An asymmetrical fault line selection based on I2 scalar product research in distribution system with DGs

The introduction of DG in distribution system has many negative impacts on conventional protection. Typically it will deteriorate selectivity and sensitivity of existing relay. It will change a simple radiation distribution system with single source into a complex multi-source system. To make the nowadays broadly used protection scheme and their coordination meet the great challenge, this paper proposed a novel fault line selection approach based on negative sequence current (I₂) scalar product (I₂SP) to locate fault line in a DG system. Negative sequence current has a powerful ability of fault identification. I₂SP can effectively decide direction of fault location without voltages. It will help to develop a wide-area protection scheme in DG system. It can easily eliminate relay mal-operation and simplify relay scheme in distribution system because of introduction of renewable energy sources. The simulation results proved its effectiveness and practicability of the method.