8th International Conference on Advanced Power System Automation and Protection (APAP2019)

994 / 2019-05-05 20:48:32

A rapid identification methods for line differential protection area fault of independent CT

two-thirds wiring; CT saturation; current polarity; differential flow; virtual braking; area fault

Analyzing cause of two-thirds wiring line differential protection misoperation because of edge switch CT saturation,according to CT phase current polarity and amplitude relation of edge and mid switch,put forward a virtual braking method of current sampling points amplitude comparison to fast identify area fault. By comparing polarity and amplitude of edge and mid switch phase current,and virtual braking of phase current sampling points to identify fault location;If area fault phase current polarity is the same, otherwise the polarity is opposite. In addition, when happending on outside transfertion area fault with CT saturation flow is no longer symmetrical, identifying characteristics of differential differential current and differential braking current , further determining fault location.The method is simple and unaffected by transient high harmonic.