Symmetrical Components Filters for Power System Protection Based on Converters with Rotating Magnetic Field

This paper presents a new method to implement positive, negative and zero sequence components filters based on converters with rotating magnetic field. The filters are directly connected to the traditional instrument transformers, provide galvanic isolation and generate symmetrical components signals that can be used for power system protection purpose. Filter output is the voltage proportional to symmetrical components current magnitudes. The paper provides schematic diagrams of the sequence components filters and outlines the basic theoretical principles for their design. The methodology to create various sequence components filters by simple rewiring of the secondary rotating magnetic field converter windings is also presented.