20°
140°
260°
AG sector
CG sector
BG sector
V1A
(Ref)
en06000413_ansi.vsd
ANSI06000413 V1 EN
Figure 152: 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.
Condition 1 and Condition 2 ⇒ Fault type
CG CG CG
BG AG BCG
The sequence phase selector is blocked when ground is not involved or if a three-phase
fault is detected.
Three-phase fault detection
Unless it has been categorized as a single or two-phase fault, the function classifies it
as a three-phase fault if the following conditions are fulfilled:
|V
1
|V1Level
and
|I
1
|>I1LowLevel
or
|I
1
|>IMaxLoad
1MRK505222-UUS C Section 6
Impedance protection
297
Technical reference manual
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