A Fast Bus Bar Protection Based on Fault Superimposed Current Polarity Comparison

Abstract

In order to avoid problems caused by data synchronization of distributed bus bar protection and current transformer (CT) transient saturation, a novel fast bus bar protection was proposed based on fault superimposed current polarity comparison. The bus protection takes the pre-fault voltage and pre-fault current as the new reference for polarity comparison, and it utilizes the relationship between the pre-fault current and superimposed current to identify the fault direction. For internal faults to bas bur, the polarities of the branches connected to the faulted bus bar are identical, for external faults, the polarities are not exactly same. The time window length of fast bus bar protection is very short, and the relay is also immune to the CT transient saturation. The theoretical analysis and PSCAD/EMTDC simulation tests show that the bus protection operates reliably and rapidly, and that its performance is immune to the influences of various fault types, fault path resistance and fault inception angle.