Bridge methods for determining symmetrical components of current, voltage and power, with special reference to electrical machinery

The isolation and separate measurement of symmetrical-component quantities is a logical corollary to the theoretical principles employed in the analysis of unbalanced polyphase systems. The paper provides a comprehensive account of the design, construction and adjustment of bridge networks which reduce to a routine procedure the measurement of sequence components of current, voltage and power in 3-phase and 2-phase systems. The bridges are designed for use with instrument transformers, and the significance of frequency variations and meter impedances are discussed. Examples of a few practical applications are included.