An Adaptive Protection System for Micro- Grid Operating in Grid-connected and Islanded Modes

This paper is aimed at accurate estimation of the fault current at all Micro Grid (MG) buses during grid-connected and islanding modes with different load types (dynamic or static). Following fault-current estimation, a design of an adaptive protection system is sought to protect the MG irrespective of the mode of operation or the type of load. The adaptive protection system has been designed using three calculation methods. The first method is the conventional method which depends on representing the power system by voltage source and Thevenin impedance. The second method depends on the IEC standard calculation method and its correction factors. The third method is a novel proposed method where all system real conditions have been taken into consideration. The proposed adaptive protection system is able to accurately estimate the value of fault currents in the MG and hence the relay tripping currents during any operating condition like grid connected mode, islanding mode, static loads, dynamic loads and existence of renewable micro sources (photovoltaic and wind). The proposed adaptive protection system has been tested for aggregated MG system planned to be installed in Toshka area in Egypt.