The Grounded Wye-Delta Transformer with a Zig-Zag Transformer

A most common use of a zig-zag transformer connection is to provide a grounding source for a three-wire delta connected distribution line. When a ground fault occurs on a delta line since there is no ground return path it is impossible to detect that the fault has occurred. In such cases a zig- zag transformer can be connected at the source to provide a path for the ground current to flow back to the source. This paper describes the basic zig-zag transformer and develops a general model that includes the grounded wye-delta bank and the zig-zag transformer. Results of power-flow and short circuit analyses are included using a new test feeder that is like the IEEE Four Node Test Feeder.