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-US
Figure 104: Simplified offset mho characteristic and voltage vector for phase A-to-ground
fault
Operation occurs if 90≤β≤270.
Offset mho, forward direction
SEMOD154224-327 v3
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 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
105. 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
1MRK 502 066-UUS B Section 7
Impedance protection
229
Technical manual
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