In this paper the effects and issues due to islanding operation with distributed generation in a distribution network are shown.Two specific conditionsare assessed (intentional island and unintentional island) by analyzing the main influence on load currents, voltage profiles and frequency of the system.Whence, the IEEE 37 nodes test grid was modeled and distributed resources locations were varied along the network whilst its capacity is changed from 100 kW to 1200 kW.