ZPEIA •
ZPE•AI-V=V
A
comp1
ß
IAB jX
IAB R
vPeReZ•I- A
VA
)
A= ZRevPE•(-I-A2comp VV
en 06000465_ansi.vsd
•
•
ANSI06000465 V1 EN
Figure 123: Simplified offset mho characteristic and voltage vector for phase A-to-
ground fault
Operation occurs if 90≤β≤270.
Offset mho, forward direction
In the same way as for phase-to-phase fault, selection of forward direction of offset
mho will introduce an extra criterion for operation. Beside the basic criteria for offset
mho according to equation
41 and 90≤β≤270, also the criteria that the angle φ between
the voltage and the current must lie between the blinders in second and fourth
quadrant. See figure 124. Operation occurs if 90≤β≤270 and ArgDir≤φ≤ArgNegRes.
where
ArgDir
is the setting parameter for directional line in fourth quadrant in the directional element,
ZDMRDIR (21D).
ArgNegRes
is the setting parameter for directional line in second quadrant in the directional element,
ZDMRDIR (21D).
β is calculated according to equation 41
Section 6 1MRK505222-UUS C
Impedance protection
252
Technical reference manual
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