where:
V
2
and IN are the magnitude of the negative sequence voltage and zero-
sequence current (3I
0
)
V2MinOp
is the setting parameter for minimum operating negative
sequence voltage
maxIph is the maximum phase current
The angle difference is phase shifted by 180 degrees if the fault is in reverse direction.
The condition 2 looks at the angle relationship between the negative sequence voltage V
2
and the
positive sequence voltage V
1
. Since this is a phase-to-phase voltage relationship, there is no need
for shifting phases if the fault is in reverse direction. A phase shift is introduced so that the fault
sectors will have the same angle boarders as for condition 1. If the calculated angle between V
2
and V
1
lies within one sector, the corresponding phase for that sector will be activated. The
condition 2 is released if both the following conditions are fulfilled:
|V
2
|>
V2MinOp
|V
1
|>
V1MinOp
where:
|V
1
| and |V
2
| are the magnitude of the positive and negative sequence voltages.
V1MinOP
and
V2MinOP
are the setting parameters for positive sequence and negative sequence
minimum operating voltages.
20°
140°
260°
AG sector
CG sector
BG sector
V1A
(Ref)
en06000413_ansi.vsd
ANSI06000413 V1 EN-US
Figure 117: Condition 2: V
2
and V
1
angle relationship
If both conditions are true and there is sector match, the fault is deemed as single phase-to-
ground. If the sectors, however, do not match the fault is determined to be the complement of the
second condition, that is, a phase-to-phase-to- ground fault.
1MRK 502 066-UUS B Section 7
Impedance protection
249
Technical manual
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