Comparison between open-ring and closed-ring grids reliability

Closed-ring operation of distribution systems has several advantages over radially-operated ones. Closed-ring achieves availability of power on demand, reduce grid losses and maintain the reliability at acceptable level. This paper evaluates the reliability of 6-bus closed-ring operated network based on total loss of continuity criterion. The results show dramatically improvement in reliability of closed-ring grids in comparison with normally-open ring distribution grids, the annual down time decreases from 8.7 hours to about 3.0 seconds, and ENS decreases to about 99.97% over the open-ring grids.