Adaptive protection scheme with fault detection, classification and isolation features for off-grid distributed generation system

Abstract

Distributed generation (DG) technology combines sources that run on fossil fuel, renewable energy and/or waste heat. The DG systems work either in grid connected mode or off-grid (standalone) mode. Protection and control issues arise in DGs due to the inherent small capacities and intermittent nature of sources, especially the renewable energy sources. In general conventional protection schemes are ineffective under off-grid operations of DGs especially where large contribution comes from renewable energy sources. The continuously shifting characteristics of sources due to environmental changes cause changes in the fault levels of the system. This paper presents an adaptive protection scheme, which continuously monitors current and voltage magnitudes in the system and adapts the new fault levels as per the instantaneous characteristics of the sources. It also provides for fault classification and fault isolation to allow quick restoration of healthy status of DG. All the details of this work are presented.