Current transformer saturation recognition - by spatial vector tracking of sec. current when opposing components of fundamental oscillation are blocked for prodn. of difference criteria

摘要

Three-phase line currents (i1-i3) are converted (1) into analogue quantities which are low-pass filtered (2) and digitised (3) for transformation (4) into real and imaginary parts of a complex rotating spatial vector (ip), which is converted by a frequency-changer (7) into a corresp. stationary vector. The recognition circuit (8) tracks the path elements of the spatial vector locus, and issues a warning signal (SE) within 5ms. (e.g. one quarter-cycle) of the onset of saturation. USE/ADVANTAGE - Esp. in differential protection of transformers, motors, lines or busbars. Saturation is recognised very quickly and reliably for undelayed remedial switching.