Design of Bypass Switches for HV/MV Hybrid Transformer Auxiliary Converters

The design of bypass switches is essential to protect the auxiliary converter connected to the HV/MV power transformer. In this paper critical fault cases are used to determine overcurrents in the HT auxiliary converter. The overcurrents are determined with a power transformer model that includes a core saturation model and parasitic capacitances between the transformer windings. Based on the determined overcurrent levels two bypass switches are designed to protect the HT auxiliary converter against critical faults.