Wavelet Transform Based Islanding Characterization Method for Distributed Generation

The utilization of Distributed Generation (DG) unit s is rapidly increasing in power system and questions are raised regarding their effect on the system, energy management, and protection policies. DG can provide in some cases a significan t part of the load energy requirements. It is therefore important to consider the energy balance both locally, regionally and globally. Islanding operations of DG usually occur when the main utility supply is interrupted due to several contingencies (inrush currents, faults, etc ) while the DG is still supplying power to the distribution networks. These conditions have negati ve impacts on the system protection, restoration, operation, and management. Therefore, it is necessary to detect the presence of this condition and switch off the DG from distribution n etwork or isolate the DG with its load from the rest of the system. Conventional detection meth ods for islanding conditions are based on monitoring several parameters. These parameters inc lude voltage magnitude, phase displacement, and frequency change. However, in case of small changes in loading for DG, the contingency will be masked by normal operating condition. The conventional methods usually will not detect such an islanding condition. This paper utilizes the discrete wavelet transform to characterize the DG islanding contingency. The proposed methods were verified using a simple radial distribution system consists of a wind-Turbine induction DG, condensers, synchronous Condenser, and loads. The generated data were used to test the performance of the detection technique.