The prime purpose of grounding transformer is to provide a neutral point on a three-phase ungrounded power system. The configuration of grounding zigzag transformer is usually wye-delta or zig-zag. The basis of this paper is a system where ungrounded connection is detected. The bus rated 15KV between two transformers falls on delta connected winding of transformer. As a fact, Delta connected system has no grounding provision. In case the ground fault occurs on bus, there is no means the fault

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... n be detected and fault current has no path to flow. As a solution a grounding zigzag transformer is suggested. Using PSCAD/EMTDC simulator, effects of balanced and unbalanced load, single line to ground and double line to ground fault is simulated. Keywords: Ungrounded system, zig-zag transformer, single line to ground fault, double line to ground fault, PSCAD/EMTDC Software.