Manta MTS-3000 Series, Operation And Reference Manual, Page: 141 / 156

POWERSCOPE PROGRAM
MTS-3000 SERIES OPERATION AND REFERENCE MANUAL B-7
CU M004 01A .
0$17$ # 7(67 # 6<67(06
B.3.3 Interpretation of Symmetrical Components Displays
The dynamic display of symmetrical components allows for very easy demonstration of the basic concepts
of symmetrical components.
1. A normal balanced 3
Φ
system will have no negative sequence or zero sequence components. Also,
symmetrical 3
Φ
faults will have no negative sequence or zero sequence components.
2. Any unsymmetrical faults involving ground (
Φ
-G, 2
Φ
-G) will produce zero sequence components
(current and voltage). The residual current is three times the zero sequence current (Ia
0
), and can be
identified easily.
Similarly, the residual voltage is three times the zero sequence voltage (Va
0
).
3. Phase-phase faults produce only positive and negative sequence components (assuming 0 prefault
currents). As the fault approaches the source, the negative sequence voltage components increase.
For a solid fault at the source (Vf=0), the negative and positive sequence voltages are equal. This
easily can be seen by varying the
Φ
-
Φ
fault voltage from nominal to 0, and by watching the
unbalance change from 0 to 100%.
Characteristics of standard faults are summarized in the table below:
These characteristics easily can be verified with Powerscope. Here are some other interesting things to try:
Phase Unbalance Select
Φ
-N mode and start with a balanced 3
Φ
system. Rotate the phase of one output
and note that this causes the gradual appearance of negative and zero sequence
components.
Condition Voltage
Components
Voltage
Unbalance
Current
Components
Current
Unbalance
Normal prefault, balanced 3
Φ
current
+ve sequence
only
0% +ve sequence
only
0%
Solid A-G fault
(VA=0), no prefault currents
Va
1
= 2Va
2
Va
2
= Va
0
50% Ia
1
=Ia
2
=Ia
0
100%
Solid
Φ
-
Φ
fault (VBC=0), no
prefault currents
No zero sequence,
Va
1
= Va
2
100% No zero sequence,
Ia
1
=Ia
2
100%
3
Φ
fault +ve sequence only 0% +ve sequence only 0%
Solid 2
Φ
-G fault, (VA=VB=0) Va
1
=Va
2
=Va
0
100% Ia
2
= Ia
0
Ia1 = 2Ia
2
50%