Abstract
A refinement to the way that overcurrent (O/C) protection of Inverse Minimum Time (IDMT) characteristic is applied in order to achieve reliable operation of a power system that contains Distributed Generation (DG) is required. This system is a micro-grid system marred with complexities of bidirectional power flow which the earlier generations of relays were not capable of dealing with. This paper investigates the application of adaptive O/C protection for effective selectivity, proper co-ordination of tripping and generally, proper management of increased fault levels introduced with connection of DG into the grid. Incorrect tripping has always resulted in nuisance tripping of circuit breakers deterring productivity, upsetting end-users and even posing a risk to life. Directional overcurrent protection is applied in Intelligent Electronic Devices (IED’s) and prove through simulations that correct coordination of cascaded breakers in a mesh system is achieved with minimal disruption of supply. Different settings groups are applied to an IED relay and a seamless migration between settings groups is achieved though relay input logic.