Novel Zero-Sequence Blocking Transformer (ZSBT) Using Three Single-Phase Transformers

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.