Overcurrent protection of distribution network with distributed generation

Penetration of distributed generation (DG) into the distribution network has changed the nature of conventional power distribution system, which was radial in nature. Power flow is now bidirectional and thus the increased penetration of DGs imposes a challenge on the conventional protection scheme which is only meant for passive distribution network. This paper deals with the protection of active distribution network (ADN). Huge penetration of DGs in the distribution network is expected in the near future, thus the proposed protection method assumes that the distribution network will have a significant penetration of distributed generation in islanded scenario and the fault current is maintained upto 5 to 7 pu during a shift from grid connected to islanded mode. The overcurrent relays (OCR) protects the downstream faults whereas the directional overcurrent relays (DOCR) are used for the protection of upstream faults. The overcurrent relays settings are obtained with the help of short-circuit analysis of network in grid connected and in islanded mode. The simulations are done using DIgSILENT power factory.