Design and Evaluation of Electrical Protection for Grid-Connected Microgrid with Renewable Energy Resources

Abstract

The objective of this article was to establish the dependability of the Over Current protection (OCP) technique in safeguarding microgrids that use inverter connected Renewable Energy Sources (RES) for lower-voltage distribution channels.  The simulation program was used to conduct OCP system experiments to demonstrate its dependability. The simulations included contrasting the system's performance in grid-connected mode, both with and without RES production, and in the island state.  The calculations are performed with a lower-voltage distributing system design.  The average relay tripping time for single line-to-ground (SLG) faults via grid mode, without RES systems, is 0.131 seconds. For line-to-line (LLL) faults, the mean tripping time is 0.121 seconds. Regarding RES generators, the mean relay tripping duration climbed to 0.199 seconds and 0.135 seconds, combining both. This is caused by the fault current generated by the addition of RES production, which limits the current detected by the specified Over-Current (OC) relays. The results indicated that a few Over-current relays failed to activate during the island scenario, resulting in a lack of synchronization and reduced fault currents. In the island scenario, the system underwent further testing at various generation ranges (15%, 50%, and 80%), revealing a slight disparity in mean tripping time across different generation stages.