The β is derived according to equation
for the mho circle and φ is the angle between the
voltage and current.
X
ArgDir
I
AB
ArgNegRes
Z
ANSI09000119-1-en.vsd
f
U
AB
ZRev
R
ANSI09000119 V1 EN
Figure 44:
Operation characteristic for reverse phase A-to-B fault
Phase-to-ground fault
Mho
The measuring of ground faults uses ground-return compensation applied in a
conventional way. The compensation voltage is derived by considering the influence from
the ground-return path.
For a ground fault in phase A, the compensation voltage Vcomp can be derived, as shown
in figure
.
A
loop
pol
Vcomp
V
I
Z
=
-
×
EQUATION1793-ANSI V1 EN
(Equation 17)
where
V
pol
is the polarizing voltage (memorized VA for Phase A-to- ground fault)
Z
loop
is the loop impedance, which in general terms can be expressed as
(
)
1
1
Z +ZN
1
Z
KN
=
× +
EQUATION1799 V1 EN
(Equation 18)
Table continues on next page
1MRK 506 335-UUS A
Section 6
Impedance protection
115
Technical manual
Содержание REL650 series
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