4.8 Symmetric components
4 Measurement functions
Technical description
136
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VM59.EN001
4.8.
Symmetric components
In a three phase system, the current phasors may be divided in
symmetric components according C. L. Fortescue (1918). The
symmetric components are:
Positive sequence 1
Negative sequence 2
Zero sequence 0
Symmetric components are calculated according the following
equations:
W
V
U
a
a
a
a
S
S
S
2
2
2
1
0
1
1
1
1
1
3
1
, where
S
0
= zero sequence component
S
1
= positive sequence component
S
2
= negative sequence component
2
3
2
1
120
1
j
a
, a phasor rotating constant
U
= phasor of phase L1 (phase current)
V
= phasor of phase L2
W
= phasor of phase L3
