摘要：This paper presents and tests three earthing system. (TT, TN and IT) for m.cro-Grid (m.) protection against various fault types when the m. transferred to the islanding m.de. The m.in contribution of this work is including the m.dels of all m.cro sources which interfaced to the m. by power electronic inverters. Inverters in turns are provided with current lim.ters and this also included with the inverter m.dels to exactly sim.late the real situation in the m. during fault tim.s. Results proved that the m.st suitable earthing system.for m. protection during the islanding m.de is the TN earthing system. That system.leads to a suitable am.unt of fault current sufficient to activate over current pro-tection relays. With using TN earthing system. touch voltages at the faulted bus and all other consum.r’s buses are less than the safety lim.ted values during islanding m.de. For the two others earthing system. (TT and IT), fault currents are sm.ll and nearly equal to the over load currents which m.ke over current protection relay can not differentiate between fault currents and overload currents. All m.dels of m.cro sources, earthing system., inverters and control schem.s are built using m.tlab?/Sim.link? environm.nt.