper aims to design a digital overcurrent relay with a characteristic of a standard inverse that can comply to the IEC standard 60255. The overcurrent relay which is used to protect one phase of an alternating circuit (AC) from the overcurrent disturbances consists of an Arduino Uno as a microcontroller to control the operation of the relay, a current sensor ACS712 with the allowable current up to 30A used to detect the input current to the relay and a circuit breaker module. The Time Multiplier Setting (TMS) of the relay was set at 0.1. The trip test of the relay was conducted at a varying TMS from 0.1 to 0.4 and the operation current was limited to 1A. When a fault current was detected at 2.02A, it was found that the operation time of the relay occurred at 1008ms with a TMS of 0.1 and at 3932ms with the TMS of 0.4. Increasing the fault current to 3.99A decreases the operation time to 504ms at the TMS of 0.1 and to 2016ms at TMS of 0.4. From these findings, it can be concluded that the prototype of the digital overcurrent relay can fulfill the inverse characteristic of the standard IEC 60255.