Module 3 : Sequence Components and Fault Analysis
Lecture 10 : Sequence Components
10.2 Sequence Components (contd..)
10.2.2

Negative Sequence Component
 

Negative sequence phasors are used to represent a balanced set of phasors (each of equal magnitude and phase difference of ) but in which the order of Vb and Vc has been reversed with respect to the positive sequence phasor. Thus,
    (3)
    (4)
  This is illustrated in fig 10.2. Note that placement of Va2 in x – y plane can be done arbitrarily. However, once Va2 is fixed both Vb2 and Vc2 are automatically fixed. Thus, negative sequence component have exactly two degrees of freedom which is to fix magnitude and angle of Va2.
If stator of a induction motor is subject to negative sequence voltage the rotor will rotate in a clockwise direction. i.e. in exactly opposite direction to that obtained with the positive sequence voltage.
 
10.2.3 Zero Sequence Component
  The zero sequence phasors Va0, Vb0 and Vc0 are a set of balanced phasors defined as follows.
    (5)
   
1
4