Islanding detection method for distributed generations interconnected with utility networks

The present invention is to provide a new method for assessing a more reliable for detecting islanding of a distributed power source by analyzing the information of the various system parameters to improve the vulnerability of existing power distribution islanding detection method. Distributed single operation determination method of the present invention is a method for determining whether a sole operation of the distributed power associated with the power system, comprising the steps of: measuring the voltage and current at the distributed power system interconnection point; Calculating a voltage unbalance index Step using the calculated voltage unbalance index The calculated voltage unbalance index variation determining whether And it is determined as Distributed single operation if more than a predetermined threshold value includes the steps to export the trip (TRIP) signal.