Rebuilding of three-phase load voltage during single-phase auto reclosing in medium voltage distribution lines

Abstract

Most faults in medium voltage (MV) distribution lines are temporary single line to ground (LG) faults. Single-phase auto reclosing (SPAR) may be used to remove the LG fault producing highly unbalanced and low voltage across the load during the reclosure dead time. The negative sequence voltage produced may cause severe over heating in three-phase induction motors. It is proposed to connect a zigzag winding grounding transformer at the remotest load bus to rebuild the three-phase voltage during the SPAR dead time. The zigzag transformer neutral should remain disconnected from the ground during normal operation.