How do I use a Grounding Transformer?
Three-phase grounding transformers provide an artificial neutral for grounding. The main requirement is a specific zero-sequence impedance from the Zig-Zag or the Wye/Delta transformer in addition to the fault current withstand rating. For grounding purpose, only the Zig-Zag or a Wye/Delta connected transformer can be used. Autotransformers will have a high zero-sequence impedance and hence, cannot be used for grounding. Air-core reactors can be normally connected between the artificial neutral and ground to provide some additional current-limiting impedance.
Grounding transformers are often required by the utility to attach a load generator such as solar, wind or a generator to the power grid.