Compensation of DGs impact on overcurrent protection system of smart micro-grids

Traditional distribution networks have radial and unidirectional topology. The protection system of these networks is based on time and current coordination of overcurrent protection devices, which are negatively affected by DGs. The coordination of these devices is the most important issue of the protection system. DGs increase the voltage of faulted feeders at their connection point and cause the under-reach in the time inverse characteristic of overcurrent protection devices. In this paper, a self-adaptive method for smart micro-grid is proposed, which compensates the under-reached fault current seen by the relay. Therefore, there is no need to change the settings of protection devices for different operation conditions.