Development of Prototype Protection Setup for Standalone Solar Power System

Abstract

This paper presents development of an electrical protection scheme using <i>Arduino</i> microcontroller for a prototype solar power system. First, literature review is carried out on numerical relays for the protection scheme having solar panel output of 12V DC, which is then converted into 220V AC power output using an inverter. Specifically two types of faults are demonstrated neglecting the fault impedance: (i) Over Current fault; (ii) Differential Overcurrent fault. Subsequently, as per the magnitude of the fault current, an Inverse-Definite Time (IDMT) characteristics are studied to <i>pre-set</i> the operational features of a relay. Afterwords, the relay signals are programmed using an <i>Arduino Microcontroller</i>. The proposed setup consists of 115V/15V transformer; 50W variable rheostat; electro-mechanical relay and low burden electronic current sensors (ACS712) to measure fault current. Then 220V AC auto-transformer is used to tap the voltage to a level of 115V as per the opted transformer. The work identifies the difference between the magnitudes of input-output of currents of a transformer and if magnitude is more than the pre-set value in AC section, finally a tripping signal will operate to disconnect the abnormal part. Further, setting of differential relay is investigated to find the efficient operation of the solar power system. Then validation of prototype model is done by creating an intentional fault using variable rheostat as load. This work investigates efficiently to obtain accurate results on both internal and external faults. In total the proposed scheme consumes less power, which is suitable to develop a prototype protection scheme.