Definition
A mathematical technique for analyzing unbalanced three-phase faults by decomposing any set of unbalanced three-phase phasors into three balanced sets: positive sequence (normal ABC rotation), negative sequence (reverse ACB rotation), and zero sequence (all three in phase). Developed by Charles Fortescue in 1918, symmetrical components allow engineers to analyze single line-to-ground, double line-to-ground, and line-to-line faults using straightforward network equations. The zero-sequence network path depends on transformer winding configurations and system grounding — making grounding design a critical factor in fault current magnitude and relay coordination.
Topic Deck
Electrical Engineering Fundamentals
Source
FERC Pro Forma OATT / LGIP