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Zero-sequence blocking transformers (ZSBTs), used to block the zero-sequence components that are present in a three-phase system, are commonly built winding the three phases around the same core limb. They are difficult to construct, especially in high-power applications that use large cross-sectional cables, as they require a symmetrical winding distribution for not to produce any flux for positive- and negative-sequence components. This paper presents a novel ZSBT configuration using three single-phase transformers. Although slightly greater in size, they can be easily wound, even when thick cables are used. Moreover, the proposed topology can be used as a simulation model of any ZSBT configuration, where core losses and magnetic saturation of the core are included by connecting a single inductor to the secondary windings of the transformers. This paper provides full details of the circuit and is supported by simulation and experimental results of the proposed ZSBT.
Date of Publication: March 2013